JP5493064B2 - Work vehicle - Google Patents

Description

  The present invention relates to a working vehicle in which a control device controls the operation of an electric actuator for HST so that the HST is in an output state corresponding to the operation state of a speed change operation member.

  In a working vehicle in which the HST is inserted in the traveling system transmission path from the driving source to the driving wheel, when the traveling load becomes excessively large, the hydraulic pressure of the pair of HST lines in the HST rises, causing the following inconveniences. .

  That is, the HST includes a hydraulic pump that is operatively connected to a drive source, and a hydraulic motor that is fluidly connected to the hydraulic pump via a pair of HST lines and that outputs rotational power toward the drive wheel. The rotational speed of the rotational power output from the hydraulic motor is changed with respect to the rotational speed of the rotational power input to the hydraulic pump by changing the volume of the hydraulic pump and the hydraulic motor, one of which is a variable displacement type. To get.

  The HST further includes a charge line for supplying pressure oil from an auxiliary pump attached to the work vehicle to the pair of HST lines, and a pair of relief valves respectively acting on the pair of HST lines. When the hydraulic pressure of the high-pressure side line of the pair of HST lines exceeds a predetermined value due to an increase in running load while supplying hydraulic oil to the pair of HST lines via the charge line, the relief The valve is designed to relieve hydraulic fluid.

  When an excessive traveling load is generated in the working vehicle and the hydraulic pressure of the high-pressure side HST line is rapidly increased, the amount of relief oil by the relief valve may exceed the amount of charge oil that can be supplied. In this case, cavitation may occur in the pair of HST lines, leading to a failure of the hydraulic pump and the hydraulic motor.

  Occurrence of the cavitation can be prevented by increasing the amount of charge oil that can be supplied due to an increase in the size of the check valve. A situation may occur where the amount of oil to be relieved exceeds the amount of oil that can be relieved by the relief valve. In this case, the hydraulic pressure on the high pressure side of the pair of HST lines may unduly increase, leading to a failure of the HST.

  For example, in Patent Document 1 below, HST inserted in a traveling system transmission path from a drive source to a drive wheel, a shift operation member that can be manually operated, an operation side sensor that detects an operation state of the shift operation member, An output side sensor comprising: an output side sensor that detects an output state of the HST; an electric actuator for HST that operatively drives the output adjustment member of the HST; and a control device that controls operation of the electric actuator. Estimating the deviation between the actual HST rotation speed detected by the HST and the HST target rotation speed corresponding to the operation state of the speed change operation member as a travel load added to the work vehicle, and the travel load is a predetermined value It is disclosed to warn of an HST abnormality when exceeding.

  The working vehicle described in Patent Document 1 includes the operation side sensor and the output side necessary for controlling the output adjustment member of the HST without providing a dedicated sensor for detecting a traveling load such as a pressure sensor. Although it is useful in that the travel load can be detected only by the sensor, the response when the travel load becomes excessively high only gives a warning, and the transmission including the HST when the travel load becomes excessively high There is room for improvement from the standpoint of preventing the failure.

Japanese Patent No. 3927397

  The present invention has been made in view of the prior art, and in a working vehicle in which the control device controls the operation of the electric actuator for HST so that the HST is in an output state according to the operation state of the speed change operation member, the cost increases. An object of the present invention is to provide a working vehicle that can effectively prevent the transmission including the HST from being damaged by an excessive traveling load while preventing the transmission as much as possible.

  In order to achieve the above object, the present invention can be operated manually by a driving source, HST that operatively inputs rotational power from the driving source, driving wheels that are operatively driven by the output of the HST, and Shift operation member, an HST electric actuator that operatively drives the output adjustment member of the HST, an operation side sensor that detects an operation state of the shift operation member, and an output side sensor that detects the output state of the HST And an input side sensor for detecting the input state of the HST, and a control device for controlling the operation of the HST electric actuator, wherein the control device includes an operation state of the speed change operation member. The control device is provided with a relationship between the actual transmission gear ratio / load torque and a protective torque value for protecting the transmission including the HST for each of a plurality of transmission gear ratios defined by Is calculated from a vehicle speed control mode in which the HST electric actuator is operated with a set speed ratio set based on a signal from the operation side sensor as a target speed ratio, and signals from the input side sensor and the output side sensor. A load control mode that is executed when the load torque value estimated from the actual gear ratio and the relationship between the actual gear ratio / load torque at the current target gear ratio exceeds the protective torque value at the current target gear ratio. In the load control mode, there is provided a working vehicle that operates the electric actuator for HST using a speed ratio lower than the current target speed ratio as a target speed ratio regardless of an operation state of the speed change operation member.

  Preferably, the load control mode includes a first step of operating the electric actuator for HST with a speed ratio that is lower than the target speed ratio at that time by a predetermined speed as a new target speed ratio, the input side sensor, The load torque value estimated from the actual gear ratio calculated based on the signal from the output side sensor and the actual gear ratio / load torque relationship at the newly set current target gear ratio is the current target gear ratio. A second step of determining whether or not the torque value is equal to or less than the protection torque value, and when the result in the second step is NO, the process returns to the first step.

  More preferably, the load control mode is a third step that is executed when YES in the second step, and a virtual load torque when the speed ratio on the high speed side is set to the target speed ratio for the predetermined speed. A third step for determining whether or not the value is equal to or less than the protective torque value at the high speed side gear ratio, and a fourth step executed when YES in the third step, wherein only the predetermined shift stage And a fourth step of operating the electric actuator for HST using the high speed side gear ratio as a new target gear ratio.

  More preferably, the load control mode includes a fifth step of determining whether or not the speed ratio set in the fourth step is a set speed ratio defined by an operation state of the speed change operation member, The control device is configured to shift from the load control mode to the vehicle speed control mode when YES in the fifth step.

