JP6795055B2 - Travel transmission device for work vehicles - Google Patents

Description

The present invention relates to a traveling transmission device in a work vehicle such as a tractor in which a work device such as a tillage device is connected to a rear portion.

The rotational drive output from the engine is appropriately decelerated via multiple gears of the multi-stage transmission and transmitted to the drive wheels, and by changing the combination of the gears, the clutch pressure is applied to the traveling transmission device of the work vehicle that shifts gears. There is a known technique for reducing shift shock caused by a sudden change in vehicle speed during shift by providing an adjustable clutch in series with a multi-speed transmission, lowering the clutch pressure during shift, and gradually increasing the pressure (patented). Document 1).

Japanese Unexamined Patent Publication No. 2014-134291

However, in the invention described in the above patent document, for example, during high-load running such as tilling by plow traction, the speed drops sharply at the moment when the clutch pressure drops, which causes a shock during shifting and hinders smooth running. It was. Further, in the case of shifting during low-load driving such as when traveling on a road, it has been required to have an adjustable configuration so that the vehicle can travel more smoothly.

In order to solve the above-mentioned problems, the present invention includes a multi-stage transmission that shifts the rotational drive output from the engine in multiple stages, and a hydraulic clutch that transmits or cuts off the driving force that has been changed by the multi-stage transmission. It has a control unit that controls the clutch pressure of the hydraulic clutch, and the control unit reduces the clutch pressure to a neutral pressure that does not transmit power at the time of shifting, and then changes the connection pressure from the neutral pressure to the connection pressure before decompression within a specified connection time. In the traveling transmission device of the work vehicle having a standard pressure-increasing curve for boosting the pressure up to, a pressure-boosting adjustment dial is provided, and the adjustment value by the pressure-boosting adjustment dial has a high-pressure side connection pressure adjustment region according to the value. In the high pressure side connection pressure adjustment region, the standard booster curve is boosted according to the high pressure adjustment booster curve that is moved in parallel to the high pressure side according to the dial position, and the control unit uses the booster adjustment dial to adjust the high pressure side connection pressure. When it is at the maximum position of the region, the first feature is to change the standard boost curve to shift gears without depressurizing.

Further, in the invention having the first feature, the adjustment value by the step-up adjustment dial has a low-voltage side connection pressure adjustment region and a connection time adjustment region according to the value, and the control unit has a connection time adjustment region. When it is in the low pressure side connection pressure adjustment region, the standard booster curve is boosted according to the low voltage adjustment booster curve which is moved in parallel to the low voltage side according to the dial position, and when it is in the connection time adjustment region, the connection time is dialed. The second feature is that the voltage is adjusted according to the adjustment connection time according to the above, and the voltage is increased according to the time adjustment boost curve for increasing the connection pressure to the connection pressure before depressurization.

According to the invention having the first feature, in the case of high load work, it is possible to adjust the speed change quickly without reducing the pressure so that the vehicle can run smoothly.

According to the invention having the second feature, when the vehicle is traveling on a low load such as on a road, the clutch can be loosely connected after decompression to suppress shocks, and the speed change can be adjusted as desired to enable smooth traveling.

Side view of the entire tractor Transmission system development diagram of the traveling transmission device Control block diagram of the entire tractor Tractor hydraulic circuit diagram Cross section of forward / backward clutch Timing chart showing the movement of each clutch Perspective view around the main shift lever The figure which shows the adjustment position of the boost adjustment dial and the change of the boost curve of the forward / backward clutch.

Examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a passenger-type tractor as an example of a work vehicle. An engine room covered with a bonnet 2 is arranged in the front part of the traveling vehicle body 1, and an engine E is mounted inside the engine room. The rotational power of the engine E is transmitted to the traveling transmission device in the transmission case 3, and the rotational power decelerated by this traveling transmission device is transmitted to the front wheels 4 and the rear wheels 5.

