JP5023693B2 - Hydraulic drive vehicle transmission - Google Patents

Description

  The present invention relates to a transmission transmission using a hydraulic continuously variable transmission used in a hydraulically driven vehicle such as a tractor.

In a hydraulically driven vehicle, a hydraulic continuously variable transmission and a gear transmission are incorporated in a transmission case, and a desired operation is performed by appropriately combining the hydraulic transmission and the gear transmission with a shift lever or the like provided near the operation seat. I am trying to run at a running speed of.
JP 2002-250437 A

  The hydraulic continuously variable transmission of the hydraulic drive vehicle is housed in a transmission case made up of a plurality of hollow cases, and the shaft constituting the link mechanism connected to the trunnion shaft (transmission shaft) of the hydraulic continuously variable transmission is the transmission case. The trunnion shaft is projected from the side portion to the outside, and the trunnion shaft is rotated by a hydraulic cylinder connected by a link mechanism to change speed. For this reason, when maintaining the link mechanism or the like, it is necessary to drain the oil in the transmission case, and the maintenance is very troublesome. Further, since the shaft constituting the link mechanism protrudes from the side of the transmission case to the outside of the side, if a malfunction occurs in the shaft seal, oil leakage may occur. In particular, since a large force is applied to the trunnion shaft, a gap is generated in the shaft support portion, and oil leakage is likely to occur.

  Therefore, an object of the present invention is to provide a configuration in which oil leakage does not easily occur even when a gap is generated in a trunnion shaft support portion of a hydraulic continuously variable transmission.

The problems of the present invention are solved by the following means.
According to the first aspect of the present invention, when the hydraulic continuously variable transmission 27 is disposed in the transmission case 23, the trunnion shaft 97 of the hydraulic continuously variable transmission 27 is disposed so as to face upward. The linked link mechanism R is configured to protrude upward from the transmission case 23, and a neutral holding mechanism 98 that holds the neutral position of the trunnion shaft 97 is provided in the transmission case 23. The shift shaft 102 to be connected protrudes from the transmission case 23, and the protrusion is connected to the hydraulic cylinder 36 for operation attached to the outside of the transmission case 23.
The shift position of the main shift lever 11 is detected by the shift sensor 95 and the hydraulic cylinder 36 is operated to turn the trunnion shaft 97 to the target speed. The movement of the trunnion shaft 97 is provided in the middle of the link mechanism R. The shift angle sensor 106 detects the rotation amount of the trunnion shaft 97 and performs feedback control so that the rotation amount becomes the target position.
Further, when the temporary neutral position of the hydraulic cylinder 36 is stored in the control device 96, the movement of the rod 110 of the hydraulic cylinder 36 is limited to approximately half. .

With this configuration, the trunnion shaft 97 is rotated in the transmission case 23 and the inclination of the movable swash plate of the hydraulic continuously variable transmission 27 is changed to change the speed steplessly. Further, the trunnion shaft 97 is shifted from above the mission case 23 via the link mechanism R. The neutral holding mechanism 98 operates without being damaged by muddy water or stones. Further, the shift position of the main shift lever 11 is detected by the shift sensor 95 and the hydraulic cylinder 36 is operated to rotate the trunnion shaft 97 so as to reach the target speed.
The movement of the trunnion shaft 97 is detected by a shift angle sensor 106 provided in the middle of the link mechanism R, and feedback control is performed so that the rotation amount of the trunnion shaft 97 becomes a target position.
When the temporary neutral position of the hydraulic cylinder 36 is stored in the control device 96, the movement of the rod 110 of the hydraulic cylinder 36 is limited to approximately half.

The invention according to claim 2 is provided with an automatic speed control switch for automatically reducing the speed when the vehicle makes a turn. When the automatic speed control switch is turned on to raise the work implement, the main speed change lever 11 2. The transmission for a hydraulically driven vehicle according to claim 1 , wherein the speed is reduced to a predetermined ratio of the indicated speed .

With this configuration, when the work implement is raised with the automatic speed control switch turned on, the speed is reduced to a predetermined ratio of the instruction speed of the main transmission lever 11.

