JPH02159472A - Hydraulic power transmission device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention A.9 Objective of the Invention (Field of Industrial Application) The present invention provides a hydraulic pump driven by an engine or the like;
The hydraulic power transmission device includes a hydraulic motor that is driven by receiving hydraulic pressure from the hydraulic pump and outputs the driving force to an output shaft. The present invention relates to a power transmission device including an engine brake control valve that is disposed in a transmission oil passage and controls the operation of an engine brake.

(Prior Art) A hydraulic power transmission device configured as described above is disclosed in, for example, Japanese Patent Laid-Open No. 127582/1982. In this example, when driving at low speed, when the accelerator pedal is released and decelerated, the speed ratio (reduction ratio) is large and excessive engine braking force is applied. When the accelerator pedal is pressed again from a decelerating state, the vehicle will accelerate again,
In view of the problem of shocks occurring due to large changes in the direction of acceleration, a bypass oil passage is provided in the hydraulic closed circuit connecting the hydraulic pump and the hydraulic motor from the outlet to the inlet of the hydraulic motor. This bypass oil passage is equipped with a check valve that allows hydraulic oil to flow through this bypass oil passage only when the engine is braking. ).

When the vehicle speed is less than a predetermined vehicle speed, the flow through the bypass oil path is allowed, and when the vehicle speed exceeds a predetermined speed, the flow through the bypass oil path is blocked. It is closed when the vehicle speed is below, and opened when the vehicle speed is above a predetermined speed. This on-off valve is called the engine brake control valve (or engine brake control valve).

The reason why a bypass oil passage having a check valve and an engine brake control valve is provided in this way is as follows.

In order to perform clutch control by controlling the degree of transmission of driving force in the above-mentioned hydraulic power transmission device, a clutch valve is disposed in the bypass oil passage that communicates the discharge side and suction side of the hydraulic pump, and this clutch Clutch control may be performed by controlling the opening of the valve (for example, Japanese Patent Application Laid-Open No. 56-9
Clutch device disclosed in Japanese Patent No. 5722). The operation control of the clutch valve in this case is performed by balancing the control force in the clutch valve closing direction corresponding to the engine rotation and the control force in the clutch valve opening direction corresponding to the engine throttle opening.

In such latch control, in the driving range, even if the accelerator pedal is not depressed and the throttle is fully closed, a creep state is created in which a certain amount of driving force (creep force) is transmitted to the wheels by slightly closing the clutch valve. There is. However, when the vehicle is traveling downhill in a creep state and the vehicle is driven from the wheels, power corresponding to the creep force is transmitted from the hydraulic motor to the hydraulic pump, and the engine rotation is increased accordingly.

When the engine rotation increases, the control force for closing the clutch valve increases, the clutch valve is operated in the closing direction, and the power transmitted from the hydraulic motor to the hydraulic pump increases accordingly. Therefore, there is a problem in that the clutch valve is operated in the closing direction more and more, and a large engine braking force is applied.

Therefore, as described above, a bypass oil passage having a check valve and an engine brake control valve is provided to prevent such problems from occurring.

(Problem to be Solved by the Invention) In the power transmission device having the above configuration, for example, when the vehicle speed is gradually increased while driving on a drop-off road without pressing the accelerator pedal, the vehicle speed may not reach a predetermined vehicle speed. Until the oil pressure is reached, the discharge oil of the hydraulic motor driven from the wheel side is returned to the suction side of the hydraulic motor via the bypass oil passage.
Coasts without engine braking. However,
When the vehicle speed exceeds a predetermined vehicle speed, the engine brake control valve operates and closes the bypass oil passage, so the oil discharged from the hydraulic motor drives the hydraulic pump.
Since this hydraulic pump drives the engine, an engine braking effect occurs. In this case, there is a problem in that, although the vehicle was coasting up until then, when the vehicle speed increases to a certain extent, engine braking is suddenly applied, causing a sudden deceleration of the vehicle body and causing a shock.

The present invention has been developed in view of these problems, and is designed to enable smooth transition when the engine brake control valve is actuated to transition from coasting as described above to engine braking driving. The purpose of the present invention is to provide a power transmission device that achieves the following.

9. Configuration of the Invention (Means for Solving the Problems) As a means for achieving the above object, the power transmission device of the present invention includes a first oil passage that communicates a discharge port of a hydraulic pump and a suction port of a hydraulic motor. , a second oil passage that communicates the suction port of the hydraulic pump and the discharge port of the hydraulic motor, a communication oil passage that communicates the first oil passage and the second oil passage, and a second oil passage that is disposed within the communication oil passage. It is equipped with a check valve that only allows the flow of hydraulic oil from the oil passage to the first oil passage, and an engine brake control valve that is disposed in the connecting oil passage and opens and closes the connecting oil passage. The control valve opens the connecting oil passage when the vehicle speed is below a predetermined vehicle speed, and closes the connecting oil passage when the vehicle speed exceeds the predetermined vehicle speed. It has a damper function that gradually closes the opening degree when closing the communication oil passage.

(Function) When a vehicle equipped with the above power transmission device travels on a drop-off road, etc. without the accelerator pedal being depressed, or when the vehicle speed is less than a predetermined vehicle speed (in the case of low speed), the hydraulic motors driven by the wheels are activated. Since the discharged oil is flowed to the suction side of the hydraulic motor via the connecting oil passage (bypass oil passage), the vehicle coasts without engine braking. When the vehicle speed exceeds a predetermined vehicle speed, the engine brake control valve is activated and the connecting oil passage is closed, so that from then on, engine brake action is applied. In this case, the communication passage is gradually closed by the damper function of the engine control valve, so that the engine braking action also gradually increases. Therefore, the transition from the coasting state to the engine braking state is performed smoothly and without shock.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 is a hydraulic circuit diagram of a continuously variable transmission equipped with a speed change control device according to the present invention. It has a variable displacement swash plate axial plunger type hydraulic pump P and a variable displacement swash plate axial plunger type hydraulic motor M that drives wheels (not shown) via a forward/reverse switching device 20. The hydraulic pump P and the hydraulic motor M are connected to a first circuit oil passage La that communicates the discharge port of the pump P and the suction port of the motor M, and the suction port of the pump P and the motor M.
The two oil passages constitute a hydraulic closed circuit and are connected to the second circuit oil passage Lb which communicates the discharge ports of the two oil passages. These 2
Of the main oil passages La and Lb, the first circuit oil passage La is used when the pump P is driven by the engine E and the motor M is rotationally driven by the oil pressure from the pump P to drive the wheels, that is, the engine E When the wheels are driven via the continuously variable transmission T, the pressure becomes high (at this time, the second circuit oil path Lb is at low pressure), while the second circuit oil path Lb becomes high pressure when the vehicle decelerates, etc. The pressure becomes high when the engine brake is applied in response to driving force from the wheels (at this time, the pressure in the first circuit oil path a is low).

