JPH08337128A - Travel speed change device for work vehicle - Google Patents

Abstract

PURPOSE: To prevent a clutch slip or stall by lowering the working pressure of a hydraulic clutch after issue of a speed change instruction, but at the preset time before the start of a change in the working pressure of a transmission clutch. CONSTITUTION: A power transmission system of a four-wheel drive agricultural tractor transmits power from an engine 1 to right and left rear wheels 14 via a rear wheel differential 13, and further transmits power divided immediately before the differential 13, to right and left front wheels 19. Also, working pressure of low and high speed clutches 26 and 27 is lowered to raise the working pressure of other transmission clutches 21 to 24 corresponding to a speed change instruction from a transmission operation lever, with the working pressure of transmission clutches 21 to 24 kept lowering on the basis of a speed change instruction. In this case, the working pressure of the clutches 26 and 27 is lowered after issuance of the instruction, but at the preset time before start of the change of working pressure of the clutches 21 to 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling transmission system for a work vehicle.

[0002]

2. Description of the Related Art For example, in a work vehicle such as a four-wheel drive type agricultural tractor, a plurality of multi-plate hydraulic type speed change clutches are arranged in parallel in order to multiply the number of speed change stages in a multiplier manner. There is a transmission provided with a transmission and an auxiliary transmission having a multi-plate hydraulic clutch arranged in parallel. In this case, one of the shift clutches of the main transmission and one of the hydraulic clutches of the auxiliary transmission is based on a shift command from a manually operable shift operating tool provided near the cockpit. By supplying hydraulic oil to one of them and operating those clutches to the transmission side, the power of the engine is transmitted to the rear wheels and the front wheels.

As described above, in order to control the speed change of the speed change device including the main speed change device and the auxiliary speed change device which are the multiple disc hydraulic clutches, the speed change clutch before the speed change command of the main speed change device is based on the speed change command. At the same time as operating
The operating pressure of the shift clutch corresponding to the shift command is gradually increased to operate the shift clutch on the transmission side, and at this time, the working pressure of the hydraulic clutch of the auxiliary transmission is reduced to a predetermined low pressure. As a result, a smooth gear shift operation can be performed with less shock when switching the clutch.

[0004]

When the shift clutch of the main transmission is switched based on the shift command as described above, the operating pressure of the shift clutch to be actuated, which corresponds to the shift command, is changed. In order to avoid a sudden pressure fluctuation that accompanies immediate response to the command, as shown in FIG. 7, an intermediate steady pressure state is once obtained, and then a gradually increasing operation is performed. Time point B
A certain time interval (overlap time TL) is required from 1 to time B2 at which the operating pressure of each shift clutch of the main transmission starts to change.

However, in the prior art, when the operating pressure of the hydraulic clutch of the auxiliary transmission is reduced, as shown in FIG. 7, the operating pressure is changed to a time point B1 when a shift command is issued from the shift operating tool.
Was reduced to a predetermined low pressure P3 (dotted line A4 in FIG. 7). Therefore, in this case, when the overlap time TL is relatively long, the time during which the hydraulic clutch of the auxiliary transmission is set to the predetermined low pressure P3 also becomes longer than necessary, and therefore the torque is increased. This could cause slipping of the clutch and loss of power due to fluctuations.

On the other hand, in the work vehicle having both the main and auxiliary transmissions as described above, the operating pressure is raised in the auxiliary transmission so that smooth transmission operation with less shock can be performed regardless of the load applied to the machine body. When the main transmission is gear-shifted while the vehicle is on, control may be performed to successively calculate and update the predetermined low pressure on the side of the auxiliary transmission based on the engine load measured in real time.

However, particularly when the engine load fluctuation is extremely large during work in the field, it is difficult for the pressure fluctuation of the operating pressure to follow the engine load fluctuation, so that the predetermined low pressure of the auxiliary transmission remains too low. The shift clutch of the transmission may be operated to change gears, which may cause slipping of the clutch and loss of power. The present invention
In view of such circumstances, it is a first object to prevent the occurrence of clutch slippage and power loss by shortening the time for depressurizing the auxiliary transmission to a predetermined low pressure during clutch switching of the main transmission as much as possible. .

Further, according to the present invention, when the shift clutch of the main transmission is switched while the operating pressure of the hydraulic clutch of the sub transmission is reduced to a predetermined low pressure, even if the load of the engine fluctuates during work, the sub transmission can be changed. The second object is to prevent the slip of the clutch and the discontinuity of power by preventing the predetermined low pressure from falling.

[0009]

In order to achieve the above object,
The present invention has taken the following technical means. That is, according to the present invention, the motive power from the engine is a main transmission in which multiple disc hydraulic shift clutches are arranged in parallel, and a sub-transmission in which multiple multiple disc hydraulic clutches are also arranged in parallel. Based on a gear shift command transmitted from a manually operable gear shift operation device to the traveling device on the lower side via the gear shift device, the gear shift clutch of the main gear shift device operating before the transmission of the gear shift command is actuated. When increasing the operating pressure of another shift clutch of the main transmission corresponding to the command while reducing the pressure, the traveling transmission of a work vehicle is designed to reduce the operating pressure of the hydraulic clutch to a predetermined low pressure. In the control, starting to reduce the working pressure of the hydraulic clutch from a time point after the shift command is issued and a predetermined time period before the working pressure of the shift clutch starts to change. Wherein the stage is provided (claim 1).

In this case, it is preferable that the predetermined time is set to the pressure response time of the control valve for supplying / discharging the hydraulic oil to / from the hydraulic clutch of the auxiliary transmission (claim 2). In addition, when the main transmission is gear-shifted while the hydraulic pressure of the sub-transmission is operating, the predetermined low pressure is calculated and updated based on the engine load. It is preferable to provide a low pressure setting means for resetting the predetermined low pressure to the newly obtained predetermined low pressure only when the obtained predetermined low pressure is higher than the already set predetermined low pressure (claim 3).

