JP2007092955A - Load control structure of working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conduct a load control suitable for the load operation over a wide range from the light load condition to the heavy load condition. <P>SOLUTION: A controlling means 31 is to control the operation of a pump operating means 26 so as to decelerate the swash plate 16A of a variable displacement pump 16 more with a greater engine load on the basis of the detection result of a load detection means 47 and the detection result of a swash plate position detection means 30 and also control the operation of a motor operating means 55 so as to change over the swash plate 17A of a variable capacity motor 17 from the high speed position into the low speed position in association with a rise of the engine load to the preset, first set value on the basis of the detection result of the load detection means 47 and to change over the swash plate 17A of the motor 17 from the low speed position into the high speed position in case the engine load has sunk to the preset, second set value or below. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to load detecting means for detecting engine load, swash plate position detecting means for detecting an operation position of a swash plate of a variable displacement pump provided in a hydrostatic continuously variable transmission, and a swash plate of the variable displacement pump. Pump operating means for continuously operating the motor, motor operating means for switching the swash plate of the variable displacement motor provided in the hydrostatic continuously variable transmission to high and low two stages, and operation of these operating means The present invention relates to a load control structure for a work vehicle including control means for controlling.

As the load control structure of the work vehicle as described above, the swash plate of the variable capacity motor is moved from the high speed position as the engine load increases to the first set value set in advance based on the detection of the load detecting means. Controls the operation of the motor operating means so that the swash plate of the variable displacement motor switches from the low speed position to the high speed position as the engine load decreases to the preset second set value. Based on the detection by the load detection means and the detection by the swash plate position detection means, the swash plate of the variable displacement pump is decelerated as the engine load increases. There is one configured to control the operation of the operating means for the pump.
JP-A-6-17928

  The former load control is suitable for light load work with a relatively small engine load, and the latter load control is suitable for heavy load work with a relatively large engine load. In each of the above-described configurations, since the load control is provided independently, it is not suitable for a wide range of load work ranging from light load work to heavy load work.

  An object of the present invention is to enable load control suitable for a wide range of load work from a light load state to a heavy load state.

  According to the first aspect of the present invention, the load detection means for detecting the engine load and the swash plate position detection for detecting the operation position of the swash plate of the variable displacement pump provided in the hydrostatic continuously variable transmission. A pump operating means for steplessly operating the swash plate of the variable displacement pump, and a motor operation for switching the swash plate of the variable displacement motor provided in the hydrostatic continuously variable transmission between high and low two stages. And control means for controlling the operation of these operating means, and the control means is configured to detect the variable capacity as the engine load increases based on detection by the load detection means and detection by the swash plate position detection means. The operation of the pump operating means is controlled so that the swash plate of the pump is decelerated, and the engine load increases to a preset first set value based on the detection of the load detecting means. , The swash plate of the variable capacity motor switches from the low speed position to the low speed position so that the swash plate of the variable capacity motor switches from the low speed position to the low speed position. The operation of the motor operating means is controlled so as to switch to the position.

  According to this configuration, in a light load work state with a small engine load, the swash plate of the variable displacement pump is decelerated as the engine load increases based on the detection of the load detection unit and the detection of the swash plate position detection unit. When the operation of the pump operating means is controlled and the engine load increases and reaches a heavy load state where the engine setting increases to a preset first set value, the swash plate of the variable capacity motor changes from the high speed position to the low speed position. The operation of the motor operation means is controlled so as to switch, and thereafter, the swash plate of the variable displacement pump is decelerated as the engine load increases based on the detection of the load detection means and the detection of the swash plate position detection means. Thus, the operation of the pump operating means is controlled.

  Then, when the engine load becomes small and a light load state where the engine load decreases to a preset second set value is reached, the operation means for the motor is operated so that the swash plate of the variable capacity motor is switched from the low speed position to the high speed position. After that, based on the detection of the load detection means and the detection of the swash plate position detection means, the operation of the pump operation means is controlled so that the swash plate of the variable displacement pump is decelerated as the engine load increases. To do.

  Therefore, load control suitable for a wide range of load work from a light load state to a heavy load state can be performed, and work efficiency and running performance can be improved.

  The invention according to claim 2 of the present invention is the invention according to claim 1, further comprising operation position detection means for detecting an operation position of the shift operation tool that is manually operated, wherein the control means includes Based on the detection of the operation position detection means, the first setting is such that the swash plate of the variable displacement motor is switched from the high speed position to the low speed position with a smaller engine load as the operation position of the speed change operation tool is lower. The value is configured to be changed to a value set in advance corresponding to the operation position of the speed change operation tool.

  By the way, for example, if the first set value is fixed to a large value, there is a possibility that an appropriate driving force cannot be obtained in a heavy load state where the engine load is less than the first set value.

  Therefore, the variable displacement motor swash plate is switched from the high speed position to the low speed position with a smaller engine load as the operation position of the speed change operation tool is on the low speed side, in other words, when the operation amount of the speed change operation tool is small. If an increase in the engine load is recognized to some extent, it can be assumed that the working state at this time is a heavy load state in which the engine load greatly increases when the operation amount of the speed change operation tool is increased. Since the swash plate of the variable capacity motor is switched from the high speed position to the low speed position from a relatively small stage, the driving force is ensured. Driving and work can be continued comfortably while preventing engine stall due to load.