A driver's seat 7 is installed in the cabin 6 at the rear of the vehicle body, and a steering handle 8 for steering the front wheels 4 and 4 is installed in front of the driver's seat 7. A meter panel 9 is installed on the front side of the steering wheel 8. The rear part of the tractor is equipped with a rotary work machine or the like, and is driven by a PTO shaft 111 protruding rearward from the mission case 3.

Explaining the power transmission mechanism in the transmission case as shown in FIG. 2, the rotation of the output shaft 20 of the engine E is transmitted to the input shaft 21, and the first input gear 22 and the second input gear 23 fixed to the input shaft are transmitted. The first low speed gear 26 of the first high / low clutch 24, the second low speed gear 27 of the second high / low clutch 25, and the first high speed gear 30 and the second high / low clutch of the first high / low clutch 24, respectively. It meshes with the second high-speed gear 31 of 25 and is driven to rotate.

The first high / low clutch 24 and the second high / low clutch 25 are the same hydraulic multi-plate clutch, and the rotation of the input shaft 21 is decelerated in two stages of high and low at the same reduction ratio, respectively, and the first clutch shaft. It will be transmitted to 28 and the second clutch shaft 29.

The rotations of the low-speed transmission shaft 34 and the high-speed transmission shaft 32 are transmitted to the first synchronization change 42 and the second synchronization change 36, respectively, and the first synchronization small gear 43 and the second synchronization small gear 37 are the fifth of the first transmission shaft 39. It meshes with the gear 40, and the first synchro large gear 44 and the second synchro large gear 38 mesh with the sixth gear 41 of the first transmission shaft 39 to transmit. As a result, the rotation of the first input shaft 21 is shifted to four low speed speeds and four high speed speeds on the first transmission shaft 39.

The multi-speed transmission 150 up to this point constitutes the main transmission, reads the shift position of the main transmission lever 15 operated by the operator, and the traveling system ECU 120 automatically performs the first, second high, and low hydraulic multi-plate clutches. By controlling 24 and 25 and the first and second synchro changes 36 and 42, the speed is changed to 4 low speeds and 4 high speeds.

The first transmission shaft 39 is connected to the second transmission shaft 45, and the seventh gear 46 and the eighth gear 47 are fixed to the second transmission shaft 45, and the forward / reverse clutch 48 forward rotation clutch gear 49 and the reverse rotation shaft It is meshed with the reverse gear 51 of 52, and the reverse gear 51 is meshed with the reverse clutch gear 50. Therefore, when the forward / reverse clutch 48 is connected to the forward clutch gear 49, it is transmitted to the auxiliary transmission shaft 53 connected to the reverse clutch 48 in the forward rotation state, and when the forward / reverse clutch 48 is connected to the reverse clutch gear 50, it is in the reverse state. It is transmitted to the auxiliary transmission shaft 53.

The ninth gear 54 and the tenth gear 55 are fixed to the auxiliary transmission shaft 53, and mesh with the third synchro small gear 56 and the third synchro large gear 59 of the third synchro change 58, respectively. When the third synchro change 58 is connected to the third synchro small gear 56 side, the fifth transmission shaft 60 is accelerated by the rotation transmitted from the ninth gear 54 to the third synchro small gear 56 and driven at high speed, and the third synchro change 58 is driven at high speed. When the synchro change 58 is connected to the third synchro large gear 59, the fifth transmission shaft 60 is decelerated and driven at a medium speed by the rotation transmitted from the tenth gear 55 to the third synchro large gear 59.

When the third synchro change 58 is set to neutral, the rotation of the tenth gear 55 is transmitted to the third synchro large gear 59, and is transmitted from the eleventh gear 57 fixed to the third synchro small gear 59 to the fourth synchro small gear 69. It is supposed to be done.