[0011]

In the present invention, the main transmission 10 and the sub transmission 11 are provided.
In operating the electromagnetic valve of the auxiliary gear shift operation, the operating pressure of one of the hydraulic clutches 26 and 27 of the auxiliary transmission device 11 is changed based on the shift command from the manually operable shift operation tools 61 and 62. While reducing the pressure to a predetermined low pressure P3 (solid line A2 in FIG. 7), the shift clutches 21 to 24 of the main transmission device 10.
Are switched (solid line A1 in FIG. 7 and alternate long and short dash line A3 in FIG. 7).

In this case, the operating pressure of either one of the hydraulic clutches 26 and 27 of the auxiliary transmission 11 is set after the time point B1 when the shift command is issued and at the shift clutches 21 to 2.
A predetermined time T0 from the time B2 at which the operating pressure of No. 4 starts to change
Since the operating pressures of the hydraulic clutches 26 and 27 start to decrease from that time point earlier, the operating pressures of the hydraulic clutches 26 and 27 on the auxiliary transmission device 11 side are immediately reduced from the time point B1 when the shift command is issued (see FIG. 7, the time during which the hydraulic clutches 26, 27 on the side of the auxiliary transmission 11 are set to the predetermined low pressure P3 can be made extremely short (claim 1).

Further, in this case, if the predetermined time T0 is set to the pressure response time of the control valves 38 and 39 for supplying / discharging the hydraulic oil to / from the hydraulic clutches 26 and 27 of the auxiliary transmission device 11, The time during which the 11 hydraulic clutches 26, 27 are set to the predetermined low pressure P3 is minimized (claim 2). On the other hand, the sub-transmission 11 remains unchanged and the main transmission 1
When the predetermined low pressure P3 is sequentially calculated and updated based on the load T of the engine 1 when shifting only 0, when the newly obtained predetermined low pressure P3 ′ is higher than the preset low pressure P3. Only the specified low pressure P3
If the predetermined low pressure P3 'is reset to the newly obtained predetermined low pressure P3', the predetermined low pressure P3 is not always lowered but is set and updated only in the upward direction (claim 3).

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the inside of a mission case 8 of a four-wheel drive type agricultural tractor, which is an example of a work vehicle.
Is transmitted to the PTO shaft 4 via the transmission shaft 2 and the hydraulic multi-plate PTO clutch 3.

Power from the engine 1 is supplied to the forward clutch 5 or the reverse clutch 6, the cylindrical shaft 7, the main transmission 10,
The left and right rear wheels 14 (corresponding to a traveling device) via the first sub transmission 11, the second sub transmission 12, and the rear wheel differential device 13
Is transmitted to On the other hand, the power branched from immediately before the rear wheel differential device 13 is transmitted through the transmission shaft 15, the hydraulic clutch type front wheel transmission device 16, the front wheel transmission shaft 17, and the front wheel differential device 18 to the left and right front wheels 19 (corresponding to a traveling device). Be transmitted to.

The forward clutch 5 and the reverse clutch 6 are hydraulic multi-plate type in which a friction plate and a piston (not shown) are combined, and are operated to the transmission side by supplying hydraulic oil. That is, when the forward clutch 5 is operated to the transmission side,
The power of the engine 1 directly flows from the forward clutch 5 to the cylindrical shaft 7, and the vehicle body moves forward. Further, when the reverse clutch 6 is operated to the transmission side, the power of the engine 1 is transmitted to the cylindrical shaft 7 in the reverse rotation state via the reverse clutch 6 and the transmission shaft 20, and the machine body moves backward.

The main transmission 10 is a hydraulic clutch in which four hydraulic multi-plate type first speed clutches 21, second speed clutches 22, third speed clutches 23 and fourth speed clutches 24 (all of which correspond to speed change clutches) are arranged in parallel. It is configured as a model and is capable of shifting to 4 speeds. By operating one of the 1st to 4th speed clutches 21 to 24 to the transmission side, the power from the cylindrical shaft 7 on the engine 1 side is changed to 4 speeds. It is adapted to be gear-shifted and transmitted to the transmission shaft 25 on the lower side.

The first sub-transmission device 11 is also of a hydraulic clutch type in which two hydraulic multi-plate type low speed clutches 26 and high speed clutches 27 (both are equivalent to hydraulic clutches) are arranged in parallel, and the speed can be changed in two stages. By operating one of the low speed and high speed clutches 26 and 27 to the transmission side,
The power from the transmission shaft 25 on the main transmission device 11 side is transmitted to the second auxiliary transmission device 12 on the lower side after being operated in two stages.

The second auxiliary transmission 12 is of a synchromesh type in which the shift member 53 is slid.
The gear can be shifted in steps, and a gear shift lever 28 described later mechanically shifts gears. Next, the hydraulic circuits for the forward and reverse clutches 5, 6 and the main transmission 10 will be described.

As shown in FIG. 3, forward and reverse clutches 5, 6 are provided in the first oil passage 30 directly connected to the pump 29.
To the electromagnetic proportional valve 35 and the pilot operated switching valves 36a and 37a, and the pilot operated switching valve 31 for the first to fourth speed clutches 21 to 24 of the main transmission 10.
a, 32a, 33a, 34a and the solenoid proportional valve 3 for the low speed and high speed clutches 26, 27 of the first auxiliary transmission 11.
8, 39 (corresponding to a control valve) are connected in parallel.

On the other hand, in the second oil passage 40 branched from the first oil passage 30, a pilot operated switching valve 42a for the hydraulic clutch 41 for the diff lock operation in the front wheel diff device 18 and a diff lock in the rear wheel diff device 13. A pilot operated switching valve 44a for the operating hydraulic clutch 43 and pilot operated switching valves 47a, 48a for the standard clutch 45 and the speed increasing clutch 46 (see FIG. 1) of the front wheel transmission 16 are connected in parallel. ing.

