JP2010164109A - Driving control device for work vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving control device for a work vehicle capable of preventing application of a large load on an engine while avoiding insufficiency of driving force (torque) for running, and capable of carrying out that accurately. <P>SOLUTION: The driving control device is provided with a retaining means 56 for retaining movement to a low speed side of an operation part 7Ma for capacity change in a variable capacity type hydraulic motor 7M of a hydrostatic continuously variable transmission 7 for running by operation force of operating movement to a high speed side, an operation force adjusting means 58 for changing and adjusting the operation force of the retaining means 56, and a control means 79 for changing and adjusting a command value of commanding the operation force adjusting means so as to maintain the operation part 7Ma in a set target position. The control means 79 changes and adjusts the command value commanding the operation force adjusting means 58 in a state of not increasing the command value such that the operation part 7Ma exceeds a set upper limit, and if it is distinguished that it is in a standard driving condition, the set upper limit is corrected on the basis of a command value of when maintaining the operation part 7Ma in the set target position. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a traveling control device for a work vehicle including a hydrostatic continuously variable transmission for traveling to which engine power is transmitted.

As a conventional example of a traveling control device for a work vehicle equipped with a hydrostatic continuously variable transmission for traveling, a variable displacement hydraulic pump of the hydrostatic continuously variable transmission is configured to be shifted by a shift lever. And an electric motor for operating the speed change lever, a rotation speed detection sensor for detecting the rotation speed of the engine, and a control device for controlling the operation of the electric motor. When it is determined that the load has increased, there is one configured to operate the shift lever to the low speed side by an electric motor (see, for example, Patent Document 1).
Incidentally, in this patent document 1, an engine is mounted on a combiner as a work vehicle, and the power of the engine is transmitted to a reaping processing unit and a threshing device. It will change according to the increase / decrease of the load of a cutting process part and the load of a threshing apparatus.

JP-A-6-159487

The conventional traveling control device for a work vehicle reduces the engine load by reducing the traveling speed when the engine load increases, but has the following disadvantages.
In other words, operating the variable displacement hydraulic pump of the hydrostatic continuously variable transmission to the low speed side reduces the discharge amount of the hydraulic pump of the hydrostatic continuously variable transmission, so the traveling speed of the aircraft is low. At the same time, the driving force (torque) for traveling also decreases. As a result, when the hydraulic pump of the hydrostatic continuously variable transmission is operated to the low speed side in a soft work place with a large running resistance, it is considered that the driving force (torque) for running becomes insufficient.

  The present invention has been made in view of the above circumstances, and its object is to prevent a large load from being applied to the engine while avoiding a shortage of driving force (torque) for traveling. The object of the present invention is to provide a traveling control device for a work vehicle that can accurately perform this.

The present invention is a traveling control device for a work vehicle provided with a hydrostatic continuously variable transmission for traveling to which engine power is transmitted.
Holding means for holding the operation part for changing the capacity of the variable capacity hydraulic motor of the hydrostatic continuously variable transmission in the low speed side with an operating force for moving the high speed side;
An operating force adjusting means for changing and adjusting the operating force of the holding means in a form in which the operating force of the holding means is increased as the command value that changes in size is larger;
Position detecting means for detecting the position of the operation unit;
Control means for changing and adjusting a command value commanded to the operating force adjusting means so as to maintain the operating portion at a set target position based on detection information of the position detecting means;
The control means is
The command value to be commanded to the operating force adjusting means is changed and adjusted in such a manner that the command value is not increased beyond the set upper limit value even if the operation unit moves to a lower speed side than the set target position. And
When it is determined that the vehicle is in the reference running state, the set upper limit value is corrected based on the command value when the operation unit is maintained at the set target position.

In other words, the operation unit for changing the capacity of the variable displacement hydraulic motor in the hydrostatic continuously variable transmission device tries to move from the set target position to the low speed side due to the traveling load, but the holding means is set by the operation unit. The movement from the target position to the low speed side is held by the operating force for moving the high speed side.
Then, the control means changes and adjusts the command value commanded to the operating force adjusting means so as to maintain the operating part at the set target position based on the detection information of the position detecting means for detecting the position of the operating part. Thus, even if the traveling load increases or decreases, the operation unit is maintained at the set target position.
Further, the control means changes and adjusts the command value commanded to the operating force adjusting means in such a manner that the command value is not increased beyond the set upper limit value even if the operation unit moves to a lower speed side than the set target position. Since the processing load is increased, the operating part moves to the low speed side when the traveling load increases and the command value is increased to the set upper limit value. The rotational speed of the hydraulic motor is operated at a lower speed than the rotational speed when the operating unit is positioned at the set target position.

  Operating the rotational speed of the hydraulic motor of the hydrostatic continuously variable transmission to a lower speed than the rotational speed when the operating unit is positioned at the set target position is a variable capacity type in the hydrostatic continuously variable transmission. Since the capacity of the hydraulic motor is reduced, the hydraulic motor of the hydrostatic continuously variable transmission does not rotate much even if sufficient hydraulic oil is supplied to the hydraulic motor from the hydraulic pump of the hydrostatic continuously variable transmission. It will not be necessary. As a result, when the hydraulic motor of the hydrostatic continuously variable transmission is operated to the low speed side, if the discharge amount of the hydraulic pump of the hydrostatic continuously variable transmission is secured, the hydrostatic continuously variable transmission of Low-speed power having sufficient driving force (torque) for traveling is transmitted from the hydraulic motor to the lower transmission side.

  When the traveling load increases in this way, the hydraulic motor of the hydrostatic continuously variable transmission is operated to the low speed side, whereby low speed power with sufficient driving force (torque) for traveling is transmitted to the traveling apparatus. Therefore, even in a soft work place having a large running resistance, it is possible to prevent a large load from being applied to the engine while avoiding a shortage of driving force (torque) for running.

In addition, when the travel load increases, the control means sets the operation of the hydraulic motor of the hydrostatic continuously variable transmission to the low speed side, even if the control unit moves to the low speed side from the set target position. The command value commanded to the operating force adjusting means is changed and adjusted in such a way that the command value commanded to the operating force adjusting means is not increased beyond the upper limit value, so that a shortage of driving force (torque) for traveling is avoided. On the other hand, it is possible to accurately prevent the engine from being subjected to a large load.
That is, when the traveling load increases, as a configuration for operating the hydraulic motor of the hydrostatic continuously variable transmission to the low speed side, for example, based on the detection information of the torque detection means that detects the driving torque of the hydraulic motor, Although it is conceivable that the actuator for operating the operation unit to the low speed side is operated, a response delay occurs when the drive torque is detected to operate the actuator.
On the other hand, according to the first characteristic configuration, the control means does not increase the command value beyond the set upper limit value even when the operation unit moves to a lower speed side than the set target position. By changing and adjusting the command value commanded to the adjusting means, when the driving load increases, the rotational speed of the variable displacement hydraulic motor is set to the low speed side without performing a special operation. Without causing a response delay, when the traveling load increases, the hydraulic motor of the hydrostatic continuously variable transmission can be precisely operated to the low speed side.

  By the way, as the holding means, for example, a hydraulic cylinder that is changed by the hydraulic pressure to which the operating force is supplied may be used, and as the operating force adjusting means, the hydraulic pressure supplied to the hydraulic cylinder may be used. There is a case where an electromagnetic proportional valve for changing and adjusting is used. Such an electromagnetic proportional valve is supplied to the hydraulic cylinder by being changed and adjusted in a state where the current value supplied as the command value changes in magnitude. The hydraulic pressure is changed. The larger the current value supplied to the electromagnetic proportional valve, the greater the pressure of the hydraulic pressure supplied to the hydraulic cylinder, that is, the holding force.

  However, the operating force adjusting means configured to change and adjust the operating force of the holding means in a form in which the operating force of the holding means is increased as the command value changing in magnitude is larger as in an electromagnetic proportional valve. The characteristic indicating the correlation between the command value and the operating force of the holding means has variations due to individual differences (see, for example, a plurality of characteristic lines L1, L2, and L3 in FIG. 13). As described above, if the setting upper limit value is set to a predetermined value in spite of variations in the characteristic indicating the correlation between the command value and the operating force of the holding means, for example, the setting upper limit value is appropriate. May be larger than the value. Then, in a state where the traveling load increases and the command value is increased to the set upper limit value, there is a disadvantage that the traveling load becomes too large and the engine load becomes excessive, and the driving force (torque) for traveling There is a risk that it will not be possible to accurately prevent the engine from being overloaded while avoiding the shortage of the engine.

  Therefore, in the first characteristic configuration, when the control unit determines that the vehicle is in the reference running state, the control unit is configured to correct the set upper limit value based on a command value for maintaining the operation unit at the set target position. Therefore, the set upper limit value can be corrected to an appropriate value in correspondence with the individual difference in the characteristic indicating the correlation between the command value and the operation force of the holding means.

  In other words, the reference driving state is a driving state in which the driving load can be assumed in advance, and in such a reference driving state, the operation force adjusting means is instructed to maintain the operation unit at the set target position. The command values are different from each other by an amount corresponding to the variation in the command values of the characteristics due to the individual differences as described above of the operating force adjusting means. Therefore, for example, it is possible to correct the set upper limit value in a state in which the variation in characteristics is canceled using information on the difference between the command value and a command value that is preset in advance. Regardless of variations in characteristics, it is possible to correct the set upper limit value to an appropriate value, and to ensure that a large load is not applied to the engine while avoiding insufficient driving force (torque) for traveling. It is possible to do this.

  In place of the above-described configuration, a pressure detection unit that detects the operation pressure of the holding unit is provided, and based on the detection information of the pressure detection unit, the pressure detected corresponds to the set upper limit value. It is conceivable to change and adjust the command value to be commanded to the operating force adjusting means so as not to exceed, but in this case, an expensive pressure sensor is required and there is a disadvantage incurring high cost. Thus, there is no such disadvantage, and a simple configuration can be handled at low cost.