According to the first aspect of the invention, since the hydraulic continuously variable transmission 27 is housed in the mission case 23, even if oil leaks from the support portion of the trunnion shaft 97, it leaks to the outside of the mission case 23. There is nothing. Further, when maintaining the link mechanism R or the like, it is not necessary to drain the oil in the mission case 23, and the maintenance becomes easy. Further, since the shaft constituting the link mechanism R protrudes upward from the upper part of the mission case 23, even if a malfunction occurs in the shaft seal, the oil in the mission case 23 does not leak to the outside. . Further, it is possible to prevent the neutral holding mechanism 98 of the trunnion shaft 97 that needs to be adjusted from being damaged by muddy water, stones, or the like. Further, the rotation of the trunnion shaft 97 to the target position becomes accurate. In addition, when the temporary neutral position of the hydraulic cylinder 36 is stored in the control device 96, the movement of the rod 110 of the hydraulic cylinder 36 is limited to approximately half, so that the moving speed during assembly work is limited and safety is ensured. .

According to the invention described in claim 2, in addition to the effect of claim 1, the vehicle can easily and safely turn.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 and FIG. 2 are drawings showing the entirety of a tractor which is an embodiment of a hydraulically driven vehicle. A driving seat 1 in which an engine 24 is mounted on the front side of the fuselage and an operator sits on the rear side. 2, a steering handle 3 is erected at an intermediate position between the front and rear, and front and rear wheels 4 and 5 are attached to the bottom.

  A forward / reverse lever 6 and an accelerator lever 7 project laterally on the left and right of the steering handle 3, and a clutch pedal 9 is provided on the left side of the steering handle 3 on the floor step 8 and an accelerator pedal 10 is provided on the right side of the steering handle 3. Is standing.

  On the left side of the cockpit 2, a main transmission lever 11 that shifts from 1st to 8th speed, a sub-transmission lever 12 that shifts to low, middle, and high three speeds, and a cultivator that is attached to the rear of the tractor The PTO clutch lever 13 for continually driving the PTO output shaft 41 is erected.

  On the right side of the cockpit 2, an automatic tilling lever 15 and a position lever 14 for adjusting the height of the work implement are erected. 16a is a switch that raises the working machine at the rear of the tractor to the right, and 16b is a switch that lowers the working machine at the rear of the tractor to the right.

Reference numeral 18 denotes an automatic horizontal switch for automatically leveling the work machine at the rear of the tractor, and 17 denotes a backup switch for automatically raising the work machine at the rear when the tractor moves backward.
The transmission case 23 which transmits the engine output of the prime mover 1 to the front and rear wheels 4 and 5 and the PTO output shaft 41 by increasing and decreasing the speed also functions as a main frame of the fuselage below the floor step 8 and the cockpit 2. This is a configuration in which four hollow cases of a case 19, a connecting case 20, an intermediate case 21, and a rear case 22 are integrally connected.

Next, the power transmission mechanism in the mission case 23 will be described with reference to FIG.
The rotation of the output shaft of the engine 24 is transmitted to the input shaft 35 of the transmission case 23 via the main clutch 34 which is intermittently connected by the clutch pedal 9. The rotation of the input shaft 35 is accelerated by the speed increasing gears 25 and 26 and transmitted to the input shaft 28 of the hydraulic continuously variable transmission 27.

  The hydraulic continuously variable transmission 27 includes a variable displacement hydraulic pump 29 and a fixed displacement hydraulic motor 31, and changes the rotation of the hydraulic motor 31 by changing the inclination of the movable swash plate 30 of the hydraulic pump 29. The inclination of the movable swash plate 30 is changed by a hydraulic cylinder 36 (FIGS. 4 and 5) that operates by detecting the movement of the main transmission lever 11 and the forward / reverse lever 6 and rotates the motor output shaft 33 of the hydraulic motor 31. Is shifted. The rotation of the pump output shaft 32 directly connected to the hydraulic pump 29 is the same as the rotation speed of the input shaft 28.

