JPH11311267A - Traveling drive transmission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method capable of heightening the durability of hydraulic clutches of main clutch mechanism or forward-reverse switching mechanism while avoiding enlargement of a transmission and cost increase in a traveling drive transmission provided with hydraulic clutch type main clutch mechanism or forward-reverse switching mechanism and hydraulic clutch type hydraulic shift mechanism. SOLUTION: Hydraulic clutch type main clutch mechanism or forward-reverse switching mechanism and hydraulic shift mechanism shifting by the operation of a selected hydraulic clutch out of a plurality of hydraulic clutches are provided being series-connected in this order. When starting a vehicle, working oil pressure to the hydraulic clutches 35, 36 in the main clutch mechanism or forward-reverse switching mechanism is built up to the set oil pressure with the hydraulic shift mechanism left in shift operation. When changing vehicle speed, working oil pressure to the hydraulic clutch in the hydraulic shift mechanism is built up to the set oil pressure while maintaining working oil pressure to the hydraulic clutches 50, 51, 52, 62, 63, 64 in the main clutch mechanism or forward-reverse switching mechanism to the set oil pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a traveling drive transmission.

[0002]

BACKGROUND OF THE INVENTION In a traveling drive transmission of a vehicle, it is necessary to employ a hydraulic clutch type speed change mechanism which facilitates a speed change operation, and to set a hydraulic pressure applied to a hydraulic clutch of the speed change mechanism by a modulation type relief valve. For example, it is well known from Japanese Patent Publication No. 33575/1988. However, in the prior art, when the vehicle is started from a stopped state, the hydraulic clutch of the hydraulic transmission mechanism is engaged through a slip state by using the hydraulic pressure rising characteristic of the modulated relief valve, and the hydraulic clutch is seized. In order to prevent such a situation, all hydraulic clutches that may be engaged when the vehicle starts moving must be configured to have a large heat dissipation capacity.

For the purpose of quickly performing a loader operation requiring frequent forward and backward movements of a vehicle, an easy-to-operate hydraulic clutch type forward / reverse switching device may be provided in front of the mechanical transmission, for example. It is known from Japanese Unexamined Patent Publication No. 8-277802. The forward hydraulic clutch and the reverse hydraulic clutch of such a forward / reverse switching device have a large heat dissipation capacity so as to function also as a main clutch.
At the time of starting the vehicle and at the time of shifting operation of the mechanical transmission, the clutch is temporarily disengaged, and then the clutch is operated to be engaged after a half-clutch state.

[0004] Therefore, when these two technologies are combined to form the forward / reverse switching device and the transmission with a hydraulic clutch type that is easy to operate, a hydraulic clutch having a large heat dissipation capacity is used for each device. Become,
The traveling drive transmission becomes larger and costs rise. In addition, if the hydraulic clutch of the forward / reverse switching device is involved in all of starting and shifting, durability for a long period becomes a problem.

SUMMARY OF THE INVENTION The present invention provides a novel control method that breaks conventional wisdom in a traveling drive transmission in which a hydraulic clutch type main clutch mechanism or a forward / reverse switching mechanism and a hydraulic clutch type speed change mechanism are connected in series in the front and rear directions. Thus, the transmission is prevented from being enlarged and the cost is increased, and the durability of the main clutch mechanism or the forward / reverse switching mechanism is enhanced.

[0006]

SUMMARY OF THE INVENTION A method of controlling a traveling drive transmission according to the present invention includes a hydraulic clutch type main clutch mechanism (8).
And a hydraulic transmission mechanism (11, 14) for performing a shift by the operation of a hydraulic clutch selected from a plurality of hydraulic clutches, which are connected in series in this order and provided when starting the vehicle.
The hydraulic pressure applied to the hydraulic clutch in the main clutch mechanism (8) is increased to the set hydraulic pressure while the hydraulic transmission mechanisms (11, 14) are being shifted, and the main clutch is used to change the vehicle speed. The hydraulic pressure applied to the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is raised to the set hydraulic pressure while the hydraulic pressure applied to the hydraulic clutch in the mechanism (8) is maintained at the set hydraulic pressure.

According to the present invention, the operating hydraulic pressure on the hydraulic clutch in the hydraulic transmission mechanism is maintained while maintaining the operating hydraulic pressure on the hydraulic clutch in the main clutch mechanism at the set hydraulic pressure, that is, maintaining the vehicle in the running state, only when the vehicle speed is changed. To the set oil pressure, and the vehicle should be started by raising the working oil pressure to the hydraulic clutch of the main clutch mechanism to the set oil pressure while keeping the hydraulic transmission mechanism operated. Since the,
The hydraulic clutch in the hydraulic transmission mechanism switches between the hydraulic clutches having a small speed difference before and after the shift only in the vehicle running state, so that the heat radiation capacity is small and the size and cost can be reduced. The torque for starting the vehicle from the stopped state is output from the main clutch mechanism, and only the hydraulic clutch needs to use a clutch having a large heat radiation capacity. From the above, it is possible to avoid an excessive burden on the hydraulic clutch of the main clutch mechanism while minimizing the increase in the size and cost of the hydraulic shift mechanism when increasing the number of hydraulic clutches of the hydraulic transmission mechanism and increasing the number of shift stages. Its durability can be increased.

A method for controlling a traveling drive transmission according to the present invention includes a forward / reverse switching device (8) for switching a vehicle traveling direction by selectively operating a forward hydraulic clutch and a reverse hydraulic clutch, and selecting from a plurality of hydraulic clutches. And a hydraulic transmission mechanism (11, 14) for performing a shift by operating the hydraulic clutch provided in series in this order, and when the vehicle starts, the hydraulic transmission mechanism (11, 14) is provided.
While the shift operation of (14) is being performed, the hydraulic pressure applied to one hydraulic clutch in the forward / reverse switching device (8) is increased to the set hydraulic pressure, and when changing the vehicle speed, the forward / reverse switching device (8) is used. The hydraulic pressure for the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is raised to the set hydraulic pressure while the hydraulic pressure for one hydraulic clutch is maintained at the set hydraulic pressure.