  Therefore, according to the first characteristic configuration of the present invention, it is possible to prevent a large load from being applied to the engine while avoiding a shortage of driving force (torque) for traveling, and to accurately do so. It is possible to provide a traveling control device for a work vehicle that can perform the above-described operation.

In addition to the first feature configuration, the second feature configuration of the present invention includes:
As the set target position, a plurality of set target positions that are different positions are determined,
Selection means for selecting any of the plurality of set target positions is provided,
The control means changes and adjusts a command value to be instructed to the operation force adjustment means so that the operation unit is maintained at the set target position selected by the selection means among the plurality of set target positions. It is in the point comprised as follows.

That is, the control means changes and adjusts the command value commanded to the operating force adjusting means so as to maintain the operating portion at the set target position selected by the selecting means among the plurality of set target positions.
Since the rotation speed of the hydraulic motor can be changed to high or low by maintaining the operation unit at a plurality of different set target positions, the running speed can be changed depending on running conditions such as the hardness of the ground. In addition, if a set target position on the low speed side is selected, a large driving force (torque) for traveling can be obtained.

  Therefore, according to the 2nd characteristic composition, in addition to the operation effect by the 1st characteristic composition, the traveling control device of the work vehicle which can choose the traveling speed according to the traveling conditions such as the hardness of the ground can be provided.

  According to a third feature configuration of the present invention, in addition to the second feature configuration, the set upper limit value is determined such that the lower set target position is lower than the set target position. There is in point.

  That is, since the setting upper limit value for each of a plurality of setting target positions is set to be lower as the setting target position on the low speed side is set, the setting on the high speed side is set even when the setting target position on the low speed side is set. Even when the target position is set, it is possible to accurately operate the rotation speed of the hydraulic motor to the low speed side as the driving load increases, and to ensure that a large load is not applied to the engine. It will be something that can be done.

  That is, when setting the low-speed set target position among the plurality of set target positions is when the driving force (torque) for traveling is required due to the softness of the ground, the hydraulic pressure Even if the motor is rotated at a low speed, a state where a large load is applied to the engine is likely to occur, but the upper limit value set for each of the plurality of set target positions is set to be lower for the set target position on the lower speed side. Therefore, it is possible to avoid as much as possible that a large load is applied to the engine for driving the hydraulic motor.

  Therefore, according to the third characteristic configuration, in addition to the operational effects of the second characteristic configuration, when the driving force (torque) for traveling is required due to the softness of the ground, the hydraulic motor It is possible to provide a traveling control device for a work vehicle that can avoid as much as possible a large load on the engine for driving.

In addition to any of the first to third feature configurations, the fourth feature configuration of the present invention includes:
The holding means is a hydraulic cylinder that is changed by a hydraulic pressure to which an operating force is supplied;
An electromagnetic proportional valve that changes and adjusts the pressure of the hydraulic pressure supplied to the hydraulic cylinder in a form in which the operating force adjusting means increases the operating force of the holding means as the energized current value as the command value increases. And
The control means is configured to change and adjust a current value for energizing the electromagnetic proportional valve in a form that does not increase beyond a set upper limit current value corresponding to the set upper limit value.

  That is, a hydraulic cylinder is used as the holding means, an electromagnetic proportional valve is used as the operating force adjusting means, and the current value that the control means supplies to the electromagnetic proportional valve corresponding to the operating force of the holding means corresponds to the set upper limit value. By controlling the current value that is applied to the solenoid proportional valve in a form that does not increase beyond the set upper limit current value, the operating unit is maintained at the set target position and the solenoid proportional valve is energized even when the traveling load increases or decreases. In the state where the current value to be increased to the set upper limit current value, when the running load further increases, the rotational speed of the variable displacement hydraulic motor is set to be higher than the rotational speed when the operation unit is positioned at the set target position. It will be possible to operate on the low speed side.

  Therefore, according to the fourth characteristic configuration, a simple configuration using a hydraulic cylinder and an electromagnetic proportional valve is used to prevent the engine from being subjected to a large load while avoiding a shortage of driving force (torque) for traveling. It is possible to provide a traveling control device for a work vehicle that can perform the above-described operation.

In addition to any of the first to fourth feature configurations described above, the fifth feature configuration of the present invention includes:
The engine is mounted on a combine as a work vehicle, and the power of the engine is transmitted to a cutting and processing unit and a threshing device,
Work state detecting means for detecting whether the state is a cutting work state or a non-cutting work state is provided,
The control means is
When the cutting state is detected by the working state detection means, it is configured to determine that it is the reference running state, and
If it is determined that the vehicle is in the reference running state, a set time before the switching timing for switching from the state in which the cutting state is detected by the working state detection unit to the state in which the non-cutting state is detected By the time until the switching timing, the setting upper limit value is corrected based on the command value when the operation unit is maintained at the set target position.

  That is, the control means is between the set time and the switching timing before the switching timing for switching from the state where the cutting state is detected by the working state detecting means to the state where the non-cutting state is detected. The set upper limit value is corrected based on the command value for maintaining the operation unit at the set target position. In other words, when performing the cutting work in one work process, the set upper limit value is corrected in a state immediately before the end of the cutting, but the state immediately before the end of the cutting in this way is In order to perform the cutting operation, the vehicle is traveling straight, and the vehicle speed is stable, and it can be assumed that the driving load is a standard driving load during the cutting operation. Can be corrected.

  Moreover, since it is possible to prevent a large load from being applied to the engine while avoiding a shortage of driving force (torque) for traveling, fluctuations in the rotational speed of the engine can be suppressed. The fluctuation of the driving speed is suppressed, and the cutting process and the threshing process can be performed satisfactorily.

  Therefore, according to the fifth feature configuration, in addition to the operational effects of any of the first to fourth feature configurations, the set upper limit value can be corrected appropriately, and the harvesting process work and the threshing process in the combine can be performed. It is possible to provide a travel control device for a work vehicle that can perform work satisfactorily.

According to a sixth feature configuration of the present invention, in addition to any one of the first feature configuration to the fourth feature configuration, the engine is mounted on a combiner as a work vehicle, and the power of the engine includes a cutting processing unit, Is transmitted to the threshing device,
A work state detection means for detecting whether the state is a cutting work state or a non-reaping work state, a vehicle speed detection means for detecting a vehicle speed, and a steering state detection means for detecting whether the vehicle is traveling straight or turning. Is provided,
The control means is
The cutting state is detected by the working state detecting means, the vehicle speed detected by the vehicle speed detecting means is equal to or higher than a set vehicle speed, and the straight traveling state is detected by the steering state detecting means. Is configured to determine that the vehicle is in the reference running state when each condition is satisfied, and
When it is determined that the vehicle is in the reference running state, the command value for maintaining the operation unit at the set target position is averaged while the state of determining that the vehicle is in the reference running state continues. Based on the above, the set upper limit value is corrected.

  That is, the control means determines that it is in the reference running state when the cutting operation is performed while traveling straight at a vehicle speed equal to or higher than the set vehicle speed, and the state in which it is determined that the reference running state continues. Since the setting upper limit value is corrected based on the value obtained by averaging the command value when maintaining the operation unit at the set target position, even when the running load may fluctuate when running on the field, By using a value obtained by averaging the command values, an appropriate setting upper limit value is set based on a command value corresponding to a traveling load in a stable traveling state or a traveling load close thereto while performing a standard cutting operation state. It can be corrected.

  Therefore, according to the sixth feature configuration, in addition to the operational effects of any of the first to fourth feature configurations, the set upper limit value can be corrected appropriately, and the harvesting processing work and the threshing process in the combine can be performed. It is possible to provide a travel control device for a work vehicle that can perform work satisfactorily.

It is a whole side view of a combine. It is a longitudinal front view of a mission case. It is a hydraulic circuit diagram of a hydraulic unit. It is a block diagram which shows a control structure. 1 is a hydraulic circuit diagram of a hydrostatic continuously variable transmission. It is a figure which shows a traveling state, a standard cutting state, and a low-speed cutting state. It is a flowchart which shows a control action. It is a flowchart which shows a control action. It is a flowchart which shows a control action. It is a flowchart which shows a control action. It is a flowchart which shows a control action. It is a flowchart which shows a control action. It is a figure which shows the relationship between an electric current value and operating force.

Embodiment
As shown in FIG. 1, a cutting unit 2 as a cutting processing unit is supported by a front part of a machine body supported by right and left crawler type traveling devices 1 so as to be movable up and down, and is operated on the right side of the front part of the machine body. The unit 3 is provided, the threshing device 4 is provided on the left side of the rear part of the machine body, the grain tank 5 is provided on the right side of the rear part of the machine body, and a self-detaching combine which is an example of a work vehicle is configured. .

  As shown in FIG. 2, an engine 6 is provided on the lower side of the driving unit 3, a mission case 8 is provided in the vicinity of the center of the left and right of the front part of the airframe, and the hydrostatic continuously variable transmission 7 is connected to the mission case 8. A belt transmission mechanism 9 having a tension clutch function is connected across the input shaft 7a of the hydrostatic continuously variable transmission 7 and the output shaft 6a of the engine 6 connected to the upper portion of the right side.

  The cutting unit 2 is provided with a stock sensor 90 as a cutting work state detection means. The stock sensor 90 detects the on-state (reaching operation state) when the harvested cereal is being conveyed, and the off-state (non-reaching operation state) when the cereal cereal is not present. Is configured to detect.

  As shown in FIG. 2, the output shaft 7b of the hydrostatic continuously variable transmission 7 is inserted into a mission case 8 and connected to a low-speed gear 10 by a spline structure, and the transmission in which the low-speed gear 10 is fixed. A high speed gear 11 is fixed to the shaft 12. A low-speed gear 14 and a high-speed gear 15 are fitted on the output shaft 13 so as to be relatively rotatable, and the low-speed gears 10 and 14 and the high-speed gears 11 and 15 are engaged. The shift member 16 slides on the output shaft 13 by a spline structure. And it is externally fitted so that it can rotate integrally. A tension clutch type cutting clutch 17 is provided by a transmission belt across the output shaft 13 and the input shaft 2a of the cutting unit 2. The power of the output shaft 6a of the engine 6 is configured to be transmitted to the threshing device 4 via a tension clutch type threshing clutch 4A (see FIG. 4).

