JP5124528B2 - Work vehicle load control device - Google Patents

Description

  The present invention relates to a transmission device for transmitting power to a travel drive system and a load control device for a work vehicle that includes an external power take-off shaft as a drive system different from the travel drive system. The present invention relates to a load control device for a work vehicle including control means for controlling a drive system transmission so as to be decelerated.

As a load control device for a work vehicle as described above, a device having a structure shown in the following [1] is conventionally known as means for avoiding engine stall due to overload.
[1] In a work vehicle equipped with a hydrostatic continuously variable transmission as a transmission for transmitting power to a travel drive system, a reduction amount of the engine speed from a set speed is detected as an engine load, and the detected load Accordingly, the swash plate position of the hydrostatic continuously variable transmission is controlled to the load reducing side (see Patent Document 1).

JP 2007-92952 A (paragraphs [0057], [0058], FIG. 6, FIG. 9)

As described above, in a work vehicle in which the engine load is detected and the swash plate position of the hydrostatic continuously variable transmission of the traveling drive system is controlled to the deceleration side according to the detected load, the engine load is reduced. When detecting and controlling the swash plate position to the deceleration side according to the detected load, the total load is determined as the engine load regardless of the engine load factor, and the traveling drive system deceleration operation is performed. It was something to do. For this reason, it is effective in performing a deceleration operation corresponding to the engine load to prevent engine stall, but the work is performed by installing a work device on the external power take-off shaft, which is a drive system different from the travel drive system. When doing so, there are the following problems.
That is, when the engine load is caused by both the driving drive system and the PTO work device, even if the swash plate position of the hydrostatic continuously variable transmission of the traveling drive system is controlled to the deceleration side, Since the load on the PTO work device is not reduced, the engine load may not be sufficiently reduced. In this case, the greater the load on the PTO work device, the more the engine speed decreases. Therefore, when a work device that uses a drive at a relatively high speed rotation is used, it may be difficult to drive the work device well.

  It is an object of the present invention to drive with a power from an external power take-off shaft, which is a drive system different from the travel drive system, in controlling the transmission device of the travel drive system to be decelerated as the engine load increases. An object of the present invention is to provide a load control device for a work vehicle that can be controlled so that the work device operates stably.

[Solution 1]
The load detection device for a work vehicle according to the present invention includes a load detection unit that detects an engine load, a shift position detection unit that detects a shift operation position of a transmission that transmits power to a traveling drive system, and a shift operation of the transmission. Shift operation means for performing the control, and based on detection signals of the load detection means and the shift position detection means, the operation of the shift operation means is controlled so that the transmission is decelerated as the engine load increases. A load control device for a work vehicle including a control means for outputting a control signal to perform operation of a PTO work device to which engine power is transmitted via an external power take-off shaft that is separate from the travel drive system. Work state detecting means for determining presence / absence is provided, and the control means is configured such that when the operating state of the PTO work device is detected, the deceleration operation amount by the speed change operation means is P The output state of the control signal to the shift operation means based on the detection signal of the work state detection means is changed so as to be larger than the deceleration operation amount when the non-operating state of the O-system work device is detected. It is comprised by these.

[Operation and effect of invention according to Solution 1]
That is, according to this solution 1, the amount of deceleration operation by the speed change operation means when the operating state of the PTO work device is detected by determining whether the PTO work device is operating is determined as the PTO work device. The output state of the control signal to the shift operation means is changed so as to be larger than the deceleration operation amount when the inactive state is detected. Therefore, when the engine load is caused by both the driving force of the traveling drive system and the PTO work device, even if the engine load is the same value, it is determined that the load is caused only by the load of the traveling drive system. In this case, the speed change operation means is operated with a larger deceleration operation amount than the deceleration operation amount in this case, so that the traveling deceleration more than the amount necessary for preventing the engine stall is performed, and the decrease in the engine speed is suppressed as much as possible. .
As a result, the engine speed reduction is suppressed, so that the PTO work device can maintain a good driving state, and the fluctuation in the engine speed is small, which contributes to an improvement in fuel consumption. This is also advantageous.
And when the engine load is caused only by the load of the traveling drive system, even if the engine load is the same value, the traveling deceleration of the amount necessary for preventing the engine stall is performed. At this time, the PTO work device is in a non-operating state, so that it does not matter. Therefore, there is no inconvenience that traveling speed is reduced more than necessary and traveling performance is deteriorated.

[Solution 2]
The invention according to Solution 2 is the work vehicle load detection device shown in Solution 1, wherein the transmission that transmits power to the traveling drive system is a hydrostatic continuously variable transmission, and the swash plate angle of the variable displacement pump The swash plate angle operation means that changes the operation steplessly constitutes the speed change operation means, the swash plate position detection means detects the operation position of the swash plate of the variable displacement pump, and the control means comprises The amount of deceleration operation of the swash plate by the pump swash plate angle operating means when the operating state of the PTO work device is detected is the same as that of the swash plate when the non-operating state of the PTO work device is detected. It is characterized in that the output state of the control signal to the pump swash plate angle operation means is changed based on the detection signal of the work state detection means so as to be larger than the deceleration operation amount. .

[Operation and effect of invention according to Solution 2]
That is, according to the solution means 2, in the case where a hydrostatic continuously variable transmission device is used as the transmission device for transmitting power to the traveling drive system, the solution means 1 is controlled by controlling the deceleration operation amount of the swash plate. Similar to the point described in the above, the PTO system work device can maintain a good driving state by suppressing the decrease in the engine speed, and the fluctuation in the engine speed can improve the fuel efficiency. There is an advantage of contributing to the above, and an advantage of avoiding a problem that the traveling performance is reduced more than necessary and the traveling performance is deteriorated.

[Solution 3]
The invention relating to the solution means 3 is the load detecting device for the work vehicle shown in the solution means 1 or 2, wherein the control means has a speed reduction operation speed by the speed change operation means when the operating state of the PTO work device is detected. The output state of the control signal to the speed change operation means is changed based on the detection signal of the work state detection means so as to be larger than the deceleration operation speed when the non-operation state of the PTO work device is detected. It is characterized in that it is configured as described above.

[Operation and effect of invention according to Solution 3]
That is, according to the solution means 3, the speed reduction operation speed by the speed change operation means when the operating state of the PTO work device is detected, and the speed reduction operation when the non-operation state of the PTO work device is detected. Since the speed is greater than the speed, the operating time, which tends to increase as the deceleration operation amount increases in the operating state of the PTO work device, can be shortened by increasing the deceleration operation speed. The decrease in the number can be suppressed as much as possible.
Therefore, there is an advantage that it is possible to further suppress a decrease in the engine speed and maintain a good driving state of the PTO work device.

[Solution 4]
The invention relating to the solution means 4 is the load detecting device of the work vehicle shown in the solution means 1, 2, or 3, wherein the control means is an engine detected based on detection signals from the load detection means and the shift position detection means. It is characterized in that the output state of the control signal to the shift operation means is changed so that the deceleration operation speed by the shift operation means increases as the load increases.

[Operations and effects of invention according to Solution 4]
That is, according to the solution means 4, the larger the engine load is, the greater the speed reduction operation speed by the speed change operation means is. Therefore, when the engine load is large, the engine speed tends to decrease. By performing the operation, a decrease in the engine speed during the operation can be suppressed as much as possible.
Therefore, the deceleration operation time, which tends to become longer as the deceleration operation amount increases in the operating state of the PTO work device, is shortened by increasing the deceleration operation speed according to the engine load, and also in this respect There is an advantage that a decrease in the number can be suppressed.