  The rotation of the pump output shaft 32 is transmitted from the PTO first intermediate shaft 38 to the PTO second intermediate shaft 39 via the PTO forward / reverse clutch 37, and finally through the PTO auxiliary transmission clutch 40 to finally transmit on the PTO output shaft 41. It is taken out of the case 23 and drives a working machine such as a rotary.

The PTO forward / reverse clutch 37 will be described. The position of the shift gear 43 in FIG. 3 indicates a neutral position.
When the shift gear 43 meshed with the gear 43a fixed to the clutch shaft 42 connected to the pump output shaft 32 is moved to the left and meshed with the reverse gear 44a on the transmission upper side, the reverse gear 44a and the pair of gears 44 are driven to the first shaft. Since the gear 45 is engaged with one gear 45 of the double gear 46 loosely fitted to the gear 51, the power of the clutch shaft 42 is transmitted through the gear 43 a, the shift gear 43, the reverse gear 44 a, and the gear 44 to the gear 45 of the double gear 46. It is transmitted to. Then, the other gear 47 of the double gear 46 is transmitted to the gear 50 fixed to the PTO countershaft 50a, and the PTO first intermediate shaft 38 is connected to the clutch shaft 42 through the gear 49 loosely fitted from the gear 50. It is transmitted to the fixed gear 48. The PTO first intermediate shaft 38 is reversed by the flow of the transmission system.

  Further, when the shift gear 43 is engaged with the forward rotation gear 49 a on the lower transmission side, the power of the clutch shaft 42 is transmitted to the forward rotation gear 49 a via the gear 43 a and the shift gear 43. Since the forward rotation gear 49 a is integral with the gear 49, power is transmitted from the gear 49 to the gear 48 fixed to the PTO first intermediate shaft 38. The PTO first intermediate shaft 38 is rotated forward by the flow of the transmission system.

  The PTO auxiliary transmission clutch 40 has a small gear 52, an intermediate gear 53, and a large gear 54 fixed to a PTO second intermediate shaft 39 connected to the PTO first intermediate shaft 38, and is provided in parallel with the PTO second intermediate shaft 39. A large clutch gear 55 meshed with the small gear 52 is fitted into the PTO output shaft 41, and a shift gear 58 formed with an intermediate gear 56 and a small gear 57 is slidably engaged. A gear dock 55 a is formed on the side surface of the large clutch gear 55. A gear dock 56 a is also formed on the side surface of the middle gear 56.

  When the shift gear 58 is slid leftward and the gear dock 56a of the middle gear 56 and the gear dock 55a of the large clutch gear 55 are engaged, the PTO output shaft 41 is driven at the first PTO speed (low speed). When the shift gear 58 is slid to engage the intermediate gear 53 and the intermediate gear 56, the PTO output shaft 41 is driven at the second PTO speed (medium speed). When the shift gear 58 is slid left and the large gear 54 and the small gear 57 are engaged with each other, the PTO output shaft 41 is driven at the PTO third speed (high speed).

The motor output shaft 33 of the hydraulic motor 31 drives the front and rear wheels 4 and 5, and the transmission path is as follows.
A gear 59 fixed to the traveling first shaft 51 connected to the output shaft 33 is meshed with a clutch gear 60 loosely fitted to the traveling second shaft 61, and the traveling first gear 63 is shifted via a sub-transmission clutch 63 that shifts to high, middle, and low. It has a transmission path for driving the two shafts 61 to transmit to the rear wheel 5 and a transmission path for driving the front wheels 4 from the traveling second shaft 61 via the front wheel clutch 90.

The subtransmission clutch 63 shifts as follows.
The power of the clutch gear 60 always rotates the triple gear 70 by meshing the large gear 88 of the triple gear 70 loosely fitted to the PTO first intermediate shaft 38 with the gear 64 integral with the clutch gear 60. When the internal gear sub-transmission clutch 63 that is always meshed with the gear 62 fixed to the traveling second shaft 61 and is slidable is meshed with the gear 65 integral with the clutch gear 60, the rotation of the clutch gear 60 causes the gear 65 and the internal gear to rotate. It is transmitted to the traveling second shaft 61 via the auxiliary transmission clutch 63 and the gear 62 and rotates the traveling second shaft 61 at a high speed (subtransmission high speed).