  As shown in FIG. 2, when the shift member 16 is engaged with the low speed gear 14 (low speed position), the power of the output shaft 7 b of the hydrostatic continuously variable transmission 7 is transmitted via the low speed gears 10, 14 and the shift member 16. When the shift member 16 is engaged with the high-speed gear 15 (high-speed position) when transmitted to the cutting unit 2 in a low-speed state, the power of the output shaft 7b of the hydrostatic continuously variable transmission 7 is transmitted to the high-speed gears 11 and 15 and the shift member 16. Is transmitted to the cutting unit 2 in a high speed state. As described above, the low-speed gears 10 and 14, the high-speed gears 11 and 15, the shift member 16, and the like constitute the cutting transmission 18 that can be shifted in two steps.

Next, the structure of the transmission system (transverse system) of the mission case 8 will be described.
As shown in FIG. 2, a transmission gear 19 is externally fitted to the transmission shaft 20 so as to be relatively rotatable, the transmission gear 19 is engaged with the low-speed gear 10, and a shift member 21 is slid onto the transmission shaft 20 by a spline structure. It is externally fitted so that it can rotate integrally. Transmission gears 22 and 23 are fixed to the transmission shaft 20, and a multi-plate friction parking brake 24 is provided at the end of the transmission shaft 20.

  As shown in FIG. 2, the shift member 21 is normally engaged with the transmission gear 19, and the power of the output shaft 7 b of the hydrostatic continuously variable transmission 7 is transmitted via the low-speed gear 10 and the transmission gear 19. It is transmitted to the shaft 20. At the time of towing the aircraft due to a failure or the like, the right and left traveling devices 1 and the hydrostatic continuously variable transmission 7 can be shut off at the position of the shift member 21 by separating the shift member 21 from the transmission gear 19. Therefore, the airframe can be pulled without receiving the resistance of the hydrostatic continuously variable transmission 7.

  As shown in FIG. 2, the transmission gear 25 is fixed to the transmission shaft 26, and the transmission gears 22 and 25 are engaged. The right and left output gears 27 are fitted on the transmission shaft 26 so as to be relatively rotatable. The right and left output gears 27 are slid onto the transmission shaft 26 by a spline structure. It is externally fitted so that it can rotate integrally. Right and left axles 29 are provided, right and left transmission gears 30 fixed to the right and left axles 29 mesh with the right and left output gears 27, and the ends of the right and left axles 29 The sprocket 1a (refer FIG. 1) of the right and left traveling apparatuses 1 is connected to the part.

  As shown in FIG. 2, a spring 32 is provided between the receiving member 31 fixed to the transmission shaft 26 and the right occlusion portion 28, and a spring 32 is provided between the transmission gear 25 and the left occlusion portion 28. Thus, the right and left occlusion portions 28 are biased by the springs 32 to the occlusion side of the right and left output gears 27. A right oil chamber is formed between the right output gear 27 and the right occlusion portion 28, and a left oil chamber is formed between the left output gear 27 and the left occlusion portion 28. By supplying hydraulic oil to the left oil chamber, the right and left occlusion portions 28 can be separated from the right and left output gears 27 against the spring 32.

  As shown in FIG. 2, an occlusion-type right side clutch 33 is configured between the right output gear 27 and the right occlusion portion 28, and the occlusion is established between the left output gear 27 and the left occlusion portion 28. A left side clutch 33 of the equation is configured. When the right (left) occlusal portion 28 meshes with the right (left) output gear 27, the right (left) side clutch 33 is in a transmission state, and the right (left) occlusal portion 28 becomes right (left). By separating from the output gear 27, the right (left) side clutch 33 is disconnected.

  2, the power of the output shaft 7b of the hydrostatic continuously variable transmission 7 is such that the low speed gear 10, the transmission gear 19, the transmission shaft 20, the transmission gears 22, 25, the transmission shaft 26, The aircraft is transmitted straight to the right and left traveling devices 1 via the left occlusal portion 28, right and left output gears 27, right and left transmission gears 30, and right and left axles 29.

Next, the structure of the transmission system (turning system) of the mission case 8 will be described.
As shown in FIG. 2, a transmission gear 35 externally fitted to the transmission shaft 34 is engaged with a gear portion on the outer peripheral portion of the right occlusion portion 28, and the transmission shaft 34 and the transmission gear 35 are connected to each other. A slow swing clutch 36 is provided therebetween. The slow swing clutch 36 is configured as a frictional multi-plate type and is energized in a shut-off state, and is operated in a transmission state when hydraulic oil is supplied, and is operated in a shut-off state when the hydraulic oil is discharged.

  As shown in FIG. 2, a swing clutch case 37 is fitted on the transmission shaft 26 so as to be relatively rotatable, and a transmission gear 38 fixed to the transmission shaft 34 and a gear portion on the outer periphery of the swing clutch case 37 are engaged with each other. is doing. The swing clutch case 37 is configured symmetrically, and a right swing clutch 39 is provided between the swing clutch case 37 and the right output gear 27, and between the swing clutch case 37 and the left output gear 27. A left turning clutch 39 is provided. The right and left turning clutches 39 are configured as a friction multi-plate type, and are operated in a transmission state by supplying hydraulic oil. In this case, in the right and left turning clutch 39, the friction plates are arranged so as to be close to each other, and the right and left turning clutch 39 are in a semi-transmission state even when the hydraulic oil is discharged. ing.

  As a result, as shown in FIG. 2, when the slow swing clutch 36 is operated in the transmission state, the power of the transmission shaft 26 causes the right occlusal portion 28, the transmission gear 35, the slow swing clutch 36, the transmission shaft 34, and the transmission gear. The power is transmitted to the turning clutch case 37 as power that is lower in speed than the transmission shaft 26 in the same direction as the transmission shaft 26. When the right or left side clutch 33 is operated in the disconnected state and the right or left side clutch 39 is operated in the transmission state in the transmission state of the slow rotation clutch 36, the transmission shaft 26 is moved in the same direction as the transmission shaft 26. Also, low speed power is transmitted to the right or left output gear 27.

As shown in FIG. 2, a brake 40 is provided on the left side of the transmission shaft 34. The brake 40 is configured as a friction multi-plate type, and is operated in a braking state by supplying hydraulic oil, and is operated in a released state by discharging the hydraulic oil.
As a result, as shown in FIG. 2, when the brake 40 is operated in the braking state, the turning clutch case 37 is in the braking state via the transmission shaft 34 and the transmission gear 38. In the braking state of the brake 40, when the right or left side clutch 33 is operated in the disconnected state and the right or left turning clutch 39 is operated in the transmission state, the right or left output gear 27 is in the braking state.

  As shown in FIG. 2, a transmission gear 41 is externally fitted to the transmission shaft 34 so as to be relatively rotatable, and the transmission gears 23 and 41 are engaged with each other, and the reverse clutch 42 is interposed between the transmission shaft 34 and the transmission gear 41. Is provided. The reverse clutch 42 is configured as a frictional multi-plate type and is energized in a shut-off state, and is operated in a transmission state when hydraulic oil is supplied, and is operated in a shut-off state when the hydraulic oil is discharged.

  As a result, as shown in FIG. 2, when the reverse clutch 42 is operated in the transmission state, the power of the transmission shaft 20 is transmitted via the transmission gears 23 and 41, the reverse clutch 42, the transmission shaft 34 and the transmission gear 38. It is transmitted to the turning clutch case 37 as power in the direction opposite to that of the shaft 26. In the transmission state of the reverse clutch 42, when the right or left side clutch 33 is operated in the disconnected state and the right or left turning clutch 39 is operated in the transmission state, the power in the direction opposite to that of the transmission shaft 26 is right or left. To the output gear 27.

Next, a hydraulic unit 59 that supplies and discharges hydraulic oil to and from the right and left side clutches 33 (the right and left occlusal portions 28), the right and left turning clutch 39, the slow turning clutch 36, the brake 40, and the reverse rotation clutch 42. Will be described.
As shown in FIGS. 2 and 3, the hydraulic unit 59 is connected to the lower part of the left side portion of the mission case 8. The hydraulic pump 60 is connected to the input shaft 7 a of the hydrostatic continuously variable transmission 7, and the hydraulic pump 60 is driven by the input shaft 7 a of the hydrostatic continuously variable transmission 7. An oil passage 61 extending from the oil pressure unit 59 is connected to the hydraulic unit 59.

  As shown in FIG. 3, a supply oil passage 62 is connected across the transmission case 8 and the hydraulic pump 60, and an oil cooler 63 is provided in the supply oil passage 62. A filter 64 is provided in a portion between the oil cooler 63. Lubricating oil stored in the transmission case 8 passes through the oil cooler 63 and the filter 64 as hydraulic oil and is supplied to the hydraulic pump 60. The hydraulic oil of the hydraulic pump 60 is supplied to the hydraulic unit 59 via the oil passage 61, and the hydraulic oil discharged from each part of the hydraulic unit 59 is returned to the transmission case 8 as will be described later.

  As shown in FIG. 3, inside the hydraulic unit 59, there are a right turn control valve 67, a left turn control valve 68, a first relief valve 69, an unload valve 70, a second relief valve 76, a proportional control valve 71, and a turn switching. A control valve 72 and pilot operation valves 73 and 74 are provided. An oil passage 61 of the hydraulic pump 60 is connected to the hydraulic unit 59, and right and left turning control valves 67 and 68, a first relief valve 69, and an unload valve 70 are connected in parallel to the oil passage 66 connected to the oil passage 61. It is connected.

