JPS6149127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides hydrostatic pressure control for obtaining precise displacement of variable displacement pumps and motors in transmission systems and for obtaining accurate, uniform actuation and steering control of dual hydrostatic transmission systems. The present invention relates to a control device for a transmission device. This control device can be used in many applications involving truck type vehicles to provide both propulsion and steering of this type of vehicle.

The applicant has a large amount of prior art relating to hydrostatic pressure transmission devices. In view of the pertinent prior art, the disclosure herein relates to control devices for hydrostatic pressure transmission devices, and more particularly to:
It concerns a control device for a two-channel hydrostatic pressure transmission device, in this latter device a main circuit including a pressure reducing valve for setting the control pressure, and a main circuit for establishing the operating direction of the two hydrostatic pressure transmission devices. A directional control valve and a horsepower control valve to prevent stalling of the prime mover are each connected to a pair of branch circuits provided for each hydrostatic transmission device, and each branch circuit is connected to a pair of branch circuits provided for each hydrostatic transmission device. It should be noted that there is a control valve. The steering control valve varies the control pressure supplied to the displacement controller of a particular hydrostatic transmission and also provides a staging effect in each transmission, in which case the transmission pump pumps to the initial maximum displacement of the motor. Almost full volume is reached before it decreases.

U.S. Pat. No. 3,187,509 discloses a displacement control valve in FIG. 2 which acts as a directional valve and is in communication with a manually controllable thrust valve 130. This thrust valve acts as a pressure reducing valve that can be manually adjusted. This patent is
Two systems having a main circuit with a speed and direction establishing member operable by only one handle and a pair of branch circuits each having a steering control valve which can be operated manually. It does not disclose a control system, nor does it disclose many features in a capacity control system for transmission devices that provide precise capacity control.

U.S. Pat. No. 3,230,699 allows a decrease in motor displacement to follow an increase in pump displacement by associating a control valve for the motor with a spring that is stronger than the spring in the control valve for the pump. is disclosed. This patent also discloses a rotatable shaft with a cam to modify the operation of the valve.

U.S. Pat. No. 3,247,669 discloses the use of springs of different strengths in a displacement control device for a motor and pump of a hydrostatic transmission device to cause actuation of the motor after actuation of the pump. are doing.

US Pat. No. 3,411,297 discloses the use of a staging valve 21 to change the displacement of the motor after the pump has been adjusted to maximum displacement.
This controller always responds to a higher control pressure in one of the two conduits to ensure that a higher control pressure is applied to one end of the control valve for the motor displacement controller. Does not include shuttle valve for movement. Additionally, this patent discloses a feedback system that cooperates with the pump.

U.S. Pat. Nos. 3,247,919 and 3,349,860 relate to dual hydrostatic pressure transmission devices. In the former, one handle provides speed control of both transmissions and a second handle provides steering. These handles actuate control cams to mechanically vary the operation of the transmission. Control cams that set the speed and direction of actuation are modified when steering control is desired. In the latter, steering is obtained through the use of a separate hydrostatic transmission device that operates to provide input to the differential.

Furthermore, the applicant has proposed that each hydrostatic pressure transmitting device be manually controlled by a separate control circuit, and that each of the hydrostatic pressure transmitting devices be cooperated with a pressure reducing valve to set the control pressure. The present invention has a prior art technology of a control device for a two-system hydrostatic pressure transmission device, which is provided with a directional control valve for determining the direction of operation. A horsepower control valve, or anti-stall valve, is connected in the control circuit for both hydrostatic transmission devices, in which case an engine overload causes an increase in the control pressure in the control device for both hydrostatic transmission devices. Produces a uniform decrease. In this prior art control, there are two handles, each handle independently setting one speed for the transmission, in which case there is no positive control between the speeds of both transmissions. There is no direct relationship.

Further prior art is U.S. Pat. No. 27,488, in which two separate controls as described above are operated by only one main control handle. In this patent, the control system for each hydrostatic transmission device has its own speed control and direction establishment system and horsepower control valve. Furthermore, as another conventional technology, Japanese Patent Application Laid-Open No. 48-16059
In the invention described in this publication, a two-system hydrostatic pressure transmission device is dealt with similarly to the present invention, however, in this prior art, the present invention There is already a fundamental difference in that a variable displacement motor is used as the motor, whereas a fixed displacement motor is used as the motor, and therefore these two systems are static. When the hydraulic transmission device is applied as a propulsion device for a vehicle, the speed change range of the vehicle is narrowed to, for example, about 1/4 compared to the vehicle to which the device of the present invention is applied. In the technology, the speed and direction of the vehicle are controlled by one speed change lever 1.
6, the speed control valve 20 is operated.
0 is the shaft 56 operated by the lever 16
It includes a valve 44 which is actuated through a neutral position and is adapted to control speed by linearly moving the valve 44 from a neutral position. However, the valve 4 due to such linear movement
The control of the valve 44 is extremely sensitive, and it is particularly difficult to control the speed in the low speed range of the vehicle when the valve 44 is near the neutral position. In contrast, in the present invention, as will be explained in detail later, speed control and direction control are performed by rotating the shaft 132 with one control handle 100, thereby controlling the pressure reducing valve by rotational motion. 12
5 and the direction control valve 142, this conventional method has the advantage that these controls can be easily and accurately carried out regardless of the speed of the vehicle. This is different from technology.

