JP2012149554A - Traveling drive circuit device for wheel type traveling working vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a traveling drive circuit device for a wheel type traveling working vehicle, with which output of a hydraulic pump supplying pressure oil to a travel motor can be sufficiently utilized.SOLUTION: This traveling drive circuit device includes: the travel motor 8 operating by the pressure oil of the first hydraulic pump 1; a traveling directional control valve 4 controlling the travel motor 8; and an accelerator pedal device 18 changing over the traveling directional control valve 4. The traveling drive circuit device also includes: a selector valve 11 provided in a bypass line 20 on the downstream side of the traveling directional control valve 4; a valve element control means controlling the selector valve 11 such that the opening area of the selector valve 11 becomes smaller than a maximum opening area according to increase of an operation amount of the accelerator pedal device 18; and a pilot pipe conduit 27 and a check valve 26 capable of supplying a flow rate flowing through the center bypass line 20 between the traveling directional control valve 4 and the selector valve 11 to the traveling directional control valve 4 when controlling the selector valve 11 to reduce the opening area thereof by the valve element control means.

Description

  The present invention relates to a traveling drive circuit device for a wheeled traveling working vehicle that is provided in a wheeled working vehicle such as a wheeled hydraulic excavator and performs bleed-off control of a traveling motor by a traveling direction control valve.

  A travel drive circuit device provided in a wheel-type hydraulic excavator that is a wheel-type work vehicle is switched according to an operation of a hydraulic pump operated by an engine, a plurality of work actuators and a travel motor, and a work operation device, It is switched according to the amount of depression of the operation direction control valve that controls the flow of pressure oil supplied from the hydraulic pump to the work actuator and the travel operation device, that is, the accelerator pedal device, and is supplied from the hydraulic pump to the travel motor. And a traveling direction control valve for controlling the flow of pressure oil. That is, the travel motor is rotated by adjusting the operation amount of the accelerator pedal of the accelerator pedal device, the wheeled hydraulic excavator is moved forward and backward, and the vehicle speed is controlled.

  Such a travel drive circuit device has a center bypass line communicating with the discharge line of the hydraulic pump, and the above-described open center travel direction control valve is disposed in the center bypass line. When the accelerator pedal is operated by the accelerator pedal device, the traveling direction control valve is switched, and the pressure oil from the hydraulic pump is supplied to the traveling motor via the traveling direction control valve, and the traveling motor is operated. When the accelerator pedal device is neutral, the return oil of the travel motor passes through the counter balance valve included in the brake device attached to the travel motor, and flows into the meter-in circuit from the meter-out circuit in the travel direction control valve. Pressure oil circulates between the travel direction control valve. There exists a thing shown by patent document 1 as this kind of prior art.

JP 2001-295675 A

  In the prior art described above, when the accelerator pedal device is neutral, the return oil of the travel motor is relieved by the overload relief valve of the brake device, and the pressure oil connects the input side and the output side of the brake device. The temperature rises as it passes through a throttle interposed in the circuit. Thereafter, as described above, the meter-out circuit flows into the meter-in circuit in the traveling direction control valve and is supplied to the traveling motor again. Thus, since the pressure oil circulates between the travel motor and the travel direction control valve while the temperature rises, the temperature of the pressure oil tends to become very high. For this reason, if the time during which the accelerator pedal device is kept neutral becomes long, thermal deformation of the spool of the traveling direction control valve occurs, and the sliding clearance between the housing portion of the traveling direction control valve and the spool becomes small.

  When the accelerator pedal device is operated in such a situation where the sliding clearance is small, the center bypass passage and the spool of the housing portion of the traveling direction control valve may be caught and stick. For this reason, usually, the notch of the spool of the traveling direction control valve is set large in advance. By setting in this way, the bleed-off flow rate flowing from the center bypass passage of the travel direction control valve to the tank via the center bypass line is increased so as to prevent the influence caused by the heat generation of the pressure oil, that is, the above-mentioned catch. Yes.

  By the way, setting the notch of the spool large as described above is effective for suppressing the influence of heat generated by the pressure oil, but the bleed-off flow rate accompanying the accelerator pedal operation increases. For this reason, in the prior art, the output of the hydraulic pump cannot be fully utilized, and energy loss tends to increase.

  The present invention has been made from the above-described state of the art, and the object thereof is a travel drive circuit device for a wheeled travel work vehicle that can fully utilize the output of a hydraulic pump that supplies pressure oil to a travel motor. Is to provide.