This configuration focuses on the fact that a hydraulic clutch for transmitting power having different rotational directions, such as a forward hydraulic clutch and a reverse hydraulic clutch, having a large heat dissipation capacity is originally used in the forward / reverse switching mechanism. The effect is the same as in the case described above.

In the present invention, the hydraulic transmission mechanism is not involved in starting the vehicle as described above. Therefore, in a preferred embodiment, the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is controlled by a switching valve mechanism having no neutral position. This switching valve mechanism makes the structure of the switching valve extremely simple.

Further, the method of controlling a traveling drive transmission according to the present invention is directed to a hydraulic transmission mechanism (11, 1) that performs gear shifting by operating a hydraulic clutch type main clutch mechanism (8) and a hydraulic clutch selected from a plurality of hydraulic clutches.
4) are connected in series in this order, and when the vehicle speed is changed, the hydraulic transmission mechanism (11, 14) is maintained while maintaining the working oil pressure for the hydraulic clutch in the main clutch mechanism (8) at the set oil pressure. ), The working oil pressure applied to the hydraulic clutch is increased to the set oil pressure.

According to the control method of this configuration, the hydraulic clutch in the hydraulic transmission mechanism is maintained while maintaining the working oil pressure for the hydraulic clutch in the main clutch mechanism at the set oil pressure, that is, while maintaining the vehicle in a running state, only when changing the vehicle speed. The hydraulic clutch in the hydraulic transmission mechanism is switched to the hydraulic clutch with a small difference in speed before and after the shift in the vehicle running state. The capacity is small, small, and low-cost. Therefore, when increasing the number of hydraulic clutches of the hydraulic transmission mechanism to increase the number of gears,
The size and cost of the mechanism can be minimized.

Further, according to the present invention, there is provided a method for controlling a traveling drive transmission, comprising: a forward / reverse switching device (8) for switching a vehicle traveling direction by selectively operating a forward hydraulic clutch and a reverse hydraulic clutch; And a hydraulic transmission mechanism (11, 14) for performing a gear shift by operating a hydraulic clutch provided in this order and connected in series. When changing the vehicle speed, one hydraulic pressure in the forward / reverse switching device (8) is changed. While maintaining the working oil pressure for the clutch at the set oil pressure, the hydraulic transmission mechanism (11, 1) is used.
The hydraulic pressure applied to the hydraulic clutch in 4) is raised to the set hydraulic pressure.

This configuration focuses on the fact that, in the forward / reverse switching mechanism, a hydraulic clutch for transmitting power having different rotational directions, such as a forward hydraulic clutch and a reverse hydraulic clutch, originally has a large heat dissipation capacity. The effect to be achieved is the same as in the case described above.

Other features and advantages of the present invention will be clearly understood from the following description with reference to the accompanying drawings.

[0016]

FIG. 1 shows a transmission mechanism of a tractor equipped with an embodiment of the present invention. The vehicle body is configured by connecting a front housing 1, an intermediate housing 2 and a rear housing 3 back and forth. An engine flywheel 4 is installed at the forefront in the front housing 1, and a driving shaft 6 connected to the flywheel 4 via a buffer spring mechanism 5 in FIG. Part 1a
. From the driving shaft 6 to the traveling drive system and P
The TO drive system is branched, and the traveling drive system is provided with a forward / reverse switching device 8 provided between a driving shaft 6 and an output shaft 7 disposed therebelow. 7
A first hydraulic transmission 11 provided between a first drive shaft 9 connected to the motor and a hollow first driven shaft 10 concentrically disposed on the driving shaft 6, and the driven shaft concentrically disposed on the first driven shaft 10. A second hydraulic transmission 14 is provided between a hollow second drive shaft 12 connected to the first drive shaft 10 and a second driven shaft 13 concentrically disposed on the first drive shaft 9, and is disposed concentrically with the second drive shaft 12. A mechanical transmission device 16 having a hollow counter shaft 15 connected to the second driven shaft 13 in a decelerating manner, wherein the gear stage directly connects the second driven shaft 13 and a propeller shaft 17 arranged concentrically thereto; A mechanical transmission 16 having two gears connected via a counter shaft 15 is provided. A bevel pinion 18 at the rear end of a propeller shaft 17 is provided with a differential device for left and right rear wheels (not shown).
With the large-diameter input bevel gear 19. The PTO drive system allows the transmission shaft 20 connected to the drive shaft 6 to pass through the hollow first driven shaft 10, the second drive shaft 12, and the counter shaft 15,
A PTO clutch 23 between the transmission shafts 21 and 22 concentrically arranged thereon, and a PTO extended to the transmission shaft 23 and the rear of the machine body.
Power is transmitted to the PTO shaft 24 via the PTO transmission 25 between the shaft and the shaft 24.

FIGS. 2 and 3 show the inside of the front housing 1 and the front half of the intermediate housing 2. As clearly shown in these figures, a first bearing frame 27 attached to the housing 1 is provided in the middle of the front housing 1 which is open at the rear end. A second bearing frame 28 attached to the housing 2 is provided at the forefront. Rear ends of the driving shaft 6 and the output shaft 7 and the first drive shaft 9
The front end of the first driven shaft 10 is supported by a first bearing frame 27, and the rear ends of the first drive shaft 9 and the first driven shaft 10, and the second drive shaft 12 and the second driven shaft. The front end of 13 is supported by a second bearing frame 28. Drive shaft 6 and PT
The transmission shaft 20 of the O drive system is connected to the transmission shaft 20 by a coupling 29 in the first bearing frame 27.