An important feature of the invention is that the main control circuit, which is operable by only one control handle, establishes a control pressure and a common speed for both hydrostatic pressure transmission devices and their direction of operation; , has two branch circuits respectively associated with each hydrostatic transmission device, and furthermore, each branch circuit has two branch circuits each associated with a respective hydrostatic transmission device, such as a double tracked vehicle with a track driven by a respective hydrostatic transmission device. For steering of a typical vehicle, there is a dual system control system for a pair of hydrostatic transmissions having a manually operated steering control valve for varying the speed of one transmission with respect to that of the other.

Another feature of the invention is to include the actuation of a steering control valve in the branch pipe to vary the control pressure to the hydrostatic transmission device which is cooperated to vary the speed to produce the swirl. The application of the control pressure to the hydrostatic transmission device is then reversed, thereby causing the vehicle to be imparted with a spin rotation about a center located within the space between the tracks.

Speed control of the hydrostatic transmission device is controlled by a pressure reducing valve in the main control circuit, which valve includes an adjustable device to determine the desired control pressure for the set speed. There is. A manually operated handle has a cam cooperated with it,
Cooperatively with the adjusting device, the cam surface also has two similar portions extending in opposite directions from a neutral center position, in this case establishing the direction of actuation of the hydrostatic pressure transmission device. The control pressure is effectively set such that rotation of the handle in either direction establishes a speed of the transmission that is dependent on the amount of rotation of the handle.

Another feature of the invention is the inclusion of a known horsepower control valve, which also acts as a safety valve with respect to the pressure generated by the control pump operated by the prime mover, and which A feature of the invention is also an improvement in a displacement control device for the swash plate of a variable displacement pump and a variable displacement motor of a transmission, which acts against a control arm connected to a control valve of the displacement control device. includes a pair of springs, and
an adjustment structure for the spring seat of one of the springs to obtain a zero position relative to the control valve when the associated swashplate is in the neutral position; including the use of a shuttle valve between the volume control device and the volume control device.
The shuttle valve directs the highest control pressure present in either of the first two lines of the shuttle valve to one end of the control valve for motor displacement;
It acts so that the motor is always adjusted in the same direction.

Another feature of the invention is to obtain a linear relationship between the conduction velocity and the conduction velocity in response to the control pressure.
and the motor displacement, and the use of a feedback device for a control valve in a displacement control device for a motor that provides a non-linear relationship between the motor displacement and the motor displacement. This means that
The control pressure is varied by the steering control valve, thus ensuring uniform speed control.

Hereinafter, the present invention will be explained based on the accompanying drawings.

A two-system hydrostatic pressure transmission device according to the invention is shown in FIG. These transmissions, in one embodiment, can each be used to separately operate the tracks of two tracked vehicles. Referring to the hydrostatic pressure transmission device shown in the upper half of FIG.
It is connected to 5. The variable displacement pump 10 is
The motor 15 has an input shaft (not shown) that is driven from a power source, such as a vehicle engine, and an output shaft (not shown) that is connectable to drive gearing, such as for a vehicle track. ).

Preferably, both pump 10 and motor 15 are of the axial piston type with rotatable cylinder blocks, each cylinder block having a plurality of cylinders in an annular configuration, and pistons 30 and 31 having rotatable cylinder blocks. , each end of which can be moved back and forth within the cylinder. The pump 10 has a variable angle reversible swash plate 32 engaged by the projecting end of the piston 30 to provide initial control of the speed of the transmission as well as its direction of rotation. The motor 15 has a variable angle swash plate 33 that is movable from the maximum volume position shown to a minimum volume position slightly greater than zero. Swash plate 33 engages piston 31 and causes its reciprocation and rotation of the cylinder block and the output shaft of the motor connected thereto as high pressure fluid is supplied to the motor from the pump.