  In the various configurations, it is preferable that the protective torque value at the plurality of gear ratios is a protective torque at other gear ratios one speed lower than the one gear ratio compared to the protective torque value at one gear ratio. The value is set to a high value.

  In the various configurations, preferably, the HST is fluidly connected to the hydraulic pump via a pair of HST lines and driven by a hydraulic pump that is operatively driven by rotational power from the drive source. A hydraulic motor that outputs rotational power toward the wheel, and a pair of relief valves provided on each of the pair of HST lines, and at least one of the hydraulic pump and the hydraulic motor has a volume adjusted by the output adjustment member. The relief valve is configured to be variable so that the cracking pressure is within a range of 50 to 100% of the protection torque value.

  The present invention also provides a drive source, an HST that operatively inputs rotational power from the drive source, a drive wheel that is operatively driven by the output of the HST, a manually operable speed change operation member, An HST electric actuator that operatively drives the output adjustment member of the HST, an operation side sensor that detects an operation state of the speed change operation member, an output side sensor that detects the output state of the HST, and an input of the HST An input side sensor for detecting a state, a clutch device inserted in a transmission path from the HST to the drive wheel, and a brake device inserted in the transmission path on the downstream side in the transmission direction from the clutch device; A clutch operation member and a brake operation member which can be manually operated, a clutch operation side sensor which detects an operation state of the clutch operation member and the brake operation member; Rake operation side sensor, clutch electric actuator and brake electric actuator operatively driving the clutch device and the brake device, respectively, operation of the HST electric actuator, the clutch electric actuator and the brake electric actuator A control vehicle that controls the vehicle, wherein the control device includes an actual transmission ratio / load torque relationship and the HST for each of a plurality of transmission ratios defined by an operation state of the transmission operation member. A protective torque value for protecting the transmission including the control device, and the control device performs vehicle speed control for operating the electric actuator with a set gear ratio set based on a signal from the operation side sensor as a target gear ratio. While, the signal from the input side sensor and the output side sensor When the load torque value estimated from the actual speed ratio calculated based on the relationship between the actual speed ratio / load torque at the current target speed ratio exceeds the protective torque value at the current target speed ratio, the clutch device is in a power shut-off state There is provided a working vehicle that operates the electric actuator for clutch so that the brake actuator is operated and the brake electric actuator is operated so that the brake device is in a brake operating state.

  According to the working vehicle of one aspect of the present invention, the actual transmission ratio / load torque relationship and the protection torque value for protecting the transmission including the HST are set in the control device stored for each of the plurality of transmission ratios. Vehicle speed control mode in which the HST electric actuator is operated with the speed ratio as the target speed ratio, the actual speed ratio calculated by signals from the HST input side sensor and output side sensor, and the actual speed ratio / load at the current target speed ratio A load control mode that is executed when the load torque value estimated from the torque relationship exceeds the protection torque value at the current target gear ratio, and the load control mode is independent of the operation state of the speed change operation member. Since the electric actuator for HST is operated with a speed ratio lower than the current target speed ratio as a target speed ratio, cost increases can be prevented as much as possible. , It can be effectively prevented transmission damage including the HST by excessive traveling load.

  According to the working vehicle according to another aspect of the present invention, the control device in which the relationship between the actual gear ratio / load torque and the protection torque value for protecting the transmission including the HST is stored for each of the plurality of gear ratios is set. While performing vehicle speed control for operating the HST electric actuator with the gear ratio as the target gear ratio, the actual gear ratio calculated based on the signals from the HST input side sensor and the output side sensor and the actual gear ratio at the current target gear ratio When the load torque value estimated from the relationship between the load torque and the load torque exceeds the protection torque value at the current target gear ratio, the clutch actuator is operated so that the clutch device enters a power cut-off state, and the brake device Since the electric actuator for brake is operated so as to be in a brake operating state, while preventing cost increase as much as possible, The damaging transmission comprises the HST by the running load time can be effectively prevented.

FIG. 1 is a side view of a working vehicle according to an embodiment of the present invention. FIG. 2 is a schematic diagram of transmission of the working vehicle shown in FIG. FIG. 3 is a hydraulic circuit diagram of the working vehicle shown in FIGS. 1 and 2. FIG. 4 is a graph showing the relationship between the actual gear ratio / load torque and the protection torque value for each gear ratio stored in the control device of the working vehicle. FIG. 5 is a control flow of a vehicle speed control mode provided in the control device. FIG. 6 is a control flow of a load control mode provided in the control device. FIG. 7 is a graph showing the relationship between the actual gear ratio / load torque for each gear ratio and the protection torque value stored in the control device of the working vehicle, and the HST line hydraulic pressure exceeds a predetermined pressure when the HST line hydraulic pressure exceeds a predetermined pressure. It is a graph in case the relief valve which relieves the hydraulic fluid of a line is provided. FIG. 8 is a control flow of a modified example that can be provided in the control device.

Hereinafter, a preferred embodiment of a working vehicle according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a side view of a working vehicle 1A according to the present embodiment.
2 and 3 show a transmission schematic diagram and a hydraulic circuit diagram of the working vehicle 1A, respectively.

  As shown in FIGS. 1 to 3, the work vehicle 1 </ b> A includes a drive source 20, an HST 30 that operatively inputs rotational power from the drive source 20, and a drive that is operatively driven by the output of the HST 30. A wheel, a shift operation member 71 that can be manually operated, an HST electric actuator 300 that operatively drives the output adjustment member of the HST 30, an HST operation side sensor 810 that detects an operation state of the shift operation member 71, An HST input side sensor 815a that detects the input state of the HST 30; an HST output side sensor 815b that detects the output state of the HST 30; and a control device 80 that controls the operation of the electric actuator 300 for HST.