  A gear 69 and a gear 66 are integrally fitted to the traveling second shaft 61 on the lower transmission side of the gear 62. Further, the gear 68 and the gear 67 are integrated, and are loosely fitted in an intermediate portion between the gear 69 and the gear 66. The gear 69 meshes with a gear 73 of a triple gear 70 that is loosely fitted to the PTO first intermediate shaft 38, and the gear 68 is loosely fitted to the PTO first intermediate shaft 38. The gear 72 is engaged.

  When the internal gear subtransmission clutch 63 is slid rightward and meshed with the gear 66, the rotation of the clutch gear 60 is the gear 64, the gear 88, the gear 73, the gear 69, the gear 66, the internal gear subtransmission clutch 63, and the gear 62. Is transmitted to the traveling second shaft 61, and the traveling second shaft 61 is rotated at a medium speed (sub-transmission medium speed).

  When the internal gear sub-transmission clutch 63 is further slid to the right and meshed with the gear 67, the rotation of the clutch gear 60 causes the gear 64, the gear 88, the gear 72, the gear 68, the gear 67, the internal gear sub-transmission clutch 63, and the gear. It is transmitted to the traveling second shaft 61 via 62 and rotates the traveling second shaft 61 at a low speed (sub-transmission low speed).

  A rear wheel differential gear mechanism 74 is attached to the rear end portion of the traveling second shaft 61 to drive the rear wheel 5. Further, from the gear 71 fixed to the traveling second shaft 61, the gear 75 further loosely fitted to the triple gear 70 loosely fitted to the PTO first intermediate shaft 38, and the gear fixed to the front wheel shaft 77. The front wheel shaft 77 is transmitted via 76.

  When a hydraulic clutch input shaft 78 is connected to the front wheel shaft 77 and a constant speed clutch 79 is connected, the rotation of the input shaft 78 is transmitted to the hydraulic clutch output shaft 84 at the same speed as it is. When the speed increasing clutch 80 is connected, the speed is increased by the gears 86 and 83 to rotate the relay shaft 81, and further the speed increasing drive is performed to rotate the hydraulic clutch output shaft 84 by the gears 82 and 87. When the constant speed clutch 79 and the speed increasing clutch 80 are not connected together, the power is not transmitted and only the rear wheel drive is performed. The rotation of the hydraulic clutch output shaft 84 drives the front wheels 4 via the front wheel differential gear mechanism 85.

Next, the transmission mechanism of the hydraulic continuously variable transmission 27 by the main transmission lever 11 will be described.
A transmission plate 92 is pivotally supported on a pin 91 erected on the side surface of the intermediate case 21 constituting the transmission case 23, and the transmission plate 92 is connected to the main transmission lever 11 by a link 94. The transmission plate 92 is lightly locked at eight locations along the guide plate 93 so that the transmission stage feels in eight stages. (See FIG. 4) The rotational position of the transmission plate 92 is transmitted to the control device 96 by the transmission sensor 95.

The hydraulic continuously variable transmission 27 is disposed in the front case 19 constituting the mission case 23. A neutral holding mechanism 98 that holds the trunnion shaft 97 connected to the movable swash plate 30 in the front case 19 in the forward / backward neutral position is configured. (See Figure 6)
The neutral holding mechanism 98 fixes a cam plate 99 to a trunnion shaft 97 protruding from the inside of a case 66 in which the variable pump 29 and the hydraulic motor 31 are housed on the upper surface of the hydraulic continuously variable transmission 27. When the roller 100 urged by the spring cylinder 101 is pressed against the peripheral cam portion 99 of the roller 99 and the roller 100 falls into the recess 99a of the peripheral cam portion of the cam plate 99, the trunnion shaft 97 returns to the neutral position. The state shown in FIG. 6 is a neutral state.

