JP7348868B2 - Work vehicle transmission - Google Patents

Description

The present invention relates to a transmission device for a work vehicle used in road construction and the like.

As a transmission device for this type of work vehicle, for example, Patent Document 1 discloses a wheel loader that runs by rotationally driving drive wheels using an HST (Hydro Static Transmission) using an engine as a power source. In this wheel loader, a variable displacement hydraulic pump is driven by the HST engine, and hydraulic oil discharged from the hydraulic pump is supplied to and driven by a variable displacement hydraulic motor. The hydraulic motor is connected to the driving wheels via a two-stage transmission, and the driving force of the hydraulic motor is changed in speed by the transmission and transmitted to the driving wheels, thereby causing the wheel loader to travel.

Patent No. 5899167 specification

By the way, an operator on board this type of work vehicle must perform work operations to carry out the original purpose of road surface excavation work, compaction work, etc., in parallel with driving operations to move the vehicle. Therefore, it is desired to automatically control the gear position of the HST in order to reduce the burden. For example, as automatic gear change control, vehicle speed feedback may be considered, which adjusts the vehicle speed according to the operation state of a travel operation member operated by an operator. Specifically, a target vehicle speed is set based on the operation state of the travel operation member, the actual vehicle speed is detected by a vehicle speed sensor, and in order to maintain the actual vehicle speed at the target vehicle speed, the tilting angle of the hydraulic motor is controlled, for example, by PID control, etc. Execute. The hydraulic motor has the characteristic of increasing its rotational speed as the tilting angle decreases, so when the actual vehicle speed is lower than the target vehicle speed, the hydraulic motor's tilting angle is controlled to decrease, and conversely, it increases the rotational speed to the target vehicle speed. On the other hand, when the actual vehicle speed is low, the tilting angle of the hydraulic motor is controlled to increase.

However, such vehicle speed feedback is not normally executed under driving conditions such as driving uphill or towing another vehicle, resulting in a problem that the vehicle becomes unable to travel. That is, for example, when a vehicle traveling on a flat road enters an uphill road, the traveling load acting on the hydraulic motor increases and the vehicle speed decreases. In order to maintain the target vehicle speed, the tilting angle of the hydraulic motor is controlled in a decreasing direction by vehicle speed feedback, but on the other hand, the hydraulic motor has a characteristic of decreasing its driving force as the tilting angle decreases. For this reason, even though it is necessary to increase the driving force to maintain the vehicle speed, the driving force of the hydraulic motor decreases and the vehicle speed gradually decreases. At this time, the oil pressure in the HST circuit (the oil pressure of the hydraulic oil supplied from the hydraulic pump to the hydraulic motor) increases rapidly, and the relief valve opens to protect the circuit, which ultimately causes the hydraulic motor to stop and the vehicle to stop. You will be unable to drive.

The present invention has been made to solve these problems, and its purpose is to reduce the burden on the operator by automatically shifting the transmission, and to increase the running load acting on the hydraulic motor. To provide a transmission device for a work vehicle that allows the vehicle to continue running even under running conditions without becoming unable to run.

In order to achieve the above object, the transmission device for a work vehicle of the present invention has a variable displacement hydraulic motor that reduces the rotational speed and increases the driving force as the tilting angle increases. In a transmission device for a work vehicle, which supplies hydraulic oil from a hydraulic pump driven by a power source to the hydraulic motor, and controls the rotational speed of the rolling wheel according to a tilting angle of the hydraulic motor. , an operation state detection device that detects the operation state of a travel operation member operated by an operator; a vehicle speed detection device that detects the travel speed of the work vehicle as an actual vehicle speed; and the travel operation detected by the operation state detection device. a normal mode execution unit that executes a normal mode in which a target vehicle speed is set according to the operation state of a member, and a tilting angle of the hydraulic motor is feedback-controlled based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device; a running load determination unit that determines the running load acting on the hydraulic motor and makes a running load increase determination when the running load increases; a hill-climbing mode for executing a hill-climbing mode in which the tilting angle of the hydraulic motor is controlled to be increased compared to the tilting angle based on the control of the normal mode execution unit when the determination unit determines that the running load has increased; further comprising: an execution unit; and an oil pressure detection device that detects the oil pressure of hydraulic oil supplied from the hydraulic pump to the hydraulic motor; When the condition where the climbing mode switching judgment pressure is equal to or higher than the climbing mode switching judgment pressure continues for a preset climbing mode switching judgment time, a running load increase judgment is made, and the climbing mode execution unit detects the oil pressure with respect to the climbing mode switching judgment pressure. The tilt angle is controlled to increase as the excess oil pressure detected by the device increases .
In addition , the transmission device for a work vehicle of the present invention connects a variable displacement hydraulic motor to the running wheels, which has characteristics of decreasing the rotational speed and increasing the driving force as the tilting angle increases, and the power source is In a transmission device for a work vehicle that supplies hydraulic oil from a hydraulic pump driven by a hydraulic motor to the hydraulic motor and controls the rotational speed of the running wheels according to a tilting angle of the hydraulic motor, the transmission is operated by an operator. an operation state detection device that detects the operation state of the operation member; a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed; a normal mode execution unit that executes a normal mode that sets a target vehicle speed and feedback-controls a tilting angle of the hydraulic motor based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device; a running load determination unit that determines a running load to be increased and makes a running load increase determination when the running load increases; and a running load determination unit that determines a running load increase while the normal mode execution unit is executing the normal mode. a hill-climbing mode execution unit that executes a hill-climbing mode that controls the tilting angle of the hydraulic motor to an increasing side compared to the tilting angle based on the control of the normal mode execution unit when the hydraulic motor is lowered; The hill-climbing mode execution unit cancels the hill-climbing mode when the operation state detection device detects a neutral position of the traveling operation member or when a failure occurs in the transmission while the hill-climbing mode is being executed. It is characterized by
In addition , the transmission device for a work vehicle of the present invention connects a variable displacement hydraulic motor to the running wheels, which has characteristics of decreasing the rotational speed and increasing the driving force as the tilting angle increases, and the power source is In a transmission device for a work vehicle that supplies hydraulic oil from a hydraulic pump driven by a hydraulic motor to the hydraulic motor and controls the rotational speed of the running wheels according to a tilting angle of the hydraulic motor, the transmission is operated by an operator. an operation state detection device that detects the operation state of the operation member; a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed; a normal mode execution unit that executes a normal mode that sets a target vehicle speed and feedback-controls a tilting angle of the hydraulic motor based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device; a running load determination unit that determines a running load to be increased and makes a running load increase determination when the running load increases; and a running load determination unit that determines a running load increase while the normal mode execution unit is executing the normal mode. a hill-climbing mode execution unit that executes a hill-climbing mode that controls the tilting angle of the hydraulic motor to an increasing side compared to the tilting angle based on the control of the normal mode execution unit when the hydraulic motor is lowered; The working vehicle has a front running wheel and a rear running wheel driven by the hydraulic motor, and the hill-climbing mode execution unit controls a tilt angle of the hydraulic motor that drives the running wheels located in the traveling direction of the working vehicle. The present invention is characterized in that the tilting angle of the hydraulic motor that drives the running wheels located in the opposite direction of travel is rapidly increased.
In addition, the transmission device for a work vehicle of the present invention connects a variable displacement hydraulic motor to the running wheels, which has the characteristic of reducing the rotational speed and increasing the driving force as the tilting angle increases. A traveling operation operated by an operator in a transmission of a work vehicle that supplies hydraulic oil from a driven hydraulic pump to the hydraulic motor and controls the rotational speed of the traveling wheels according to a tilt angle of the hydraulic motor. an operation state detection device that detects the operation state of the member; a vehicle speed detection device that detects the traveling speed of the work vehicle as the actual vehicle speed; a normal mode execution unit that executes a normal mode that sets a vehicle speed and feedback-controls a tilting angle of the hydraulic motor based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device; a running load determination unit that determines a running load and makes a running load increase determination when the running load increases; and a running load determination unit that determines a running load increase while the normal mode execution unit is executing the normal mode. further comprising: a hill-climbing mode execution unit that executes a hill-climbing mode that controls the tilting angle of the hydraulic motor to be increased when the hydraulic motor is lowered compared to the tilting angle based on the control of the normal mode execution unit; The traveling load determination unit calculates a decrease in the actual vehicle speed detected by the vehicle speed detection device with respect to the predicted vehicle speed calculated by the predicted vehicle speed calculation unit, and the decrease is greater than or equal to a preset hill-climbing mode switching determination value. The feature is that a running load increase determination is made when