  In order to achieve this object, the present invention connects an engine, a hydraulic pump driven by the engine, a traveling motor operated by pressure oil discharged from the hydraulic pump, and the hydraulic pump and a tank. A wheel provided in a bypass line and provided with a traveling direction control valve that controls the flow of pressure oil supplied from the hydraulic pump to the traveling motor, and a traveling operation device that switches the traveling direction control valve. In the travel drive circuit device of the traveling vehicle, the valve body provided in the bypass line on the downstream side of the travel direction control valve and the opening of the valve body according to an increase in the operation amount of the travel operation device. When controlling the valve body control means to control the area to be smaller than the maximum opening area, and the valve body control means to reduce the opening area of the valve body, The flow rate through the center bypass line between the serial travel directional control valve and the valve body is characterized in that a flow guide means that can be supplied to the running directional control valve.

  In the present invention configured as described above, when the travel operation device is operated, the valve body provided in the center bypass line by the valve body control means has an opening area corresponding to an increase in the operation amount of the travel operation device. Is controlled to be smaller than the maximum opening area. As a result, the flow rate that is released from the valve body through the bypass line to the tank, that is, the bleed-off flow rate, is suppressed so as to decrease, and the flow rate that is blocked from flowing to the tank in the valve body It can be supplied to the control valve and used for the operation of the travel motor. That is, the present invention can reduce the bleed-off flow rate even in the case where the notch of the spool of the traveling direction control valve is set large, and can fully utilize the output of the hydraulic pump that supplies pressure oil to the traveling motor. it can.

Further, in the above invention, the present invention provides a working actuator that is operated by pressure oil discharged from the hydraulic pump, and a flow of pressure oil that is supplied from the hydraulic pump to the working actuator. A work direction control valve provided in the center bypass line on the downstream side of the center and a work operation device for switching the work direction control valve, and the valve body control means is configured to operate the work operation device. Accordingly, the opening area of the valve body is controlled to be the maximum opening area.

  In the present invention configured as described above, when the work operation device is operated, the valve body is controlled by the valve body control means so that the opening area becomes the maximum opening area. That is, the flow rate flowing from the valve body to the center bypass line is supplied to the work actuator via the work direction control valve that is disposed downstream of the valve body and is switched by the work operation device. It is used for the operation of the actuator.

  The present invention is characterized in that, in the above invention, the valve body comprises a switching valve or a pilot check valve.

  The present invention is characterized in that, in the above-mentioned invention, the valve body control means comprises electric operation means including a proportional solenoid valve for switching the valve body and a controller for controlling the proportional solenoid valve.

  Further, in the present invention according to the above-mentioned invention, the valve body control means is operated by a pilot pressure generated in accordance with the operation of the work operation device, and includes a hydraulic valve including an operation valve or a pilot check valve for switching and controlling the valve body. It is characterized by comprising actuating means.

  A traveling actuation circuit device for a wheeled traveling vehicle according to the present invention includes a valve body provided in a bypass line downstream of a traveling direction control valve that controls a flow of pressure oil supplied from a hydraulic pump to a traveling motor; A valve body control means for controlling the opening area of the valve body to be smaller than the maximum opening area in accordance with an increase in the operation amount of the travel operation device, and the opening area of the valve body is reduced by the valve body control means. The control device for travel is provided with a flow rate guiding means capable of supplying the flow rate flowing through the center bypass line between the travel direction control valve and the valve body to the travel direction control valve. When operated, the bleed-off flow rate is reduced even if the valve body control means makes the valve body opening area smaller than the maximum opening area and the notch of the spool of the traveling direction control valve is set large. Supplying a flow rate that is blocked by the valve body in the travel directional control valve through the flow directing means, it can be further supplied to the traveling motor. Thereby, the output of a hydraulic pump can fully be utilized and an energy loss can be made small compared with the past. Along with this, it is possible to suppress engine output and improve fuel efficiency.