A direct coupling clutch valve DC that can connect and disconnect the oil passage La is disposed within the first circuit oil passage La.

A discharge port of a charge pump (replenishment pump) 1O driven by the engine E via a pair of gear sets 9a+9b is
It is connected to the regulator valve 12 via a pump discharge oil passage Lj, and a first control oil passage L1 branches off from this discharge oil passage Lj. The regulator valve 12 operates according to the oil pressure in the discharge oil passage Lj, sets the oil pressure in the discharge oil passage Lj and the first control oil passage L1 to a predetermined control line pressure Pt, and maintains this line pressure PL. The hydraulic oil is supplied from the first control oil path to control valves and the like, which will be described later.

The amount of oil supplied from the first control oil path L1 to the control valves etc. is small compared to the discharge amount of the charge pump 10, and therefore, the remaining oil is supplied to the first control valve by the operation of the regulator valve 12.
It is sent to charge oil path Lk. In addition, when there is still an excess amount of oil even after sending it to the first charge oil path Lk, it is returned to the sump 17 from the drain oil path Lm. In this way the first
The oil sent to the charge oil path Lk passes through the centrifugal oil filter 4 and is purified, and then passes through the second charge oil path Ln to the third circuit oil path La, which has a pair of check valves 3, 3. By the action of the check valves 3, 3, the oil is supplied to the lower pressure side of the first and second circuit oil passages La, Lb.

Note that a first lubricating oil passage Lp that connects to the internal space of the motor cylinder 70 that constitutes the pump case branches from the second charge oil passage Ln, and a portion of the oil supplied to the second charging oil passage Ln is It passes through the check valve 6a disposed in the first lubricating oil passage Lp and is supplied into the internal space via this oil passage Lp. The oil supplied to this internal space lubricates the pump parts and is sent to the outside from the second lubricating oil path LQ for lubrication. Note that when the rotation of the motor cylinder 70 is extremely small, that is, when the engine is stopped, the check valve 6b opens and the hydraulic oil in this internal space is directly discharged to the sump 17.

A governor valve 8 is attached coaxially with the charge pump 10. Hydraulic oil at a predetermined pressure is supplied to this governor valve 8 from a control valve (not shown), and the governor valve 8 converts the pressure of this hydraulic oil into governor oil pressure corresponding to the rotational speed of the engine E. Note that the input and output oil passages connected to the governor valve 8 will be described later.

A fourth circuit oil path Ld having a shuttle valve 110 is connected to the closed circuit. A fifth circuit oil passage La having a low pressure relief valve 7 and connected to the oil sump 17 is connected to the shuttle valve 110. The shuttle valve 110 connects the first and second circuit oil passages a + t.
, b, and connects the lower pressure side of the first and second circuit oil passages La, Lb to the fifth circuit oil passage La. As a result, the relief oil pressure in the oil passage on the low pressure side is regulated by the low pressure relief valve 7.

Between the first and second circuit oil passages a r L b, there is also a sixth circuit oil passage Lf that short-circuits both passages. A main clutch valve CL consisting of a variable throttle valve is provided to control the main clutch valve CL.

Sarani, engine brake control valve 12
0 and the check valve 139 in series, the seventh circuit oil passage g is the first and second circuit oil passage a + L.
This seventh circuit oil passage g portion is shown in detail in FIG. 2.

The engine brake control valve 120 includes a bousing 121, a spool 122 fitted into an insertion hole of the bousing 121 so as to be movable left and right, a spring 123 that biases the spool 122 leftward, and a right end of the insertion hole. and a plug 125 that covers the area. The check valve 139 is made up of a ball 139a and a spring 139b, and is a valve that blocks the flow of hydraulic oil from the first circuit oil path La toward the second circuit oil path Lb, but allows the flow in the opposite direction.

A tapered groove 122a is formed in the spool 122, and when the spool 122 is moved to the left by the bias of a spring 123 (the state shown in the figure), the seventh circuit oil passage g is opened, and the spool 122 7th according to the movement to the right
Gradually close the circuit oil passage g. For this reason, spool 1
22 is moved to the left, when the wheels are driven by the engine E via the continuously variable transmission T, that is, when the first circuit oil passage La is at high pressure, the seventh circuit oil passage La is moved by the action of the check valve 139. Although hydraulic oil does not flow through Lg, when the hydraulic motor M is driven in response to the driving force from the wheels, that is, when the second circuit oil path Lb is at high pressure, there is no flow of hydraulic oil through the second circuit oil path Lb. Hydraulic oil flows into the first circuit oil passage La through the seven circuit oil passage Lg.

When there is no flow through the seventh circuit oil path Lg, when the hydraulic motor M is driven in response to the driving force from the wheels, the hydraulic pump P is driven thereby, and engine braking force is applied. However, in the above case, the hydraulic oil discharged from the hydraulic motor M to the second circuit oil path Lb is
It is sucked in from the suction port of the hydraulic motor M via the circuit oil path Lg and the first circuit oil path La. For this reason, the hydraulic pump P
is not driven, and engine braking is not applied.

Here, the engine brake control valve 12
Oil pressure from the 60th control oil passage Leo acts on the left end of 0. As will be described later, line pressure PL is supplied to the 60th control oil passage L60 when the vehicle speed becomes equal to or higher than a predetermined vehicle speed. be moved. When the spool 122 is moved to the right, the seventh circuit oil passage Lg is closed by this spool 122, and the second circuit oil passage Lb is connected to the first circuit oil passage La via this seventh circuit oil passage Lg.
The flow of hydraulic oil to the engine is blocked and engine braking is applied.

The right end 122b of the spool 122 is fitted into the recess 125a of the plug 125, and the right end 122b is fitted into the recess 125a of the plug 125.
b is provided with a passage 122c and a one-way valve 12θ that communicate the space 125b in the recess 125a with a drain. The one-way valve 126 is a valve that allows the flow of hydraulic oil from the drain side to the space 125b, but blocks the reverse flow. Therefore, as described above, the 60th control oil path. . When the spool 122 is moved to the right by the line pressure Pt from the spool 122, the space 125b is closed by the right end 122b of the spool 122 and the passage 122C is closed by the one-way valve 126, so the oil in the space 125b is , it only flows out to the drain side through the fitting gap between the recess 125a of the plug 125 and the right end 122b of the spool 122. Since this fitting gap is extremely narrow, the spool 122 is moved slowly to the right. Thereby, the seventh circuit oil passage Lg is slowly closed by the spool 122 by the Taper groove 122a.