When the 4th synchro change 71 is connected to the 4th synchro small gear 69 side, the rotation of the 4th synchro small gear 69 becomes the rotation of the 16th gear 74 and becomes low speed, and the 4th synchro change 71 is changed to the 4th synchro large gear 72. When connected to the side, the rotation of the 4th synchro small gear 69 is transmitted from the 15th gear 70 to the 17th gear 75, the 18th gear 76, and the 4th synchro large gear 72, and the 16th gear 74 becomes ultra-low speed.

Further, the 16th gear 74 meshes with the 12th gear 61 fixed to the 5th transmission shaft 60 to drive the 5th transmission shaft 60. The first bevel gear 62 fixed to the shaft end of the fifth transmission shaft 60 meshes with the second bevel gear 63 of the rear bevel gear case 64, and the bevel output shaft 65 to the thirteenth gear 66 and the fourteenth gear 67 of the rear bevel gear case 64. The rear wheel output shaft 68 is rotated via the rear wheel 5 to drive the rear wheel 5.

Further, the 21st gear 117 is fixed to the 5th transmission shaft 60, and the 1st front wheel is interposed via the 22nd gear 118 and the 23rd gear 148 fixed to the 3rd cylinder shaft 119 pivotally supported by the auxiliary transmission shaft 53. It is transmitted to the 19th gear 77 of the drive shaft 78, and the rotation of the fifth transmission shaft 60 at 16 low speeds and 16 high speeds is transmitted to the first front wheel drive shaft 78.

It is transmitted from the first front wheel drive shaft 78 to the second front wheel drive shaft 85 via the front wheel speed-up clutch 79, and is transmitted to the third front wheel drive shaft 86, the fourth front wheel drive shaft 87, and the front wheel drive bevel shaft 88. The first front bevel gear 89 fixed to the shaft end of the front wheel drive bevel shaft 88 meshes with the second front bevel gear 115 of the front bevel case 90, and the front bevel output shaft 91 to the first front bevel gear 92 of the front bevel case 90. The front wheel output shaft 94 is rotated via the front wheel drive shaft 116 and the second bevel gear set 93 to drive the front wheel 4.

When the front wheel speed-up clutch 79 is connected to the front wheel constant speed gear 82 side, the rotational drive of the first front wheel drive shaft 78 is directly transmitted to the second front wheel drive shaft 85 to become a normal four-wheel drive, and the front wheel speed-up clutch 79 is engaged. When connected to the front wheel speed-up gear 84 side, the rotation in which the rotation drive of the first front wheel drive shaft 78 is accelerated from the front wheel constant speed gear 82 via the first speed-up gear 81 and the second speed-up gear 83 is second. It is transmitted to the front wheel drive shaft 85 and becomes front wheel speed-up four-wheel drive. Further, when the front wheel speed-up clutch 79 is set to the neutral state, power is not transmitted to the front wheels 4, so that the rear wheels are driven by two wheels.

The main clutch gear 96 of the PTO main clutch 97 is meshed with the second input gear 23 so that the PTO main clutch 97 performs power interruption and disengagement to the PTO output shaft 111.

The first PTO shaft 95 is provided with a PTO transmission unit 157, and is equipped with a first PTO gear 98, a second PTO gear 99, a fifth synchro small gear 100 and a fifth synchro large gear 101 of the fifth synchro change 151, and a second PTO. The 20th gear 102, the 24th gear 152, the 26th gear 103, and the 25th gear 153 are fixed to the shaft 107, and the PTO reverse gear 105 is pivotally supported on the counter shaft 106.

