JP2009262728A - Transmission of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate transmission operation and to minimize transmission shock by rationalizing an order to arrange transmission clutches within a transmission case. <P>SOLUTION: A transmission of a working vehicle is constructed in the following manner: when the transmission clutches are arranged within the transmission case 1 for transmitting driving force from an engine 14 to rear wheels 58, a forward/backward change clutch 2 is installed from the transmission upstream side, and a high/low speed change clutch 8 causing slight transmission differences is arranged on the downstream side of the forward/backward change clutch 2, and multistage transmission clutches 3 and 4 are arranged on the downstream side of the high/low speed change clutch 8. A clutch pedal 6 is also installed which operates to disengage both the forward/backward change clutch 2 and the high/low speed change clutch 8, and operates for a double mating condition in which a plurality of shift stages mate the multistage transmission clutches 3 and 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission device from an engine to a traveling device in a work vehicle such as a tractor or a passenger management machine.

In a work vehicle such as a tractor, as described in Japanese Patent Application Laid-Open No. 2004-201622, a main clutch that interrupts power in a transmission case that transmits power from an engine to a traveling wheel, a shift clutch of a multi-stage transmission gear, or a front wheel The front wheel drive clutch that interrupts the power transmission of the engine is provided, so that the rotation speed of the traveling wheel can be finely increased / decreased with multi-speed shifting so that the rotation output of the diesel engine with a narrow practical rotation range can be driven at a speed according to the working conditions. ing. And each clutch of a gear stage is comprised so that it can shift while drive | working with a hydraulic multi-plate clutch or a hydraulic synchromesh.
JP 2004-201622 A

  The transmission device of the work vehicle as described above changes the gear position every time the gear speed is changed and the travel speed is changed. However, if the gear ratio of the gear speed is large, the travel speed changes suddenly every time the gear is changed. You will feel.

  In view of the above, an object of the present invention is to make it easy to perform a shift operation and extremely reduce a shift shock by rationalizing the arrangement order of the shift clutch in the mission case.

The above object of the present invention is achieved by the following configuration.
That is, according to the first aspect of the invention, when the transmission clutch is provided in the transmission case 1 that transmits the driving force from the engine 14 to the rear wheel 58, the forward / reverse switching clutch 2 is provided from the upstream side of the transmission, and the forward / reverse switching is performed. A work vehicle having a structure in which a high / low speed switching clutch 8 with a small shift difference is arranged downstream of the clutch 2 and multistage transmission clutches 3 and 4 are arranged downstream of the high / low speed switching clutch 8. It is a transmission device.

In this configuration, the forward / reverse switching clutch 2 is switched to switch the traveling direction back and forth, and the high / low speed switching clutch 8 and the multi-stage transmission clutches 3 and 4 are switched to change the traveling speed.
In the second aspect of the invention, the clutch pedal 6 that operates to disengage both the forward / reverse switching clutch 2 and the high / low speed switching clutch 8 and operates the multi-speed gear clutches 3 and 4 in a double-engaged state in which a plurality of gear speeds mesh with each other. The transmission device for a work vehicle according to claim 1, wherein the transmission device is provided.

  In this configuration, when the clutch pedal 6 is depressed, the forward / reverse switching clutch 2 and the high / low speed switching clutch 8 are disconnected, and the driving force transmission of the engine 14 is completely disconnected, and the multi-speed clutches 3 and 4 are double-engaged. Thus, the rear wheel 58 can be prevented from rotating unexpectedly.

The effect by the said structure is as follows.
According to the first aspect of the present invention, when the traveling speed is changed a little, if only the forward / reverse switching clutch 2 is operated, the shift shock can be reduced and the operation can be easily performed.

  According to the second aspect of the present invention, when the clutch pedal 6 is depressed when the vehicle is temporarily stopped during traveling, the transmission of the driving force to the rear wheel 58 of the engine 14 is completely cut off and rotation of the rear wheel 58 due to external force is prevented. Since the aircraft is kept in a stopped state, there is an effect that it is possible to easily and safely stop on a slope.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a drive force transmission mechanism, and shows a power transmission configuration from the engine 14 to the front wheels 89, the rear wheels 58, the PTO drive shaft 113, and the hydraulic pump 10.