Therefore, from a state in which the engine brake is not operating (a state in which the spool 122 is moved to the left), line pressure Pt is supplied to the 60th control oil passage Lieo, and the line pressure Pt is supplied to the 7th circuit oil passage Lg.
When the seventh circuit oil passage Lg is closed and the engine brake is operated, the seventh circuit oil passage Lg is closed slowly, and the engine braking force increases slowly.

Returning to FIG. 1, first and first circuit oil passages Lai and Lbl branch from the first and first circuit oil passages La+Lb, respectively. These two branch oil passages 1. al.

Lbl is connected to the high pressure oil path Lh via the check valve 5 a r 5 b, and the higher oil pressure PH of the first and second circuit oil paths L a * L b is connected to this high pressure oil path Lh. Supplied.

An output shaft 28 is arranged parallel to the rotating shaft 2 of the hydraulic motor M, and a forward/reverse switching device 20 is provided between both shafts 2 and 28. This device 20 includes first and second drive gears 21 and 22 disposed on a rotating shaft 2 with a spacing in the axial direction, and rotatably supported by an output shaft 28 and a first drive gear 2
1, a second wave gear 25 that meshes with the second drive gear 22 via an intermediate gear 24, and is rotatably supported on the output shaft 28; A clutch hub 26 is fixed to the output shaft 28 between the gears 23 and 25, and a clutch gear 23a or 25a is slidable in the axial direction and is formed on the side surfaces of the clutch hub 26 and the driven gears 23 and 25, respectively. This sleeve 27 is moved from side to side by a shift fork 29. The specific structure of this forward/reverse switching device 20 is shown in FIG. In this forward/reverse switching device 20, when the sleeve 27 is slid leftward in the figure by the shift fork 29 and the clutch gear 23a of the first driven gear 23 and the clutch hub 26 are connected as shown in the figure, the output The shaft 28 is rotated in the opposite direction to the rotating shaft 2, and the wheels are rotated in the forward direction as the continuously variable transmission T is driven. On the other hand, when the sleeve 27 is slid to the right by the shift fork 29 and the clutch gear 25a of the second driven gear 25 and the clutch hub 26 are connected, the output shaft 28 is rotated in the same direction as the rotating shaft 2, The wheels are rotated in the reverse direction.

Next, the concrete structure of the continuously variable transmission T will be briefly explained using FIG. 3.

This continuously variable transmission T has first to fourth cases 15a to 15d.
A hydraulic pump P and a hydraulic motor M are arranged intermittently in a space surrounded by. An input shaft 1 of the hydraulic pump P is coupled to a crankshaft Es of the engine E via a flywheel 1a. This flywheel 1
A centrifugal filter 4 is disposed within the inner circumferential recess of a.

Further, a drive gear 9a is connected to the input shaft 1 by a spline, and a driven gear 9b meshes with the drive gear 9a. The driven gear 9b is coaxially connected to the drive shaft 11 of the charge pump 10, and the rotation of the engine E is transmitted to the drive shaft 11 of the charge pump 10 via the pair of gears 9a+9b, thereby driving the charge pump 10. . This drive shaft 11 passes through the charge pump 10 and protrudes to the side opposite to the gear 8b, and is also connected to the governor valve 8. Therefore, the rotation of the engine E is also transmitted to this governor valve 8, and the governor valve 8 causes the engine E to rotate.
A governor oil pressure P0 corresponding to the rotation of is created.

The hydraulic pump P includes a pump cylinder 60 spline-coupled to the input shaft 1, and a plurality of pump plungers 62 slidably engaged with a plurality of cylinder holes 61 formed in the pump cylinder 60 at equal intervals on the circumference. It is rotationally driven by the power of the engine E transmitted via the input shaft l.

The hydraulic motor M includes a motor cylinder 70 provided surrounding the pump cylinder 60, and a plurality of motor plungers 72 that slide into a plurality of cylinder holes 71 formed in the motor cylinder 70 at equal intervals on the circumference. It is designed to be able to rotate relative to the pump cylinder 60 coaxially.

The motor cylinder 70 is composed of first to fourth parts 70a to 70d that are aligned in the axial direction and are integrally coupled.

The first portion 70a has a bearing 7 at its left end outer periphery.
The pump swash plate ring 63 is rotatably supported by the case 15b via the pump 9a, and the right inner surface is inclined with respect to the input shaft 1 to form a pump swash plate member. is provided. second part 70
The plurality of cylinder holes 71 are formed in b, and the third portion 70c has a distribution plate 80 in which oil passages to each cylinder hole 61, 71 are formed. A gear member having the first and second drive gears 21 and 22 is press-fitted into the fourth portion 70d, and is connected to the case 1 through a bearing 79b.
It is rotatably supported by 5c.

An annular pump shoe 64 is rotatably and slidably attached on the pump swash plate ring 63, and the pump shoe 64 and the pump plunger 62 are connected to each other via a connecting rod 65 so as to be able to swing freely to some extent. pump shoe 6
4 and the pump cylinder 80 have bevel gears 68 that mesh with each other.
a, 88b are formed. Therefore, when the pump cylinder 60 is rotationally driven from the input shaft 1, the pump shoe 64
The pump plunger 62 is reciprocated in accordance with the inclination of the pump swash plate ring 63 to suck oil from the suction port and discharge oil to the discharge port.

Also, a swash plate member 73 facing each motor plunger 72
However, the second case 15
It is swingably supported by b. A motor swash plate ring 73b is disposed on the surface of the swash plate member facing the motor plunger 72, and a motor shoe 74 is mounted on the motor swash plate ring 73b by a sliding fluid. The motor shoe 74 is swingably connected to the end of each motor plunger 72. This swash plate member 73 is connected to the piston rod 32 of the first shift servo unit 30 via a link member 39 at a position away from the trunnion shaft 73a.
When the piston rod 32 is moved in the axial direction,
The swash plate member 73 is configured to swing around a trunnion shaft 73-a.