1 is an electric / hydraulic circuit diagram showing a first embodiment of a travel drive circuit device for a wheeled travel work vehicle according to the present invention. It is a hydraulic circuit diagram which shows the brake device attached to the travel motor with which 1st Embodiment shown in FIG. 1 is equipped. It is a block diagram which shows the principal part structure of the controller with which 1st Embodiment is equipped. FIG. 4 is a diagram showing a function relationship set by each function generator included in the controller shown in FIG. 3, and (a) a diagram showing a relationship between a travel operation amount set by the function generator 13 a and a switching valve opening area; (B) is a figure which shows the relationship between the switching valve opening area set by the function generator 13c, and a proportional solenoid valve control pressure, (c) The figure shows the proportional solenoid valve control pressure set by the function generator 13d. It is a figure which shows the relationship with a proportional solenoid valve output. It is an electro-hydraulic circuit diagram showing a second embodiment of the present invention. It is a hydraulic circuit diagram which shows 3rd Embodiment of this invention. It is a hydraulic circuit diagram which shows 4th Embodiment of this invention.

  Embodiments of a travel drive circuit device for a wheeled travel work vehicle according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an electro-hydraulic circuit diagram showing a first embodiment of a travel drive circuit device for a wheel-type traveling work vehicle according to the present invention, and FIG. 2 is attached to a travel motor provided in the first embodiment shown in FIG. It is a hydraulic circuit diagram which shows a brake device. FIG. 3 is a block diagram showing the main configuration of the controller provided in the first embodiment, and FIG. 4 is a diagram showing the functional relationship set by each function generator included in the controller shown in FIG. Is a diagram showing the relationship between the travel operation amount set by the function generator 13a and the switching valve opening area, (b) is a relationship between the switching valve opening area set by the function generator 13c and the proportional solenoid valve control pressure. (C) is a figure which shows the relationship between the proportional solenoid valve control pressure set by the function generator 13d, and a proportional solenoid valve output.

  The travel drive circuit device according to the first embodiment is provided, for example, in a wheel-type hydraulic excavator. As shown in FIG. 1, the engine 22, a first hydraulic pump 1 driven by the engine 22, and a second hydraulic pressure are provided. A pump 2 and a pilot pump 3 are provided. Further, a travel motor 8 that is operated by pressure oil discharged from the first hydraulic pump 1 and a center bypass line 20 that is connected to a discharge pipeline of the first hydraulic pump 1 are provided. 8 includes an open center type traveling direction control valve 4 that controls the flow of pressure oil supplied to 8 and a traveling operation device that switches the traveling direction control valve 4, that is, an accelerator pedal device 18. . The center bypass line 20 is connected to the tank 21. Further, a working actuator 9 that is operated by pressure oil discharged from the second hydraulic pump 2, a working actuator 10 that is operated by pressure oil discharged from the second hydraulic pump 2 and the first hydraulic pump 1, and a second Work direction control valve 6 for controlling the flow of pressure oil supplied from the hydraulic pump 2 to the work actuator 9 and work for controlling the flow of pressure oil supplied from the second hydraulic pump 2 to the work actuator 10 And a directional control valve 7. The working actuators 9 and 10 described above are constituted by a boom cylinder, an arm cylinder, or the like in the wheeled hydraulic excavator.

  A brake device 25 shown in FIG. 2 is attached to the traveling motor 8 described above. The brake device 25 includes an overload relief valve 23 and a counter balance valve 24. When the travel direction control valve 4 is switched, the pressure oil discharged from the first hydraulic pump 1 is supplied to the travel motor 8 via the travel direction control valve 4 and the brake device 25.

  In the first embodiment, as shown in FIG. 1, a valve body provided in a bypass line 20 on the downstream side of the traveling direction control valve 4, for example, a switching valve 11 having an open position 11b and a closed position 11c, and an accelerator pedal. In response to an increase in the operation amount of the device 18, that is, the depression amount of the accelerator pedal, the opening area of the switching valve 11 is set to be smaller than the maximum opening area at the open position 11b, that is, to the closed position 11c side. Valve body control means for controlling. Further, when the valve body control means controls the opening area of the switching valve 11 to be small, the flow rate flowing through the center bypass line 20 between the traveling direction control valve 4 and the switching valve 11 is changed to the traveling direction control valve. 4 is provided.