As is clearly shown in FIG. 2, the forward / reverse switching device 8 comprises two gears 30, 31 loosely fitted on the driving shaft 6.
And two gears 32, 33 fixedly installed on the output shaft 7, of which the forward gears 30, 32 are directly meshed, and the reverse gears 31, 33 are the first bearing frame. 2
The gear 7 is meshed via an idler gear 34 (FIG. 1) supported by the gear 7. The output shaft 7 has a rear end connected to the first drive shaft 9 via a boss 33 a of the gear 33. The forward / reverse switching device 8 is of a hydraulic type, and
Hydraulic clutch 35 for forward movement provided between gears 30 and 31 above
And a reverse hydraulic clutch 36. Each of the hydraulic clutches 35 and 36 has a plurality of friction elements slidably supported by a clutch cylinder 37 fixedly installed on the driving shaft 6 and boss portions 30 a and 31 a of gears 30 and 31.
A plurality of friction elements, which are slidably supported only, are alternately arranged, and the pistons 35b, 36b urged by the return springs 35a, 36a are moved by hydraulic action to engage the friction elements. It is configured as a well-known friction multi-plate type to be obtained and operated.

In the driving shaft 6, hydraulic clutches 35 and 36 are provided.
Oil passages 38F, 38 for supplying hydraulic oil to the
R and a lubricating oil passage 38L for supplying lubricating oil to the friction element portions of the hydraulic clutches 35 and 36 are formed. These oil passages 38F, 38R, 38L close the annular groove formed on the outer peripheral surface of the driving shaft 6 with the inner wall surface of the driving shaft insertion hole in the supporting wall portion 1a, and the driving shaft 6 and the supporting wall portion 1a.
Oil passages 38F, 38R, 38L in the driving shaft 6 which are communicated with the annular oil chambers 39F, 39R, 39L formed therebetween, and which are rotated by the annular oil chambers 39F, 39R, 39L, are fixed on the support wall. Oil passages 40F, 40R, 40 in 1a
An oil passage rotary joint for connecting to the L is formed.

The hydraulic pump 41 for supplying oil to the hydraulic clutches 35 and 36 is of an internal gear type using the driving shaft 6 as a pump shaft, and is mounted on the front surface of the support wall 1a. The control valve device 42 (FIG. 1) for the forward / reverse switching device 8 is provided with an opening in one side wall of the front housing 1, and extends through the opening into and out of the front housing 1. Although not specifically illustrated, the support wall 1
a, a hydraulic pump 41 and a control valve device 42
The oil passages 40F, 40R, 40L for connecting the oil passages and the control valve device 42 and the annular oil chambers 39F, 39R, 39L are provided. The specific structure of these oil passages, including the specific structure of the control valve device 42, is disclosed in U.S. Pat.
5,599,247.

The first hydraulic transmission 11 will now be described. As clearly shown in FIG. 3, three gears 44, 45 and 46 are loosely mounted on the first drive shaft 9, and the first driven shaft is provided. 1
Three gears 47, 48, and 49 are fixedly mounted on 0, and the corresponding gears are meshed with each other. On the first drive shaft 9, gears 44, 45 and 46 are alternatively provided.
Three hydraulic clutches 50, 51,
52 are provided. Each hydraulic clutch 50, 51, 52
Are the clutch cylinders 53 and 54 fixedly installed on the first drive shaft 9 (the clutch cylinder 53 is a hydraulic clutch 5
It is shared between 0 and 52. ) And gears 44, 45, 46
The bosses 44a, 45a, and 46a alternately support a plurality of friction elements that are alternately arranged and slide freely, and apply hydraulic pressure to the pistons 50b, 51b, and 52b that are urged to move by return springs 50a, 51a, and 52a. The known friction multi-disc type is operated by obtaining the engagement between the friction elements by moving it. The first hydraulic transmission 11 operates the hydraulic clutch 50 and causes the gears 44 and 47 to participate in the transmission of the speed change so that the gear ratio of the first speed is changed. The gear ratio of the second speed can be increased by operating the hydraulic clutch 52 and the gears 46 and 49 can be engaged in the transmission of the gear shift.
Speed ratios are given respectively.

The second hydraulic transmission 14 will be described. Similarly, as shown in FIG. 3, the second drive shaft 12 is connected to the first driven shaft 10 by a coupling 55 in the second bearing frame 28. Are linked. 3 on the second drive shaft 12
Gears 56, 57, 58 are fixedly installed, and three gears 59, 60, 61 are loosely installed on the second driven shaft 13, and the corresponding gears are meshed with each other. . On the second driven shaft 13, three hydraulic clutches 6 for selectively connecting gears 59, 60, 61 to the driven shaft 13 are provided.
2, 63, 64 are provided. Each hydraulic clutch 62, 6
Reference numerals 3 and 64 denote clutch cylinders 65 and 66 fixed on the second driven shaft 13 (the clutch and cylinder 65 are shared by the hydraulic clutches 62 and 63) and gears 59 and 66.
Pistons 62b, 63b, which are urged to move by return springs 62a, 63a, 64a, slidably support a plurality of friction elements alternately arranged on the boss portions 59a, 60a, 61a of the 60, 61, respectively. 64b is a known friction multi-plate type which is operated by moving the hydraulic element 64b by the action of hydraulic pressure to obtain engagement between friction elements. The second hydraulic transmission 14 operates the hydraulic clutch 62 to operate the gear 5.
The gear ratio of the first speed is operated by allowing the gears 6 and 59 to participate in the transmission, and the gear ratio of the second speed is operated by operating the hydraulic clutch 63 and the gears 57 and 60 are engaged in the transmission. By causing the gears 58 and 61 to participate in the transmission of the speed change, a speed change ratio of the third speed is given.