The fourth portion 70d of the motor cylinder 70 is formed hollow, and a fixed shaft 91 fixed to the pressure distribution board 18 is inserted into the center thereof. A distribution ring 92 is fluid-tightly fitted to the left end of the fixed shaft 91, and the left end surface of the distribution ring 92 in the axial direction is eccentric so that it can come into sliding contact with the distribution plate 80.

This distribution ring 92 divides the hollow portion formed within the fourth portion 70d into an inner oil chamber and an outer oil chamber, with the inner oil chamber forming the first circuit oil passage La and the outer oil chamber forming the first circuit oil passage La. A second circuit oil path Lb is configured. Note that the pressure distribution panel 18 has a shuttle valve 110, a low pressure relief valve 7, etc.
Attached to the right side of the third case 15C,
It is covered by a fourth case 15d.

A pump discharge port and a pump suction port are bored in the distribution board 80, and the cylinder hole 61 of the pump plunger 62 in the discharge stroke and the inner oil chamber are connected through the discharge port and the discharge path connected thereto. The first circuit oil passage La is in communication with the second circuit oil passage Lb, which is made up of the cylinder hole 61 of the pump plunger 62 in the suction stroke and the outer oil chamber via the pump suction port and the suction passage connected thereto. communicated. Furthermore, a communication path communicating with the cylinder hole (cylinder chamber) 71 of each motor plunger 72 is formed in the distribution board 80, and the opening of this communication path is
Due to the action of the distribution ring 92, it is communicated with the first circuit oil passage La or the second circuit oil passage Lb according to the rotation of the motor cylinder 70. Therefore, the cylinder hole 71 of the motor plunger 72 in the expansion stroke and the first circuit oil passage La are different from the cylinder hole 71 of the motor plunger 72 in the contraction stroke and the second circuit oil passage La.
The circuit oil passages Lb are communicated with each other via communication passages.

In this way, a hydraulic closed circuit is formed between the hydraulic pump P and the hydraulic motor M via the distribution panel 80 and the distribution ring 92. Therefore, when the pump cylinder 60 is driven from the input shaft 1, the high-pressure hydraulic oil generated by the discharge stroke of the pump plunger 62 is transferred from the pump discharge port to the pump discharge passage, the first circuit oil passage La (inner oil chamber), and the like. It flows into the cylinder hole 71 of the motor plunger 72 which is in the expansion stroke through the first communication path which is in communication with the
A thrust is applied to the motor plunger 72. On the other hand, the hydraulic oil discharged by the motor plunger 72 in the contraction stroke is in the suction stroke via the second communication path communicating with the second circuit oil path Lb (outer oil chamber), the pump suction path, and the pump suction port. It flows into the cylinder hole 61 of the pump plunger 62.

Due to this circulation of hydraulic oil, the reaction torque that the pump plunger 62 in the discharge stroke applies to the motor cylinder 70 via the pump swash plate ring 63, and the reaction torque that the motor plunger 72 in the expansion stroke receives from the motor swash plate member 73. The motor cylinder 70 is rotationally driven by the sum of .

The gear ratio of the motor cylinder 70 to the pump cylinder 60 is given by the following equation.

Rotation speed of pump cylinder 60 Gear ratio = Rotation speed of motor cylinder 70 Capacity of hydraulic motor M 1 + Capacity of hydraulic pump P As can be seen from the above equation, the swash plate member 73 is oscillated by the speed change servo unit 30, and the hydraulic By changing the capacity of the motor M from O to a certain value, the gear ratio can be changed from 1 (minimum value) to a certain required value (maximum value).

On the other hand, as described above, a gear member having first and second drive gears is press-fitted and fixed into the fourth portion 70d of the motor cylinder 70. For this reason, the motor cylinder 70
The rotational driving force is transmitted to the output shaft 2 via the forward/reverse switching device 20.
8.

This output shaft 28 is connected to a final gear set 28 a + 2
Is it connected to the differential device 100 via 8b? The rotational driving force of the output shaft 28 is transmitted to the differential device 100. And the differential
The device 100 drives the left and right drive shafts 105, 10.
The rotational driving force divided into 6 is applied to the left and right wheels (not shown).
and the vehicle is driven.

A short-circuit path between the first circuit oil passage La and the second circuit oil passage Lb is formed in the fixed shaft 91 inserted into the hollow portion of the fourth portion 70d, and this short-circuit path can be changed from fully closed to fully opened. A main clutch valve CL that can control up to 100 degrees, and a direct clutch valve DC that can control the first circuit oil passage La on and off are provided.

First, the main clutch valve CL will be explained. A first circuit oil passage La and a second circuit oil passage Lb are provided on the peripheral wall of the fixed shaft 91.
A cylindrical main clutch valve body 95 is inserted into the hollow portion of the fixed shaft 91. The valve body 95 is rotatable relative to the fixed shaft 91, and has a short-circuit hole that can be aligned with the short-circuit port. By rotating an arm 95a formed at the right end of the valve body 95, the valve body 95 can be rotated to adjust the amount of alignment (overlapping) between the short circuit port and the short circuit hole. The size of this matching part becomes the opening degree of the short-circuit passage between the first circuit oil passage La and the second circuit oil passage Lb, and therefore, by controlling the rotation of the valve body 95, the opening degree of the short-circuit passage is changed from fully open to fully open. Can be controlled when fully closed. If the short circuit passage is fully open, the first
The hydraulic oil discharged into the circuit oil passage La directly flows into the second circuit oil passage Lb from the short-circuit port and the short-circuit hole, and also flows into the pump suction port, so the hydraulic motor M becomes inactive and the clutch is in the OFF state. Become. Naturally, on the contrary, if the opening degree of the short-circuit passage is fully closed, a clutch ON state in which the hydraulic motor M operates is realized.

A direct coupling clutch valve DC is disposed within the hollow portion of this main clutch valve body 95. This direct-coupled Clara valve DC includes a piston shaft 85 inserted into the valve body 95 so as to be movable in the axial direction, a shoe 86 attached to the tip of the piston shaft 85, and a shoe 86 inserted into the piston shaft 85. The pilot spool 84 is composed of a pilot spool 84.
By moving in the axial direction, the piston shaft 85 can be moved in the axial direction to follow this movement. Therefore, the pilot spool 84 is moved to the left, the piston shaft 85 is moved to the left, and the shoe 86 at the tip of the pilot spool 84 is moved to the left to block the discharge path of the pump that opens to the end face of the distribution board 80, thereby blocking the first circuit oil path La. It is now possible to do so. In this state where the pump discharge passage is closed, the pump plunger 62 is hydraulically locked, and the hydraulic pump P and the hydraulic motor M are directly connected.