  The guide plate 104 having the long hole 104 a is fixed to the front case 19 constituting the mission case 23. A link (plate) 105 is fixed to the lower side of the shift shaft 102 penetrating to the outside of the front case 19, and a connecting pin 114 is provided upright on the link 105. Further, the connecting pin 114 is inserted into the elongated hole 104a of the guide plate 104 and moves along the elongated hole 104a. A link (rod) 103 is connected to the connecting pin 114, and the link 103 is connected to the cam plate 99. Therefore, when the shift shaft 102 is rotated, the connecting pin 114 is moved along the long hole 104a, and the trunnion shaft 97 is rotated via the link (rod) 103 and the cam plate 99 so that the gear can be changed.

  Since the link 103 is received and placed on the guide plate 104, the lower side of the link 104 is bent downward to form a bent portion 104b so as to move smoothly. The neutral holding mechanism 98 performs inspection and repair by opening the upper side of the front case 19, but since it is the upper side of the transmission case 23, the neutral holding mechanism 98 can be operated without draining the internal oil, so that maintenance is easy.

  At the portion of the shift shaft 102 that protrudes upward from the front case 19, the tip of the rod 110 of the hydraulic cylinder 36 attached to the side surface of the front case 19 with the bracket 115 and the arm 113 fixed to the shift shaft 102 are connected to the link 111, link 111 a, The rods 112 are connected. The link 111 and the link 111a rotate with the fulcrum 111b as a fulcrum, and the rod 112 moves in response to the rotation of the link 111a. Therefore, the shift shaft 102 is rotated by the operation of the hydraulic cylinder 36, and the trunnion shaft 97 is rotated by the rotation of the shaft 102 to shift the hydraulic continuously variable transmission 27.

  A shift angle sensor 106 that detects the rotation angle of the shift shaft 102, that is, the rotation angle of the trunnion shaft 97 is engaged with the connecting pin 117 of the arm 113 and the rod 112. The shift angle sensor 106 is attached to the shift shaft mounting plate 107 so that it can be assembled at the time of sub-assembly of shift shaft related parts. Further, the shift shaft mounting plate 107 is provided with stopper bolts 108 and 109, and the plate 102a that rotates together with the shift shaft 102 abuts against the stopper bolts 108 and 109, so that the shift shaft 102 is over-rotated (over). (Run) is prevented.

  On the rod 110 side of the hydraulic cylinder 36, a pin 110 a that connects the rod 110 and the link 111 is provided at the tip of the rod 110, but a bracket 116 provided with a stopper 118 that restricts excessive movement of the rod 110 is provided. It is attached to the side surface of the front case 19. The pin 110a abuts against the stopper 118 to restrict the rod 110 from moving too much. 4 is a stopper on the reduction side of the rod 110. The bracket 115 is configured to be recessed by forming a recess at the cylinder position of the bracket 115 in order to bring the hydraulic cylinder 36 close to the wall surface of the front case 19.

  Before the assembly work for connecting the rod 110 of the hydraulic cylinder 36 and the shift shaft 102 with the link 111, the link 111a, the rod 112 and the arm 113, the temporary neutral position is stored in the control device 96 by the temporary neutral setting means of the hydraulic cylinder 36, The control device 96 moves the rod 110 to the connection position to perform the connection work, and then stores the position of the rod 110 that becomes neutral by the neutral holding mechanism 98 in the control device 96 as a correct formal neutral position. In the temporary neutral position storage state, even if the main speed change lever 11 is at the highest speed, the movement speed of the rod 110 is limited to about half to limit the traveling speed, and the moving speed during the assembly work is limited.

  The control device 96 that controls the hydraulic cylinder 96 receives the information shown in FIG. 7 and outputs control signals to the speed increasing solenoid 123 and the speed reducing solenoid 124 of the hydraulic control valve. The input signal includes a forward or reverse signal from a forward / reverse switch 119 provided at the base of the forward / reverse lever 6, a shift position signal from the shift sensor 95 of the main shift lever 11, and a trunnion shaft 97 from the shift angle sensor 106. Rotation angle signal, a depression signal from the clutch pedal switch 120 that detects depression of the clutch pedal 9, an on / off signal of the engine speed control switch 121, and a sub shift position from the sub shift detection switch 122 of the sub shift lever 12 Signal.