  As shown in FIGS. 2 and 3, the HST 30 is fluidly connected to the hydraulic pump 32 operatively driven by the rotational power from the drive source 20 and the hydraulic pump 32 via a pair of HST lines 100. And a hydraulic motor 34 that outputs rotational power toward the drive wheel, and an output adjustment member 36 that changes the volume of at least one of the hydraulic pump 32 and the hydraulic motor 34. By operating, the rotational speed of the hydraulic motor 34 with respect to the rotational speed of the hydraulic pump 32 can be changed.

  In the present embodiment, the HST 30 further supports a pump shaft 31 that supports the hydraulic pump 32 in a relatively non-rotatable manner while being operatively connected to the drive source 20, and a hydraulic motor 34 that does not relatively rotate. And a motor shaft 33 that outputs rotational power toward the drive wheel.

As shown in FIGS. 2 and 3, in the present embodiment, the output adjusting member 36 changes the volume of the hydraulic pump 32.
Specifically, the output adjusting member 36 is movable to change the suction / discharge amount of the corresponding hydraulic rotating body (the hydraulic pump 32 in the present embodiment) according to its own tilt position around the swing reference line. A swash plate (not shown) and a control shaft (not shown) operatively connected to the movable swash plate so that the movable swash plate tilts about a swing reference axis in response to rotation about its own axis. Including.

  The HST 30 further includes a charge line 460 for supplying hydraulic oil to the pair of HST lines 100, a pair of check valves 461 inserted in the charge lines 460, and the hydraulic pressure of the pair of HST lines 100. When a predetermined value is exceeded, a pair of relief valves 465 for relieving hydraulic oil from the pair of HST lines 100 are provided.

The charge line 460 is configured to supply a part of the pressure oil from the auxiliary pump 210 provided in the work vehicle 1A to each of the HST lines 100.
Specifically, as shown in FIGS. 2 and 3, the working vehicle 1A is provided with the auxiliary pump 210 that is operatively driven by the drive source 20, as shown in FIGS. .

  As shown in FIG. 3, the charge line 460 includes a common charge line 460a having one end fluidly connected to the discharge side of the auxiliary pump 210, and one end fluidly connected to the common charge line 460a and the other end. Has a pair of branch charge lines 460b fluidly connected to the pair of HST lines 100, respectively.

  As shown in FIG. 3, the check valve 461 is connected to the pair of branch charge lines 460b to prevent the reverse flow while allowing the flow of pressure oil from the common charge line 460a to the HST line 100. It is inserted.

Each of the relief valves 465 has a primary side fluidly connected to the corresponding HST line 100 and a secondary side fluidly connected to a low pressure site.
In the present embodiment, as shown in FIG. 3, the secondary side of the relief valve 465 is fluidly connected to the common charge line 460a.

  In the present embodiment, as shown in FIG. 1, the working vehicle 1A has a pair of left and right front wheels 12 and a pair of left and right rear wheels 11, and the rear wheel 11 acts as a main drive wheel. The front wheel 12 acts as a sub drive wheel.

  That is, as shown in FIG. 2, the working vehicle 1A according to the present embodiment serves as a sub driving wheel from a transmission path from the driving source 20 to the rear wheel 11 acting as a main driving wheel via the HST 30. It has a sub drive wheel power take-out mechanism 285 capable of taking out rotational power toward the front wheel 12 that acts, and the sub drive wheel power take-out mechanism 285 can selectively output power toward the sub drive wheel. It is like that.

The HST electric actuator 300 is configured to operate the output adjusting member 36 in response to a control signal from the control device 80.
As shown in FIG. 3, in the present embodiment, an electrohydraulic servo mechanism is employed as the HST electric actuator 300.

  Specifically, as shown in FIG. 3, the electrohydraulic servomechanism is in a state where the servo cylinder 310 and the internal space of the servo cylinder 310 are liquid-tightly separated into a first oil chamber 311 and a second oil chamber 312. A servo piston 315 accommodated in the servo cylinder 310 so as to be capable of reciprocating; a first supply / discharge line 151 and a second supply / discharge line 152 fluidly connected to the first and second oil chambers 311 and 312; A servo switching valve 320 that switches between supply and discharge of hydraulic oil to and from the first and second supply / discharge lines 151 and 152, and a servo solenoid valve that controls the position of the servo switching valve 320 based on a signal from the control device 80. 350.

  The servo piston 315 is reciprocally accommodated in the servo cylinder 310 in a state of being operatively connected to the output adjusting member 36, and the hydraulic oil is supplied to the first oil chamber 311 and the second oil chamber. When the hydraulic oil is discharged from 312, the movable swash plate is swung to the forward or reverse side around the rocking reference line, the hydraulic oil is discharged from the first oil chamber 311, and is operated to the second oil chamber 312. When oil is supplied, the movable swash plate is swung to the other side forward and reverse around the swing reference line.

  The servo switching valve 320 includes a first position for supplying hydraulic oil to the first supply / discharge line 151 and discharging hydraulic oil from the second supply / discharge line 152, and the first and second supply / discharge lines 151, 151. The holding position for closing 152 and the second position for discharging the hydraulic oil from the first supply / discharge line 151 and supplying the hydraulic oil to the second supply / discharge line 152 are selectively configured. Yes.

  In the present embodiment, as shown in FIG. 3, a part of the pressure oil from the auxiliary pump 210 is used as a hydraulic pressure source of the electrohydraulic servo mechanism.