Whole side view which shows the working vehicle to which the load control apparatus of this invention is applied Schematic explanatory diagram showing the power transmission system of the work vehicle Vertical sectional view of the main part showing the transmission structure of the work vehicle Horizontal sectional view of the main part showing the transmission structure of the work vehicle Hydraulic circuit diagram Block diagram showing the control system Chart showing the correlation between the operating position of the shift pedal and the operating position of the pump swash plate Chart showing correlation between pump swash plate deviation and target operating speed Chart showing correlation between operating position of pump swash plate and engine speed Chart showing correlation between pump swash plate deviation and target operating speed Chart showing operation of pump swash plate during motor swash plate switching operation The chart which shows correlation with the operation position of the pump swash plate and engine speed in another embodiment

Hereinafter, an example of an embodiment of the present invention will be described based on the drawings.
[Overall configuration of work vehicle]
FIG. 1 shows an entire side surface of a tractor as an example of a work vehicle to which a load control device of the present invention is applied.
In this tractor, front wheels 3 are provided on the left and right of a front frame 2 that supports the vibration isolation of the engine 1, and rear wheels 5 are provided on the left and right of a transmission case 4 combined with the engine 1. A boarding operation unit 8 is formed by arranging a steering wheel 6 and a driver seat 7 on the upper side.

As shown in FIGS. 2 to 4, power from the engine 1 is transmitted to a hydrostatic continuously variable transmission 10 that functions as a main transmission via a dry main clutch 9 and the like. The driving power extracted from the hydrostatic continuously variable transmission 10 is a gear-type transmission 11 that functions as a sub-transmission that is configured to be able to change gears between high, middle, and low, and a front wheel differential. It is transmitted to the left and right front wheels 3 and the left and right rear wheels 5 via the device 12 or the rear wheel differential device 13.
Further, the working power extracted from the hydrostatic continuously variable transmission 10 is transmitted to the power take-off shaft 15 via the hydraulic work clutch 14 and the like.

  The transmission case 4 includes a first casing portion 4A that houses the main clutch 9 and the like, a second casing portion 4B that houses the hydrostatic continuously variable transmission 10 and the like, a third casing portion 4C that houses the work clutch 14 and the like, and The fourth casing portion 4D that houses the gear-type transmission 11 and the like is connected.

[Configuration of hydrostatic continuously variable transmission]
As shown in FIGS. 2 to 5, the hydrostatic continuously variable transmission 10 includes an axial plunger type variable displacement pump 16, an axial plunger type variable displacement motor 17, and the like housed in the second casing portion 4 </ b> B. The non-shifting power from the variable displacement pump 16 is output as working power, and the shifting power from the variable displacement motor 17 is output as traveling power. Then, the charge oil from the charge pump 21 driven by engine power is supplied to the closed circuit 20 formed by connecting the variable displacement pump 16 and the variable displacement motor 17 by the first oil passage 18 and the second oil passage 19. The charging oil passage 22 and the check valve 23 are supplied.

  As shown in FIGS. 1 and 4 to 6, the tractor includes a swash plate 16 </ b> A (hereinafter referred to as a pump) of the variable displacement pump 16 based on an operation of a neutral return type shift pedal 24 provided in the boarding operation unit 8. A servo control mechanism 25 (an example of a shift operation means) for operating a swash plate is provided.

As shown in FIGS. 4 to 6, the servo control mechanism 25 is a hydraulic pump cylinder 26 (an example of pump swash plate angle operating means) that operates the pump swash plate 16A in a stepless manner. A servo valve 27 for controlling the flow of oil, a regulator valve 28 for maintaining the hydraulic pressure for the servo valve 27 and the like at a set pressure are provided.
The servo control mechanism 25 includes a pedal sensor 29 composed of a potentiometer that detects the operation position of the shift pedal 24, and a swash plate sensor 30 composed of a potentiometer that detects the operation position of the pump swash plate 16A from the operation amount of the pump cylinder 26. (An example of the swash plate position detecting means and the shift position detecting means) and a control device 31 (an example of the control means) including a microcomputer to which detection signals such as the pedal sensor 29 and the swash plate sensor 30 are input. It is comprised so that.

  The pump cylinder 26 is housed in the second casing portion 4B together with the forward deceleration spring 32 and the reverse deceleration spring 33 that urge the pump swash plate 16A back to the neutral position. By supplying the hydraulic oil to the forward shift oil chamber 34 of the pump cylinder 26, the pump swash plate 16A is operated in the forward acceleration direction against the urging force of the forward deceleration spring 32, and the reverse shift is performed. When the hydraulic oil is supplied to the oil chamber 35, the pump swash plate 16A is operated in the reverse acceleration direction against the urging force of the reverse deceleration spring 33.

The servo valve 27 is an electromagnetic forward proportional valve 36 that controls the flow of hydraulic fluid to the forward shift oil chamber 34 of the pump cylinder 26 and the hydraulic fluid to the reverse shift oil chamber 35 of the pump cylinder 26. And an electromagnetic reverse proportional valve 37 for controlling the flow of the motor.
The regulator valve 28 is configured to distribute the hydraulic oil fed from the power steering supply pump 38 to the work clutch 14 and the hydraulic power steering device 39 at a set pressure suitable for each operation. A supply oil passage 41 for the servo valve 27 is connected to the pressure port 28A of the regulator valve 28 to which the supply oil passage 40 for the work clutch 14 is connected.
An electromagnetic clutch operation valve 75 is provided in the supply oil passage 40 for supplying pressure oil to the work clutch 14, and an oil passage opening / closing operation is performed by the clutch operation valve 75 based on a command from the control device 31 described later. By doing so, the work clutch 14 can be turned on and off.

[Configuration of control device]
<Pump control>
As shown in FIG. 6, the control device 31 operates map data (an example of correlation data) indicating the correlation between the operation position of the shift pedal 24 and the operation position of the pump swash plate 16A, and the pump swash plate 16A. A pump swash plate control means 31A equipped with a storage control program is provided.
The control program for operating the pump swash plate 16A by the pump swash plate control means 31A is based on the stored map data, the detected value of the pedal sensor 29, the detected value of the swash plate sensor 30, and the like. The operation of the valve 36 or the reverse proportional valve 37 is controlled, and the pump swash plate 16A is operated.

  In the map data of the pump swash plate control means 31A, the operation amount from the neutral position of the pump swash plate 16A to the forward acceleration direction increases as the operation amount from the neutral position of the speed change pedal 24 to the forward acceleration direction increases. As the operation amount from the neutral position of the speed change pedal 24 to the reverse acceleration direction becomes larger, the operation amount from the neutral position of the pump swash plate 16A to the reverse speed increase direction becomes larger. This corresponds to the operation position of the plate 16A (see FIG. 7).

  The control program of the pump swash plate control means 31A is based on the stored map data and the detection value of the pedal sensor 29, and the operation position of the pump swash plate 16A corresponding to the operation position of the transmission pedal 24 detected by the pedal sensor 29. Is set as the target operation position of the pump swash plate 16A. Based on the set target operation position and the detected value of the swash plate sensor 30, the forward proportional valve 36 or the reverse proportional is set so that the target operation position of the pump swash plate 16A matches the actual operation position. The operation of the valve 37 is configured to be controlled. With this control operation, the vehicle body can be moved forward or backward at a speed corresponding to the operation position of the shift pedal 24.