  The valve body control means described above is constituted by, for example, an electric operation means that is connected to the pilot pump 3 and includes a proportional solenoid valve 12 that controls the switching valve 11 and a controller 13 that controls the proportional solenoid valve 12. is there. The proportional solenoid valve 12 is provided in a pilot line 34 that connects the pilot pump 3 and the control unit 11d of the switching valve 11, and switches to the lower position 12a or the upper position 12b according to a control signal output from the controller 13. It is done. Further, one end of the flow rate guiding means described above is connected to the center bypass line 20 between the traveling direction control valve 4 and the switching valve 11, and the other end is connected to the pressure supply port of the traveling direction control valve 4. The pilot line 27 and the pilot line 27 are provided in the pilot line 27 to allow the flow of the pressure oil from the center bypass line 20 side to the pressure oil supply port side of the traveling direction control valve 4 and to transfer the pressure oil in the reverse direction. And a check valve 26 for blocking the flow.

  Pressure sensors 14 and 15 for detecting the operation amount of the accelerator pedal device 18, that is, the travel operation amount are provided, and the detected pressure of the pressure sensors 14, 15, that is, the travel operation amount is output to the controller 13.

  In the first embodiment, the flow of pressure oil supplied from the first hydraulic pump 1 to the above-described working actuator 10 is controlled, and the working direction provided in the center bypass line 20 on the downstream side of the switching valve 11. A control valve 5 and a work operation device 19 for switching the work direction control valve 5 are provided. In addition, pressure sensors 16 and 17 for detecting that the work operation device 19 is operated are provided, and detection signals of these pressure sensors 16 and 17 are output to the controller 13.

  As shown in FIG. 3, the controller 13 includes a function generator 13 a that calculates the opening area of the switching valve 11 according to the operation amount of the accelerator pedal device 18 output from the pressure sensors 14, 15, that is, the travel operation amount, The calculation is performed by the switching unit 13b that is switched according to whether or not the work operation device 19 is operated, and the function generator 13a that is output via the switching unit 13b when the work operation device 19 is operated. A function generator 13c that calculates a control pressure of the proportional solenoid valve 12 according to the opening area of the switching valve 11, and an output of the proportional solenoid valve 12 according to the control pressure of the proportional solenoid valve 12 calculated by the function generator 13c And a function generator 13d for calculating

  As shown in FIG. 4A, the function generator 13a is set with a relationship between the travel operation amount and the switching valve opening area in which the opening area of the switching valve 11 gradually decreases as the traveling operation amount increases. Yes. As shown in FIG. 4 (b), the function generator 13c includes a switching valve opening area and a proportional solenoid valve control pressure which gradually decrease in the control pressure of the proportional solenoid valve 12 as the switching valve opening area increases. Relationship is set. As shown in FIG. 4C, the function generator 13d includes a proportional solenoid valve control pressure and a proportional solenoid valve in which the output of the proportional solenoid valve 12 gradually increases as the control pressure of the proportional solenoid valve 12 increases. The relationship with the output is set.

  The above-described switching unit 13b shown in FIG. 3 connects the function generator 13a and the function generator 13c when the work operation device 19 is operated and the signals of the pressure sensors 16 and 17 are input. When the work operation device 19 is not operated and the signals of the pressure sensors 16 and 17 are not input to the controller 13, the function generator 13a and the function generator 13c are switched to each other. When the switching unit 13b is switched so as to cut off between the function generator 13a and the function generator 13c, the switching valve 11 is set to the control unit of the proportional solenoid valve 12 from the controller 13 to the maximum opening area. A control signal for switching to the open position 11b to be held is output.

  The processing operation in the first embodiment configured as described above will be described below.

  As shown in FIG. 1, for example, the work operation device 19 is not operated, the work direction control valve 5 is held neutral, the accelerator pedal device 18 is not operated, and the travel direction control valve 4 is neutral. When being held, the pressure oil discharged from the first hydraulic pump 1 is returned to the tank 21 via the center bypass line 20, and the wheeled hydraulic excavator is stopped. At this time, the interior of the traveling motor 8 becomes a closed circuit, and the temperature of the pressure oil rises, which may adversely affect the device. Therefore, a small amount of pressure oil is released from the neutral throttle of the counter balance valve 24 of the brake device 25 shown in FIG. 2 and guided to the traveling direction control valve 4, and the meter-out circuit as described above in the traveling direction control valve 4. And a meter-in circuit communicate with each other to form a circulation circuit for returning the pressure oil to the suction side of the traveling motor 8 again. This suppresses an increase in the temperature of the pressure oil.