Each switching valve 31a-34a, 36a, 37
a, 42a, 44a, 47a, and 48a are urged to the oil discharge side (transmission cut-off side) by springs, and are operated to the supply side (transmission side) by supplying pilot hydraulic oil as described later. To be done. A pilot oil passage 50 is branched from the first oil passage 30 via a pressure reducing valve 49.
0 is the switching valves 31a to 34a, 36a, 37a, 42a,
44a, 47a, and 48a are connected to the operation portions of the switching valves, and the solenoid operated valves 31b, 32b, and 33 are connected to the operation portions of the respective switching valves.
b, 34b, 36b, 37b, 42b, 44b, 47
b and 48b are connected.

Each solenoid operated valve 31b-34b, 36b, 3
7b, 42b, 44b, 47b, 48b are urged to the oil discharge side (transmission cutoff side) by springs, and when these are electrically operated to the supply side, the pilot operating oil causes the switching valve 31a.
~ 34a, 36a, 37a, 42a, 44a, 47a,
It is supplied to the operation part of 48a, and these are operated to the supply side (transmission side).

Next, the construction of the operation parts of the forward and reverse clutches 5, 6, the main transmission 10, etc. will be described. As shown in FIGS. 2 and 3, an opening / closing valve 51 capable of draining pilot working oil from the operation portion of the switching valves 36a, 37a of the forward and reverse clutches 5, 6 is provided, and the opening / closing valve 51 is closed by a spring. Biased to the side. Also, in the lower front of the cockpit,
Clutch pedal 5 for mechanically operating the open / close valve 51 to the open side
2 is provided, and a position sensor 68 for detecting the operation position of the clutch pedal 52 is provided at the pivot portion of the clutch pedal 52.

Further, at the base of the steering wheel 58 of the front wheel 19, there is provided a forward / backward lever 59 for emitting an electric forward signal and a backward signal, and the accelerator position of the engine 1 is artificially placed in the lower front of the cockpit. An accelerator pedal 69 is provided for changing the operation. A position sensor 70 that detects an operation position of the accelerator pedal 69 is provided at a pivot portion of the accelerator pedal 69.

As shown in FIG. 2, the speed change lever 28 is swingably supported around the horizontal axis of the control section of the machine body, and the shift member 53 of the second auxiliary speed change device 12 (see FIG. 1).
Shift fork 54 and gear shift lever 2 for sliding
8 and 8 are mechanically interlocked by a linkage mechanism 55. Therefore, the second auxiliary transmission device 12 can be operated to change gears by switching the speed change lever 28 between the neutral stop position N, the low speed position L, and the high speed position H.

A lock pin 56 is provided in the middle of the speed change lever 28 so as to be able to move outward and backward. An operation pin 57 for operating the lock pin 56 to move in and out is an upper inner surface side of the speed change lever 28 (operator). Side). The lock pin 56 is biased by a spring (not shown) so as to project to the fixed position on the right side of the drawing in FIG. 2 (the operation pin 57 is also biased to the protruding side on the left side of the drawing), and the lock pin 56 is By engaging with the guide plate 60 on the fixed side, the shift lever 2
8 is fixed at each of the neutral stop position N, the low speed position L and the high speed position H.

When the operation pin 57 is pushed in, the lock pin 56 is retracted to the fixed release position on the left side of the drawing, and the gear shift lever 28 is moved to the neutral stop position N and the low speed position L.
And it can be operated to the high speed position H. A position sensor 63 that detects the operation position of the shift lever 28 is provided at the base of the shift lever 28. A shift up button 61 and a shift down button 6 are provided on the left lateral side of the speed change lever 28.
Two (both are equivalent to gear shift operation tools) are arranged above and below, and as described later, when the shift up button 61 and the shift down button 62 are pressed once, one shift up signal and one shift down signal (both are (Corresponding to a gear shift command) is started, and the main and first auxiliary transmissions 1 of FIG.
A gear change operation of 0 and 11 is performed.

As shown in FIG. 2, the gear shift positions (1st to 8th gears) of the main and first auxiliary transmissions 10 and 11 are provided in the control section of the airframe.
7-segment speed change display portion 64 for displaying the speed), and a forward lamp 6 for displaying which of the forward and reverse clutches 5, 6 is operated by the forward / reverse lever 59 to the transmission side.
5 and the reverse lamp 66, and the neutral stop lamp 67 indicating that the speed change lever 28 is operated to the neutral stop position N.
And are provided.

Further, as shown in FIG. 3, a pressure sensor 74 for detecting whether or not the operating pressure of the forward and reverse clutches 5, 6 has reached a predetermined pressure on the transmission side is provided. Upon detection of 74, the forward and reverse lamps 65 and 66 are turned on. Next, the shift lever 28
Shift up button 61 and shift down button 62
The shift operation and the abnormality detection in this shift operation will be described.

As shown in FIG. 4, first, the presence or absence of abnormality is detected in the solenoid proportional valve 35 for the forward and reverse clutches 5 and 6 of FIG. 3 (step S1). An operating current is sent (step S2). Next, when the forward / backward lever 59 is operated to the forward position F (step S3), an operation current is sent to the electromagnetic operation valve 36b of FIG. 3 (step S5), and the switching valve 36a is operated to the supply side. The forward clutch 5 is operated to the transmission side, and the forward lamp 65 is turned on (step 6).

On the contrary, when the forward / reverse lever 59 is operated to the reverse position R (step S3), the solenoid operated valve 3 shown in FIG.
An operating current is sent to 7b (step S8), and the switching valve 37
a is operated to the supply side, the reverse clutch 6 is operated to the transmission side, and the reverse lamp 66 is turned on (step S
9), the buzzer 71 of FIG. 2 operates intermittently (step S10).

