JPH07332483A - Running gear shift structure of working vehicle - Google Patents

Abstract

PURPOSE:To suppress the generation of a shock when, during a gear shift when a load exerted on an engine is high, a gear shift clutch is operated to the transmission side after completion of a gear shift. CONSTITUTION:A transmission clutch E is provided to take out a power from a place situated upper stream from a mechanical gear shifter A and a gear shift clutch 19 and transmit it to a place situated downstream from the mechanical gear shifter A and the gear shift clutch 19. Along with the starting of a gear shift by actuators T1 and T2, the gear shift clutch 19 is operated to the transmission cut off side, the transmission clutch E is operated to the transmission side, and lowering of the running speed of a machine body is suppressed. In this case, a load exerted on an engine is detected and the working pressure of the transmission clutch E is automatically varied and regulated so that the more a load is increased, the more a power transmitted by the transmission clutch E is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling speed change structure for a work vehicle equipped with a gear speed change device, which automatically operates a speed change clutch for traveling speed change to a transmission disengagement side based on an operation command for speed change. The present invention relates to a gear shift device provided with a structure for performing a gear shift operation and automatically again operating a gear shift clutch to a transmission side.

[0002]

2. Description of the Related Art An example of a traveling speed change structure for a work vehicle as described above is disclosed in Japanese Patent Laid-Open No. 3-209056. With this structure, the engine (1 in FIG. 4 of the publication)
On the lower side of the actuator, the actuator (1 in FIG.
1, a gear shift device (A in FIG. 4 of the publication) which is operated by a gear shift, and a shift clutch for traveling gear shifting (3 in FIG. 4 of the publication) are arranged in series. . As a result, the shift clutch is automatically operated to the transmission interruption side based on the operation command for shifting, and the gear shift device is shifted by the actuator. When the shift operation by the actuator is completed, the shift clutch is automatically operated to the transmission side.

[0003]

Work vehicles equipped with the above-described traveling speed change structure are generally used for traveling on soft ground having a large traveling resistance or for towing a truck carrying a load. If the gear shift clutch is operated to the transmission disengagement side during traveling gear shifting as described above, the engine power is not transmitted to the lower traveling system at this point, and the traveling speed of the aircraft suddenly decreases due to the traveling load described above. There is.

As a result, if the speed change clutch is operated to the transmission side and the power of the engine is supplied to the running system in the state where the traveling speed of the machine body is greatly reduced at the end of the gear shift operation by the actuator, the machine body is lowered. There will be room for improvement in terms of ride comfort, as a shock will be generated due to sudden acceleration to the original running speed. SUMMARY OF THE INVENTION It is an object of the present invention to provide a traveling gear shift structure for a work vehicle configured to shift gears for traveling by means of an actuator and a shift clutch so that the gear shift operation can be performed with less shock.

[0005]

The feature of the present invention resides in that the traveling speed change structure for a work vehicle as described above is configured as follows. That is, [1] a gear shift device for traveling and a shift clutch for traveling gear shift are arranged in series on the lower side of the engine, and a shift operation is performed by sliding a shift gear of the gear transmission based on an operation command. The hydraulically operated friction clutch which is equipped with an actuator, takes out the power of the engine from the upper side of the gear transmission and the speed change clutch, and transmits this power to the lower side of the speed change gear and the speed change clutch, and can cut off the transmission. And operating pressure changing means for changing the operating pressure of the transmission clutch to change the power transmitted by the transmitting clutch to high or low, and load detecting means for detecting the load applied to the engine, and gear shifting operation by the actuator When the control is started, the first control means for operating the speed change clutch to the transmission disengagement side in conjunction with this and the speed change operation by the actuator are opened. Once started, the operating pressure change means is operated to change and adjust the operating pressure of the transmission clutch based on the load detected by the load detection means such that the larger the load, the greater the power transmitted by the transmission clutch. And second control means for operating the transmission clutch on the transmission side, and third control means for operating the transmission clutch on the transmission side and operating the transmission clutch on the transmission cutoff side in conjunction with the completion of the shift operation by the actuator. Is equipped with.