  During this time, a signal corresponding to the non-operation state is output from the pressure sensors 14 and 15 to the controller 13. In response to this, the function generator 13a shown in FIG. 4 obtains the maximum opening area Amax as the opening area of the switching valve 11 according to the signal corresponding to the non-operating state, that is, the operation amount equal to or less than the travel operation amount P2, and this maximum The opening area Amax is output to the function generator 13c via the switching unit 13b. The function generator 13c calculates the minimum control pressure P3 of the proportional solenoid valve 12 according to the maximum opening area Amax, and outputs this minimum control pressure P3 to the function generator 13d. In the function generator 13d, the minimum output A1 of the proportional solenoid valve 12 is obtained according to the minimum control pressure P3 of the proportional solenoid valve 12, and this minimum output A1 is output to the control unit of the proportional solenoid valve 12. As a result, the proportional solenoid valve 12 is held at the lower position 12a that blocks between the pilot pump 3 and the control unit 11d of the switching valve 11, as shown in FIG. Therefore, the switching valve 11 is held at the open position 11b which is the maximum opening area by the force of the spring 11a. That is, the center bypass line 20 is kept fully open. Accordingly, as described above, the pressure oil discharged from the first hydraulic pump 1 is returned to the tank 21 via the traveling direction control valve 4, the open position 11 b of the switching valve 11, and the center bypass line 20.

  When the accelerator pedal of the accelerator pedal device 18 is depressed from such a neutral state, for example, the traveling direction control valve 4 is switched according to the depression amount of the accelerator pedal, that is, the traveling operation amount, and discharged from the first hydraulic pump 1. The pressure oil is supplied to the traveling motor 8 via the traveling direction control valve 4 and the brake device 25 shown in FIG. As a result, the traveling motor 8 operates and the wheeled hydraulic excavator travels.

  During this time, the travel operation amount output from the pressure sensors 14 and 15 is output to the controller 13. In response to this, in the function generator 13a, the opening area corresponding to the operation amount of the accelerator pedal device 18, that is, the traveling operation amount, is obtained as the opening area of the switching valve 11. In order to simplify the description, for example, if the travel operation amount is the maximum operation amount P1 in FIG. 4A, the opening area of the switching valve 11 is determined by the function generator 13a according to the maximum operation amount P1. As a minimum opening area Amin is obtained. The minimum opening area Amin is output to the function generator 13c via the switching unit 13b. In the function generator 13c, the maximum control pressure P4 of the proportional solenoid valve 12 is obtained according to the minimum opening area Amin of the switching valve 11, and this maximum control pressure P4 is output to the function generator 13d. In the function generator 13d, the maximum output A2 of the proportional solenoid valve 12 is obtained according to the maximum control pressure P4 of the proportional solenoid valve 12, and this maximum output A2 is output to the control unit of the proportional solenoid valve 12. As a result, the proportional solenoid valve 12 is switched to the upper position 12b in FIG. 1 where the pilot pump 3 communicates with the control unit 11d of the switching valve 11 against the spring force. Therefore, the pressure oil discharged from the pilot pump 3 is given to the control unit 11d of the switching valve 11 through the upper position 12b of the proportional solenoid valve 12 and the pilot pipe line 34, and the switching valve 11 resists the force of the spring 11a. Then, it is switched to the closed position 11c. As a result, the center bypass line 20 is shut off at the switching valve 11.

  Accordingly, the pressure oil, that is, the bleed-off flow rate that has flowed from the traveling direction control valve 4 to the center bypass line 20 while the traveling motor 8 is being operated, is supplied to the traveling direction control valve via the pilot line 27 and the check valve 26. The pressure oil discharged from the first hydraulic pump 1 is joined to the pressure oil supply port 4 and supplied. That is, the flow rate flowing from the traveling direction control valve 4 to the bypass line 20 can be utilized for the operation of the traveling motor 8.