According to the transmission device for a work vehicle of the present invention, it is possible to reduce the burden on the operator by automatically shifting the transmission device, and the vehicle can run without becoming unable to travel even under driving conditions where the traveling load acting on the hydraulic motor increases. can be continued.

It is a side view showing the vibration roller for earthworks of an embodiment. FIG. 2 is a hydraulic circuit diagram showing a schematic configuration of a portion of an HST circuit related to a transmission. FIG. 3 is a characteristic diagram showing the relationship between the tilt angle of the hydraulic pump and the amount of hydraulic oil discharged. FIG. 3 is a characteristic diagram showing the relationship between the tilt angle, rotation speed, and driving force of a hydraulic motor. It is a complaint correspondence diagram which shows the function of a controller. 2 is a flowchart showing a hydraulic motor tilt angle control routine executed by a controller. 3 is a flowchart showing a hill climbing mode control routine executed by the controller. It is a figure which shows the control map for calculating a restriction|limiting ratio from the oil pressure of an HST circuit. 5 is a time chart showing the control status of the tilt angle of the hydraulic motor when the vehicle starts and enters an uphill road from a flat road.

Hereinafter, an embodiment in which the present invention is embodied in a transmission device for a vibration roller for earthworks will be described.
FIG. 1 is a side view showing a vibration roller for earthworks according to the present embodiment, and in the following description, the front-rear direction and left-right direction will be expressed with the vehicle as a reference.
The earthwork vibratory roller 1 is a type of compaction vehicle, and is mainly used for compacting the ground before asphalt is applied. The body of an earthwork vibrating roller 1 (hereinafter also referred to as a vehicle) is formed by connecting a front body 2 and a rear body 3 via an articulating mechanism 4. The front vehicle body 2 includes a metal drum as a front rolling wheel 5 (front running wheel), and the rear vehicle body 3 includes a rubber tire as a rear rolling wheel 6 (rear running wheel). An HST powered by an engine is mounted in a machine room 7 provided in the rear body 3, and the front and rear rolling wheels 5 and 6 are rotationally driven by a hydraulic motor for traveling of the HST, which will be described in detail later. The vehicle 1 travels while compacting the road surface.

Further, the articulating mechanism 4 is driven by the hydraulic cylinder, and the front and rear vehicle bodies 2 and 3 are bent in the horizontal direction to steer the vehicle 1. A cabin 8 is provided in front of the machine room 7 of the rear vehicle body 3, and an operator in the cabin 8 is seated in a driver's seat 9, and a steering wheel 11 and a forward/reverse lever 12 (travel control member) provided on an operation console 10 are provided. Accordingly, a driving operation for driving the vehicle 1 and a work operation for carrying out compaction work are performed.