[2] In the configuration of the above item [1], when the shift operation by the actuator is started, the operating pressure changing means is based on the load detected by the load detecting means immediately before the transmission clutch is operated to the transmission side. The second control means is configured to change and adjust the operating pressure of the transmission clutch to operate the transmission clutch on the transmission side.

[3] In the configuration of [1] or [2] above, the gear shift clutch is operated to the power transmission side and then the power transmission clutch is operated to the power transmission disengagement side in conjunction with the completion of the gear shift operation by the actuator. , Third control means.

[0008]

[Action]

[I] When configured as in the above item [1], for example, as shown in FIG.
When the shift gear S1 of the gear transmission A starts to be slid by the gear shift operation, the shift clutch 19
Is operated to the transmission interruption side, and at the same time, the transmission clutch E is operated to the transmission side. When the speed change clutch 19 is operated to the transmission disengagement side in this way, if the speed change clutch 19 is on the lower side of the gear speed changer A, the gear speed changer A and the traveling system are disconnected, and the speed change clutch 19 is changed to the gear speed changer. When on the upper hand side of A, the gear transmission A and the engine 1 are disconnected.
Accordingly, the sliding operation of the shift gear S1 of the gear transmission A by the actuators T1 and T2 is smoothly performed, and the gear shifting operation is performed.

As described above, the shift clutch 19 shown in FIG.
Is operated to the transmission disengagement side, the power of the engine 1 does not flow from the shift clutch 19 to the traveling system on the lower side. However, at the same time, the transmission clutch E is operated to the transmission side, so that the gear transmission A and the gear shift device The power of the engine 1 extracted from the upper side of the clutch 19 is transmitted to the traveling system via the transmission clutch E. As a result, when the gear shift clutch 19 is operated to the transmission cutoff side during a gear shift operation by the actuators T1 and T2, even if the traveling speed of the aircraft is about to be reduced due to a traveling load or a traction load, the aircraft from the power transmission clutch E is used Drive without slowing down too much. Therefore, when the speed change clutch 19 is operated to the transmission side after the completion of the speed change operation by the actuators T1 and T2 (with this, the transmission clutch E is operated to the transmission cutoff side).
Since the speed change clutch 19 is operated to the transmission side while the traveling speed of the machine body is not significantly reduced, it is possible to operate the speed change clutch 19 to the transmission side and cause a shock after the traveling speed of the machine body is extremely reduced. The situation can be prevented.

In this case, the load applied to the engine 1 is detected, and the operating pressure of the transmission clutch E is changed and adjusted so that the larger the load is, the larger the power transmitted by the transmission clutch E becomes. By changing and adjusting the operating pressure of the transmission clutch E in this way, it is possible to stabilize the traveling speed of the airframe during the gear shifting operation, regardless of changes in traveling load, traction load, and the like. Further, since the operating pressure of the transmission clutch E is set based on the load applied to the engine 1, the operating pressure of the transmission clutch E can be set accurately and accurately.

[II] When configured as in the above item [2],
As in the case of the configuration of the above [1], the "action" described in the above [I] is provided, and in addition to this, the following "action" is provided. Since the load applied to the engine changes continuously depending on the condition of the work site, etc., when the load applied to the engine is detected immediately before the transmission clutch is operated to the transmission side as in the previous section [2], the time when this is detected It is possible to suppress the fluctuation between the load on the power transmission and the load when the transmission clutch is actually operated on the transmission side to be small. As a result, the operating pressure of the transmission clutch can be set accurately and further.

[III] The constitution as described in [3] above has the "action" described in [I] or [II] as in the case of [1] or [2]. In addition to this, it has the following “action”. With the configuration of the above [3], as shown in FIG. 1, for example, the transmission clutch E is operated to the transmission interruption side with a slight delay with respect to the operation of the transmission clutch 19 to the transmission side. This allows
When the transmission clutch E is operated to the transmission cutoff side, the power is transmitted without interruption by the speed change clutch 19, and the operation of the transmission clutch E to the transmission side and the operation of the transmission clutch E to the power cutoff side are performed. At the time of switching, power transmission is not interrupted for a moment, and the traveling speed of the airframe does not momentarily decrease due to traveling load or traction load.