The traveling speed control by the control device 96 is performed as follows.
First, the engine speed control switch 121 automatically reduces the turning speed to a safe speed when turning from high-speed straight traveling to turning by turning on the switch 121 in order to prevent sudden turning during turning. Instead of lowering the rotation of the engine 24, the hydraulic cylinder 36 is operated to turn the trunnion shaft 97 to the speed lowering side. Since the speed can be changed while keeping the engine speed constant in this way, the operating pressure of other control hydraulic pumps is not reduced, so that the performance of the tractor is not reduced. Although this function can ensure safety during high-speed driving, when performing operations such as tilling at low speed, control is performed to reversely increase the turning speed under the condition that the sub-shift position switch 122 is at low speed. This makes it possible to work efficiently. In addition, the control for increasing the turning speed may be performed separately by providing a high-speed switch during turning and turning on this switch.

  The hydraulic cylinder 36 mainly detects the position of the speed change position of the main speed change lever 11 as a target speed by the speed change sensor 95 and operates the speed increasing solenoid 123 or the speed reducing solenoid 124 to operate the hydraulic cylinder 36 to move the trunnion shaft 97. Rotate to reach the target speed.

  At this time, the trunnion shaft 97 rotates. The rotation movement of the trunnion shaft 97 is detected by a shift angle sensor 106 provided in the middle of the link mechanism R, and the control device 96 detects from the shift angle sensor 106. Is received so that the rotation amount of the trunnion shaft 97 becomes the target position. That is, the shift sensor 95 that detects the movement of the main transmission lever 11 merely transmits the position of the main transmission lever 11 to the control device 96, and the actual position of the trunnion shaft 97 is confirmed by the shift angle sensor 106. Do.

  If the current speed is far from the target shift speed (for example, when increasing from the second speed to the eighth speed), the first speed is activated to bring the speed closer to the target speed and close to the target speed. Then, the speed increase rate is lowered so that the shift to the target speed can be made quickly with less shift shock.

  If the current speed exceeds the low speed range set by the auxiliary speed change lever 12 when the auxiliary speed change lever 12 is switched from high speed to low speed, the main speed change lever 11 may be set to the higher speed side to lower the speed. Control is also performed to reduce the range.

  Further, the speed of the hydraulic cylinder 36 is changed depending on the position of the sub-shift lever 12, for example, when the sub-shift is high, the operation speed of the hydraulic cylinder 36 is slowed down and the shift is performed slowly. The speed is increased and the speed change is performed quickly so that the speed change can be performed quickly with little speed change shock.

  Further, when the clutch pedal 9 is stepped down during high-speed traveling and then reconnected by stopping the depression of the clutch pedal 9, the shift position of the trunnion shaft 97 is lowered below the target speed of the main shift lever 11, and gradually By returning the rotation angle of the trunnion shaft 97 to the target speed, the rapid increase due to the reconnection of the main clutch 34 is prevented.

  Further, when the forward speed and the reverse speed are made the same in the hydraulic continuously variable transmission 27, the reverse speed is controlled by the control device 96 so that the movement of the hydraulic cylinder 36 during the backward movement is suppressed to 80 to 90% during the forward movement. It only has to be lower than the forward speed.

  In addition, when the brake pedal sensor 125 is provided and the forward / reverse lever 6 is in the neutral position and the brake pedal 125 is depressed, the hydraulic cylinder 36 is moved faster than usual so that the speed is rapidly reduced and the brake is suddenly applied. good.