FIG. 2 is a hydraulic circuit diagram showing a schematic configuration of a portion of the HST circuit related to the transmission. Various hydraulic pumps, such as a variable capacity traveling hydraulic pump 15 (hereinafter simply referred to as hydraulic pump) and a charging hydraulic pump (not shown), are connected to the output shaft of the engine 14 of the HST, and each is rotationally driven by the engine 14. and discharges hydraulic oil. A pair of servo cylinders 15a and 15b of the hydraulic pump 15 are connected to a control valve 16 for controlling the tilt angle, and the control valve 16 is supplied with hydraulic oil from the charging hydraulic pump whose pressure is regulated by a relief valve 17. There is. According to the switching of the control valve 16, hydraulic oil is supplied to each servo cylinder 15a, 15b, the tilting angle of the hydraulic pump 15 increases or decreases, and the direction and amount of hydraulic oil discharged from the pair of ports is controlled. . A pair of ports of the hydraulic pump 15 are connected via a relief pipe 18, and the discharge pressure of the hydraulic pump 15 is limited to the set pressure of a pair of relief valves 19, 20 installed in the relief pipe 18 as an upper limit. This protects the HST circuit from excessive oil pressure.

One port of the hydraulic pump 15 is connected to one port of a pair of variable capacity traveling hydraulic motors 23 and 24 (hereinafter simply referred to as hydraulic motors) connected to the front and rear rolling wheels 5 and 6. They are connected via an advancement conduit 21. The other port of the hydraulic pump 15 is connected to the other port of each hydraulic motor 23, 24 via a reverse conduit 22. When hydraulic oil is discharged from one port of the hydraulic pump 15, the hydraulic oil is supplied to each hydraulic motor 23, 24 via a forward line 21, and then to each hydraulic pump 15 via a reverse line 22. This causes the front and rear rolling wheels 5, 6 to rotate in the forward direction. Further, when the hydraulic oil is discharged from the other port of the hydraulic pump 15, the hydraulic oil flows in the order of the reverse conduit 22, each hydraulic motor 23, 24, and the forward conduit 21, contrary to the above, and The front and rear rolling wheels 5 and 6 are each rotationally driven in the backward direction. As shown in the characteristic diagram of FIG. 3, the hydraulic pump 15 has a characteristic that the discharge amount of hydraulic oil (rotational speed of the rolling press) increases as the tilt angle increases from 0 to the maximum value. .

Servo cylinders 23a, 24a are connected to each hydraulic motor 23, 24, and each servo cylinder 23a, 24a is connected to control valves 25, 26 for controlling a tilt angle, respectively. Hydraulic oil from the charging hydraulic pump is supplied to each servo cylinder 23a, 24a according to the switching of the control valves 25, 26, and the tilting angle of each hydraulic motor 23, 24 increases or decreases, thereby changing the rotation speed and driving force. controlled. As shown in the characteristic diagram of FIG. 4, the hydraulic motors 23 and 24 have characteristics that increase the rotational speed and decrease the driving force as the tilt angle decreases from the initial value corresponding to the maximum value to the minimum value. have.

Parking brakes 27 and 28 are connected to each hydraulic motor 23 and 24, and each parking brake 27 and 28 is connected to a common brake release valve 29. During normal operation, the parking brakes 27 and 28 are kept in an operating state, and a braking force is applied to the vehicle 1 by regulating the rotation of the hydraulic motors 23 and 24. When the vehicle 1 starts traveling, the brake release valve 29 is opened, hydraulic oil from the charging hydraulic pump is supplied to each parking brake 27, 28, and the braking of the vehicle 1 is released. Note that flushing valves 30 and 31 are connected in parallel to each of the hydraulic motors 23 and 24, and the hydraulic oil in the HST circuit is replaced as appropriate.

The controller 32 that controls the transmission includes an input/output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs, control maps, etc., a central processing unit (CPU), a timer counter, and the like. On the input side of the controller 32, there is an operation state detection device 13 that detects the operation direction and operation amount (hereinafter collectively referred to as the operation state) of the forward/reverse lever 12, and a hydraulic pump 15 that supplies signals to the respective hydraulic motors 23 and 24. Hydraulic pressure sensors 39 and 40 (hydraulic pressure detection devices) for detecting hydraulic oil pressures Pf and Pr (hereinafter referred to as HST circuit oil pressures) are provided on the front and rear rolling wheels 5 and 6, respectively, and are installed in the vehicle 1. Various sensors such as vehicle speed sensors 34 and 35 (vehicle speed detection devices) that detect vehicle speeds Vf and Vr as running speeds of the vehicle are connected, and respective detection information is input.

Further, on the output side of the controller 32, there are various types of pump electromagnetic proportional valves 36 for controlling the tilting angle of the hydraulic pump 15, motor electromagnetic proportional valves 37 and 38 for controlling the tilting angles of the front and rear hydraulic motors 23 and 24, etc. Devices are connected. A control signal is input from the controller 32 to each electromagnetic proportional valve 36 to 38, and based on the pilot pressure output from each electromagnetic proportional valve 36 to 38, the tilting angle of the hydraulic pump 15 and hydraulic motors 23 and 24 is adjusted as described above. is controlled.

FIG. 5 is a complaint diagram showing the functions of the controller 32, and the controller 32 includes a normal mode execution section 32a, a hill climbing mode execution section 32b, a running load determination section 32c, and a lower limit restriction section 32d. The normal mode execution unit 32a calculates the tilting angles pθ, mθ of the hydraulic pump 15 and the hydraulic motors 23, 24 based on the operating state of the forward/reverse lever 12, and sends control signals corresponding to the tilting angles pθ, mθ to each electromagnetic Output to proportional valves 36-38.

Regarding the hydraulic motors 23 and 24, the tilting angle mθ is controlled by vehicle speed feedock control, thereby automatically shifting the HST. For example, based on a preset control map (not shown), a target vehicle speed Vtgt for forward or reverse travel is set based on the operation state of the forward/reverse lever 12, and this target vehicle speed Vtgt and the actual vehicle speed detected by the vehicle speed sensors 34 and 35 are set. The tilt angle mθ of each hydraulic motor 23, 24 is calculated by PID control or the like based on V (for example, the average value of Vf and Vr) (hereinafter, the tilt angle control at this time will be referred to as a normal mode).