  Further, for example, when the work operation device 19 is operated from the state where only the accelerator pedal device 18 is operated as described above, the operation of the work operation device 19 is detected by the pressure sensors 16 and 17. Is input to the controller 13. The controller 13 switches the switching unit 13b shown in FIG. 3 to a position where the function generator 13a and the function generator 13c are disconnected based on the signals from the pressure sensors 16 and 17, and the maximum opening area of the switching valve 11 is reached. A process of outputting a corresponding control signal to the control unit of the proportional solenoid valve 12 is performed. By this control signal, the proportional solenoid valve 12 is switched to the lower position 12a shown in FIG. 1 by the force of the spring, and the switching valve 11 is switched to the open position 11b having the maximum opening area by the force of the spring 11a. That is, even when the accelerator pedal device 18 is operated to operate the traveling motor 8 and the wheel-type hydraulic excavator is traveling, when the work operation device 19 is operated, the switching valve 11 is fully opened. It is switched to the open position 11b that holds the area. Accordingly, the flow rate flowing from the traveling direction control valve 4 to the bypass line 20 is supplied to the working direction control valve 5 via the switching valve 11 and the center bypass line 20, and the second direction is set via the working direction control valve 5. 2 It is supplied to the working actuator 10 together with the pressure oil discharged from the hydraulic pump 2 and can be used for the operation of the working actuator 10. Even when the work operation device 19 is operated in a state where the accelerator pedal device 18 is not operated, the switching valve 11 is kept in the open position 11b which is the maximum opening area and is discharged from the first hydraulic pump 1. The pressurized oil is supplied to the working direction control valve 5 via the traveling direction control valve 4 and the open position 11 b of the switching valve 11.

  According to the first embodiment configured as described above, when the work operation device 19 is not operated as described above and the accelerator pedal device 18 is operated, the control signal output from the controller 13. Thus, the proportional solenoid valve 12 is switched to the upper position 12b in FIG. 1, and the opening area of the switching valve 11 is controlled to be smaller than the maximum opening area. As a result, the flow rate that is released from the switching valve 11 through the center bypass line 20 to the tank 21, that is, the bleed-off flow rate, is suppressed, and the flow rate that is prevented from flowing to the tank 21 by the switching valve 11 It can be supplied to the traveling direction control valve 4 via the path 27 and the check valve 26 and used for the operation of the traveling motor 8. That is, even if the notch of the spool of the traveling direction control valve 4 is set large, the bleed-off flow rate is reduced, and the output of the first hydraulic pump 1 that supplies pressure oil to the traveling motor 8 is fully utilized. Energy loss can be reduced. Along with this, it is possible to suppress the output of the engine 22 and improve fuel efficiency. That is, when it is going to ensure the performance equivalent to the past, the capacity | capacitance of the 1st hydraulic pump 1 can be made small, and the output of the engine 22 can be suppressed in connection with this.

  When the work operation device 19 is operated, the switching valve 11 is switched to the open position 11b having the maximum opening area, and the flow rate flowing from the open position 11b of the switch valve 11 to the center bypass line 20 is controlled in the work direction. It can be used for the operation of the working actuator 10 via the valve 5. In this respect as well, the output of the first hydraulic pump 1 can be utilized.

  FIG. 5 is an electric / hydraulic circuit diagram showing a second embodiment of the present invention. In the second embodiment shown in FIG. 5, the valve body provided in the center bypass line 20 on the downstream side of the traveling direction control valve 4 is configured by a pilot check valve 40. Other configurations are the same as those of the first embodiment described above.

  In the second embodiment configured as described above, when the work operation device 19 is not operated and the accelerator pedal device 18 is operated, for example, the proportional solenoid valve 12 is controlled by a control signal output from the controller 13. 1 is switched to the lower position 12a in FIG. 1, and the pilot check valve 40 functions as a check valve to block the flow rate flowing from the traveling direction control valve 4 to the bypass line 20. That is, the opening area of the pilot check valve 40 is controlled to be smaller than the maximum opening area in the open state when the pilot check valve 40 is operated and the check valve function is lost. As a result, the flow rate of the pilot check valve 40 that is prevented from flowing to the tank 21 is supplied to the pressure oil supply port of the travel direction control valve 4 via the pilot line 27 and the check valve 26 to operate the travel motor 8. The same effects as those of the first embodiment can be obtained.

  When the work operation device 19 is operated, the proportional solenoid valve 12 is switched to the upper position 12b by the control signal output from the controller 13, and the pilot pressure of the pilot pump 3 is pilot checked via the pilot line 35. It is supplied to the control unit of the valve 40. As a result, the pilot check valve 40 loses the check valve function and becomes an open state having the maximum opening area, and the flow rate flowing from the pilot check valve 40 to the center bypass line 20 can be utilized for driving the working actuator 10. it can. In this respect as well, the same effect as the first embodiment can be obtained. When the accelerator pedal device 18 is not operated, the proportional solenoid valve 12 is switched to the upper position 12b by a control signal from the controller 13, and the pilot pressure of the pilot pump 3 is controlled by the pilot check valve 40 via the pilot line 35. The check valve function of the pilot check valve 40 is lost.

