JP2000097323A - Working vehicle and method for controlling clutch of working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a working vehicle provided with a control device to effect control a clutch pressure during gear shifting of a working vehicle without recording a number of pressure characteristics and prevent the occurrence of a shock during gear shifting. SOLUTION: Feedback control of a hydraulic clutch is effected such that the measuring speed (a solid line) of a working vehicle is adjusted to a value approximately equal to a theoretical running speed (a dotted line). When a measurement speed is extended toward a direction in which the measurement speed is parted from the theoretical running speed, by keeping a jerk value being a differential value for a time of acceleration at a constant value, the measurement speed is pointed to the direction of the theoretical running speed. Further, by performing control to hold acceleration at a specified value, control is carried out until the measurement speed attains the theoretical running speed. When the measurement speed attains the theoretical running speed (a dotted line), the clutch is completely brought into a transmission state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work vehicle, in particular, an engine, a traveling device, a transmission provided between the engine and the traveling device, and a transmission device disposed between the engine and the traveling device. A state in which the transmission of the driving force from the engine to the traveling device is cut off, a half-clutch state, a clutch displaceable between the transmission state, an actuator that operates the clutch, and a speed sensor that measures the ground speed of the work vehicle. Work vehicle to be provided. Further, the present invention provides an engine and a traveling device, a transmission provided between the engine and the traveling device, and a transmission device disposed between the engine and the traveling device to transmit driving force from the engine to the traveling device. Cutting state,
The present invention relates to a clutch control method for a working vehicle including a half-clutch state, a clutch that can be displaced in a transmission state, and an actuator that controls the clutch.

[0002]

2. Description of the Related Art A conventional working vehicle is disclosed in Japanese Unexamined Patent Publication No.
In this conventional example, one of a plurality of preset pressure increasing curves is set based on factors such as the number of engine revolutions, a shift position, and the rolling state of wheels. Select, hydraulic clutch (switching clutch)
The control operation is set so as to increase the pressure of the hydraulic clutch according to the selected pressure increase curve during the on-coming operation.

[0003]

However, in the case where the pressure is increased according to the characteristic selected when the hydraulic clutch is turned on as in the conventional example, one of a plurality of predetermined types of boosting characteristics is selected. Therefore, in order to smoothly enter and operate the hydraulic clutch in accordance with various factors, it is necessary to set a large number of boosting characteristics, which is troublesome in terms of manufacturing and leaves room for improvement.

Further, controlling the pressure of the hydraulic clutch along the stored pressure increasing curve means that, for example, even when the working vehicle reaches a desired speed, the clutch pressure is gradually increased along the pressure increasing curve. It also happens.
When such a situation occurs, it takes more time than necessary until the clutch connection, that is, the clutch shift, is completed. That is, since the clutch pressure is controlled irrespective of the state of the work vehicle, there is still room for improvement in that the optimized control of the clutch pressure cannot be said to be performed.

[0005] Shock at the time of shifting is generated when the hydraulic clutch is engaged, and appropriate control is performed by a mechanical difference between the hydraulic clutch and a solenoid valve that controls the pressure of the hydraulic clutch. Even if it is performed, the pressure of the hydraulic clutch cannot be raised with the preset characteristics, and there is room for improvement in this point. The present invention has been made in view of the above problems.

[0006]

In the work vehicle according to the present invention, a measured acceleration is obtained from the speed of the work vehicle, and the actuator is feedback-controlled so that the measured acceleration matches a predetermined acceleration characteristic. It is characterized by doing. It is not necessary to store a large number of boost curves for controlling the hydraulic clutch, and the hydraulic clutch can be controlled based on the acceleration of the work vehicle. Further, by performing more optimized control of the hydraulic clutch based on the state of the acceleration of the work vehicle, it is possible to prevent occurrence of a shock or the like.

Further, in the embodiment of the present invention, it is preferable to control a jerk value, which is a value obtained by differentiating acceleration with respect to time, in order to efficiently control a shock during shifting. Further, in the embodiment of the present invention, by detecting the engine speed of the work vehicle and the target shift speed, a theoretical traveling speed which is a desired traveling speed when a shift operation is performed is calculated. Although the clutch should be controlled so that the measurement speed becomes faster, it is desirable to perform this control based on the jerk value.

For example, the gear is shifted to a speed increasing position,
When the theoretical traveling speed is higher than the measured speed and the deceleration starts due to the weight of the work vehicle when the clutch is disengaged as the first stage of the shift operation, the speed of the work vehicle changes from deceleration to acceleration. (Direction of the theoretical running speed, which is the desired speed)
It is necessary to control to change to. For this reason, by controlling the jerk value to be positive, it is possible to shift from deceleration to acceleration.

Conversely, if the speed of the work vehicle is increased when the speed is shifted to the deceleration side and the theoretical traveling speed is lower than the measured speed, the jerk value is controlled to be negative, thereby increasing the speed. It is controlled to shift from speed to deceleration. In controlling the jerk value to be positive or negative in this manner, it is desirable to control the jerk value to be maintained at a constant positive or negative set value as necessary in terms of simplification of control.

In the embodiment of the present invention, it is desirable that the clutch be controlled so that the clutch is shifted from the half-clutch state to the complete transmission state as soon as the measured speed reaches the theoretical traveling speed. As a result, it is possible to prevent the time until the completion of the shifting operation from being prolonged more than necessary.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an agricultural tractor as an example of a work vehicle has an engine 1 disposed at a front position of a vehicle body having a drive-type front wheel FW and a drive-type rear wheel RW that are steered. Have been. A transmission system for transmitting the power from the engine 1 to the transmission case MC via the main clutch 2 provided in the main clutch housing is provided. Further, a steering handle SH and a driver seat DS are arranged at a center position of the vehicle body, and a pair of left and right lift arms LA which are operated by a lift cylinder LC serving as a drive elevating mechanism provided at a rear upper portion of the transmission case MC is provided. Tractor is constructed.