For example, when the running vehicle 1 enters an uphill road and the running load increases, the running load determination unit 32c makes a running load increase determination, and outputs the determination result to the uphill mode execution unit 32b. In this embodiment, the oil pressures Pf and Pr detected by the oil pressure sensors 39 and 40 are selectively used as the running load depending on whether the vehicle 1 moves forward or backward. Specifically, during forward movement, the oil pressure Pf detected by the oil pressure sensor 39 in the forward movement conduit 21 is used, and during reverse movement, the oil pressure Pr detected by the oil pressure sensor 40 in the reverse movement line 22 is used. When these oil pressures Pf and Pr continue to be higher than a preset climbing mode switching judgment pressure P1 for a climbing mode switching judgment time T1, it is assumed that the running load has increased, and a running load increase judgment is made.

When the running load increase determination is input from the running load determining unit 32c, the climbing mode execution unit 32b determines the tilting angle of the hydraulic motors 23 and 24 by comparing it with the tilting angle mθ based on the control of the normal mode execution unit 32a. Control mθ to the increasing side. The details will be described later, but the control to the increasing side at this time is to set the limit ratios Rf, Rr (lower limit value) in the range of 0 to 100% to limit the lower limit of the tilting angle mθ according to the oil pressures Pf, Pr. It is calculated within and output to the lower limit limit section 32d. The lower limit limiter 32d limits the tilting angle mθ of the hydraulic motors 23, 24 input from the normal mode execution unit 32a based on the restriction ratios Rf, Rr input from the hill climbing mode execution unit 32b. As a result, the tilting angle mθ is corrected to a value on the increasing side, and a control signal corresponding to the corrected tilting angle mθ is output to each motor electromagnetic proportional valve 37, 38 (hereinafter, the tilting angle at this time is (This control is called climbing mode).

FIG. 6 is a flowchart showing a tilt angle control routine for the hydraulic motors 23 and 24 executed by the controller 32, and is executed at predetermined control intervals when the vehicle 1 is powered on.
First, in step 1, it is determined whether the vehicle 1 is currently running based on the detection information from the vehicle speed sensors 34, 35, and if the determination is No (negative), the routine is temporarily terminated. When the determination in step 1 is Yes (affirmative), the process moves to step 2, and the oil pressure Pf, Pr of the HST circuit detected by the oil pressure sensors 39, 40 (either one depending on the forward or backward movement, and the following explanation is the same) ) is equal to or higher than a preset uphill mode switching determination pressure P1, and in the subsequent step 3, it is determined whether or not a preset uphill mode switching determination time T1 has elapsed (running load determination section ). That is, it is determined whether the state in which the oil pressures Pf and Pr of the HST circuit are equal to or higher than the climbing mode switching judgment pressure P1 continues for the climbing mode switching judgment time T1, and if these conditions are not met, the process moves to step 4. and executes normal mode (normal mode execution part). Therefore, in this case, the tilt angle mθ of the hydraulic motors 23 and 24 is controlled by vehicle speed feedback control, and the actual vehicle speed V is maintained at the target vehicle speed Vtgt.

Further, if the conditions of steps 2 and 3 are both satisfied, the process moves to step 5. It can be inferred that the vehicle 1 at this time is running on an uphill road, and the running load acting on the hydraulic motors 23 and 24 increases, and the actual vehicle speed V gradually decreases. In such a situation, if vehicle speed feedback in the normal mode is continued, the tilt angle mθ of the hydraulic motors 23 and 24 will be controlled in a downward direction based on the characteristics shown in FIG. 4 in order to maintain the target vehicle speed Vtgt (rotational speed). Therefore, the actual vehicle speed V actually decreases due to a decrease in the driving force.

The condition of step 2 may be satisfied even when driving on a flat road, for example, when the forward/reverse lever 12 is returned to the neutral position (=0) and so-called HST braking occurs, or when the vehicle 1 starts moving. However, these situations will end in a very short time. Therefore, a condition regarding the hill-climbing mode switching determination time T1 in step 3 is added, thereby making it possible to accurately determine only the situation in which the running load has increased, which requires switching to the hill-climbing mode.

Inappropriate tilt angle control in the normal mode as described above is prevented by the hill climbing mode executed in step 5.
When the controller 32 moves to step 5, it executes the uphill mode control routine shown in FIG. 7 (uphill mode execution section). First, in step 21, the detection information of the oil pressure sensors 39, 40 is taken in, and in the subsequent step 22, limit ratios Rf, Rr corresponding to the oil pressures Pf, Pr are calculated based on the control map shown in FIG. The restriction ratios Rf and Rr are individually set by the front and rear hydraulic motors 23 and 24, and in the region below the above-mentioned hill-climbing mode switching judgment pressure P1, both are set to 0%, which corresponds to no restriction on the tilting angle mθ, and the slope-climbing When the mode switching determination pressure P1 is exceeded, it increases at a predetermined rate of increase.

At this time, the rate of increase is greater in the restriction ratio Rr (indicated by a broken line) of the rear hydraulic motor 24 than in the restriction ratio Rf (indicated by a solid line) of the front hydraulic motor 23. Therefore, as the oil pressures Pf and Pr increase, the restriction ratio Rr of the rear hydraulic motor 24 reaches 100%, which corresponds to the maximum restriction at the oil pressure Px, and the restriction ratio of the front hydraulic motor 23 reaches the higher oil pressure Py. (>Px), it reaches 100% and thereafter remains at 100% regardless of the increase in oil pressure. In this way, the limit ratios Rf and Rr are set to the side where the tilting angle mθ increases as the excess of the hydraulic pressure with respect to the hill-climbing mode switching determination pressure P1 becomes larger.