A pair of pump control cylinders 36 and 38 are provided for positioning the pump swashplate 32. Each cylinder has pistons 41 and 4, shown schematically by 39 and 40, respectively.
It has a spring structure acting on 2. Pistons 41 and 42 pivot swashplate 32 via links 45 and 46 connected to the pistons. Control cylinders 36 and 38 position swashplate 32 in response to the supply of working fluid to the cylinders by conduits 48 and 50. Centering spring 3
9 and 40 act to position the pump swashplate 32 via the piston in its normally neutral position as shown when no working fluid is supplied via the conduit. In this position there is no active output from the pump. The control cylinders are conventional and of the single-acting type, whereby the entry of pressurized fluid into one cylinder is controlled by the swashplate 32.
tilting or swirling the swashplate in one direction, and the inflow of pressurized fluid into the opposite cylinder causes a reverse pivoting of the swashplate, thus reversing the flow from the pump 10; Therefore, the output of pump 10 is reversed.

A positive displacement charge pressure pump 53 is provided to be driven by the engine, or prime mover, of the vehicle or other equipment using the transmission system, via a suitable device. It's getting old. Pump 53 communicates with tank 54 via an intake conduit 55 and also has a discharge conduit 56. The capacity of the charging pump 53 is sufficient to displace leaking fluid and also to provide working fluid to a pair of control valves of a volume control system for the pump and motor (described below) and to provide further conduction. In order to maintain the device at a low temperature, it is sufficient to supply cooling fluid to the hydrostatic transmission device in excess of the amount required for the above purpose. Additionally, the pump 53 develops sufficient pressure such that the force within the cylinder to position the pump and motor swashplate is
The forces tending to move the swashplate, such as those generated internally by the action of the pump and motor, may be exceeded.

A pair of spring biased check valves 57 and 58 interconnect conduit 56 and the pump and motor. The main pipes 11 and 12 are communicated with each other. Check valves 57 and 58 supply makeup and cooling fluid to the low pressure side of the transmission through each check valve, and the pressure in the high pressure line keeps the check valves closed. It's summery. A spring biased refill safety valve 63 communicates with conduit 56 and serves to vent excess fluid. A shuttle valve 70 is provided to establish a circuit between the main lines 11 and 12 at low pressure and the low pressure relief valve 68. This shuttle valve 7
0 has conduits 72, 74, 7 in conduits 11 and 12.
6 and 78, charging pump 5
3 provides a device for removing heating oil which is replaced by cooling oil supplied by No. 3. The fluid pressure in conduits 11 and 12 is, respectively,
Acts to properly position shuttle valve 70 via conduits 72 and 76, thereby
Communication is established from the low pressure relief valve 68 via conduit 80 to the low pressure side of the conductor circuit, either by conduit 74 or conduit 78, so that the heating fluid passes through heat exchanger 79. , can be drained into the tank. Shuttle valve 70 is spring centered in the closed position and thus
During the movement of pressure reversal in the main lines 11, 12, no high pressure oil is lost from the circuit.

The transmission device includes overpressure relief valves 81 and 8 communicating with the main lines by conduits 83 and 84, respectively.
Contains 2. These valves eliminate abnormally high pressures in either of the two main lines 11 and 12 by decirculating surge pressures that may occur during rapid acceleration or hard braking.
This is something that can help prevent this. In response to this high pressure, the overpressure relief valves 81, 82 are displaced, draining excess oil to the low pressure side of the transmission circuit. For example, when excessively high pressure is present in conduit 11, conduit 83
Fluid pressure within causes valve 81 to shunt fluid to conduit 12 through conduit 84 .

A bypass valve 90 is connected into conduits 83 and 84 by a pair of conduits 91 and 92 and to the outlet of charge pump 53 by conduit 93. When the pressure from charge pump 53 is removed, bypass valve 90 transitions to connect conduits 91 and 92, creating a short circuit and free-rotating operation.

Motor 15 has a pair of actuation cylinders 94 and 95 containing pistons, link members 96 and 97 pivotally connected to swash plate 33, and conduits 98 and 99 to each of the cylinders. and supply them with working fluid.

The second hydrostatic pressure transmission device, shown in the lower half of FIG. 1, is of the same construction as just described and is also supplied with fluid via conduit 55 from tank 54. Corresponding components of the second hydrostatic pressure transmission device use the same reference symbols with the addition of a dash (').

A two-way control system is shown primarily in FIG. 2A, and in particular a main control circuit for setting the operating speed and direction of the two hydrostatic transmission devices shown in FIG. ing. FIG. 2A additionally shows a pair of branch circuits extending from the main control circuit containing structures for providing steering capability. The control device is operated by three control handles. That is, control handle 1
00 is operable to set the speed and direction of actuation. A control handle 100 is operable to establish a change in the speed of one transmission and its direction of operation for the possibility of steering in one direction, and a third control handle 102
is operable to control the operating speed and direction of other hydrostatic transmission devices for the possibility of steering in turns in other directions.