As shown in FIG. 3-6, three hydraulic oil passages 68A, 68B, 68C are formed in the first drive shaft 9 to open toward the pistons 50b, 51b, 52b.
The second driven shaft 13 has three hydraulic oil passages 69A and 69A.
B, 69C to form pistons 62b, 63b, 64c
It is opened toward. Between the first drive shaft 9 and the first bearing frame 27, three annular grooves formed on the outer peripheral surface of the first drive shaft 9 are covered with the inner wall surface of the shaft bearing hole of the first bearing frame 27. The annular oil chambers 70A, 70B, and 70C are formed so as to open the hydraulic oil passages 68A, 68B, and 68C in the oil chambers 70A, 70B, and 70C on the base end side, and the first bearing frame. Hydraulic oil passages 71A, 71B, 71 in the body 27
C is opened to form annular oil chambers 70A, 70B, 70C at a rotary joint of the oil passage. Similarly the second
The second driven shaft 1 is provided between the driven shaft 13 and the second bearing frame 28.
The three annular oil chambers 72 are rotary joints that connect the hydraulic oil passages 69A, 69B, 69C in the third oil passage 3 and the hydraulic oil passages 73A, 73B, 73C in the second bearing frame 28.
A, 72B and 72C are formed. First drive shaft 9
And the second driven shaft 13 are formed with lubricating oil passages 68L and 69L so as to communicate with each other in the second bearing frame 28, and the passages 68L and 69L are formed in the first bearing frame 27. It is connected to the lubricating oil passage 74.

As shown in FIG. 4-7, a thick plate-shaped valve block 77 is attached to the lower part of the outer surface of one side (right side) of the front housing 1 via a plate member 76. The valve block 77 is disposed substantially between the first and second bearing frames 27 and 28 when viewed in the vehicle axial direction. Further, another valve block 77 is provided below the outer surface of one side of the front end of the intermediate housing 2 (right side). The plate member 78 is mounted. On the upper surface of the valve block 77, the hydraulic clutches 50, 51, 5 in the first and second hydraulic transmissions 11, 14 are provided.
Four electromagnetic switching valves 79A, 79B, 79C, 79D for controlling the supply of hydraulic oil to the valves 2 and 62, 63, 64 are mounted, and the respective oil path switching plungers 79a are inserted into the valve block 77. Hydraulic clutches 50, 51, 52 and 6 are located in front of the lower surface of the valve block 77.
An electromagnetic proportional valve 80 for controlling the hydraulic pressure applied to 2, 63, 64 is mounted, and an electromagnetic control valve 81 for controlling oil drainage from the hydraulic clutch is mounted at a lower position on the back. The valve block 77 is also provided with a hydraulic oil supply port 82 and a lubricating oil supply port 83.

From the inside of the valve block 77, the plate member 7
Hydraulic oil passages 84A, 84B, 84C are guided into the inside 6, and an opening 85 is formed in the side wall of the front housing 1. The hydraulic oil passage 71 in the first bearing frame 27
A, 71B, 71C are hydraulic oil passages 84A, 84B, 84
C, pipes 86A and 86 passed through the opening 85
B, 86C. Hydraulic oil passages 87A, 87B, and 87C are provided from inside the valve block 77 to the plate member 76 and the side wall of the front housing 1, and a hydraulic oil passage 88 communicating with these hydraulic oil passages is provided.
A, 88B, 88C are formed in the side wall of the intermediate housing 2 and in the other plate member 78, and the other plate member 7 is formed.
8 has an opening on the inner surface. And the second bearing frame 28
73A, 73B and 73C are hydraulic oil passages 88A and 88, respectively.
B, 88C are connected by pipes 90A, 90B, 90C that have passed through an opening 89 in the side wall of the intermediate housing 2.

The flow direction of the hydraulic oil supplied to the hydraulic oil supply port 82 of the valve block 77 is switched by the electromagnetic switching valve, and the annular oil chambers 70A, 70B or 70C and the annular oil chambers 72A, 72B or 72C. On the other hand, the lubricating oil supply port 83 is connected to an oil passage 91 in the plate member 76 communicating therewith and the pipe 9 connecting the lubricating oil supply passage 74 in the first bearing frame 27.
2, the lubricating oil supply passage 74, and thus the lubricating oil passage 68L in the first drive shaft 9 and the second driven shaft 1
3 is always in communication with the lubricating oil supply passage 69L.

FIG. 8 shows a hydraulic circuit for the hydraulic clutches 35, 36 of the forward / reverse switching device 8, and hydraulic clutches 50, 51, 5 of the first and second hydraulic transmissions 11, 14.
The hydraulic circuit for 2,62,63,64 is shown. Oil is supplied to the former hydraulic circuit by the hydraulic pump 41 and to the latter hydraulic circuit by the hydraulic pump 95 from an oil reservoir 94 provided in the lower part of the vehicle body. As shown in FIG. 1, the latter hydraulic pump 95 is connected so as to be driven by a transmission shaft 21 of a PTO drive system constantly driven by an engine. That is, the lift case 9 supporting the left and right lift arms 96 at the rear of the machine body.
The drive of the hydraulic pump 95 is obtained through a gear train 98 including a gear supported by the case 97. An oil filter 99 shared by the hydraulic pump 41 and the hydraulic pump 95 is provided in the oil reservoir 94.

The hydraulic clutch 35 of the forward / reverse switching device 8
The hydraulic circuit for 36, as shown in FIG.
An oil passage shutoff valve 103 and a pressure reducing valve 10
4 and the directional control valve 105 are connected in series in this order. A line filter 106 and a bypass valve 107 are inserted in the oil supply passage 102 while being connected in parallel with each other. When the line filter 106 is clogged and the hydraulic pressure on the upstream side is increased, the bypass valve 107 performs a relief operation to secure a necessary oil supply amount.
The oil pressure in the oil supply passage 102 is set by a main relief valve 108, and on the secondary side of the main relief valve 108, lubricating oil set by the low-pressure relief valve 109 is directed toward the hydraulic clutches 35 and 36. An oil supply oil passage 110 is connected.