A rotary tilling device R is connected to the tractor via a three-point link mechanism including a top link TL and a pair of left and right lower links LL with respect to the rear end position of the vehicle body. By supporting the lower link LL and the left and right lift arms LA in a suspended state via a lift rod LR, the rotary tillage device R is configured to be able to move up and down by driving the lift arm LA.

A position lever (not shown) for setting the height of the rotary tilling device R with respect to the vehicle body and a gear-type transmission incorporated in the transmission case MC are provided at side positions of the driver seat DS. Main shifting lever 3 for shifting operation
3. Further, the forward / reverse lever 16 and the auxiliary speed change lever 43
Is arranged. Further, a brake pedal BP is disposed on the right side of the step portion, and a main clutch pedal CP is disposed on the left side. A brake switch 65 (FIG. 5) for detecting the displacement of the brake pedal BP is provided.

FIG. 2 shows a power transmission system of the agricultural tractor, in which the power from the engine 1 is supplied by a main clutch 2, a first main transmission A, a hydraulic clutch 3 for a multi-plate type traveling shift, and a first auxiliary transmission C. The power is transmitted to the rear wheels 4 via the second main transmission B, the second auxiliary transmission D, and the rear wheel differential mechanism 4a. Also,
The power branched immediately before the rear wheel differential mechanism 4a is transmitted to the transmission shaft 5
And transmitted to the front wheels 6 via the front wheel differential mechanism 6a. The power from the engine 1 is transmitted to the PT
It is transmitted to the O-shaft 8.

The first main transmission A is a synchromesh type gear shift type having two sets of shift members 9 and 10 and is configured to be able to shift to four speeds. Second main transmission B
This is also a synchromesh type gear shift type provided with one set of shift members 30, and is configured to be able to shift to two speeds. The first and second main transmissions A and B can be shifted to eight speeds. The shift members 9 and 10 of the first main transmission A are slid by the first and second hydraulic cylinders 11 and 12, and the shift member 30 of the second main transmission B is slid by the third hydraulic cylinder 13. You.

The second auxiliary transmission D has a set of shift members 31.
The shift member 31 is directly slid by the sub-shift lever 43. Therefore, the combination of the first and second main transmissions and the second auxiliary transmission D enables a maximum of 16 shift positions. As shown in FIG. 2, a switch 43 </ b> A functioning as a gear position sensor is provided at the base of the auxiliary speed change lever 43.
The third shift position can be detected. The output of the switch 43A functioning as a shift stage sensor is sent to a control device 42 (FIG. 4) as control means.

In FIG. 2, reference numeral 61 denotes a tachometer that measures the engine speed and functions as a speed sensor that communicates with the control device 42 (FIG. 4). Further, a speed sensor 63 for measuring the actual ground speed of the work vehicle is provided for the front wheels 6. As described above, the agricultural tractor according to the present embodiment can basically shift at 16 shift positions. However, when the load on the tractor changes, for example, when the state of the work site changes, the gear shifts to a shift position with a slightly different transmission ratio from the current gear position, and the load on the tractor returns to the original state There is a demand to return to the original shift position again. In order to respond to this demand, the tractor of the present embodiment is provided with a first auxiliary transmission C for realizing a transmission ratio slightly different from the current transmission position.

Next, the first auxiliary transmission C will be described. As shown in FIGS. 2 and 3, the first auxiliary transmission C is a synchromesh type forward / reverse switching unit C1 having a shift member 47 and a synchromesh type shift unit having a shift member 48, and can be shifted in two stages. And a transmission C2.

The forward / reverse switching unit C1 is configured such that a reverse gear 45 and a forward cylindrical shaft 46 are externally fitted to a transmission shaft 44 from the hydraulic clutch 3 so as to be relatively rotatable, and a shift provided on the transmission shaft 44 is provided. When the member 47 is slid rightward in FIG. 3 to engage the reverse gear 45, the power of the transmission shaft 44 is transmitted from the reverse gear 45 via the intermediate gear 55 to the transmission C2.
Transmission shaft 4 to the second main transmission B in a reverse state without passing through
9 is transmitted.

Conversely, when the shift member 47 is slid to the left in FIG.
The power of No. 4 is transmitted to the forward cylindrical shaft 46 in the forward rotation state, and the shift member 47 is directly slid by the forward / reverse lever 16. As shown in FIG. 2, the forward / reverse lever 16 is provided at its base with a switch 16A functioning as a gear position sensor. The output of the switch 16A is sent to the control device 42.

As shown in FIGS. 2 and 3, the transmission C2 is
A high-speed gear 50 is rotatably fitted on the advancing cylindrical shaft 46, and a low-speed gear 51 is rotatably fitted on the transmission shaft 44. When the shift member 48 provided on the forward cylindrical shaft 46 is slid to the right in FIG. 3 to engage with the high-speed gear 50, the power of the forward cylindrical shaft 46 is transmitted to the transmission shaft 49 in a normal high-speed state. You. Conversely, shift member 4
When the gear 8 is slid leftward in FIG. 3 to engage the low-speed gear 51, the power of the forward-moving cylindrical shaft 46 is transmitted to the transmission shaft 49 in the forward low-speed state.
The slide operation is performed by the hydraulic cylinder 14.

In this case, the high-speed gear 5 in the transmission portion C2
The transmission ratio difference between the low speed gear 51 and the low speed gear 51 is determined by the first
The transmission ratio is set to be smaller than the difference in the transmission ratio between the transmission positions of the second main transmissions A and B (transmission lever 33).