In the following step 23, the tilt angle mθ is calculated based on the vehicle speed feedback. This process is similar to that executed in the normal control mode in step 3, and the tilt angle mθ is calculated by PID control or the like based on the target vehicle speed Vtgt and the actual vehicle speed V. Thereafter, the process moves to step 24, where the tilting angle mθ is limited based on the limiting ratios Rf and Rr. For example, if the restriction ratios Rf and Rr are calculated in step 22 and mθ1 is calculated as the tilting angle mθ in step 23, the tilting angle mθ of the front hydraulic motor 23 is limited based on the control map in FIG. The tilt angle mθ of the rear hydraulic motor 24 is limited to a tilt angle corresponding to the limit ratio Rr. As long as the oil pressure increases, the limiting ratios Rf and Rr are also set to the increasing side, and the tilting angle mθ of each hydraulic motor 23, 24 continues to be corrected to the increasing side, and is balanced at the tilting angle mθ determined from the slope of the uphill road, etc. do.

After executing the above process of FIG. 7, the controller 32 moves from step 5 to step 6 of FIG. In step 6, it is determined whether the forward/reverse lever 12 has been returned to the neutral position, and in the following step 7, it is determined whether or not a failure has occurred in the transmission, and if any of the determinations is Yes, the process moves to step 4. do. The processes in steps 6 and 7 are both based on the assumption that the continuation of the uphill mode is undesirable. When the forward/reverse lever 12 is returned to the neutral position, a so-called HST brake is applied to the vehicle 1, but the hydraulic motors 23 and 24, which are controlled to increase the tilt angle mθ, exert a greater control than in the normal mode. This generates power, resulting in sudden braking that is not intended by the operator. Further, a failure in the transmission means that normal driving cannot be expected, and it is desirable to cancel the irregular hill-climbing mode in which the tilting angle mθ is controlled to the increasing side. By returning to normal mode, these unexpected situations can be prevented.

When the determination is No in both steps 6 and 7, it is determined in step 8 whether or not the hydraulic pressure Pf, Pr of the HST circuit is less than the preset normal mode return determination pressure P2, and in the following step 9, the determination is made in advance. It is determined whether the set normal mode return determination time T2 has elapsed. That is, it is determined whether the state in which the oil pressures Pf and Pr of the HST circuit are less than the normal mode return judgment pressure P2 continues for the normal mode return judgment time T2, and if these conditions are met, the process proceeds to step 4. and return to normal mode (normal mode execution section). Further, if the conditions of steps 8 and 9 are not satisfied, the process moves to step 10.

The purpose of step 8 is to determine, for example, a situation in which the vehicle 1 has finished climbing an uphill road and there is no longer a need to continue the uphill mode due to a drop in oil pressure in the HST circuit. The condition of step 8 may be satisfied even with the oil pressure fluctuation. However, since such oil pressure fluctuations end in a very short time, adding the condition regarding the normal mode return determination time T2 in step 9 prevents inappropriate return to normal mode due to oil pressure fluctuations while driving. can be prevented.

In step 10, the rotational speed difference ΔN between the front rolling wheel 5 and the rear rolling wheel 6 is calculated based on the vehicle speeds Vf and Vr detected by the front and rear vehicle speed sensors 34 and 35, and the rotational speed difference ΔN is set in advance. It is determined whether or not the rotation difference determination value ΔN0 is greater than or equal to the determined rotation difference determination value ΔN0. When the determination is Yes, it is assumed that either the front or rear rolling wheels 5, 6 are slipping, and the process moves to step 11 to switch from the hill-climbing mode to the traction mode. The control contents of the traction mode are well known and will not be explained in detail, but the tilting angles mθ of the hydraulic motors 23 and 24 that drive the rolling wheels 5 and 6 on the slip side, which have high rotational speeds, are controlled to the slip suppression side. to recover grip.
Also, when the determination in step 10 is No, the process returns to step 5, repeats the processes in steps 5 to 10, and continues the climbing mode, and returns to normal mode when any of the conditions in steps 6 to 9 are met. .

Next, the control status of the tilting angle mθ of the hydraulic motors 23 and 24 based on the above processing of the controller 32 will be explained.
FIG. 9 is a time chart showing the control status of the tilt angle mθ of the hydraulic motors 23 and 24 when the vehicle 1 starts in the forward direction and enters an uphill road from a flat road.
When the forward/reverse lever 12 is operated in the forward direction, the target vehicle speed Vtgt is set corresponding to the amount of operation, and the tilting angle mθ of the hydraulic pump 15 is first controlled in an increasing direction from 0 to reach the maximum value. (Point b). Along with this, the hydraulic pump 15 starts discharging hydraulic oil, the hydraulic pressure Pf of the HST circuit increases, and the hydraulic motors 23 and 24, which are maintained at the initial value of the tilting angle mθ, are driven, thereby reducing the actual vehicle speed V to 0. It gradually increases from At a timing (point a) just before the tilting angle mθ of the hydraulic pump 15 reaches the maximum value, the tilting angle mθ of the hydraulic motors 23 and 24 starts to be controlled in a downward direction from the initial value based on the normal mode. Based on the characteristics shown in FIG. 4, the rotational speeds of the hydraulic motors 23 and 24 increase, and the actual vehicle speed V gradually increases accordingly and reaches the target vehicle speed Vtgt (point c).

When the amount of operation of the forward/reverse lever 12 increases or decreases, a corresponding target vehicle speed Vtgt is set, and the tilt angle mθ of the hydraulic motors 23, 24 is controlled so as to achieve the target vehicle speed Vtgt by vehicle speed feedback. Note that even when the forward/reverse lever 12 is operated to the reverse side, the tilt angle mθ is similarly controlled by simply reversing the rotation direction of the hydraulic motors 23, 24.