The oil passage cutoff valve 103 has a cutoff position I for cutting off the end of the oil supply passage 102 and an open position II for connecting the oil supply passage 102 to a connection oil passage 112 between the oil passage cutoff valve 103 and the pressure reducing valve 104. In the shut-off position I, the connection oil passage 112 is connected to the oil reservoir 94, and the oil is drained from the connection oil passage 102. The pressure reducing valve 104 controls the oil pressure of the oil passage 113 guided to the direction switching valve 105 to reduce the pressure.
2 is connected to the oil passage 113 without substantially reducing the pressure, and a depressurizing position is where the connecting oil passage 112 is variably connected to the oil passage 113 and connected to the oil passage 113 to variably reduce the oil pressure of the oil passage 113. B and drain oil from oil passage 113 to
13 and an unload position C for unloading the hydraulic pressure. The directional control valve 105 includes two hydraulic clutches 35, 3
Neutral position N for turning off 6, hydraulic clutch 3 for forward movement
5 is provided with a forward action position F in which the engagement state is established, and a reverse action position R in which the reverse hydraulic clutch 36 is engaged. A well-known modulation type relief valve 114 for increasing the oil pressure is provided in connection with the connection oil passage 112, and the oil chamber behind the control piston 114b which receives the base end of the oil pressure setting spring 114a in the relief valve 114 has a direction. The oil is drained through the switching valve 105 to the oil reservoir 94 so that the oil is drained quickly at the neutral position N of the switching valve 105. The modulation type relief valve 114 is a directional control valve 10.
When the piston 5 is moved to the operation position F or R, the spring 114a is gradually compressed by gradually moving the piston 114b by the oil gradually flowing behind the control piston 114b from the connection oil passage 112 via the throttle 114c to compress the connection oil. Road 1
The hydraulic pressure of No. 12 is gradually increased to a predetermined value. The direction switching valve 105 is displaced by a forward / reverse switching lever 115.

The pressure reducing valve 104 is operated by a pedal 117, and is provided with a cylinder mechanism 118 for mechanically moving the oil passage shutoff valve 103 from a shutoff position I to an open position II in conjunction with the operation of the pressure reducing valve. Once the oil passage shutoff valve 103 is moved to the open position II, the cylinder mechanism 118 is actuated by the oil pressure of the connection oil passage 112 via the shutoff valve 103 even if the pedal 117 is returned to the original position. Valve 1
03 is held at the same open position II. When the pedal 117 is greatly depressed from the stop state of the vehicle, the pressure reducing valve 104 is moved to the unload position C, and at the same time, the oil passage shutoff valve 103 is moved to the open position II. After that, the pedal 117 is gradually released to release the pressure reducing valve 104. By returning to the non-operation position A via the pressure reduction operation position B, the vehicle gradually starts. In the running state of the vehicle, the pedal 117 is arbitrarily depressed to obtain an arbitrary depressurized state by the pressure reducing valve 104, and the slip engagement of the hydraulic clutch 35 or 36 is obtained, so that the vehicle can run at low speed.

Similarly, as shown in FIG. 8, the secondary side oil passage of the modulation type relief valve 114 is
Has been joined to. The lubricating oil supply oil passage 110 has an on-off valve 1
19, the on-off valve 119 is connected to the oil passage 113
Is used as a pilot pressure, and is released only in a state where the oil pressure is established in the oil passage 113 to guide the lubricating oil toward the hydraulic clutches 35 and 36. On the downstream side of the on-off valve 119, the lubricating oil supply oil passage 110
The flow control valves 120F and 120R are connected to the forward hydraulic clutch 35 and the reverse hydraulic clutch 36, respectively. These flow control valves 120F, 120R are configured using the hydraulic clutches 35, 36 themselves, but will not be described in detail here. In any case, the flow control valve 120
F, 120R are hydraulic clutches 35 or 36 in the engaged state.
Only so that a sufficient amount of lubricating oil is supplied.
It is configured.

Referring to FIG. 8, the hydraulic circuit of the first and second hydraulic transmissions 11 and 14 will be described. The hydraulic clutches 50, 51 of the first and second hydraulic transmissions 11, 14 are supplied to the oil supply passage, to which oil is supplied from the oil passage 122 leading to the oil reservoir 94 by the hydraulic pump 95 and the oil pressure is set by the main relief valve 123. , 52, 62, 63, and 64, and is provided with an oil supply passage 124 for supplying hydraulic oil in the directions. A line filter 125 and a bypass valve 126 are provided in the oil passage 122.
And are inserted in parallel with each other. The bypass valve 126 functions similarly to the bypass valve 107. On the secondary side of the main relief valve 123, a low-pressure relief valve 127 is provided.
The hydraulic lubricating oil set by the hydraulic clutches 50 and 5
A lubricating oil supply oil passage 128 leading to the directions 1, 52, 62, 63, 64 is connected.

An electromagnetic proportional valve 80 is inserted in the oil supply passage 124. In response to a command given as a current, the electromagnetic proportional valve 80 is displaced from the illustrated non-operating position N for draining oil from the oil supply passage 124 on the downstream side of the valve 80 to the operating position I, and the oil supply passage according to the current value. By controlling the flow rate of the oil flowing through the valve 124, the oil pressure in the oil supply passage 124 on the downstream side of the valve 80 is gradually raised to a predetermined value.
The oil supply passage 124 is branched into two oil supply passages 124a and 124b on the downstream side of the electromagnetic proportional valve 80, and the oil supply passage 124a is connected to three of the first hydraulic transmission 11 via two electromagnetic switching valves 79A and 79B. Are connected to two hydraulic switching valves 79C, 79D.
Are connected to three hydraulic clutches 62, 63, 64 of the second hydraulic transmission 14. Each electromagnetic switching valve 79
A, 79B, 79C, and 79D are provided with a single oil drain 129 connected via a check valve.
An electromagnetic control valve 81 for oil drainage control is inserted into the oil pump. The electromagnetic control valve 81 has a position A for discharging the oil from the oil discharge passage 129 to the oil sump 94 without being throttled, and a position B which is moved by the excitation of the solenoid and which restricts the oil discharge by the throttle 81a. Have.

Each of the electromagnetic switching valves 79A, 79B, 79C, 7
9D is a four-port, two-position valve having no neutral position.
From position II to position II. The oil supply passage 124a is connected to the electromagnetic switching valve 79A, and the electromagnetic switching valve 79A is connected to the hydraulic clutch 50 and the electromagnetic switching valve 79B, and the latter electromagnetic switching valve 79B is connected to the hydraulic clutches 51 and 52. ing. Similarly, the oil supply passage 124b is connected to an electromagnetic switching valve 79C, and the electromagnetic switching valve 79C is connected to the hydraulic clutch 62 and the electromagnetic switching valve 79D, and the latter electromagnetic switching valve 79D is connected to the hydraulic clutches 63 and 64. Connected. Solenoid switching valves 79A, 79B, 79C,
The relationship between the position 79D and the two clutches engaged by the hydraulic clutches 50, 51, 52 of the first hydraulic transmission II and the hydraulic clutches 62, 63, 64 of the second hydraulic transmission 14 is as follows. , As shown in Table 1.