  Therefore, it is possible to perform load control suitable for a wide range of load work from a light load state to a heavy load state, and it is possible to further improve work efficiency and traveling performance.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the control means performs the operation when the engine load decreases to a preset second set value or less. Based on the detection of the position detecting means, the operation position of the speed change operating tool is determined, and when the operation position of the speed change operation tool exceeds the preset value and is largely operated on the acceleration side, the variable capacity The operation of the motor operating means is controlled so that the swash plate of the motor is switched from the low speed position to the high speed position.

  In this configuration, the swash plate of the variable displacement motor is moved from the low speed position to the high speed position only when the driver expresses the intention to further accelerate in a light load state in which the engine load has decreased to a preset second set value or less. In this way, the swash plate of the variable capacity motor can be used in spite of the driver's operation to decelerate by operating the speed change operation tool as the load decreases. It is possible to prevent the occurrence of inconvenience that the speed is unexpectedly increased by switching from the low speed position to the high speed position.

  Therefore, it is possible to perform load control suitable for a wide range of load work from a light load state to a heavy load state, and it is possible to further improve work efficiency and traveling performance.

  FIG. 1 shows an entire side surface of a tractor that is an example of a work vehicle. This tractor is provided with front wheels 3 on the left and right sides of a front frame 2 that supports the vibration isolation of the engine 1 and is connected to the engine 1. A rear wheel 5 is provided on the left and right of the mission case 4 serving as a frame, and a riding operation unit 8 is formed by providing a steering wheel 6 and a driver seat 7 above the mission case 4.

  As shown in FIGS. 2 to 4, the 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 or the like, and the hydrostatic continuously variable transmission. A gear-type transmission 11 that functions as a sub-transmission configured such that the driving power taken out from the transmission 10 can be shifted to three stages of high, medium, and low, a front wheel differential 12 or a rear wheel differential. The working power transmitted to the left and right front wheels 3 and the left and right rear wheels 5 via the device 13 and the like and taken out from the hydrostatic continuously variable transmission 10 is powered via the hydraulic work clutch 14 and the like. It is transmitted to the take-out shaft 15.

  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.

  As shown in FIGS. 2 to 5, the hydrostatic continuously variable transmission 10 includes an axial plunger type variable displacement pump 16 and an axial plunger type variable displacement motor 17 incorporated in the second casing portion 4B. 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. The variable displacement pump 16 and the variable displacement motor 17 are connected to each other. Charge oil from a charge pump 21 driven by engine power is supplied to a closed circuit 20 formed by connecting an oil passage 18 and a second oil passage 19 via a charge oil passage 22 and a check valve 23. ing.

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

  As shown in FIGS. 4 to 6, the servo control mechanism 25 is a hydraulic pump cylinder (an example of pump operating means) 26 that operates the pump swash plate 16 </ b> A in a stepless manner, and the flow of hydraulic oil to the pump cylinder 26. A servo valve 27 for controlling the pressure, a regulator valve 28 for maintaining the hydraulic pressure for the servo valve 27 at a set pressure, a pedal sensor (an example of an operation position detecting means) 29 comprising a potentiometer for detecting the operation position of the shift pedal 24, a pump cylinder 26, a swash plate sensor (an example of a swash plate position detection means) 30 comprising a potentiometer that detects the operation position of the pump swash plate 16A from the operation amount of 26, detection of the pedal sensor 29, detection of the swash plate sensor 30, and the like are input. And a control device (an example of control means) 31 composed of a microcomputer. There.

  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 to return to the neutral position, and hydraulic oil is supplied to the oil chamber 34 for forward transmission. Thus, the pump swash plate 16A is operated in the forward acceleration direction against the bias of the forward deceleration spring 32, and hydraulic oil is supplied to the oil chamber 35 for reverse transmission, so that the reverse deceleration spring 33 The pump swash plate 16A is operated in the reverse speed increasing direction against the bias.

  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. The regulator valve 28 is composed of an electromagnetic reverse proportional valve 37 for controlling the flow of the engine, and the regulator valve 28 supplies hydraulic oil pumped from the power steering supply pump 38 to the work clutch 14 and the hydraulic power steering device. The 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. It is connected.

  As shown in FIG. 6, the control device 31 includes 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 16 </ b> A, the map data, and the pedal sensor. A pump swash plate control equipped with a control program for operating the pump swash plate 16A by controlling the operation of the forward proportional valve 36 or the reverse proportional valve 37 based on the detection of 29 and the detection of the swash plate sensor 30. Means 31A are provided.