  Specifically, the servo switching valve 320 is fluidly connected to a servo first supply line 471 whose primary side is fluidly connected to the discharge side of the auxiliary pump 210 and a servo first drain line 155 fluidly connected to an oil sump. In addition, the secondary side is fluidly connected to the first supply / discharge line 151 and the second supply / discharge line 152.

  When the servo switching valve 320 is located at the first position, the first supply / discharge line 151 is fluidly connected to the first servo supply line 471 and the second supply / discharge line 152 is connected to the servo first supply line 471. When the fluid is connected to the first drain line 155 and positioned at the holding position, the first and second supply / discharge lines 151 and 152 are closed, and when positioned at the second position, the first supply / discharge line 151 is closed. The servo first drain line 155 is fluidly connected and the second supply / discharge line 152 is fluidly connected to the servo first supply line 471.

The servo switching valve 320 is configured to be able to take the first position and the second position by being moved to one side and the other side in the axial direction across the holding position.
As shown in FIG. 3, the servo switching valve 320 is urged toward an initial position which is one of the first and second positions by a control piston urging member 345 acting on a control piston 340 described later. The control piston 340 is configured to be positioned at the holding position or the other of the first and second positions from the initial position by receiving the action of hydraulic pressure.

  Specifically, as shown in FIG. 3, the hydraulic servomechanism 300 includes a servo arm 330 having a base end engaged with the servo switching valve 320, a switching cylinder case 335, and a distal end of the servo arm 330. The control piston 340 accommodated in the switching cylinder case 335 so as to be reciprocally movable and the servo switching valve 320 are pushed toward the initial position via the servo arm 330. And the control piston biasing member 345 for biasing the control piston 340 in the direction to be moved.

The servo solenoid valve 350 is configured to switch between supply and discharge of hydraulic oil to and from the control piston 340.
Specifically, the servo solenoid valve 350 can selectively take a supply position for supplying hydraulic oil to the control piston 340 and a stop position for discharging hydraulic oil from the control piston 340, as shown in FIG. The position is controlled by the control device 80 so that the supply position and the stop position can be selectively taken in accordance with the operation state of the shift operation member 71 (see FIG. 1) that can be manually operated.

That is, the control device 80 has a vehicle speed control mode in which the output state of the HST 30 is changed according to the operation state of the speed change operation member 71.
In the vehicle speed control mode, an operation state of the shift operation member 71 is detected based on a signal from the HST operation side sensor 810 (see FIG. 3), and the HST 30 outputs an output state corresponding to the operation state of the shift operation member 71. The position of the servo electromagnetic valve 350 is controlled so that

Specifically, in the vehicle speed control mode, an actual speed ratio based on detection signals from the HST input side sensor 815a and the HST output side sensor 815b matches a set speed ratio based on the operation state of the speed change operation member 71. The position of the servo solenoid valve 350 is controlled.
The control device 80 has a load control mode in addition to the vehicle speed control mode. This load control mode will be described later.

  As shown in FIGS. 2 and 3, the working vehicle 1A according to the present embodiment further includes a forward / reverse switching device 50 inserted in a transmission path from the HST 30 to the drive wheel 11, and the forward / reverse travel. And a brake device 90 interposed in the transmission path on the downstream side in the transmission direction from the switching device 50.

  The forward / reverse switching device 50 is configured to be capable of selectively taking a forward state, a reverse state, and a power cut-off state in accordance with an operation state of a forward / reverse switching operation member 72 (see FIG. 1) that can be manually operated.

  Specifically, as shown in FIG. 3, the working vehicle 1 </ b> A according to the present embodiment includes the forward / reverse switching operation member 72 and a forward / reverse switching operation side sensor that detects an operation state of the forward / reverse switching operation member 72. 820 and a forward / reverse switching electric actuator 500 for switching the transmission state of the forward / reverse switching device 50.

  As shown in FIG. 3, in the present embodiment, the forward / reverse switching device 50 is a hydraulic type that operates using part of the pressure oil from the auxiliary pump 210 as hydraulic fluid. The forward electromagnetic valve 500F and the reverse electromagnetic valve 500R inserted between the auxiliary pump 210 and the forward / reverse switching device 50 form the forward / backward switching electric actuator 500.

  That is, the control device 80 moves the forward solenoid valve 500F and the reverse solenoid valve 500R so that the forward / reverse switching device 50 enters the forward state in accordance with the operation of the forward / reverse switching operation member 72 to the forward position. The forward solenoid valve 500F and the reverse solenoid valve 500R are positioned so that the forward / reverse switching device 50 is in the reverse state in accordance with the operation of the forward / reverse switching operation member 72 to the reverse position. The forward solenoid valve 500F and the reverse drive are controlled so that the forward / reverse switching device 50 is in a power cut-off state in accordance with an operation to the neutral position (interruption position) of the forward / reverse switching operation member 72. The position of the electromagnetic valve 500R is controlled.

  2 and 3, the working vehicle 1A according to the present embodiment further includes a planetary gear device 40 that cooperates with the HST 30 to form an HMT, and the forward / reverse switching device 50 Is arranged downstream in the transmission direction of the HMT.

  The planetary gear device 40 operatively inputs constant speed rotational power from the drive source 20 and operatively inputs variable rotational power from the HST 30 to output combined rotational power.

  Specifically, the planetary gear unit 40 operatively inputs a first element that operatively inputs a constant speed rotational power from the drive source 20 and a variable rotational power from the motor shaft 33 of the HST 30. 2 elements, and a third element that combines and outputs the rotational power of the first and second elements, and the HST 30 changes from the forward / reverse one side maximum output state to the forward / reverse other side maximum output state. Accordingly, the third element is configured to shift from a substantially output stop state to a maximum output state.