In steps S1, S4 and S7 in the above state, the solenoid proportional valve 3 for the forward and reverse clutches 5 and 6
5 and the solenoid operated valves 36b and 37b, when an abnormality such as a short circuit of the operating current is detected, a lower case "c" is displayed and blinks in the lower half segment of the gear shift display section 64 in FIG. 2 (step S11). ), The buzzer 71 operates continuously (step S12). As a result, the operator recognizes that an abnormality has occurred in the operation system of the forward and reverse clutches 5 and 6.

As shown in FIG. 1, the main transmission 10 is capable of shifting in four stages, and the first auxiliary transmission 11 is capable of shifting in two stages. Therefore, the main transmission and the first auxiliary transmissions 10, 11 are arranged. It is possible to shift gears in 8 steps. In this case, the first to fourth speed clutches 21 to 24 of the main transmission 10 are operated with the low speed clutch 26 of the first auxiliary transmission 11 being operated to the transmission side.
Correspond to the shift positions of the 1st to 4th speeds, and the 1st to 4th speed clutches 21 to 21 of the main transmission 10 are in the state where the high speed clutch 27 of the first auxiliary transmission 11 is operated to the transmission side.
24 corresponds to the shift position of the fifth speed to the eighth speed.

As shown in FIG. 3, these operating pressures are transmitted to the first to fourth speed clutches 21 to 24 of the main transmission device 10, and the low speed and high speed clutches 26 and 27 of the first auxiliary transmission device 11, respectively. Each pressure sensor 74 is provided with a pressure sensor 74 for detecting whether or not a predetermined pressure on the side has been reached.
Is detected, the current gear shift positions (1st to 8th gear) of the main and first auxiliary transmissions 10 and 11 are detected, and the detected gear shift positions are displayed on the gear shift display section 64 (step S1).
3).

Next, the speed change lever 28 of FIG.
Alternatively, in the state where the shift lever 28 is operated to the high speed position H (step S14), the shift up button 61 of the shift lever 28 is pressed.
Alternatively, the shift down button 62 is pressed once to operate (steps S15 and S16). Then, as shown in FIG. 5, when the shift-up button 61 is pressed, the electromagnetic operation valves 31b to 34b for the main transmission 10 at the gear shift position one step higher than the current gear shift position are in an abnormal state. The presence / absence of the high speed clutch 2 in the first auxiliary transmission device 11 is detected during the shift operation from the 4th speed shift position to the 5th speed shift position.
The presence or absence of abnormality of the solenoid proportional valve 39 for 7 is also detected at the same time (step S17).

On the contrary, when the shift down button 62 is pressed, the electromagnetically operated valves 31b to 3b for the main transmission 10 at the shift position one step lower than the current shift position.
The presence or absence of abnormality of 4b is detected, and the presence or absence of abnormality of the solenoid proportional valve 38 for the low speed clutch 26 in the first subtransmission device 11 is also detected at the same time during the shift operation from the 5th gear position to the 4th gear position. (Step S17).

If no abnormality is detected in the above-mentioned state (step S18), the predetermined low pressure P3 (see FIG. 7) of the low speed or high speed clutches 26 and 27 operated on the transmission side in the first auxiliary transmission device 11 is detected. It is obtained in real time as described later (step S19). Then, the solid line A in FIG.
As shown in FIG. 1, when the shift-up button 61 is pressed at a certain time point B1, the electromagnetic operation valves 31b to 34b for the main transmission device 10 at the gear shift position which is one speed higher than the current gear shift position. Operation current is started to be supplied, and conversely, the shift down button 6
When 2 is pressed, the operating current starts to be supplied to the electromagnetically operated valves 31b to 34b for the main transmission device 10 at the speed change position one step lower than the current speed change position (step S20).

In this case, in order to avoid a sudden pressure fluctuation of the low speed or high speed clutch 26.27 due to the immediate response to the shift up signal or the shift down signal, an intermediate steady pressure state is once obtained and then gradually. Is operated ascending. Therefore, the main transmission 10 corresponding to the shift signal
The operating pressures of the first to fourth speed clutches 21 to 24 are temporally constant from a time point B1 when there is a shift-up signal or a shift-down signal to a time point B2 when the operating pressure of each shift clutch of the main transmission device starts to change. The distance (overlap time TL) is set.

Further, as described above, the first to fourth speed clutches 21 to 21 on the one-speed high speed side or the one-speed low speed side in the main transmission 10 are described.
While the operating pressure of 24 is increased to the operating pressure P1 in the transmission state by the electromagnetically operated valves 31b to 34b, as shown by the alternate long and short dash line A3 in FIG. Time point B when the operating pressure of the first to fourth speed clutches 21 to 24 before the push operation of the button 62 elapses from the time point B1 by the overlap time TL.
From 2, the solenoid operated valves 31b to 34b are operated to lower the operating pressure P1 in the transmission state to zero (step S2).
2).

Then, as described above, the second auxiliary transmission 1
When the clutch is switched on the side of the main transmission device 10 when 2 is in the low speed or high speed position L or H, the solid line A2 in FIG. As shown, the first auxiliary transmission 11
With the solenoid proportional valves 38, 39 of the low speed and high speed clutches 26, 27 operated on the transmission side, the operating pressure of the low speed or high speed clutches 26, 27 operated on the transmission side starts from the operating pressure P2 in the transmission state. The pressure is reduced to the predetermined low pressure P3 (step S21).

In this case, after the time point B1 at which the shift-up signal or the down-shift signal is issued, and after the time point B2 at which the operating pressure of the speed change clutches 21 to 24 on the main transmission device 10 side starts to change. From time B5 before the predetermined time T0, the hydraulic clutch 2 on the side of the first auxiliary transmission 11 is
Start to reduce the working pressure of 6, 27 (corresponding to the controller).