  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 determines 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 based on the stored map data and the detection of the pedal sensor 29. The target operation position of the pump swash plate 16A is set, and based on the set target operation position and the detection of the swash plate sensor 30, the target operation position of the pump swash plate 16A matches the actual operation position. The operation of the forward proportional valve 36 or the reverse proportional 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 detection of the pedal sensor 29 and the detection of the swash plate sensor 30. The forward proportional valve 36 or the reverse proportional through the pressure port 28A of the regulator valve 28 is operated electronically by operating the pump cylinder 26 and operating the pump swash plate 16A of the hydrostatic continuously variable transmission 10. A direct acting type that directly drives the pump cylinder 26 with the output pressure of the valve 37 is used, so that pressure fluctuations in the closed circuit 20 of the hydrostatic continuously variable transmission 10 and fluctuations in engine speed can be detected. Compared to the case where the pump cylinder 26 is driven by the output pressure from the charge oil passage 22 in which the pressure fluctuates, the servo pilot is more stable. As a result, the operation of the pump cylinder 26 can be accurately controlled. As a result, the detection of the pedal sensor 29 and the detection of the swash plate sensor 30 while the servo control mechanism 25 is configured as an inexpensive direct acting type. Accordingly, the vehicle speed control for moving the vehicle body forward or backward at a speed corresponding to the operation position of the shift pedal 24 can be performed with high accuracy.

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

  Each map data of the first operation speed setting means 31B includes the actual operation position of the pump swash plate 16A detected by 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 operation speed of the pump swash plate 16A is increased with respect to the deviation of the pump swash plate 16A in the reverse travel, so that the operation speed of the pump swash plate 16A in the forward travel is The deviation of the pump swash plate 16A is made to correspond to the operation speed of the pump swash plate 16A so as to be slower than the operation speed of the pump swash plate 16A with respect to the deviation of 16A (see FIG. 8).

  The control program of the first operating speed setting means 31B determines the operating speed of the pump swash plate 16A corresponding to the calculated deviation of the pump swash plate 16A based on the stored map data and the calculation result of the arithmetic program. The target operation speed is set to 16A, and the set target operation speed is output to the pump swash plate control means 31A.

  The control program of the pump swash plate control means 31A is a forward proportional valve 36 or a reverse proportional so that the pump swash plate 16A is operated at the target operation speed set by the first operation speed setting means 31B in the vehicle speed control. The operation of the valve 37 is configured to be controlled. By this control operation, it is possible to suppress the occurrence of hunting while enhancing the response of the pump swash plate 16A to the operation of the shift pedal 24. As a result, the shift pedal is controlled. The vehicle speed can be reached quickly and accurately at a speed corresponding to the 24 operation positions. 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 hydrostatic continuously variable transmission 10 at the time of reverse travel is less likely to grasp the speed sensation than at the time of forward travel because the speed change operation is performed more slowly than the speed change operation of the hydrostatic continuously variable transmission 10 at the time of travel. This makes it easier to perform the shifting operation.

  The control device 31 is provided with data changing means 31C having a control program for changing map data used by the first operation speed setting means 31B. The data changing means 31C includes various data as shown below. The map data used by the first operation speed setting means 31B is appropriately changed according to the situation.

  Based on the operation position of the adjustment dial 42 composed of a potentiometer provided in the boarding operation unit 8, the data changing means 31C is configured so that the operation position of the adjustment dial 42 is largely changed from the reference position to the quick side. In order to perform the operation promptly, the map data to be used is determined by calculating 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 increases. The map data to be used is changed so that the operation of the pump swash plate 16A is performed more gently as the operation position of the adjustment dial 42 is greatly changed from the reference position to the smooth side. The deviation of the pump swash plate 16A and the pump swash plate so that the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A becomes slow. To change the 6A of the operation speed in the map data, which is made to correspond.

  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.

  Based on the detection of the oil temperature sensor 43 that detects the temperature of the hydraulic oil supplied to the regulator valve 28, the data changing means 31C causes the pump swash plate 16A to be operated more gently as the hydraulic oil temperature is lower. In addition, the map data to be used is 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 oil temperature decreases. Change to the corresponding map data.

  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 based on the detection of the sub-transmission sensor 45 including a potentiometer that detects the gear position of the gear-type transmission 11 from the operation position of the sub-transmission lever 44 provided in the boarding operation unit 8. The map data to be used is determined with respect to the deviation of the pump swash plate 16A in accordance with the increase in the gear stage of the gear type transmission 11 so that the operation of the pump swash plate 16A is performed more quickly as the speed of the gear is higher. The deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are changed to map data so as to increase the operation speed of the pump swash plate 16A.

  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. Accordingly, the operation feeling when the hydrostatic continuously variable transmission 10 is shifted with the shift pedal 24 can be made the same regardless of the shift stage of the gear transmission 11. .

  Based on the detection of the operation speed detection means 46 for detecting the operation speed of the shift pedal 24, the data changing means 31C is configured so that the operation of the pump swash plate 16A is performed more gradually as the operation speed of the shift pedal 24 is slower. The map data to be used is 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 becomes slower as the operation speed of the shift pedal 24 decreases. Change to map data corresponding to.

  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 is based on the detection of a rotation sensor (an example of a load detection means) 47 for detecting the engine speed and the target operation position of the pump swash plate 16A set by the pump swash plate control means 31A. If the target operation position of the pump swash plate 16A is set to the low speed side when the rotational speed decreases, the map data to be used is used to decrease the engine rotational speed so that the pump swash plate 16A is operated quickly. Accordingly, the map swash plate 16A is changed to map data corresponding to the deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A so as to increase the operation speed of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A. When it is detected that the target operation position of the pump swash plate 16A is set to the high speed side when the number increases, the operation of the pump swash plate 16A is performed gently. The map data to be used corresponds 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 engine speed increases. Change to the map data.