Next, a control device for the continuously variable transmission T having the above configuration will be explained using the circuit diagrams shown in FIGS. 4 and 5.

The control device includes a clutch servo unit 130 that controls the main clutch CL, a forward/reverse servo unit 140 that controls the operation of the forward/reverse switching device 20, and a swash plate member 73 that swings to control the gear ratio. There are first and second shift servo units 30, 50, which are operated appropriately by the illustrated hydraulic valves to perform various controls.

First, the configuration and operation of each device will be explained.

The clutch servo unit 130 has a fixed cylinder 131
The piston member 132 is fitted into the upper cylinder 31 so as to be slidable in the axial direction, and a spring 133 biases the piston member 132 to the right in the figure. The cylinder 13 is divided into two parts by the piston of the piston member 132.
The left and right cylinder chambers 134 and 135 formed in 1 include
Two sixths connected to the clutch control valve 220
and seventh control oil passages Le and L7, respectively. Therefore, the piston member 132 is moved left and right in the figure by the hydraulic pressure of the hydraulic oil that is selectively supplied to and discharged from the left and right cylinder chambers 134 and 135 by the clutch control valve 220.

The left end of the piston member 132 is connected to the cam member 97 via a link 98a. The cam member 97 has its cam surface 97
a is the right spool 2 of the clutch control valve 220
23 end face, and is fixed to the shaft 98a at one end. A link arm 98b is also fixed to the shaft 98a. The tip of this link arm 98b is a link 9θ
It is connected to an arm 95a integrally formed with the main clutch valve body 95 described above through b. Therefore, when the piston member 132 is moved left and right, the cam member 97 and the link arm 98b are rotated together around the shaft 98a, and the main clutch valve body 95 is accordingly moved to the OFF position shown in the figure. (open position) to ON position (closed position)
It is rotated between. Note that at this time, the cam surface 97a
is adapted to push the right spool 223 to the right in response to the rotation of the cam member 97.

The clutch control valve 220 includes a left spool 221 and a right spool 223 that are movable in the axial direction, and a spring 222 disposed between the spools 221 and 223.
The spring 224 biases the left spool 221 to the right. Furthermore, the space in which this spring 224 is arranged (
In the left side space of the left spool 221, there is a governor valve 8.
A 17th control oil passage LIT that communicates with the 16th control oil passage Llf+ that communicates with the discharge port of the engine E is communicated with the 16th control oil passage Llf+ that communicates with the discharge port of the
A governor pressure P0 corresponding to the rotation speed is supplied. Also,
The space where the spring 222 is arranged (left and right spool 22
In the space between 1 and 223), there is a throttle valve 24
0 to the 22nd control oil path L22, the 23rd control oil path L23,
Clutch off valve 235 and 24th control oil passage L24
Throttle pressure PT corresponding to throttle opening
H is supplied.

Therefore, the left spool 221 is connected to the governor pressure P0 and the spring 2
It is moved to the right or to the left in response to a rightward pushing force by 24 and a leftward pushing force by throttle pressure PTH and spring 222. In response to this movement, the line pressure Pt sent from the first control oil passage L1 to the fifth control oil passage L5 is supplied to one of the sixth and seventh control oil passages Le, L7, and the hydraulic oil is supplied from the other. is discharged into the drain. This results in
The piston member 132 of the clutch servo unit 130 is operated, and the operation of the main clutch CL is controlled.

However, at this time, the right spool 223 is pushed by the cam member 97 as the piston member 132 moves, and the spring 222
The pushing force of the main clutch can be changed, so that the main clutch can be opened and closed according to desired characteristics.

In addition, the right spool 223 has a groove 223a at 2tlf,
223b is formed, and both grooves 223a, 223b communicate with the outside when the main clutch valve body 95 is in the OFF position (when the piston member 132 of the clutch servo unit 130 is in the rightward movement position). From this state, when the piston member 132 is moved to the left and the clutch valve body 95 is rotated in the ON direction, the right spool 223 is pushed to the left by the cam member 97, and the clutch valve body 95 is moved to a certain position ( At this position, creep force can be transmitted, and this position is referred to as the creep position).
a, 223b are closed. This groove 223b is connected to the 23rd control oil passage L21 via the 25th control oil passage L25, and when the clutch valve body 95 is between the OFF position and the creep position, the groove 223b is connected to the space where the spring 222 is disposed. The active throttle pressure PTII is drained.

Therefore, at this time, the line pressure PL is supplied from the seventh control oil passage L7 to the right cylinder chamber 135 of the clutch servo cylinder 130, and the piston member 132 is moved to the right.
Clutch valve body 95 is moved to the creep position. Thereby, even when the engine is idling and the governor pressure P0 is low, the clutch valve body 95 is positioned at the creep position.

Therefore, even when the accelerator pedal is not depressed and the engine is idling, the clutch valve body 96 is in the creep position, and creep force is transmitted to the wheels. However, if the hydraulic motor M is driven by the driving force from the wheels when the vehicle approaches the exit road in this state, the driving force corresponding to the creep force will be transmitted to the engine and the engine rotation will increase. When the engine speed is increased, the governor pressure P.

As a result, the clutch valve 95 is rotated toward the ON position, causing the problem that the creep force further increases. However, in this example, when the hydraulic motor M is driven, as explained in FIG. This prevents such problems from occurring.

In addition, when discharging the hydraulic oil in the left cylinder chamber 134 from the sixth control oil passage L6 in order to operate the clutch CL from OFF to ON, the clutch control valve 22
0 to 8th, 9th and 10th control oil passages Ls r Le
+L+o. This tenth control oil passage LIO is connected to the drain via the first orifice 274, and also connects to the orifice change valve 270 and the second control oil passage LIO.
It is connected to a drain via an orifice 272, and these orifices 272, 274 limit the discharge speed of the hydraulic oil and adjust the connection speed (speed from OFF to ON) of the clutch CL.

The connection speed of the clutch CL is required to be faster when the throttle opening of the engine E is small than when it is wide. Therefore, the 25th control oil passage L2. Throttle pressure PTH is introduced from the throttle valve 240 through
When the pressure becomes higher than a predetermined pressure, the orifice change valve 270 is moved to the left by this hydraulic pressure, and this valve 270
is closed. In this way, the throttle opening is small and the orifice change valve 270
When the valve is open, the above-mentioned hydraulic oil is discharged through the two orifices 272 and 274, but when the throttle opening is large and the orifice change valve 270 is closed, one orifice is discharged. 274, and when the throttle opening is large, the connection speed of the main clutch CL becomes slow.