Therefore, conventionally, when the operating pressure of the hydraulic clutches 26, 27 on the side of the first auxiliary transmission 11 is immediately reduced from the time point B1 when the shift-up signal or the shift-down signal is issued (see FIG. 7). Compared to the dotted line A4), the time during which the hydraulic clutches 26 and 27 are set to the predetermined low pressure P3 becomes shorter. Further, in the case of this embodiment, the predetermined time T0
Is programmed into the controller as a constant setpoint,
The pressure response time of the solenoid proportional valves 38 and 39 on the side of the first auxiliary transmission 11 is defined as the pressure response time, which means the target operating pressure (output) after the proportional valves 38 and 39 receive an electric signal. ) Means the time until it is obtained. Therefore, if the predetermined time T0 is set to the pressure response time of the proportional valves 38 and 39, the time for which the hydraulic clutches 26 and 27 are set to the predetermined low pressure P3 can be minimized.

The pressure response time is determined by the solenoid proportional valve 3
Although it depends on the type of 8, 39, it can be set to about 0.2 seconds. On the other hand, as described above, the operating pressures of the low speed and high speed clutches 26 and 27 of the first auxiliary transmission 11 are set to the predetermined low pressure P.
While shifting to 3, the shift clutches 21 to 24 of the main transmission 10.
In the case of performing the gear shift operation for switching the gear shift operation from the 4th gear shift position to the 5th gear shift position, the operating pressure of the low speed clutch 26 of the first auxiliary transmission device 11 is reduced to zero and the high speed clutch 27 Working pressure from zero to low pressure P
It is operated to rise to 3. Conversely, from the 5th gear position to 4
When performing a gear shift operation to a high speed gear shift position, the first auxiliary transmission 1
The operating pressure of the high speed clutch 27 of No. 1 is dropped to zero, and the operating pressure of the low speed clutch 26 is increased from zero to a predetermined low pressure P3.

Therefore, between the fourth speed and the fifth speed in which the low speed clutch 26 and the high speed clutch 27 of the first auxiliary transmission 11 are switched, the setting of the predetermined low pressure P3 obtained by the method described later is once cleared to zero. It will be. Next, the operating pressure of the low speed or high speed clutches 26, 27 of the first auxiliary transmission device 11 maintained at the predetermined low pressure P3 is the solid line A in FIG.
2 time point B3 to time point B4, the solenoid proportional valve 3
It is gradually raised by 8,39, and then
The working pressure of the low speed or high speed clutch 26, 27 reaches the working pressure P2 (step S23). In this case, from the time point B3 to the time point B4 of the solid line A2 in FIG. 7, the characteristic of increasing the operating pressure of the low speed or high speed clutches 26 and 27 is set for each shift position, and the low speed side (first speed side) shift is performed. The position is such that the operating pressure from time B3 to time B4 is rapidly increased in a short time.

As described above, the shift up button 6
Since one shift operation by pressing the 1 or the shift down button 62 is finished, when the shift operation is finished, the shift position after the shift operation is displayed on the shift display section 64 (step S24), and the buzzer 71 is pressed once. And the operator is informed of the end of the gear shifting operation (step S25). The shift operation as described above is not continuously performed even if the shift-up button 61 or the shift-down button 62 is continuously pressed, and the shift-up button 61 or the shift-down button 62 is once returned and then pressed again. Otherwise, the next one shift operation will not be performed.

In response to the normal shift operation as described above, in step S18 of FIG.
Electromagnetic operation valves 31b to 34b and electromagnetic proportional valves 38, 3 that are scheduled to be shifted (operation current is to be supplied) in the auxiliary transmission device 11.
If an abnormality such as a short-circuit of the operating current is found in 9, the abnormal gear position is displayed on the gear shift display portion 64, and this display blinks for a predetermined time (for example, about 10 seconds) (step S26). ).

Then, the electromagnetically operated valves 31b to 34b and the electromagnetic proportional valve 3 which are in the abnormal gear shift schedule (scheduled to supply the operating current).
The operation current is not supplied to 8, 39, and the shift position before the push operation of the shift up button 61 or the shift down button 62 is left, and the shift position before the push operation is displayed on the shift display portion 64. (Step S27). If an abnormality is found in step S18 of FIG.
When 8 is operated to the low speed position L or the high speed position H, the gear shift operation beyond the abnormal gear shift position cannot be performed. However, when the gear shift lever 28 is returned to the neutral stop position N, the abnormal gear shift position is set. It is possible to perform a gear shifting operation beyond the range. Next, this gear shifting operation will be described.

When an abnormality is found in step S18 of FIG. 5, the operator operates the speed change lever 28 from the low speed position L or the high speed position H to the neutral stop position N as will be described later (step S14 of FIG. 4). As a result, the neutral stop lamp 67 in FIG. 2 lights up (step S28 in FIG. 6), and if the shift up button 61 or the shift down button 62 is pressed in this state (steps S29, S30), the power is supplied before the pressing operation. Solenoid operated valve 31b operated to the side
The operation current to 34b is cut off (step S31), and the operation current is supplied to the electromagnetic operation valves 31b to 34b that are one speed higher or one speed lower than the current gear position (steps S32 and S33). .

In this case, the electromagnetically operated valve 31b after the shifting operation is performed.
If there is no abnormality in ~ 34b, the solenoid operated valves 31b ~ 3
The current gear shift position corresponding to 4b is displayed on the gear shift display portion 64 (steps S34 and S35), and the buzzer 71 operates only once (step S37). On the contrary, if there is an abnormality in the electromagnetically operated valves 31b to 34b after the gear shift operation, the current gear shift position corresponding to the electromagnetically operated valves 31b to 34b is displayed on the gear shift display section 64 and this display blinks (step S3).
4, S36), the buzzer 71 operates only once (step S37).