  As shown in FIG. 3, the right turn control valve 67 is connected to the right side clutch 33 (right occlusion portion 28) and the right turn clutch 39, and the left turn control valve 68 is connected to the left side clutch 33 ( It is connected to the left occlusal portion 28) and the left turning clutch 39. The right and left turning control valves 67 and 68 are configured in an electromagnetic operation type that can be operated to supply positions 67a and 68a and discharge positions 67b and 68b, and are urged to the discharge positions 67b and 68b. The unload valve 70 is configured as an electromagnetic operation type that can be freely operated at the shut-off position 70a and the discharge position 70b, and is urged to the shut-off position 70a.

  As shown in FIG. 3, the second relief valve 76 is connected to the oil passage 75 branched from the right and left side clutches 33 (the right and left occlusal portions 28), and the proportional control valve 71 and the swing are connected to the oil passage 75. The switching control valve 72 is connected in series, and the turning switching control valve 72 is connected to the slow turning clutch 36, the brake 40 and the reverse rotation clutch 42. The proportional control valve 71 is configured as an electromagnetic operation type, and can control the pressure of hydraulic oil. The turning switching control valve 72 is configured in a pilot operation type that can be operated to a slow turning position 72a, a trust turning position 72b, and a super turning position 72c, and is biased to the slow turning position 72a. In this case, the relief pressure of the first relief valve 69 is set to a relatively high value, and the relief pressure of the second relief valve 76 is set to a relatively low value.

As shown in FIG. 3, the pilot operation valve 73 is configured so that the pilot hydraulic oil branched from the oil passage 75 is supplied to the turning switching control valve 72 and operated to the pivot turning position 72 b. The pilot operation valve 74 is configured to supply the pilot hydraulic oil thus supplied to the turning switching control valve 72 and to operate it to the super turning position 72c. A drain oil passage (not shown) is formed on the connection surface (mating surface) between the hydraulic unit 59 and the transmission case 8, and includes a right turn control valve 67, a left turn control valve 68, a first relief valve 69, The hydraulic oil of the unload valve 70, the second relief valve 76, the proportional control valve 71, the turning switching control valve 72, and the pilot operation valves 73 and 74 is returned to the mission case 8 through the drain oil passage.
As shown in FIG. 4, the right and left turning control valves 67 and 68, the unload valve 70, the proportional control valve 71, and the pilot operation valves 73 and 74 are operated as described later by a control device 79 as a control means. .

Next, a straight traveling state by the steering lever 77 will be described.
As shown in FIGS. 1 and 4, a steering lever 77 that can be operated to the right and left is provided in the operation unit 3, and detection information of an operation position detection sensor Q that detects an operation position of the steering lever 77 is indicated by the control device. 79, and the steering lever 77 is configured to be operated at a straight advance position n, right and left first turning positions R1, L1, and right and left second turning positions R2, L2. A dial operation type turning mode switch 78 is provided in the operation unit 3, and operation information of the turning mode switch 78 is inputted to the control device 79, and the turning mode switch 78 is set to a slow turning position, a trust turning position, and a super trust. It has a swivel position.

  As shown in FIGS. 2, 3, and 4, regardless of the operation position of the turning mode switch 78, when the steering lever 77 is operated to the rectilinear position n, the right and left turning control valves 67, 68 are moved to the discharge positions 67b, The unload valve 70 is operated to the discharge position 70b. As a result, the hydraulic oil is discharged from the right and left side clutch 33 (right and left occlusion portion 28) and the right and left turning clutch 39, and the right and left side clutch 33 (right and left occlusion portion 28). Is operated in the transmission state, and the right and left turning clutch 39 are operated in the half transmission state. The proportional control valve 71 operates the slow turn and reverse clutches 36 and 42 to the disconnected state, and the brake 40 to the released state.

  As shown in FIG. 2, the power of the output shaft 7b of the hydrostatic continuously variable transmission 7 is such that the low speed gear 10, the transmission gear 19, the transmission shaft 20, the transmission gears 22, 25, the transmission shaft 26, the right and left occlusions. It is transmitted to the right and left traveling devices 1 through the part 28, the right and left output gears 27, the right and left transmission gears 30, and the right and left axles 29, and the aircraft advances straight.

Next, the slow turning state by the steering lever 77 will be described.
As shown in FIGS. 2 to 4, when the turning mode switch 78 is operated to the slow turning position, the turning switch control valve 72 is operated to the slow turning position 72 a by the pilot operation valves 73 and 74.
Accordingly, when the steering lever 77 is operated to the right first turning position R1, the right turning control valve 67 is operated to the supply position 67a, the unload valve 70 is operated to the cutoff position 70a, and the right side The hydraulic oil is supplied to the clutch 33 (right occlusion portion 28) and the right turning clutch 39, the right side clutch 33 (right occlusion portion 28) is operated to be disconnected, and the right turning clutch 39 is in a transmission state. To be operated.

  As shown in FIG. 2, since the left swing clutch 39 is in a semi-transmission state, the power of the left side clutch 33 (the left occlusion portion 28) is transferred from the left output gear 27 and the left swing clutch 39 to the right. Is transmitted to the right output gear 27 through the turning clutch 39, and the power slightly lower than the transmission shaft 26 in the same direction as the transmission shaft 26 is transmitted to the right output gear 27. As a result, the aircraft gently turns to the right.

  As shown in FIGS. 2, 3, and 4, when the steering lever 77 is operated to the first right turning position R1, the right turning control valve 67 is operated to the supply position 67a as described above, and the unload valve 70 is moved. Simultaneously with the operation to the shut-off position 70a, hydraulic oil begins to be supplied to the slow swing clutch 36 via the proportional control valve 71 and the swing switching control valve 72 (slow swing position 72a), and the steering lever 77 is The proportional control valve 71 increases the operating pressure of the slow turning clutch 36 as the right first turning position R1 is operated to the right second turning position R2.

  As shown in FIGS. 2, 3, and 4, as the operating pressure of the slow swing clutch 36 is increased by the proportional control valve 71 based on the operation position of the steering lever 77, the power of the transmission shaft 26 is changed to the right. And the transmission shaft 26 in the same direction as the transmission shaft 26 via the occlusal portion 28, the transmission gear 35, the slow turning clutch 36, the transmission shaft 34, the transmission gear 38, the turning clutch case 37 and the right turning clutch 39. It is transmitted to the right output gear 27 as power.

  In this case, as shown in FIG. 2, the power from the left side clutch 33 (the left occlusal portion 28) and the power from the slow turning clutch 36 are simultaneously transmitted to the right output gear 27. In the range where the operating pressure of the slow swing clutch 36 is low, the power from the left side clutch 33 (left occlusion portion 28) overcomes the power from the slow swing clutch 36, and the left side clutch 33 (left occlusion) The right output gear 27 is driven by the power from the section 28). As a result, the airframe gradually turns to the right when the operating pressure of the slow swing clutch 36 is low.

  Next, when the operating position of the steering lever 77 approaches the right second turning position R2 and the operating pressure of the slow turning clutch 36 becomes high, the power from the slow turning clutch 36 is changed to the left side as shown in FIG. Overcoming the power from the clutch 33 (the left occlusal portion 28), the right output gear 27 is driven by the power from the slow turning clutch 36. In this state, the right output gear 27 is driven by the power from the slow turning clutch 36, rather than the right output gear 27 being driven by the power from the left side clutch 33 (the left occlusal portion 28). However, the right output gear 27 is driven at a low speed, and the aircraft turns slowly to the right.

  As shown in FIGS. 2 to 4, when the steering lever 77 is operated to the left first turning position L1, the left turning control valve 68 is operated to the supply position 68a, and the unload valve 70 is operated to the cutoff position 70a. Then, hydraulic oil is supplied to the left side clutch 33 (the left occlusion portion 28) and the left turning clutch 39, and the left side clutch 33 (the left occlusion portion 28) is operated in a disconnected state to turn left. The clutch 39 is operated to the transmission state. At the same time, the same operation as described above is performed, and the aircraft gradually turns to the left. When the steering lever 77 is operated from the left first turning position L1 to the left second turning position L2, the same operation as described above is performed, and the aircraft turns slowly to the left.

Next, the belief turning state by the steering lever 77 will be described.
As shown in FIGS. 2 to 4, when the turning mode switch 78 is operated to the belief turning position, the turning switch control valve 72 is operated to the belief turning position 72 b by the pilot operation valves 73 and 74.
Accordingly, when the steering lever 77 is operated to the right first turning position R1, the right turning control valve 67 is operated to the supply position 67a, the unload valve 70 is operated to the cutoff position 70a, and the right side The hydraulic oil is supplied to the clutch 33 (right occlusion portion 28) and the right turning clutch 39, the right side clutch 33 (right occlusion portion 28) is operated to be disconnected, and the right turning clutch 39 is in a transmission state. To be operated. In this case, since the left turning clutch 39 is in a semi-transmission state, the aircraft gently turns to the right as described in [13] above.

  As shown in FIGS. 2 to 4, when the steering lever 77 is operated to the right first turning position R1, the right turning control valve 67 is operated to the supply position 67a as described above, and the unload valve 70 is shut off. Simultaneously with the operation of 70a, the hydraulic oil begins to be supplied to the brake 40 via the proportional control valve 71 and the turn switching control valve 72 (the pivot turn position 72b), and the steering lever 77 is moved to the right first. The proportional control valve 71 increases the operating pressure of the brake 40 as the turning position R1 is operated to the second right turning position R2.

  As shown in FIGS. 2 to 4, the operating pressure of the brake 40 is increased by the proportional control valve 71 based on the operation position of the steering lever 77, and accordingly, the transmission shaft 34, the transmission gear 38, and the swing clutch case 37. And the braking force is applied to the right output gear 27 via the right turning clutch 39.