  As shown in FIG. 2, in the present embodiment, a carrier 41, a sun gear 42, and an internal gear 43 function as the first to third elements, respectively.

  The brake device 90 is configured to be able to selectively take a brake operation state and a brake release state in accordance with an operation state of a manually operable brake operation member 70 (see FIG. 3).

  Specifically, as shown in FIG. 3, the working vehicle 1A according to the present embodiment includes the brake operation member 70, a brake operation side sensor 825 that detects an operation state of the brake operation member 70, and the brake device. And an electric actuator for brake 900 for switching the operation state of 90.

  As shown in FIG. 3, in the present embodiment, the brake device 90 is of a hydraulic type that operates using part of the pressure oil from the auxiliary pump 210 as hydraulic oil. A brake solenoid valve interposed between the auxiliary pump 210 and the brake device 90 forms the brake electric actuator 900.

  That is, the control device 80 controls the brake solenoid valve so that the brake device 90 enters the brake operation state and the brake release state, respectively, according to the operation of the brake operation member 70 to the brake operation position and the brake release position. Perform position control.

  As shown in FIG. 2, the working vehicle 1A according to the present embodiment is further operated and selected on a multi-speed transmission 250 that multi-speeds the rotational power from the HMT, and a driven side of the multi-speed transmission 250. A braking brake 260 that can apply braking force, a differential gear device 270 that differentially transmits the rotational power from the multi-stage transmission 250 to the pair of left and right drive wheels 11, and the pair of drive wheels 11 independently. And a pair of traveling brake devices 15 to which a braking force can be applied.

  Reference numerals 73 and 74 in FIG. 1 are a parking brake operation member for operating the parking brake device 260 and an auxiliary transmission operation member for operating the multi-stage transmission 250, respectively.

Further, as shown in FIG. 2, the working vehicle 1A according to the present embodiment further includes a PTO shaft 380 for outputting rotational power toward the working machine, and the drive source 20 to the PTO shaft 380. A PTO clutch device 365 and a PTO transmission device 375 inserted in the PTO transmission path are provided.
Reference numeral 75 in FIG. 1 denotes a PTO speed change operation member for operating the PTO speed change device 375.

Here, a control structure by the control device 80 will be described.
The control device 80 controls a vehicle speed control mode in which the operation control of the HST electric actuator 300 is performed using the speed ratio set by the speed change operation member 71 as a target speed ratio, and the vehicle speed when the load on the HST 30 exceeds a predetermined value. A load control mode that is executed instead of the control mode.

  Whether the load on the HST 30 exceeds a predetermined value depends on the target gear ratio of the working vehicle 1A based on the signal from the HST operation side sensor 810, the HST input side sensor 815a, and the HST output side sensor 815b. The determination is based on the deviation from the actual transmission ratio of the working vehicle 1A based on the signal.

  Specifically, the control device 80 protects the transmission including the actual transmission ratio / load torque and the transmission including the HST 30 for each of a plurality of transmission ratios defined by the operation state of the transmission operation member 71. The protection torque value is stored in advance.

FIG. 4 shows a graph regarding the relationship between the actual transmission ratio / load torque and the protection torque value for each transmission ratio.
In FIG. 4, X (n) is an actual speed ratio / load torque relationship at the highest speed ratio among a plurality of speed ratios that can be set by the speed change operation member 71, and is described in order from X (n) to the left X (n−1), X (n−2),... Are the actual gear ratio / load torque relationship at the gear ratio on the low speed side one step from the maximum gear ratio.

  In each of the above-described relationships among a plurality of gear ratios that can be set, the gear ratio when the load torque value is zero is the theoretical gear ratio, that is, the gear ratio when the traveling load is zero. In FIG. 4, as an example, the theoretical gear ratios Rt (n), Rt (n-1), Rt (n-2) in X (n), X (n-1), and X (n-2). Is displayed.

The protective torque values in the actual gear ratio / load torque relationships X (n), X (n-1), and X (n-2) are T (n), T (n-1), and T (n, respectively). -2).
As shown in FIG. 4, the gear ratios corresponding to the load torque values T (n), T (n-1) and T (n-2) in the above relationships are Rr (n), Rr (n-1), Rr (n-2).
Conversely, when the maximum speed ratio is set by the speed change operation member 71 (that is, when the relationship X (n) in FIG. 4 is used), the actual speed ratio R (n) is theoretically calculated. When the speed ratio Rt (n) decreases to Rr (n), the load torque value reaches the protection torque value.

  More specifically, for example, when the maximum speed ratio is set by the speed change operation member 71, assuming that the traveling load on the work vehicle 1A is zero, the actual speed ratio R (n) of the work vehicle 1A (ie, The ratio of the output rotation speed of the HST 30 to the input rotation speed of the HST 30 is equal to the theoretical gear ratio Rt (n).

However, in practice, the working vehicle 1A is subjected to a traveling load. Therefore, the actual speed ratio R (n) of the working vehicle 1A based on the detection signals of the HST input side sensor 815a and the HST output side sensor 815b is smaller than the theoretical speed ratio Rt (n).
A deviation (ΔR = Rt (n) −R (n)) between Rt (n) and R (n) is proportional to the traveling load applied to the work vehicle 1A.

  Based on this idea, in the present embodiment, the control device 80 determines the relationship between the actual transmission ratio / load torque at the currently set transmission ratio and the HST input side sensor 815a and the HST output side sensor 815b. The load torque value is estimated from the actual gear ratio calculated based on the detection signal, and the current running load is allowed for the transmission including the HST 30 by comparing the load torque value with a preset protection torque value. Judging whether or not it should be done.