[0013]

According to the first aspect of the present invention, when the gear shift clutch is operated to the transmission cutoff side during the gear shift operation of the gear transmission by the actuator, the traveling system is provided by another transmission system that bypasses the gear transmission and the transmission clutch. Since the power is transmitted to the vehicle to suppress the decrease in the traveling speed of the aircraft, the entire gear shifting operation can be performed smoothly with less shock, and the riding comfort of the work vehicle can be improved. Also, since the operating pressure of the transmission clutch is set accurately based on the magnitude of the load on the engine, the difference in the traveling speed of the airframe before and after operating the transmission clutch on the transmission side after the shift operation has been minimized. In this state, the shift clutch is operated to the transmission side to smoothly transmit the power. As a result, the shock when the shift clutch is operated to the transmission side after the shift operation is completed can be suppressed well regardless of the traveling load, the traction load, etc., and the riding comfort of the work vehicle can be further improved.

According to the second aspect, similar to the case of the first aspect, the above-mentioned "effect of the invention" is provided. Further, according to the second aspect of the present invention, the operating pressure of the transmission clutch is accurately set by the load applied to the engine immediately before, so that the running speed of the airframe before and after the transmission clutch is operated to the transmission side after the gear shifting operation is completed. The difference can be further reduced, and the riding comfort of the work vehicle can be further improved.

According to the third aspect, similar to the case of the first or second aspect, the "effect of the invention" of the first or second aspect is provided. Further, according to the third aspect of the present invention, the power transmission is not interrupted for a moment at the end of the gear shift operation, and the traveling speed of the aircraft does not momentarily decrease due to the traveling load or the towing load. The riding comfort of the car can be further improved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (1) 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.
From the P via the transmission shaft 2 and the clutch mechanism 3.
It is transmitted to the TO shaft 4. The power from the engine 1 is the forward clutch 5 or the reverse clutch 6, the cylindrical shaft 11, the main transmission A (corresponding to a gear transmission), the transmission clutch 19, the first auxiliary transmission B, the second auxiliary transmission C, and the rear wheels. It is transmitted to the rear wheel 7 via the differential device 7a. The power branched from immediately before the rear wheel differential device 7a is transmitted to the front wheels 10 via the transmission shaft 9, the hydraulic clutch type front wheel transmission device D, the front wheel transmission shaft 12, and the front wheel differential device 10a.

The forward clutch 5 and the reverse clutch 6 are multi-plate friction type hydraulically operated systems in which a friction plate (not shown) and a piston (not shown) are combined and are supplied to the transmission side by supplying hydraulic oil. Operated. 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 11 to move the vehicle body forward. Reverse clutch 6
Is operated to the transmission side, the power of the engine 1 is transmitted to the cylindrical shaft 11 in the reverse rotation state via the reverse clutch 6 and the transmission shaft 31, and the machine body moves backward.

The main transmission A is constructed as a synchromesh type in which two sets of shift gears S1 are slidably operated, and is capable of shifting in four stages, and the power from the cylindrical shaft 11 on the engine 1 side is transmitted to the transmission shaft 35. The power is transmitted from the power transmission shaft 35 to the cylindrical power transmission shaft 40, and the speed is changed in four steps to be transmitted to the speed change clutch 19. The first auxiliary transmission B is also of a synchromesh type for sliding the shift gear S2. It is provided with hydraulic cylinders T1 and T2 (corresponding to actuators) for slidingly operating both shift gears S1 of the main transmission A, and a hydraulic cylinder T3 for slidingly operating shift gear S2 of the first auxiliary transmission B. The second auxiliary transmission C is a manually operated type in which the shift gear is directly slid by a shift lever (not shown).