  In this case, as shown in FIG. 2, the power from the left side clutch 33 (the left occlusal portion 28) and the braking force of the brake 40 are simultaneously transmitted to the right output gear 27. In a range where the operating pressure of the brake 40 is low, the power from the left side clutch 33 (the left occlusion portion 28) overcomes the braking force of the brake 40 and the force from the left side clutch 33 (the left occlusion portion 28) The right output gear 27 is driven by the power. As a result, when the operating pressure of the brake 40 is in a low pressure range, the aircraft gradually turns to the right.

  Next, when the operating position of the steering lever 77 approaches the right second turning position R2 and the operating pressure of the brake 40 becomes high, the braking force of the brake 40 is applied to the left side clutch 33 (left The power output from the occlusal portion 28) is overcome, the braking force of the brake 40 causes the right output gear 27 to enter the braking state, and the aircraft turns right.

  As shown in FIGS. 2 to 4, when the steering lever 77 is operated to the left first turning position L1, the left turning control valve 68 is operated to the supply position 68a, and the unload valve 70 is operated to the cutoff position 70a. Then, hydraulic oil is supplied to the left side clutch 33 (the left occlusion portion 28) and the left turning clutch 39, and the left side clutch 33 (the left occlusion portion 28) is operated in a disconnected state to turn left. The clutch 39 is operated to the transmission state. At the same time, the same operation as described above is performed, and the aircraft gradually turns to the left. When the steering lever 77 is operated from the left first turning position L1 to the left second turning position L2, the same operation as described above is performed, and the aircraft turns to the left.

Next, the super turning state by the steering lever 77 will be described.
As shown in FIGS. 2 to 4, when the turning mode switch 78 is operated to the super turning position, the turning control valve 72 is operated to the super turning position 72 c by the pilot operation valves 73 and 74.
Accordingly, when the steering lever 77 is operated to the right first turning position R1, the right turning control valve 67 is operated to the supply position 67a, the unload valve 70 is operated to the cutoff position 70a, and the right side The hydraulic oil is supplied to the clutch 33 (right occlusion portion 28) and the right turning clutch 39, the right side clutch 33 (right occlusion portion 28) is operated to be disconnected, and the right turning clutch 39 is in a transmission state. To be operated. In this case, since the left turning clutch 39 is in a semi-transmission state, the aircraft gradually turns to the right.

  As shown in FIGS. 2 to 4, when the steering lever 77 is operated to the right first turning position R1, the right turning control valve 67 is operated to the supply position 67a as described above, and the unload valve 70 is shut off. Simultaneously with the operation of 70a, the hydraulic oil starts to be supplied to the reverse rotation clutch 42 via the proportional control valve 71 and the turn switching control valve 72 (super pivot turn position 72c). The proportional control valve 71 increases the operating pressure of the reverse rotation clutch 42 as the first turning position R1 is operated to the right second turning position R2.

  2-4, as the operating pressure of the reverse clutch 42 is increased by the proportional control valve 71 based on the operation position of the steering lever 77, the power of the transmission shaft 20 is transmitted to the transmission gear 23, 41, the reverse rotation clutch 42, the transmission shaft 34, the transmission gear 38, the turning clutch case 37, and the right turning clutch 39 are transmitted to the right output gear 27 as power in the direction opposite to that of the transmission shaft 26.

  In this case, as shown in FIG. 2, the power from the left side clutch 33 (the left occlusal portion 28) and the power from the reverse clutch 42 are transmitted to the right output gear 27 at the same time. In the range where the operating pressure of the reverse clutch 42 is low, the power from the left side clutch 33 (the left occlusion portion 28) overcomes the power from the reverse clutch 42 and the left side clutch 33 (the left occlusion portion 28). ) Drives the right output gear 27. As a result, when the operating pressure of the reverse clutch 42 is in a low pressure range, the aircraft gradually turns to the right.

  Next, when the operating position of the steering lever 77 approaches the right second turning position R2 and the operating pressure of the reverse clutch 42 becomes high, the power from the reverse clutch 42 is changed to the left side clutch 33 as shown in FIG. The right output gear 27 is driven by the power from the reverse clutch 42 by overcoming the power from the (left occlusal portion 28). In this state, the right output gear 27 is driven in the opposite direction with respect to the left output gear 27, and the aircraft turns to the right.

  As shown in FIGS. 2 to 4, when the steering lever 77 is operated to the left first turning position L1, the left turning control valve 68 is operated to the supply position 68a, and the unload valve 70 is operated to the cutoff position 70a. Then, hydraulic oil is supplied to the left side clutch 33 (the left occlusion portion 28) and the left turning clutch 39, and the left side clutch 33 (the left occlusion portion 28) is operated in a disconnected state to turn left. The clutch 39 is operated to the transmission state. At the same time, the same operation as described above is performed, and the aircraft gradually turns to the left. When the steering lever 77 is operated from the left first turning position L1 to the left second turning position L2, the same operation as described above is performed, and the aircraft turns to the left.

Next, the hydraulic circuit structure of the hydrostatic continuously variable transmission 7 will be described.
As shown in FIG. 5, the hydrostatic continuously variable transmission 7 includes an axial plunger type variable displacement hydraulic pump 7P and an axial plunger type variable displacement hydraulic motor 7M. The hydraulic pump 7P and the hydraulic motor 7M are connected to each other. It is configured to be connected by a pair of oil passages 7c. A charge pump 44 is connected to the input shaft 7 a of the hydrostatic continuously variable transmission 7, and the charge pump 44 is driven by the input shaft 7 a of the hydrostatic continuously variable transmission 7.

  As shown in FIG. 5, a bypass oil passage 83 is connected across the oil passage 7 c of the hydrostatic continuously variable transmission 7, and a charge oil passage 45 extending from the charge pump 44 is connected to the bypass oil passage 83. The charge oil passage 45 is provided with a filter 49. A check valve 84, a throttle portion 85, and a relief valve 86 are provided between a portion of the bypass oil passage 83 to which the charge oil passage 45 is connected and the oil passage 7c of the hydrostatic continuously variable transmission 7. The relief pressure of the relief valve 86 is set to the highest pressure allowed as a whole of the hydrostatic continuously variable transmission 7. A supply oil passage 47 is connected across an oil tank 46 provided separately from the mission case 8 and the charge pump 44, and a filter 48 is provided in the supply oil passage 47.

  As shown in FIG. 5, a relief valve 50 is connected to the charge oil passage 45, and the relief valve 50 is connected to a case 51 that houses the hydrostatic continuously variable transmission 7. An oil passage 52 is connected across the case 51 and the oil tank 46, and an oil cooler 53 is provided in the oil passage 52. With the above structure, the hydraulic oil in the oil tank 46 is supplied to the oil passage 7c of the hydrostatic continuously variable transmission 7 through the filter 48, the supply oil passage 47, the charge pump 44, and the charge oil passage 45, and surplus. The hydraulic oil is discharged to the case 51 through the relief valve 50. The hydraulic oil from each part of the hydrostatic continuously variable transmission 7 is discharged to the case 51, and the hydraulic oil in the case 51 passes through the oil passage 52 and the oil cooler 53 and is returned to the oil tank 46.

Next, the operation structure of the hydraulic pump 7P of the hydrostatic continuously variable transmission 7 will be described.
As shown in FIGS. 4 and 5, the hydraulic pump 7P of the hydrostatic continuously variable transmission 7 is configured to be steplessly variable in the neutral state, the forward side and the reverse side, and is in a neutral position N, the forward side F, and the reverse side. A shift lever 43 (corresponding to a hydraulic pump operating tool) that can be operated on the side R is provided in the operating unit 3, and the shift lever 43 and the swash plate 7Pa of the hydraulic pump 7P of the hydrostatic continuously variable transmission 7 are linked to each other. 80 are mechanically linked. Although not illustrated, a friction type holding mechanism for holding the operated shift lever 43 in its position is provided.

  As shown in FIG. 4, an electric motor 55 for applying an operating force (assist force) to the speed change lever 43 and an operation sensor (FIG. 5) for detecting that the speed change lever 43 is about to be operated to the forward side F or the reverse side R. The electric motor 55 is operated by the control device 79 as follows based on the detection value of the operation sensor.

  As shown in FIG. 4, when the transmission lever 43 is about to be operated to the forward side F, this operation is detected by the operation sensor, and the electric motor 55 is activated to apply the operating force to the forward side F to the transmission lever 43. give. When the shift lever 43 is about to be operated to the reverse side R, this operation is detected by the operation sensor, and the electric motor 55 is activated to apply an operation force to the reverse side R to the shift lever 43.

  As shown in FIG. 4, the swash plate 7Pa of the hydraulic pump 7P in the hydrostatic continuously variable transmission 7 is operated by the shift lever 43 so that the swash plate 7Pa of the hydraulic pump 7P is set to the neutral position N, the forward side F, and the reverse side. By operating the electric motor 55, the transmission lever 43 can easily operate the swash plate 7Pa of the hydraulic pump 7P to the forward side F and the reverse side R. When the operation of the shift lever 43 toward the forward side F and the reverse side R stops, the electric motor 55 also stops, and the swash plate 7Pa of the hydraulic pump 7P is held at that position.

Next, operations of the hydraulic motor 7M, the harvesting clutch 17, the threshing clutch 4A, and the harvesting transmission 18 of the hydrostatic continuously variable transmission 7 will be described.
As shown in FIG. 4, the grip 43 a at the top of the shift lever 43 is provided with a travel shift switch 81 at the bottom of the lateral surface of the grip 43 a of the shift lever 43, and the grip 43 a of the shift lever 43 is A cutting shift switch 82 is provided at the upper portion of the rear surface portion. The travel speed change switch 81 and the mowing speed change switch 82 are configured as push buttons that are urged to return to the return side (projection side), and operation signals of the travel speed change switch 81 and the mowing speed change switch 82 are input to the control device 79. Is done.