As described above, in the normal mode, the target vehicle speed Vtgt is set according to the operating state of the forward/reverse lever 12, and the tilting angle mθ of the hydraulic motors 23 and 24 of the HST is controlled based on the target vehicle speed Vtgt. has been realized. Therefore, the vehicle 1 can always be driven at an appropriate actual vehicle speed V according to the operating state of the forward/reverse lever 12 without requiring manual gear shifting operations by the operator. During compaction work, the operator needs to carry out work operations to carry out the compaction work in parallel with driving operations for moving the vehicle 1, but it is possible to reduce the burden on such operators and also Inappropriate gear shifting operations can be prevented.

On the other hand, when the vehicle 1 enters an uphill road from a flat road, the running load acting on the hydraulic motors 23 and 24 increases and the actual vehicle speed V decreases. Although the tilting angle mθ of 24 is controlled in a decreasing direction, a decrease in vehicle speed cannot be suppressed because the driving force decreases based on the characteristics shown in FIG. At this time, as the running load acting on the hydraulic motors 23 and 24 increases, the hydraulic pressure Pf of the HST circuit begins to increase (point d), and if the normal mode continues, the hydraulic pressure will increase as shown by the broken line in the figure. When Pf reaches the set pressure of the relief valves 19, 20, the relief valves 19, 20 are opened, the hydraulic motors 23, 24 are stopped, and the vehicle 1 becomes unable to travel.

In this embodiment, when the increasing oil pressure Pf reaches the climbing mode switching determination pressure P1 (point e) and this state continues for the climbing mode switching determination time T1 (point f), the normal mode is switched to the climbing mode. . Then, the tilting angle mθ of each hydraulic motor 23, 24 is limited based on the restriction ratios Rf, Rr calculated from the control map of FIG. 8, and thereby each is corrected to the increasing side. Such restrictions on the tilting angles mθ are sequentially executed in response to changes in the oil pressure Pf, and as a result, each tilting angle mθ is gradually controlled in an increasing direction (point g). At this time, the tilting angle mθ is increased more rapidly in the rear hydraulic motor 24 than in the front hydraulic motor 23, based on the magnitude relationship of the restriction ratios Rf and Rr based on FIG. Due to such an increase in the tilting angle mθ, the driving force of the hydraulic motors 23 and 24 gradually increases based on the characteristics shown in FIG. Vtgt is reached (point h).

In this example, the actual vehicle speed V has recovered to the target vehicle speed Vtgt, but since the rotational speed of the hydraulic motors 23 and 24 decreases as the driving force increases, the speed may vary depending on various conditions such as the target vehicle speed Vtgt and the slope of the uphill road. may not recover to the target vehicle speed Vtgt. However, even in that case, the relief valves 19 and 20 do not open because the hydraulic pressure increase in the HST circuit is suppressed by the tilt angle control in the increasing direction, and the hydraulic motors 23 and 24 stop due to this. This allows the vehicle 1 to continue traveling by preventing this.

As described above, in the uphill mode executed on an uphill road, the tilting angle mθ of the hydraulic motors 23 and 24, which is set in the same way as in the normal mode, is determined by the limiting ratios Rf and Rr set from the hydraulic pressures Pf and Pr of the HST circuit. By restricting it, it is compensated for the increase. Therefore, since the driving force of the hydraulic motors 23 and 24 increases based on the characteristics shown in FIG. 4, the actual vehicle speed V that has decreased due to running on an uphill road can be recovered to the target vehicle speed Vtgt, and the target vehicle speed cannot be recovered to the target vehicle speed Vtgt. Even if there is no vehicle, the vehicle 1 can continue to run and climb the uphill road.

In addition, in this embodiment, the greater the excess of the oil pressures Pf, Pr with respect to the hill-climbing mode switching determination pressure P1, the greater the limit ratios Rf, Rr are set to the increasing side of the tilting angle mθ, and the slope-climbing mode is started. Then, each restriction ratio Rf, Rr is set from 0 in an increasing direction as the oil pressures Pf, Pr increase. The tilting angle mθ is based on the vehicle speed feedback similar to the normal mode, and the tilting angle mθ is limited by the limiting ratios Rf and Rr, so each tilting angle mθ is set from the normal mode value as the starting point. It will be set in an increasing direction. As a result, when switching from normal mode to hill-climbing mode, each tilt angle mθ changes smoothly to the increasing side without any steps, and the actual vehicle speed V inevitably changes smoothly (at point f in Fig. 9). time).

At this time, the vehicle 1 may be compacting the uphill road by traveling at a constant speed, and if the actual vehicle speed V fluctuates stepwise, the road surface being compacted becomes rough and repair work is required. This kind of situation can be prevented by the above-mentioned mode switching, and there is also an advantage that the compaction work can be made more efficient.

In addition, when switching from normal mode to hill-climbing mode, the tilting angle mθ of the rear hydraulic motor 24 is rapidly increased compared to the tilting angle mθ of the front hydraulic motor 23, which inevitably causes the front The driving force of the rear rolling wheel 6 increases more rapidly than the driving force of the rolling wheel 5. The center of gravity of the vehicle 1 moves rearward as it enters the uphill road, and the grip of the front rolling wheel 5 decreases and the grip of the rear rolling wheel 6 increases. The rear compaction wheels 6 made of rubber tires inherently have higher grip than the front compaction wheels 5. In response to this disparity in grip, the driving force of the front and rear rolling wheels 5, 6 increases, so the driving force of each rolling wheel 5, 6 can be transmitted to the road surface without waste while suppressing slips, resulting in stable It is possible to realize driving on steep slopes.

Note that when the vehicle 1 is moving backward, the moving direction of the center of gravity when the vehicle 1 enters the uphill road is reversed from when moving forward. Therefore, a control map is prepared in which the magnitude relationship of the restriction ratios Rf and Rr is reversed from that in FIG. 8, and in the hill climbing mode in reverse, the rear hydraulic motor is The tilting angle mθ of the hydraulic motor 23 on the front side of the hydraulic motor 24 may be suddenly increased.
That is, the tilt angle of the hydraulic motors 23 and 24 that drive the rolling wheels 5 and 6 that are located in the opposite direction of travel of the vehicle 1 is greater than the tilt angle of the hydraulic motors 23 and 24 that drive the rolling wheels 5 and 6 that are located in the direction of travel of the vehicle 1. It is only necessary to rapidly increase the tilt angle of 24, thereby making it possible to appropriately increase the driving force both when moving forward and when moving backward.