  FIG. 6 is a hydraulic circuit diagram showing a third embodiment of the present invention. In the third embodiment shown in FIG. 6, the valve body control means for controlling the opening area of the valve body to be smaller than the maximum opening area in accordance with an increase in the operation amount of the accelerator pedal device 18 includes a working operation. It comprises hydraulic operating means including an operation valve 43 which is operated by the secondary pressure of the pilot pump 3 generated in accordance with the operation of the device 19 and which controls the valve body, that is, the switching valve 11 equivalent to that of the first embodiment.

  That is, in the third embodiment, the shuttle valve 41 that takes out the secondary pressure of the pilot pump 3 generated in accordance with the operation of the accelerator pedal device 18 and guides it to the pilot pipe line 36 connected to the control unit 11d of the switching valve 11. And a shuttle valve 42 for taking out the secondary pressure of the pilot pump 3 generated in accordance with the operation of the work operation device 19, and a pilot provided in the pilot pipe line 36 according to the secondary pressure guided from the shuttle valve 42. An operation valve 43 capable of blocking the pipe line 36 is provided. The other configuration is the same as the configuration of the first embodiment described above except for the electrical equipment portion, that is, the pressure sensors 14, 15, 16, 17, the proportional solenoid valve 12, and the controller 13.

  In the third embodiment configured as described above, when the work operation device 19 is not operated, the operation valve 43 is held at the open position 43a by the force of the spring 11a and switched to the shuttle valve 41. The control unit 11 d of the valve 11 is kept in a conductive state via a pilot line 36. For example, when the accelerator pedal device 18 is operated from such a state, the pilot pressure corresponding to the operation amount is taken out from the shuttle valve 41, and the switching valve 11 has an opening area larger than the maximum opening area via the operation valve 43. Is controlled to operate toward the closed position 11c so as to be smaller. Therefore, as in the first and second embodiments, the flow rate at which the flow to the tank 21 is blocked by the switching valve 11 is changed to the pressure oil supply port of the traveling direction control valve 4 via the pilot line 27 and the check valve 26. Can be utilized for the operation of the traveling motor 8, and the same effect as the first and second embodiments can be obtained.

  When the operation device 19 is operated, the secondary pressure of the pilot pump 3 taken out from the shuttle valve 42 is applied to the control unit of the operation valve 43, and the operation valve 43 closes against the spring force. The position is switched to position 43b. As a result, the pilot line 36 is shut off, and the switching valve 11 is switched to the open position 11b that maintains the maximum opening area by the force of the spring 11a. Therefore, the flow rate flowing from the switching valve 11 to the center bypass line 20 can be utilized for the operation of the work actuator 10. In this respect as well, the same effect as the first embodiment can be obtained. When the accelerator pedal device 18 is not operated, the secondary pressure of the pilot pump 3 is not supplied to the controller 11d of the switching valve 11, and the switching valve 11 is held at the open position 11b by the force of the spring 11a.

  FIG. 7 is a hydraulic circuit diagram showing a fourth embodiment of the present invention. In the fourth embodiment shown in FIG. 7, the pilot valve 3 is not provided in the pilot line 36 that connects the shuttle valve 41 and the control unit 11d of the switching valve 11 as in the third embodiment. A pilot line 46 is provided to connect the control unit 11e on the side where the spring 11a of the switching valve 11 is provided, and the check valve function is lost in the pilot line 46 according to the pilot pressure taken out from the shuttle valve 42. The pilot check valve 45 that is in an open state is provided. Also in the fourth embodiment, the valve body control means, that is, the means for controlling the switching valve 11 is constituted by a hydraulic operation means. Other configurations are the same as those of the third embodiment.