  A gear 16 is fixed to the input shaft 15 directly connected to the output shaft of the engine 14 and the forward / reverse switching clutch 2 is mounted. The gear 16 meshes with a gear 92 fixed to the first counter shaft 91, meshes with another gear 93 fixed to the first counter shaft 91, and this gear 94 is fixed to the input shaft 96 of the hydraulic pump 10. The hydraulic pump 10 is always driven by meshing with the gear 95. A power steering hydraulic pump 133 is provided adjacent to the hydraulic pump 10 and driven by the input shaft 96.

  One gear 17 of the forward / reverse switching clutch 2 meshes with a gear 19 fixed to the first transmission shaft 18 and decelerates, and the other gear 20 of the forward / reverse switching clutch 2 is connected to the first transmission shaft 18 via a counter gear 22. The power is transmitted in reverse by meshing with the fixed gear 23. That is, when the forward / reverse switching clutch 2 is placed (connected) to the gear 17 side, the rotation of the input shaft 15 is transmitted to the first transmission shaft 18 in the reverse direction, and when it is placed on the gear 20 side, the rotation of the input shaft 15 is forward. The main clutch disengaged state can be maintained by controlling the hydraulic valve, which will be described later, in the main clutch disengaged state in which the neutral state away from both the gear 17 and the gear 20 is disengaged from the power transmission. I am doing so.

  A third counter shaft 34 is connected to the first transmission shaft 18 on the lower transmission side of the forward / reverse switching clutch 2 by a coupling 33 to transmit the rotation as it is. A small gear 35 and a large gear 36 are fixed to the third counter shaft 34.

  The small gear 35 and the large gear 36 mesh with the large gear 38 and the small gear 39 of the high / low speed switching clutch 8 mounted on the second transmission shaft 37, respectively, and the third counter shaft 34 rotates at a high speed or a low speed at the second transmission shaft. 37. The high / low speed switching clutch 8 is switched by a high / low switching lever provided in the driver's seat.

  The second transmission shaft 37 has a first speed / three speed switching clutch 3 and a second speed / four speed switching clutch 4 which are operated to shift by a main transmission lever provided in the driver's seat on the lower transmission side of the high / low speed switching clutch 8. Wearing. That is, the gears 25 and 27 of the first transmission clutch 3 are engaged with the gears 26 and 28 fixed to the second countershaft 24, and are decelerated for the first speed or slightly increased for the third speed. Is transmitted to the second counter shaft 24. Further, the gears 29 and 31 of the second speed change clutch 4 are engaged with the gears 30 and 32 fixed to the second countershaft 24, and are slightly increased for the second speed or greatly increased for the fourth speed. The rotation of the transmission shaft 37 is transmitted to the second counter shaft 24.

A gear 42 is fixed to the lower transmission side end of the second counter shaft 24, and the gear 42 and a large gear 44 of a large and small gear 59 pivotally supported on the third drive shaft 49 are meshed with each other to reduce the transmission. Yes.
The small gear 45 of the large and small gear 59 meshes with the gear 43 of the double sub-transmission clutch 40 with a synchro mechanism that is pivotally supported by the bevel gear shaft 48, and is transmitted at a reduced speed. Further, the gear 47 provided integrally with the gear 43 is engaged with the large gear 50 fixed to the fifth countershaft 120 for transmission at a reduced speed.

  A small gear 51 is further fixed to the fifth counter shaft 120, and the small gear 51 is engaged with the large gear 46 of the double sub-transmission clutch 40 to be further decelerated. Therefore, the rotation of the second transmission shaft 37 is transmitted while being sequentially decelerated in the order of gear 42 → large gear 44 → small gear 45 → gear 43 → gear 47 → large gear 50 → small gear 51 → gear 46.