Incidentally, in the present embodiment, the situation in which the running load of the hydraulic motors 23 and 24 has increased due to entry into an uphill road is determined based on the hydraulic pressures Pf and Pr of the HST circuit, but the present invention is not limited to this, and for example, it can be determined based on a change in vehicle speed. You may judge. Specifically, as shown in FIG. 5, a predicted vehicle speed calculation unit 32e is added to the controller 32, and the actual vehicle speed V of the vehicle 1 to be achieved is calculated as the predicted vehicle speed based on the current tilt angle mθ of the hydraulic motors 23 and 24. and outputs the calculation result to the traveling load determination section 32c (predicted vehicle speed calculation section).

This predicted vehicle speed corresponds to the actual vehicle speed V while traveling on a flat road or the actual vehicle speed V when not towing another vehicle, etc. In these traveling conditions, the predicted vehicle speed is different from the actual vehicle speed V detected by the vehicle speed sensors 34 and 35. Approximately matching predicted vehicle speeds are calculated. For example, when the vehicle 1 enters an uphill road, the actual vehicle speed V decreases, and the amount of decrease in the actual vehicle speed V relative to the predicted vehicle speed gradually increases. Therefore, when the amount of decrease exceeds a preset slope-climbing mode switching determination value, a determination may be made to increase the running load and switching to the slope-climbing mode may be made.

This concludes the description of the embodiment, but aspects of the present invention are not limited to this embodiment. For example, in the above embodiment, the transmission device is used for the vibrating roller 1 for earthworks, but the present invention is not limited to this as long as it is a working vehicle that runs by driving a hydraulic motor using an HST. For example, it may be embodied as a transmission device for tire rollers or vibrating rollers, or a transmission device for a wheel loader.
Further, in the above embodiment, the front and rear rolling wheels 5 and 6 are driven by the hydraulic motors 23 and 24, respectively, but the invention is not limited to this, and can be applied to, for example, a work vehicle that drives one of the running wheels. You may.

Furthermore, in the hill-climbing mode of the above embodiment, the tilting angle mθ of the hydraulic motors 23 and 24, which is set in the same way as in the normal mode, is limited by the limiting ratios Rf and Rr set from the hydraulic pressures Pf and Pr of the HST circuit. Although the correction is made to the following, it is not limited to this. For example, when switching from normal mode to hill-climbing mode, vehicle speed feedback is stopped, the tilting angle mθ is set in the increasing direction in accordance with the increase in the hydraulic pressures Pf and Pr of the HST circuit, and the hydraulic pressure is set based on the tilting angle mθ. The motors 23 and 24 may be controlled in a feedforward manner. Even in this case, the driving force of the hydraulic motors 23 and 24 increases based on the characteristics shown in FIG. 4, so that the vehicle 1 can continue to travel.
Furthermore, in the above embodiment, a situation in which the running load acting on the hydraulic motors 23 and 24 increases is described as running on an uphill road, but the present invention is not limited to this. For example, the hill-climbing mode may be executed when the vehicle is towing another vehicle, and the same effects as in the above embodiment can be obtained in this case as well.

1 Vibrating roller for earthworks (work vehicle)
5 Front rolling wheel (front running wheel)
6 Rear rolling wheel (rear running wheel)
12 Forward/backward lever (traveling operation member)
13 Operation state detection device 14 Engine (power source)
15 Hydraulic pump 23, 24 Hydraulic motor 34, 35 Vehicle speed sensor (vehicle speed detection device)
32a Normal mode execution section 32b Uphill mode execution section 32c Running load determination section 32d Lower limit restriction section 32e Predicted vehicle speed calculation section 39, 40 Oil pressure sensor (oil pressure detection device)

Claims (7)