(2) As shown in FIG. 1, the hydraulic cylinder T
When the speed change clutch 19 is operated to the transmission disengagement side as described later during the speed change operation of the main speed change apparatus A by 1, T2, the transmission shaft 34 of the first auxiliary speed change apparatus B on the lower side of the speed change clutch 19; A transmission clutch E capable of connecting the forward and reverse clutches 5 and 6 of the main transmission A to the transmission shaft 35 is provided. The transmission clutch E is configured as a friction multi-plate type in which a spring (not shown) urges the transmission clutch E to the transmission cutoff side, and the transmission clutch E is operated to the transmission side by supplying hydraulic oil.

As a result, when the hydraulic oil is drained and the transmission clutch E is operated in the transmission cut-off state, the transmission shaft 35 on the main transmission A side and the transmission shaft 34 on the first auxiliary transmission B side shown in FIG. 1 are disconnected. This transmission interruption state is the normal traveling state of the aircraft. Conversely, when hydraulic oil is supplied to operate the transmission clutch E to the transmission state, the transmission shaft 35 on the main transmission A side and the transmission shaft 34 on the first auxiliary transmission B side are connected, and the engine 1 Power is transmitted to the front wheels 10 and the rear wheels 7 via the transmission shafts 35 and 34. This transmission state is changed by the hydraulic cylinders T1, T2, T3 to the main transmission A.
Also, the first auxiliary transmission B is in a state of performing a speed change operation.

(3) Next, the hydraulic cylinders T1, T2, T
3, the hydraulic control system of the speed change clutch 19 and the transmission clutch E will be described. As shown in FIG. 2, the hydraulic pump 13
Is supplied to the three sets of hydraulic cylinders T1, T2, T3 via the rotary valve 15 from the hydraulic cylinder T.
A pilot oil passage 16 is provided for supplying / discharging pilot hydraulic oil during the operation of 1, T2 and T3. The hydraulic oil from the hydraulic pump 13 is supplied to the rotary valve 15 via the oil passage 17, and the hydraulic oil is supplied to the forward and reverse clutches 5 and 6 via the oil passage 18 and the forward / reverse switching valve 27. .

Hydraulic oil is supplied from the oil passage 20 branched from the oil passage 18 to the speed change clutch 19 via the pilot operated switching valve 26, and the pilot oil passage 16 is connected to the switching valve 26. Control valves 21 and 22 for controlling the supply and discharge of pilot hydraulic oil in the pilot oil passage 16 are provided, and the pilot oil passages 23 and 24 from the hydraulic cylinders T1 and T2 for the main transmission device A, and the first sub gear shift. The pilot oil passage 25 from the hydraulic cylinder T3 for the device B is connected to the control valves 21 and 22 as shown in FIG.
The hydraulic oil in the oil passage 38 branched from the oil passage 18 is supplied to the transmission clutch E via a pressure control valve 39 (corresponding to operating pressure changing means) of an electromagnetic proportional type.

As shown in FIG. 2, the rotary valve 15 can be mechanically operated to the neutral position and the first to eighth speed positions, the position sensor 29 for detecting the operating position of the speed change lever 14, and the forward / reverse switching. Set the valve 27 to the forward position F and the neutral position N.
And a forward / reverse lever 33 that can be operated in three positions of the reverse position R
Is equipped with. As shown in FIG. 1, a rotation speed sensor 30 for detecting the rotation speed of the transmission shaft 40 is provided between the main transmission A and the speed change clutch 19. An accelerator pedal 32 for the engine 1 is provided, and an accelerator opening sensor 36 that detects the accelerator opening of the engine 1 based on the operation position of the accelerator pedal 32 is provided.

(4) Next, the operation of each part during a gear shift operation will be described. FIG. 2 shows a state in which the forward / reverse lever 33 is operated to the forward position F and the transmission lever 14 is operated to the first speed position. The hydraulic cylinder T1 of the main transmission A moves to the first speed position and the hydraulic cylinder T2. Is in the neutral position,
The hydraulic cylinder T3 of the first auxiliary transmission B is located on the low speed side. As a result, the control valve 21 is switched by the pilot hydraulic oil from the hydraulic cylinder T1, and the pilot hydraulic oil from the hydraulic cylinder T3 enters the pilot oil passage 16 via the pilot oil passage 25 and the control valves 22 and 21. After being supplied, the switching valve 26 is switched to the communication position shown in FIG.