When the shift up button 61 or the shift down button 62 is further pressed, steps S37 to S14 (see FIG. 4), S28, S2 are performed.
Returning to 9, the shift operation as described above is performed. As a result, the shift operation can be performed beyond the abnormal shift position.
When the shift lever 28 is operated to the neutral stop position N as described above, the shift operation as described above is continuously performed if the shift up button 61 or the shift down button 62 is continuously pressed. And in this state,
Since the second auxiliary transmission device 12 is operated to the neutral stop position, the first auxiliary device as shown by the solid line A2 in FIG. 7 is used except for the speed change operation between the fourth speed position and the fifth speed position. The operating pressure on the side of the transmission 11 is not controlled.

More specifically, the above-described gear shift operation and abnormality detection will be described. For example, when a gear shift operation is performed from the second gear shift position to the third gear shift position, if there is an abnormality in the third gear shift position, a shift up operation is performed. When the button 61 is pressed, the gear shift display portion 64 changes from the gear shift position display of the second speed to the gear shift position display of the third speed, and the gear shift position display of the third speed blinks.
As a result, the operator can recognize that there is an abnormality in the gear shift position of the third speed, the gear shift display unit 64 then returns to the display of the gear shift position of the second gear, and the actual gear shift position is also the second gear. It remains in the gear position.

On the contrary, for example, if there is an abnormality in the shift position of the 3rd speed when shifting from the shift position of the 4th speed to the shift position of the 3rd speed, when the shift down button 62 is pressed, the shift display portion 64 displays the 4th speed The display of the shift position of is changed to the display of the shift position of the third speed, and the display of the shift position of the third speed blinks.
As a result, the operator can recognize that there is an abnormality in the gear shift position of the third speed, and the gear shift display unit 64 then returns to the display of the gear shift position of the fourth gear, and the actual gear shift position is also the fourth gear. It remains in the gear position.

Next, in the above-mentioned state, the shift lever 28 is operated from the low speed position L or the high speed position H to the neutral stop position N.
When the shift-up button 61 is pressed in this manner, the gear shift display portion 64 changes from displaying the gear shift position of the second speed to displaying the gear shift position of the third speed, and the display of the gear shift position of the third speed blinks. Further, when the shift-up button 61 is pressed, the shift display portion 64 displays the shift position of the fourth speed, and the actual shift position is also shifted to the shift position of the fourth speed.

On the contrary, when the shift down button 62 is pressed, the gear shift display portion 64 displays the shift position of the 4th speed from the 3rd position.
The display of the shift position of the third speed is changed, and the display of the shift position of the third speed blinks. Further, when the shift down button 62 is pressed, the gear shift display portion 64 displays the gear shift position of the second gear, and the actual gear shift position is also shifted to the gear shift position of the second gear.

Next, the first step in step S19 of FIG.
A method of setting the predetermined low pressure P3 for the low speed or high speed clutches 26, 27 of the auxiliary transmission device 11 will be described. As shown in FIG. 8, the current operation position of the accelerator pedal 69 is detected by the position sensor 70 (step S42), and the no-load of the engine 1 corresponding to the current operation position of the accelerator pedal 69 (accelerator position of the engine 1). Rotational speed N1
Is estimated based on the graph of FIG. 9 previously obtained for the engine 1, and the rotation speed N1 is gradually calculated (step S43).

Next, the current engine speed N2 of the engine 1 is detected by the engine speed sensor 72 shown in FIGS. 1 and 2 (step S44), and the difference between the engine speed N1 when there is no load and the current engine speed N2. N3 is calculated (step S45), and the current shift positions (1st speed to 16th speed) of the main transmission 10, the first and second auxiliary transmissions 11 and 12 (however, the shift-up button 61 and the shift-down button 62 are operated). (Before pushing operation)
Is detected (step S46).

As a result, based on the difference N3 between the rotational speeds N1 and N2 and the current shift position (1st speed to 16th speed), as shown in FIG.
Thus, the load T applied to the engine 1 is calculated (step S47), and based on this load T, the predetermined low pressure P3 'of step S19 of FIG. 5 and the solid line A2 of FIG. 7 is set (step S48). In this case, as shown in FIG. 10, it is determined that the larger the difference N3 between the unloaded engine speed N1 and the current engine speed N2, the larger the load T on the engine 1, and the predetermined low pressure indicated by the solid line A2 in FIG. Since P3 is set to a high value (the side close to the operating pressure P2 in the transmission state), conversely, the smaller the difference N3, the smaller the load on the engine 1 is determined, and the predetermined low pressure indicated by the solid line A2 in FIG. P3 is set to a low value (zero side).

Further, as shown in FIG. 10, it is judged that the load applied to the engine 1 is larger as the current shift position is on the lower speed side (first speed side), and the predetermined low pressure P3 indicated by the solid line A2 in FIG. It is set to a high value (the side close to the operating pressure P2 in the transmission state). On the other hand, when the accelerator pedal 69 is operated,
The rotation speed of the engine 1 changes a little later than this. Therefore, when the accelerator pedal 69 is operated as shown in FIG. 8 (step S41), the rotation speed N1 calculated last time is calculated.
The difference N3 from N2 is continuously used as it is (step S49), the current gear position (1st speed to 16th speed) is detected (step S50), the load T applied to the engine 1 is calculated, and the predetermined low pressure is applied. P3 is set (steps S51, 52).

After the accelerator pedal 69 is operated, if it is determined that the rate of change of the engine speed N1 of the engine 1 is less than or equal to the predetermined value D and the change of the engine speed N1 is stable (step S53), the process proceeds from step S41. It returns to step S42. Further, particularly when the load variation of the engine 1 is large during the work in the field, it is difficult for the pressure variation of the operating pressure of the valve to follow the load variation of the engine 1.
If the load T applied to the vehicle suddenly rises from a low point, the predetermined low pressure P3 of the low speed or high speed clutches 26, 27 of the first auxiliary transmission 11 is temporarily too low, and therefore, The clutch may slip or the power may be cut off.