That is, in the servo control mechanism 25, the pump swash plate control means 31A controls the operation of the forward proportional valve 36 or the reverse proportional valve 37 based on the detected value of the pedal sensor 29 and the detected value of the swash plate sensor 30. Thus, the forward proportional valve 36 or the reverse drive that operates the pump cylinder 26 by operating the pump swash plate 16A of the hydrostatic continuously variable transmission 10 and the pressure port 28A of the regulator valve 28 is operated. The pump cylinder 26 is directly driven by the output pressure of the proportional valve 37 for direct drive.
As a result, the pump cylinder 26 is driven by the output pressure from the charge oil passage 22 where the pressure fluctuates due to pressure fluctuations in the closed circuit 20 of the hydrostatic continuously variable transmission 10 or fluctuations in engine speed. Thus, a stable servo pilot pressure can be obtained, and the operation control of the pump cylinder 26 can be performed with high accuracy. As a result, while the servo control mechanism 25 is configured as an inexpensive direct acting type, the vehicle body is moved forward or backward at a speed corresponding to the operation position of the shift pedal 24 based on the detection of the pedal sensor 29 and the detection of the swash plate sensor 30. The vehicle speed control can be performed with high accuracy.

  The control device 31 includes a target operation position of the pump swash plate 16A and an actual operation position based on the target operation position of the pump swash plate 16A set by the pump swash plate control means 31A and the detection value of the swash plate sensor 30. , A plurality of map data (an example of correlation data) indicating the correlation between the deviation and the operation speed of the pump swash plate 16A, the map data, and the calculation result of the calculation program And an operation speed setting means 31B that stores a control program for setting a target operation speed of the pump swash plate 16A.

Each map data of the operation speed setting means 31B includes an actual operation position of the pump swash plate 16A detected by the swash plate sensor 30 and a target operation position of the pump swash plate 16A set by the pump swash plate control means 31A. The deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are made to correspond to each other so that the operation speed of the pump swash plate 16A increases when the deviation is large (see FIG. 8).
Further, each map data of the operation speed setting means 31B indicates that the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A at the time of reverse travel is such that the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A at the time of forward travel. It is also set so as to be slower than the operation speed, and the deviation of the pump swash plate 16A corresponds to the operation speed of the pump swash plate 16A (see FIG. 8).

  That is, the control program of the operation speed setting means 31B sets the operation speed of the pump swash plate 16A calculated based on the stored map data and the calculation result of the calculation program as the target operation speed of the pump swash plate 16A. The set target operation speed is output to the pump swash plate control means 31A.

As described above, the control program of the pump swash plate control means 31A includes the forward proportional valve 36 or the reverse drive so that the pump swash plate 16A is operated at the target operation speed set by the operation speed setting means 31B in the vehicle speed control. The operation of the proportional valve 37 is configured to be controlled. By this control operation, it is possible to suppress the occurrence of hunting while improving the responsiveness of the pump swash plate 16A to the operation of the shift pedal 24. As a result, the vehicle speed can be quickly increased to the speed corresponding to the operation position of the shift pedal 24. Can be reached accurately.
Further, the operation speed of the pump swash plate 16A during reverse travel is slower than the operation speed of the pump swash plate 16A during forward travel, and the speed change operation of the hydrostatic continuously variable transmission 10 during reverse travel is performed forward. The speed change operation of the hydrostatic continuously variable transmission 10 is performed at the time of reverse travel, which is performed more slowly than the speed change operation of the hydrostatic continuously variable transmission 10 at the time and difficult to grasp the speed sensation compared to the time of forward travel. It becomes easy.

  As shown in FIG. 6, the control device 31 includes data changing means 31C having a control program for changing map data selected and used by the operation speed setting means 31B. The data changing unit 31C is configured to appropriately change the map data used by the operation speed setting unit 31B according to various situations, as described below.

The data changing unit 31C associates the map data to be used with the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A based on the operation position of the adjustment dial 42 including a potentiometer provided in the boarding operation unit 8. It is configured to change to the map data.
That is, the map data to be used is converted to the pump swash plate 16A with respect to the deviation of the pump swash plate 16A so that the operation of the pump swash plate 16A is performed more rapidly as the operation position of the adjustment dial 42 is largely changed from the reference position to the quick side. The deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are changed to map data so that the operation speed of the plate 16A is increased.
Further, the map data to be used is converted to the pump swash plate 16A with respect to the deviation of the pump swash plate 16A so that the operation of the pump swash plate 16A is performed more gradually as the operation position of the adjustment dial 42 is largely changed from the reference position to the smooth side. The deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are changed to map data so that the operation speed of the plate 16A becomes slow.

  In other words, by operating the adjustment dial 42, the operation feeling when shifting the hydrostatic continuously variable transmission 10 with the shift pedal 24 can be changed according to the driver's preference. The feeling and speed change operability can be improved.

  Further, the data changing means 31C operates the pump swash plate 16A more gently as the temperature of the hydraulic oil is lower based on the detection of the oil temperature sensor 43 that detects the temperature of the hydraulic oil supplied to the regulator valve 28. As shown, the map data to be used is the difference between the pump swash plate 16A and the pump swash plate 16A so that the operation speed of the pump swash plate 16A becomes slower with respect to the deviation of the pump swash plate 16A as the oil temperature decreases. Change to map data corresponding to.

  In other words, the lower the operating oil temperature, the higher the operating oil viscosity and the lower the responsiveness of the hydraulically operated pump swash plate 16A. The target operation speed of the plate 16A is set to a low speed. Accordingly, when the temperature of the hydraulic oil is not taken into account, the pump swash plate 16A is more likely to be invited as the temperature of the hydraulic oil decreases. It is possible to suppress the occurrence of hunting due to a decrease in responsiveness.

The data changing means 31C is configured to select map data to be used by detecting the gear position of the gear type transmission 11 from the operation position of the auxiliary transmission lever 44 provided in the boarding operation unit 8.
That is, the operation position of the auxiliary transmission lever 44 is detected by the auxiliary transmission sensor 45 comprising a potentiometer, and based on the detection result, the operation of the pump swash plate 16A is performed as the gear stage of the gear transmission 11 is higher. The map data to be used is pump swash plate 16A so that the operation speed of pump swash plate 16A increases with respect to the deviation of pump swash plate 16A in accordance with the increase of the gear stage of gear type transmission 11. And the map data in which the deviation of the pump and the operation speed of the pump swash plate 16A are made to correspond to each other.

  That is, the target operation speed of the pump swash plate 16A is set to a higher speed considering that the response to the operation of the pump swash plate 16A becomes slower as the gear stage of the gear type transmission 11 is set to the higher speed side. Thus, regardless of the gear position of the gear type transmission 11, the operation feeling when the hydrostatic continuously variable transmission 10 is shifted with the shift pedal 24 can be made the same.

  Further, the data changing unit 31C is configured to change the map data to be used based on the detection of the operation speed detecting unit 46 that detects the operation speed of the shift pedal 24. That is, the operation of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A according to the decrease in the operation speed of the transmission pedal 24 so that the operation of the pump swash plate 16A is performed more slowly as the operation speed of the speed change pedal 24 becomes slower. The map data is changed so that the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A correspond to each other so that the speed becomes slow.

  As a result, even when the speed change pedal 24 is operated at a very low speed, the pump swash plate 16A follows the speed change pedal 24 with a delay in the operation of the speed change pedal 24. Since it is possible to avoid the possibility that the operation of the plate 16A catches up and the stepped speed change operation is performed stepwise, the speed change operation of the hydrostatic continuously variable transmission 10 by the speed change pedal 24 is smoothly performed regardless of the operation speed of the speed change pedal 24. Yes.

