JPS627005B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotary tiller, a plow, a seeding machine,
Self-propelled working vehicles such as agricultural tractors, bucket carts, or shovels that are equipped with various working machines such as fertilizer applicators and wheel loaders that are used for transporting earth and compost, or for excavating the ground. (hereinafter referred to as "agricultural tractors, etc."), which is equipped with a hydraulic clutch type transmission for changing the traveling power and a mechanical transmission connected in series in this order. This invention relates to a traveling drive device for a certain agricultural tractor or the like.

When a traveling drive device such as an agricultural tractor is equipped with a hydraulic transmission that continuously changes and controls the vehicle speed by changing the rotation speed of a hydraulic motor, the hydraulic transmission generally includes a hydraulic pump and a hydraulic motor. A hydraulic transmission device (hydrostatic transmission) connects these pumps and motors through a pair of oil supply and exhaust circuits that form a closed circuit, and changes and controls the volume of the hydraulic pump to change the vehicle speed. However, a technique using an open-circuit hydraulic transmission, which is cheaper than such a closed-circuit hydraulic transmission, is disclosed in Japanese Patent Application Laid-Open No. 109228/1983.

The one in the same publication uses a hydraulic transmission to creep the work vehicle during heavy-load work, and a hydraulic motor supplied with hydraulic oil from a hydraulic pump is paralleled to a mechanical transmission for changing the driving power. The vehicle speed is changed by connecting and controlling the volume of the hydraulic motor.

However, with this structure, the variable displacement hydraulic motor is expensive, and if the angle of the motor swash plate is small, such as 2 degrees or 3 degrees, the number of revolutions becomes difficult to maintain. There is. In addition, in a structure in which a mechanical transmission and a hydraulic motor are connected in parallel like the one in this publication, the deceleration ability of the mechanical transmission cannot be used when the hydraulic motor drives the vehicle, so the vehicle cannot be driven at a low speed. It is necessary to use a large-capacity hydraulic motor to generate the torque, and for this reason as well, the hydraulic motor is expensive. Of course, the specially provided hydraulic pump also increases the cost of the travel drive.

The object of the present invention is to provide a particularly well-known traveling drive system in which a hydraulic clutch type transmission and a mechanical transmission for changing traveling power are connected in series with each other in this order. 1977-
When incorporating an open-circuit hydraulic transmission like the one in Publication No. 109228, it is possible to use the hydraulic transmission to handle tasks where it is desirable to creep the vehicle or change the vehicle speed steplessly. In addition to eliminating the need for a separate hydraulic pump by making the hydraulic pump for the clutch-type transmission also serve as the hydraulic pump for the above-mentioned hydraulic transmission, it is also possible to use a fixed-displacement type and small-capacity hydraulic motor as a hydraulic motor for the hydraulic transmission. In addition to suppressing the cost increase of the travel drive system as much as possible, the use of the above-mentioned hydraulic motor allows stable low rotational speeds of the hydraulic motor, making the vehicle speed stable even in the low speed range, which can be changed steplessly. An object of the present invention is to provide a novel traveling drive device for agricultural tractors, etc., which provides advantages to the user.

In order to solve this problem, the present invention provides a hydraulic clutch type transmission 2 and a mechanical transmission 3 connected in series in this order, as illustrated in FIG. 1. The following technical measures were taken for a self-propelled work vehicle such as an agricultural tractor.

That is, as clearly illustrated in FIG. 6, an oil supply direction switching valve 58 is connected to a hydraulic pump 55 for supplying hydraulic oil to the plurality of hydraulic clutches 18, 19, 20, 21 in the hydraulic clutch type transmission 2.
A hydraulic motor 41 is provided which is connected to the flow rate control valve 61 via a variable flow rate control valve 61. As illustrated in FIG. 1, while there is a transmission shaft 22 located on the driven side of the hydraulic clutch type transmission 2 and located on the driving side of the mechanical transmission 3,
The hydraulic motor 41 is operatively connected to the transmission shaft 22 via a clutch 48, as illustrated in FIGS.

Therefore, when the oil supply direction selector valve 58 is placed in a position to supply hydraulic oil to the hydraulic clutches 18-21 and the clutch 48 is disengaged, as in the conventional case,
The hydraulic clutch type transmission 2 and the mechanical transmission 3 allow the vehicle to travel while changing the vehicle speed in multiple stages.
1 to the position for refueling and clutch 48.
When the engine is turned on, the vehicle can be driven by the hydraulic motor 41 via the mechanical transmission 3. The vehicle speed when the vehicle is driven by the hydraulic motor 41 is
Continuously variable control is possible by changing the flow rate set in the flow rate control valve 61, and in this driving state, the rotation of the hydraulic motor 41 is decelerated by the mechanical transmission 3 and transmitted to the driving wheels (or a crawler replacing it). will be done. In the illustrated example, the clutch 48 can be engaged only in the first gear (lowest gear) of the mechanical transmission 3, as will be described later.
Although the rotation of the hydraulic motor 41 is significantly decelerated by the mechanical transmission 3 and transmitted to the driving wheels, if the clutch 48 can be engaged at other gears of the mechanical transmission 3, The rotation of the hydraulic motor 41 can be transmitted to the driving wheels by not only simply reducing the speed but also changing the rotation in a stepped manner.

When the vehicle is driven at low speed by the hydraulic motor 41, the vehicle speed is stabilized even when the flow rate controlled by the flow control valve 61 is low, and the low speed rotation of the hydraulic motor 41 is significantly reduced by the mechanical transmission 3 to control the driving wheels. Since the hydraulic motor 41 can be transmitted in both directions and there is no need to rotate the hydraulic motor 41 at an extremely low speed, it can be obtained extremely stably.

To explain an example, in FIG.
is a transmission case for an agricultural tractor,
Inside the transmission case 1, which constitutes a part of the body of the tractor, are a hydraulic clutch type transmission 2 which constitutes a main transmission for traveling power, and a mechanical transmission 3 which constitutes an auxiliary transmission for traveling power. are arranged in front and behind each other. Of these two transmissions 2 and 3, the hydraulic clutch type transmission 2 on the front side is a transmission connected to an engine 4 mounted on an agricultural tractor via a main clutch 5 (see above, Fig. 6). The mechanical transmission 3 is for selectively interlocking the shaft 6 and another transmission shaft 7 provided parallel to and below the transmission shaft 6 at an appropriate transmission ratio. The transmission shafts 7 and 8 are respectively configured to selectively interlock and connect the other transmission shaft 7 and another transmission shaft 8 provided on an extension thereof at an appropriate speed ratio. The other transmission shaft 8 mentioned above is
It constitutes the output shaft of the driving power transmission section consisting of both transmissions 2 and 3, and the transmission shaft 8 is connected to the ends of the transmission shaft 8 for transmitting the driving power after shifting toward the left and right rear wheels (not shown). A bevel gear 9 is provided.

In order of explanation, both the above-mentioned transmission devices 2 and 3
To explain the specific structure of the hydraulic clutch type transmission 2, which is a common structure, first, the hydraulic clutch type transmission 2 has a transmission shaft 6.
_F1 speed change gear 10, _F2 speed change gear 11, _F3 speed change gear 12, and R speed change gear 13, which are fixedly provided to
It is loosely fitted to another transmission shaft 7 and connected to the corresponding one of the transmission gears 10-13 on the transmission shaft 6 either directly (F gear) or indirectly (R gear) via the R intermediate gear 13A.
The gear is provided with an _F1 idler gear 14, an _F2 idler gear 15, an _F3 idler gear 16, and an R idler gear 17 which are meshed with the gears. On the other transmission shaft 7, each of the above-mentioned idler gears 14, 15, 16, 17 is arranged, and each idler gear 14, 15, 16, 17 is selectively coupled to the other transmission shaft 7. A multi-plate _F1 hydraulic clutch 18, _F2 hydraulic clutch 19, _F3 hydraulic clutch 20, and R hydraulic clutch 21 are provided for this purpose. The hydraulic clutch type transmission 2 shifts one idler gear 14, 1 by selective actuation of a corresponding hydraulic clutch 18, 19, 20 or 21.
5, 16 or 17 are selectively connected to other transmission shafts 7 to select forward 1st speed F ₁ , forward 2nd speed F ₂ , forward 3rd speed
The transmission shafts 6 and 7 are selectively connected at the gear ratio of speed _F3 or reverse 1st speed R.

The mechanical transmission 3 also includes a hollow transmission shaft 22 provided on the rear half of the transmission shaft 6, and this hollow transmission shaft 22 connects a large diameter gear 23 at its base end to another transmission shaft. By meshing with the small diameter gear 24 on the rear end of the transmission shaft 7, the transmission shaft 7 is always connected to the other transmission shaft 7 in a deceleration interlocking manner. Three speed change gears 25, 26, 27 are provided on the hollow transmission shaft 22,
Further, two integral shift gears 28 and 29 and another shift gear 30 are provided on another transmission shaft 8 and are spline-fitted to the shaft 8. Furthermore, a meshing clutch 31 is interposed between the transmission shafts 7 and 8, and is constructed by forming pawls 31a and 31b that can be engaged with the end of the other transmission shaft 7 and the boss portion of the shift gear 30. As a result of the above, the mechanical transmission 3 is
The shift gears 28, 29, and 30 are selectively slidably displaced on another transmission shaft 8, and the gear ratio is 1st speed due to the meshing between the gears 25 and 28, and the 2nd speed is achieved due to the meshing between the gears 26 and 29. At a gear ratio of 3, the meshing between the gears 27 and 30 results in a gear ratio of 3rd gear, and the pawls 31a and 31b
The transmission shafts 7 and 8 are directly connected by the operation of the mesh clutch 31 due to the meshing between the transmission shafts 7 and 8, and the transmission shafts 7 and 8 are selectively interlocked and connected, respectively, at a 4-speed gear ratio.

The parts explained above are of a normal structure, but as shown in Fig. 2-5, an opening 32 is formed in the rear end part of one side wall of the mission case 1. A lid plate 34 is provided which is removably fixed to the opening 32 by a fixture 33 to close the opening 32. And this cover plate 34
A support metal fitting 36 is provided on the inner surface of the lid plate 34 by a fixture 35, and the gear shafts 39a, 40a are rotated by a support plate 38 which is fixed to the support plate 36 by a fixture 37. A freely supported external gear type hydraulic motor 41 is supported with a hydraulic oil supply path 42 and a hydraulic oil discharge path 43 that communicate with the meshing portion of both gears 39 and 40 of the hydraulic motor 41 from one direction and the other direction. It is formed on a metal fitting 36 and mounted on the supporting metal fitting 36. Further, as shown in FIGS. 2 and 4, an intermediate shaft 44 is rotatably supported by the support hardware 36 and parallel to the hollow transmission shaft 22. The diameter gear 45 is
As shown in the figure, one gear shaft 3 of the hydraulic motor 41
It is meshed with a small-diameter gear 46 that is fitted into the gear 9a. A shift gear 47 is further provided on the intermediate shaft 44, as shown in FIG. 2, which is spline-fitted onto the intermediate shaft 44 and can mesh with the large diameter gear 23 at the base end of the hollow transmission shaft 22. , this shift gear 4
7 is selectively slidably displaced on the intermediate shaft 44, and the second
The intermediate shaft 44 and the hollow transmission shaft 22 are meshed with the large-diameter gear 23 as shown by the solid line in the figure, or disengaged from the large-diameter gear 23 as shown by the chain line.
Therefore, between the hydraulic motor 41 and the hollow transmission shaft 22
a clutch 48 that selectively connects and disconnects the interlocking connection between the
is configured. In order to operate the clutch 48 on and off, as shown in FIG.
A clutch lever 50 is attached to this operating shaft 49 outside the transmission case 1, and an operating plate 52 is provided inside the transmission case 1 with a shifter 51 at one end that engages with the shift gear 47.
is mounted so that sliding displacement of the shift gear 47 can be obtained by rotating the clutch lever 50. Between the other end of the actuating plate 52 and the inner surface of the cover plate 34, a positional restraint is provided between the actuating plate 52 and the inner surface of the cover plate 34 so that the shift gear 47 can be released from the clutch 48 at its engaged position and disengaged position by restricting the rotational displacement of the actuating plate 52. Detent means 53 are provided.

Based on the configuration described above, if the clutch 48 is engaged and hydraulic oil is supplied to the hydraulic motor 41 to drive the motor 41 in a rotational manner with the hydraulic clutch type transmission 2 in the neutral state, this hydraulic motor The rotation of 41 is decelerated by gears 46 and 45 and transmitted to intermediate shaft 44, and further decelerated by gears 47 and 23 and transmitted to hollow transmission shaft 22. In the illustrated case, the hydraulic motor 41
The rotational drive causes the mechanical transmission 3 to be in the 1st speed state, that is, the speed change gear 2 on the hollow transmission shaft 22 as described above.
5 and the shift gear 28 on the transmission shaft 8 are engaged with each other, and at this time, the vehicle can move forward at an extremely low speed, that is, creep traveling can be achieved. That is, the illustrated hydraulic motor 41 is used as an alternative to the hydraulic clutch type transmission 2, and is provided in a system separate from the transmission 2 to drive the vehicle in creep mode. In order to drive the motor 41, the following hydraulic circuit is provided in conjunction with a hydraulic oil supply/discharge control circuit for the plurality of hydraulic clutches 18, 19, 20, and 21 in the hydraulic clutch type transmission 2. .

That is, the hydraulic clutch 1 is supplied from the oil tank 54 configured by utilizing the lower part inside the transmission case 1.
A hydraulic pump 55 for supplying hydraulic oil to the hydraulic pumps 8, 19, 20, and 21 is provided as shown in FIG. A switching valve 56 for returning and discharging hydraulic oil from all hydraulic clutches 18, 19, 20, 21 into an oil tank 54, furthermore for each working position F ₁ , F ₂ , F ₃ or R a corresponding hydraulic A switching valve 56 for supplying hydraulic oil from a hydraulic pump 55 to the clutch 18, 19, 20 or 21 at an oil pressure set by a pressure regulating valve 57 is also provided as shown in FIG. ing. As shown in FIG. 6, an oil supply direction switching valve 58 is inserted into the oil discharge circuit of the hydraulic pump 55 at a position before the pressure regulating valve 57 is connected. As shown in the diagram, it is configured as a 3-port, 2-position valve.
One of the two ports on the secondary side is a hydraulic clutch 18
The clutch oil supply circuit 59 guided in the −21 direction is
A motor oil supply circuit 60 guided toward the hydraulic motor 41 is connected to each of the other ports. The lubrication direction switching valve 58 has a clutch lubrication position where it blocks the end of the motor lubrication circuit 60 to connect the hydraulic pump 55 to the clutch lubrication circuit 59, and a clutch lubrication position where it blocks the end of the clutch lubrication circuit 59 and connects the hydraulic pump 55 to the motor lubrication circuit 60. and a motor lubrication position connected to the motor.

When the oil supply direction switching valve 58 is moved to the motor oil supply position to supply hydraulic oil to the hydraulic motor 41 and the motor 41 is rotated to cause the vehicle to creep, the number of rotations of the hydraulic motor 41, and therefore the vehicle In order to change and control the creep running speed of
As shown in the figure, a flow control valve 61 is inserted into the motor oil supply circuit 60. This flow control valve 6
Reference numeral 1 denotes a variable throttle 62 inserted directly into the motor oil supply circuit 60, and a relief valve 64 inserted into a relief circuit 63 branched from the motor oil supply circuit 62 at a stage before the variable throttle 62. The relief valve 64 is configured to be of a pressure compensating type, and includes a relief valve 64 which guides the oil pressure of the motor oil supply circuit 60 on the downstream side of the throttle 62 as back pressure. hydraulic motor 4
1, and thus the creep speed of the vehicle, is changed and controlled by changing and adjusting the degree of opening of the variable throttle 62 in the flow rate control valve 61.

Similarly, as shown in FIG. 6, a relief circuit 6 branched from an oil drain circuit 65 from the hydraulic motor 41
6 has a pressure regulating valve 67 inserted therein, and the oil drain circuit 65 has a dash prevention valve 68 inserted therein as described below. That is, this dart prevention valve 6
8 has a non-blocking position N that allows free drainage of oil from the hydraulic motor 41 without blocking the oil draining circuit 65, and a blocking position B that blocks the oil draining circuit 65. By introducing the hydraulic pressure on the primary side of the hydraulic motor 41 through the hydraulic action circuit 69, it is displaced and energized in the direction of taking the non-blocking position N, and a spring 70 is provided on the other side.
It is displaced and energized in the direction to take the block position B. The force exerted by the spring 70 to displace the valve 68 is:
When the hydraulic motor 41 is in normal operation, the force applied to the valve 68 by the hydraulic pressure on the primary side of the motor 41 is smaller than that, and therefore, the dash prevention valve 68 is always in the non-blocking position N. Take. When the hydraulic motor 41 is externally driven for some reason to act as a hydraulic pump and negative pressure is generated on the primary side of the hydraulic motor 41, the displacement force exerted by the spring 70 is overcome and the dash prevention valve 68 is moved to the blocking position B. It is designed so that it can be automatically displaced to. Therefore, during creep travel, the agricultural tractor is pushed by, for example, a rotary tiller connected to the rear of the agricultural tractor and towed, and the vehicle travels at a speed higher than the creep travel speed set by the flow rate control valve 61. If this occurs, the hydraulic motor 41 will act as a pump, so the dash prevention valve 68 will be moved to the blocking position B, and the oil drain circuit 65 will be blocked, thereby preventing the oil drain from the hydraulic motor 41. This is carried out via the relief circuit 66, and as the oil pressure is immediately increased by the relief valve 67 in the relief circuit 66, the load on the hydraulic motor 41 which is working as a pump increases and the travel system is restricted. Power is applied and speed increase above the set speed is suppressed. When the external driving force such as the pushing action from the rotary tiller is released, the dart prevention valve 68 is automatically returned to the non-blocking position N again by hydraulic action.

Here, the arrangement and specific structure of various members in the hydraulic circuit shown in FIG. 6 will be explained. The hydraulic motor 41 is as described above.
Further, as shown in FIG.
(Fig. 6) is installed in a clutch housing 71 which is housed in the front end. This hydraulic pump 55 is configured as an external gear pump with a pair of spur gears 72 and 73 meshing with each other, and its first gear shaft 72a is connected to a transmission shaft 74 connected to the main clutch 5. It is connected to the transmission shaft 6.

The variable throttle 62 described above is mounted on a valve case 75 disposed on the upper surface of the rear end of the clutch housing 71 as shown in FIGS. , 7, they are respectively housed inside a valve housing 76 disposed on the upper surface of the valve case 75. Among these, first, the oil supply direction switching valve 58 is
As shown in the figure, a spool 78 is provided which is fitted into a laterally extending valve hole 77 formed in a valve housing 76. The valve hole 77 has a pump port 79 connected to the discharge port of the hydraulic pump 55, a clutch port 80 connected to the clutch oil supply circuit 59, and a motor port 81 connected to the motor oil supply circuit 60. are opened at appropriate locations. In the position shown in FIG. 8, the spool 78 blocks the connection between the pump port 79 and the clutch port 80 by the land 78a, and communicates between the pump port 79 and the motor port 81, and conversely, the spool 78 has a fixed length D from the position shown in FIG. When pushed in,
The land 78a blocks the pump port 79 and the motor port 81, and allows the pump port 79 and the clutch port 80 to communicate with each other. Spool 78
is integrally provided with a handle 78b for operation.

As shown in FIG. 1, the variable throttle 62 includes a spool 83 fitted into a valve hole 82 formed in the valve case 75 and extending in the front-rear direction.
2, the motor port 81 of the oil supply direction switching valve 58
A pump port 84 connected to the hydraulic motor 41 and a motor port 85 connected to the hydraulic motor 41 are opened with an appropriate interval between them. A notch groove 83a extending diagonally is formed on the circumferential surface of the spool 83, and by moving the spool 83 back and forth, the pump port 84 and the motor port 8 are connected to each other by the notch groove 83a.
By changing the communication cross-sectional area between 5 and 5, the variable aperture 62
The aperture degree or aperture degree of the lens can be changed and controlled. As shown in FIG. 1 and FIGS. 7 and 8, a support shaft 86 extends laterally along the front side of the valve case 75.
is fixedly installed, and an operating barrel 87 is rotatably disposed on this support shaft 86, and an operating arm 88 mounted from the operating barrel 87 is engaged with the base end of the spool 83. lever 89
is installed, and by rotating the lever 89, the operating tube 8
7 and an operating arm 88 so that the spool 83 can be displaced back and forth. The position of the spool 83 is controlled by controlling the rotation of the operation tube 87 by a disc spring 90 on the support shaft 86.

Next, as shown in FIG. 8, the relief valve 64 has a valve body 92 fitted into a valve hole 91 formed laterally along the valve housing 76, and the valve body 92 is moved in one direction. A compression spring 93 is provided. The valve hole 91 includes a pump port 94 connected to the clutch port 81 of the oil supply direction switching valve 58, a tank port 95 connected to the transmission case 1 which also serves as the oil tank 54, and a variable throttle clutch port 85. The former two ports 94 and 95 are opened on the opposite side where the compression spring 93 is installed, and the last one port 96 is opened on the side where the compression spring 93 is installed. The valve body 92, which is formed in a hollow shape except for the thick part in the middle, has a window hole 92a that communicates the pump port 94 with the hollow part on the front side of the valve body 92, and a window hole 92a that connects the hollow part on the front side of the valve body 92 with the tank port. A window hole 92b that communicates with the valve body 95 and a window hole 92c that communicates the back pressure port 96 with the hollow portion on the back side of the valve body 92 are formed. The valve body 92 has a hydraulic pressure acting on the front side of the valve body 92 from a pump port 94 and a back pressure application port 9.
At a position where the oil pressure acting on the back side of the valve body 92 from 6 and the force of the compression spring 93 acting on the back side are balanced, oil from the pump port 94 is passed through the window hole 92.
a, 92b and the tank port 95. In this case, the pump 55
Fluctuations in the pressure difference before and after the valve body 92 that occur due to variations in rotational speed, etc. are compensated for by increasing or decreasing the amount of oil relief by vibratory back-and-forth movement of the valve body 92 based on the fluctuations.
In the illustrated case, a port 97 communicating with the pump port 84 of the variable throttle 62 is opened in the valve hole 91 on the front side of the valve body 92, and a hollow portion is opened in the valve body 92 on the front side of the valve body 92. A window hole 92d is formed to communicate with the port 97, and the motor port 81 of the oil supply direction switching valve 58 is connected to the pump port 94 of the relief valve 64, the valve body window hole 92a, the inside of the hollow part on the front side of the valve body 92, and the valve body window. Hole 92d and the above port 97
It is connected to the pump port 84 of the variable throttle 62 via. In addition, on the back side of the valve body 92 on the valve body 91,
A motor port 98 connected to the hydraulic motor 41 is opened, and the motor port 98 is connected to the valve body 9.
2. A window hole 92e is formed in the hollow part on the back side to communicate with the motor port 84 of the variable aperture 62.
Back pressure application port 96 of relief valve 64, valve body window hole 92c, inside hollow part on back side of valve body 92, valve body window hole 92
Hydraulic motor 4 via e and motor port 98
It is connected to 1.

Next, as shown in FIGS. 2 and 3, a valve case 99 is fixed to the lid plate 34 with a fixture 100 and mounted on the outer surface of the lid plate 34. 34, as shown in FIG.
Hydraulic oil supply passages 101 and 102 are formed that communicate with the hydraulic oil supply passage 101, and the motor port 98 of the relief valve 76 described above (FIG. 8) is provided at the base end of the hydraulic oil supply passage 101.
Connecting hardware 103 for hydraulic pipes led from is installed. Further, as shown in FIGS. 3 and 4, a valve hole 104 is connected to the middle of the hydraulic oil discharge path 43 of the support metal fitting 36 and opens into the transmission case 1 which also serves as the oil tank 54. The relief valve 67 is arranged using the valve hole 104. That is, the ball 105 that can be brought into close contact with the valve seat formed at the end of the valve hole 104 is placed between the receiving metal fitting 106 that receives the ball 105 and the supporting metal fitting 3.
The relief valve 67 is constructed by a compression spring 108 disposed in the valve hole 104 with both ends received by a pin 107 fixed to the valve 6 and energized to move toward the valve seat.

Further, as shown in FIGS. 2 and 3, a valve hole 109 is formed in the valve case 99 along the vertical direction, and a part of the valve hole 109 is supported through a communication hole 110 formed in the cover plate 34. An inlet port 111 that communicates with the hydraulic oil discharge path 43 of the hardware 36 and an outlet port 114 that communicates with the mission case 1 that also serves as the oil tank 54 through a drain hole 112 in the valve case 99 and a drain hole 113 in the cover plate 34. and,
It has been formed. And the above-mentioned dart prevention valve 6
8 is a valve body 11 inserted into the above-mentioned valve hole 109.
5, and the valve body 115
is the spring 7 disposed in the valve hole 109.
It is energized to move downward by 0, and
By forming an oil hole 69A corresponding to the above-described hydraulic circuit 69 (FIG. 6) in the valve case 99 so as to be connected to the hydraulic oil supply path 101, the hydraulic motor 4
The hydraulic pressure on the primary side is applied to the lower surface to energize it to move upward. An annular groove 115a is formed on the circumferential surface of the valve body 109 to allow communication between the inlet port 111 and the outlet port 114 described above during normal operation of the hydraulic motor 41. In the dart prevention valve 68, when negative pressure is generated on the primary side of the hydraulic motor 41, the valve body 115 moves downward by the force of the spring 70, and the annular groove 115a is removed from the port 111, 114 position and the gap between the two ports 111, 114 is removed. Valve body 115
Since it is blocked by the above-described block position B,

The switching valve 56 and pressure regulating valve 57 shown in FIG.
Since these valves 56 and 57 are common, illustrations and explanations of their specific structures will be omitted, but these valves 56 and 57 are installed in a valve housing 116 installed on the upper surface of the front half of the mission case 1, as shown in FIG. is provided. In FIGS. 1 and 7, reference numeral 117 denotes an oil passage forming plate attached to the front surface of the mission case 1, which is an oil passage forming plate that connects the hydraulic pump 55 to the valve case 75 and the valve housing 116, and the valve housing 116. An oil passage is formed that extends from the inside to the seal housing 118 fitted over the front end of the transmission shaft 7. Hydraulic oil is supplied to and discharged from the hydraulic clutches 18-21 through the seal housing 118 and each hydraulic clutch 18-21.
This is done by connecting the insides of 19, 20, and 21 with an oil passage bored in the transmission shaft 7.

Since the illustrated travel drive device according to the present invention is configured as described above, in normal cases, the oil supply direction switching valve 58 is placed in the clutch oil supply position, and the hydraulic clutch type transmission 2 is connected to the hydraulic clutch type transmission device 2. Even with the mechanical transmission 3, an appropriate traveling speed can be selected to allow the vehicle to travel. At this time, by disengaging the clutch 48, the hydraulic motor 4
1 is prevented from receiving external drive from the hollow transmission shaft 22 side, and problems such as damage to the hydraulic motor 41 caused by external drive of the motor 41 with the oil supply path cut off do not occur. . When the vehicle needs to creep, for example when performing thin slicing work in a field or snow removal work on the road, the refueling direction selector valve 58 is moved to the motor refueling position, the clutch 48 is engaged, and the mechanical transmission is turned on. 3 is meshed between the gears 25 and 28 to shift to the first gear, and the vehicle can be driven creep by the hydraulic motor 41. The vehicle speed during creep running can be controlled steplessly by controlling the degree of opening or constriction of the variable throttle 62 of the flow rate control valve 61 using the control lever 89, and by changing and controlling the supply ratio of hydraulic fluid to the hydraulic motor 41. can be controlled to change. Furthermore, if the vehicle attempts to travel at a speed exceeding the vehicle speed set by the flow rate control valve 61 due to the pushing action of the work equipment, etc., the action of the dart prevention valve 68 prevents such an increase in vehicle speed. is suppressed and the set vehicle speed is maintained. The effects of this invention are as follows.