Therefore, in this embodiment, when the predetermined low pressure P3 is sequentially updated based on the load T of the engine 1 as described above, the newly obtained predetermined low pressure P3 'is obtained from the preset low pressure P3. Only when it is also high (step S54), the predetermined low pressure P3 is reset to the newly obtained predetermined low pressure P3 '(step S54).
55).

Therefore, as shown in FIG. 12, when the load T of the engine 1 fluctuates while the predetermined low pressure P3 of the low speed or high speed clutches 26 and 27 of the first auxiliary transmission 11 is set, When the load T increases, the predetermined low pressure P3 increases, but even when the load T increases, the predetermined low pressure P3 does not decrease. Therefore, the predetermined low pressure P3 does not always decrease and the setting is updated only in the increasing direction. .

As described above, the predetermined low pressure P3 is repeatedly set and updated, and when step S19 of FIG. 5 is reached, the latest stored predetermined low pressure P3 is reached.
3 is taken in. Next, the shift lever 2 shown in FIG.
The shift operation to the neutral stop position N, the low speed position L, and the high speed position H of 8 will be described.

As described above, the speed change lever 28 is fixed at the neutral stop position N, the low speed position L, or the high speed position H by the lock pin 56, and when the speed change lever 28 is operated to another position. It is necessary to push the operation pin 57 of the shift lever 28 to release the lock pin 56.

In this case, as shown in FIG. 11, when the speed change lever 28 is operated to the low speed position L, for example,
When the operation pin 57 is pressed (ON) (time point B1)
1), the lock pin 56 is removed from the guide plate 60 and operated. At the same time, an operation signal from the operation pin 57 operates the forward or reverse clutches 5 and 6 to the transmission cutoff side by the electromagnetic operation valves 36b and 37b of FIG. 3, and the electromagnetic proportional valves 38 and 39 cause the first auxiliary transmission device. The 11 low speed or high speed clutches 26 and 27 are operated to the transmission cutoff side.

As a result, the speed change lever 28 is moved from the low speed position L to the neutral stop position N while the operation pin 57 is being pressed.
To operate. In this case, as shown in FIG.
Since the first sub-transmission device 11 immediately above the second sub-transmission device 12 which is operated to shift in 8 is operated in the transmission cutoff state, the shift operation to the neutral stop position N by the shift lever 28 is facilitated. You can do it.

After operating the speed change lever 28 to the neutral stop position N, when the operator releases the operating pin 57 and returns it (OFF) (time point B12), the lock pin 56 moves the speed change lever 28 to the neutral stop position N. At the same time it is fixed
The forward or reverse clutches 5, 6 are immediately operated to the transmission side by the solenoid operated valves 36b, 37b and the solenoid proportional valve 35 in FIG. 3, and the first auxiliary transmission device 11 is operated by the solenoid proportional valves 38, 39.
The low speed or high speed clutches 26 and 27 are immediately operated to the transmission side.

Next, when the speed change lever 28 is operated to the neutral stop position N, the operation pin 57 is pushed (ON) (time point B13), and the lock pin 56 is removed from the guide plate 60 as described above. The forward or reverse clutches 5 and 6 and the low speed or high speed clutches 26 and 27 of the first auxiliary transmission device 11 are operated to the transmission interruption side. As a result, for example, when the speed change lever 28 is operated from the neutral stop position N to the high speed position H while the operation pin 57 is being pressed, the first auxiliary transmission device immediately above the second auxiliary transmission device 12 in the same manner as described above. Since 11 is operated in the transmission cutoff state, the speed change operation to the high speed position H by the speed change lever 28 can be easily performed.

After operating the speed change lever 28 at the high speed position H, when the operator releases the operating pin 57 and returns it (OFF) (time point B14), the lock pin 56 fixes the speed change lever 28 at the high speed position H. At the same time, the solenoid proportional valves 38, 39 immediately operate the low speed or high speed clutches 26, 27 of the first auxiliary transmission 11 to the transmission side. On the other hand, the forward or reverse clutches 5 and 6 are gradually operated to the transmission side as described below.

As shown in FIG. 1, a rotation speed sensor 73 for detecting the rotation speed of the cylindrical shaft 7 between the forward and reverse clutches 5, 6 and the main transmission 10 is provided, and the operation pin 57 is provided.
From the time point B14 when the return operation is performed, the rotation speed sensor 73
The operating pressure of the forward or reverse clutches 5 and 6 is increased by the solenoid proportional valve 35 of FIG. 3 so that the rate of increase of the detected value does not exceed the set value, and is operated toward the transmission side (time B15). ).

It is assumed that the clutch pedal 52 shown in FIGS. 2 and 3 is depressed to operate the forward / reverse clutches 5 and 6 by the open / close valve 51 into a half-clutch state. in this case,
As shown in FIG. 1, since the rotation speed sensors 72 and 73 are arranged on the lower side and the upper side of the forward and reverse clutches 5 and 6, respectively, the forward and reverse clutches are different depending on the difference between the detection values of the both rotation speed sensors 72 and 73. The power of the engine 1 absorbed by 5 and 6 is calculated, and when the integrated value of the absorbed power reaches a set value, it is determined that seizure will occur in the forward or reverse clutches 5 and 6, and the buzzer 71 is set at a short interval. Is operated intermittently to notify the operator.

The present invention is not limited to the above embodiment. For example, in FIG. 2, the shift up button 61
Although the shift down button 62 and the shift down button 62 are separately provided, the shift up signal and the shift down signal are transmitted by operating one shift switch (not shown) to the shift up side and the shift down side. It may be configured to.