  That is, when the estimated load torque value is less than or equal to the protection torque value, it is determined that the current traveling load is sufficiently durable for the transmission, and when the load torque value exceeds the protection torque value, It is determined that the traveling load is in a dangerous state for the transmission.

  For example, at the maximum gear ratio (relationship X (n)), as shown in FIG. 4, when the actual gear ratio R (n) decreases from Rt (n) to Rr (n), the load torque value becomes the protective torque. It is estimated that the value T (n) has been reached.

  Therefore, when the maximum speed ratio is set by the speed change operation member 71, the actual speed ratio R (n) based on the detection signals from the HST input side sensor 815a and the HST output side sensor 815b is Rr (n If the actual transmission ratio R (n) is lower than Rr (n), the traveling load is determined to be within a range that the transmission load can withstand. It can be determined that the transmission is in a dangerous state.

Here, a control flow of the control device 80 will be described.
FIG. 5 shows a control flow in the vehicle speed control mode, and FIG. 6 shows a control flow in the load control mode.

  The vehicle speed control mode is started when a start condition is satisfied, for example, when the drive source 20 is in an activated state and a manually operable key is in a main power-on state.

  In the vehicle speed control mode, a step (step 11) of detecting an operation state of the speed change operation member 71 based on a signal from the HST operation side sensor 810, and a speed ratio based on the operation state of the speed change operation member 71 is set as a target speed change. As a ratio, there is a step (step 12) of controlling the operation of the electric actuator 300 for HST.

  Further, in the vehicle speed control mode, subsequent to step 12, an actual speed ratio is calculated based on signals from the HST input side sensor 815a and the HST output side sensor 815b (step 13); It is determined whether or not the load torque value estimated based on the actual speed ratio obtained in step 13 and the relationship between the actual speed ratio / load torque stored in advance is equal to or less than the protective torque value at the current target speed ratio. (Step 14).

If YES in step 14, the process proceeds to step 15 for determining whether or not to continue the vehicle speed control mode. If YES, the process returns to step 11 and if NO, the vehicle speed control mode is changed. finish.
The determination in step 15 can be made, for example, based on whether or not the key has been operated from the main power on position to the main power off position.

  If NO in step 14, that is, if the load torque value exceeds the protection torque value, the control device 80 activates the load control mode instead of the vehicle speed control mode.

  As shown in FIG. 6, in the load control mode, the operation control of the HST electric actuator 300 is performed with a speed ratio that is lower than the current target speed ratio by a predetermined speed as a target speed ratio (step 21). have.

That is, the load control mode controls the operation of the HST 30 with a speed ratio that is lower than the current target speed ratio by a predetermined speed as a target speed ratio, regardless of the operating state of the speed change operation member 71. Yes, thereby reducing the vehicle speed of the working vehicle 1A and reducing the traveling load on the transmission including the HST 30.
The predetermined shift speed includes every one or more shift speeds that can be set.

  The load control mode further includes a step (step 22) of detecting an actual speed ratio based on signals from the HST input side sensor 815a and the HST output side sensor 815b, and an actual speed ratio obtained in step 22. Determining whether the load torque value estimated based on the actual gear ratio / load torque relationship at the current target gear ratio is less than or equal to the protective torque value at the current target gear ratio (step 23). ing.

  If NO in step 23, that is, if the load torque value is still higher than the protective torque value at the current target gear ratio, the process returns to step 21 to set the speed ratio on the lower speed side by the predetermined speed. The ratio is set, and the steps 22 and 23 are performed.

  The load control mode is a step executed when YES in step 23, and the virtual load torque value when the high speed side gear ratio is set as the target speed ratio for the predetermined gear position is the high speed side gear change. A step (step 24) for determining whether or not the ratio is equal to or less than the protection torque value in the ratio, and a step that is executed when YES in step 24, the speed ratio on the high speed side is set to the target speed change by the predetermined shift stage. And a step (step 25) of controlling the operation of the electric actuator for HST as a ratio.

  In this way, whether or not the virtual load torque value when the target speed ratio is changed to the speed ratio on the high speed side by a predetermined speed from the current speed ratio is equal to or less than the protective torque value at the speed ratio on the high speed side is determined in advance. It is determined that the target speed ratio is changed excessively only when the virtual load torque value is determined to be equal to or less than the protection torque value, thereby preventing the target speed ratio from being changed excessively. Thus, smooth operation control of the HST electric actuator 300 can be realized.

  The load control mode is a step subsequent to the step 25, and it is determined whether or not the target speed ratio set in the step 25 is a set speed ratio based on an operation state of the speed change operation member 71. Step (step 26).

If YES in step 26, that is, if the current target speed ratio is a speed ratio according to the operating state of the speed change operation member 71, the load control mode is terminated and the vehicle speed control mode is entered. .
If NO in step 26, the process proceeds to step 22.

  Preferably, as shown in FIG. 4, the protection torque values at the plurality of gear ratios are protected at other gear ratios one speed lower than the one gear ratio as compared to the protection torque value at one gear ratio. The torque value is set to be a high value.

  According to such a preferable configuration, since the load torque value exceeds the protection torque value, the operation control of the HST electric actuator 300 is performed with the speed ratio that is lower than the current speed ratio by a predetermined speed as the target speed ratio. When performing the above, it is possible to increase the possibility that the load torque value at the new target gear ratio becomes equal to or less than the protective torque value at the target gear ratio, and as a result, the fluctuation range of the target gear ratio can be suppressed.

That is, suppose that the protective torque values at the plurality of gear ratios are constant (in this case, a straight line indicating the protective torque values in FIG. 4 is parallel to the horizontal axis).
In this case, since the load torque value at the current target speed ratio exceeds the protective torque value, even if the speed ratio on the low speed side is changed to a new target speed ratio by a predetermined speed, the new target speed ratio However, there is a high possibility that the load torque value still exceeds the protective torque value.