  The shifters 121 and 122 of the double auxiliary transmission clutch 40 are slidably engaged with the bevel gear shaft 48 in the axial direction. When the shifter 121 is slid to the gear 43 side and engaged, the rotation of the gear 43 remains at a high speed. When the shifter 122 slides to the gear 47 side and engages with the bevel gear shaft 48, the rotation of the gear 47 is transmitted to the bevel gear shaft 48 at a medium speed, and when the shifter 122 slides to engage with the gear 48 side and rotates, the gear 47 rotates. Is transmitted to the bevel gear shaft 48 at a low speed, and is gradually decelerated to rotate the bevel gear shaft 48.

  The shifters 121 and 122 of the double auxiliary transmission clutch 40 are operated by the auxiliary transmission lever 7 provided in the driver's seat. In order to change the gear combination, the rotation of the drive shaft must be slowed down or stopped completely. However, the control is performed by a traveling system controller 135 incorporating a microcomputer as described later. The sub-shift lever 7 is configured as shown in FIG. 6, and the sub-shift lever 7 is tilted back and forth to move the shifters 121 and 122 to shift to high speed, medium speed, and low speed. The part 9 is provided with a clutch switch 5, an acceleration switch 11, and a deceleration switch 13.

The rotation of the bevel gear shaft 48 is transmitted to the differential gear 123 via the bevel gears 54 and 55, and is transmitted from the differential gear 123 to the rear wheel 58 via the axle 56 and the planetary gear 57.
To summarize the above description, the rotation of the input shaft 15 is first switched to forward rotation or reverse rotation by the forward / reverse switching clutch 2, and is shifted to two stages by the high / low speed switching clutch 8. The second-speed / four-speed switching clutch 4 shifts the gear to four speeds, and the double sub-transmission clutch 40 shifts the gear to three speeds, and is transmitted to the bevel gear shaft 48. That is, the rotation of the input shaft 15 is shifted to 2 × 4 × 3 = 24 speeds and transmitted to the axle 56.

  At the time of shifting the double sub-transmission clutch 40, the clutch switch 5 of the sub-transmission lever 7 is pushed to change the forward / reverse switching clutch 2, the first / third speed switching clutch 3, and the second / fourth speed switching clutch 4. Either the connected one or the high / low speed switching clutch 8 is made neutral at the same time, but when the clutch is connected, the last connected clutch is worn out, so the connection order is changed sequentially.

  Transmission to the front wheel 89 is performed as follows. A gear 53 is fixed to the bevel gear shaft 48, and the gear 53 is meshed with a gear 52 fixed to the third drive shaft 49 to drive the third drive shaft 49. Another gear 68 fixed to the third drive shaft 49 is meshed with a gear 69 of a front wheel acceleration clutch 70 attached to a transmission shaft 67 connected to the front wheel drive shaft 76 by a coupling 75. The gears 126 and 74 of the front wheel acceleration clutch 70 and the all-wheel drive clutch 156 are engaged with gears 72 and 73 fixed to the seventh countershaft 71, so that the front wheel acceleration and the rear wheel drive (two-wheel drive) ).

  A gear 77 is fixed to the front wheel drive shaft 76 and is engaged with a gear 78 fixed to the front wheel drive bevel shaft 127 to transmit power. The power of the front wheel drive bevel shaft 127 drives the front wheels 89 via the bevel gears 79 and 80, the differential gear 81, the bevel gears 82 and 83, the vertical shaft 84, the bevel gears 85 and 86, and the planetary gear 88.

Next, the power transmission of the PTO drive shaft 113 will be described.
The gear 16 of the input shaft 15 is engaged with the gear 101 of the PTO intermittent clutch 100 mounted on the fourth counter shaft 102, and two gears 103 and 104 are fixed to the fourth counter shaft 102.

  A first PTO shaft 107, a second PTO shaft 66, and a third PTO shaft 109 are arranged in series with respect to the input shaft 15 at a position symmetrical to the input shaft 96 of the hydraulic pump 10, and the first PTO shaft on the uppermost transmission side is arranged. One side of the drive switching clutch 67 mounted on the second PTO shaft 66 at high speed or low speed by the PTO high / low clutch gears 105, 106 mounted on the PTO shaft 107 meshing with the gears 103, 104 and sliding the shifter, respectively. The disk 114 is driven.