  The operation speed detecting means 46 includes a pedal sensor 29 and a calculation program provided in the data changing means 31C so as to calculate the operation speed of the shift pedal 24 based on the detection of the pedal sensor 29. .

  When the operation position of the pump swash plate 16A is detected as being in the neutral position or in the vicinity of the neutral position based on the detection of the swash plate sensor 30, the data changing unit 31C operates the pump swash plate 16A slowly. As shown in FIG. 4, the map data to be used are the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A so that the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A is limited to the low speed side. Change to map data corresponding to.

  As a result, when the pump swash plate 16A is positioned at or near the neutral position, the pump swash plate 16A rapidly increases with the stepping operation even if the gear pedal 24 is suddenly depressed. Since the pump swash plate 16A is slowly increased without being operated at a high speed, even if the speed change pedal 24 is suddenly depressed greatly, it is possible to prevent a sudden start or a sudden acceleration from a very low speed. You can start and accelerate.

The data changing means 31C detects the operating position of the brake pedal 48 provided in the boarding operation unit 8 so that the operating speed of the pump swash plate 16A is changed in accordance with the braking state of a braking device (not shown). The map data to be used can be selected based on the detection of the brake sensor 49 composed of a potentiometer.
As a result, when the braking device is in a braking operation, the map data to be used has a high operating speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A in consideration of a decrease in the vehicle speed due to the braking operation of the braking device. Thus, the map data is changed so that the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A correspond to each other.

  Thus, the interference between the hydrostatic continuously variable transmission 10 and the braking device during the braking operation in which the depressing operation of the shift pedal 24 is released and the brake pedal 48 is depressed can be suppressed. The durability of the device 10 and the braking device can be improved.

  Based on the detection of the vehicle speed sensor 50 that detects the vehicle speed from the output rotational speed of the gear type transmission 11, the data changing means 31C is configured so that the operation of the pump swash plate 16A is gently performed when the vehicle speed is low. The map data to be used is made to correspond to the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A so that the operation speed of the pump swash plate 16A becomes slower with respect to the deviation of the pump swash plate 16A as the vehicle speed decreases. Change to map data.

  As a result, the response of the pump swash plate 16A to the operation of the speed change pedal 24 is reduced during low-speed traveling, and therefore the inching operation at the vehicle speed required during low-speed traveling is facilitated.

The data changing means 31C determines the operation direction of the pump swash plate 16A and the pump swash plate 16A so that the operation speed of the pump swash plate 16A differs between the operation to the speed increasing side and the operation to the deceleration side of the pump swash plate 16A. Change to map data corresponding to the operation speed.
That is, based on the detection of the swash plate sensor 30 and the target operation position of the pump swash plate 16A set by the pump swash plate control means 31A, the target operation position of the pump swash plate 16A is increased more rapidly than the actual operation position. When set to the side, the map data is changed to correspond to the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A so that the operation of the pump swash plate 16A is performed gently. Further, when the target operation position of the pump swash plate 16A is set to be decelerated from the actual operation position, the deviation of the pump swash plate 16A and the pump swash plate 16A can be quickly operated. The map data is changed to correspond to the operation speed of the plate 16A.
Further, when the target operation position of the pump swash plate 16A and the actual operation position sandwich the neutral position, the map data to be used is stored in the pump swash plate so that the pump swash plate 16A can be operated more quickly. In accordance with the positional relationship between the target operation position of 16A and the actual operation position, the map data is changed to correspond to the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A.

  Thereby, the operation feeling can be changed between the speed increasing operation and the speed reducing operation of the hydrostatic continuously variable transmission 10 by the shift pedal 24. In addition, the increase in engine load due to the speed increasing operation of the hydrostatic continuously variable transmission 10 can be suppressed, and the reduction of the engine load due to the deceleration operation of the hydrostatic continuously variable transmission 10 can be promoted. The possibility that the engine 1 is stopped due to the shift operation of the hydrostatic continuously variable transmission 10 by the shift pedal 24 can be reduced. Further, it is possible to perform the forward / reverse switching operation of the hydrostatic continuously variable transmission 10 with the speed change pedal 24 in which the operation delay of the pump swash plate 16 </ b> A with respect to the speed change pedal 24 is suppressed.

The data changing means 31C generates map data in which the operation time of the pump swash plate 16A and the operation speed of the pump swash plate 16A are associated with each other so that the operation speed of the pump swash plate 16A is different at the start of travel and when the travel is stopped. change.
That is, based on the detection of the swash plate sensor 30 and the target operation position of the pump swash plate 16A set by the pump swash plate control means 31A, at the start of traveling when the pump swash plate 16A is speeded up from the neutral position, The map data in which the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are made to correspond to each other so that the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A becomes slow according to the start-up.
Further, when the travel is stopped when the pump swash plate 16A is decelerated from the acceleration position to the neutral position, map data to be used is determined according to the stop time so that the pump swash plate 16A is operated quickly. In order to increase the operation speed of the pump swash plate 16A with respect to the deviation, the map swash plate 16A is changed to map data in which the operation speed of the pump swash plate 16A is made to correspond.

  Thereby, the operation feeling can be changed between when the travel is started by the operation of the shift pedal 24 and when the travel is stopped, and the possibility of sudden start at the start of travel can be suppressed.

  Incidentally, as map data of the operation speed setting means 31B, the map data for forward movement for setting the speed change operation speed during forward movement and the map data for reverse movement for setting the speed change operation speed during reverse movement are provided. The data changing unit 31C may be configured to change the map data to be used based on the detection of the pedal sensor 29.

  By the way, when the neutral return operation (deceleration operation) of the pump swash plate 16A is performed by the forward deceleration spring 32 and the reverse deceleration spring 33, the pump swash plate 16A is driven regardless of the deceleration operation of the shift pedal 24 due to inertia during trailer work. It may be difficult to perform a deceleration operation toward the neutral position of the swash plate 16A.

  Therefore, the pump swash plate control means 31 </ b> A is based on the detection of the pedal sensor 29 and the detection of the swash plate sensor 30, regardless of the deceleration operation of the speed change pedal 24, and the pump swash plate by the forward deceleration spring 32 or the reverse deceleration spring 33. When it is detected that the deceleration operation of 16A is not performed, the forward proportional valve 36 on the opposite side to the side used when the pump swash plate 16A is accelerated to the current operation position or the reverse proportional By controlling the operation of the valve 37, the pump cylinder 26 is forcibly operated in a direction in which the pump swash plate 16A is decelerated toward the neutral position.

  As a result, even if the pump swash plate 16A is not decelerated regardless of the decelerating operation of the shift pedal 24 due to inertia during trailer work, the forward proportional valve 36 or reverse proportional by the pump swash plate control means 31A. The pump swash plate 16A can be decelerated by forcibly operating the pump cylinder 26 by controlling the operation of the valve 37.

  The control device 31 includes a detection of a set rotation detection sensor 52 including a potentiometer that detects a set rotation speed of the engine 1 from an operation position of an accelerator lever 51 provided in the boarding operation unit, and a rotation sensor that detects the rotation speed of the engine 1. 47 based on the detection of the engine rotation ratio (the set rotation speed of the engine 1 set by the accelerator operating tool such as the accelerator lever 51 provided in the control unit and the actual rotation of the engine 1 detected by the rotation sensor 47). Based on a calculation program that calculates the correlation between the engine speed and the operation position of the pump swash plate 16A, the calculation result of the calculation program, and the map data. The automatic shift control process for controlling the operation of the forward proportional valve 36 or the reverse proportional valve 37 to automatically operate the pump swash plate 16A. Automatic pump swash plate control means 31D equipped stores and Gram are provided.