The main control circuit includes a control pump 110 suitably driven by a prime mover, such as a vehicle engine, to provide control fluid used to establish a control pressure to the system. control pump 110
The output of is directed via conduit 111 to a variable orifice valve 112 having a rotatable member 115 having a variable orifice 116. The position of this valve 112 is connected via a connecting member 117 to an engine throttle linkage (not shown) to provide a differential pressure across the valve 112 depending on the engine settings, and a variable orifice. 116
The aperture of the diaphragm varies in direct relation to the aperture setting. The differential pressure is constant for each engine set at rated speed. Variable orifice valve 11
2 operates to signal the speed of the engine, so that if the speed of the engine is reduced below that normally obtained by the throttling setting, a signal from the control pump 110 is signaled. There is an output flow resulting in a drop in differential pressure across the valve orifice 112. A conduit 117 extends from the variable orifice valve 112 to a pressure control valve 120 which ensures adequate backpressure downstream of the variable orifice valve 112 to operate the control system and which also provides a pressure control valve 120 within the conduit 118. gives a controlled constant pressure, denoted as P _R . Conduit 118 extends to a pressure reducing valve 125 (ratio control valve), which serves to establish a certain control pressure to obtain uniform speed control of both hydrostatic pressure transmission devices. Pressure reducing valve 125 includes a valve spool 126, which controls communication between inlet conduit 118 and outlet conduit 127. The valve spool 126 is 1
At one end, outlet pressure is received therefrom via a conduit 128 having a flow restriction member and an adjustable spring 126a, and at the opposite end, a spring 126a.
29 has been affected. This spring 129 is movable inside the valve housing. It is engageable with a speed setting cam 131 located partially inside the cylinder member 130 and connected to a rotatably positioned shaft 132 at one end, which shaft 132 can be manually operated. It is thus rotated by the handle 100 which is actuatable.

The cam 131 has a pair of oppositely sloped cam surface portions 1 extending in opposite directions from a neutral position.
60 and 161, but this cam 131
is shown engaged with member 130 in FIG. 2A. Control pressure fluid supplied by conduit 127 from pressure reducing valve 125 is directed to horsepower control valve 140, whose primary function is to prevent stalling of a prime mover, such as a vehicle engine. and therefore can also be referred to as an anti-stall valve. A conduit 141 extends from anti-stall valve 140 to directional control valve 142, which valve 14
2 has a valve spool 143 which can be positioned by a link 144 which rotates and positions the shaft 1 by a manually actuated handle 100.
32. Valve spool 14
Position 3 determines the normal operating direction of the hydrostatic pressure transmission device.

The structure shown in FIG. 2A above constitutes a main control circuit in which the positioning of the handle 100 determines the normal operating direction and basic common uniform velocity for the two hydrostatic pressure transmission devices. do. The first outlet conduit 150 from the directional control valve 142 is
It branches into a pair of conduits 151 and 152, each branch conduit being associated with a respective hydrostatic pressure transmission device. It has two branch conduits 154 and 155 extending from the directional control valve 142. In the illustrated position of the mandrel 143, the conduit 141 is closed and the conduits 150, 153 are drained.

When the shaft 132 is rotated by a force applied to the handle 100 from the position shown in FIG. Fluid may be directed into one of conduits 150 and 153 to operate the conductor in one direction, or flow may be directed to the other conduit and actuated in the opposite direction. Two portions 160 and 161 of the cam surface of cam 131
are mirror symmetrical to each other, and rotation of the shaft 132 in either direction causes the spring 12 of the pressure reducing valve 125 to
A degree of compression of 9 occurs, setting a certain desired control pressure for the speed of operation of the hydrostatic transmission device.

Branch conduits 151 and 154 from the main control circuit
are connected to the steering control valve housing 170, indicated generally by 171, while corresponding branch conduits 152 and 155 are connected to the steering valve housing 172, indicated generally by 173. connected inside. The steering control valve 171 has a pair of output conduits 1 extending therefrom.
75 and 176 and extend to the pump and motor displacement control device shown in FIG. 2B. Steering control valve 173 has a similar pair of output conduits 177 and 178, which also extend to volume control devices (not shown) for other transmission devices. Each of the steering control valves is of identical construction and the displacement control devices for the pump and motor of the hydrostatic transmission are also identical, so that the following description will be given of the The steering control valve 171 and displacement control device shown in FIG. 2B will be described in detail with the understanding that the structure is the same for other hydrostatic pressure transmission devices.