Therefore, the hydraulic oil from the oil passage 18 is supplied to the forward clutch 5 via the forward / reverse switching valve 27 and is operated to the transmission side (the reverse clutch 6 is shut off by the forward / backward switching valve 27). Operate on the side). The hydraulic oil from the oil passage 20 is supplied to the shift clutch 19 via the switching valve 26 to operate the shift clutch 19 on the transmission side, and the pressure control valve 39 operates the transmission clutch E to the transmission cutoff side. , The aircraft is traveling in the first forward speed state.

(5) In the forward first speed state as shown in FIG. 2, it is assumed that the shift lever 14 is started to be operated from the first speed position to the second speed position. By this operation, the pressure control valve 39 is operated by the control device 37 based on the detection of the position sensor 29, the working oil is supplied from the oil passage 38 to the transmission clutch E, and the piston (not shown) of the transmission clutch E is rubbed. It is lightly pressed against a plate (not shown) (time point A1 in FIG. 3).

Next, as shown in FIG. 2, the hydraulic oil from the rotary valve 15 causes the hydraulic cylinder T1 to start moving from the 1st speed position to the 2nd speed position (time A2 in FIG. 3), and the pilot oil passage 23 The pilot pressure decreases, the control valve 21 is switched, and the pilot oil passage 16 is discharged. As a result, the switching valve 26 is switched and hydraulic oil is drained from the speed change clutch 19, and the speed change clutch 19 is operated to the transmission interruption side (time point A3 in FIG. 3) (the above corresponds to the first control means). At the same time, the oil passage 38 and the pressure control valve 39
Is supplied to the transmission clutch E, and the transmission clutch E is operated to the transmission side.

As described above, the operation of the pressure control valve 39 to the transmission side of the transmission clutch E based on the detection of the position sensor 29 is not delayed (time A1 in FIG. 3). On the other hand, the start of the operation of the hydraulic cylinder T1 may be slightly delayed due to the flow path resistance of each part (at time point A in FIG. 3).
2), the operation of the transmission clutch 19 to the transmission cutoff side is more delayed (time point A3 in FIG. 3). In this case, as described above, rather than operating the transmission clutch 19 to the transmission interruption side,
Since the transmission clutch E is operated to the transmission side a little ahead, when the transmission clutch 19 is operated to the transmission interruption side,
The power transmission is not interrupted by the transmission clutch E.
And transmitted to the rear wheel 7. As a result, when the operation of the speed change clutch 19 to the transmission cutoff side and the operation of the transmission clutch E to the transmission side are switched, the transmission of power is interrupted for a moment, and the traveling speed of the airframe due to traveling load or traction load. Does not drop momentarily.

Thus, the speed change clutch 19 shown in FIG.
Is operated to the transmission cutoff side, the first auxiliary transmission B and the second auxiliary transmission C on the lower side from the speed change clutch 19
The power of the engine 1 stops flowing. However, since the transmission clutch E is operated to the transmission side slightly before this, the power of the engine 1 is the forward clutch 5 (or the reverse clutch 6), the cylindrical shaft 11, the transmission shaft 35 of the main transmission A, the transmission clutch. It is transmitted from the first auxiliary transmission device B and the second auxiliary transmission device C to the front wheels 10 and the rear wheels 7 via E and the transmission shaft 34, and the vehicle body moves forward even if there is a traveling load or a traction load.

(6) During the shifting operation as described above,
The operating pressure of the transmission clutch E is controlled to be high or low. Next, the control of this operating pressure will be described. As shown in Figure 1,
The rotation speed sensor 30 detects the rotation speed of the transmission shaft 40 between the main transmission A and the speed change clutch 19. Accordingly, if the position sensor 29 of FIG. 2 detects the operation position of the shift lever 14 (shift position of the main transmission A), the rotation speed of the engine 1 can be detected by the detection value of the rotation speed sensor 30. .