  The other disk 115 of the drive switching clutch 67 meshes with a gear 64 fixed to the sixth countershaft 62 with a gear 65 integrated with the other disk 115. The sixth counter shaft 62 is transmitted by meshing the gear 61 fixed to the ground shaft 60 connected to the third drive shaft 49 with the coupling 116 with the gear 63 fixed to the sixth counter shaft 62. The power from the bevel gear shaft 48 that drives the rear wheel 58 is transmitted to the other disk 115.

  Therefore, when the shifter 117 of the drive switching clutch 67 is slid to the one-side disk 114, the power of the first PTO shaft 107 is transmitted, and when the shifter 117 is slid to the other-side disk 115, the power from the ground shaft 60 is transmitted.

  The second PTO shaft 66 to which the drive switching clutch 67 is attached is connected to the third PTO shaft 109 by the coupling 108, and the shaft of the gear 111 is connected to the third PTO shaft 109 by the coupling 110. The PTO drive shaft 113 is driven by meshing with the gear 112 fixed to the PTO drive shaft 113.

  FIG. 2 is a power transmission diagram in which the periphery of the drive switching clutch 67 is changed. The long ground shaft 60 is changed to the short eighth counter shaft 118, and the power transmission from the bevel gear shaft 48 is cut off. Then, the gear 119 fixed to the eighth counter shaft 118 is engaged with the gear 97 fixed to the one-side disk 114 and the gear 98 fixed to the sixth counter shaft 62, and further fixed to the eighth counter shaft 118. The other disk 115 is reversely rotated by meshing another gear 99 with the gear 65 integrated with the other disk 115. Accordingly, when the shifter 117 of the drive switching clutch 67 is slid to the one-side disk 114, the power of the first PTO shaft 107 is transmitted in the normal direction, and when the shifter 117 is slid to the other-side disk 115, the power of the first PTO shaft 107 is reversed. Will be transmitted at high speed. Therefore, by controlling the engine rotation from 2000 rpm to 1700 rpm, for example, in order to prevent reverse high-speed rotation, the normal PTO shaft rotation is performed at a low engine speed, thereby reducing fuel consumption. Become a shift.

  FIG. 3 is a longitudinal sectional view of the transmission case 1 that constitutes the transmission diagram of FIG. 1. The transmission case 1 is configured by connecting the hollow case of the front transmission case 1a, the intermediate transmission case 1b, and the rear transmission case 1c. ing. Inside the front mission case 1a, a forward / reverse switching clutch 2, a PTO intermittent clutch 100, a PTO high / low speed clutch 12, and a drive switching clutch 67 are incorporated, and a hydraulic pump 10 is mounted outside the case. Inside the intermediate transmission case 1b, a high / low speed switching clutch 8, a first / third speed switching clutch 3, a second / fourth speed switching clutch 4 and a front wheel speed increasing clutch 70 are incorporated. The rear transmission case 1c integrally constitutes a differential gear case, and a double subtransmission clutch 40 is built therein.

  4 is a longitudinal sectional view of the transmission case 1 constituting the transmission diagram of FIG. 2. The difference from FIG. 3 is that an eighth counter shaft 118 is installed instead of the long ground shaft 60. The drive switching clutch 67 functions as an economy shift by changing and adding gears.

  As shown in FIG. 5, the tractor having the transmission mechanism and the hydraulic circuit has an engine 14 mounted in the hood 125 at the front of the vehicle body, and transmits the rotational power of the engine 14 to the transmission mechanism in the transmission case 1. The rotational power appropriately decelerated is transmitted to the left and right front wheels 89 and the left and right rear wheels 58.

  A steering handle 126 for steering the left and right front wheels 89 and 89 is provided behind the engine 14, and a cockpit 127 is installed behind the steering handle 126. A cylinder case 128 is mounted on the rear upper part of the transmission case 1, and a clutch pedal 6 for switching power is provided at the feet of the cockpit 127. Left and right lift arms 129 and 129 are pivotally supported on both left and right sides of the cylinder case 128 so as to be rotatable. When the working oil is supplied to the hydraulic cylinder for raising and lowering the work implement housed in the cylinder case 128, the lift arms 129 and 129 are configured to rotate upward. Various work machines R can be connected to the three-point link mechanism of the lower link 130, 130 and the top link 131 connected to the lift arms 129, 129.