As shown in FIGS. 4 and 5, the hydraulic motor 7M of the hydrostatic continuously variable transmission 7 is configured to be steplessly variable in the range of the high speed position H and the low speed position L, and the hydrostatic continuously variable transmission apparatus. 7 is provided with an operating cylinder 56 (corresponding to the holding means) that holds the swash plate 7Ma (corresponding to the capacity changing operation section) of the hydraulic motor 7M that moves to the low speed side with an operating force that moves it to the high speed side. It has been.
As the position of the swash plate 7Ma of the hydraulic motor 7M, a potentiometer 89 (corresponding to a position detecting means) for detecting the position of the piston of the operating cylinder 56 is provided, and the position of the piston of the operating cylinder 56 is detected by the potentiometer 89. The position of the swash plate 7Ma of the hydraulic motor 7M is detected, and the detection value P of the potentiometer 89 is input to the control device 79.

As shown in FIGS. 4 and 5, the oil passage 57 branches from the charge oil passage 45, and the oil passage 57 is connected to an oil chamber 56 a that operates the operation cylinder 56 to the high speed side. A spring 56b for urging is provided. A pressure control valve 58 constituted by an electromagnetic proportional control valve as an operation force adjusting means for changing and adjusting the operation force of the operation cylinder 56 is provided in the oil passage 57, and the pressure in the oil chamber 56a of the operation cylinder 56 is adjusted. When the pressure rises, the operating cylinder 56 operates the swash plate 7Ma of the hydraulic motor 7M to the high speed side against the traveling load and the urging force of the spring 56b, and when the pressure in the oil chamber 56a of the operating cylinder 56 decreases, The swash plate 7Ma is operated to the low speed side by the traveling load and the urging force of the spring 56b.
In other words, the operation cylinder 56 is a hydraulic cylinder that is changed by hydraulic pressure to which an operation force for moving the swash plate 7Ma of the hydraulic motor 7M to the high speed side is supplied, and the pressure control valve 58 is an operation cylinder 56. Is configured to change and adjust the pressure of the hydraulic pressure supplied to.

  As shown in FIG. 4, a vehicle speed sensor 91 is provided as vehicle speed detection means for detecting the vehicle speed, and a detected value P of the vehicle speed sensor 91 is input to the control device 79. As will be described later, the control device 79 is The vehicle speed sensor 91 is configured to determine whether or not the vehicle speed detected is equal to or higher than the set vehicle speed. Although not shown, the vehicle speed sensor 91 is configured to detect and act on a gear provided on a drive shaft for driving the traveling device 1 to generate a pulse corresponding to the vehicle speed.

  As shown in FIG. 4, an operation motor 65 is provided, and the operation motor 65, the reaping clutch 17, the threshing clutch 4 </ b> A, and the reaping transmission device 18 are mechanically linked. The clutch 4A and the cutting transmission 18 are operated. By the operating motor 65, the cutting clutch 17 and the threshing clutch 4A are operated in the disconnected state and the cutting transmission 18 is operated to the low speed position, and the cutting clutch 17 and the threshing clutch 4A are operated in the transmission state and the cutting transmission 18 The three states appear in the state in which the cutting clutch 17 and the threshing clutch 4A are operated in the transmission state and the cutting transmission 18 is operated in the high speed position.

  As shown in FIG. 6, a moving traveling state, a standard cutting state, and a low-speed cutting state are set. In the traveling state, the standard cutting state, and the low-speed cutting state, as shown in FIGS. 4 and 6, the control device 79. Accordingly, the pressure control valve 58, the operation motor 65, and the display unit 87 provided in the operation unit 3 are operated as follows.

In the traveling state, the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 is operated to the high speed position H for traveling, the reaping clutch 17 and the threshing clutch 4A are operated in the disconnected state, and the reaping transmission device. 18 is a state where the low speed position is operated, and the high speed position H is displayed on the display unit 87.
In the standard reaping state, the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 is operated to the middle speed position M for reaping work, the reaping clutch 17 and the threshing clutch 4A are operated to the transmission state, and the reaping speed change. In this state, the device 18 is operated to the low speed position, and the medium speed position M is displayed on the display unit 87.
In the low-speed cutting state, the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 is operated to the low-speed position L for the overturning cutting operation, the cutting clutch 17 and the threshing clutch 4A are operated in the transmission state, and the cutting shift is performed. The device 18 is in a state of being operated to the high speed position, and the low speed position L is displayed on the display unit 87. This low-speed cutting state is selected when cutting a crop that is heavily laid down.

As shown in FIG. 6, the control device 79 is configured to operate the pressure control valve 58 and the operation motor 65 as follows based on the pushing operation of the travel shift switch 81 and the cutting shift switch 82.
When the travel shift switch 81 is pushed and operated in the state where the mobile travel state is set, the standard cutting state is set. When the travel shift switch 81 is pushed and operated in the state where the standard cut state is set, the mobile travel state is set. Is set. Thus, every time the travel shift switch 81 is pushed, the traveling state and the standard cutting state are alternately set.
In this case, even if the cutting shift switch 82 is pushed in a state where the traveling state is set, the pushing operation is ignored and the traveling state is maintained. When the travel shift switch 81 is pushed, and the cutting shift switch 82 is pushed in a state where the standard cutting state is set, the low-speed cutting state is set.

When the cutting shift switch 82 is pushed in the state where the standard cutting state is set, the low-speed cutting state is set. When the cutting shift switch 82 is pushed in a state where the low-speed cutting state is set, the standard cutting state is set. Thus, every time the cutting shift switch 82 is pushed, the standard cutting state and the low-speed cutting state are alternately set.
In this case, even if the travel shift switch 81 is pressed in a state where the low-speed cutting state is set, this pressing operation is ignored and the low-speed cutting state is maintained. If the travel shift switch 81 is pushed and operated in a state where the standard cut state is set by pushing the cut shift switch 82, the traveling state is set.

As described above, the high speed position H, the medium speed position M, and the low speed position L are determined as the set target positions of the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7. 81 and the mowing shift switch 82 function as selection means for selecting one of the set target positions.
Then, the control device 79 maintains the swash plate 7Ma of the hydraulic motor 7M at the target position set by the travel shift switch 81 and the cutting shift switch 82 among the plurality of set target positions. It is comprised so that the electric current value which supplies with electricity may be controlled.

Further, the control device 79 operates to move the swash plate 7Ma of the hydraulic motor 7M to the high speed side exceeding the set upper limit value even if the swash plate 7Ma of the hydraulic motor 7M moves to the low speed side of the set target position. The pressure control valve 58 is configured to be controlled in a form that does not increase the force.
When the explanation is added, the current value energized to the pressure control valve 58 corresponds to the operating force for moving the swash plate 7Ma of the hydraulic motor 7M to the high speed side by the operating cylinder 56. As shown in FIG. A current detection sensor D for detecting a current value a energized to the pressure control valve 58 and a drive circuit 93 for the pressure control valve 58 are provided.
Then, a set upper limit current value corresponding to the set upper limit value corresponding to each of the high speed position H, the medium speed position M, and the low speed position L as the set target positions for maintaining the swash plate 7Ma of the hydraulic motor 7M. A1, A2, and A3 are set in a state where the lower set target position is lower, and the control device 79 sets the current value a to be supplied to the pressure control valve 58 based on the detection information of the current detection sensor D. It is configured to control the current value a energized to the pressure control valve 58 in a form that does not increase beyond the set upper limit current values A1, A2, and A3.

In this way, by controlling the current value supplied to the pressure control valve 58 in such a manner that the current value a supplied to the pressure control valve 58 does not increase beyond the set upper limit current values A1, A2, and A3, the engine 6 It is possible to suppress an excessive load.
That is, when the swash plate 7Ma of the hydraulic motor 7M is maintained at the high speed position H, the traveling load increases, and the swash plate 7Ma of the hydraulic motor 7M is moved to the high speed position with an operating force corresponding to the set upper limit current value A1. If it cannot be maintained at H, the swash plate 7Ma of the hydraulic motor 7M will move to the lower speed side than the high speed position H, and the traveling speed will be reduced and the load on the engine 6 will be prevented from increasing. .
Similarly, when the swash plate 7Ma of the hydraulic motor 7M is maintained at the medium speed position H, the traveling load increases, and the swash plate 7Ma of the hydraulic motor 7M is operated with the operating force corresponding to the set upper limit current value A2. If the medium speed position M cannot be maintained, the swash plate 7Ma of the hydraulic motor 7M moves to the lower speed side than the medium speed position H, and the traveling speed is reduced to prevent the load on the engine 6 from increasing. Will do.

The low speed position L as the set target position of the swash plate 7Ma of the hydraulic motor 7M is set at a position slightly higher than the movement limit of the swash plate 7Ma to the low speed side, and the swash plate 7Ma of the hydraulic motor 7M. When the swash plate 7Ma of the hydraulic motor 7M cannot be maintained at the low speed position L with the operating force corresponding to the set upper limit current value A3 when the vehicle is maintained at the low speed position H, the hydraulic motor Although the 7M swash plate 7Ma moves to the lower speed side than the low speed position L, the movement amount is small, and the traveling speed is reduced by a small amount, and the load on the engine 6 is reduced. Is not very effective.
Incidentally, the high speed position H as the set target position of the swash plate 7Ma of the hydraulic motor 7M is set to a position slightly on the low speed side from the limit of movement of the swash plate 7Ma to the high speed side.

  As described above, when the traveling load increases, the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 is moved from the high speed position H, the medium speed position M, and the low speed position L as the set target positions. Although the load on the engine 6 is reduced by moving to the side, the control device 79 causes the hydrostatic pressure to be reduced when the load on the engine 6 is excessive in spite of the reduced traveling speed. Although it is configured to perform a deceleration operation process in which the swash plate 7Pa of the hydraulic pump 7P in the variable continuously variable transmission 7 is operated to the deceleration side by the electric motor 55, a detailed description of the deceleration operation process is omitted.

