JP2012224213A - Brake system of work vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain reduction in the number of parts, space saving, and easy installation to a vehicle body when a first brake unit using a master cylinder and a second brake unit using a control valve that reduces an amount of a pump discharge flow amount are provided as a brake system in a work vehicle equipped with an HST traveling drive system.SOLUTION: A brake operating system 17 in which an inching valve 16 and the master cylinder 18 are incorporated as one unit is provided, and the inching valve 16 and the master cylinder 18 are operated linked with each other in association with the operation of a brake pedal 15.

Description

  The present invention relates to a technical field of a brake device in a work vehicle including an HST travel drive device such as a wheel loader.

  In general, for example, some working vehicles such as wheel loaders are provided with an HST travel drive device in which a hydraulic motor is connected to a variable displacement hydraulic pump driven by an engine in a closed circuit and wheels are driven by the hydraulic motor. . In a work vehicle equipped with such an HST travel drive device, conventionally, as a brake device that applies braking to travel, first brake means that operates by brake pressure output from a master cylinder and applies braking force to wheels, The first brake is provided with two brake means including a second brake means for applying a braking force to the hydraulic motor by reducing a pump discharge flow rate by operating a control valve connected to a displacement control circuit of the variable displacement hydraulic pump. There is known a configuration in which the means and the second brake means are configured to operate based on the operation of a brake pedal (for example, see Patent Document 1).

Japanese Patent No. 3213173

In the thing of the said patent document 1, while the master cylinder which comprises a 1st brake means is arrange | positioned in a control tower, this master cylinder and a brake pedal are connected via several linkage members, such as an arm. ing. On the other hand, the control valve (inching clutch) constituting the second brake means is not arranged in the control tower, and the control valve and the brake pedal are linked via a plurality of linkage members such as operation wires. Has been. Further, in this case, the control valve is set to operate by operating the brake pedal to a small operating position, and the master cylinder is set to operate by operating beyond the operating position.
That is, in the thing of patent document 1, while connecting a master cylinder and a control valve separately, it is linked with a brake pedal using separate linkage members (some linkage members are shared). Yes. For this reason, there are problems that the number of parts increases and a space for arranging these many parts must be secured. Further, as in Patent Document 1, when setting the control valve to operate when the brake pedal is operated to a small operating position and the master cylinder is operated to operate beyond the operating position, the brake pedal In consideration of the assembly errors of the master cylinder, control valve, linkage member, etc., with these assembled in the vehicle body, the adjustment of the linkage member for the master cylinder and the adjustment of the linkage member for the control valve There is a problem that it is cumbersome and troublesome and inferior in workability, and there are problems to be solved by the present invention.

SUMMARY OF THE INVENTION The present invention was created in view of the above circumstances and has been created for the purpose of solving these problems. The invention of claim 1 provides a wheel by a hydraulic motor connected in a closed circuit to a variable displacement hydraulic pump. As a brake device that brakes the travel of the work vehicle in a work vehicle having an HST travel drive device that drives the vehicle, first brake means that actuates the brake pressure output from the master cylinder and applies braking force to the wheels. And a second brake means for applying a braking force to the hydraulic motor by reducing a pump discharge flow rate by operating a control valve connected to a capacity control circuit of the variable displacement hydraulic pump, and operating the first and second brake means. In order to provide a brake pedal to be operated, the control valve and the master cylinder are assembled as a unit. Provided over key actuating apparatus is a braking device in a work vehicle, characterized in that the arrangement for operating in conjunction with the control valve and the master cylinder with the operation of the brake pedal.
According to a second aspect of the present invention, in the brake operating device according to the first aspect, the spool constituting the control valve and the piston constituting the master cylinder are arranged on the same axis, and the spool is operated in accordance with the operation of the brake pedal. A brake device for a working vehicle characterized in that the second brake means is actuated by movement, and the first brake means is actuated by movement of the piston in conjunction with movement of the spool. .
According to a third aspect of the present invention, in the second aspect of the present invention, the setting of the brake pedal operation is preset between the spool and the piston by interposing an elastic machine that contracts due to the movement of the spool accompanying the operation of the brake pedal. When the operation position is reached, only the spool moves and the piston does not move, and when the brake pedal is operated beyond the set operation position, the spool and the piston move in conjunction with each other. It is a brake device in a working vehicle.
According to a fourth aspect of the present invention, in the second or third aspect, the brake operating device includes a push member that transmits the operation of the brake pedal to the spool by being pushed by the member on the brake pedal side. And a brake device in a working vehicle, characterized by being arranged coaxially with the piston.
A fifth aspect of the invention is a brake device for a working vehicle according to any one of the first to fourth aspects, wherein a brake pedal is integrally assembled with the brake operating device.