FIG. 7 is a plan view of the work machine control adjustment panel 180.
On the front side of the work implement control adjustment panel 180, an accelerator memory 179 that stores two types of rotation speed of the engine 14, a position control lever 181 that moves the work implement up and down, and a tillage depth adjustment that adjusts the tillage depth of the rotary tiller. A dial 182 is provided, an elevating control unit 200 and an automatic control setting unit 201 for controlling elevating of the left and right lift arms 129 and 129 are provided at the center, and an automatic control adjusting unit 202 and a horizontal control adjusting unit 203 are provided on the rear side. .

  The elevation control unit 200 is provided with an automatic control sensitivity standard input button 204, an automatic control type display unit 183, an automatic control switching button 205, a lowered position adjustment dial 184, and a lowering speed adjustment dial 185. Each time the automatic control switching button 205 is pressed, the auto rotary, mix auto, load auto, and draft lamps of the automatic control type display unit 183 are lit and the control is switched. For example, when autorotation is used, automatic horizontal control and backup control are performed.

  The automatic control setting unit 201 is provided with an auto accelerator button 186, an auto lift button 187, a backup button 188, and an auto brake button 189. The automatic control adjustment unit 202 includes a PTO intermittent automatic sensitivity button 190, a sensitivity adjustment button 191, a PTO connection button 192, a speed change connection button 193, a linear connection button 194, and a brake weakening button 195.

  The horizontal control unit 203 is provided with a horizontal sensitivity button 196, a horizontal switching button 197 for switching between tilt, parallel, manual, and automatic horizontal, a horizontal tilt adjustment dial 198, and a horizontal switch button 199 for setting the degree of tilt. For example, when the horizontal switch button 197 is manually set and the rotary tiller is tilted to the left and right with the left and right tilt adjustment dial 198 and then automatically switched again with the horizontal switch button 197, the rotary tiller is controlled to maintain the tilted state. This control is performed by adding / subtracting the correction value to the left / right sensor output values for detecting the left / right height of the rotary tiller by the work machine lifting / lowering system controller 171.

Next, various automatic controls by the microcomputer will be described.
FIG. 8 is a block diagram showing input / output of control signals. A travel system controller 135 that controls the travel speed, an engine controller 163 that controls the output of the engine 14, and a work machine lift system controller 171 that controls the lift of the work machine. It is connected with a communication line and communicates control signals.

  First, the travel system controller 135 receives on / off information of the clutches of the first speed / third speed switching clutch 3 and the second speed / fourth speed switching clutch 4 from the shift 1 clutch pressure sensor 136 and the shift 2 clutch pressure sensor 137. Input / output information of the high / low speed switching clutch 8 is input from the Hi clutch pressure sensor 140 and the Lo clutch pressure sensor 141, and the forward / reverse switching clutch 2 is input. ON / OFF information is input from the forward clutch pressure sensor 142 and the reverse clutch pressure sensor 143, and the forward / reverse lever operation position sensor 144 for detecting the shift position of the forward / reverse lever for shifting the forward / reverse switching clutch 2 and the secondary and secondary levers are detected. The shift position information is obtained from the auxiliary shift lever operation position sensor 145 that detects the shift position of the shift clutch 40. Input to the roller 135.

  Furthermore, the travel system controller 135 receives a travel speed from a vehicle speed sensor 146 that detects the number of revolutions of the rear wheel 58, and an oil temperature in the mission case 1 is input from the mission oil oil temperature sensor 147. The position of the clutch pedal is input from the sensor 148, and the engine power setting information is input from the engine power selection switch 149.

  Further, the accelerator shift information is input to the traveling system controller 135 from the accelerator shift setting switch 150, the setting information is input from the main shift acceleration / deceleration operation switch 151, the accelerator setting information is input from the accelerator sensor 152, and the accelerator fine adjustment is performed. Setting information is input from the lever 153, engine output torque line setting information is input from the torque selection switch 134, and an on / off signal is input from the clutch switch 5. The accelerator fine adjustment lever 153 is a rebound push switch, and the adjustment value changes step by step each time it is pressed.