When the first PTO gear 98 is slid and meshed with the 20th gear 102, the second PTO shaft 107 becomes the second gear, and when the first PTO gear 98 is slid and engaged with the second PTO gear 99, the first PTO shaft 95 rotates. Is transmitted to the 2nd PTO shaft 107 via the 2nd PTO gear 99 and the 24th gear 152 to become the 4th gear, and when the 5th synchro change 151 is connected to the 5th synchro small gear 100, the 5th synchro small gear 100 to the 26th gear When the 5th synchro change 151 is connected to the 5th synchro large gear 101, it is transmitted from the 5th synchro large gear 101 to the 25th gear 153 to become the 3rd gear, and the PTO reverse gear 105 is set to the 1st speed. When the 1 PTO gear 98 and the 20th gear 102 are meshed with each other, the rotation of the 1st PTO shaft 95 is transmitted from the 1st PTO gear 98 to the 20th gear 102 via the PTO reverse gear 105 and is transmitted to the 2nd PTO shaft 107 to cause reverse rotation. ..

The rotation of the second PTO shaft 107 is transmitted to the fourth PTO shaft 108 via the third PTO shaft 156, and is further decelerated by the first PTO output gear 109 and the second PTO output gear 110 to drive the PTO output shaft 111.

FIG. 3 is a control block diagram that controls the operation of each part of the tractor, and controls the rotation of the engine ECU 190 that controls the output of the engine E, the work equipment elevating system ECU 191 that controls the elevating and lowering of the working machine, and the rotations of the front wheels 4 and the rear wheels 5. It is composed of a traveling system ECU 120 that controls the traveling speed, and communicates control signals by CAN communication.

The input of control data to the engine ECU 190 is the selection mode from the engine mode selection switch 192, the exhaust temperature from the engine exhaust temperature sensor 207, the rotation speed of the engine output shaft 20 from the engine rotation sensor 121, and the engine oil pressure. The oil pressure from the sensor 193, the radiator water temperature from the engine water temperature sensor 194, the fuel pressure of the common rail from the rail pressure sensor 198, the depression signal of the accelerator pedal 18 of the accelerator operation position detection sensor 195, etc., from the engine ECU 190. The control outputs are the rail pressure to the fuel high-pressure pump 196 and the injection signal to the high-pressure injector 197.

The control data is input to the work equipment lifting system ECU 191 by the operation signal from the position control sensor 199 by the position control lever 13 for raising and lowering the work equipment, the lift position signal from the lift arm sensor 200, and the lift position regulation dial. The control output from the work equipment elevating system ECU 191 by the adjustment signal of 201 and the lowering speed adjustment dial 202 is an ascending or descending signal to the main ascending solenoid 204 and the main descending solenoid 205 of the hydraulic elevating cylinder.

The control data is input to the traveling system ECU 120 by the first clutch Lo side pressure switch 122, the first clutch Hi side pressure switch 123, the second clutch Lo side pressure switch 124, the second clutch Hi side pressure switch 125, and the forward clutch pressure. Each signal of the sensor 128 and the boost adjustment dial 129, the operation position of the forward / backward lever operation position sensor 130 of the forward / backward lever 11, the operation position of the auxiliary shift position sensor 131 of the auxiliary shift lever, and the main shift of the main shift lever 15. The operation position of the lever position sensor 136, the oil temperature of the oil temperature sensor 133 of the oil in the mission case, the shift position of the first main shift mechanism position sensor 137 and the second main shift mechanism 138, and the left and right of the brake connection detection switch 139. The connection condition of the brake pedals 12L and 12R, the traveling speed of the vehicle speed sensor 140, the rotation speed of the PTO rotation sensor 220, the on / off signal of the PTO on / off switch 221 and the changeover signal of the PTO automatic-manual changeover switch 222. It is a changeover signal of the travel-work changeover switch 223 and the like.

The control outputs from the traveling system ECU 120 are the forward switching solenoid 141F, the reverse switching solenoid 141R, the forward / backward boosting solenoid 142, the first main shift first solenoid 207, the first main shift second solenoid 208, and the second main shift second. 1 solenoid 209, 2nd main speed change 2nd solenoid 210, 1st Lo side solenoid 211a, 1st Hi side solenoid 211b, 2nd Lo side solenoid 212a, 2nd Hi side solenoid 212b, 4WD solenoid 213, front wheel acceleration solenoid 214 , Buzzer 215, PTO clutch solenoid 216, and the like.