A control pressure signal is provided to one or the other of branch conduits 151, 154 depending on the position of directional control valve 142, connecting these conduits to valve spool 180.
A bore in a valve housing 170 to which the valve is movably mounted communicates. The position of the valve spool 180 is
Controlled by a handle 101, the handle 101 is connected to a rotatable shaft 181 supporting an eccentrically pivoted link 182 pivotally connected to the upper end of a valve spool 180. . In the position of the valve as shown in FIG. 2A, and assuming control pressure is supplied to branch conduit 151, the control pressure fluid enters the bore of the valve and reduces the diameter of the valve spool. The flow around the blown portion leads to an output conduit 176 leading to a volume control device. This output conduit 17
6 supplies the total control pressure to the volumetric controller. The supply of this control pressure provides operation of the associated hydrostatic pressure transmission device at the desired rate as determined by setting the control pressure by the pressure reducing valve 125. In a turn of the vehicle in one direction, the speed of the hydrostatic transmission device in cooperation with the steering control valve 171 is reduced. handle 10
1 is shown in FIG. 2A, the valve spool 18
0 downwardly, so that valve 142 has its spool 143 displaced upwardly from the condition shown in FIG. Directional control valve 142
It is branched into a branch conduit 154 which is connected to a tank port 185 which is connected to the tank port 185. By this,
Decrease control pressure to reduce speed. This branched flow traverses the lands of valve spool 180, which is provided with external slots 186 above the lands, and these slots 186 act as variable orifices. That is, as valve spool 180 is lowered from the position shown in FIG. 2A, it increases in size and progressively decreases the control pressure supplied to the volume controller via output conduit 176. These slots 186 do not extend the entire length of the land, so that the land is continuous in its lower portion as viewed in FIG. 2A.

Valve spool 180 has two limit positions: an upper limit position is shown in FIG. 2A, and an opposite limit position resists the action of spring 187 within the valve housing. This is the fully lowered position of the valve spool. In the fully lowered position, there is a reverse flow of control pressure fluid with respect to output conduits 175 and 176, thereby reversing the direction of operation of the associated hydrostatic pressure transmission devices. This action is accomplished by a pair of radial openings in the valve spool 180 that allow the internal passageway 18 in the valve spool 180 between the branch conduit 151 and the output conduit 175 to
8, this valve spool 180 extends an internal passage 188 to the surface of the valve spool, and these openings are indicated by 189 and 190. This reverses the direction of operation of the cooperating hydrostatic transmission device, in which case a spin turn of the vehicle occurs and the vehicle is
Rotate around an axis between two endless tracks.

If the directional control valve 142 is shifted downwardly to obtain the opposite direction of operation of the hydrostatic pressure transmission device,
Pressure is supplied to a branch conduit 154 leading to a steering control valve 171, and in the position of valve 171 shown in FIG. . Similarly, the control pressure is reduced by branching as the valve spool 180 is lowered by a slot above the land of the valve spool, and the direction of actuation is reduced by a slot 186 above the land of the valve spool 180.
The land having the output conduit 154 connects the branch conduit 154 to the output conduit 17
5 to occlusion, at which time a control pressure signal is supplied to the output conduit 176, resulting in an opposite direction of movement of the hydrostatic pressure transmission device.

The magnitude of the control pressure reduction depends on the relative dimensions of orifice 195 in branch conduit 151 and the discharge characteristics of valve 171. Sleeve 196, which is disposed within the bore of the valve housing and movably receives valve spool 180, has a suitable flow path and also preferably reduces the effects of orifice size tolerances. An orifice passageway 197 is provided that communicates with the branch conduit 154.

As shown in FIG. 2B, the steering control valve 1
Output conduits 175 and 176 extending from 71 connect to opposite ends of a volume control valve 200 for positioning a control valve spool 201 movable within the valve housing. The control valve 200 additionally has a pair of tank connections 202,2.
03 and the aforementioned pump control cylinders 36 and 3
It has connections to conduits 48 and 50 leading to 8. The working fluid is passed through conduit 205 to control valve 200.
(FIG. 1), this conduit 20
5 is supplied by charge pump 53 of FIG. 1, with its output conduit 56 connected to conduit 205.

The swash plate 32 for the pump is shown in a central position in FIG. 2B, as raised by springs 39 and 40 inside the cylinder. conduit 1
Assuming that the control pressure signal directed to 76 provides forward movement of the hydrostatic transmission device,
This results from the control pressure displacing valve spool 201 to the left from the position shown in FIG. be moved by Alternatively, if a control pressure signal is provided to output conduit 175, the control pressure signal is applied to the left hand end of valve spool 201;
Spool 201 is displaced to the right as viewed in FIG. 2B, thereby applying actuating fluid from conduit 205 to piston 42 and displacing swashplate 32 in the opposite direction. Conduits 175 and 176 that additionally connect to control valve 200 are connected to shuttle valve 21.
It extends to 0. Shuttle valve 210 vents to one end the highest control pressure present in either output conduit 175 or 176, thereby always regulating motor swashplate 33 in the same direction.