According to the first aspect of the present invention, the members that operate the control valve and the master cylinder in accordance with the operation of the brake pedal can be shared by the control valve and the master cylinder, so that the number of parts can be reduced and space can be saved. Can contribute. Furthermore, by attaching the brake actuator to the vehicle body, the control valve and the master cylinder can be attached to the vehicle body, and the first brake means and the second brake means are linked when the brake actuator is attached to the vehicle body. Therefore, it is possible to provide a brake device having a stable quality without the necessity of adjusting the vehicle body, and making the installation work to the vehicle body easy and without causing an adjustment error during the installation work to the vehicle body. .
According to the invention of claim 2, the first and second brake means can be operated by moving the piston in conjunction with the movement of the spool with a simple structure. Can contribute to
According to the invention of claim 3, in accordance with the operation of the brake pedal, the second brake means is actuated first, and then the first brake means is actuated. The burden on the means can be reduced. Furthermore, by changing the urging force of the ammunition, the interlocking relationship between the first brake means and the second brake means accompanying the operation of the brake pedal can be easily changed.
According to the fourth aspect of the invention, the operation of the brake pedal can be transmitted to the spool with a simple structure, and the structure of the brake operating device can be simplified.
With the invention of claim 5, the brake pedal is attached at the same time by attaching the brake operation device to the vehicle body, and adjustment of the positional relationship between the brake operation device and the brake pedal is not required at the time of attachment to the vehicle body, Thus, it is possible to contribute to further improvement in workability of the installation work.

It is a hydraulic circuit diagram for driving | running | working of a working vehicle. (A), (B) is sectional drawing of a brake actuator with which the brake pedal was assembled | attached, and a bottom view. (A), (B) is the front view of a brake actuator with which the brake pedal was assembled | attached, and a rear view. It is sectional drawing which shows a brake actuator when the brake pedal is not operated. It is sectional drawing which shows a brake actuator when a brake pedal is operated to the setting operation position. It is sectional drawing which shows a brake actuator when a brake pedal is operated exceeding a setting operation position. It is sectional drawing which shows the relationship between the moving stroke of a spool, and the opening amount of an inching valve.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a traveling hydraulic circuit for a working vehicle equipped with an HST traveling drive device such as a wheel loader. In FIG. 1, 1 is a variable displacement hydraulic pump driven by an engine E, The hydraulic pump 1 is connected in a closed circuit to a variable displacement hydraulic motor 4 through a pair of drive circuits 2 and 3. The pressure oil discharged from the hydraulic pump 1 is supplied to the hydraulic motor 4 via one drive circuit 2 or 3, and further flows to the hydraulic pump 1 via the other drive circuit 3 or 2. The hydraulic motor 4 circulates, whereby the hydraulic motor 4 rotates forward or backward, and the rotation of the hydraulic motor 4 is transmitted to the axle 5 to drive the wheel 6 forward or backward.

  A charge pump 7 is driven by the engine E. The charge pump 7 supplies pressure oil to the pair of drive circuits 2 and 3 through a charge circuit 8 and also through a sequence valve 9. A signal pressure is supplied to the capacity control circuit 10 of the hydraulic pump 1.

  The discharge flow rate of the charge pump 7 increases or decreases according to the engine speed controlled according to the operation amount of an accelerator pedal (not shown). On the other hand, on the upstream side of the sequence valve 9, an orifice 11 for generating a differential pressure corresponding to the discharge flow rate of the charge pump 7 on the primary side and the secondary side is arranged, and the primary side and secondary side of the orifice 11 are arranged. When the pilot pressure acts on the sequence valve 9 from the side, the sequence valve 9 generates a signal pressure corresponding to the engine speed and supplies it to the capacity control circuit 10.

  The displacement control circuit 10 is a circuit for controlling a regulator 12 that varies the discharge direction and displacement of the hydraulic pump 1. The displacement control circuit 10 is provided with a forward / neutral / reverse switching valve 13. ing. The forward / neutral / reverse switching valve 13 is configured to switch to a neutral position N, a forward position F, and a reverse position R based on an operation of a forward / reverse switching operation tool (not shown).