  When such a situation occurs, the step of setting the low speed side gear ratio as a new target speed ratio by a predetermined speed is repeated, and the operation control of the HST electric actuator 300 is finally performed so that the target vehicle speed is zero. Will do.

  On the other hand, the protection torque value at the plurality of gear ratios is higher than the protection torque value at the one gear ratio, and the protection torque value at another gear ratio on the one-speed lower side than the one gear ratio is higher. If so, it is possible to effectively prevent the step of setting the low speed side gear ratio as a new target gear ratio by a predetermined speed step from being excessively repeated.

  Further, in the present embodiment, as described above, the HST 30 is configured such that when the hydraulic pressure of the pair of HST lines 100 exceeds a predetermined value, the pair of relief valves 465 ( 3).

Thus, when the HST 30 is provided with the pair of relief valves 465, when the load torque value rises above the cracking pressure of the relief valve 465, the load torque value is substantially reduced by the relief action of the relief valve 465. Will decrease.
FIG. 7 shows the relationship between the actual gear ratio and the load torque in a state where the relief action of the pair of relief valves 465 is taken into consideration.

  By the way, the viscosity of the hydraulic oil flowing through the pair of HST lines 100 varies greatly depending on the oil temperature. And the fluctuation | variation of the viscosity of hydraulic fluid causes the change of the relationship of an actual gear ratio / load torque.

Specifically, when the oil temperature of the hydraulic oil is low (for example, about 50 ° C.), the rate of change of the load torque value with respect to the deviation between the theoretical gear ratio and the actual gear ratio increases (relationship Xl in FIG. 7). (See (n)).
On the other hand, when the oil temperature of the hydraulic oil is high (for example, about 100 ° C.), the rate of change of the load torque value with respect to the deviation between the theoretical gear ratio and the actual gear ratio is small (see relation Xh (n) in FIG. 7). ).

When the HST 30 does not have the relief valve 465, the relationship when the hydraulic oil is low temperature (for example, 50 ° C.) and high temperature (for example, 100 ° C.) is expressed by the broken line Xl (n) ′ and the broken line Xh ( n) 'becomes a straight line.
In this case, a large variation in the load torque value occurs due to a change in hydraulic oil temperature.

On the other hand, when the relief valve 465 is provided in the HST 30, the relationship when the hydraulic oil is low temperature (for example, 50 ° C.) and high temperature (for example, 100 ° C.) is the relief action of the relief valve 465. Is linear until the relief valve 465 is relieved. As the actual speed ratio becomes smaller, the change ratio of the load torque value with respect to the theoretical speed ratio and the deviation of the actual speed ratio becomes smaller. (See solid line Xl (n) and broken line Xh (n) in FIG. 7).
In this case, the variation in the load torque value due to the change in the hydraulic oil temperature becomes small.

Thus, the error of the load torque value due to the change in the hydraulic oil temperature can be suppressed by providing the HST 30 with the pair of relief valves 465.
The cracking pressure of the relief valve 465 is preferably 50 to 100% of the protective torque value from the viewpoint of reducing the error of the load torque value caused by the change in hydraulic oil temperature while maintaining the transmission efficiency of the HST 30 satisfactorily. It may be configured to be located within the range.

  In the present embodiment, when the load torque value exceeds the protective torque value, the speed change is performed at a speed lower than the current target speed ratio by a predetermined speed regardless of the operation state of the speed change operation member 71. The load on the transmission including the HST 30 is reduced by operating the HST electric actuator 300 using the ratio as a target speed ratio. Instead, the control device 80 has the following deformation control flow. It is also possible to prevent an excessive load from acting on the transmission.

  As described above, the working vehicle 1A includes the drive source 20, the HST 30, the drive wheel 11, the speed change operation member 71, the HST electric actuator 300, the HST operation side sensor 810, and the An HST input side sensor 815a, the HST output side sensor 815b, the forward / reverse switching device 50 inserted in a transmission path from the HST 30 to the drive wheel 11, and a downstream of the forward / reverse switching device 50 in the transmission direction The brake device 90 inserted in the transmission path on the side, the forward / reverse switching operation member 72 and the brake operation member 70, the forward / reverse switching operation side sensor 820 and the brake operation side sensor 825, The forward / reverse switching electric actuator that operatively drives the forward / reverse switching device 50 and the brake device 90, respectively. 00 and the electric actuator 900 for the brake, and a said control device 80 which controls the operation control of the HST electric actuator 300, the forward-reverse switching electric actuator 500 and the brake electric actuator 900.

  As described above, the forward / reverse switching device 50 is configured to be able to take a neutral state (power cut-off state) in addition to the forward drive state and the reverse drive state, and as a clutch device that cuts off the power transmission of the transmission path. Works.

  In the working vehicle 1A having such a configuration, the control device 80 may be configured to execute the load release mode when the load torque value exceeds the protection torque value while executing the vehicle speed control mode.

  Specifically, as shown in FIG. 8, the control device 80 performs the vehicle speed control mode including the steps 11 to 15 and the load executed when the load torque value exceeds the protection torque value. And a release mode.

  The load release mode is a step that is shifted when the result of step 14 is NO, that is, when the load torque value exceeds the protection torque value, regardless of the operation state of the forward / reverse switching operation member 72. A step (step 41) of controlling the operation of the electric actuator 500 for forward / reverse switching so that the forward / reverse switching device 50 acting also as the clutch device is in a neutral state (power cut-off state); and the brake operating member 70 A step (step 42) of controlling the operation of the brake electric actuator 900 so that the brake device 90 is in a brake operation state regardless of the operation state.