The control valve 220 of the motor displacement controller has a valve spool 221 whose right hand end is connected via a conduit 222 extending from the shuttle valve 210.
Always under the highest control pressure. control valve 220
The opposite end of conduit 22 includes branch conduits 224 and 225 connected to shuttle valve 210.
It has 3. Control valve 220 is of the same construction as control valve 200 and also includes a pair of tank connections and a conduit 226;
branches from a conduit 205 connected into an outlet from the charge pump 53 and supplies working fluid for operation of the volume control device to the motor swashplate 33.

Referring to a displacement control device for a pump, the valve spool 201 places the swash plate 32 in a neutral position and the position of the valve spool 201 is partially controlled by a pivotably connected arm 230 to the neutral position. The arm 230 is also connected to the valve spool for movement therewith and includes a pair of springs 231 that engage opposite sides of the arm to act in opposition to each other.
and 232. The zero position of the valve spool with the swash plate 32 in the neutral position is determined by the rotatable adjustment member of the threaded spring seat member 233 relative to the spring 232, resisting the action of the spring 231 to obtain the desired zero position. The spring seat 233 is set by advancing or retracting a rotatable adjustment member to vary the compression of the spring 232. Additionally, the volume control device includes a feedback device including an arm 241 on a fixed pivot 242 and a pivotably mounted link 240 having a seat at one end thereof for a spring 231. have. When valve spool 201 is displaced, control arm 230 is similarly displaced and
This causes springs 231 and 232 to become unbalanced. Displacement of spool 201 causes pivoting of swash plate 32, thereby causing feedback link 24
0 to vary the compressive force on the spring 231, in which case the valve spool 201 is in a neutral flow blocking position when the spring forces are balanced again. This effect is the same regardless of the direction in which the swash plate 32 is pivoted.

As previously mentioned, the highest control pressure is always in conduit 222.
in which the pressure is directed to the valve 220 of the motor displacement controller through the valve spool 221 to the second B
It operates to move to the left as seen in the diagram. The valve spool 221 has a control arm 250 movable therewith and also has a pair of springs 25
1 and 252 engage opposite sides of control arm 250 and have opposing effects. Spring 251 is applied to obtain a zero position relative to valve spool 221.
It has an adjustable, threaded spring seat member 253 on the fixed mounting member. Additionally, spring 251 is similar to springs 231, 232 and 25.
2, thereby making the valve spool 2
21 is permanently open towards conduit 98 and is responsive to the control pressure until the value of the control pressure exceeds the control pressure which acts to substantially completely displace the valve spool 201 of the pump volume control valve. It does not change. This provides staging of the transmission elements so that the pump swashplate 32, which was in a neutral position, moves to approximately its maximum displacement before any movement of the motor swashplate 33. do. Following maximum displacement of pump swashplate 32,
The motor volume is decreased as the control pressure increases.

This effect is illustrated by the graph in FIG. 4, where the control pressure obtained by setting the pressure reducing valve 125 is blotted as the ordinate, and the pump and motor volumes are plotted as the abscissa. It is plotted. When the control pressure increases from (a) to (b), the pump volume changes from neutral to maximum, as indicated by the sign at the bottom of the horizontal axis, and at about the same time the pump reaches full volume. death,
The volume of the motor decreases progressively from maximum to minimum as the control pressure moves from value (b) to value (c), as shown by the markings above the horizontal axis.

Shuttle valve 210 has a pair of internal passageways opening into valve spool 260 and opposite ends thereof;
A pair of radial passages 261 and 2 to the surface of 0
62. These passages 261,
262 provides pressure communication to each opposing end of shuttle valve spool 260 in output conduits 175 and 176. Assuming the greater control pressure is in conduit 175, shuttle valve spool 260 is displaced upwardly, causing conduit 1
75 is in communication with conduit 222 . If there is greater control pressure in output conduit 176, this pressure will be directed to the upper end of shuttle valve spool 260, displacing the valve downwardly, so that output conduit 176 is in control of motor displacement. It is in communication with a conduit 222 leading to a control valve 220 of the device. In any of the above conditions, the branch conduit 224,
Or, one or the other of 225 is the output conduit 1
75 and 176, but these conduits extend back to the steering control valve 171 for appropriate connection to the tank at the directional control valve 142.

To consider the feedback system of the motor displacement controller, reference is first made to FIGS. 5 and 6.
In order to maintain the same steering radius of the vehicle when changing ground speed during a turn, there must be a linear relationship between the transmission control pressure and the output speed, as shown in the diagram in Figure 5. It won't happen.

The feedback device for the motor displacement controller has a cam which adjusts the speed of the transmission and the motor to obtain the linear relationship between the control pressure and the speed of the transmission shown in the diagram of FIG. The relationship shown in the diagram of FIG. 6 is given between the volume of . Without the cam, the relationship between pressure and speed shown in FIG. 5 would not be linear at higher control pressures, in which case one of the steering control valves 171 or 173 would It is possible to have an indirect relationship between the speeds of two hydrostatic transmission devices when operated to obtain one transmission operating in different speed ranges. This results in an uncontrolled relationship in vehicle turns.