As described above, the discharge speed of hydraulic oil from the left cylinder chamber 134 of the clutch servo unit 130 is changed in accordance with the throttle opening degree, and the connection speed of the clutch CL is adjusted to a desired value.

However, since this adjustment is performed using fixed orifices 272 and 274, the discharge speed is affected by changes in the viscosity of the hydraulic oil. There is a problem in that the connection speed of the clutch CL becomes extremely slow.

In order to solve this problem, in this example, an eleventh control oil passage L11 having a relief valve 260 is branched from the tenth control oil passage Lto. This is done in consideration of the fact that when the discharge of hydraulic oil from the fixed orifices 272 and 274 is slow at low temperatures, the oil pressure in the oil passage upstream from these becomes higher than normal. Therefore, the relief valve 260 is set to open when the oil pressure in the oil passage L□1 becomes higher than the oil pressure generated at the normal operating temperature (for example, 80° C.).

For this reason, the orifice is 272°274° when the hydraulic oil is hot or cold.
When the flow resistance is large and the oil pressure in the oil passage Lll is high, this relief valve 260 is opened, and even if the amount of oil discharged from the fixed orifices 272, 274 is small, it is compensated for by the discharge from the relief valve 260, To smoothly connect a clutch CL. This allows the clutch CL to be connected without delay even when starting at a low temperature, making it possible to start the vehicle smoothly.

The servo unit 140 for forward and backward movement has a fixed cylinder 141
The piston member 142 is fitted into the cylinder 141 so as to be movable in the axial direction (up and down in the figure), and a spring 143 urges the piston member 142 downward. The space within the cylinder 141 covered by the cover 14.6 is divided into two into upper and lower cylinder chambers 144, 145 by a piston of a piston member 142 fitted into this space, and both cylinder chambers 144, 145 have a , the 31st and 33rd control oil passages L 311 L3G communicate with each other, respectively.

Both passages L31 and L33 are connected to the manual valve 210 directly or via the clutch-on valve 230 and the 32nd control oil passage L3□, respectively. Manual valve 210, L2. When in the L position (2.1 position in the figure), the line pressure PL from the control oil passage L2 is supplied to the 31st control oil passage L3□, and the 33rd control oil passage L33 communicates with the drain.
When in the R position, line pressure PL is supplied to the 33rd control oil passage L33, and the 31st control oil passage L3,
is connected to the drain. For this reason, manual valve 2
10, L2. When Lt positidine is selected,
The piston member 142 is moved downward as shown, and the shift fork 29 fixed to the tip of the piston member 142 is located at the forward position.

On the other hand, when the R position is selected, the piston member 142 is moved upward and the shift fork 29 is located in the reverse position. In addition, other children, namely N
And in the P position, both control oil passages L31
and L1i3 are both connected to the drain, but in this case, the biasing force of the spring 143 holds the piston member 142 in the downward movement position, and the shift fork 29 is positioned in the forward movement position.

Furthermore, when the line pressure PL is supplied to the upper cylinder chamber 144 and the piston member 142 is moved downward, this line pressure P
t is introduced into the 15th control oil passage L□5, line pressure Pt is supplied to the lower cylinder chamber 145, and the piston member 142
is being moved upward, this line pressure PL is applied to the 15th control oil passage L through the through hole 142b in the piston member 142.
Introduced at +5.

Next, the shift servo unit 30.50 shown in FIG. 5 will be explained. Both units 30 and 50 are link mechanisms 4
Connected via 0.

The first speed change servo unit 30 includes a fixed cylinder 31, a piston rod 32 fitted into the cylinder 31 so as to be movable up and down in the figure, a valve member 33 fixedly held within the rod 32, and this valve. The spool member 34 is inserted into the member 33 so as to be movable up and down in the figure. The internal space of the cylinder 31 is covered at the upper part of the figure by a cover (not shown), and is divided into two parts by the piston portion 32a of the piston rod 32 to form upper and lower cylinder chambers 35.3E3. Also,
The lower end of the piston rod 32 projects outward from the cylinder 31, and is connected to a swash plate member 73 of the motor M via a link member 39, as shown in FIG.

A high-pressure oil passage Lh is connected to the cylinder 81, and a high-pressure introduction hole 31a that communicates this with the lower cylinder chamber 36
is formed, and hydraulic oil having a hydraulic pressure PR on the high pressure side in the hydraulic closed circuit of the transmission T is introduced into the lower cylinder chamber 3θ. The hydraulic oil having this high pressure P)I is further guided to the groove 33a of the valve member 33 via the communication hole 32b of the piston rod 32, and is also guided into the groove 33a of the valve member 33 from this groove 33a via the communication hole 33b. It is guided into a spool member insertion hole (not shown).

When the spool member 34 inserted into this insertion hole is moved upward relative to the valve member 33 in the figure, it closes the communication hole 33b of the valve member 33 and opens the upper cylinder chamber 35 inside the piston rod 32. When it is discharged to the drain through the through hole 32c and is relatively moved downward,
The communication hole 33b of the valve member 33 is communicated with the upper cylinder chamber 35. For this reason, the spool member 3
4, the high pressure P acting on the lower cylinder chamber 36 increases.
The piston rod 32 is moved to the spool member 3 by the hydraulic pressure of o.
It will be moved up following 4. Also, when the spool member 34 is moved downward, high pressure P is applied to the upper and lower cylinder chambers 35 and 38.
R is added, and the piston rod 32 follows the spool member and is moved downward due to the difference in pressure receiving area in the piston portion 32a (the pressure receiving area on the upper cylinder chamber 35 side is larger).

Note that when the spool member 34 is stationary, the piston rod 32 is also held stationary at a position where the forces applied to the piston portion 32a from the upper and lower cylinder chambers 35, 36 are balanced. That is, when the spool member 34 is moved up and down, the piston rod 32 is moved up and down following this movement. At this time, since the piston rod 32 is connected to the swash plate member 73 of the motor M, the swash plate angle can be controlled by moving the spool member 34, that is, the gear ratio of the transmission T can be controlled.

The upper end of the spool member 34 is connected to the second link via the first link 41.
It is connected to one end of the link 42. The second link 42 is integrally connected to the shaft 43 and is rotatable about the shaft 43. A third link 44 is also integrally connected to the shaft 43, and the third link 44 is connected to a piston member 52 of a second speed change servo unit 50 via a fourth link 45. Therefore, when the piston member 52 is moved up and down in the figure, the spool member 34 of the first gear shifting servo unit 30 is moved up and down via the link mechanism 40 constituted by the links 41 to 45.