[Table 1]

The lubricating oil supply oil passage 128 is connected to the first oil supply passage 128 shown in FIG.
Lubricating oil passages 68L in the drive shaft 9 and the second driven shaft 13
The six hydraulic clutches 50, 51,
Lubricating oil is supplied to the friction element portions 52, 62, 63, and 64.

First and second hydraulic transmissions 11 and 14
The electromagnetic switching valves 79A, 79B, 79C, 79D are operated by a main transmission lever 130 as shown in FIG. A rotary switch R having a movable contact Sa attached to a cylindrical portion 130a that is rotationally displaced integrally with the main speed change lever 130.
S is provided. Nine S1, S2, S3, and S4 fixed contacts of the rotary switch RS correspond to the nine-speed shift obtained by the combination of the first hydraulic transmission 11 and the second hydraulic transmission 14. , S5, S6, S7,
S8 and S9 are provided. A controller is provided connected to the rotary switch RS. The controller includes a shift-up / shift-down determination unit 131, an excitation control unit 132a for the electromagnetic switching valves 79A and 79B, and an excitation control for the electromagnetic switching valves 79C and 79D. A section 132b, an excitation control section 132c of the electromagnetic proportional valve 80, and an excitation control section 132d of the electromagnetic control valve 81 are provided. The determination unit 131 determines which shift speed has been shifted up or down to which other shift speed, and outputs a signal corresponding to the determination result to the excitation magnetization control units 132a, 132b, 132c, and 132d.
Output to The excitation magnetization control units 132a and 132b perform excitation magnetization control of the electromagnetic switching valves 79A to 79D corresponding to the speed change operation. The excitation magnetization control unit 132c gives a command signal to the electromagnetic proportional valve 80 so that a predetermined startup characteristic of the clutch operating oil pressure is obtained according to the selected shift speed. The exciter magnetizing control unit 132d temporarily displaces the electromagnetic control valve 81 for oil drainage control from the position A to the position B at the time of a shift operation so that the oil pressure from the hydraulic clutch before the shift is obtained so as to obtain a predetermined oil pressure drop characteristic. Restrict oil flow.

The other parts will be described briefly.
As shown in the figure, the counter shaft 15 of the mechanical transmission 16 is
The gears 135 and 136 are connected to the second driven shaft 13 by reduction. The other two gears 13 on the counter shaft 15
7, 138 are fixedly installed, and a gear 140 connected to a small-diameter gear 137 via a gear reduction mechanism 139 is provided outside the counter shaft 15. A shift gear 141 that can be selectively engaged with the gear 140 is provided on the propeller shaft 17 so as to be slidable only.
The gear 142 meshed with the gear 138 is loosely installed, and the propeller shaft 17 is further connected to the second hydraulic transmission 14.
The clutch hardware 143 that can be displaced between a position directly connected to the second driven shaft 13 and a position connected to the gear 142 with the propeller shaft 17 is provided. As described above, the mechanical transmission device 16 achieves the first gear ratio (creep speed) by meshing the shift gear 141 with the gear 140, and the second gear ratio by coupling the gear 142 to the propeller shaft 17 by the clutch hardware 143. The gear ratio of the clutch hardware 14
3, the propeller shaft 17 is directly connected to the second driven shaft 13 so as to selectively obtain the third gear ratio. In FIG. 1, 144 is a gear for taking out front wheel driving force fixedly installed on the propeller shaft 17,
A pulley 145 is fixed on the propeller shaft 17 and is used as a brake target of a parking brake (not shown).

Similarly, as shown in FIG. 1, the PTO clutch 23 is configured as a hydraulic clutch. The P
The TO transmission 25 is provided with the clutch hardware 14 of the PTO shaft 24.
7 is used to perform three-speed shifting.

FIG. 10 shows controllers 131 and 132a-
The control mode of the hydraulic pressure by 132d is schematically shown. The controller controls the electromagnetic proportional valve 80 to apply the clutch operating oil pressure P to the time t after the shift, for example, according to the curve C1, C2 or Make them stand up like C3. On the other hand, the controller is an electromagnetic control valve 81
Then, the hydraulic pressure P applied to the hydraulic clutch is reduced over time, for example, as shown by a curve Cd, by limiting the flow rate of the drained oil from the hydraulic clutch before the shift. The hydraulic clutch before the shift is disengaged through a slip state due to a decrease in the working oil pressure, and the hydraulic clutch after the shift is engaged through a slip state due to a rise in the working oil pressure. The reduction characteristic and the increase characteristic of the hydraulic pressure are selected according to whether the shift is up or down so that a smooth change in vehicle speed can be obtained.

As described above, the driving mode of the traveling drive transmission is controlled by the first and second vehicle starting operations.
The hydraulic pressure applied to the hydraulic clutch 35 or 36 of the forward / reverse switching device 8 is raised in a rising manner determined by the modulating type relief valve 114 while the hydraulic transmissions 11 and 14 are being shifted. Or 36 is engaged through a slip state. When the vehicle is started for the first time after the engine is started, it is necessary to move the pressure reducing valve 104 to the unload position C by depressing the pedal 117 and simultaneously move the oil passage shutoff valve 103 to the open position II as described above. . When changing the vehicle speed, the hydraulic clutch 35 of the forward / reverse switching device 8 is used.
Alternatively, the operation is performed by operating the electromagnetic switching valves 79A to 79D using the main transmission lever 130 while maintaining the working oil pressure for 36. The forward / reverse switching device 8 is a mere main clutch, that is, 1
The same control is performed in the case where the vehicle is replaced with one having only one hydraulic clutch.