Reference is now made specifically to the feedback system for a motor displacement controller shown in FIG. 2B. A link mechanism connected to the swash plate 33 connects the arm 270 to the swash plate 3.
This arm 270 is connected to link 2.
71, an arm 272 is pivotably connected to a fixed bracket 273, and a cam roller 274 is provided on the end of the arm 272. A cam 275 pivotally mounted on a fixed mounting member 276 has a spring seat for spring 252 and has a cam surface that cooperates with cam roller 274 .

The actuation of the cam 275 is such that there is a greater rate of change in the compression of the spring 252 in response to a given control pressure signal when the motor is operating towards the minimum volume range of operation. This allows relatively small changes in the compression exerted on spring 252 to be obtained as the motor volume varies near the maximum volume range of motor operation. Thus, as swashplate 33 pivots counterclockwise as viewed in FIG. The pressure on spring 252 is decreased until a balance is achieved to bring it to a neutral position where it is closed from communication with the spring 252. This balance is such that the control pressure acting on the right hand end of control spool 221 plus the force of spring 252 is stronger than the force of spring 251.
is equal to some force resulting from the pressure acting on the left hand end of control spool 221.

It is clear that the relationship between the cam and cam roller shown in FIG. 2 can be reversed so that the cam is associated with a follower that is associated with a feedback link and a spring seat. be.

A cam such as cam 275 designed for a hydrostatic transmission system using only one variable displacement motor with one variable displacement pump, regardless of pump size or input speed, gives the desired relationship shown in FIG. The only requirement is
The actual control pressure to produce the total pump volume is similar for different pump sizes. Similarly, the same cam can be used for different motor sizes as long as the appropriate feedback link is used to create the relationship shown in FIG.

In a control device such as the one just described, only one
A control handle 100 controls the members of the main control circuit in order to establish a uniform control pressure and therefore a uniform speed for both hydrostatic pressure transmission devices as well as the direction of their operation. control handle 1
00 and the rotation of the shaft 132, the control valve 142 is approximately positioned, and the speed setting cam 131
Either of the cam surface portions 160 and 161 of
The spring force of the pressure reducing valve 125 is controlled. This applies the same control pressure to both branch circuits, each circuit having steering control valves 171 and 173. When it is desired to obtain non-uniform actuation of the transmission device, either handle 101 or 102 is manipulated to vary the control pressure applied to the volume control device for the associated hydrostatic pressure transmission device. do. The relationship of the rotation of the handle 100 to the establishment of the control pressure by the pressure reducing valve 125 is shown in the diagram of FIG. 3, in which the control pressures (a), (b) and (c) are 4 corresponds to those given in Fig. 4. The first rotation of the handle determines the direction of actuation, and the magnitude of the rotation of the handle determines the control pressure.
Therefore, care should be taken in determining the speed of the hydrostatic transmission device.

As before, the steering control valve 171 is shown in one limit position, and when the handle is moved, the valve spool is progressively moved toward the other limit position, further increasing the movement. In the meantime, a portion of the control pressure fluid is diverted back to the directional control valve 142 via a connection to the tank, and the entire movement of the steering control valve to the opposite limit position also diverts the control pressure fluid to the volume control device. Actually reverse the direction.

When the steering control valve spool 180 is shifted to divert the control pressure, pressure is applied to either the conduit 175 or 176 connected to the tank by the directional control valve 142 and the flow to the tank is reduced. is established for each orifice 197 and 195 that limits the The establishment of this pressure, along with a decrease in control pressure, upsets the balance on the volume control device and causes the hydrostatic pressure transmission device to operate at a reduced speed.

The steering control valve 173 is connected to the output conduit 1 described above.
77 and 178, which are output conduits 175 and 17 to the steering control valve 171.
It corresponds to 6. Output conduits 177 and 178
is connected to a volume control device identical to that shown in FIG. 2B for the pump and motor of the second hydrostatic transmission device.