Next, the fourth hydraulic cylinder 14 of the transmission C2
Will be described. As shown in FIG. 4, an electromagnetically operated valve 22 for supplying and discharging hydraulic oil is provided in an oil chamber on the left side of the fourth hydraulic cylinder 14 in the drawing, and an oil chamber on the right side of the drawing of the fourth hydraulic cylinder 14 is described later. An oil passage 27 branched from the oil passage 17 is connected, and hydraulic oil is constantly supplied. The solenoid operated valve 22 is a three-port type having an input port for hydraulic oil, an output port for hydraulic oil, and a drain port for hydraulic oil, and is operated at two positions, a supply position for supplying hydraulic oil and a discharge position for discharging hydraulic oil. It is configured freely and is urged toward the supply position by a spring.

When the solenoid operated valve 22 is operated to the supply position by the above structure, the piston 14a moves rightward in the drawing as shown in FIG. 4 due to the difference in the pressure receiving area of the piston 14a. Shift member 4 of part C2
8 is a state in which the high-speed gear 50 is engaged. Next, when the solenoid operated valve 22 is operated to the oil discharge position, the piston 14a moves to the left in the drawing by the hydraulic oil supplied from the oil passage 27, and this state is when the shift member 48 of the transmission C2 is moved to the low speed gear. It is in a state of engaging with 51.

Next, the first and second hydraulic cylinders 11 and 12 of the first main transmission A will be described. As shown in FIG. 4, a large-diameter cylinder portion and a small-diameter cylinder portion are formed, and a large-diameter piston 23 and a small-diameter piston 24 are slidably housed therein. The first and second hydraulic cylinders 11 and 12 are configured to be slidably inserted.

An electromagnetically operated valve 25 for supplying and discharging hydraulic oil is provided on the right side of the drawing of the small diameter piston 24, and an electromagnetically operated valve 26 for supplying and discharging hydraulic oil is provided on the left side of the drawing of the large diameter piston 23. The solenoid operated valves 25 and 26 are of a three-port type having an input port for hydraulic oil, an output port for hydraulic oil, and a drain port for hydraulic oil.
It is configured to be operable at two positions, a supply position for supplying hydraulic oil to the hydraulic pump 12 and a discharge position for discharging hydraulic oil, and is urged toward the supply position by a spring.

With the above configuration, both solenoid operated valves 25,
When the valve 26 is operated to the supply position, as shown in the second hydraulic cylinder 12 in FIG. 4, the large-diameter piston 23 has a larger pressure-receiving area than the small-diameter piston 24 and has a larger diameter and a smaller diameter. The large-diameter and small-diameter pistons 23 and 24 try to move to the right in the drawing while the pistons 23 and 24 are pushing each other, and the large-diameter piston 23 hits the step of the large-diameter and small-diameter cylinders. Hold the large-diameter and small-diameter pistons 23 and 24. This state is the neutral stop position of the shift members 9 and 10 shown in FIG.

Next, when the solenoid operated valve 25 is operated to the oil discharge position while the solenoid operated valve 26 is left at the supply position, as shown in the first hydraulic cylinder 11 of FIG.
, The small-diameter piston 24 moves to the right in the drawing. This state is a state in which the shift members 9 and 10 shown in FIG. 2 are slid to the right in the drawing and are engaged with the transmission gear. Conversely, when the solenoid operated valve 26 is operated to the oil discharge position while the solenoid operated valve 25 is left at the supply position, the large-diameter and small-diameter pistons 23 and 24 move integrally to the left in the drawing. This state is a state in which the shift members 9 and 10 shown in FIG. 2 are slid to the left in the drawing and engaged with the transmission gear.

Next, the third hydraulic cylinder 13 of the second main transmission B will be described. As shown in FIG. 4, similarly to the fourth hydraulic cylinder 14, an electromagnetically operated valve 29 for supplying and discharging hydraulic oil is provided in an oil chamber on the right side of the drawing of the third hydraulic cylinder 13. An oil passage 28 branched from an oil passage 17 to be described later is connected to the left oil chamber, and hydraulic oil is always supplied. The solenoid operated valve 29 is a three-port type equipped with a hydraulic oil input port, a hydraulic oil output port, and a hydraulic oil drain port, and is operated at two positions, a supply position for supplying hydraulic oil and a discharge position for discharging hydraulic oil. It is configured freely and is urged toward the supply position by a spring.

When the solenoid operated valve 29 is operated to the supply position by the above structure, the piston 13a moves to the left in the drawing as shown in FIG. 4 due to the difference in the pressure receiving area of the piston 13a. The second main transmission B is in a low speed state. Next, when the solenoid operated valve 29 is operated to the oil discharging position, the hydraulic oil supplied from the oil passage 28 causes the piston 13 to be operated.
a moves to the right in the drawing, and this state is the high-speed state of the second main transmission B.

Next, the first, second, third and fourth hydraulic cylinders 1
Hydraulic circuits for the hydraulic clutches 1, 12, 13, 14 and the hydraulic clutch 3 will be described. As shown in FIG.
5, oil passages 17 and 18 are branched in parallel.
8, a pressure control valve 21 and an operation valve 35 of an electromagnetic proportional type are connected in series, and the hydraulic clutch 3 is connected to the lower side of the operation valve 35. That is, the pressure control valve 21 functions as an actuator that controls the hydraulic clutch 3 steplessly. With this actuator, the hydraulic clutch 3 is operated so as to be displaceable between a state in which the transmission of the driving force from the engine 1 to the traveling devices such as the front wheels 6 and the rear wheels 4 is cut off, a half clutch state, and a transmission state. is there.

The operating valve 35 is provided between a supply position 35a for supplying hydraulic oil to the hydraulic clutch 3 and transmitting the hydraulic oil, and an oil discharging position 35b for discharging hydraulic oil from the hydraulic clutch 3 and transmitting the hydraulic oil. It is a pilot-operable type that can be operated, and is urged toward the oil discharge position 35b by a spring.
The pilot oil passage 20 branches from the lower side of the throttle portion 19 in the oil passage 17, and the pilot oil passage 20 is
5 is connected.

The above-mentioned solenoid-operated valves 22, 25, 26, 29 are connected to the oil passage 17 on the upstream side from the throttle portion 19. On the lower side from the throttle portion 19 in the oil passage 17,
On-off valves 36, 37, 38, 39, 40 biased to the closing side
Is connected. First, second, third and fourth hydraulic cylinders 11
14 to 14, a recess is formed in the piston rod at a position corresponding to the shift position, and a neutral portion between the shift positions is formed in a convex shape. An interlocking mechanism 32 that opens and closes the on-off valves 36 to 39 between the shift positions is provided.

The shift shaft for sliding operation of the shift member 47 in the forward / reverse switching portion C1 of the first auxiliary transmission C is also provided on the shift shaft.
A concave portion and a convex neutral portion similar to those described above are formed, and a linkage mechanism 32 that opens and closes the on-off valve 40 between the forward side and the reverse side.
Is provided.

The gear is manually operated by the operator, and is provided with a shift lever 33 having operating positions of first to eighth speed positions, and functions as a shift stage sensor for detecting the operating position of the shift lever 33. The signal of the potentiometer 34 is input to the control device 42. The control device 42 operates the electromagnetic operation valves 25, 26, 29 based on the operation of the shift lever 33. A button-type operation switch 52 is provided on the grip portion of the shift lever 33, and the control device 42 operates the electromagnetic operation valve 22 based on the operation of the operation switch 52. The pilot oil passage 20 is located on the lower side of the throttle portion 19 in the oil passage 17.
A pressure sensor 41 for detecting the pilot pressure of the pressure sensor 41 is provided, and a signal from the pressure sensor 41 is input to the control device 42.

Next, the first and second shift levers 33 are used.
The shift operation of the main transmissions A and B will be described. The state shown in FIG. 4 is a state in which the shift lever 33 is operated to the first speed position, the first hydraulic cylinder 11 is in the first speed position of the first main transmission A, the second hydraulic cylinder 12 is in the neutral stop position, 3
The hydraulic cylinder 13 is in the low speed position of the second main transmission B, and is in the first forward speed state in which the forward / reverse lever 16 is located on the forward side.
As a result, the operation valve 35 is operated to the supply position 35a by the pilot pressure of the pilot oil passage 20, and the transmission operation of the hydraulic clutch 3 is performed.

In the first forward speed state, the shift lever 33
Is operated to the second speed position, for example, the first hydraulic cylinder 11
Is operated from the oil discharge position to the supply position,
The electromagnetic operation valve 26 of the first hydraulic cylinder 11 is operated from the supply position to the discharge position. As a result, the large-diameter and small-diameter pistons 23, 24 of the first hydraulic cylinder 11 start moving from the first speed position shown in FIG.
Starts to slide.

During the movement of the large-diameter and small-diameter pistons 23, 24 of the first hydraulic cylinder 11, the on-off valve 36 is opened by the linkage mechanism 32 (since the second hydraulic cylinder 12 is in the neutral stop position, The on-off valve 37 has already been opened.) As a result, the pilot pressure in the pilot oil passage 20 decreases, the operating valve 35 is operated from the supply position 35a to the oil discharge position 35b by the urging force of the spring, and the transmission of the hydraulic clutch 3 is operated.

Next, when the sliding operation of the shift member 9 by the first hydraulic cylinder 11 is completed and the first main transmission A is shifted to the second speed position, the on-off valve 36 is closed by the linkage mechanism 32. Then, the pilot pressure in the pilot oil passage 20 increases again, and the operation valve 35 is operated from the oil discharge position 35b to the supply position 35a. As described above, when the pressure sensor 41 detects that the pilot pressure has decreased and increased again in the pilot oil passage 20, the control device 4
2, the pressure control valve 21 is operated, and the hydraulic clutch 3
Is controlled by a control method described below.

In the same manner as the above shifting operation, the shifting lever 33
Is operated over the second speed position and the third speed position, the first main transmission A is shifted by the first and second hydraulic cylinders 11 and 12, and the shift lever 33 is shifted to the third speed position and the fourth speed position. By operating over this, the first hydraulic cylinder 12
The main transmission A is shifted.

When the shift lever 33 is operated between the fourth speed position and the fifth speed position, the first, second and third hydraulic cylinders 11 and 1 are operated.
When the first and second main transmissions A and B are shifted by the gears 2 and 13 and the shift lever 33 is operated between the fifth speed position and the sixth speed position, the first main transmission A is operated by the first hydraulic cylinder 11. Is operated, and if the shift lever 33 is operated between the sixth speed position and the seventh speed position, the first and second speeds are changed.
When the first main transmission A is shifted by the hydraulic cylinders 11 and 12, and the shift lever 33 is operated between the seventh speed position and the eighth speed position, the first main transmission A is shifted by the second hydraulic cylinder 12. Is done.

When the forward / reverse lever 16 is operated between the forward side and the reverse side, the on / off valve 40 is opened / closed by the linkage mechanism 32, and the hydraulic clutch 3 is operated by the operation valve 35 in the same manner as described above.
Are automatically turned off and further driven in the manner described below.

Next, the shift operation of the shift portion C2 of the first auxiliary transmission C by the operation switch 52 will be described. First
In a normal state in the transmission portion C2 of the subtransmission C, the solenoid operated valve 22 is operated to the supply position by the urging force of the spring, and the piston 14a of the fourth hydraulic cylinder 14 moves rightward in the drawing of FIG. And the shift member 48 of the transmission C2.
Are engaged with the high-speed gear 50.

In this state, when the operation switch 52 of the shift lever 33 shown in FIG. 4 is pressed once, the control device 42 operates the solenoid operated valve 22 from the supply position to the oil discharge position. Accordingly, the piston 14a of the fourth hydraulic cylinder 14 starts to move to the left in the drawing by the hydraulic oil supplied from the oil passage 27, and accordingly, the on-off valve 38 is opened by the linkage mechanism 32, and the operation valve 35 is opened. Drain position 35b
To operate the hydraulic clutch 3 for power transmission.

Next, when the shift member 48 is engaged with the low-speed gear 51 by the fourth hydraulic cylinder 14, the on-off valve 38 is closed by the linkage mechanism 32. Next, as described in detail below, the control device 42 operates the pressure control valve 21 to displace the hydraulic clutch 3 to the transmission state. At this time,
The display lamp 53 lights up.

In this case, the high-speed gear 5 in the transmission portion C2
0 and the low-speed gear 51 are different in the transmission ratio between the first and second gears.
The transmission ratio is set smaller than the difference in the transmission ratio between the main transmissions A and B (transmission lever 33) at each transmission position. Thus, for example, when the shift lever 33 is operated to the second speed position and the operation switch 52 is pressed as described above to engage the shift member 48 of the transmission C2 with the low speed gear 51, the second speed The transmission state is at an intermediate transmission ratio between the position and the first speed position.

Next, in the above-described state, the speed change lever 33
When the operation switch 52 is pressed again, the electromagnetic operation valve 22 is operated from the oil discharge position to the supply position by the control device 42, and the shift member 48 of the transmission C2 is moved to the low speed gear 5.
1 is engaged with the high-speed gear 50. At this time,
The hydraulic clutch 3 is automatically turned off by the on-off valve 38 and the operating valve 35, and the pressure control valve 21 is operated by the control device 42 to operate the hydraulic clutch 3 in the transmission state, as described in detail below.

Here, the shift operation by the shift lever 33 and the operation to the shift position having a transmission ratio slightly different from the current shift position by the operation switch 52 have been described. However, the operation of the transmission system by the operation of the auxiliary shift lever 42 is described. Is similar to this and will not be described here. With the structure of the above-described transmission, a shift is performed between different shift positions. When the shift position is changed, the hydraulic clutch 3 is automatically displaced to the transmission disengaged state as described above, but it is necessary to operate the hydraulic clutch 3 in the half-clutch state on the way to the transmission state. is there. By controlling the clutch pressure of the hydraulic clutch 3 in the half-clutch state, an optimized shift operation can be performed.

Hereinafter, how the control device 42 controls the pressure control valve 21 functioning as an actuator to control the clutch 3 will be described in detail. The control device 42 functioning as a control unit inputs output information from various sensors as shown in FIG. The potentiometer 34 functioning as a shift stage sensor for detecting the displacement position of the shift lever 33, the auxiliary shift lever 43, and the forward / reverse lever 16, the output from the switches 43A and 16A, the tachometer 61 functioning as an engine rotation sensor, and the speed sensor 63 The output of the brake switch 65 for detecting whether the brake pedal BP is operated and the output of the pressure sensor 41 for measuring the pilot pressure are input to the control device 42. The control device 42 operates the hydraulic clutch 3 via the pressure control valve 21 based on at least a part of the information.

Next, referring to FIG. 6 to FIG.
The second control algorithm will be described. In each of FIGS. 6 to 11, the vertical axis represents the speed of the work vehicle, and the horizontal axis represents time. Therefore, in this figure, the slope of the curve represents the acceleration a. In these drawings, the engine speed (rpm) which is the output of the engine speed sensor 61 is shown.
m) and the output from the gear position sensor 34, the theoretical traveling speed is calculated. This theoretical running speed is represented by a dotted line. The actual ground speed of the work vehicle based on the output of the speed sensor 63 is represented by a solid line.

The vertical axis in each of FIGS. 6 to 11 represents pressure, and the control oil pressure applied to the hydraulic clutch 3 is shown by a solid line. The horizontal axis represents time, and in each figure, the time axis in FIG. 7A corresponds to the time axis in FIG. 6 to 8 show that from t0 to t1,
In response to the control in which the work vehicle travels at a certain shift position and then shifts to a high-speed shift position, FIGS.
Corresponds to a case where a shift operation to a lower gear is performed at time t1 from the current shift position.

FIG. 6 shows a state in which the operator has operated the shift lever 33 to the high-speed shift position at t = t1. At this point, the hydraulic pressure to the hydraulic clutch 3 is automatically reduced to zero by the operation valve 35 as described above. In FIG. 6, when the clutch 3 is in the disengaged state, as shown by the solid line in FIG. 6A, the control in a state where the speed of the work vehicle is not increasing (the acceleration a is zero or negative) is shown. Have been. At this time, when the output value from the pressure sensor 41 of the control device 42 decreases, it is sensed that the clutch 3 has been disengaged, and nothing is performed during the set time from t1 to t2. At time t = t2, the displacement of each gear related to the shift is completed, and the operation valve 35 permits the transmission of the hydraulic pressure of the pressure control valve 21 to the clutch 3. At this time, the control device 42 controls the pressure control valve 21 so as to send the set hydraulic pressure P2 to the clutch 3 so as to bring the hydraulic clutch 3 into the half-clutch state only from t2 to t3.

At t = t3, the control device 42 calculates the acceleration of the work vehicle by continuously inputting the output from the speed sensor 63 and calculating the change in the measured speed per time unit. . Further, by calculating a temporal change of the acceleration, a value obtained by differentiating the acceleration generally referred to as a jerk value a 'with respect to time is obtained. Here, the apostrophe (') attached to a represents a differentiation with respect to time. The controller 42 determines that the jerk value a 'is equal to a constant first
Feedback control is performed on the hydraulic clutch 3 so as to compare with the set value β and make them equal. Thus, feedback control for obtaining an acceleration characteristic with a constant jerk value is referred to as a first control mode.

Since β is a positive value, when such control is performed, the measured acceleration a of the work vehicle drawn by the solid line shifts from negative to positive. That is, when the theoretical traveling speed is higher than the measurement speed, the measurement speed decreases,
When the measured speed is changed in the opposite direction to the theoretical traveling speed, the jerk value is controlled to be positive in order to shift the measured speed in the direction of the theoretical traveling speed. When the measured acceleration reaches α which is the second set value, at this time (t = t
In 4), the feedback control is performed on the hydraulic clutch 3 so that the measured acceleration becomes the second set value α. The feedback control for obtaining the acceleration characteristic that makes the acceleration constant as described above is referred to as a second control mode.

This control is continued at t = t5 until the measured speed matches the theoretical running speed. The time during which the jerk value is controlled to be the first set value β (from t3 to t4) is called the first time region, and the time during which the measured acceleration a ′ is controlled to be the second set value α. (T4 to t5) is called a second time domain.

As soon as the measured speed coincides with the theoretical running speed, the control device 42 increases the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1 for bringing the hydraulic clutch 3 into a completely transmitting state. FIG. 7 shows a state in which, during shifting, after the clutch 3 is operated to be in the disengaged state, when the half-clutch state is controlled at t3, the acceleration a is positive and the measured speed is already higher than the theoretical traveling speed. Is shown. When the measurement speed is rapidly increasing in this way, the control by the control device 42 from t = t3 indicates that the jerk value a 'is -β (β> 0) which is the first set value in this state. Control (first control mode). That is, when the theoretical traveling speed is lower than the measured speed, and the measured speed increases and changes in the direction opposite to the theoretical traveling speed, the jerk value is changed to shift the measured speed in the direction of the theoretical traveling speed. It is controlled to be negative. In this case, since the actual speed of the work vehicle is higher than the theoretical running speed based on the combination of the engine rotation and the target clutch, when the clutch pressure of the hydraulic clutch 3 increases, the engine brake is applied, so that the work vehicle is decelerated. It can be done.

As a result, the speed curve of the work vehicle having overshot the desired theoretical traveling speed is controlled so as to decrease in the direction of the theoretical traveling speed. Moreover, it is possible to avoid a shock that occurs when the clutch pressure is increased to P1 at a stroke. Further, at t = t4, when the measured acceleration a becomes equal to the second set value -α, the control is started so that the measured acceleration becomes -α (second control mode).

At t = t5, when the measured speed becomes equal to the theoretical running speed, the control device 42 immediately changes the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1 for bringing the hydraulic clutch 3 into a completely transmitting state. Raise to In FIG. 8, after the gearshift operation is performed and the hydraulic clutch 3 is automatically disengaged, when the half-clutch state is controlled at t3, the measured speed is in an accelerating state, and the measured speed is reduced to the theoretical speed. The control when not exceeded is shown.

The control oil pressure to the hydraulic clutch 3 is substantially P
By setting the hydraulic clutch 3 to a light half-clutch state substantially at a set value P3 lower than 2, it is possible to allow the speed of the work vehicle to naturally reach the theoretical traveling speed at t = t5. As soon as the measured speed matches the theoretical running speed,
The control device 42 increases the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1.

In this case, if the acceleration of the work vehicle is small and the measured speed does not reach the theoretical speed within the set time,
The control device 42 increases the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1. In addition, when the measured speed does not reach the theoretical traveling speed within the set time, the acceleration a may be controlled to become the set acceleration α.

FIG. 9 shows changes in different parameters in a state in which the shift operation to the lower gear is performed at time t1 and the work vehicle is not decelerating (acceleration is zero or positive) at time t3. ing. When the half clutch state of the hydraulic clutch 3 is started at t = t3, the hydraulic clutch 3 is feedback-controlled so that the jerk value a 'becomes -β which is the first set value (first control mode). Then, when the acceleration a becomes −α at t4 (t
In 4), the actual acceleration of the work vehicle is set to the second set value -α
A second control mode is started. This second control mode is continued until the measured speed matches the theoretical running speed at t5. As soon as the measured speed matches the theoretical running speed, the control device 42 increases the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1.

In FIG. 10, after the gear shifting operation is performed, t =
Control at the time t3 when the acceleration is negative and the measured speed is already lower than the theoretical running speed is shown. In such a case, the controller 42 from t = t3
Controls that the jerk value a ′ is the first in this state.
Control is performed so as to be the set value β (first control mode). As a result, control is performed so that the speed curve of the work vehicle that has overshot the desired theoretical traveling speed is increased in the direction of the theoretical traveling speed. Moreover, it is possible to avoid a shock that occurs when the clutch pressure is increased to P1 at a stroke. Further, at t = t4, when the measured acceleration a becomes equal to the second set value α, the measured acceleration a
Is started so that the value becomes α (second control mode).

At t = t5, when the measured speed becomes equal to the theoretical running speed, the control device 42 immediately increases the control oil pressure to the hydraulic clutch 3 to the set oil pressure P1. FIG. 11 shows a control method in a case where the measured speed is in a decelerating state and is not lower than the theoretical traveling speed when the hydraulic clutch 3 is brought into a half-clutch state at t3 due to a shift operation. In this case, the control oil pressure to the hydraulic clutch 3 is set to P3, which is a set value lower than P2, and the hydraulic clutch 3 is substantially kept in a light half-clutch state. Allow to reach speed. As soon as the measured speed matches the theoretical running speed, the control device 42 sets the control oil pressure to the hydraulic clutch 3 to
The control oil pressure to the hydraulic clutch 3 is increased to the set oil pressure P1.

In this case, if the speed of the working vehicle does not naturally reach the theoretical traveling speed within the set time, the hydraulic clutch 3
By increasing the control hydraulic pressure to the set hydraulic pressure P1, it is possible to avoid extending the gear change time. In addition, when the measured speed does not reach the theoretical traveling speed within the set time, the acceleration a may be controlled to become the set acceleration α.

In the above description, for example, when the feedback control is performed so that the acceleration a calculated based on the measured speed becomes equal to the set value α, the control is performed so that the acceleration a and the target value α are completely equal. However, it is preferable to provide a dead zone having a width of δ at the target value α, and to perform control such that the acceleration a exists between α ± δ.

The control operation of the control device 42 is set so that, when the operator intentionally performs a deceleration operation by depressing the brake pedal BP, a process of automatically decelerating the transmission system relative to the traveling system is performed. Have been. That is, FIG.
As shown in the flowchart of FIG.
When it is determined that the brake operation has been performed based on the signal from the control unit 5, the rotational speed sensor 61, the shift speed sensor 34, the rotational speed of the engine 1, the shift speed of the transmission, and the measured speed of the work vehicle are used. The actual speed is reduced by a set value or more by comparing the theoretical speed obtained from each of the speed sensors 63 based on the rotational speed of the engine 1 and the gear position of the transmission with the actual speed. If it is determined that the gear is present, the speed change motor (not shown) is controlled to perform the speed reduction operation of the gear (steps # 1 to # 5).

Since the transmission system is formed as described above, when shifting the traveling speed, the shift lever 33 is operated only to a desired shift speed, and automatic operation is performed without depressing the clutch pedal 17. The gear can be changed. At the time of the on-coming operation of the hydraulic clutch 3, the on-coming operation of the hydraulic clutch 3 is performed with the optimal boosting characteristic based on the theoretical traveling speed and the actual speed, so that the occurrence of a shock is suppressed and a smooth shift is enabled. I have. In particular, even if the acceleration acting on the vehicle body during this shift is large, this acceleration is corrected with a constant jerk value a ', so that a shift to a desired shift speed can be made without causing a shock. It becomes possible.

[Another Embodiment] In the above embodiment, the control device 42 senses that a shift operation has been performed due to a decrease in the output of the hydraulic pressure sensor 41 for measuring the pilot pressure. The control device 42 instead of the shift lever 33
By the operation described above, it may be determined that the speed change operation has been performed. Further, in the above embodiment, the hydraulic clutch 3
When the shift operation is performed by the operation valve 35 or the like, the clutch is automatically displaced to the clutch disengaged state. Instead of this, the control device 42 may be configured to perform the clutch disengagement state when the shift operation is performed.

Instead of using the pressure control valve 21 of the electromagnetic proportional type, a type in which an electromagnetic solenoid is provided and PWM control is performed may be used. Further, in the above embodiment, as shown in FIG. 7, for example, when the measured speed of the work vehicle exceeds the theoretical running speed at time t3, the jerk value a ′ is controlled to be −β. However, instead of this, even if the measured speed does not exceed the theoretical traveling speed at time t3, the acceleration a exceeds the third set value γ, which is a value larger than the second set value α.
Even if the measured speed reaches the theoretical running speed, the hydraulic clutch 3
Without increasing the control oil pressure to P1, the control speed is allowed to exceed the theoretical traveling speed, and then the control is performed in the first control mode in which the jerk value a ′ is controlled to −β. Is also good. Thereafter, the second control mode is performed until the measured speed becomes the theoretical running speed. In this case, when the acceleration a of the work vehicle is equal to or smaller than the third set value γ, the control described with reference to FIG. 8 is performed.

It will be obvious to those skilled in the art that similar control can be applied to the control described with reference to FIGS. The control pressure of the hydraulic clutch 3 according to the present invention described in the above embodiment is controlled by the speed sensor 34, the engine speed sensor 61, and the speed sensor 63.
It is a function that uses the output of the input as the input value. As in the above embodiment, feedback control based on acceleration and jerk value may be performed, but feedback control based on the difference between the theoretical traveling speed and the measured speed may be performed. For example, the following control may be performed. If the shift operation is a shift to a high-speed shift position,
The greater the speed difference, the more quickly the hydraulic pressure to the hydraulic clutch 3 is increased. When the shift operation is a shift to a lower shift position, the control oil pressure to the hydraulic clutch is gradually increased as the shift difference is larger.

The present invention relates to the shifting operation of the work vehicle, particularly to the characteristics of the control hydraulic pressure applied to the hydraulic clutch 3, and is not limited to the transmission system of the work vehicle disclosed in the above embodiment and another embodiment. Absent. In particular, it is within the scope of the present invention to apply the present invention to a work vehicle that does not have the first sub-transmission C and the second sub-transmission D.

[Brief description of the drawings]

FIG. 1 is a side view of a working vehicle according to the present invention.

FIG. 2 is an explanatory diagram illustrating a path in which driving force is transmitted from an engine of the work vehicle of FIG. 1 to a front wheel and a rear wheel.

FIG. 3 is a sectional view of an auxiliary transmission.

FIG. 4 is an explanatory diagram relating to a hydraulic system of the work vehicle in FIG. 1;

FIG. 5 is an explanatory diagram showing different sensors for inputting signals to the control device and outputs from the control device.

FIG. 6 is a diagram showing control relating to feedback control of the hydraulic clutch when shifting to a higher speed side when the work vehicle is in a decelerating state.