That is, this invention is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 52-109228.
Like the one in the publication, a structure is adopted in which the vehicle speed is continuously changed by an open-circuit hydraulic transmission, but in particular, a hydraulic pump 5 for the hydraulic clutch type transmission 2 is used.
5 the hydraulic motor 41 of the hydraulic transmission;
The oil supply direction switching valve 58 eliminates the need for a separate hydraulic pump for the hydraulic transmission, and controls the flow rate of oil supplied to the hydraulic motor 41 of the hydraulic transmission. A variable flow rate type flow control valve 61 is provided, and the rotation speed of the hydraulic motor 41 can be changed steplessly by changing the flow rate set in the flow rate control valve 61, making it cheaper than a variable displacement type. Hydraulic transmission hydraulic motor 41
is connected via a clutch 48 to the transmission shaft 22 located on the driven side of the hydraulic clutch type transmission 2 and located on the driving side of the mechanical transmission 3, so that the rotation of the motor 41 is controlled when the hydraulic motor 41 drives the vehicle. is decelerated by the mechanical transmission 3 and transmitted to the wheels or the crawler, so that even if the torque generated by the hydraulic motor 41 is small, the torque is increased by deceleration, so there is no problem in driving the vehicle. This year, hydraulic motor 41
As a result, the cost of the hydraulic transmission can be significantly reduced and the cost increase of the traveling drive device can be suppressed to the utmost.

Further, the present invention uses a variable flow rate control valve 61 to change and control the rotation speed of the hydraulic motor 41, and the flow rate controlled by the flow control valve is stable even when the flow rate is low. Since the low-speed rotation can be significantly reduced by the mechanical transmission 3, it is not necessary to rotate the motor 41 at an extremely low speed, thereby obtaining an extremely stable vehicle speed when the vehicle is driven at low speed by the hydraulic motor 41. .

[Brief explanation of the drawing]

FIG. 1 is a partially omitted longitudinal side view of the main parts of an agricultural tractor equipped with an embodiment of the present invention, and FIG.
The figure is a cross-sectional plan view of a part of the illustrated part;
4 is a longitudinal sectional front view of the part shown in FIG. 3, FIG. 5 is a longitudinal sectional side view of the part shown in FIG. 6 is a circuit diagram showing the hydraulic circuit in the above embodiment, and FIG. 7 is a vertical sectional front view of FIG. 1.
FIG. 8 is an enlarged cross-sectional plan view taken along line - in FIG. 7; DESCRIPTION OF SYMBOLS 1...Mission case, 2...Hydraulic clutch type transmission, 3...Mechanical transmission, 4...Engine, 5...Main clutch, 6...Transmission shaft, 7...
Transmission shaft, 8... Transmission shaft, 18, 19, 20, 21
...Hydraulic clutch, 22...Hollow transmission shaft, 36...
...Support hardware, 41...Hydraulic motor, 44...Intermediate shaft, 45...Large diameter gear, 46...Small diameter gear, 47
...Shift gear, 48...Clutch, 50...Clutch lever, 55...Hydraulic pump, 56...Switching valve, 57...Pressure regulating valve, 58...Lubrication direction switching valve, 59...Clutch oil supply circuit, 60 ... Motor oil supply circuit, 61 ... Flow rate control valve, 62 ... Variable throttle, 63 ... Relief circuit, 64 ... Relief valve, 65 ... Oil drain circuit, 66 ... Relief circuit,
67...Pressure regulating valve.

Claims (1)

[Claims] 1 Hydraulic clutch type transmission device for driving power transmission 2
In a self-propelled working vehicle such as an agricultural tractor, in which a mechanical transmission 3 and a mechanical transmission 3 are connected in series in this order, the plurality of hydraulic clutches 18, 19, 20, 21 in the hydraulic clutch type transmission 2 are provided. On the other hand, a hydraulic motor 41 is provided which is connected to a hydraulic pump 55 for supplying hydraulic oil via an oil supply direction switching valve 58 and a variable flow rate control valve 61, and this hydraulic motor 41 is connected to the hydraulic clutch type transmission. The traveling drive device is characterized in that it is interlocked and connected via a clutch 48 to a transmission shaft 22 located on the driven side of the mechanical transmission 3 and on the driving side of the mechanical transmission 3.