  The control signal output from the travel system controller 135 is a signal for switching the hydraulic valve for operating the forward / reverse switching clutch 2 to the forward / reverse switching solenoid 154, a switching boost signal for the linear boost solenoid 155, and a neutral operation for the clutch solenoid 156. Signal, a switching signal to the shift 1-3 switching solenoid 157 and a boost signal to the shifting 1-3 boost solenoid 158 of the hydraulic valve for operating the first / third speed switching clutch 3, a second speed / fourth speed switching clutch 4 The switching signal to the shift 2-4 switching solenoid 159 of the hydraulic valve that operates the hydraulic valve, the boost signal to the shifting 2-4 boost solenoid 160, the Hi clutch switching solenoid 161 and the Lo clutch of the hydraulic valve that operates the high / low speed switching clutch 8 This is a high / low switching signal to the switching solenoid 162.

  The information signal input to the engine controller 163 includes the exhaust temperature from the engine exhaust temperature sensor 164, the rotational speed from the engine rotation sensor 165, the oil pressure from the engine oil pressure sensor 166, and the cooling from the engine water temperature sensor 167. The control signal output from the engine controller 163 at the water temperature and the common rail pressure from the rail pressure sensor 168 is a pressurization signal to the fuel high pressure pump 169 and a fuel injection signal to each high pressure injector 170.

  The information signal input to the work implement lifting system controller 171 is arm position information from the lift arm sensor 172, and the control signal output from the work implement lifting system controller 171 is a hydraulic cylinder that operates the left and right lift arms 129 and 129. It is a raising / lowering signal to the main raising solenoid 173 and the main lowering solenoid 174 of the main valve.

The meter panel 175 displays detection information of each sensor and switch setting information, and various setting signals are input through the operation panel 176.
For example, when the vehicle is stopped by depressing the clutch pedal 6, the automatic control is performed by disengaging the forward / reverse switching clutch 2 and the high / low speed switching clutch 8 to completely disconnect the power transmission of the engine 14, and thereby the first speed / third speed. Both the switching clutch 3 and the second speed / fourth speed switching clutch 4 are engaged so that the rear wheel 58 is not rotated by the mechanical lock. In this case, the double-engaged state is kept low and the clutch is engaged. Further, the clutch pressure in the double-engaged state may be changed according to the degree of depression of the clutch pedal 6. This clutch pressure adjustment may also be performed when the forward / reverse switching clutch 2 is operated. Further, the clutch pressure adjustment may be performed at all shifts.

  The first speed / third speed switching clutch 3 and the second speed / fourth speed switching clutch 4 are all disengaged when the clutch pedal 6 is depressed while the vehicle is running, and the main gear is increased or decreased when the clutch is stopped. The clutch may be engaged at the shift position set by the speed operation switch 151 so that the set speed can be quickly reached at the start.

  FIG. 9 is a flowchart of automatic control at the time of shifting of the double sub-shift clutch 40. In step S1, it is determined whether the clutch pedal provided at the foot of the driver's seat is depressed (ON). If NO, the sub-shift is performed in step S2. If it is determined that the clutch switch 5 provided on the lever 7 is ON and the determination in step S2 is YES or if the clutch pedal is ON in step S1, the forward / reverse switching clutch 2 and the first / third speed switching clutch 3 are determined in step S3. All the hydraulic clutches of the second speed / fourth speed switching clutch 4 and the high / low speed switching clutch 8 are made neutral so that the rotation of the engine 14 is not transmitted to the double sub-transmission clutch 40.

  Further, if the shift of the double sub-transmission clutch 40 is a shift from a high speed to a medium speed in step S4, the first speed / third speed switching clutch 3 and the second speed / fourth speed switching clutch 4 are reduced in pressure in step S5. And the double transmission is generated to completely stop the rotation of the transmission shaft, and the double sub-transmission clutch 40 is completely engaged in step S6.