FIG. 4 is a diagram showing a hydraulic circuit of a tractor. The main pump 250 and the sub-pump 251 operated by engine power suck up the lubricating oil in the mission case 3 through the suction filter 252, and the pressure oil is supplied as the hydraulic oil in the hydraulic circuit. Pressure oil is supplied from the sub pump 251 to the power steering device 253, and the front wheels 4 are operated. The hydraulic oil discharged from the power steering device 253 is used as oil for lubricating and cooling the first high / low clutch 24, the second high / low clutch 25, and the forward / reverse clutch 48, and is returned to the mission case 3. Is done.

Pressure oil is supplied from the main pump 250 to the work machine system hydraulic system 254 and the traveling system hydraulic system 255. When the main speed change lever 15 is operated to the first speed, a current is passed through the first main speed change first solenoid 207 to move the valve, and the pressure oil is discharged from the Lo side oil chamber 256L of the first main speed change cylinder 256. The first synchro change 42 is connected to the first synchro small gear 43 side. Further, a current is passed through the first Lo side solenoid 211a to move the valve, pressure oil is supplied to the oil chamber on the low speed side of the first high / low clutch 24, and the pressure oil is connected to the first low speed gear 26 side.

When the main shift lever 15 is operated from the 1st speed to the 2nd speed, the state of the 1st main shift 1st solenoid 207 does not change, and the 1st synchro change 42 is connected to the 1st synchro small gear 43 side. A current is passed through the first Lo side solenoid 211a and the first Hi side solenoid 211b to move each valve, and pressure oil is supplied to the oil chamber on the high speed side of the first high and low clutch 24 and connected to the first high speed gear 30 side. Will be done.

When the main shift lever 15 is operated from the 2nd speed to the 3rd speed, the current of the 1st main shift 1st solenoid 207 is stopped, the current is passed through the 2nd main shift 1st solenoid 209, and the 1st synchro change 42 Is disconnected, and the second synchro change 36 is connected to the second synchro small gear 37 side. Further, the current of the first Hi side solenoid 211b is stopped, the current is passed through the second Lo side solenoid 212a, each valve is operated, and the pressure oil is supplied to the oil chamber on the low speed side of the second high and low clutch 25. It is connected to the second low speed gear 27 side.

Similarly, in the 4th speed, the 2nd synchro small gear 37 and the 2nd high speed gear 31, in the 5th speed, the 1st synchro large gear 44 and the 1st low speed gear 26, and in the 6th speed, the 1st synchro large gear 44 and the 1st high speed gear. In the 30th and 7th gears, the 2nd synchro large gear 38 and the 2nd low speed gear 27 are connected, and in the 8th gear, the 2nd synchro large gear 38 and the 2nd high speed gear 31 are connected to perform the main shift operation.

The connection pressure of the forward / backward clutch 48 is adjusted at the time of shifting or when the vehicle is started, so that the shifting shock and the shock at the time of starting are suppressed. When the forward / backward lever 14 is moved forward or backward, the forward / backward lever sensor 130 reads the operating position, and a current is passed through the forward switching solenoid 141F or the reverse switching solenoid 141R to move the valve and select the oil passage. To. The pressure of the forward / backward oil passage 142b can be adjusted to an arbitrary pressure by adjusting the flow rate that determines the relief pressure of the forward / backward relief valve 142a according to the magnitude of the current flowing through the forward / backward boosting solenoid 142, which is a proportional solenoid. It has become.

FIG. 5 is a cross-sectional view of the forward / backward clutch 48. The clutch shaft 48a integrated with the forward rotation clutch gear 49 is rotatably supported by the auxiliary transmission shaft 53 by the second bearing B1 and the third bearing B2, and has a plurality of inner clutch plates 48b at the rear portion. doing. The rear portion of the clutch shaft 48a is covered with the clutch case 48d, and the pressing plate 48e fixed to the inside of the front portion of the clutch case 48d is located in front of the front ends of the plurality of inner clutch plates 48b.