When the main transmission A is operated to the 1st speed position when there is no load on the engine 1 and no load is applied, it corresponds to the accelerator opening of the engine 1 (detection value of the accelerator opening sensor 36). The detected value R1 of the rotation speed sensor 30 and the accelerator opening of the engine 1 (the detected value of the accelerator opening sensor 36 when the main transmission A is operated to the second speed position when there is no load on the engine 1 and no load is applied). ), The detection value R2 of the rotation speed sensor 30 is obtained in advance.

As a result, as shown in FIG. 3, when the shift lever 14 is operated from the first speed position to the second speed position in the forward first speed state, the time point A1 (at which the hydraulic oil is started to be supplied to the transmission clutch E). Or immediately before this), the detection value R1 at the time of no load at the first speed position and the current rotation speed sensor 3
The difference F from the detected value of 0 is obtained to estimate the current load applied to the engine 1 (corresponding to load detecting means). in this case,
It can be determined that the load applied to the engine 1 is larger as the difference F is larger, and the operating pressure P1 of the transmission clutch E is set to be larger in proportion to the load, corresponding to the obtained load.

Therefore, as shown in FIG.
When 9 is operated to the transmission cutoff side and the transmission clutch E is operated to the transmission side (time point A3 in FIG. 3), the transmission device E and the pressure control valve 39 maintain the transmission clutch E at the above-mentioned operating pressure P1 ( (See time point A3 to time point A6 in FIG. 3) (corresponding to the second control means). As a result, the detection value of the rotation speed sensor 30 is maintained between the detection value R1 with no load at the first speed position and the detection value R2 with no load at the second speed position.

As described above, while the transmission clutch E is operated to the transmission side and the power of the engine 1 is transmitted to the front wheels 10 and the rear wheels 7 to advance the vehicle body, the time point A shown in FIG.
The shift operation to the second speed position by the hydraulic cylinder T1 is performed from 2 to time A4. When the shift operation is completed, pilot hydraulic oil is supplied again from the hydraulic cylinder T1 to the pilot oil passage 23 as shown in FIG. 2, and the control valve 21 is switched to the position shown in FIG. Pilot oil is supplied again to the switching valve 2
6 is switched to the communication position shown in FIG. As a result, hydraulic oil is supplied to the speed change clutch 19 as shown from time A4 to time A5 in FIG. 3, and the speed change clutch 19 is operated toward the transmission side. After a little delay, the transmission clutch E is operated by the pressure control valve 39 to the transmission cutoff side (time point A in FIG. 3).
6) (The above corresponds to the third control means).

In this case, as described above, the speed change clutch 19
Since the transmission clutch E is operated to the transmission cut-off side a little later than the operation to the transmission side of the front wheel 10, when the transmission clutch E is operated to the transmission cut-off side, the power transmission is not interrupted by the speed change clutch 19 and the front wheel 10 And transmitted to the rear wheel 7. As a result, when the operation of the transmission clutch 19 to the transmission side and the operation of the transmission clutch E to the transmission interruption side are switched,
Power transmission will not be interrupted for a moment, and the traveling speed of the aircraft will not momentarily decrease due to traveling load or traction load.

The above states are between the forward first speed state and the forward second speed state, and between the forward fifth speed state and the forward sixth speed state, but between the forward third speed state and the forward fourth speed state. , Between the seventh forward speed state and the eighth forward speed state, the hydraulic cylinder T2 of FIG.
And the control valve 22 is switched to perform the automatic operation as described above, and the hydraulic cylinders T1, T2, T3 are operated between the fourth forward speed state and the fifth forward speed state. The automatic operation as described above is performed. Even in the reverse state in which the forward / reverse lever 33 is operated to the reverse position R and the hydraulic oil is supplied to the reverse clutch 6, the automatic operation as described above is performed between the reverse first speed state and the reverse speed eighth state. Done.

[Other Embodiment] In FIG. 1, the rotation speed sensor 30 is not provided between the main transmission A and the shift clutch 19, but the engine 1 and the forward and reverse clutches 5, 6 are used.
It may be provided between and. In this case, the rotation speed of the engine 1 can be directly detected regardless of the operation position of the transmission lever 14 (main transmission A) detected by the position sensor 29.