  FIG. 10 shows the pressure control of each hydraulic clutch when the switching from the first speed to the second speed and the switching operation from the high speed to the low speed are simultaneously performed. FIG. 10 (B) shows the pressure change of the high / low speed switching clutch 8. First, the first speed clutch of the first speed / three speed switching clutch 3 is shown. The hydraulic pressure is turned off, and the second-speed clutch of the second-speed / four-speed switching clutch 4 is boosted to the extent that it does not double-engage with the first-speed clutch, and is fully boosted after the first-speed clutch is disconnected. The high / low speed switching clutch 8 disengages the high pressure side clutch of the high / low speed switching clutch 8 before disengaging the first speed side clutch so that the low pressure side clutch of the high / low speed switching clutch 8 is not double-engaged with the high pressure side clutch. After boosting the pressure and disengaging the first speed clutch, the pressure is gradually increased completely. By doing so, the shift shock can be reduced.

  FIG. 11 shows another embodiment of the pressure control of each hydraulic clutch when the switching from the first speed to the second speed and the switching operation from the high speed to the low speed are performed at the same time. FIG. 11 (A) shows the high / low speed switching clutch 8. FIG. 11B shows the pressure change of the first speed / third speed switching clutch 3 and the second speed / fourth speed switching clutch 4. First, the hydraulic pressure of the high speed side clutch of the high / low speed switching clutch 8 is shown. The low-pressure side clutch of the high / low-speed switching clutch 8 is increased to the extent that it does not double-engage with the high-speed side clutch, and is fully increased after the high-speed side clutch is disconnected. Before disengaging the high speed clutch of the high / low speed switching clutch 8, the first speed clutch of the first / third speed switching clutch 3 is disengaged, and the second speed clutch of the second / fourth speed switching clutch 4 is switched to the first speed clutch. The pressure is increased to such an extent that double engagement is not caused, and the pressure is gradually increased completely after the high-speed side clutch is disengaged. By doing so, the shift shock can be reduced as in the embodiment of FIG.

  FIG. 12 is an example of pressure control of each hydraulic clutch when moving forward at high speed. FIG. 12 (A) shows the pressure change of the high / low speed switching clutch 8 and FIG. 12 (B) shows the pressure change. ing. In the forward / reverse switching clutch 2, the high / low speed switching clutch 8 is kept in the clutch holding state at a low pressure and the low speed side clutch is disconnected simultaneously with the shift, and the high pressure side clutch gradually increases in pressure when the forward side of the forward / backward switching clutch 2 is engaged. Boost completely.

It is a power transmission diagram in a mission case. It is a power transmission diagram in the mission case which changed a part. FIG. 2 is a longitudinal sectional view of the mission case in FIG. 1. FIG. 3 is a longitudinal sectional view of the mission case of FIG. 2. It is the whole tractor side view. It is a partial enlarged side view. It is a top view of the operation panel of a working machine. It is a control block diagram. It is a control flowchart figure of a clutch. It is an Example of the oil pressure change of the main transmission clutch and the high / low speed switching clutch. It is another Example of the oil pressure change of a main transmission clutch and a high / low speed switching clutch. It is an Example of the oil pressure change of a high / low speed switching clutch and a forward / reverse clutch.

Explanation of symbols

1 Mission case 2 Forward / reverse switching clutch 3, 4 Multi-speed clutch (1st / 3rd speed switching clutch 3, 4th speed / fourth speed switching clutch 4)
6 Clutch pedal 8 High / low speed switching clutch 14 Engine 58 Rear wheel

Claims (2)

  In providing a speed change clutch in the transmission case (1) for transmitting driving force from the engine (14) to the rear wheel (58), the forward / reverse switching clutch (2) is provided from the upstream side of the transmission, and the forward / reverse switching clutch (2 ) The high / low speed switching clutch (8) with a small gear shift difference is arranged on the downstream side, and the multi-stage transmission clutches (3), (4) are arranged on the downstream side of the high / low speed switching clutch (8). A power transmission device for a work vehicle.   The clutch pedal (6) which operates by disengaging both the forward / reverse switching clutch (2) and the high / low speed switching clutch (8) and operating the multi-speed clutches (3), (4) in a double-engaged state in which a plurality of gear speeds mesh. The transmission device for a work vehicle according to claim 1, wherein:

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