The second speed change servo unit 50 is constructed by fitting the piston member 52 into a fixed cylinder 51 so as to be movable in the axial direction (in the vertical direction in the figure). The internal space of the fixed cylinder 51 is covered by the plug member 53 and divided into two by the piston portion of the piston member 52 to form upper and lower cylinder chambers 54 and 55. The upper cylinder chamber 54 includes a 44th control oil passage L44 having an orifice 57a and a 45th control oil passage L44 having a check valve 57b.
A 42nd control oil passage L4° communicates with the control oil passage L45, and a 40th control oil passage L4° communicates with the lower cylinder chamber 55. The 42nd control oil path L4□ is the clutch off valve 23
5 and the 41st control oil passage L41, and the 40th control oil passage L40 is directly connected to the shift control valve 25.
Connects to 0.

Therefore, due to the action of the shift control valve 250, the upper cylinder chamber 54 and the lower cylinder chamber 55 are
The line pressure PL is supplied from the control oil path L15, or the hydraulic oil in the cylinder chamber is discharged. The piston member 52 is moved up and down in accordance with the supply and discharge of the hydraulic oil, and this is transmitted to the first shift servo unit 30 via the link mechanism 40 to perform shift control. in particular,
By moving the piston member 52 of the second shift servo unit 50 upward and moving the piston member 32 of the first shift servo unit 30 downward, the gear ratio is increased (LO
(shift to the W side), and conversely, by moving the piston member 52 downward and moving the piston member 32 upward,
It is possible to reduce the gear ratio (shift to the TOP side).

In this case, the line pressure PL is gradually supplied to the upper cylinder chamber 54 by the action of the orifice 57a, but the hydraulic oil is discharged from the upper cylinder chamber 54 by the check valve 5.
7b is opened and done rapidly. Therefore, when moving the piston member 52 upward to increase the gear ratio (LOW
This is done rapidly when shifting to the side), but when the piston member 52 is moved downward to reduce the gear ratio (
When shifting to the TOP side), this is done slowly. However, the piston member 52 has a first
A groove 52a is formed, and the 43rd control oil passage L43 communicating with the hole formed in the cylinder 51 passes through this groove when the gear ratio is large (when the piston member 52 is moving upward by a predetermined amount or more). It communicates with the upper cylinder chamber 54 through the upper cylinder chamber 54. Therefore, the line pressure Pt is supplied via this 43rd control oil passage L43 until the piston member moves down by a predetermined amount or more and the gear ratio becomes below a certain value, and during this time, a rapid gear change is performed. .

Note that a tapered surface 52d is formed at the lower end of the piston member 52, and the end surface of the spool 151 of the throttle cam mechanism 150 is in contact with this tapered surface 52d.
The throttle cam mechanism 150 is configured to operate in accordance with the gear ratio.

Furthermore, through holes 56a and 56b are formed in the upper part of the cylinder 51 and are connected to the insertion hole of the piston member 52, and the 46th and 47th control oil passages L4 (11L 47) communicate with the two-way holes 56a and 58b, respectively. .

A groove 5 is provided in the upper part of the piston member 52 to connect the through holes 56a and 156b to the drain when the piston member 52 is moved upward by a predetermined amount or more.
2b and 52c are formed. Therefore, when the piston member 52 is moved upward and the gear ratio becomes smaller (approaching the TOP side), the 47th control oil passage L 47 is first communicated with the drain via the groove 52C and the through hole 56b, and then When the piston member 52 is moved upward, the groove 52b and the through hole 58
The 46th control oil passage L4a is communicated with the drain via a.

Below, each valve illustrated in FIGS. 4 and 5 will be briefly described.

The spool 211 of the manual valve 210 is operated in response to operation of the shift lever at the driver's seat, and the operation of the forward/reverse servo unit 140 is controlled as described above.

Note that when the spool 211 is located at the "2" position (L2 position), the 48th control oil passage L4g having governor pressure is communicated with the 46th control oil passage L46, and °'
When the spool 211 is at the 1"' position, the 48th control oil passage L48 is communicated with the 47th control oil passage L4□. Therefore, when the spool 211 is at the 1! 2" or "1" position, the gear ratio is set to a predetermined value. If the value falls below the 48th
The governor pressure in the control oil passage L48 is drained, and as will be described later, the governor pressure acting on the shift control valve 250 becomes zero, preventing the gear ratio from becoming smaller (toward the TOP side).

The clutch-on valve 230 is normally connected to its spool 23.
1 has been moved to the left by the pushing force of the spring 232 as shown in the figure. However, the controller 100
When it is detected that the vehicle speed has become equal to or higher than a predetermined vehicle speed, the normally open type first solenoid valve 280 is operated and closed, and the flow of water from the third control oil path L3 into the 51st control oil path L□ is activated. Line pressure PL is generated, and the spool 232 is moved to the right by this hydraulic pressure. As a result, the 17th
Line pressure Pt from the 34th control oil passage L34 is supplied to the control oil passage L17, and the clutch control valve 22
0's left spool 221 is moved to the right, and the main clutch C
L is kept in the ON state (connected state) regardless of its state. At the same time, the line pressure P is also supplied to the engine brake control valve 120 shown in FIG. 1 from the 60th control oil passage LflO. At this time, the 33rd control oil passage L33 connected to the lower cylinder chamber 144 of the forward/reverse servo unit 140 is in communication with the drain, and the manual valve 210 is set to reverse (R) while driving in this state.
This servo unit 140 is prevented from operating even if the switch is switched to improve safety.

The latch-off valve 235 is the manual valve 21
In cases other than the case where 0 is the N or P position, the spool 236 is moved to the left as shown in the figure by the line pressure Pi from the 15th control oil passage LI5 acting on the right end of the spool 236.
When the manual valve 210 is switched to the N (or P) position, it is moved to the right by the spring 237. When the spool 236 is moved to the right, line pressure PL from the fourth control oil passage L4 is supplied to the 24th control oil passage L24, and the left spool 221 of the clutch control valve 220 is moved to the left, turning the main clutch CL OFF. be made into At the same time, the 42nd control oil passage L4□ is closed, the piston member 52 of the second speed change servo unit 50 is held as it is, and the speed change ratio is held as it is.