A variable capacity hydraulic motor that has the characteristic of decreasing the rotational speed and increasing the driving force as the tilting angle increases is connected to the running wheels, and hydraulic oil from a hydraulic pump driven by a power source is supplied to the hydraulic A transmission device for a work vehicle that supplies power to a motor and controls the rotation speed of the running wheels according to a tilt angle of the hydraulic motor,
an operation state detection device that detects an operation state of a traveling operation member operated by an operator;
a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed;
A target vehicle speed is set according to the operation state of the traveling operation member detected by the operation state detection device, and a tilting angle of the hydraulic motor is determined based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device. a normal mode execution unit that executes a normal mode that performs feedback control;
a running load determination unit that determines a running load acting on the hydraulic motor and makes a running load increase determination when the running load increases;
During execution of the normal mode by the normal mode execution unit, when the running load determination unit determines that the running load has increased, the tilt angle of the hydraulic motor is greater than the tilt angle based on the control of the normal mode execution unit. a climbing mode execution unit that executes a climbing mode that controls the tilting angle to an increasing side;
further comprising a hydraulic pressure detection device that detects the hydraulic pressure of hydraulic oil supplied from the hydraulic pump to the hydraulic motor,
The traveling load determination unit determines that the traveling load has increased when the oil pressure detected by the oil pressure detection device continues to be at or above a preset uphill mode switching determination pressure for a preset uphill mode switching determination time. death,
The hill-climbing mode execution unit controls the tilting angle to an increasing side as the excess of the oil pressure detected by the oil pressure detection device with respect to the hill-climbing mode switching determination pressure is larger.
A transmission device for a work vehicle characterized by: further comprising a lower limit limiting section that limits the tilt angle based on the control of the normal mode execution section by a lower limit value,
The hill-climbing mode execution unit sets the lower limit value to an increasing side as the excess of the oil pressure detected by the oil pressure detection device with respect to the hill-climbing mode switching determination pressure is larger, and the lower limit limiter sets the lower limit value to an increasing side based on the lower limit value. 2. The transmission device for a work vehicle according to claim 1, wherein the tilting angle of the hydraulic motor is controlled to increase by limiting the tilting angle of the hydraulic motor. The hill -climbing mode executing unit is configured to maintain a state in which the oil pressure detected by the oil pressure detection device is less than a preset normal mode return judgment pressure for a preset normal mode return judgment time during execution of the hill-climbing mode. 2. The transmission device for a work vehicle according to claim 1 , wherein the transmission device for a work vehicle cancels the uphill mode when the uphill mode occurs. A variable capacity hydraulic motor that has the characteristic of decreasing the rotational speed and increasing the driving force as the tilting angle increases is connected to the running wheels, and hydraulic oil from a hydraulic pump driven by a power source is supplied to the hydraulic A transmission device for a work vehicle that supplies power to a motor and controls the rotation speed of the running wheels according to a tilt angle of the hydraulic motor,
an operation state detection device that detects an operation state of a traveling operation member operated by an operator;
a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed;
A target vehicle speed is set according to the operation state of the traveling operation member detected by the operation state detection device, and a tilting angle of the hydraulic motor is determined based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device. a normal mode execution unit that executes a normal mode that performs feedback control;
a running load determination unit that determines a running load acting on the hydraulic motor and makes a running load increase determination when the running load increases;
During execution of the normal mode by the normal mode execution unit, when the running load determination unit determines that the running load has increased, the tilt angle of the hydraulic motor is greater than the tilt angle based on the control of the normal mode execution unit. a climbing mode execution unit that executes a climbing mode that controls the tilting angle to an increasing side;
The hill-climbing mode execution unit is configured to cancel the hill-climbing mode when the operation state detection device detects a neutral position of the traveling operation member or when a failure occurs in the transmission while the hill-climbing mode is being executed. A transmission device for a work vehicle characterized by: The work vehicle has front running wheels and rear running wheels each driven by the hydraulic motor,
The hill-climbing mode execution unit calculates a rotational speed difference between the front running wheels and the rear running wheels from the actual vehicle speed detected by the vehicle speed detection device during execution of the hill-climbing mode, and calculates the rotational speed difference between the front running wheels and the rear running wheels. The transmission device for a work vehicle according to claim 1 , wherein when the rotation difference determination value is equal to or greater than a preset rotation difference determination value, the uphill mode is stopped and the transmission mode is switched to a traction mode for suppressing slippage. A variable capacity hydraulic motor that has the characteristic of decreasing the rotational speed and increasing the driving force as the tilting angle increases is connected to the running wheels, and hydraulic oil from a hydraulic pump driven by a power source is supplied to the hydraulic A transmission device for a work vehicle that supplies power to a motor and controls the rotation speed of the running wheels according to a tilt angle of the hydraulic motor,
an operation state detection device that detects an operation state of a traveling operation member operated by an operator;
a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed;
A target vehicle speed is set according to the operation state of the traveling operation member detected by the operation state detection device, and a tilting angle of the hydraulic motor is determined based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device. a normal mode execution unit that executes a normal mode that performs feedback control;
a running load determination unit that determines a running load acting on the hydraulic motor and makes a running load increase determination when the running load increases;
During execution of the normal mode by the normal mode execution unit, when the running load determination unit determines that the running load has increased, the tilt angle of the hydraulic motor is greater than the tilt angle based on the control of the normal mode execution unit. a climbing mode execution unit that executes a climbing mode that controls the tilting angle to an increasing side;
The work vehicle has front running wheels and rear running wheels each driven by the hydraulic motor,
The hill-climbing mode execution unit is configured to set a tilting angle of a hydraulic motor that drives the running wheels located in a counter-progressive direction to a tilting angle of a hydraulic motor that drives the running wheels located in a direction opposite to the traveling direction of the work vehicle. A transmission device for a work vehicle characterized by a rapid increase in speed. A variable capacity hydraulic motor that has the characteristic of decreasing the rotational speed and increasing the driving force as the tilting angle increases is connected to the running wheels, and hydraulic oil from a hydraulic pump driven by a power source is supplied to the hydraulic A transmission device for a work vehicle that supplies power to a motor and controls the rotation speed of the running wheels according to a tilt angle of the hydraulic motor,
an operation state detection device that detects an operation state of a traveling operation member operated by an operator;
a vehicle speed detection device that detects the traveling speed of the work vehicle as an actual vehicle speed;
A target vehicle speed is set according to the operation state of the traveling operation member detected by the operation state detection device, and a tilting angle of the hydraulic motor is determined based on the target vehicle speed and the actual vehicle speed detected by the vehicle speed detection device. a normal mode execution unit that executes a normal mode that performs feedback control;
a running load determination unit that determines a running load acting on the hydraulic motor and makes a running load increase determination when the running load increases;
During execution of the normal mode by the normal mode execution unit, when the running load determination unit determines that the running load has increased, the tilt angle of the hydraulic motor is greater than the tilt angle based on the control of the normal mode execution unit. a climbing mode execution unit that executes a climbing mode that controls the tilting angle to an increasing side;
further comprising a predicted vehicle speed calculation unit that calculates a traveling speed of the work vehicle to be achieved by the current tilt angle of the hydraulic motor as a predicted vehicle speed,
The traveling load determination unit calculates a decrease in the actual vehicle speed detected by the vehicle speed detection device with respect to the predicted vehicle speed calculated by the predicted vehicle speed calculation unit, and the decrease is greater than or equal to a preset hill-climbing mode switching determination value. A transmission device for a work vehicle, characterized in that a transmission device for a work vehicle is characterized in that it determines that a running load has increased when

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