  As a result, if the speed change pedal 24 is operated to the deceleration side when the engine speed decreases due to an increase in traveling load or the like, the operation in the deceleration direction of the pump swash plate 16A based on the operation is quickly performed. The reduction of the load is promoted, and thus the engine load is reduced by the deceleration operation of the hydrostatic continuously variable transmission 10 linked to the operation of the speed change pedal 24 even though the speed reduction operation of the speed change pedal 24 is performed. It is possible to suppress the possibility of inconvenience that the engine 1 is stopped after a delay. Further, even if the speed change pedal 24 is operated to the speed increasing side when the engine speed increases due to a decrease in traveling load or the like, the operation in the speed increasing direction of the pump swash plate 16A based on the operation is gently performed. It is possible to avoid a sudden increase in the vehicle speed due to the speed increase operation of the pump swash plate 16A being performed promptly as the engine speed increases. That is, regardless of fluctuations in the engine speed, the shifting operation of the hydrostatic continuously variable transmission 10 by the shift pedal 24 can be performed satisfactorily.

  The data changing means 31 </ b> C performs the braking operation of the braking device based on the detection of the brake sensor 49 including a potentiometer that detects the operation of the braking device (not shown) from the operation position of the brake pedal 48 provided in the boarding operation unit 8. If so, the map data to be used is determined with respect to the deviation of the pump swash plate 16A in consideration of the decrease in the vehicle speed due to the braking operation of the braking device so that the operation of the pump swash plate 16A in the deceleration direction is performed quickly. The deviation of the pump swash plate 16A and the operation speed of the pump swash plate 16A are changed to map data so as to increase the operation speed of the pump swash plate 16A.

  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.

  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 data changing unit 31C determines that the target operation position of the pump swash plate 16A is the actual operation position. When the speed swash plate 16A is set to the higher speed side, the target operation position of the pump swash plate 16A is set to the speed reduction side than the actual operation position so that the operation of the pump swash plate 16A is performed gently. In this case, so that the pump swash plate 16A can be operated quickly, the pump swash plate 16A can be operated when the target operation position of the pump swash plate 16A and the actual operation position sandwich the neutral position. In order to make the map data to be used more quickly, the operation of the pump swash plate 16A with respect to the deviation of the pump swash plate 16A is determined according to the positional relationship between the target operation position of the pump swash plate 16A and the actual operation position. Degree to change differently the operating speed of the deviation of the pump swash plate 16A and the pump swash plate 16A to the map data is made to correspond.

  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 unit 31C operates the pump swash plate 16A at an increased speed from the neutral position 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 unit 31A. At the start of traveling, the map swash plate 16A is used 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 starting time so that the operation of the pump swash plate 16A is gently performed. The map data corresponding to the deviation of 16A and the operation speed of the pump swash plate 16A is changed, and the pump swash plate 16A is operated when the pump swash plate 16A is decelerated from the acceleration position to the neutral position. Therefore, the map data to be used can be set so that the operation speed of the pump swash plate 16A is increased with respect to the deviation of the pump swash plate 16A according to the stop time. Changing the operating speed of the deviation of the flop swash plate 16A and the pump swash plate 16A to the map data 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 the map data of the first operation speed setting means 31B, forward map data for setting the forward shift operation speed and reverse map data for setting the reverse shift operation speed are provided. In addition, the data changing means 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 is based on the detection of the set rotation 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 8, and the detection of the rotation sensor 47. A calculation program for calculating a reduction amount (hereinafter referred to as engine drop amount) of the engine speed from the set speed, and a plurality of map data (correlation) indicating the correlation between the engine speed and the operation position of the pump swash plate 16A. An example of relational data) and a control program for operating the pump swash plate 16A by controlling the operation of the forward proportional valve 36 or the reverse proportional valve 37 based on the calculation result of the calculation program and the map data. The equipped automatic pump swash plate control means 31D is provided.

  The map data of the automatic pump swash plate control means 31D is obtained from the engine 1 set from the maximum torque output characteristic of the engine 1 with respect to the operation position of the pump swash plate 16A set based on the relief pressure of the hydrostatic continuously variable transmission 10. Engine speed so that the limit operation position of the pump swash plate 16A becomes smaller as the engine drop amount is larger, and the limit operation position of the pump swash plate 16A is not set to the neutral position. The numbers correspond to the operation positions of the pump swash plate 16A (see FIG. 9).

  The control program of the automatic pump swash plate control means 31D determines the operation position of the pump swash plate 16A corresponding to the engine drop amount calculated by the calculation program based on the calculation result of the calculation program and the map data. Based on the set limit operation position and the detection of the swash plate sensor 30, the forward proportional valve 36 or the forward operation valve 36A or the actual operation position is matched with the limit operation position of the pump swash plate 16A. It is configured to control the operation of the reverse proportional valve 37, and by this control operation, at the time of loader work in which the front loader A is connected to the tractor, or at the time of tillage work in which the cultivator is connected to the tractor, Prevents the engine from being stalled due to an overload without the driver performing a gear shifting operation that takes into account the workload. Can be performed load control, with, it is possible to improve the operability and workability.

  In this load control, since the limit operation position of the pump swash plate 16A is not set to the neutral position, the load swash plate 16A is not returned to the neutral position by this load control. The occurrence of inconveniences such as the pump swash plate 16A being returned to the neutral position and the vehicle body being reversely fed back can be avoided.

  The control device 31 includes a plurality of map data indicating the correlation between the change speed of the engine speed and the operation speed of the pump swash plate 16A, and the change speed detecting means 53 for detecting the map data and the change speed of the engine speed. The second operation speed setting means 31E is provided which stores a control program for setting the target operation speed of the pump swash plate 16A based on the detection of.

  Each map data of the second operation speed setting means 31E includes the change speed of the engine speed and the operation speed of the pump swash plate 16A so that the operation speed of the pump swash plate 16A increases as the change speed of the engine speed increases. Is a correspondence.

  The control program of the second operating speed setting means 31E is a pump swash plate corresponding to the change speed of the engine speed detected by the change speed detection means 53 based on the stored map data and the detection of the change speed detection means 53. The operation speed of 16A is set to the target operation speed of the pump swash plate 16A, and the set target operation speed is output to the automatic pump swash plate control means 31D.

  The control program of the automatic pump swash plate control means 31D is used to set the forward proportional valve 36 or the reverse proportional valve 37 so that the pump swash plate 16A is operated at the target operation speed set by the second operation speed setting means 31E. It is configured to control the operation, thereby enabling better load control considering the change speed of the engine speed, and regardless of the fluctuation of the change speed of the engine speed, the engine speed The drop feeling when the engine speed decreases and the return feeling when the engine speed returns can be made constant, and the speed reduction operation of the pump swash plate 16A with respect to the decrease in engine speed can be performed with good responsiveness. It is possible to prevent engine stall due to operation delay of the pump swash plate 16A.

  The change speed detecting means 53 comprises a rotation sensor 47 and a calculation program provided in the second operation speed setting means 31E so as to calculate the change speed of the engine speed based on the detection of the rotation sensor 47. Has been.

  The data changing means 31C is provided with a control program for changing the map data used by the automatic pump swash plate control means 31D and the second operation speed setting means 31E. The data changing means 31C detects the set rotation sensor 52. Based on the above, map data used by the automatic pump swash plate control means 31D is set so that the amount of operation of the pump swash plate 16A with respect to the amount of change in the engine rotational speed increases as the set rotational speed of the engine 1 decreases. Map data corresponding to the operation position of the pump swash plate 16A (see FIG. 9), and based on the detection of the sub-transmission sensor 45, the gear stage of the gear-type transmission 11 is closer to the lower speed side. The map data used by the second operating speed setting means 31E is changed to the gear type transmission 11 so that the operation of the pump swash plate 16A is performed quickly. The map speed is changed to map data in which the change speed of the engine rotation speed 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 change speed of the engine rotation speed increases as the stage descends. It is configured.

  That is, load control suitable for the set rotational speed of the engine 1 can be performed based on the map data in consideration of the set rotational speed of the engine 1 selected according to the set rotational speed of the engine 1. Regardless of the number, the engine stall due to overload can be prevented well.

  Further, the pump swash plate 16A with respect to the change speed of the engine speed is increased as the speed is lower in accordance with the speed of the gear-type transmission 11 that is shifted to the lower speed as the work with a larger work load is performed. Map data set so as to increase the operation speed of the pump swash plate 16A is responsive to a sudden decrease in engine speed in a heavy work load. As a result, engine stall due to overload can be prevented more reliably.

  Incidentally, although not shown in the figure, a manual operation speed setting device including a potentiometer or a switch for setting the target operation speed of the pump swash plate 16A during load control is provided, and the target operation set by the operation speed setting device is provided. Types of working devices that are connected and configured so that automatic pump swash plate control means 31D controls the operation of forward proportional valve 36 or reverse proportional valve 37 so that pump swash plate 16A is operated at a speed. The target operation speed of the pump swash plate 16A may be set in consideration of different work loads.

  Further, an operation tool for data change instruction including a potentiometer or a switch for instructing change of map data used by the automatic pump swash plate control means 31D or the second operation speed setting means 31E is mounted on the data change means 31C. The map data may be changed according to the type of work device to be connected and installed in the unit 8.

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

  The switching mechanism 54 includes a hydraulic motor cylinder (an example of a motor operating means) 55 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 31F 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 31F performs elevation 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 31F 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 preset operation speed to the calculated deceleration target operation position, and the pump swash plate 16A is controlled. After reaching the deceleration target operating position, the return accelerating operation at the preset operating speed to the stored operating position of the pump swash plate 16A and the low speed from the high speed position of the motor swash plate 17A at the preset operating speed are performed. It is configured to control the operation of the forward proportional valve 36 or the reverse proportional valve 37 and the operation of the control valve 57 so that the switching operation to the position is performed simultaneously. With and [Figure 10 (b) refer to Fig.

  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. In addition, the operation of the forward proportional valve 36 or the reverse proportional valve 37 and the operation of the control valve 57 are controlled, and thereafter, the pump swash plate 16A is operated to return and increase at a preset operation speed to the stored operation position. In this way, the operation of the forward proportional valve 36 or the reverse proportional valve 37 is controlled (see (b) in FIG. 10).