A plurality of outer clutch plates 48c are alternately arranged inside the clutch case 48d so as to be sandwiched between the inner clutch plates 48b, and the inner clutch plate 48b has a plurality of teeth on the inner side, so that the clutch is clutched. It rotates integrally with the shaft 48a, and since the outer clutch plate 48c has a plurality of teeth on the outside, it rotates integrally with the clutch case 48d.

Inside the clutch case 48d, a clutch piston 48f is provided at the rear portion of the clutch shaft 48a and is urged rearward by a spring 48g, and the rear portion of the clutch piston 48f has a space for a cylinder portion 48h to which pressure oil is supplied. .. In the forward / backward clutch 48, pressure oil is supplied to the cylinder portion 48h, and when the pressure exceeds the elastic force of the spring 48g, the clutch piston 48f advances, and the inner clutch plate 48b and the outer clutch plate 48c are pressed between the pressing plates 48e. Clutch. The pressured inner clutch plate 48b and outer clutch plate 48c transmit driving force to each other by friction, and the driving force transmitted from the forward rotation clutch gear 49 is transmitted to the clutch case 48d and splined to the clutch case 48d. The fitted auxiliary transmission shaft 53 rotates.

In a state where pressure oil is not supplied to the cylinder portion 48h and no pressure is applied, the clutch piston 48f is pushed backward by the elastic force of the spring 48g, so that the inner clutch plate 48b and the outer clutch plate 48c are not crushed. In this state, since the inner clutch plate 48b and the outer clutch 48c do not transmit the driving force to each other, the PTO clutch 48 is in a state where the power transmission is cut off, and even if the forward clutch gear 49 rotates, the auxiliary transmission shaft 53 does not rotate. .. A reverse clutch gear 50 is provided on the opposite side of the clutch case 48d, and the reverse power is transmitted and cut off in the same configuration.

FIG. 6 is a timing chart showing the movement of each clutch when the main shift is operated from the first speed to the second speed. When the forward / backward lever 14 is moved forward and the main shift lever 15 is operated in the second speed while traveling forward in the first speed, the first high / low clutch 24 is switched from the low speed side to the high speed side, and at this time, the forward / backward clutch is moved forward. The pressure is reduced to a low pressure that does not transmit power once, and the pressure is gradually increased to reduce the shift shock. On the other hand, the second high / low clutch 25 is neutral, the first main speed change cylinder keeps the first synchro change 42 connected to the first synchro small gear 43, and the second main speed change cylinder 257 prepares for the third speed. The second synchro change 36 is connected to the second synchro small gear 37. In this case, the lever operation time t3 includes the operation completion determination time t4 based on the movement speed, and the first corresponding clutch starts to be connected after the lever operation time t3 and the movement time t1 of the clutch piston, and a certain time before t5 (omitted). The forward / backward clutch 48 is turned off 10 milliseconds before) to prevent double biting. Similarly, the forward / backward clutch 48 is adjusted so as to gradually boost the pressure during other shifts and when the vehicle starts, thereby reducing the shock during driving.

FIG. 7 is a perspective view of the periphery of the main speed change lever 15. The main shift lever 15 has a manual shift range of 15s, a neutral range of 15n, and an auto shift range of 15d according to the shift position. In the manual shift range of 15s, it is possible to manually shift from 1st gear to 8th gear. The control unit automatically selects and connects the appropriate gear combination at the shift position. In the neutral range 15n, the power transmission of the multi-speed transmission 150 is cut off, and when the lever is operated in the auto shifting range 15d, the shifting is automatically performed depending on the accelerator condition. The boost adjustment dial 129 is provided on the lever guide on the right side of the driver's seat, and the shift sensitivity can be adjusted by adjusting the boost characteristic of the forward / backward clutch 48.