  When the forward / neutral / reverse switching valve 13 is in the neutral position N, the signal pressure from the sequence valve 9 is not supplied to the regulator 12, and the forward and backward oil chambers 12a and 12b of the regulator 12 are oiled. The tank 12 communicates with the tank T, whereby the regulator 12 controls the hydraulic pump 1 so that the discharge flow rate to the pair of drive circuits 2 and 3 becomes zero. On the other hand, when the forward / neutral / reverse switching valve 13 is at the forward position F, the signal pressure from the sequence valve 9 is supplied to the forward-side oil chamber 12a of the regulator 12, whereby the regulator 12 is discharged to one drive circuit 2. The hydraulic pump 1 is controlled to supply oil. When the forward / neutral / reverse switching valve 13 is in the reverse position R, the signal pressure from the sequence valve 9 is supplied to the reverse oil chamber 12b of the regulator 12, whereby the regulator 12 is discharged to the other drive circuit 3. The hydraulic pump 1 is controlled to supply oil. Further, when the forward / neutral / reverse switching valve 13 is switched to the forward position F or the reverse position R, the discharge flow rate of the hydraulic pump 1 is from the sequence valve 9 to the forward oil chamber 12a or the reverse oil chamber of the regulator 12. Control is performed so as to increase / decrease according to the level of the signal pressure input to 12b, that is, increase / decrease according to the level of engine speed.

  Further, an inching oil passage 14 extending to the oil tank T is connected to the capacity control circuit 10 extending from the sequence valve 9 to the forward / neutral / reverse switching valve 13. The inching oil passage 14 is provided with an inching valve (corresponding to the control valve of the present invention) 16 that operates based on the operation of the brake pedal 15. The inching valve 16 is a variable throttle valve, and is incorporated in a brake operating device 17 as will be described later. However, the inching oil passage 14 is closed when the brake pedal 15 is not operated. The signal pressure output from the sequence valve 9 to the capacity control circuit 10 is supplied as it is to the regulator 12 via the forward / neutral / reverse switching valve 13, and thus the hydraulic pump 1 corresponding to the engine speed described above. The discharge flow rate control is performed. On the other hand, when the brake pedal 15 is operated, the inching valve 16 opens the inching oil passage 14, whereby the signal pressure output from the sequence valve 9 to the capacity control circuit 10 flows into the oil tank T. Thus, the signal pressure supplied from the capacity control circuit 10 to the regulator 12 via the forward / neutral / reverse switching valve 13 decreases, and the discharge flow rate of the hydraulic pump 1 decreases (including zero). A braking force is applied to the hydraulic motor 4, and the second brake means is operated in this way. In the present embodiment, the inching oil passage 14 and the inching valve 16 constitute the second brake means of the present invention.

  On the other hand, 18 is a master cylinder, which is incorporated in the brake actuating device 17 together with the inching valve 16, and will be described in detail later. The master cylinder 18 is operated when the brake pedal 15 is operated. A brake pressure corresponding to the amount is supplied to the service brake 19. The service brake 19 employs a wet disc brake in this embodiment, but is provided at a mounting portion between the axle 5 and the wheel 6 so that the wheel 6 is braked with a braking force corresponding to the supplied brake pressure. Braking is performed, and the first brake means is actuated in this manner. In the present embodiment, the master cylinder 18 and the service brake 19 constitute the first brake means of the present invention. In the figure, 20 is a reservoir tank for storing brake fluid.

  Next, the brake actuator 17 will be described with reference to FIGS. The brake actuating device 17 includes the inching valve 16 and the master cylinder 18 incorporated as a unit. The body 21 of the brake actuating device 17 includes an upper body 21X and a lower body 21Y. The bolts 22 are integrally assembled.

  A flange portion 21a fixed to the floor surface A of the cab of the work vehicle is integrally formed on the upper body 21X. The brake actuator 17 is mounted and fixed to the floor surface A in a state where the flange portion 21a is placed on the floor surface A of the cab and the body 21 is housed under the floor. In the drawing, 21b is a bolt insertion hole into which a bolt (not shown) for attaching the flange portion 21a to the floor surface A is inserted.