FIGS. 11 and 12 show a second embodiment. In the present embodiment, as shown in FIG.
Is configured to have a neutral position N. The direction switching valve 105 of the forward / reverse switching device 8 is configured as an electromagnetic valve. And while adding a fixed contact S ₀ corresponding to the neutral position N of the electromagnetic switching valve 79A as the rotary switch RS shown in FIG. 12, provided with another rotary switch RS 'to be operated by the forward-reverse switching lever 115, the Rotary switch RS '
Fixed contacts SF, SN, SR corresponding to three positions of the forward / reverse switching lever 115 are provided. The shift-up / shift-down determination unit 131 moves the electromagnetic directional control valve 105 to the position F, N or R via the excitation magnetization control unit 132e in addition to the rotary switch RS in accordance with the operating position of the valve.
The neutral position N is detected by the
At the same time as the electromagnetic switching valve 79A is moved to the position N via 32a, the electromagnetic switching valve 105 is controlled via the excitation magnetizing control unit 132e regardless of the position of the forward / reverse switching lever 230,
It is configured to move to a position N.

Therefore, according to the second embodiment, when the electromagnetic switching valve 79A is operated to the neutral position N by the main shift lever 130, the electromagnetic direction switching valve 105 is neutralized regardless of the position of the forward / reverse switching lever 115. Moved to position N and the vehicle stops. Thereafter, when the main shift lever 130 is moved to the operating position I or II, the operating hydraulic pressure of the hydraulic clutch 35 or 36 of the forward / reverse switching device 8 is increased at the speed determined by the modulation type relief valve 114, and the vehicle is moved. Starts. That is, also in the second embodiment, the vehicle starts moving,
It is obtained by raising the working oil pressure of the forward / reverse switching device 8 to the hydraulic clutch up to the set oil pressure. Solenoid switching valve 79
Although the provision of the neutral position N at A is disadvantageous in terms of complicating the structure, the vehicle is stopped by placing the main transmission lever 130 in the neutral position N and setting the transmission in the neutral state, so that resistance to operation is obtained. There is no feeling.

In the second embodiment, as shown in FIG.
A second switching valve 201 connected in parallel to the first switching valve 200 connected in series to the electromagnetic proportional valve 80 is provided. The first switching valve 200 is normally in a position from a position A where the oil supply passage 124 is opened to a position B to be closed, and the second switching valve 201 is a position in which the circuit 202 bypassing the oil supply passage 124 is opened from a position A which is closed. B is moved by operating the common handle 203. This is in preparation for a failure of the electric system. At that time, the electromagnetic switching valves 79A and 79B and 79C and 79D are not excited, and the vehicle can run in the first speed state. However, the electromagnetic proportional valve 81 may be in the position N depending on the failure of the electric system.
And the hydraulic pressure is not established in the branch passages 124a and 124b. Therefore, the first and second switching valves 200, 201
When the electric system fails, the switching valves 200 and 201 are moved to the position B, whereby the hydraulic pressure set by the main relief valve 123 is changed to the hydraulic clutches 50 and 62.
Can be acted upon. That is, when the electric system fails, the first and second hydraulic transmissions 11 and 14 are set to the first speed state so that the vehicle can travel to a predetermined location. This consideration is also made in the above-described embodiment, and as shown in FIG.
05 is attached to the electromagnetic proportional valve 80.

FIGS. 13 and 14 show a third embodiment. In the present embodiment, as shown in FIG.
Although -79D does not have a neutral position, the direction switching valve 105 of the forward / reverse switching device 8 is configured as an electromagnetic valve. And while providing the same fixed contacts S ₀ to the rotary switch RS, is provided with the same other rotary switch RS '. And shift up / shift down determination unit 1
When the rotary switch RS is operated to the position N in the same manner as described above, the electromagnetic direction switching valve 105 is moved to the position N via the excitation magnetizing control unit 132e regardless of the position of the forward / reverse switching lever 115. It is configured to transfer. Therefore, according to the third embodiment, when the main shift lever 130 is operated to the position N, the electromagnetic directional control valve 105 is moved to the neutral position N regardless of the position of the forward / reverse switching lever 115, and the vehicle Stops. After that, the main shift lever 13
If 0 is moved to the operation position I or II, the operation oil pressure of the hydraulic clutch 35 or 36 of the forward / reverse switching device 8 is increased at the speed determined by the modulation type relief valve 114, and the vehicle starts. This embodiment is an example in which a virtual neutral position N is provided on the main shift lever 130 and the vehicle is stopped at this position.

In the illustrated tractor, after the engine is started, once the pedal 117 shown in FIG. 8 is depressed greatly, the oil passage shutoff valve 103 is moved to the open position, and hydraulic oil is supplied to the hydraulic clutches 35 and 36 of the forward / reverse switching device 8. If the state is not obtained, it is impossible to start the vehicle. After that, the pedal 117 is gradually released to gradually increase the clutch operating oil pressure by the pressure reducing valve 104, and the hydraulic clutch 35 or 36 is moved through the slip state. Engagement provides a gradual start of the vehicle. The forward / reverse switching device 8 can be used as a main clutch by this operation or by the gradually increasing oil pressure by the modulated relief valve 114. The shift operation of the first and second hydraulic transmissions 11 and 14 is performed while the forward / reverse switching device 8 is operated, and the mechanical transmission 16 is set in advance to a gear corresponding to the traveling conditions of the vehicle. However, if necessary, the direction change valve 105 is operated to the neutral position N by the forward / reverse switching lever 115 or the pressure reducing valve 104 is operated to the unload position C by the pedal 117, and the hydraulic clutch 35 of the forward / reverse switching device 8 is operated. , 36, the shift operation can be performed even while the vehicle is running. The vehicle can be stopped without shock by depressing the pedal 117 to bring the pressure reducing valve 104 to the pressure reducing operation position B and then to the hydraulic unloading position C.