  As described above, the automatic speed control switch is provided to automatically reduce the speed when turning, but in this embodiment, the traveling speed can be changed by the hydraulic continuously variable transmission 27. When it is turned on, the hydraulic cylinder 36 may be operated to raise it to about 80% of the command speed of the main shift lever 11 when the work implement is raised. The traveling speed reduction rate when the working machine is raised may be uniform or may be changed depending on the speed. Even if the main transmission lever 11 is operated at the time of this speed reduction, the speed is changed while maintaining the same speed reduction rate.

  Further, when the traveling speed reduced by the first working machine ascending is maintained and the main speed change lever 11 is moved and the instruction speed is lowered to the lowered traveling speed, the traveling speed reduction control is released and thereafter the instruction of the main speed changing lever 11 is issued. The restriction release control may be performed so that the vehicle travels at a speed.

FIG. 8 is a hydraulic circuit diagram, which includes a main pump 140 used for work machine control and travel control, a hydraulic continuously variable transmission 27, and a sub pump 143 that sends the operating pressure of the power steering 144, and rotates the trunnion shaft 97. Since the control hydraulic pressure of the hydraulic cylinder 36 that moves is supplied from the main pump 140 to the trunnion valve 142 through the relief valve 141, the operating pressure of the pressure oil is stable.

The pressure oil from the sub pump 143 is supplied to the power steering 144 and then supplied to the hydraulic continuously variable transmission 27 through the lily valve 145 and the oil cooler 146.
The pressure oil from the main pump 140 is adjusted by the main relief valve 151 to control the travel clutch 34 through the travel valve 147 and the left and right brake cylinders 149 and 150 through the brake valve 148 and further diverted. Pressure oil is sent to work equipment related controls.

  The pressure oil related to the working machine is sent to the horizontal cylinder 154 and the main elevating cylinder 157 by the diversion valve 152. The horizontal cylinder 154 is controlled by a horizontal valve 153, the main elevating cylinder 157 is controlled by an electrohydraulic valve 155 and a slow return check valve 156, and the pressure oil is returned into the mission case 23 through the safety relief valve 158.

It is a top view of a hydraulic drive vehicle (tractor). It is a side view of a hydraulic drive vehicle (tractor). It is a power transmission diagram in a mission case. It is a partial enlarged side view. It is a partial enlarged plan view. It is a partially expanded plan view in a mission case. It is a control block diagram. It is a hydraulic circuit diagram.

R link mechanism
11 Main transmission lever 23 Mission case 27 Hydraulic continuously variable transmission 36 Hydraulic cylinder 66 Hydraulic continuously variable transmission case
95 shift sensor
96 control device 97 trunnion shaft 98 neutral holding mechanism 102 shift shaft
106 shift angle sensor
110 rods

Claims (2)

When the hydraulic continuously variable transmission (27) is arranged in the transmission case (23), the trunnion shaft (97) of the hydraulic continuously variable transmission (27) is arranged to face upward, and the trunnion shaft (97) The link mechanism (R) connected to the transmission case is configured to protrude upward from the transmission case (23), and the neutral holding mechanism (98) for holding the neutral position of the trunnion shaft (97) is disposed in the transmission case. (23) A hydraulic cylinder (36) for operation which is provided in (23) and protrudes from the transmission case (23) and which is connected to the trunnion shaft (97) and which is attached to the outside of the transmission case (23). And connected with
The speed change position of the main speed change lever (11) is detected by the speed change sensor (95), the hydraulic cylinder (36) is operated to turn the trunnion shaft (97) to the target speed, and the trunnion shaft (97) Is detected by a shift angle sensor (106) provided in the middle of the link mechanism (R), and feedback control is performed so that the rotation amount of the trunnion shaft (97) becomes a target position.
Further, when the temporary neutral position of the hydraulic cylinder (36) is stored in the control device (96), the movement of the rod (110) of the hydraulic cylinder (36) is limited to substantially half. Gearbox. An automatic speed control switch for automatically reducing the speed when the vehicle turns is provided. When the automatic speed control switch is turned on to raise the work implement, the speed is increased to a predetermined ratio of the instruction speed of the main transmission lever (11). 2. The transmission of a hydraulically driven vehicle according to claim 1, wherein the transmission is reduced .

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