  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. Change in the capacity of the variable capacity motor 17 caused by the switching operation of the motor can be offset by the capacity change in the variable capacity pump 16 caused by the speed increasing operation of the pump swash plate 16A. When the 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 switched from the low speed position to the high speed position. The displacement change in the variable displacement motor 17 generated in this manner can be offset by the displacement change in the variable displacement pump 16 that occurs in accordance with the deceleration operation of the pump swash plate 16A. Can, have, it is possible to alleviate shift shock generated by the switching operation of the motor swash plate 17A.

  Although not shown, when a high-speed response valve is used instead of the switching valve 56 and the motor swash plate control means 31F 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 31F is in a 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 31F 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 31F 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 31F 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.

  As shown in FIGS. 4 to 6, the control device 31 detects, based on detection of the pedal sensor 29, that the operation position of the shift pedal 24 has been operated to a preset operation position or operation area. Based on the maximum torque output characteristic of the engine 1 and the engine drop amount calculated by the calculation program of the automatic pump swash plate control means 31D, the engine speed corresponds to the operating position of the shift pedal 24 at that time in advance. The operation of switching the motor swash plate 17A from the high speed position to the low speed position when it is detected that the rotational speed has decreased to the high / low switching speed (first set value) or the high / low switching speed range near the set maximum torque output speed. In addition to performing automatic height switching control, the corresponding indicator lamp 61 is turned on, and the engine speed is set in advance based on the engine drop amount. Based on detection of the pedal sensor 29, when detecting that it has risen to a nearby low-high switching speed (second set value) or a low-high switching speed area, An automatic low / high switching control for switching the motor swash plate 17A from the low speed position to the high speed position as the operation of the shift pedal 24 is detected, and the corresponding indicator lamp 62 is turned on. Motor swash plate control means 31G is provided as a control program.

  Specifically, for example, when the operation position of the pedal 24 with the maximum depression position being 100% is an operation position of 50% or less, the engine speed with the set rotation speed as 100% is the rotation speed with 85%. When the operation position of the pedal 24 with the maximum depression position being 100% is an operation position of 90% or more as the value decreases to (first set value), the set rotation speed is set to 100%. As the engine speed decreases to 70% or less (first set value), automatic high / low switching control is performed, and the engine speed is 90% or more with the set speed as 100%. When the pedal 24 is depressed to an operating position of 80% or more with the maximum depressed position being 100%, the automatic low / high switching is performed. To do control It has been made.

  That is, when the amount of depression of the shift pedal 24 is large and the engine drop amount is large, naturally, when a certain amount of engine drop occurs when the amount of depression of the shift pedal 24 is small, It can be inferred that this is a heavy load state in which the engine drop amount increases as the depression amount of the speed change pedal 24 is increased. Therefore, even if the engine drop amount is small, high / low switching control is performed to ensure the driving force. Therefore, even if the driver does not perform a shift operation considering the work load or the like, it is possible to continue heavy load work requiring high driving force while preventing engine stall due to overload. . Also, when reducing the load when the engine speed has increased to around the preset set speed, if the driver wants to accelerate further, the vehicle speed will be increased by performing low-high switching control. In spite of the load reduction, the driver is trying to reduce the amount of depression of the shift pedal 24 to decelerate the vehicle. it can.

  In the high / low switching control of the automatic motor swash plate control means 31G, at the stage when the switching operation is performed, it is assumed that the vehicle speed is sufficiently lowered by the traveling load and the shift shock is small, so the motor swash plate control means 31F. The forward proportional valve is operated so that the motor swash plate 17A is switched from the high-speed position to the low-speed position at a preset operation speed without performing the control for reducing the shift shock such as the high-low switching control. 36 or the reverse proportional valve 37 is controlled to switch the motor swash plate 17A to the low speed position, and then the state is maintained for a predetermined time (for example, 2 seconds).

  Further, in the low / high switching control of the automatic motor swash plate control means 31G, the control operation similar to the low / high switching control in the motor swash plate control means 31F is performed, and the shift generated by the low / high switching operation of the motor swash plate 17A. After the shock is reduced and the motor swash plate 17A is switched to the high speed position, the state is maintained for a predetermined time (for example, 2 seconds).

  Incidentally, the automatic motor swash plate control means 31G has a preset maximum torque output speed based on the maximum torque output characteristic of the engine 1 and the engine drop amount calculated by the calculation program of the automatic pump swash plate control means 31D. Along with detecting that it has fallen to a nearby high / low switching speed or high / low switching speed area, automatic high / low switching control is performed to switch the motor swash plate 17A from a high speed position to a low speed position, and a corresponding indicator lamp. 61 is turned on, and based on the amount of engine drop, it is detected that the engine speed has increased to a low-high switching speed or a low-high switching speed area near a preset rotational speed. In addition to performing automatic low / high switching control for switching the motor swash plate 17A from the low speed position to the high speed position, the corresponding indicator lamp 62 is turned on. It may be configured to.