The forward / reverse switching device 8, which is also used as a main clutch, controls large torque fluctuations when the vehicle starts moving.
6 is used to make the vehicle run at a low speed by slipping, but since the lubrication systems of the hydraulic clutches 35 and 36 are provided independently, wear of the friction element is sufficiently suppressed. Since the hydraulic clutches 35, 36 are disposed on the upper driving shaft 6 in the forward / reverse switching device 8, the clutches 35, 36 are not immersed in the oil contained in the vehicle body, and the friction elements Drag torque that can be transmitted by the motor is reduced. On the other hand, the hydraulic clutch 5 of the first and second hydraulic transmissions 11 and 14
0, 51, 52 and 62, 63, 64 correspond to the lower first drive shaft 9 and the second driven shaft 13 in these transmissions.
By being arranged on the upper side, it is immersed in oil in the vehicle body to promote cooling.

[Brief description of the drawings]

FIG. 1 is a schematic partially developed longitudinal side view showing a transmission mechanism provided in a tractor equipped with an embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a front half of a front housing of the tractor shown in FIG. 1;

3 is a vertical sectional side view showing a rear half of a front housing and a front half of an intermediate housing of the tractor shown in FIG. 1;

FIG. 4 is a sectional view taken substantially along the line IV-IV in FIG. 3;

FIG. 5 is a sectional view taken substantially along the line VV of FIG. 3;

6 is a cross-sectional plan view showing a part of the tractor shown in FIG.

FIG. 7 is a longitudinal sectional side view showing a part of the tractor shown in FIG. 1;

FIG. 8 is a circuit diagram showing a hydraulic circuit for the forward / reverse switching device and first and second hydraulic transmissions shown in FIGS.

FIG. 9 is a block diagram showing a controller for the first and second hydraulic transmissions shown in FIGS. 1 and 3;

FIG. 10 is a schematic graph illustrating a control mode of a hydraulic pressure by the controller shown in FIG. 9;

FIG. 11 is a circuit diagram showing a second embodiment.

FIG. 12 is a block diagram illustrating a controller according to a second embodiment.

FIG. 13 is a circuit diagram showing a third embodiment.

FIG. 14 is a block diagram illustrating a controller according to a third embodiment.

[Explanation of symbols]

Reference Signs List 6 Drive shaft 7 Output shaft 8 Forward / reverse switching device 9 First drive shaft 10 First driven shaft 11 First hydraulic transmission 12 Second drive shaft 13 Second driven shaft 14 Second hydraulic transmission 30, 31 Gears 32, 33 Gears 35 Forward hydraulic clutch 36 Reverse hydraulic clutch 44, 45, 46 Gears 47, 48, 49 Gears 50, 51, 52 Hydraulic clutches 56, 57, 58 Gears 59, 60, 61 Gears 62, 63, 64 Hydraulic clutch 79A, 79B, 79C, 79D Solenoid switching valve 80 Solenoid proportional valve 81 Solenoid control valve 103 Oil passage cutoff valve 104 Pressure reducing valve 105 Directional switching valve 114 Modulated relief valve 115 Forward / reverse switching lever 130 Main shift lever 131 Shift Up / shift down determination unit 132a, 132b, 132c, 132d Solenoid valve control unit

Claims (5)

[Claims] A main clutch mechanism of a hydraulic clutch type (8).
And a hydraulic transmission mechanism (11, 14) for performing a shift by operation of a hydraulic clutch selected from a plurality of hydraulic clutches, which are connected in series in this order, and when the vehicle starts, the hydraulic transmission mechanism (11, 14) is provided. 11, 14)
The hydraulic pressure applied to the hydraulic clutch in the main clutch mechanism (8) is increased to the set hydraulic pressure while the gearshift operation is performed, and when the vehicle speed is changed, the hydraulic pressure applied to the hydraulic clutch in the main clutch mechanism (8) is changed. And controlling the hydraulic pressure applied to the hydraulic clutch in the hydraulic transmission mechanism (11, 14) to the set hydraulic pressure while maintaining the hydraulic pressure at the set hydraulic pressure. 2. A forward / reverse switching device (8) for switching the traveling direction of a vehicle by selectively operating a forward hydraulic clutch and a reverse hydraulic clutch, and performing a shift by operating a hydraulic clutch selected from a plurality of hydraulic clutches. And a hydraulic transmission mechanism (11, 14) connected in series in this order and provided when the vehicle starts moving.
The hydraulic pressure applied to one hydraulic clutch in the forward / reverse switching device (8) is increased to the set hydraulic pressure while the speed change operation is being performed, and when the vehicle speed is changed, one of the forward / reverse switching device (8) is used. A hydraulic pressure applied to the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is increased to the set hydraulic pressure while the hydraulic pressure applied to the hydraulic clutch is maintained at the set hydraulic pressure. 3. The traveling drive transmission control method according to claim 1, wherein the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is controlled by a switching valve mechanism having no neutral position. 4. A hydraulic clutch type main clutch mechanism (8).
And a hydraulic transmission mechanism (11, 14) that performs gear shifting by operation of a hydraulic clutch selected from a plurality of hydraulic clutches, which are connected in series in this order, and when changing the vehicle speed, the main clutch mechanism ( 8) The traveling drive transmission control characterized in that the hydraulic pressure applied to the hydraulic clutch in the hydraulic transmission mechanism (11, 14) is increased to the set hydraulic pressure while the hydraulic pressure applied to the hydraulic clutch in (8) is maintained at the set hydraulic pressure. Method. 5. A forward / reverse switching device (8) for switching a vehicle traveling direction by selectively operating a forward hydraulic clutch and a reverse hydraulic clutch, and performing a shift by operating a hydraulic clutch selected from a plurality of hydraulic clutches. A hydraulic transmission mechanism (11, 14) is connected in series in this order, and when changing the vehicle speed, the hydraulic pressure applied to one hydraulic clutch in the forward / reverse switching device (8) is maintained at the set hydraulic pressure. A method for controlling a traveling drive transmission, wherein the hydraulic pressure applied to a hydraulic clutch in the hydraulic transmission mechanism (11, 14) is raised to the set hydraulic pressure.