In the hydraulic control system shown in FIG. 2, the oil passage 20 is provided with a pressure control valve (not shown) of an electromagnetic proportional type, a variable reducing valve (not shown), etc., and the hydraulic oil to the speed change clutch 19 is supplied. The pressure may also be controlled. In this case, when the speed change clutch 19 is operated to the transmission side as shown from time A4 to time A5 in FIG. 3 after the completion of the speed change operation, the pressure increasing characteristic of the hydraulic oil pressure to the speed change clutch 19 is changed to The shift clutch 19 is smoothly operated to the transmission side according to the load applied to the engine 1 estimated based on F.

A pressure control valve 3 of the electromagnetic proportional type in FIG.
Instead of 9, a variable reducing valve (not shown) may be used as the operating pressure changing means. Further, in the configuration shown in FIG. 1, the transmission clutch 19 disposed between the main transmission A and the first auxiliary transmission B is a cylindrical shaft between the forward and reverse clutches 5 and 6 and the main transmission A. You may prepare for the 11th part.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a transmission system in a mission case.

FIG. 2 is a hydraulic circuit diagram of a hydraulic cylinder for speed change operation, a speed change clutch, a transmission clutch, forward and reverse clutches, etc.

FIG. 3 is a diagram showing states of a hydraulic cylinder, a speed change clutch, a transmission clutch, and a rotation speed sensor during a speed change operation from a first speed position to a second speed position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 19 speed change clutch 39 operating pressure changing means A gear speed changer S1 shift gears of gear speed changer T1, T2 actuator E transmission clutch

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Fukui 64 Ishizukita-machi, Sakai City, Osaka Prefecture Kubota Sakai Factory Co., Ltd. (72) Inventor Yoshifumi Horiuchi 64, Ishizukita-machi, Sakai City, Osaka Prefecture Kubota Sakai Manufacturing Co., Ltd. In-house

Claims (3)

[Claims] 1. A gear transmission (A) for traveling and a shift clutch (19) for traveling shifting are provided on the lower side of the engine (1).
Are arranged in series, and equipped with actuators (T1) and (T2) that perform a shift operation by sliding the shift gear (S1) of the gear transmission (A) based on an operation command. ) And the speed change clutch (19) from the upper side, and the power of the engine (1) is taken out, and this power is transferred to the gear transmission (A) and the speed change clutch (1).
9) Hydraulically operated frictional transmission clutch (E) capable of transmission and transmission interruption operation to the lower side, and power for transmitting the transmission clutch (E) by changing the operating pressure of the transmission clutch (E) Is provided with an operating pressure changing means (39) capable of changing the pressure to a high level and a load detecting means for detecting a load applied to the engine (1), and a shift operation by the actuators (T1) and (T2) is started. And the speed change clutch (1
When the gear shift operation by the first control means for operating 9) to the transmission interruption side and the actuators (T1), (T2) is started, this load is increased based on the load detected by the load detection means. The operating pressure of the transmitting clutch (E) is changed and adjusted by operating the operating pressure changing means (39) so that the power transmitted by the transmitting clutch (E) becomes larger. The second control means operated to the side, and the gear shift clutch (19) is operated to the power transmission side in conjunction with the completion of the gear shift operation by the actuators (T1) and (T2), and the power transmission clutch (E) is operated. A traveling speed change structure for a work vehicle, comprising: a third control means that is operated to a transmission cutoff side. 2. The actuators (T1), (T2)
When the gear shift operation by is started, the operating pressure changing means (39) is based on the load detected by the load detecting means immediately before the transmission clutch (E) is operated to the transmission side.
Adjusts the operating pressure of the transmission clutch (E) and operates the transmission clutch (E) to the transmission side.
The traveling speed change structure for a work vehicle according to claim 1, which constitutes a control means. 3. The actuators (T1), (T2)
The gear shift clutch (1
9) Operate to the transmission side, and then move the transmission clutch (E)
3. The traveling speed change structure for a work vehicle according to claim 1, wherein the third control means is configured so as to operate the transmission to the transmission cutoff side.