  The control device 31 is provided with a mode switching means 31H as a control program for switching a control mode to be executed based on an operation of a mode setting device 64 comprising a normally open switch provided on the display panel 63. This mode switching means 31H. Switches the shift control mode to be executed to the manual control mode, the semi-automatic control mode, and the automatic control mode each time an ON signal is input in accordance with the pressing operation of the mode setting device 64, and corresponds to each control mode. In the manual control mode, the vehicle speed control using the control operation of the pump swash plate control means 31A and the switching control using the control operation of the motor swash plate control means 31F are performed in the manual control mode. In the semi-automatic control mode, the vehicle speed control using the control operation of the pump swash plate control means 31A and the automatic pump swash plate control means 31 are performed. The load control using the control operation of the motor and the switching control using the control operation of the motor swash plate control means 31F are performed so that the load control has priority over the vehicle speed control. In the automatic control mode, the pump swash plate Vehicle speed control using the control operation of the control means 31A, load control using the control operation of the automatic pump swash plate control means 31D, and automatic switching control using the control operation of the automatic motor swash plate control means 31G The load control is prioritized over the control, and the load control and the automatic switching control are performed in a linked state so as to be appropriately linked.

  That is, when the manual control mode is selected, the pump swash plate 16A reaches the target operation position corresponding to the operation position of the shift pedal 24 at the target operation speed based on the operation position of the shift pedal 24 and the like. When the motor swash plate 17A is operated and is switched to the two positions of high and low based on the operation of the switching lever 59, and the semi-automatic control mode is selected, the pump swash plate 16A is On the basis of the operation position of 24, etc., the engine is operated so as to reach the target operation position corresponding to the operation position of the shift pedal 24 at the target operation speed. Based on this, the motor swash plate 17A is operated so as to reach the limit operation position corresponding to the engine drop amount at the target operation speed, and the switching lever 5 When the automatic control mode is selected, the pump swash plate 16A operates the speed change pedal 24 based on the operation position of the speed change pedal 24 or the like. While the engine is operated so as to reach the target operation position corresponding to the position at the target operation speed, if the engine drop occurs, the target operation position is set to the limit operation position corresponding to the engine drop amount based on the engine drop amount. The motor swash plate 17A is operated so as to reach the operation speed, and is switched to the high / low 2 position at an appropriate timing based on the operation position of the speed change pedal 24, the engine drop amount, and the like. For example, the manual control mode is selected during traveling or light load work, and during uphill or medium load work when the slope is relatively tight. Select semiautomatic control mode, if so during tight hill climbing or during heavy load work graded to select automatic control mode, while realizing reduction in burden on the driver, perform satisfactorily respective traveling and working

  Incidentally, in the load control in the automatic control mode, the control sensitivity is set to be insensitive to the engine drop easily because the lower limit rotational speed of the engine 1 is set lower than the load control in the semi-automatic control mode. Therefore, automatic switching control for switching the motor swash plate 17A to the low speed position is easily performed.

  When the automatic control mode is selected and the switching operation of the motor swash plate 17A to the low speed position based on the operation of the switching lever 59 is performed, the motor swash plate 17A is switched to the low speed position by the automatic switching control. Since the switching operation cannot be performed, the control mode is automatically switched from the automatic control mode to the semi-automatic control mode.

  As shown in FIG. 6, the operation panel 63 is equipped with a liquid crystal display 69 that can switch the display state to a vehicle speed display state, a residual fuel display state, or the like based on the operation of the display changeover switch 68. When the pump swash plate position display mode is selected by the operation of the display changeover switch 68, the display 69 displays the target operation position 69A or the limit operation position 69B and the current position 69C of the pump swash plate 16A that change every moment. Is configured to do.

  That is, by selecting the pump swash plate position display mode, it is possible to easily confirm the movement of the pump swash plate 16A, and to improve maintainability.

  Incidentally, (a) in FIG. 6 shows a state in which a target operation position 69A for speed increase with respect to the pump swash plate 16A is set, and (b) in FIG. 6 shows that the pump swash plate 16A is used for speed increase. FIG. 6 (c) shows a state where the target operation position 69A for deceleration of the pump swash plate 16A or the limit operation position 69B is set. It is shown.

  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 connected to a bolt, and is unitized into one block as an electronic operation mechanism 72. As shown in FIG. 12 and FIG. An operation shaft 73 that is operated and linked via a mechanical linkage mechanism (not shown), a servo valve 74 that includes a spool that controls the flow of hydraulic oil to the pump cylinder 26, and the like are provided in the second transmission case 4. Equipped with a casing 75 that is detachably bolted to the right side of the casing part 4B and unitized into one block. Was that replace the mechanical type operating mechanism 76, so that the easy specification changes the mechanical formulas electronic.

  4 and 12 is used as a feedback arm installed over the pump cylinder 26 and the swash plate sensor 30 in the electronic servo control mechanism 25, and is a mechanical servo control mechanism 78. Is a linkage arm that is used as an operation / feedback arm that spans the pump cylinder 26 and the operation shaft 73 so that the servo valve 74 can be operated.

  Reference numerals 78 and 79 shown in FIGS. 5 and 13 are formed on the joint surface of the second casing part 4B with the casing 71 when the electronic operating 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 be connected corresponding to each made communication port 80,81.

  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. Built in the casing 83 and unitized as one block as an operation mechanism 84, the operation mechanism 84 is replaced with a plate 85 as shown in FIGS. 12 and 14, and the operation mechanism of the second casing portion 4B is replaced. 84, the communication ports 86 to 91 formed on the joint surface are closed, the variable capacity motor 17 in the second casing portion 4B is replaced with the fixed capacity motor 92, and the motor cylinder 55 is removed. The specification can be changed relatively easily from the variable motor specification to the fixed motor specification.