  In the automatic pump swash plate control means 31D, when the pump swash plate 16A is automatically operated in accordance with the decrease rate of the engine speed from the set rotational speed, the relationship between the engine rotation ratio and the operation position of the pump swash plate 16A. As map data for setting the travel map data (see line L1 in FIG. 9) in which the relationship between the engine speed suitable for avoiding engine stall during travel and the pump swash plate 16A is set, and the travel map data Also, two types of map data are provided: work map data (see line L2 in FIG. 9) in which the rate of change in the operation position of the pump swash plate 16A with respect to the change in engine speed is increased.

The automatic transmission control program provided in the automatic pump swash plate control means 31D is a PTO clutch sensor 74 comprising a potentiometer that detects the operating position of the PTO clutch lever 73 provided in the boarding operation section 8 (an example of a work state determination means). On the basis of the signal from the control signal, an operation signal for performing on / off operation of the work clutch 14 is output to the clutch operation valve 75, and a determination program for determining the on / off state, and a pump swash plate 16A corresponding to the engine speed ratio. Based on one of the two types of map data, that is, based on the travel map data when the work clutch 14 is disengaged, and based on the work map data when the work clutch 14 is engaged. And a calculation program to be set.
Then, the detection value of the swash plate sensor 30 for detecting the actual operation position of the pump swash plate 16A and the control target position set by the calculation program are detected, and the control target position of the pump swash plate 16A and the actual operation are detected. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so as to match the position.

In FIG. 9, the vertical axis represents the engine rotation ratio, and the horizontal axis represents the swash plate operation position.
The engine rotation ratio on the vertical axis means the set rotation speed of the engine 1 set by the accelerator operating tool such as the accelerator lever 51 provided in the control unit and the actual rotation speed of the engine 1 detected by the rotation sensor 47. Is the ratio. 100% on the vertical axis indicates that the set rotational speed of the engine 1 and the actual rotational speed of the engine 1 are the same value. In many cases, a work vehicle such as a tractor equipped with this type of work clutch 14 is used by setting the maximum rotation speed as a set rotation speed or a position close to the maximum rotation speed in order to make full use of the capacity of the work vehicle. There are many.

  The swash plate operation position on the horizontal axis indicates the ratio of the operation position of the pump swash plate 16A within the operation range of the pump swash plate 16A, where the maximum tilt angle of the pump swash plate 16A is 100%. That is, it corresponds to the swash plate angle corresponding to the control target position set by the calculation program for the maximum tilt angle of the pump swash plate 16A, or the operation position of the pump swash plate 16A actually detected by the swash plate sensor 30. The swash plate angle is shown as a ratio.

A plurality of map data indicating the correlation between the engine rotation ratio used in the automatic pump swash plate control means 31D and the operation position of the pump swash plate 16A will be described.
The line L1 shown in FIG. 9 is a line indicating the correlation between the engine rotation ratio and the speed change operation position of the pump swash plate 16A. The PTO clutch sensor 74 including a potentiometer that detects the operation position of the PTO clutch lever 73 is It is a line represented by the map data for driving | running | working which shows the correlation in the state which has detected the disconnection state of the clutch.
The line L2 in the figure is a line indicating the correlation between the engine rotation ratio and the speed change operation position of the pump swash plate 16A, and a PTO clutch sensor 74 comprising a potentiometer that detects the operation position of the PTO clutch lever 73. It is a line represented by work map data indicating a correlation in a state where the engagement state of the work clutch 14 is detected.

More specifically, as shown in FIG. 9, the change rate of the pump swash plate 16 </ b> A is larger than the change rate of the engine speed in the first region h <b> 1 having a large engine speed ratio among the preset engine speed regions h. Thus, the engine speed and the operation position of the pump swash plate 16A are associated with each other.
In the second region h2 where the engine speed ratio is smaller than that in the first region h1, the engine swash plate 16A has a change rate smaller than the change in the first region h1 with respect to the change rate of the engine speed. The rotation ratio is associated with the operation position of the pump swash plate 16A.
In the third region h3 where the engine speed ratio is smaller than the second region h2, the engine swash plate 16A has a change rate larger than the change in the second region h2 with respect to the change rate of the engine speed. The rotational speed is associated with the operation position of the pump swash plate 16A.

  Then, the control program of the automatic pump swash plate control means 31D is such that the PTO clutch sensor 74 comprising a potentiometer for detecting the operation position of the PTO clutch lever 73 detects the disengagement state of the work clutch 14 and the line L1 Based on the travel map data, the operation position of the pump swash plate 16A corresponding to the engine rotation ratio calculated by the calculation program is set as the control target position of the pump swash plate 16A, and the set control target position and the swash plate sensor 30 are set. Based on this detection, the operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so that the control target position of the pump swash plate 16A matches the actual operation position.

  By this control operation, the driver considers the traveling load during the loader work that travels by connecting the tractor with the front loader A that is not a working device driven by the power of the PTO system, or when traveling on the road. Even if the operation is not performed, it is possible to perform load control so that engine stall due to overload can be prevented, thereby improving operability and workability.

  When the PTO clutch sensor 74, which is a potentiometer that detects the operation position of the PTO clutch lever 73, detects the engaged state of the work clutch 14, the calculation program is based on the work map data of the line L2. The operation position of the pump swash plate 16A corresponding to the calculated engine speed is set as the control target position of the pump swash plate 16A, and the pump swash plate 16A is based on the set control target position and the detection of the swash plate sensor 30. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so that the control target position and the actual operation position coincide with each other.

In this control operation, the control target position of the pump swash plate 16A is set to a light load side which is larger than necessary for avoiding engine stall when the engine speed is equal to or lower than the predetermined speed.
That is, as shown in FIG. 9, when the engine rotation ratio is reduced to the level of the line x in the figure, the control target position of the pump swash plate 16A is determined as described above when the disengagement state of the work clutch 14 is detected. Based on the travel map data of the line L1, it is set at a position y1 corresponding to the point a1 on the line L1.
However, even when the engine speed ratio is reduced to the level of the line x in the figure, the control target position of the pump swash plate 16A is the work position for the line L2 in the state where the engagement state of the work clutch 14 is detected. Based on the map data, the position y2 corresponding to the point a2 on the line L2 is set.
Thus, the swash plate angle of the pump swash plate 16A is changed to the position y2 where the operating position of the pump swash plate 16A is larger than the position y1 necessary to avoid engine stall and the traveling load is reduced. .

As a result, among the loads acting on the engine 1, the load from the traveling system driven via the hydrostatic continuously variable transmission 10 is greatly reduced, which effectively reduces the rotational speed due to the overload of the engine 1 itself. Can be suppressed. Accordingly, the rotational speed on the engine 1 side is maintained at a high speed, and a decrease in the rotational speed of the PTO work device (not shown) to which the driving force is transmitted from the power take-off shaft 15 is suppressed.
The PTO work device here is a work device that is driven by the driving force taken out from the power take-off shaft 15 separately from the traveling system. For example, a mower for mowing, a snow removal device, and the like are relatively high speed. It is the working device which is rotationally driven by.