  According to this modification, the vehicle 1 </ b> A is safely stopped by the brake device 90 while releasing the load on the transmission including the HST 30 by causing the HST 30 and the driving wheel 11 to be in a power cut-off state. Can be made.

11 Rear wheel (main drive wheel)
20 Drive source 30 HST
32 Hydraulic pump 34 Hydraulic motor 36 Output adjustment member 50 Forward / reverse switching device (clutch device)
70 Brake operation member 71 Shift operation member 72 Forward / reverse switching operation member (clutch operation member)
80 Control device 90 Brake device 100 HST line 300 HST electric actuator 465 Relief valve 500 Forward / reverse switching electric actuator (clutch electric actuator)
810 HST operation side sensor 815a HST input side sensor 815b HST output side sensor 820 Forward / reverse switching operation side sensor (clutch operation side sensor)
825 Brake operation side sensor 900 Electric actuator for brake

Claims (7)

Drive source, HST that operatively inputs rotational power from the drive source, drive wheels that are operatively driven by the output of the HST, a speed change operation member that can be manually operated, and an output adjustment member of the HST An HST electric actuator for operatively driving, an operation side sensor for detecting an operation state of the shift operation member, an output side sensor for detecting the output state of the HST, and an input side for detecting the input state of the HST A working vehicle comprising a sensor and a control device for controlling the operation of the HST electric actuator;
The control device is provided with an actual gear ratio / load torque relationship and a protective torque value for protecting the transmission including the HST for each of a plurality of gear ratios defined by an operation state of the gearshift operating member. ,
The control device includes a vehicle speed control mode in which the HST electric actuator is operated with a set speed ratio set based on a signal from the operation side sensor as a target speed ratio, and signals from the input side sensor and the output side sensor. A load control mode that is executed when the load torque value estimated from the actual gear ratio calculated by the equation (1) and the relationship between the actual gear ratio / load torque at the current target gear ratio exceeds the protective torque value at the current target gear ratio; In the load control mode, the HST electric actuator is operated using a speed ratio lower than the current target speed ratio as a target speed ratio regardless of the operation state of the speed change operation member. Working vehicle.   The load control mode includes a first step of operating the electric actuator for HST with a speed ratio that is lower than a target speed ratio at a time by a predetermined speed as a new target speed ratio, the input side sensor, and the output side The load torque value estimated from the actual gear ratio calculated based on the signal from the sensor and the actual gear ratio / load torque relationship at the newly set current target gear ratio is the protective torque value at the current target gear ratio. 2. The working vehicle according to claim 1, further comprising: a second step of determining whether or not the following is satisfied, and returning to the first step when the second step is NO.   The load control mode is a third step that is executed when YES in the second step, and the virtual load torque value when the speed ratio on the high speed side is set to the target speed ratio for the predetermined speed is the high speed. A third step for determining whether or not a protective torque value is less than or equal to the gear ratio on the side, and a fourth step executed when YES in the third step, and a gear shift on the high speed side by the predetermined gear stage. The working vehicle according to claim 2, further comprising a fourth step of operating the electric actuator for HST with a ratio as a new target gear ratio. The load control mode includes a fifth step of determining whether or not the speed ratio set in the fourth step is a set speed ratio defined by an operation state of the speed change operation member;
4. The work vehicle according to claim 3, wherein the control device shifts from the load control mode to the vehicle speed control mode when YES in the fifth step. 5.   The protective torque values at the plurality of gear ratios are set such that the protective torque values at other gear ratios one speed lower than the one gear ratio are higher than the protective torque values at one gear ratio. The working vehicle according to any one of claims 1 to 4, wherein the working vehicle is provided. The HST is a hydraulic pump that is operatively driven by rotational power from the drive source, and a hydraulic motor that is fluidly connected to the hydraulic pump via a pair of HST lines and that outputs rotational power toward the drive wheels. And a pair of relief valves provided on each of the pair of HST lines, and at least one of the hydraulic pump and the hydraulic motor is a variable displacement type whose volume is variable by the output adjusting member. ,
The working vehicle according to claim 1, wherein the relief valve is configured such that a cracking pressure is located within a range of 50 to 100% of a protection torque value. Drive source, HST that operatively inputs rotational power from the drive source, drive wheels that are operatively driven by the output of the HST, a speed change operation member that can be manually operated, and an output adjustment member of the HST An HST electric actuator for operatively driving, an operation side sensor for detecting an operation state of the shift operation member, an output side sensor for detecting the output state of the HST, and an input side for detecting the input state of the HST A sensor, a clutch device inserted in the transmission path from the HST to the drive wheel, a brake device inserted in the transmission path on the downstream side in the transmission direction with respect to the clutch device, and a manually operable clutch operation Member and brake operation member, clutch operation side sensor for detecting operation state of clutch operation member and brake operation member, and brake operation side A motor, a clutch electric actuator and a brake electric actuator that operatively drive the clutch device and the brake device, respectively, and an operation control of the HST electric actuator, the clutch electric actuator, and the brake electric actuator. A working vehicle with a control device,
The control device is provided with an actual gear ratio / load torque relationship and a protective torque value for protecting the transmission including the HST for each of a plurality of gear ratios defined by an operation state of the gearshift operating member. ,
The control device performs vehicle speed control for operating the electric actuator using a set speed ratio set based on a signal from the operation side sensor as a target speed ratio, and based on signals from the input side sensor and the output side sensor. When the load torque value estimated from the calculated actual speed ratio and the relationship between the actual speed ratio / load torque at the current target speed ratio exceeds the protective torque value at the current target speed ratio, the clutch device The working vehicle is characterized in that the clutch electric actuator is operated so that the brake device is in a brake operating state.

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