When the control device 79 determines that it is in the reference running state, the current value a energized to the pressure control valve 58 when the swash plate 7Ma of the hydraulic motor 7M is maintained at the medium speed position M as the set target position. Is configured to execute a correction process for correcting the set upper limit current values A1, A2, and A3.
That is, the relationship between the current value in the pressure control valve 58 constituted by an electromagnetic proportional control valve and the pressure of the hydraulic pressure supplied to the operation cylinder 56 (operation force) changes linearly as shown in FIG. 13, for example. Although having such characteristics, due to individual differences, there are variations in the characteristics as indicated by characteristic lines L1, L2, and L3 in FIG. As a result, the current values required to obtain the same pressure (operating pressure) in the operating cylinder 56 (illustrated as F1, F2, and F3 in FIG. 13) become different values.

  Accordingly, when the traveling load is relatively stable and the traveling load is in the reference traveling state in which the magnitude of the traveling load can be predicted to some extent, the medium speed position with the swash plate 7Ma of the hydraulic motor 7M as the set target position. The set upper limit current values A1, A2, and so on that the error due to the variation in characteristics due to such individual differences is reduced by using the current value a energized to the pressure control valve 58 when maintained at M. , A3 is corrected to an appropriate value.

  In other words, the control device 79 detects that the stock cutting sensor 90 detects the cutting operation state, the vehicle speed detected by the vehicle speed sensor 91 is equal to or higher than the set vehicle speed, and the operation position detection sensor Q. When the straight running state is detected, each reference condition is satisfied, and the reference traveling state is determined. When the reference traveling state is determined, the reference traveling state is determined. On the basis of the value obtained by averaging the current value a to be supplied to the pressure control valve 58 when the swash plate 7Ma of the hydraulic motor 7M is maintained at the medium speed position M while the state to be performed continues. The values A1, A2, and A3 are configured to be corrected.

Hereinafter, the control operation of the control device 79 will be described based on the flowcharts shown in FIGS.
FIG. 7 shows the main flow. When the power is turned on, the initial setting is performed first (# 1). In this initial setting, the traveling state is set.
Once the initial setting has been made, it is next determined whether or not the vehicle is in a traveling state (# 2). If in the traveling state, whether or not the traveling shift switch 81 has been operated, that is, the traveling shift switch 81 is It is determined whether or not it is turned on (# 3), and if the travel shift switch 81 is not operated, the process for moving travel state is performed in which the mowing clutch 17 and the threshing clutch 4A are disconnected and the mowing transmission 18 is lowered. (# 4) and a high-speed operation process (# 5) for maintaining the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 at the high-speed position H is executed.
Next, when it is determined that the vehicle is in the reference running state, the correction process is executed (# 6), and then the process returns to the process of determining whether or not the moving running state is # 2.

  When it is determined that the travel shift switch 81 has been operated in # 3, it is assumed that it is a change to the standard reaping state, and the reaping clutch 17 and the threshing clutch 4A are set in the transmission state and the reaping transmission device 18 is set to a low speed The mowing state process (# 10) and the medium speed operation process (# 11) for maintaining the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 at the medium speed position M are executed, and then # The process proceeds to the correction process No. 6.

  If it is determined in # 2 that the vehicle is not in the traveling state, it is determined whether or not it is in the standard cutting state (# 7). If it is in the standard cutting state, it is determined whether or not the traveling shift switch 81 is turned on. Discriminate (# 8). If the travel shift switch 81 is not operated, it is determined whether or not the cutting shift switch 82 is operated, that is, whether or not the cutting shift switch 82 is turned on (# 9), and the cutting shift switch 82 is operated. If not, the process proceeds to the standard cutting state process of # 10.

If it is determined at # 8 that the travel shift switch 81 has been turned ON, it is determined that the travel shift state has been changed, and the process proceeds to # 4 for travel travel state processing.
When it is determined in # 9 that the cutting shift switch 82 has been turned ON, it is determined that the cutting is to the low-speed cutting state, and the cutting clutch 17 and the threshing clutch 4A are set in the transmission state to make the cutting transmission 18 high speed. The state process (# 13) and the low speed operation process (# 14) for maintaining the swash plate 7Ma of the hydraulic motor 7M in the hydrostatic continuously variable transmission 7 at the low speed position L are executed, and then the correction of # 6 Transition to processing.

  If it is determined in # 7 that it is not in the standard cutting state, that is, if it is determined in the low speed cutting state, it is determined whether or not the cutting shift switch 82 is turned on in # 12, and the cutting shift switch 82 is turned on. If it is determined that the change is made to the standard cutting state, the process proceeds to the standard cutting state process of # 10, and it is determined that the cutting shift switch 82 is turned ON in # 12. , # 13 shifts to the low-speed cutting state process.

FIG. 8 shows the control operation of the high-speed operation process described above.
First, it is determined whether or not the detection value P of the potentiometer 89 for detecting the position of the piston of the operating cylinder 56 is a position corresponding to the high speed position H (# 21), and the detection value P is a position corresponding to the high speed position H. If it is, the process returns to the main flow.
If it is determined in # 21 that the detected value P is not a position corresponding to the high speed position H, it is determined whether or not the detected value P is on the higher speed side than the position corresponding to the high speed position H (# 22). When it is determined that the speed is high, a value obtained by subtracting the set amount α from the current target current value A is set as a new target current value A (# 23), and the current detected by the current detection sensor D A current control process for instructing the drive circuit 93 to give a current increase / decrease command is executed so that the value a becomes the new target current value A (# 24), and then the process returns to the main flow.

When it is determined in # 22 that the detected value P is not on the higher speed side than the position corresponding to the high speed position H, that is, the detected value P is on the lower speed side than the position corresponding to the high speed position H, the target current value A Is smaller than the set upper limit current value A1 corresponding to the high speed position H (# 25). If it is determined that the current is smaller, the current target current value A is determined in # 26. A value obtained by adding the set amount α is set as a new target current value A, and thereafter, the process proceeds to a current control process of # 24.
If it is determined in # 25 that the target current value A is not smaller than the set upper limit current value A1 corresponding to the high speed position H, the current target current value A is set to the set upper limit current value A1, The current control process proceeds to # 24.

FIG. 9 shows the control operation of the medium speed operation process described above.
First, it is determined whether or not the detection value P of the potentiometer 89 for detecting the position of the piston of the operating cylinder 56 is a position corresponding to the medium speed position M (# 41), and the detection value P corresponds to the medium speed position M. If it is a position to perform, the process returns to the main flow.
If it is determined in # 41 that the detected value P is not a position corresponding to the medium speed position M, it is determined whether or not the detected value P is higher than the position corresponding to the medium speed position M ( # 42) When it is determined that the speed is high, a value obtained by subtracting the set amount α from the current target current value A is set as a new target current value A (# 43) and detected by the current detection sensor D. The current control process for instructing the drive circuit 93 to give a current increase / decrease command is executed so that the current value a to become the new target current value A (# 44), and then the process returns to the main flow.

When it is determined at # 42 that the detected value P is not on the higher speed side than the position corresponding to the medium speed position M, that is, the detected value P is on the lower speed side than the position corresponding to the medium speed position H, It is determined whether or not the value A is smaller than the set upper limit current value A2 corresponding to the medium speed position M (# 45). If it is determined that the value A is smaller, the current target current is determined in # 46. A value obtained by adding the set amount α from the value A is set as a new target current value A, and then the process proceeds to a current control process of # 44.
If it is determined at # 45 that the target current value A is not smaller than the set upper limit current value A2 corresponding to the medium speed position M, the current target current value A is set to the set upper limit current value A2, The current control process proceeds to # 44.

FIG. 10 shows the control operation of the low-speed operation process described above.
First, it is determined whether or not the detected value P of the potentiometer 89 for detecting the position of the piston of the operating cylinder 56 is a position corresponding to the low speed position L (# 61), and the detected value P is a position corresponding to the low speed position L. If it is, the process returns to the main flow.
If it is determined in # 61 that the detected value P is not a position corresponding to the low speed position L, it is determined whether or not the detected value P is higher than the position corresponding to the low speed position L (# 62). When it is determined that the speed is high, a value obtained by subtracting the set amount α from the current target current value A is set as a new target current value A (# 63), and the current detected by the current detection sensor D Current control processing for instructing a current increase / decrease command to the drive circuit 93 is executed so that the value a becomes the new target current value A (# 64), and then the process returns to the main flow.

When it is determined in # 62 that the detected value P is not on the high speed side from the position corresponding to the low speed position L, that is, the detected value P is on the low speed side than the position corresponding to the low speed position H, the target current value A Is smaller than the set upper limit current value A3 corresponding to the low speed position L (# 65). If it is determined that it is smaller, the current target current value A is determined in # 66. A value obtained by adding the set amount α is set as a new target current value A, and then the process proceeds to # 64 current control processing.
When it is determined in # 65 that the target current value A is not smaller than the set upper limit current value A3 corresponding to the low speed position L, the current target current value A is set to the set upper limit current value A3, The process proceeds to # 64 current control processing.

FIG. 11 shows the control operation of the correction processing described above.
First, the stock sensor 90 detects an on-state (cutting work state) (# 80), and detects that the vehicle speed detected by the vehicle speed sensor 91 is equal to or higher than the set vehicle speed (# 81). If the position detection sensor Q detects a straight traveling state (# 82), that is, if it is determined that the vehicle is in the reference traveling state, the previous integration is performed while the state of determining that the vehicle is in the reference traveling state continues. If it is determined that the set time has elapsed (# 83), the current value a detected by the current detection sensor D at that time is added to the integrated value, the current value is integrated, and the current value is integrated. The integrated value is stored in a non-volatile memory (not shown) (# 84). Further, the accumulated number of times is counted (# 85).