Horsepower control valve 140, shown in FIG. 2A, is a normally open three-way modulating valve in series with pressure reducing valve 125. This valve 140 is biased closed by an adjustable spring 300 acting on a valve spool 301. Variable orifice valve 1
The pressure present at the opposite end of 12 is such that the pressure in front of the variable orifice valve is applied to valve spool 301 via conduit 305 that connects to conduit 111 .
are added to opposite ends of valve spool 301.
The pressure downstream of the variable orifice valve is
01 via a conduit 306 connected to a conduit 118 detecting a controlled pressure P _R .
Added. When the engine is operating at or near rated speed for any selected throttling setting, the pressure drop across the variable orifice valve is reduced by the valve spool 30, as seen in FIG. 2A.
Spring 300 for maintaining 1 in the raised position
exceeds the force of the control pressure and allows the control pressure to pass through it without pressure loss. If the engine begins to operate below rated speed, the pressure drop across the variable orifice valve is reduced below the setting of spring 300, causing the valve spool 301 to move downward and the directional control valve restricting the flow path to conduit 141 leading to and begin draining control pressure fluid to the tank. This causes a decrease in the control pressure signal,
Reduce the speed of the hydrostatic transmission device to match the vehicle speed to the power capacity of the engine. If the vehicle is moving forward, operation of the horsepower control valve produces an equal but reduced control pressure on both hydrostatic transmission devices, causing the vehicle to move directly over the path. However, it operates at low ground speed. If the vehicle is in steering mode, the reduction in control pressure by the valve will proportionally reduce the control pressure in each hydrostatic transmission device. Prior art constructions by Applicants had one valve to obtain the same anti-stall.

Horsepower control valve 140 now also provides a vacuum for overpressure protection to control pump 110. This action is caused by an overpressure acting to displace the valve spool 301 in the conduit 305 upwardly against the spring 300 and the pressure _PR , connecting the conduit 305 to the tank. The condition that causes this action is when the oil used in the system is at a very low temperature and the variable orifice valve 11
2 and therefore an overpressure condition exists in conduit 305.

The functions and effects of the present invention are clear from the above description, but a summary thereof can be summarized as follows.

(i) In a control device for a two-system hydrostatic pressure transmission device,
The main circuit has a first valve for setting the control pressure to determine the speed of operation of the transmission and a second valve for determining the direction of operation of the transmission, both of which the valve is operable by only one control handle; (ii) the main circuit is connected to two branch circuits;
(iii) each branch circuit is led to a volume control device for each of the hydrostatic pressure transmission devices, and each branch circuit has its own steering control valve; (iv) each steering control valve provides a reduction in control pressure for the reduced speed of the associated hydrostatic pressure transmission device, or Such as providing a reversal of the control pressure fluid to obtain a reversal of the direction of operation of one of the hydraulic transmission devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a dual hydrostatic transmission system with two complete hydrostatic transmission systems; FIG. 2A is a schematic diagram of a portion of the control system for a dual hydrostatic transmission system; FIG. 2B is a schematic representation of one of the hydrostatic transmission systems 3 is a diagram showing the direction of operation and speed setting of the hydrostatic transmission device in response to the position of the manual control handle; FIG. 4 is a diagram of the variable displacement pump and Diagram showing the staging action of the motor; Figure 5 is a diagram showing the desired linear relationship between control pressure and output speed for the hydrostatic transmission device; Figure 6 is a diagram showing the relationship between linearity speed and control pressure. FIG. 2 is a diagram illustrating the non-linear relationship between the volume of the motor of the transmission and its control pressure with respect to the output speed; 100...control member; 120...pressure control valve;
142... Directional control valve; 151, 154; 15
2,155...Branch circuit; 171,173...Steering control valve; 175,176,177,178
...Output conduit.

Claims (1)

[Claims] 1 each having a variable displacement pump 10, 10';
variable displacement motors 15, 15'; pressure-responsive displacement control devices 32, 3 for variable displacement pumps 10, 10' and variable displacement motors 15, 15', respectively;
3; In a control device for two systems of variable volume hydrostatic pressure transmission devices having 32' and 33', a controller for establishing a control pressure for the two systems of variable volume hydrostatic pressure transmission devices; No. 1 valve (pressure reducing valve) 125
and a second valve (directional control valve) for setting the operating direction of the two systems of variable volume hydrostatic pressure transmission devices.
142 and only one control member (control handle and shaft) for actuating both the first valve (pressure reducing valve) 125 and the second valve (directional control valve) 142.
100, 132, and the first valve (pressure reducing valve) 1
25 and a second valve (directional control valve) 142, and two branch circuits 151, 154; 152 downstream of the first valve (pressure reducing valve) 125 and second valve (directional control valve) 142. , 155 and said branch circuit 151, 15 for modifying the control pressure to influence the mutual operation of said variable volume hydraulic transmission device.
4; 152, 155; each steering control valve 171, 173 has an output conduit 175, 176; 17;
7,178, each output conduit 175,1
76; 177, 178 each represent one variable displacement pump 10, 1 of a variable displacement hydrostatic pressure transmission device.
0' and the pressure-responsive displacement control device 32, 33, 32' for the variable displacement motor 15, 15';
33', and each output conduit 175, 176; 177, 178 has a volume control device 2 for the variable volume pump 10, 10'.
00 and a motor displacement control device 220 for the variable displacement motors 15, 15';
Upstream of the pump displacement controller 220 includes a shuttle valve 210 to ensure that the highest control pressure in the output conduits 175, 176; 177, 178 is applied to the motor displacement controller 220. A control device characterized by: