JP2010234864A - Transmission gear of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability by reducing a wear and tear degree of a clutch, while making the most use of a merit of operability and an advantage to reduce an uncultivated part, such as to automatically perform engagement-disengagement having a half-clutch of a PTO clutch, in operation of a braking operation tool. <P>SOLUTION: The PTO clutch is operated for disengagement after starting braking operation by the braking operation tool 41 in operation to the travel stopping side of the braking operation tool 41. The operation timing is set so as to start engaging operation of the PTO clutch 24 before the braking operation is released by the braking operation tool 41 in operation to the travel stopping releasing side of the braking operation tool 41. A control means 32 is provided for making control so that a change in clutch pressure of the PTO clutch 24 to an operation quantity of the braking operation tool 41 becomes gentler on the clutch engaging side than the clutch disengaging side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes a traveling drive system transmission device that transmits engine power to a traveling device, and a work device drive system transmission device that transmits engine power to an external power take-out shaft, and for stopping the traveling of the airframe. The present invention relates to a transmission device for a work vehicle provided with a braking operation tool.

As a transmission device for this type of work vehicle, one having the following structure is conventionally known.
[1] Depressing a brake pedal, which is a braking operation tool, puts the traveling transmission into a stopped state, and operates the PTO clutch of the work device drive system to the disengagement side to stop driving the PTO shaft. I have to. Then, when starting the tilling work again, the PTO clutch is automatically engaged and the rotary tiller starts to rotate slowly if the brake pedal is slightly returned while the brake is applied and the running is stopped. When the rotary rotary tiller is lowered to enter the field and lowered to the desired tilling depth, the brake pedal is further returned to completely release the braking, and the vehicle proceeds to forward travel in the desired tilling state. What you can do. (For example, refer to Patent Document 1).

JP 2008-137436 A (paragraph numbers 0028, 0029, 0035, 0037, FIGS. 3 and 4)

In the conventional structure shown in [1] above, for example, in a plowing operation in which a rotary plowing device is connected to the rear portion of the tractor main unit and driven by a PTO shaft, when stopping traveling during the plowing operation, the brake pedal is depressed. Since the PTO clutch is automatically disengaged by operating and stopping, it is useful in that it is possible to avoid an increase in the stopping distance due to the rotary cultivator being driven by the rotary tractor unit. Is.
And when resuming work, the PTO clutch is automatically engaged while maintaining the state where the travel is stopped by slightly returning the brake pedal. Therefore, when starting work from the end of the field, there is no need for a separate shifting operation, and only the brake pedal is operated. Tillage work can be done, and there is also the convenience that can reduce the remaining plowing part.

With the structure in which the operation of the PTO clutch is linked to the operation of the brake pedal operated at the start and stop of the airframe as in the conventional structure described above, in order to avoid a sudden increase in load at the start of driving of the rotary tiller Then, the brake pedal in the depressed state is slightly returned and the PTO clutch is engaged after passing through the half clutch state of the PTO clutch, and then the vehicle starts to travel.
As described above, the PTO clutch linked to the operation of the brake pedal is disengaged after passing the half-clutch state even when the airframe is stopped. That is, since the half-clutch state appears not only when the aircraft starts but also when it stops, there is a possibility that the degree of wear of the PTO clutch increases, which may be disadvantageous in terms of durability.
Moreover, the aircraft continues to run in the half-clutch state until the aircraft completely stops, so compared to the case where the aircraft is stopped even in the same half-clutch state and the rotary tiller is driven gradually at the same position. Because of the difference in speed generated between the traveling speed of the machine and the driving speed of the rotary tiller, the PTO clutch clutch plate may be slidably rotated even in a relatively strong pressure contact state. There is a possibility that the clutch may be worn and there is room for improvement.

  The object of the present invention is that the operation of the brake operating tool for stopping the aircraft is automatically turned on and off with the half clutch of the PTO clutch, and the advantage that the operability and the remaining tillage portion can be reduced. It is to reduce the degree of clutch wear while making the most of it, and to obtain a highly durable work vehicle transmission.

[Solution 1]
The technical means of the present invention devised to solve the above-described problems includes a travel drive system that transmits engine power to a travel device, and a work device drive system that transmits engine power to an external power take-out shaft. In a work vehicle transmission device provided with a braking operation tool for applying a braking action to traveling,
A hydraulically operated PTO clutch for intermittently transmitting power to an external power take-off shaft in the work device drive system;
The PTO clutch and the braking operation tool are configured to change the clutch pressure of the PTO clutch to a clutch disengaged state with an increase in the operation amount to the travel stop side by the brake operation tool, and the operation amount to the travel stop side. The clutch operating force and the PTO clutch are linked so that the clutch pressure is changed with the decrease in the clutch operation state, and the braking operation tool and the PTO clutch are connected to the braking operation tool when operated to the travel stop side. After the braking operation is started, the PTO clutch is disengaged. In the operation of the braking operation tool toward the travel stop release side, the PTO clutch engagement operation is started before the braking operation by the braking operation tool is released. The operation timing is set so that
Further, the present invention is characterized by further comprising control means for controlling the change in the clutch pressure of the PTO clutch with respect to the operation amount of the braking operation tool so that the change is more gentle on the clutch engagement side than on the clutch disengagement side.

[Action and effect]
As described above, in the work vehicle transmission device according to the present invention according to Solution 1, the PTO clutch can be automatically turned on and off by merely operating the braking operation tool by linking the PTO clutch and the braking operation tool. In addition, the operation timing is set so that the PTO clutch is disengaged after the aircraft is stopped and the PTO clutch is engaged before the stop operation is released by the brake operation tool. Since it is set, it is possible to perform tillage work with good operability and few remaining plowing parts.
And in the case of pursuing good operability and reduction of the remaining tillage portion in this way, there is a possibility of causing a new problem that the degree of wear of the PTO clutch that is started and stopped through the half-clutch state is increased. However, in the present invention, the change degree of the clutch pressure of the PTO clutch that is turned on and off by the change of the clutch pressure is solved by making it different in association with the operation direction of the brake operating tool.
That is, the change in the clutch pressure of the PTO clutch with respect to the amount of operation of the brake operating tool operates the brake operating tool to the stop release side more than the change when the brake operating tool is operated to the travel stop side to disengage the PTO clutch. Thus, the PTO clutch is controlled so that the change when the PTO clutch is engaged is moderated, so that the PTO clutch is quickly disengaged when the travel is stopped, and the PTO clutch is slowly engaged after the half-clutch state when the stop is released. I have to.

  Therefore, just by operating the brake operation tool, the PTO clutch can be automatically turned on and off and the travel stop can be released after the clutch is engaged, thereby improving operability and reducing residual tillage. In addition, there is an advantage that durability of the PTO clutch can be improved by reducing wear of the clutch plate due to half-clutch operation when the vehicle is stopped.

[Solution 2]
According to a second means for solving the problem in the transmission device for a work vehicle of the present invention, as described in claim 2, the PTO clutch engagement operation end position associated with the operation of the braking operation tool toward the travel stop release side is the braking operation. It is characterized in that it is set closer to the start side of the travel stop release operation than the end position of the travel stop release operation of the braking operation tool during the operation stroke of the tool.

[Action and effect]
As described above, in the work vehicle transmission of the present invention according to the solving means 2, the position where the PTO clutch engagement operation ends when the brake operating tool is operated toward the travel stop canceling side is the travel stop canceling operation of the brake operating tool. Since it is set closer to the start side of the travel stop release operation than the end position of the brake, the brake is applied during the operation stroke of the brake operating tool between the end position of the PTO clutch engagement operation and the end position of the travel stop release operation. Even if the operating tool is slightly operated toward the travel stop side, there is a region where the clutch pressure of the PTO clutch does not change.
Therefore, for example, in the middle of the travel stop release operation of the brake operation tool, before the travel stop release operation has been completed, the operator used the brake operation tool with the foot placed lightly instead of the footrest. However, since the region where the clutch pressure does not change is present, it is possible to avoid a half-clutch state inadvertently. As described above, the operation of the PTO clutch in the half-clutch state without the operator's intention can be avoided by providing an area in which the PTO clutch is not operated during the operation stroke of the brake operation tool. As a result, it is easy to avoid occurrence of a situation in which the PTO clutch remains operated for a long time in a half-clutch state without being noticed, and burn-in occurs.

[Solution 3]
According to a third means for solving the problem in the transmission device for a work vehicle of the present invention, the PTO clutch disengagement operation start position associated with the operation of the braking operation tool toward the traveling stop side is the braking operation tool. It is characterized in that it is set closer to the travel stop operation end side of the braking operation tool than the PTO clutch engagement operation start position associated with the operation of the brake operation tool toward the travel stop release side during the operation stroke.

[Action and effect]
As described above, in the work vehicle transmission device of the present invention according to the solving means 3, the PTO clutch disengagement operation start position associated with the operation of the braking operation tool toward the travel stop side is set to the braking during the operation stroke of the braking operation tool. It is set closer to the travel stop operation end side of the braking operation tool than the PTO clutch engagement operation start position accompanying the operation of the operation tool toward the travel stop release side, and the start point of the PTO clutch disengagement operation is determined by the brake operation tool. The time is approaching when the travel stop operation ends.
As a result, when the brake operating tool is operated to the travel stop side, the PTO clutch can be operated in a short time without performing an operation that causes the PTO clutch to rub in a half-clutch state for a long time, and the wear of the clutch plate is reduced. There are advantages that can be reduced.

[Solution 4]
According to a fourth means for solving the problem of the invention, the display means for displaying the change in the PTO clutch pressure accompanying the operation of the brake operating tool toward the stop release side is provided. It is characterized by having.

[Action and effect]
As described above, the transmission device for a work vehicle according to the present invention according to the solution means 4 includes the display means for displaying the change in the PTO clutch pressure accompanying the operation of the brake operation tool toward the stop release side. The degree of turning on and off of the PTO clutch, which cannot be recognized as a sensation, can be smoothly operated while recognizing with reference to the display state on the display means.

[Solution 5]
According to a fifth aspect of the present invention, there is provided a transmission device for a work vehicle comprising a change-over switch capable of intermittently connecting the brake operating tool and the PTO clutch.

[Action and effect]
Since there is a changeover switch that can connect / disconnect the brake operating tool and the PTO clutch, when this connection is not necessary, that is, when the work device is not connected to the PTO shaft, or the work device is connected to the PTO shaft. However, when the work device is always continuously driven and the intermittent operation of the drive is not necessary, the working device can be used without performing the control of the PTO clutch.
Therefore, there is an advantage that it is possible to select and use a driving state suitable for the working device connected to the PTO shaft.

It is a whole side view which shows the tractor comprised by the tiller specification. It is a diagram which shows a transmission system. It is a block diagram which shows a control system. It is operation | movement explanatory drawing of a side brake pedal. It is a graph which shows the relationship between the operation amount of a side brake, and PTO pressure. It is a top view which shows the arrangement | positioning state of a side brake pedal and a stop operation pedal. 1 is a hydraulic circuit diagram of a hydrostatic continuously variable transmission. It is explanatory drawing of the display screen which displays the pressure change of a PTO clutch.

[Overall configuration of work vehicle]
FIG. 1 shows a tractor configured as a rotary tiller specification, which is an example of a work vehicle including a transmission device according to the present invention.
This tractor is configured by connecting a rotary tiller 4 to a rear portion of a four-wheel drive tractor main machine 1 having a front wheel 2 and a rear wheel 3 so as to be movable up and down. The vehicle body of the tractor main unit 1 is configured as a monobody type in which an engine 5, a main clutch housing 6, a main transmission case 7, a mid case 8, and a transmission case 9 are directly connected in series. A front axle case 11 is supported by a front frame 10 connected to the engine 5 so as to be capable of rolling, and a front wheel 2 is supported by the left and right sides of the front axle case 11 so as to be steerable. 3 is pivotally supported. A link mechanism 13 that is driven up and down by a lift arm 12 is provided at the rear of the mission case 9, and the rotary tiller 4 is connected to the link mechanism 13.

[Configuration of transmission system]
FIG. 2 shows a transmission system in the tractor main unit 1. The output of the engine 5 is transmitted to the input shaft 16 provided in the main transmission case 7 through the main clutch 15, and the transmission power taken out from the output shaft 17 provided in the main transmission case 7 is converted into a gear-type auxiliary transmission. After being shifted in three stages by the device 18, it is transmitted to the left and right rear wheels 3 via the rear differential device 19 and the side brake 22. A part of the traveling system power changed by the auxiliary transmission 18 is taken out from the lower part of the transmission case 9, transmitted to the front axle case 11 via the transmission shaft 20, and left and right front wheels via the front differential device 21. 2 is transmitted.

  The main transmission case 7 is internally provided with a hydrostatic continuously variable transmission (HST) 23. The continuously variable transmission 23 includes a variable displacement hydraulic pump 23P configured in an axial plunger type and a hydraulic motor 23M, and changes the swash plate angle in the hydraulic pump 23P that is driven to rotate at a constant speed by the input shaft 16. Then, the output shaft 17 of the hydraulic motor 23M that receives the pressure oil is continuously rotated by forward rotation or reverse rotation by changing the discharge direction and discharge amount of the discharged pressure oil. Yes.

  The input shaft 16 extends rearward through the hydraulic pump 23P, and a part of the constant speed rotational power transmitted to the input shaft 16 is further rearward through a PTO clutch 24 built in the midcase 8. Then, the rotary tiller 4 is driven by a constant speed PTO power regardless of the traveling speed change.

The continuously variable transmission 23 (HST) is speed-controlled by hydraulic servo means, and its configuration is shown in FIGS.
The swash plate angle of the hydraulic pump 23P in the continuously variable transmission 23 is configured to be able to be changed in the forward and reverse directions by a return servo cylinder 30, and the swash plate angle is detected by a swash plate angle sensor 31 using a potentiometer. And input to the control device 32. The servo cylinder 30 is urged and returned by a pair of return springs 33 to a neutral position where the swash plate angle becomes zero, and a forward proportional control valve 34 and a reverse proportional control valve 35 connected to the control device 32. The servo cylinder 30 is expanded and contracted by hydraulic control via the.

  The proportional control valves 34 and 35 are biased to a return position where the servo cylinder 30 communicates with the tank when the energization control is not performed. When both the proportional control valves 34 and 35 are in the return position, the servo cylinder 30 is In a free state, the continuously variable transmission 23 returns to neutral. The pressure oil supply path from the pump 36 to the proportional control valves 34 and 35 is provided with a relief valve 37, which limits the maximum system pressure in the hydraulic servo means.

[Configuration of gear shifting operation system]
The tractor main unit 1 is equipped with a shift pedal 38 and a shift lever 39 as shift operating tools. The shift pedal 38 is disposed on the right side of the foot of the driver seat 14, and the shift lever 39 is disposed on the left side of the driver seat 14.
The speed change pedal 38 can be stepped forward and backward, and is mechanically urged to return to the neutral position by a cam mechanism (not shown). The depression position of the shift pedal 38 is detected by the potentiometer 40 and input to the control device 32. Information on the depression position of the shift pedal 38 detected by the potentiometer 40, feedback information from the swash plate angle sensor 31, and Based on detection information of a stop operation detection switch 61 that detects an operation of a stop operation pedal 60 described later, the proportional control valves 34 and 35 are controlled by servo control means 100 provided in the control device 32.
That is, the servo control means 100 controls the operation of the proportional control valves 34 and 35 so that the servo cylinder 30 is expanded and contracted according to the depression direction and the depression amount of the shift pedal 38 detected by the potentiometer 40. By making the swash plate angle corresponding to the depression of 38, stepless forward shift and reverse shift are performed.
When the potentiometer 40 detects the release of the shift pedal 38, the operation of the proportional control valves 34 and 35 is controlled to automatically return the shift pedal 38 to the neutral position, cut off the output of the driving thrust and stop the driving. To control.

The shift lever 39 is mechanically linked so that the shift pedal 38 can be operated only in the forward shift direction, and is supported so as to be able to hold friction at an arbitrary operation position. The operation position of the shift lever 39 is the shift position. It is detected by a potentiometer 40 that detects the operation position of the pedal 38. In a state where the shift lever 39 is held at the linkage release position n, the linkage between the shift lever 39 and the shift pedal 38 is released, and the shift pedal 38 can be depressed in the entire region from the forward range to the reverse range.
As the speed change lever 39 is operated forward from the linkage release position n shown in FIG. 3, the speed change pedal 38 is operated in the forward depression direction (forward speed increasing direction), and the speed change lever 39 is operated arbitrarily in the forward speed change range. By holding the friction at the position, the neutral return of the shift pedal 38 is prevented and held in an arbitrary forward shift range, and a constant speed forward travel at an arbitrary speed corresponding to the operation position of the shift lever 39 is performed. In the state where the shift pedal 38 is held at the intermediate position of the forward shift range by the shift lever 39, it is permitted to depress the shift pedal 38 in the further forward speed increasing direction. It returns to the speed set by the lever 39.

[Linkage configuration of travel braking and PTO clutch]
As shown in FIG. 6, in the vicinity of the shift pedal 38, a pair of brake pedals 41 serving as brake operation tools linked to the left and right side brakes 22 are provided in parallel on the left and right sides. The brake pedal 41 is linked to the operating arm 43 through a link mechanism 42.
The link mechanism 42 does not rotate the operating arm 43 only by operating one brake pedal 41 in the depressing direction, which is the travel stop direction, and only depresses both brake pedals 41 simultaneously. The operating arm 43 is configured to be rotated at an angle corresponding to the amount. The rotating angle of the operating arm 43 is detected by the potentiometer 44 and input to the control device 32.

The PTO clutch 24 is configured as a multi-plate friction clutch that is engaged when a hydraulic pressure is applied, and is turned off by a spring biasing force when the hydraulic pressure is released. Control is performed via an electromagnetic proportional control valve 45 connected to the control device 32.
A PTO clutch lever 46 is provided on the right side of the driver seat 14, the operation position of the PTO clutch lever 46 is detected by the PTO on / off switch 47, and the detection information is input to the control device 32. . In addition, for the control device 32, the state in which the PTO clutch 24 and the left and right side brakes 22 are linked and the linkage operation is released, and the PTO clutch 24 and the left and right side brakes 22 are independent of each other. A linkage state changeover switch 48 for switching the operation state is also connected.
The control device 32 controls the electromagnetic proportional control valve 45 based on the detection information of the potentiometer 44 for detecting the rotation angle of the operating arm 43, the PTO on / off switch 47, and the linkage state changeover switch 48. First PTO pressure control means 101 for outputting a signal is provided.

Therefore, when the PTO clutch lever 46 is operated to the “disengaged” position, the proportional control valve 45 is controlled so that the application of the hydraulic pressure is released, the PTO clutch 24 is in the clutch disengaged state, and the PTO clutch lever 46 is moved to “ When operated to the “ON” position, a control signal is output from the control device 32 to the proportional control valve 45 so that a predetermined high hydraulic pressure is applied, and the PTO clutch 24 enters the clutch engaged state.
When the linkage state changeover switch 48 is in the “off” state, the control device 32 controls the PTO clutch 24 regardless of the operation of the left and right brake pedals 41 according to the operation position of the PTO clutch lever 46. Is maintained in the “OFF” or “ON” state.
The PTO clutch is linked to the operation of the left and right brake pedals 41 only when the linkage state changeover switch 48 is operated to “ON” and the operation position of the PTO clutch lever 46 is “ON”. 24 is controlled as follows.

When the left and right brake pedals 41 are operated in the simultaneous depression state, the braking force of each side brake 22 increases as the depression amount of the brake pedal 41 increases, and the operation direction and the operation amount of the brake pedal 41. Thus, the clutch pressure of the PTO clutch 24 is controlled in association with the braking state.
First, each operation position in the depression direction which is the traveling stop direction of the brake pedal 41 shown in FIGS. 4 and 5 will be described.

  While the transmission lever 39 is held at an arbitrary forward position to set the forward speed and the PTO clutch lever 46 is operated to the “ON” position, as shown by the solid line in FIG. Is released and returned to the return position (a), both the side brakes 22 are in a brake release state, the forward proportional control valve 34 is energized and the servo cylinder 30 is actuated to a predetermined position, and is continuously variable. The transmission 23 is held in a forward shift state corresponding to the operation position of the shift lever 39. In addition, the first PTO pressure control means 101 outputs a control signal to the proportional control valve 45 to the PTO clutch 24 so that a high hydraulic pressure is supplied to the PTO clutch 24 to bring the clutch into an engaged state.

  If both the brake pedals 41 are depressed simultaneously from this state, the left and right side brakes 22 exert a braking action as the depression amount increases, and the servo cylinder 30 decelerates based on the rotation angle of the operating arm 43. The travel speed is gradually decreased from the forward speed set by the speed change lever 39.

  When the brake pedals 41 are simultaneously depressed to the preset first depression position (b), the servo control means 100 controls the proportional control valve 34 even though the shift lever 39 is held in the forward shift range. , 35 is cut off, the servo cylinder 30 is returned to the neutral position, the continuously variable transmission 23 is in the neutral state, and the traveling drive by the continuously variable transmission 23 is stopped. At this time, the PTO clutch 24 has hardly changed from the state where the clutch pressure is located at the return position (a) as shown in FIG. 5, and is kept at a constant high pressure and is in the clutch engaged state. .

As the brake pedals 41 are further depressed beyond the first depression position (b), the amount of depression of both brake pedals 41 increases and the braking force gradually increases, but the clutch pressure of the PTO clutch 24 is As shown in FIG. 5, the pressure is maintained at a constant pressure while maintaining almost no change from the state of being located at the return position (a), and is maintained in the entering state. However, when both the brake pedals 41 are depressed to the second depression position (c) set in advance as an operation position at which the maximum braking force of each side brake 22 can be obtained, the detection from the potentiometer 44 that detects this is performed. In response to the signal, the first PTO pressure control means 101 outputs a control signal so as to operate the proportional control valve 45 to the oil passage open side, and the clutch pressure of the PTO clutch 24 is rapidly reduced. The force disappears and the clutch is completely disengaged.
That is, in the operation in the depression direction of both the brake pedals 41, the braking force of each side brake 22 increases according to the operation amount of both the brake pedals 41, but the clutch pressure of the PTO clutch 24 is the second depression position ( There is almost no change until just before c), and the clutch-engaged state is maintained without the half-clutch state. Then, when the vehicle is stepped over to the second stepping position (c) beyond the first stepping position (b) where the traveling is stopped, the clutch pressure of the PTO clutch 24 is rapidly reduced and the clutch is disengaged. This second depression position (c) is the position for starting the disengagement operation of the PTO clutch (24) accompanying the operation of both brake pedals 41 toward the travel stop side.

  Note that when the front arm 2 is steered and only one brake pedal 41 on the inner side of the turn is depressed to make a small turn, the operating arm 43 does not turn, so that the deceleration control and the PTO clutch 24 release control described above are performed. Never done.

  When both brake pedals 41 are depressed to the third depression position (d) which is the depression limit position beyond the second depression position (c), the relief valve 37 of the hydraulic servo means is activated based on the rotation of the operating arm 43. The system is forcibly released mechanically, the system pressure of the hydraulic servo means is reduced to zero, and pressure oil is supplied to the servo cylinder 30 regardless of the control operation state of the proportional control valves 34 and 35 for traveling speed change. The continuously variable transmission 23 is neutralized and released.

  In this way, when both brake pedals 41 are greatly depressed to the third depression position (d), the pressure oil supply to the servo cylinder 30 is forcibly released and the continuously variable transmission 23 is returned to the neutral state. Even if a situation occurs in which the proportional control valves 34 and 35 do not return to the return position due to a failure in the electric system, the stepless transmission 23 can be neutrally returned as long as both brake pedals 41 are depressed to the limit. You can stop running.

Next, each operation position in the depression release direction that is the travel stop release direction of the brake pedal 41 shown in FIGS. 4 and 5 will be described.
The clutch pressure of the PTO clutch 24 associated with the operation in the release release direction of the brake pedal 41 is between the return position (a) and the second depression position (c), and the PTO clutch 24 associated with the operation in the depression direction. The clutch pressure changes differently.

  That is, as shown in FIG. 5, in the middle of returning both brake pedals 41 from the second depression position (c) to the first depression position (b), the first PTO pressure control means 101 of the control device 32 is controlled by the proportional control valve 45. The control signal is output so as to maintain the oil passage open state due to, and both brake pedals 41 are returned while the clutch disengaged state of the PTO clutch 24 is maintained. At this time, both the proportional control valves 34 and 35 are also de-energized, the servo cylinder 30 is returned to the neutral position, and the running is stopped.

As shown in FIG. 5, in the middle of returning both brake pedals 41 from the first depression position (b) to the return position (a ′) slightly before the return position (a), the brakes 41 In accordance with the detection signal from the potentiometer 44 that detects the operation position of the pedal 41, the first PTO pressure control means 101 of the control device 32 outputs a control signal so as to adjust the degree of oil passage opening of the proportional control valve 45. Thus, the clutch pressure of the PTO clutch 24 is changed according to the operation position of both brake pedals 41 so that the clutch pressure gradually increases as both brake pedals 41 are operated to the return side.
When it is detected that both the brake pedals 41 have reached the position before return (a ′), the first PTO pressure control means 101 outputs a control signal so as to close the oil passage of the proportional control valve 45, and The control valve 45 is operated so that a predetermined high hydraulic pressure is applied to the PTO clutch 24. That is, while the brake pedal 41 is returned from the first depression position (b) to the position before return (a ′), the PTO clutch 24 changes so as to gradually increase the clutch pressure in the half-clutch state. When the position before return (a ′) is reached, the clutch is completely engaged.
The first depressing position (b) is the starting operation start position of the PTO clutch 24 that accompanies the operation of the brake pedal 41 toward the depressing release side, and the return position (a ′) is toward the depressing release side of the brake pedal 41. Is the position where the PTO clutch 24 is engaged when the operation is completed.

  In the region where the brake pedal 41 returns from the position before return (a ′) to the return position (a), the PTO clutch 24 is maintained in the engaged state, and the braking force gradually decreases as the brake pedals 41 are returned. Thus, the braking force completely disappears at the return position (a). That is, this return position (a) is the end position of the travel stop canceling operation.

  With the control device 32 including the first PTO pressure control means 101 described above, the change in the clutch pressure of the PTO clutch 24 with respect to the operation amount of the brake pedal 41 serving as the brake operating tool becomes gentler on the clutch engagement side than on the clutch disengagement side. Thus, the control means for controlling is configured.

  The amount of swash plate operation by which the swash plate of the hydraulic pump 23P that has been operated to return to the neutral position is operated forward with the return operation of both brake pedals 41 is determined by the operating positions of the transmission pedal 38 and the transmission lever 39. It is set based on the detection signal of the potentiometer 40 to be detected. That is, the servo control means 100 sets the swash plate angle set based on the detection signal of the potentiometer 40 as the target speed position of the hydrostatic continuously variable transmission 23, and reaches this target speed position. The swash plate angle of the hydraulic pump 23P is changed. At this time, the speed at which the servo cylinder 30 changes the swash plate angle of the hydraulic pump 23P is linked to the speed of the return operation of both brake pedals 41.

[Stop operation tool]
As shown in FIG. 7, the hydrostatic continuously variable transmission 23 having a first oil passage A or the like that becomes a high pressure side when moving forward and a second oil passage B that becomes a low pressure side when moving forward includes a continuously variable transmission. A stop operation pedal 60 is provided as a stop operation tool for releasing the hydraulic pressure of the first oil passage A which is a drive circuit of the device 23 and interrupting the transmission of power to the traveling device.
That is, the return oil path 63 is provided across the first oil path A and the oil tank T, which are high pressure during forward travel in the continuously variable transmission 23, the unload valve 64 is provided in the return oil path 63, and the return oil path 63. A throttle valve 65 is provided between the unload valve 64 and the oil tank T in FIG. The stop operation pedal 60 is configured to release the hydraulic pressure of the first oil passage A of the continuously variable transmission 23 by the unload valve 64 to cut off power transmission to the traveling device.

  A detection switch 61 for detecting a power transmission cut-off state due to depression of the stop operation pedal 60 is provided, and a detection signal of the detection switch 61 is transmitted to the control device 32. The control device 32 includes second PTO pressure control means 102 that operates the proportional control valve 45 based on whether or not the stop operation pedal 60 is depressed, which is detected by the detection switch 61, and this second PTO pressure control means 102. Is configured to control the clutch pressure of the PTO clutch 24 as the stop operation pedal 60 is depressed.

The second PTO pressure control means 102 determines that the depressing operation pedal 60 is depressed when the detection switch 61 that detects one of the two on / off states is in the on state, and the detection switch 61 is in the off state. At a certain time, it is determined that the depressing state of the stop operation pedal 60 is released.
In the second PTO pressure control means 102, when the detection switch 61 is switched from the OFF state to the ON state, the return position (a) to the second depression position (c) in the PTO pressure control curve shown in FIG. A control command is output to the proportional control valve 45 so as to perform the control corresponding to the control in between.
On the contrary, when the detection switch 61 is switched from the on state to the off state, it corresponds to the control from the second depression position (c) to the return position (a) in the PTO pressure control curve shown in FIG. A control command is output to the proportional control valve 45 so as to perform control.

  At this time, in the detection switch 61 that detects the state of power transmission interruption by the stop operation pedal 60, the change in the amount of depression of the brake pedal 41 described above occurs from the return position (a) to the second depression position (c). Corresponding information cannot be detected, but instead, as a preset set time, a time corresponding to the time interval from when braking is started until the aircraft stops is stored in the control device 32. The second PTO pressure control means 102 is configured to adjust the clutch pressure from the return position (a) to the second depression position (c) within the set time.

  Then, in the second PTO pressure control means 102, the first depression position (b) set between the return position (a) and the second depression position (c) in FIG. 5 in the return stroke of the stop operation pedal 60. ) And the position corresponding to the position before return (a ′), the ratio of the time from the second depression position (c) to the first depression position (b) with respect to the set time, and the second depression position ( The ratio of the time from c) to the position before return (a ′) indicates that the operation stroke of the brake pedal 41 between the return position (a) and the second depression position (c) and the second depression position (c ) To the first depression position (b), or the ratio of the operation stroke of the brake pedal 41 from the second depression position (c) to the position before return (a ′). Ratio It is set to be.

One of the second PTO pressure control means 102 and the first PTO pressure control means 101 is selected to control the proportional control valve 45, and the both brake pedals The proportional control valve 45 is controlled by the first PTO pressure control means 101 in a state where the potentiometer 44 detects the rotation angle of the operating arm 43 by operating 41.
Therefore, in the state where the proportional control valve 45 is controlled by the first PTO pressure control means 101 as described above, even if the detection switch 61 detects that the stop operation pedal 60 has been depressed, it takes precedence over this. The first PTO pressure control means 101 controls the PTO clutch pressure. Further, even if the detection switch 61 detects that the stop operation pedal 60 is depressed first and the PTO clutch pressure is controlled by the second PTO pressure control means 102, both the brake pedals 41 are operated. When the detection signal from the potentiometer 44 is sent to the first PTO pressure control means 101, the control by the second PTO pressure control means 102 is stopped, and the control by the first PTO pressure control means 101 is preferentially performed. .

[Others]
FIG. 8 is an explanatory diagram of a display screen 51 displayed on the meter display 50 provided in the control panel portion of the tractor as display means for displaying the pressure change of the PTO clutch. From the “stop” position on the right side in the figure to the “turn” position on the left side, the degree of increase or decrease in the PTO clutch pressure can be displayed as an image in a bar graph shape.
This display screen 51 is displayed on the meter display 50 based on the detection signal of the potentiometer 44 so that both brake pedals 41 are displayed in the middle of returning from the second depression position (c) to the return position (a). It is controlled by display control means 103 that outputs a signal.
Further, the display signal from the display control means 103 may be displayed by directly detecting the clutch pressure of the PTO clutch 24. However, in this display control means 103, based on the detection signal from the potentiometer 44, Assuming that the operation stroke of the brake pedal 41 corresponds to the PTO clutch pressure, a display signal is output so that the value converted from the detection result of the operation stroke of the brake pedal 41 is displayed as the PTO clutch pressure. The display screen 51 is interrupted and displayed at a predetermined location on the meter display 50.

[Other Embodiment 1]
In the above embodiment, as shown in FIG. 5, the clutch pressure of the PTO clutch 24 is almost changed until just before the second depression position (c) in the operation in the depression direction of both brake pedals 41 as the brake operation tool. If the clutch is engaged without maintaining a half-clutch state and is depressed to the second depressing position (c) beyond the first depressing position (b) where travel is stopped, the clutch of the PTO clutch 24 Control is performed so that the pressure is rapidly reduced and the clutch is disengaged. When the brake pedal 41 is operated in the depressing release direction, while the brake pedal 41 is returned from the first depressing position (b) to the position before returning (a ′), the PTO clutch 24 is gradually moved to the clutch pressure in the half-clutch state. Is changed so as to increase.
However, the present invention is not necessarily limited to such control that the clutch pressure is changed. For example, the clutch pressure of the PTO clutch 24 is set to the second depression position (c) by operating the brake pedals 41 in the depression direction. It is possible to change appropriately, for example, by changing the position slightly more slightly before the second stepping position (c) so that the clutch is completely disengaged.
In short, the degree of change in the PTO clutch pressure in the operation in the depressing direction of both brake pedals 41 as a brake operating tool is more rapid than the degree of change in the PTO clutch pressure in the operation in the depressing direction of both brake pedals 41. Thus, hysteresis is generated in the control characteristics between the depression direction of the brake pedal 41 and the depression release direction so that the braking operation and the change in the PTO clutch pressure are associated with each other to improve the operability and the remaining tillage portion. Anything that can reduce the degree of wear of the PTO clutch 24 while utilizing the advantage that can be reduced can be used.

[Second embodiment]
The braking operation tool is not limited to the pair of left and right side brake pedals 41 but may be a dedicated braking brake pedal. Further, not only the pedal but also a brake operation lever may be used.

[3 of another embodiment]
The display screen 51 displayed on the meter display 50 is not limited to an image that can display the degree of increase or decrease in the PTO clutch pressure. For example, the amount of depression of the brake pedal 41, the PTO clutch 24, the left and right side brakes 22 The on / off state of the link state changeover switch 48 for switching the link state may be displayed.
Further, when displaying the degree of increase / decrease in the PTO clutch pressure, a single pressure fluctuation may not be displayed, but may be displayed when a predetermined pressure continues for a predetermined time or longer.

  As a transmission device for a work vehicle to which the present invention is applied, a transmission device for a rice transplanter or a combiner, or a transmission device for a mower or a snowplow may be used.

24 PTO clutch 25 External power take-off shaft 32 Control means 41 Braking operation tool 48 Changeover switch 50 Display means a End position of travel stop release operation a 'PTO clutch engagement operation end position b PTO clutch engagement operation start position c PTO clutch Cutting operation start position

Claims (5)

A work including a travel drive system for transmitting engine power to the travel device and a work device drive system for transmitting engine power to the external power take-off shaft, and a brake operation tool for applying a braking action to the travel of the aircraft A vehicle transmission,
A hydraulically operated PTO clutch for intermittently transmitting power to an external power take-off shaft in the work device drive system;
The PTO clutch and the braking operation tool are configured to change the clutch pressure of the PTO clutch to a clutch disengaged state with an increase in the operation amount to the travel stop side by the brake operation tool, and the operation amount to the travel stop side. The clutch operating force and the PTO clutch are linked so that the clutch pressure is changed with the decrease in the clutch operation state, and the braking operation tool and the PTO clutch are connected to the braking operation tool when operated to the travel stop side. After the braking operation is started, the PTO clutch is disengaged. In the operation of the braking operation tool toward the travel stop release side, the PTO clutch engagement operation is started before the braking operation by the braking operation tool is released. The operation timing is set so that
And a control means for controlling the change in the clutch pressure of the PTO clutch with respect to the operation amount of the brake operating tool to be more gentle on the clutch engagement side than on the clutch disengagement side. .   The position at which the PTO clutch engagement operation ends when the braking operation tool is moved toward the travel stop release side is greater than the end position of the travel stop release operation of the braking operation tool during the operation stroke of the braking operation tool. The transmission device for a work vehicle according to claim 1, wherein the transmission device is set closer to the side.   The PTO clutch disengagement operation start position associated with the operation of the braking operation tool toward the travel stop side is the PTO clutch engagement operation start position associated with the operation of the braking operation tool toward the travel stop release side during the operation stroke of the braking operation tool. 3. The work vehicle transmission device according to claim 1, wherein the work vehicle transmission device is set closer to a travel stop operation end side of the braking operation tool.   The transmission device for a work vehicle according to any one of claims 1 to 3, further comprising display means for displaying a change in the PTO clutch pressure accompanying the operation of the braking operation tool toward the stop release side.   The transmission device for a work vehicle according to any one of claims 1 to 4, further comprising a changeover switch capable of intermittently connecting the braking operation tool and the PTO clutch.

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