FIG. 7 is a diagram showing control relating to feedback control of the hydraulic clutch when shifting to a higher speed side when the work vehicle is in a state of rapid acceleration.

FIG. 8 is a diagram showing control relating to feedback control of a hydraulic clutch when shifting to a higher speed side when the work vehicle is in a state of non-rapid acceleration.

FIG. 9 is a diagram showing control relating to feedback control of the hydraulic clutch when shifting to a lower speed side when the work vehicle is in a speed increasing state.

FIG. 10 is a diagram showing control relating to feedback control of the hydraulic clutch when shifting to a lower speed side when the work vehicle is in a state of rapid deceleration.

FIG. 11 shows a state in which the working vehicle is in a state of non-rapid deceleration.
The figure which shows the control regarding the feedback control of the hydraulic clutch at the time of shifting to a low speed side

FIG. 12 is a flowchart showing a control routine for automatically shifting down the shift speed when a braking operation is intentionally performed.

[Explanation of symbols]

 A first main transmission B second main transmission C first sub transmission D second sub transmission 1 engine 3 hydraulic clutch 16 forward / reverse lever 21 pressure control valve 33 main transmission lever 34 potentiometer 35 operating valve 41 pressure sensor 42 Control device 43 Sub transmission lever 63 Speed sensor

Claims (17)

[Claims] 1. An engine, a traveling device, a transmission provided between the engine and the traveling device, and a transmission of driving force from the engine to the traveling device disposed between the engine and the traveling device. Disengaged state, half-clutch state, and a clutch displaceable between a transmission state, an actuator for operating the clutch, and a work vehicle including a speed sensor for obtaining a measured speed of the work vehicle; A work vehicle, comprising: control means for obtaining a measured acceleration based on an output, and performing feedback control of the actuator so that the measured acceleration matches a preset acceleration characteristic. 2. The work vehicle according to claim 1, wherein the control unit further performs feedback control on the actuator so that a jerk value, which is a derivative of the measured acceleration with respect to time, matches the set acceleration characteristic. 3. The work vehicle further includes a rotation speed sensor for measuring a rotation speed of an engine of the work vehicle, and a shift speed sensor for measuring a target shift speed. The control unit includes the rotation speed sensor and the speed sensor. Based on the output from the gear position sensor, a theoretical traveling speed that is a desired traveling speed is calculated, and the set acceleration characteristic is such that the theoretical traveling speed is greater than the measured speed, and the measured speed decreases. Has a time region in which the jerk value is positive, the theoretical traveling speed is smaller than the measured speed, and when the measured speed is increasing, the jerk value is negative. The work vehicle according to claim 2, wherein the work vehicle has a time domain. 4. The acceleration characteristic includes a first time region that is a first set value at which the jerk value is constant.
Or the working vehicle according to 3. 5. The work vehicle according to claim 4, wherein the acceleration characteristic includes a second time region in which the acceleration is a constant second set value. 6. The work vehicle according to claim 5, wherein the second time domain follows the first time domain. 7. The work vehicle according to claim 6, wherein the first time domain ends and the second time domain starts when the measured acceleration becomes equal to the second set value. 8. The control device according to claim 1, wherein, when the measured speed reaches the theoretical running speed in the second time domain, the actuator performs control to immediately shift the clutch from the half-clutch state to the transmission state. Item 8. The work vehicle according to any one of Items 5 to 7. 9. The work vehicle according to claim 1, wherein the clutch is a hydraulic clutch, and the actuator controls a hydraulic pressure supplied to the hydraulic clutch. 10. An engine and a traveling device, a transmission provided between the engine and the traveling device, and a transmission disposed between the engine and the traveling device to cut off transmission of driving force from the engine to the traveling device. State, half-clutch state,
A clutch capable of being displaced in a transmission state, and a clutch control method for a working vehicle having an actuator that controls the clutch, a process of obtaining a measured speed of the working vehicle, a process of obtaining a measured acceleration based on the measured speed, An operation of comparing the measured acceleration with a preset acceleration characteristic, and a step of performing feedback control of the actuator based on the comparison to match the measured acceleration with the acceleration characteristic. Car clutch control method. 11. The method further comprises calculating a jerk value that is a derivative of the measured acceleration over time;
The clutch control method for a work vehicle according to claim 10, further comprising a step of performing feedback control of the actuator so that the jerk value matches the set acceleration characteristic. 12. The method according to claim 1, further comprising the steps of: measuring a rotational speed of the engine of the work vehicle; measuring a target shift speed; and the control unit determines a desired speed based on the rotational speed and the target shift speed. A step of calculating a theoretical traveling speed that is a traveling speed, wherein the set acceleration characteristic is such that the theoretical traveling speed is greater than the measured speed and the measured speed is decreasing. A time region in which the jerk value is positive, the theoretical traveling speed is smaller than the measured speed, and the time region in which the jerk value is negative when the measured speed is increasing. Claim 11 or 1 having
2. The working vehicle according to 2. 13. The acceleration characteristic includes a first time region in which the jerk value is a constant first set value.
Or a clutch control method for a working vehicle according to item 12. 14. The work vehicle clutch control method according to claim 10, wherein the acceleration characteristic includes a second time region in which the acceleration is a constant second set value. 15. The work vehicle clutch control method according to claim 14, wherein the second time domain of the acceleration characteristic follows the first time domain. 16. When the measured acceleration becomes equal to the second set value, the first time domain ends, and the second time domain ends.
The method according to claim 15, wherein the time domain is started. 17. The method according to claim 12, further comprising the step of: when the measured speed reaches the theoretical traveling speed, causing the actuator to immediately shift the clutch from a half-clutch state to a transmission state. A method for controlling a clutch of a working vehicle according to any one of the above.