As shown in FIG. 10, the control program for the automatic pump swash plate control means 31D is set by the actual operation position of the pump swash plate 16A detected by the swash plate sensor 30 and the automatic pump swash plate control means 31D. When the deviation from the control target position of the pump swash plate 16A is large, the deviation of the pump swash plate 16A is made to correspond to the operation speed of the pump swash plate 16A so that the operation speed of the pump swash plate 16A is increased. It is.
The speed at which the operation speed of the pump swash plate 16A increases corresponding to the magnitude of the deviation is detected when the working clutch 14 is engaged, compared to when the working clutch 14 is detected to be disengaged. The case is set to be faster.
In addition to this, the operation moving direction of the pump swash plate 16A is detected by the swash plate sensor 30, and the operation to the side where the pump swash plate 16A is tilted (acceleration side) is performed as shown by a two-dot chain line in the figure. The operation direction of the pump swash plate 16A and the pump swash plate 16A so that the operation speed of the pump swash plate 16A toward the return side (deceleration side) of the pump swash plate 16A is faster than the case where it is performed. The operation speed of the plate 16A is made to correspond.

<Motor control>
The tractor is equipped with a switching mechanism 54 for switching the swash plate 17A (hereinafter referred to as a motor swash plate) of the variable capacity motor 17 between two levels.

  The switching mechanism 54 includes a hydraulic motor cylinder 55 (an example of motor operating means) that operates the motor swash plate 17A, a switching valve 56 that controls the flow of hydraulic oil to the motor cylinder 55, and the switching valve 56. An electromagnetic control valve 57 to be operated, a high pressure selection valve 58 that enables supply of hydraulic oil from the closed circuit 20 of the hydrostatic continuously variable transmission 10 to the control valve 57, and a lower left portion of the steering wheel 6 are provided. The control device 31 includes a switching lever 59, a lever sensor 60 including a switch for detecting an operation position of the switching lever 59, and a control program for performing a switching operation of the motor swash plate 17A based on the detection of the lever sensor 60. The motor swash plate control means 31E is provided.

  The motor cylinder 55 is detachably mounted in the second casing portion 4 </ b> B of the transmission case 4 together with the variable capacity motor 17.

  Based on the detection of the lever sensor 60, the motor swash plate control means 31E performs height switching control for switching the motor swash plate 17A from the high speed position to the low speed position when the switching lever 59 is operated to the low speed position. At the same time, the corresponding indicator lamp 61 is turned on, and when the switching lever 59 is operated to the high speed position, low / high switching control for switching the motor swash plate 17A from the low speed position to the high speed position is performed. The indicator lamp 62 is turned on.

  In other words, when the traveling speed is significantly reduced due to an increase in traveling load during uphill traveling or work traveling with the switching lever 59 set to the high speed position, the switching lever 59 is switched from the high speed position to the low speed position. Thus, the driving force for the left and right front wheels 3 and the left and right rear wheels 5 can be increased, so that the climbing traveling and the working traveling can be continued.

  The indicator lights 61 and 62 are provided on an operation panel 63 provided below the steering wheel 6.

  In the elevation switching control, the motor swash plate control means 31E first stores the current operation position of the pump swash plate 16A based on the detection of the swash plate sensor 30, and sets the deceleration target operation position of the pump swash plate 16A. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so that the pump swash plate 16A is decelerated at a predetermined operation speed to the calculated deceleration target operation position. Then, after the pump swash plate 16A reaches the deceleration target operation position, the return accelerating operation at the preset operation speed to the operation position stored in the pump swash plate 16A and the motor swash plate at the preset operation speed are performed. The operation of the forward proportional valve 36 or the reverse proportional valve 37 and the operation of the control valve 57 are controlled so that the switching operation from the high speed position to the low speed position of 17A is performed at the same time [FIG. 11 (a)].

  In the low / high switching control, first, based on the detection of the swash plate sensor 30, the current operation position of the pump swash plate 16A is stored, and the deceleration target operation position of the pump swash plate 16A is calculated, and the calculation is performed. The deceleration operation at the preset operation speed of the pump swash plate 16A to the target deceleration operation position and the switching operation from the low speed position to the high speed position of the motor swash plate 17A at the preset operation speed are performed simultaneously. The operation of the forward proportional valve 36 or the reverse proportional valve 37 and the operation of the control valve 57 are controlled. Thereafter, the pump swash plate 16A is configured to control the operation of the forward proportional valve 36 or the reverse proportional valve 37 so that the pump swash plate 16A is restored and accelerated at a preset operation speed to the stored operation position [ See FIG. 11 (b)].

  That is, when the motor swash plate 17A is switched from the high speed position to the low speed position, not only the switching operation but also the speed increasing operation of the pump swash plate 16A is simultaneously performed, so that the motor swash plate 17A is changed from the high speed position to the low speed position. The change in the capacity of the variable capacity motor 17 that occurs in response to the switching operation can be offset by the change in the capacity of the variable capacity pump 16 that occurs in response to the speed increase operation of the pump swash plate 16A. When the motor swash plate 17A is switched from the low speed position to the high speed position, not only the switching operation but also the speed reduction operation of the pump swash plate 16A is performed at the same time, so that the motor swash plate 17A is moved from the low speed position to the high speed position. The change in the capacity of the variable capacity motor 17 that occurs with the switching operation can be offset by the change in the capacity of the variable capacity pump 16 that occurs with the deceleration operation of the pump swash plate 16A. Accordingly, it is possible to mitigate the shift shock generated by the switching operation of the motor swash plate 17A.

  Although not shown, when a high-speed response valve is employed instead of the switching valve 56 and the motor swash plate control means 31E performs the switching operation of the motor swash plate 17A, the operation speed of the motor swash plate 17A is By changing the duty of the high-speed response valve so as to decrease, the change in the capacity of the variable capacity motor 17 that occurs when the motor swash plate 17A is switched is slowed down, and the shift shock caused by the change in the capacity of the variable capacity motor 17 May be relaxed.

  Incidentally, when the motor swash plate control means 31E is in the traveling state in which the motor swash plate 17A is switched to the high speed position, the height switching control is performed in conjunction with the braking operation of the braking device based on the detection of the brake sensor 49. It may be configured to improve braking performance.

  Further, when the motor swash plate control means 31E is in a traveling state in which the motor swash plate 17A is switched to the high speed position, the motor swash plate control means 31E is involved in the deceleration operation of the shift pedal 24 based on the detection of the pedal sensor 29 and the detection of the swash plate sensor 30. First, when it is detected that the deceleration operation of the pump swash plate 16A by the forward deceleration spring 32 or the reverse deceleration spring 33 is not performed, the high / low switching control is performed, and the inertia at the time of trailer work, etc. When the pump swash plate 16A is not decelerated regardless of the decelerating operation of the shift pedal 24, the decelerating operation by the high / low switching control may be performed.

  Further, when the motor swash plate control means 31E is switched to the high speed position of the motor swash plate 17A, the operation speed of the shift pedal 24 is faster than the preset operation speed based on the detection of the operation speed detection means 46. In this case, the high / low switching control may be performed to prevent sudden start or acceleration.

  As shown in FIG. 1, the switching lever 59 is extended so that its operation end is located in the vicinity of the left portion of the steering wheel 6, and thereby, the motor swash plate is released without releasing the hand from the steering wheel 6. 17A high / low switching operation can be performed. In addition, when the front loader A (see FIG. 6) is connected to the tractor, the motor tilt is not released without releasing the front loader operating lever (not shown) provided on the right side of the steering wheel 6. The plate 17A can be switched between high and low.

  When the data changing means 31C is equipped with a height sensor 70 including a potentiometer that detects the height position of the work device in a work state in which the work device such as the front loader A is connected and installed so as to be able to move up and down, Based on the detection of the height sensor 70, the pump swash plate control means 31A is used when the working device is raised to a height position higher than a preset height (for example, a height position exceeding the vehicle height). The map data indicating the correlation between the operation position of the speed change pedal 24 and the operation position of the pump swash plate 16A is changed to map data for raising the working device stored in the pump swash plate control means 31A. It is configured.