  When it is determined that the cutting work in one work process is completed and the stock sensor 90 has just been switched from the ON state (the cutting work state) to the OFF state (the non-cutting work state) (# 86). ), And averaging the accumulated current values (# 87). That is, the average current value Av is obtained by dividing the integrated value by the number n. Next, low-pass processing is executed (# 88). This low-pass processing will be specifically described. The value obtained by multiplying the reference current value Ar obtained in the previous work process by “9” and the average current value Av obtained this time is divided by “10”. To obtain a new reference current value Ar. By repeating such processing, a value corresponding to a value averaged over a long travel distance is obtained as much as possible.

  Next, the set upper limit current value A2 corresponding to the medium speed position M is corrected to the newly obtained reference current value Ar, and at the same time, the set upper limit current value A1 and the low speed position L corresponding to the high speed position H are corrected. The corresponding set upper limit current value A3 is also corrected (# 89), and the corrected set upper limit current values A1, A2, and A3 are updated and stored in the nonvolatile memory (# 90).

When the correction of the set upper limit current values A1, A2, and A3 is described, the current value in the pressure control valve 58 constituted by an electromagnetic proportional control valve and the pressure of the hydraulic pressure (operating force) supplied to the operating cylinder 56 13 changes linearly as shown in FIG. 13. Of the three characteristic lines L1, L2, and L3 shown in FIG. 13, the central characteristic line L2 is initially set in the production stage. Assuming that the reference current value Ar (A2) detected this time is located on the characteristic line L3, for example, when the pressure varies with individual differences, the current value when the pressure is the same is Although each line is offset, it is known that each characteristic line has the same inclination of the straight line and changes in a state of translation. Therefore, when the reference current value Ar (A2) detected this time is positioned on the characteristic line L3, the reference current value Ar (A2) is set to the high speed position H with the same correction amount as the set upper limit current value A2 corresponding to the medium speed position M. The corresponding set upper limit current value A1 and the set upper limit current value A3 corresponding to the low speed position L can be similarly corrected.
In addition, as a result of the reference running state, the hydraulic pressure (operating pressure) of the operating cylinder 56 is output as a value close to the pressure F2 when the set upper limit current value A2 is initially set. Estimate.

[Another embodiment]
Hereinafter, another embodiment of the present invention will be described.

(1) As the correction process, control may be executed as follows.
That is, the control device is configured to determine that the vehicle is in the reference running state when an on-state (cutting work state) is detected by the stock sensor serving as the work state detecting means, and the reference running is performed. If it is determined that it is in a state, a set time before the switching timing at which the stock state sensor switches from the state in which the on state (cutting work state) is detected to the state in which the off state (non-cutting work state) is detected. From the current value a energized to the pressure control valve 58 when the swash plate 7Ma of the hydraulic motor 7M is maintained at the medium speed position M during the switching timing until the switching timing, the set upper limit current values A1, A2, and , A3 may be controlled to be corrected.

FIG. 12 shows the control operation of the correction process of another embodiment.
First, when the stock sensor 90 detects an ON state (reaping work state) at # 100, that is, when it is determined that the vehicle is in the reference running state, the state of determining that the vehicle is in the reference running state continues. If it is determined that the set time has elapsed since the last storage in # 101, the current value a detected by the current detection sensor D at that time is stored in the nonvolatile memory in # 102. . At this time, the current value a is sequentially stored in association with the passage of time.

  Then, it is determined that the harvesting work in one work process is finished, and in # 103, it is immediately after the stock sensor 90 is switched from the on state (reaching work state) to the off state (non-reaching work state). Then, in step # 104, the current value a stored before the set time is obtained as the reference current value Ar. Next, in # 105, the set upper limit current value A2 corresponding to the medium speed position M is corrected to the newly obtained reference current value Ar, and at the same time, the set upper limit current value A1 corresponding to the high speed position H and the low speed position. The set upper limit current value A3 corresponding to L is also corrected, and the set upper limit current values A1, A2, and A3 corrected in # 89 are updated and stored in the nonvolatile memory. The method of correcting the set upper limit current values A1, A2, and A3 is the same as in the above embodiment.

(2) As the correction process, control may be executed as follows.
That is, in the above embodiment and another embodiment of the above (1), the control device automatically determines based on the detection information of the work state detection means and the other detection means. Then, the control device may execute the correction process based on an operation command of an instruction switch as a manually operated command means.

  Specifically, with the combine set to the traveling state, the driver operates the indicator switch while running on a hard and flat road surface such as a concrete road surface at the set speed. , The current value a detected by the current detection sensor D is repeatedly detected and stored every set time, and then when the operator commands the end by operating the instruction switch again, a plurality of stored values are stored. Is determined as a reference current value Ar, the reference current value Ar is corrected to the set upper limit current value A1 corresponding to the high speed position H, and the set upper limit current values A2 and A3 are also corrected. The correction method is the same as in the above embodiments.

(3) In the above embodiment, the holding unit is exemplified by the hydraulic cylinder that is changed by the hydraulic pressure to which the operating force is supplied. However, other configurations can be used.
For example, a drive rotator for moving the operation unit to the high speed side, and the drive rotator and the operation unit are linked to each other using a friction transmission mechanism whose transmission force can be changed and adjusted, thereby transmitting the friction transmission mechanism. By changing and adjusting the force, the operation force for moving the operating portion to the high speed side can be changed and adjusted.
The operating force adjusting means for changing and adjusting the operating force of the holding means is variously changed according to the configuration of the holding means.

(4) In the above embodiment, the case where the set target positions for maintaining the operation unit are three positions that are different from the high speed position, the medium speed position, and the low speed position is exemplified. You may implement with the form defined as a position, and you may implement with the form which defines four or more multiple positions as a setting target position.

(5) In the above embodiment, the case where the setting upper limit value is determined separately for each of the three setting target positions for maintaining the operation unit in a state where the setting target position on the low speed side is set lower is exemplified. Alternatively, only the set upper limit value corresponding to the high speed position may be determined.

(6) In the above embodiment, the combine as a work vehicle has been exemplified, but the present invention can be applied to various work vehicles such as a tractor and a transport vehicle.

2 Mowing processing unit 4 Threshing device 6 Engine 7 Hydrostatic continuously variable transmission 7M Hydraulic motor of hydrostatic continuously variable transmission 7Ma Operation unit (swash plate)
56 Holding means (hydraulic cylinder)
58 Operating force adjustment means (Electromagnetic proportional valve)
79 Control means 81, 82 Selection means 89 Position detection means 90 Work state detection means 91 Vehicle speed detection means Q Steering state detection means

Claims (6)

A traveling control device for a work vehicle including a hydrostatic continuously variable transmission for traveling to which engine power is transmitted,
Holding means for holding the operation part for changing the capacity of the variable capacity hydraulic motor of the hydrostatic continuously variable transmission in the low speed side with an operating force for moving the high speed side;
An operating force adjusting means for changing and adjusting the operating force of the holding means in a form in which the operating force of the holding means is increased as the command value that changes in size is larger;
Position detecting means for detecting the position of the operation unit;
Control means for changing and adjusting a command value commanded to the operating force adjusting means so as to maintain the operating portion at a set target position based on detection information of the position detecting means;
The control means is
The command value to be commanded to the operating force adjusting means is changed and adjusted in such a manner that the command value is not increased beyond the set upper limit value even if the operation unit moves to a lower speed side than the set target position. And
A work vehicle travel control device configured to correct the set upper limit value based on the command value when the operation unit is maintained at the set target position when it is determined that the vehicle is in a reference travel state. As the set target position, a plurality of set target positions that are different positions are determined,
Selection means for selecting any of the plurality of set target positions is provided,
The control means changes and adjusts a command value to be instructed to the operation force adjustment means so that the operation unit is maintained at the set target position selected by the selection means among the plurality of set target positions. The traveling control device for a work vehicle according to claim 1 configured as described above.   The travel control device for a work vehicle according to claim 2, wherein the set upper limit value is set so as to be lower for each of the plurality of set target positions at a lower set target position. The holding means is a hydraulic cylinder that is changed by a hydraulic pressure to which an operating force is supplied;
An electromagnetic proportional valve that changes and adjusts the pressure of the hydraulic pressure supplied to the hydraulic cylinder in a form in which the operating force adjusting means increases the operating force of the holding means as the energized current value as the command value increases. And
The said control means is comprised so that the electric current value which supplies with electricity to the said solenoid proportional valve may be changed and adjusted in the form which does not increase exceeding the setting upper limit electric current value corresponding to the said setting upper limit value. The travel control device for a work vehicle according to claim 1. The engine is mounted on a combine as a work vehicle, and the power of the engine is transmitted to a cutting and processing unit and a threshing device,
Work state detecting means for detecting whether the state is a cutting work state or a non-cutting work state is provided,
The control means is
When the cutting state is detected by the working state detection means, it is configured to determine that it is the reference running state, and
If it is determined that the vehicle is in the reference running state, a set time before the switching timing for switching from the state in which the cutting state is detected by the working state detection unit to the state in which the non-cutting state is detected 5. The apparatus according to claim 1, wherein the set upper limit value is corrected based on the command value when the operation unit is maintained at the set target position before the switching timing. The traveling control device for a work vehicle according to item. The engine is mounted on a combine as a work vehicle, and the power of the engine is transmitted to a cutting and processing unit and a threshing device,
A work state detection means for detecting whether the state is a cutting work state or a non-reaping work state, a vehicle speed detection means for detecting a vehicle speed, and a steering state detection means for detecting whether the vehicle is traveling straight or turning. Is provided,
The control means is
The cutting state is detected by the working state detecting means, the vehicle speed detected by the vehicle speed detecting means is equal to or higher than a set vehicle speed, and the straight traveling state is detected by the steering state detecting means. Is configured to determine that the vehicle is in the reference running state when each condition is satisfied, and
When it is determined that the vehicle is in the reference running state, the command value for maintaining the operation unit at the set target position is averaged while the state of determining that the vehicle is in the reference running state continues. The travel control device for a work vehicle according to any one of claims 1 to 4, wherein the travel upper limit value is configured to correct the set upper limit value.

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