  A support bracket 21c is erected on the upper surface of the flange portion 21a, and a swing support shaft 15a of one of the left and right brake pedals 15 is rotatably supported on the support bracket 21c. Yes. Here, the swing support shaft 15a of the brake pedal 15 is fixed to the base end portion of the brake pedal 15, and swings when the distal end side of the brake pedal 15 swings about the swing support shaft 15a as a stepping operation. The moving support shaft 15a also rotates integrally. Further, a pair of left and right brake pedals 15 are provided, and the swinging support shafts 15a of the left and right brake pedals 15 are connected to each other by a connecting rod 23 so that the left and right brake pedals 15a and 15b can be integrally rotated. Even when the pedal 15 is depressed, the left and right brake pedals 15 swing in conjunction with each other. Then, as described above, one of the left and right brake pedals 15 is integrally assembled with the brake actuator 17 by the pivot support shaft 15a being rotatably supported by the support bracket 21c. On the other hand, the swing support shaft 15a of the other brake pedal 15 is rotatably supported by a support member fixed to the floor A of the driver's seat, although not shown. The brake operating device 17 can be assembled to either the left or right brake pedal 15, but one of the brake pedals 15 is selected in consideration of the layout of other members disposed under the floor of the cab. .

  A pressure roller (corresponding to a member on the brake pedal side of the present invention) 25 is provided on the lower surface side of the brake pedal 15 (the brake pedal 15 to which the brake operating device 17 is assembled, hereinafter the same) via a pin shaft 24. Is rotatably supported. The pressing roller 25 is positioned on the distal end side of the brake pedal 15 with respect to the swing support shaft 15a, and is moved downward as the brake pedal 15 is depressed, and a push member 26 described later. It is in contact with the upper surface of the roller in a freely rollable state.

  On the other hand, the upper body 21X is provided with a first cylinder hole 21d that faces in the vertical direction, and a spool 27 constituting the inching valve 16 is fitted in the first cylinder hole 21d so as to be slidable in the vertical direction. Has been. Further, a first port 28 connected to the capacity control circuit 10 and a second port 29 connected to the oil tank T are formed in the upper body 21X so as to communicate with the first cylinder hole 21d.

  The upper portion of the spool 27 protrudes upward from the upper end of the upper body 21X, and the push member 26 is fixed to the protruding upper end portion so as to be coaxial with the spool 27. In addition, a cylindrical hole 27a having an opening on the lower side is formed in the lower portion of the spool 27. Inside the cylinder hole 27a, an upper portion of a transmission rod 30 and a first spring (described in the bulletin board of the present invention) are formed. (Corresponding) 31 is furnished. Further, the outer peripheral surface of the spool 27 is formed in a land portion 27b whose lower portion is fitted in the first cylindrical hole 21d with no gap, and a portion above the land portion 27b is a first cylindrical hole. The first oil passage 32 is formed between the outer peripheral surface of the spool 27 and the inner peripheral surface of the first cylindrical hole 21d. Further, the spool 27 is formed with a second oil passage 33 that communicates the inside of the cylindrical hole 27 a with the first oil passage 32. Further, the inside of the cylinder of the cylindrical hole 27a and the second port 29 communicate with each other through a third oil passage 34 formed between the outer peripheral surface of the transmission rod 30 and the inner peripheral surface of the first cylindrical hole 21d. It has become.

  The spool 27 is held at the non-operating position by the urging force of the first spring 31 and a second spring 35 described later when the brake pedal 15 is not depressed. In this state, the first port 28 connected to the capacity control circuit 10 is closed by the land portion 27b of the spool 27, whereby the inching valve 16 closes the inching oil passage 14 described above. The signal pressure of the capacity control circuit 10 does not flow to the oil tank T, and therefore the second brake means is inactive. On the other hand, when the brake pedal 15 is depressed, the push roller 25 is pressed to move the push member 26 downward, and the push member 26 is further pressed to move the spool 27 downward. When the spool 27 moves to a position where the first port 28 communicates with the first oil passage 32, the first port 28 is connected to the first oil passage 32, the second oil passage 33, the cylinder interior of the cylindrical hole 27a, the third The inching valve 16 opens the inching oil passage 14 and allows the signal pressure of the capacity control circuit 10 to flow to the oil tank T, thus communicating with the second port 29 via the oil passage 34. The second brake means is activated. In this case, the opening amount of the inching valve 16 increases as the moving stroke of the spool 27 increases until the moving stroke of the spool 27 reaches a preset setting stroke, as shown in FIG. After reaching the value, it is set to maintain the fully open state.