The throttle modulator valve 245 reduces the line pressure PL supplied to the 20th control oil passage L20 to create a predetermined modulator pressure PM, and supplies this to the throttle valve 240 via the 21st control oil passage L21.

The throttle valve 240 is operated in response to the suppression of the first cam 161 of the throttle cam mechanism 150, which is operated in response to the accelerator pedal or the throttle valve opening, and the throttle opening (or the accelerator The throttle pressure Pry corresponding to the opening degree) is supplied.

The shift control valve 250 is connected to the second cam 17 of the throttle cam mechanism 150, which is transmitted via the blade 252.
1 and the governor pressure P from the 49th control oil passage L4°
. This valve controls the supply and discharge of the line pressure Pt to the upper and lower cylinder chambers 54, 55 of the second shift servo unit 50 by the left and right movement of the spool 251 which receives the pressing force from the spool 251. This allows the throttle opening (
The gear ratio is controlled according to engine speed (or depression of the accelerator pedal) and engine speed.

The kickdown control valve 258 increases the gear ratio by discharging hydraulic oil from the 42nd control oil passage L4□ when the accelerator pedal is suddenly depressed while driving.
This is a valve for switching to the LOW side.

The engine rotation inhibitor valve 265 is activated when the engine rotation exceeds a predetermined rotation and the governor pressure P exceeds a predetermined value.
This is a valve that cuts off communication with 4e.

The second solenoid valve 285 is a normally closed type valve, and is opened when the controller 100 detects sudden braking. For this reason, line pressure PL is normally supplied to the right end of the shift control valve 250, but in the event of sudden braking, this is released, the spool 251 of the shift control valve 250 is moved to the right, and the gear ratio is shifted to the LOW side. controlled so that

The operation of the engine brake control valve 120, which is used in a transmission having the control device configured as above, will be explained.

As is clear from the explanation of FIGS. 1 and 2, when the wheels are driven by the engine E via the continuously variable transmission T, the pressure in the first circuit oil passage La becomes high; in this case, The check valve 139 closes the seventh circuit oil passage Lg.
is closed, the engine brake control valve 120 has no effect.

On the other hand, when the vehicle is decelerating, the hydraulic motor M is driven by the driving force from the wheels, and the pressure in the first circuit oil path La is higher than that in the first circuit oil path La due to the discharged oil.
Check valve 139 is opened. In this case, if the vehicle speed is below a predetermined vehicle speed (for example, 15 km/H), the controller 100 does not operate the first solenoid valve 280, which is open, and the clutch-on valve 232 is closed. The spool 231 is in a left moved state. For this reason, the 60th control oil path L g
The oil pressure in o is zero, and the spool 122 of the engine brake control valve 120 is in the state shown in FIG. 2 (moved to the left), and as described above, the engine brake is not applied.

Therefore, for example, when traveling downhill without pressing the accelerator pedal, the vehicle coasts without engine braking until the vehicle speed reaches a predetermined vehicle speed. When the vehicle speed exceeds a predetermined vehicle speed, the controller 100 detects this and operates the first solenoid valve 280 to close it. With this closure, the 51st
Control oil path LI5. Line pressure PL is supplied from the clutch on valve 230 to move the spool 232 to the right.

As a result, the main clutch CL is turned ON (connected) and the line pressure Pt is applied to the 60th control oil passage L80.
is supplied.

The spool 122 of the engine brake control valve 120 is moved to the right by the line pressure Pt from the 60th control oil passage Leo, but the right movement in this case is done slowly as explained in FIG. The seventh circuit oil passage Lg is slowly closed. Therefore, the oil discharged from the hydraulic motor M driven by the wheels begins to flow toward the hydraulic pump P, and the engine brake gradually increases, causing coasting. Smooth transition from state to engine brake operating state.

Note that during coasting, the engine rotation is in an idling state and the gear ratio is LOW (maximum), but as the engine brake gradually increases, the engine rotation increases, so the spool 251 of the shift control valve 250
The governor pressure Pa acting on increases, and the gear ratio becomes TOP.
transferred to the side. When transitioning from coasting to engine braking, the engine braking force gradually increases to prevent rapid deceleration, but at the same time, the gear ratio also shifts to the TOP side where the engine braking force decreases. As a result, the increase in engine braking force becomes more gradual.

C1 As described in detail of the invention, when a vehicle equipped with the power transmission device according to the present invention runs on a drop-off road etc. without pressing the accelerator pedal, when the vehicle speed is less than a predetermined vehicle speed (low speed case) In this case, the oil discharged from the hydraulic motor driven by the wheels is flowed to the suction side of the hydraulic motor via a connecting oil passage (bypass oil passage), so the vehicle coasts without engine braking. Then, when the vehicle speed exceeds a predetermined vehicle speed, the engine brake control valve is operated and the connecting oil passage is closed, so that from this point on, an engine brake action is applied. In this case, the communication passage is gradually closed by the damper function of the engine control valve, so that the engine braking action also gradually increases. Therefore, the transition from the coasting state to the engine braking state is smooth and the shift is smooth.
It can be done without any trouble.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram of a continuously variable transmission equipped with a power transmission device according to the present invention, Fig. 2 is a hydraulic circuit diagram showing a part of the hydraulic circuit in detail, and Fig. 3 is a hydraulic circuit diagram of the continuously variable transmission described above. 4 and 5 are control circuit diagrams of the continuously variable transmission. 30.50... Servo unit for speed change 95... Clutch valve body 97... Cam member 120... Engine brake control valve 130... Clutch servo unit 140... Servo unit for forward and backward movement 210...・Manual valve

Claims (1)

[Scope of Claims] 1) a hydraulic pump driven by driving force from an input shaft; a hydraulic motor driven by hydraulic pressure from the hydraulic pump to drive an output shaft; a discharge port of the hydraulic pump; A first oil passage that communicates a suction port of a hydraulic motor, a second oil passage that communicates a suction port of the hydraulic pump and a discharge port of the hydraulic motor, and a communication between the first oil passage and the second oil passage. a check valve disposed within the communicating oil passage that allows only the flow of hydraulic oil from the second oil passage to the first oil passage; It consists of an engine brake control valve that opens and closes a communication oil passage.The engine brake control valve opens the communication oil passage when the vehicle speed is below a predetermined vehicle speed, and opens the communication oil passage when the vehicle speed exceeds the predetermined vehicle speed. The oil passage is closed, and the engine brake control valve is provided with a damper function that gradually closes the opening degree when the connecting oil passage is closed by the engine brake control valve. Hydraulic power transmission device.