  In the fourth embodiment configured in this manner, the pilot check valve 45 functions as a check valve when the work operation device 19 is not operated, and the control unit of the control valve 11 from the pilot pump 3 side. 11e is kept in a state of blocking the flow of pressure oil to 11e. Further, when the accelerator pedal device 18 is neutral, the secondary pressure of the pilot pump 3 is not supplied to the control unit 11d of the switching valve 11, and the switching valve 11 maintains the maximum opening area by the force of the spring 11a. Can be switched to. For example, when the accelerator pedal device 18 is operated from such a state, the secondary pressure of the pilot pump 3 corresponding to the operation amount is taken out from the shuttle valve 41 and applied to the control unit 11 d of the switching valve 11. As a result, the switching valve 11 is controlled to operate toward the closed position 11c so that its opening area is smaller than the maximum opening area. Therefore, as in the third embodiment, the flow rate of the switching valve 11 that is prevented from flowing to the tank 21 is supplied to the pressure oil supply port of the traveling direction control valve 4 via the pilot line 27 and the check valve 26. The operation of the traveling motor 8 can be utilized, and the same effect as the third embodiment can be obtained.

  When the operating device 19 is operated, the secondary pressure of the pilot pump 3 taken out from the shuttle valve 42 is applied to the pilot check valve 45, and the pilot check valve 45 loses the check valve function. It becomes an open state. As a result, the pilot pump 3 and the control unit 11e of the switching valve 11 are conducted through the pilot line 46, and the secondary pressure of the pilot pump 3 is supplied to the switching valve 11 via the pilot line 46 and the pilot check valve 45. It is supplied to the control unit 11e. Therefore, the switching valve 11 is switched to the open position 11b that retains the maximum opening area according to the force of the spring 11a and the force of the secondary pressure of the pilot pump 3, and the flow rate that flows from the switching valve 11 to the center bypass line 20 Can be utilized for the operation of the working actuator 10. In this respect, the same effect as the third embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 1st hydraulic pump 3 Pilot pump 4 Traveling direction control valve 5 Working direction control valve 8 Traveling motor 10 Working actuator 11 Switching valve (valve body)
DESCRIPTION OF SYMBOLS 12 Proportional solenoid valve 13 Controller 13a Function generator 13b Switching part 13c Function generator 13d Function generator 14 Pressure sensor 15 Pressure sensor 16 Pressure sensor 17 Pressure sensor 18 Accelerator pedal apparatus (traveling operation apparatus)
19 Work Operating Device 20 Center Bypass Line 21 Tank 22 Engine 25 Brake Device 26 Check Valve 27 Pilot Pipeline 40 Pilot Check Valve (Valve)
43 Operating valve 45 Pilot check valve (valve)

Claims (5)

An engine, a hydraulic pump driven by the engine, a travel motor operated by pressure oil discharged from the hydraulic pump, and a bypass line connecting the hydraulic pump and the tank, In a travel drive circuit device for a wheeled travel work vehicle comprising a travel direction control valve that controls the flow of pressure oil supplied to a motor and a travel operation device that switches the travel direction control valve.
A valve body provided in the bypass line downstream of the traveling direction control valve;
Valve body control means for controlling the opening area of the valve body to be smaller than the maximum opening area in accordance with an increase in the operation amount of the travel operation device;
When the valve body control means controls the opening area of the valve body to be small, the flow rate flowing through the center bypass line between the travel direction control valve and the valve body is set to the travel direction control valve. A travel drive circuit device for a wheel-type traveling work vehicle, characterized in that it comprises a flow rate guiding means that can be supplied to the vehicle. In the traveling drive circuit device of the wheel type traveling working vehicle according to claim 1,
A working actuator that is operated by pressure oil discharged from the hydraulic pump and a flow of pressure oil that is supplied from the hydraulic pump to the working actuator are controlled and provided in the center bypass line on the downstream side of the valve body. A work direction control valve and a work operation device for switching the work direction control valve,
The travel drive circuit device for a wheel type traveling work vehicle, wherein the valve body control means controls the opening area of the valve body to be the maximum opening area as the work operation device is operated. In the traveling drive circuit device of the wheel type traveling working vehicle according to claim 2,
The above-mentioned valve body consists of a change-over valve or a pilot check valve, The traveling drive circuit device of the wheel type traveling working vehicle characterized by things. In the traveling drive circuit device of the wheel type traveling working vehicle according to claim 3,
The valve body control means comprises a proportional solenoid valve for switching and controlling the valve body, and an electric operation means including a controller for controlling the proportional solenoid valve. . In the traveling drive circuit device of the wheel type traveling working vehicle according to claim 3,
The valve body control means comprises hydraulic operating means including an operation valve or a pilot check valve which is operated by a pilot pressure generated in accordance with operation of the work operation device and which controls switching of the valve body. A traveling drive circuit device for a wheeled traveling vehicle.

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