Further, in FIG. 1, a main clutch having forward-reverse clutches 5 and 6 is provided on the upper side of the main transmission device 10.
Although the forward-reverse 16-speed transmission in which the second auxiliary transmission 12 is provided on the lower side of the auxiliary transmission 11 is shown, the present invention is not limited to such an arrangement and is configured by a multi-plate hydraulic clutch. It can be widely adopted in a transmission in which the first auxiliary transmission 11 also composed of a multi-plate hydraulic clutch is arranged below the main transmission 10.

[0074]

As described above, according to the present invention,
When the clutches of the main transmission 10 are switched, the time during which the hydraulic clutches 26 and 27 on the side of the auxiliary transmission 11 are set to the predetermined low pressure P3 can be extremely shortened, so that the slippage of the clutch and the occurrence of power loss can be prevented. It is possible (Claim 1).

According to the second aspect of the present invention, the hydraulic clutches 26, 27 of the auxiliary transmission 11 have the predetermined low pressure P3.
Since the time set for can be minimized, the occurrence of clutch slippage and disengagement of power can be prevented more completely. Furthermore,
According to the third aspect of the present invention, when the predetermined low pressure P3 is sequentially calculated and updated based on the load T of the engine 1, the predetermined low pressure P3 does not always fall and the setting is updated only in the upward direction. Even if the load of the engine 1 varies during the work, the situation where the predetermined low pressure P3 of the auxiliary transmission device 11 is too low is avoided in advance, so that the slip of the clutch and the discontinuance of power can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a transmission system in a mission case.

FIG. 2 is a diagram showing a linked state of a shift lever and a second auxiliary transmission device, a shift display portion, and a linked state of each portion.

FIG. 3 is a hydraulic circuit diagram of a main transmission, a first auxiliary transmission, and the like.

FIG. 4 is a diagram showing a first half flow of control of gear shift operation and abnormality detection by a shift up button and a shift down button when a shift lever is operated to a low speed position or a high speed position.

FIG. 5 is a diagram showing a second half flow of control of gear shift operation and abnormality detection by a shift up button and a shift down button when the shift lever is operated to a low speed position or a high speed position.

FIG. 6 is a diagram showing a flow of control of gear shift operation and abnormality detection by a shift up button and a shift down button in a state where the gear shift lever is operated to a neutral stop position.

FIG. 7 is a diagram showing the states of the main and first auxiliary transmission devices at the time of a shift operation with a shift up button and a shift down button in a state where the shift lever is operated to a low speed position or a high speed position. .

8 is a predetermined low pressure (P) on the side of the first auxiliary transmission in FIG.
It is a figure which shows the flow of the setting of 3).

9 is a predetermined low pressure (P) on the side of the first auxiliary transmission in FIG.
It is a figure which shows the relationship between the accelerator position of an engine, and the engine speed at the time of no load of an engine at the time of setting of 3).

10 shows the relationship between the load on the engine and the difference between the engine speed with no load and the current engine speed when the predetermined low pressure (P3) on the side of the first auxiliary transmission in FIG. 7 is set. It is a figure.

FIG. 11 is a diagram showing a state of a forward or reverse clutch and a state of a first auxiliary transmission when a second auxiliary transmission is gear-shifted by a shift lever and an operation pin.

FIG. 12 is a diagram showing changes in engine load and changes in a predetermined low pressure (P3).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 10 main transmission device 11 (first) auxiliary transmission device 14 traveling device (rear wheel) 19 traveling device (front wheel) 21 shift clutch (1st speed clutch) 22 shift clutch (2nd speed clutch) 23 shift clutch (3rd speed clutch) ) 24 speed change clutch (4th speed clutch) 26 hydraulic clutch (low speed clutch) 27 hydraulic clutch (high speed clutch) 38 control valve (electromagnetic proportional valve) 39 control valve (electromagnetic proportional valve) 61 speed change operation tool (shift up button) 62 speed change Operation tool (shift down button) B1 time point B2 time point B5 time point P3 specified low pressure P3 'specified low voltage T load

Claims (3)

[Claims] 1. A main transmission (10) in which power from an engine (1) is the same as that of a main transmission (10) formed by arranging multiple disc hydraulic type shift clutches (21) (22) (23) (24) in parallel. It is transmitted to the traveling device (14) (19) on the lower side through an auxiliary transmission (11) in which hydraulic clutches (26) (27) of a multi-plate hydraulic type are arranged in parallel and are operated artificially. Based on a gear shift command from a possible gear shift operation tool (61) (62), the gear shift clutch (21) (22) of the main transmission device (10) that is operating before the transmission of the gear shift command.
(23) Another shift clutch (2) of the main transmission (10) corresponding to the command while reducing the operating pressure of (24).
1) When increasing the working pressure of (22) (23) (24), the travel shift of the work vehicle is such that the working pressure of the hydraulic clutches (26) (27) is reduced to a predetermined low pressure (P3). In the device, after the time point (B1) when the shift command is issued and at the shift clutches (21) (22) (23) (2).
Control means is provided for starting to reduce the operating pressure of the hydraulic clutches (26) and (27) from a time point (B5) that is a predetermined time (T0) before the time point (B2) when the operation pressure of 4) starts to change. Work vehicle running transmission. 2. The auxiliary transmission (1) for a predetermined time (T0).
The traveling speed change device for a work vehicle according to claim 1, wherein the pressure response time of a control valve (38) (39) for supplying and discharging hydraulic oil to the hydraulic clutch (26) (27) of 1) is set. 3. A hydraulic clutch (2) of the auxiliary transmission (11).
6) When the main transmission (10) is being shifted while the operating pressure is rising at (27), the predetermined low pressure (P3) is sequentially calculated based on the load (T) of the engine (1). In updating, the predetermined low pressure (P3 ′) is newly obtained only when the newly obtained predetermined low pressure (P3 ′) is higher than the preset low pressure (P3). 3. The traveling speed change device for a work vehicle according to claim 1, further comprising low pressure setting means for resetting the pressure.