  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.

  From the above configuration, the variable motor specification includes the electronic servo control mechanism 25 (see FIG. 5), and the variable motor specification includes the mechanical servo control mechanism 78 (see FIG. 13). The specification can be easily changed between the fixed motor specification with the electronic servo control mechanism 25 (see FIG. 14) and the fixed motor specification with the mechanical servo control mechanism 78 (see FIG. 15). In addition, it is possible to reduce costs and simplify parts management by sharing parts.

  As shown in FIG. 6, the regions on both ends of the operation region of the shift pedal 24 are set to the high speed region, and the space between them is set to the low speed region, and the motor swash plate control means 31F is based on the detection of the pedal sensor 29. When the shift pedal 24 is operated in the low speed region, the motor swash plate 17A is switched to the low speed position, and when the shift pedal 24 is operated in the high speed region, the motor swash plate 17A is positioned in the high speed position. As described above, the operation of the control valve 57 may be controlled so that the shift pedal 24 may be used also as an operation tool for switching between the two positions of the variable displacement motor 17. When the speed change pedal 24 is operated to the high speed area based on the detection of the pedal sensor 29, the motor swash plate 17A is set to the high speed area. To switch the speed position, and configured to control the actuation of the control valve 57, the shift pedal 24 may be also used as the operating tool of a low high switching of the variable displacement motor 17.

  As described above, when the shift pedal 24 is also used as an operation tool for switching the variable capacity motor 17, a detent mechanism (not shown) for grasping the boundary of the operation area of the shift pedal 24 may be provided. .

[Another embodiment]
[1] The working vehicle may be a riding rice transplanter, a riding mower or a wheel loader.
[2] As correlation data, a plurality of correlation expressions corresponding to various conditions may be provided, and coefficients corresponding to various conditions may be given to the correlation expressions.
[3] An electric cylinder, an electric motor, a hydraulic motor, or the like may be employed as the pump operation means 26 and the motor operation means 55.
[4] The shift operation tool 24 may be a shift lever or the like.
[5] Instead of the gear type transmission 11, a planetary gear type transmission may be adopted.

Overall side view of tractor Schematic showing the transmission structure of the tractor Vertical side view of the main part showing the transmission structure of the tractor Cross-sectional plan view of the main part showing the transmission structure of the tractor Hydraulic circuit diagram Block diagram showing the control structure The figure which shows the correlation with the operation position of a speed change pedal, and the operation position of a pump swash plate Diagram showing correlation between pump swash plate deviation and target operating speed A diagram showing the correlation between the operating position of the pump swash plate and the engine speed Diagram showing operation of pump swash plate during motor swash plate switching operation The figure which shows the display state of the pump swash plate position in the liquid crystal panel Cross-sectional plan view of the main part showing the structure of the mechanical servo control mechanism Hydraulic circuit diagram showing the state equipped with a mechanical servo control mechanism and switching mechanism Hydraulic circuit diagram showing a state equipped with only an electronic servo control mechanism Hydraulic circuit diagram showing a state equipped with only a mechanical servo control mechanism

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydrostatic continuously variable transmission 16 Variable displacement pump 16A Swash plate 17 Variable displacement motor 17A Swash plate 24 Shifting operation tool 26 Pump operation means 29 Operation position detection means 30 Swash plate position detection means 31 Control means 47 Load detection means 55 Motor operating means

Claims (3)

Load detecting means for detecting engine load, swash plate position detecting means for detecting the operation position of the swash plate of the variable displacement pump provided in the hydrostatic continuously variable transmission, and the swash plate of the variable displacement pump in a stepless manner Operating means for the pump to be operated, operating means for the motor for switching the swash plate of the variable capacity motor provided in the hydrostatic continuously variable transmission to high and low, and control means for controlling the operation of these operating means And
Based on the detection of the load detection means and the detection of the swash plate position detection means, the control means operates the pump operation means so that the swash plate of the variable displacement pump is decelerated as the engine load increases. And the swash plate of the variable capacity motor is switched from the high speed position to the low speed position as the engine load increases to the first set value set in advance based on the detection of the load detecting means. In addition, the operation of the motor operating means is controlled so that the swash plate of the variable displacement motor is switched from the low speed position to the high speed position when the engine load drops below a second preset value set in advance. A work vehicle load control structure configured as described above. Comprising an operation position detecting means for detecting an operation position of the manually operated speed change operation tool;
Based on the detection of the operation position detection means, the control means is configured such that the swash plate of the variable displacement motor is switched from the high speed position to the low speed position with a smaller engine load as the operation position of the speed change operation tool is lower. 2. The work vehicle load control structure according to claim 1, wherein the first set value is changed to a value set in advance in correspondence with an operation position of the shift operation tool.   When the engine load decreases to a preset second set value or less, the control means determines the operation position of the shift operation tool based on the detection of the operation position detection means, and operates the shift operation tool. Controls the operation of the motor operating means so that the swash plate of the variable capacity motor is switched from the low speed position to the high speed position when the position is greatly increased beyond the preset value. The load control structure for a work vehicle according to claim 1 or 2 configured as described above.

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