FIG. 8 is a diagram showing changes in the adjustment position of the boost adjustment dial 129 and the boost curve 300 of the forward / backward clutch 48. When the dial position is in the standard boosting region 129n, the voltage is boosted according to the standard boosting curve 300n stored in advance in the traveling system ECU 120 which is the control unit. When the dial position is the high-voltage side connection pressure adjustment region 129h, the standard booster curve 300n is boosted according to the high-voltage adjustment booster curve 300h translated to the high-voltage side according to the dial position. When the boost adjustment dial 129 is turned to the maximum position, the pressure is adjusted by the maximum pressure line 300 m, and the pressure is not reduced.

When the dial position is the low voltage side connection pressure adjustment region 129l, the standard booster curve 300n is boosted according to the low voltage adjustment booster curve 300l translated to the low voltage side according to the dial position. Further, when the dial position is the connection time adjustment area 129o, the connection time is lengthened from the specified connection time t10 of the standard boost curve 300n to the adjustment connection time t11 according to the dial position, and the connection is adjusted to be loose. It is boosted according to the time-adjusted boost curve 300o.

With these adjustments, for example, in the case of high-load work such as plow plowing, the forward / backward clutch 48 can be set to be quickly engaged, and adjustments can be made so that shifting or starting can be performed smoothly, and during low-load driving such as road driving. It is possible to loosen the connection of the forward / backward clutch 48 and adjust the gear according to preference so that the vehicle can shift and start without shock.

Further, the traveling system ECU 120 acquires the hydraulic oil temperature of the hydraulic clutch by the oil temperature sensor 133, and when the oil temperature is below a certain temperature, the voltage is boosted according to the standard boost curve 300n regardless of the dial position of the boost adjustment dial 129. Will be done. Since the hydraulic oil may be used, for example, which has a characteristic that the viscosity changes significantly around 20 degrees, the clutch may not operate normally if the pressure increasing curve is changed below a predetermined oil temperature. When the oil temperature is below a certain temperature, this can be prevented by not changing the booster curve.

E engine t10 Specified connection time 48 Forward / backward clutch (flood clutch)
120 Traveling system ECU (control unit)
129 boost regulator dial 129n standard boost region 129l low-pressure side connection pressure adjusting region 129h high-pressure side connection pressure adjusting region 129o connection time adjusting region 150 mechanical transmission 300n standard boost curves

Claims (2)

A multi-speed transmission that shifts the rotary drive output from the engine in multiple stages,
A hydraulic clutch that transmits or cuts off the driving force shifted by the multi-speed transmission
It has a control unit that controls the clutch pressure of the hydraulic clutch.
The control unit reduces the clutch pressure to a neutral pressure that does not transmit power at the time of shifting, and then boosts the clutch pressure from the neutral pressure to the connection pressure before depressurization in a specified connection time in a traveling transmission device for a work vehicle having a standard boost curve . ,
With a boost adjustment dial
The adjustment value by the step-up adjustment dial has a high-pressure side connection pressure adjustment region according to the value.
When the control unit is in the high-voltage side connection pressure adjustment region, the standard booster curve is boosted according to the high-voltage adjustment booster curve translated to the high-voltage side according to the dial position.
When the boost adjustment dial is at the maximum position of the high pressure side connection pressure adjustment region , the control unit changes the standard boost curve to shift gears without depressurizing.
Travel transmission device for work vehicles. The adjustment value by the step-up adjustment dial has a low-voltage side connection pressure adjustment area and a connection time adjustment area according to the value.
When the control unit is in the low-voltage side connection pressure adjustment region, the standard boost curve is boosted according to the low-voltage adjustment boost curve that is translated to the low-voltage side according to the dial position.
When it is in the connection time adjustment region, the connection time is changed to the adjustment connection time according to the dial position, and the voltage is increased according to the time adjustment increase curve for boosting the connection pressure before depressurization. Transmission device.

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