  The map data for raising the working device is obtained by setting the operation position of the pump swash plate 16A relative to the operation position of the shift pedal 24 to the low speed side as compared to the map data used normally (see FIG. 7). By using this map data by the pump swash plate control means 31A, the vehicle speed is limited to the low speed side, and high speed traveling in an unstable state in which the working device is raised above the set height is prevented. Will be.

  As shown in FIGS. 4 and 5, the servo control mechanism 25 includes a servo valve 27, a regulator valve 28, and a swash plate sensor 30, together with an oil temperature sensor 43, on the right side of the second casing portion 4 </ b> B in the transmission case 4. It is housed in a casing 71 that is detachably bolted and is unitized as one block as an electronic operation mechanism 72.

  In the electronic servo control mechanism 25, reference numeral 77 shown in FIG. 4 is a linkage arm used as a feedback arm that spans between the pump cylinder 26 and the swash plate sensor 30.

  Further, reference numerals 78 and 79 shown in FIG. 5 are formed on the joint surface of the second casing part 4B with the casing 71 when the electronic operation mechanism 72 is bolted to the right side part of the second casing part 4B. It is a communication port formed in the joint surface with the 2nd casing part 4B of the casing 71 so that it may connect corresponding to the communication ports 80 and 81. FIG.

  As shown in FIGS. 4 and 5, the switching mechanism 54 includes a switching valve 56, a control valve 57, and a high pressure selection valve 58 that are detachably bolted to the left side portion of the second casing portion 4 </ b> B in the transmission case 4. It is housed in the casing 83 and unitized as one block as the operation mechanism 84.

  5 are connected corresponding to the respective communication ports 86 to 91 of the second casing portion 4B when the switching mechanism 54 is bolted to the left side portion of the second casing portion 4B. Thus, it is a communicating port formed in the joint surface with the 2nd casing part 4B of the casing 83. FIG.

[Other Embodiment 1]
In the above embodiment, the automatic pump swash plate control means 31D provided in the control device 31 is configured to automatically operate the pump swash plate 16A with the rate of decrease of the engine speed from the set speed. Although not limited to this, as shown in FIG. 12, the automatic pump swash plate control means 31D sets the maximum speed or a speed close to it as the set engine speed, and sets the set speed. The pump swash plate 16A may be configured to be automatically operated in accordance with the amount of decrease from the number.

  In the automatic pump swash plate control means 31D provided in the control device 31 in this embodiment, a set rotation detection sensor 52 including a potentiometer that detects the set rotation speed of the engine 1 from the operation position of the accelerator lever 51 provided in the boarding operation unit. And a calculation program for calculating a reduction amount (hereinafter referred to as an engine drop amount) of the engine rotational speed from the set rotational speed based on detection of the rotational speed of the engine 1 and detection of the rotational sensor 47 that detects the rotational speed of the engine 1. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is based on a plurality of map data indicating the correlation between the engine speed and the operation position of the pump swash plate 16A, the calculation result of the calculation program, and the map data. And an automatic shift control program for automatically operating the pump swash plate 16A. About the other structure of the control apparatus 31, it has the same structure as the control apparatus 31 demonstrated by previous embodiment.

  In the automatic pump swash plate control means 31D, when the pump swash plate 16A is automatically operated in accordance with the reduction amount of the engine speed from the set rotational speed, the relationship between the engine rotational speed and the operation position of the pump swash plate 16A. As map data for setting the travel map data (see line L1 in FIG. 12) in which the relationship between the engine speed suitable for avoiding engine stall during travel and the pump swash plate 16A is set, and the travel map data Also, two types of map data are provided: work map data (see line L2 in FIG. 12) in which the rate of change in the operation position of the pump swash plate 16A with respect to the change in engine speed is increased.

The automatic transmission control program provided in the automatic pump swash plate control means 31D is based on a signal from a PTO clutch sensor 74 comprising a potentiometer that detects an operation position of a PTO clutch lever 73 provided in the boarding operation unit 8. An operation signal for performing on / off operation of the clutch 14 is output to the clutch operation valve 75, a determination program for determining the on / off state, and a control target position of the pump swash plate 16A corresponding to the engine speed are set to 2 A calculation program that is set based on any one of the various types of map data, that is, based on the travel map data when the work clutch 14 is disengaged, and based on the work map data when the work clutch 14 is engaged. ing.
Then, the detection value of the swash plate sensor 30 for detecting the actual operation position of the pump swash plate 16A and the control target position set by the calculation program are detected, and the control target position of the pump swash plate 16A and the actual operation are detected. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so as to match the position.

A plurality of map data indicating the correlation between the engine speed used in the automatic pump swash plate control means 31D and the operation position of the pump swash plate 16A will be described.
The line L0 shown in FIG. 12 is not directly related to the control of the operation position of the pump swash plate 16A, but the hydrostatic continuously variable transmission in which the high pressure relief of the hydrostatic continuously variable transmission 10 is jetted by the traveling load. It is an engine stall performance line which shows that an engine speed and the gear shifting operation position of the pump swash plate 16A are balanced when the transmission 10 is at a maximum load. This engine stall performance is determined by the output torque of the engine 1, the pressure of the hydrostatic continuously variable transmission 10, and the operation position (swash plate angle) of the pump swash plate 16A.

The line L1 shown in FIG. 12 is a line indicating the correlation between the engine speed and the speed change operation position of the pump swash plate 16A. The PTO clutch sensor 74 including a potentiometer that detects the operation position of the PTO clutch lever 73 is It is a line represented by the map data for driving | running | working which shows the correlation in the state which has detected the disconnection state of the clutch.
Also, line L2 in the figure shows a PTO clutch sensor 74 comprising a potentiometer that detects the operation position of the PTO clutch lever 73 among the lines indicating the correlation between the engine speed and the speed change operation position of the pump swash plate 16A. It is a line represented by work map data indicating a correlation in a state where the engagement state of the work clutch 14 is detected.

More specifically, as shown in FIG. 12, the change amount of the pump swash plate 16 </ b> A is larger than the change amount of the engine speed in the first region h <b> 1 where the engine drop amount is small in the preset engine rotation region h. Thus, the engine speed and the operation position of the pump swash plate 16A are associated with each other.
In the second region h2 where the engine drop amount is larger than that in the first region h1, the engine swash plate 16A changes with respect to the engine speed change amount so that the change amount becomes smaller than the change in the first region h1. The rotational speed is associated with the operation position of the pump swash plate 16A.
In the third region h3 where the engine drop amount is larger than that in the second region h2, the engine swash plate 16A has a change amount larger than the change in the second region h2 with respect to the change amount of the engine speed. The rotational speed is associated with the operation position of the pump swash plate 16A.

  As shown in FIG. 12 above, the two types of map data used by the automatic pump swash plate control means 31D detect data that maps the engine stall performance line L0 and the disengagement state of the work clutch 14. The data representing the correlation between the engine speed in the state and the speed change operation position of the pump swash plate 16A is mapped, and the engine speed and the pump skew in the state in which the engagement state of the work clutch 14 is detected. Among the data obtained by mapping the line L2 indicating the correlation with the speed change operation position of the plate 16A, the map is composed of travel map data obtained by mapping the line L1 and work map data obtained by mapping the line L2. ing.

  Then, the automatic transmission control program of the automatic pump swash plate control means 31D reads the line when the PTO clutch sensor 74 composed of a potentiometer that detects the operation position of the PTO clutch lever 73 detects the disengagement state of the work clutch 14. Based on the driving map data of L1, the operation position of the pump swash plate 16A corresponding to the engine speed calculated by the calculation program is set as the control target position of the pump swash plate 16A, and the set control target position and swash plate are set. Based on the detection of the sensor 30, the operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so that the control target position of the pump swash plate 16A matches the actual operation position. Yes.

  By this control operation, the driver considers the traveling load during the loader work that travels by connecting the tractor with the front loader A that is not a working device driven by the power of the PTO system, or when traveling on the road. Even if the operation is not performed, it is possible to perform load control that can prevent engine stall due to overload.

  That is, regarding the prevention of engine stall, on the line L1 of the travel map data, as shown by a point p1 in FIG. 12, the engine speed and the operation position of the pump swash plate 16A are on the engine stall performance line L0. If the control is performed so that the engine is positioned, effective control using the engine output to the maximum can be performed without engine stall. However, in such a control, the engine output is effectively used while avoiding engine stall, and therefore the engine speed may be greatly reduced in order to secure the output. Therefore, when using a working device that is desired to be used while maintaining a stable high speed of the engine speed, the driving speed of the working device may be too low to drive the working device satisfactorily.

Therefore, in the present invention, the engine speed and the operation position of the pump swash plate 16A are controlled as follows based on the operating state of the work clutch 14.
That is, when the PTO clutch sensor 74, which is a potentiometer that detects the operation position of the PTO clutch lever 73, detects the engaged state of the work clutch 14, the calculation program is based on the work map data of the line L2. The operation position of the pump swash plate 16A corresponding to the calculated engine speed is set as the control target position of the pump swash plate 16A, and the pump swash plate 16A is based on the set control target position and the detection of the swash plate sensor 30. The operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled so that the control target position and the actual operation position coincide with each other.

In this control operation, the control target position of the pump swash plate 16A is set to the region inside (light load side) beyond the point p2 on the engine stall performance line L0 when the engine speed is equal to or lower than the predetermined speed. Therefore, the load acting on the hydrostatic continuously variable transmission 10 is smaller than when the pump swash plate 16A is positioned on the engine stall performance line L0.
As a result, among the loads acting on the engine 1, the load from the traveling system driven via the hydrostatic continuously variable transmission 10 is greatly reduced, which effectively reduces the rotational speed due to the overload of the engine 1 itself. Can be suppressed. Accordingly, the rotational speed on the engine 1 side is maintained at a high speed, and a decrease in the rotational speed of the PTO work device (not shown) to which the driving force is transmitted from the power take-off shaft 15 is suppressed.
The PTO work device here is a work device that is driven by the driving force taken out from the power take-off shaft 15 separately from the traveling system. For example, a mower for mowing, a snow removal device, and the like are relatively high speed. It is the working device which is rotationally driven by.

Considering the case where the engine speed has decreased to the level of the line x in FIG. 12, in the state in which the disengagement state of the work clutch 14 is detected, the control target position of the pump swash plate 16A is the line. Based on the travel map data of L1, the position is set to a position y1 corresponding to the point a1 on the line L1.
On the other hand, in a state where the engagement state of the work clutch 14 is detected, the speed change operation position of the pump swash plate 16A is set to a position y2 corresponding to the point a1 on the line L2 based on the travel map data of the line L2. Is set.

  In this way, even when the amount of decrease in the engine speed is the same, when the work clutch 14 is in the engaged state, the operation position of the pump swash plate 16A is more than the position y1 necessary for avoiding the engine stall, compared with the disengaged state. The swash plate angle of the pump swash plate 16A is changed to the position y2 where the traveling load is greatly reduced.

[Second embodiment]
The travel drive transmission is not limited to the hydrostatic continuously variable transmission 10 but may be configured using a gear transmission type transmission or a transmission mechanism such as CVT. In this case, the speed change operation means for performing the speed change operation may be configured to be appropriately operated using a shift operation tool instead of the pump swash plate angle operation means 26 and the motor operation means 55. An electric cylinder, an electric motor, a hydraulic motor, or the like may be employed as a power source for operating the shift operation tool.

[3 of another embodiment]
In the above-described embodiment, both the deceleration operation amount and the deceleration operation speed of the pump swash plate 16A when the engaged state of the work clutch 14 is detected are larger than when the disconnected state of the work clutch 14 is detected. However, the present invention is not limited to this. For example, when the engaged state of the work clutch 14 is detected, the deceleration operation amount of the pump swash plate 16A is detected when the disengaged state of the work clutch 14 is detected. The speed of the deceleration operation of the pump swash plate 16A may be approximately the same as when the disengagement state of the work clutch 14 is detected.

  The load control device for a work vehicle in the present invention is not limited to the tractor shown in the embodiment, and various work vehicles including a work device driven by an output from a power take-off shaft separately from the traveling drive system, for example, The present invention can be applied to a mower, a snowplow, a chemical sprayer, a rice transplanter, or the like.

1 Engine 10 Hydrostatic continuously variable transmission (transmission)
14 Working Clutch 15 Power Extraction Shaft 16 Variable Displacement Pump 16A Swash Plate 17 Variable Displacement Motor 24 Shift Pedal 25 Servo Control Mechanism (Shift Operation Unit)
26 Cylinder for pump (pump swash plate angle operating means)
30 Swash plate position detection means (shift position detection means)
31 Control device (control means)
31A Pump swash plate control means 31B Operation speed setting means 31C Data change means 31D Automatic pump swash plate control means 47 Rotation sensor (load detection means)
55 Motor operating means 74 PTO clutch sensor (working state detecting means)

Claims (4)

A load detecting means for detecting engine load; a shift position detecting means for detecting a shift operation position of a transmission that transmits power to the travel drive system; and a shift operation means for performing a shift operation of the transmission,
Control means for outputting a control signal for controlling the operation of the speed change operation means based on the detection signals of the load detection means and the speed change position detection means so that the speed change device is decelerated as the engine load increases. A load control device for a work vehicle equipped with,
A working state detecting means for determining whether or not the PTO working device to which the engine power is transmitted via an external power take-off shaft that is separate from the traveling drive system;
The control means is such that a deceleration operation amount by the shift operation means when the operating state of the PTO work device is detected is smaller than a deceleration operation amount when the non-operation state of the PTO work device is detected. A work vehicle load control device configured to change an output state of a control signal to the shift operation means based on a detection signal of the work state detection means so as to increase. The transmission that transmits power to the traveling drive system is a hydrostatic continuously variable transmission, and the speed change operation means is configured by the pump swash plate angle operation means that changes the swash plate angle of the variable displacement pump continuously. The shift position detecting means is constituted by the swash plate position detecting means for detecting the operation position of the swash plate of the capacity pump,
The control means is configured such that a deceleration operation amount of the swash plate by the pump swash plate angle operating means when the operating state of the PTO work device is detected is determined when the non-operating state of the PTO work device is detected. 2. The output state of the control signal to the pump swash plate angle operation means based on the detection signal of the work state detection means is changed so as to be larger than the deceleration operation amount of the swash plate. Load control device for work vehicles.   In the control means, the deceleration operation speed by the speed change operation means when the operating state of the PTO work device is detected is larger than the deceleration operation speed when the non-operation state of the PTO work device is detected. The work vehicle load control apparatus according to claim 1 or 2, wherein the output state of the control signal to the shift operation means based on the detection signal of the work state detection means is changed.   The control means outputs the control signal to the shift operation means so that the deceleration operation speed by the shift operation means increases as the engine load detected based on the detection signals from the load detection means and the shift position detection means increases. 4. The load control device for a work vehicle according to claim 1, wherein the output state is changed.

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