  On the other hand, the transmission rod 30 is interposed between the spool 27 and the piston 36 so as to transmit the movement of the spool 27 to a piston 36, which will be described later. 21d is slidably fitted up and down, and there is a gap between the outer peripheral surface of the transmission rod 30 above the support member 37 and the inner peripheral surface of the first cylindrical hole 21d. The third oil passage 34 is formed by the gap. The upper portion of the transmission rod 30 is loosely fitted into the cylindrical hole 27a of the spool 27, and a cylindrical hole 30a having an upper opening is formed. The first spring 31 is interposed between the bottom of the cylindrical hole 30 a at the top of the transmission rod 30 and the bottom of the cylindrical hole 27 a at the bottom of the spool 27.

  The transmission rod 30 is held at a non-operating position by a biasing force of a second spring 35 described later when the brake pedal 15 is not depressed, but in this state, the cylindrical hole of the transmission rod 30 is The upper end of 30 a and the bottom of the cylindrical hole 27 a of the spool 27 are separated by the urging force of the first spring 31. On the other hand, when the brake pedal 15 is depressed, the spool 27 moves downward as described above. However, in this embodiment, the urging force of the first spring 31 is sufficiently larger than the urging force of the second spring 35. Therefore, until the hole bottom of the cylindrical hole 27a of the spool 27 contacts the upper end of the cylindrical hole 30a of the transmission rod 30, only the first spring 31 is reduced even if the spool 27 moves downward. Thus, the second spring 35 is not reduced, so that the transmission rod 30 is held in the non-operating position and the movement of the spool 27 is not transmitted to the piston 36. On the other hand, after the bottom of the cylindrical hole 27a of the spool 27 comes into contact with the upper end of the cylindrical hole 30a of the transmission rod 30, the transmission rod 30 moves together with the movement of the spool 27 accompanying the stepping operation of the brake pedal 15, As a result, the movement of the spool 27 is transmitted to the piston 36.

  Here, in the present embodiment, the movement stroke of the spool 27 until the spool 27 contacts the transmission rod 30 (the bottom of the cylindrical hole 27a of the spool 27 contacts the upper end of the cylindrical hole 30a of the transmission rod 30) The opening amount of the inching valve 16 is designed to substantially coincide with the set stroke at which the inching valve 16 is fully opened, so that when the spool 27 comes into contact with the transmission rod 30, the inching valve 16 is fully opened. Is set. Further, the operation position of the brake rake pedal 15 when the spool 27 abuts on the transmission rod 30 is set in advance as the setting operation position. Thus, when the operation of the brake pedal 15 reaches the setting operation position, the spool 27 is moved and the piston 36 is not moved. However, when the brake pedal 15 is operated beyond the set operation position, the spool 27 and the piston 36 are moved in conjunction with each other.

  On the other hand, in the lower body 21Y, a second cylinder hole 21e communicating with the first cylinder hole 21d is opened coaxially with the first cylinder hole 21d formed in the upper body 21X. A piston 36 constituting the master cylinder 18 is fitted in the second cylinder hole 21e so as to be slidable in the vertical direction. Thus, the piston 36 is arranged so as to be coaxial with the spool 27 described above. Yes. Further, a third port 38 connected to the service brake 19 and a fourth port 39 connected to the reservoir tank 20 are formed in the lower body 21Y. The fourth port 39 communicates with the second cylinder hole 21e via a relief port 39a and a communication hole 39b.

  The piston 36 includes a piston main body portion 36a, an operation rod portion 36b provided integrally with an upper portion of the piston main body portion 36a, and a tip rod portion 36c provided integrally with a lower portion of the piston main body portion 36a. Although configured, a concave portion 36d is formed in the upper portion of the operating rod 36b, and a convex portion 30b formed in the lower portion of the transmission rod 30 is fitted in the concave portion 36d. The lower end of the convex portion 30b is in contact with the bottom surface of the concave portion 36d. Thus, when the transmission rod 30 moves downward, the piston 36 moves together. The cylinder interior of the second cylinder hole 21e below the piston body 36a is a brake fluid chamber 42 communicating with the third port 38, and the cylinder bottom of the piston body 36a and the second cylinder hole 21e. A second spring 35 that biases the piston 36 upward is interposed between the first spring 21f and the second spring 35f.

  In the case where the brake pedal 15 is not depressed or is operated up to the operation position, that is, in a state where the transmission rod 30 is held at the non-operation position, the piston 36 is biased by the second spring 35. Thus, the upper end of the actuating rod portion 36b abuts against the stopper 43 and is positioned at a non-actuating position where further upward movement is restricted. In this state, the relief port 39a communicates with the brake fluid chamber 42, and no brake pressure is generated in the brake fluid chamber 42, so that the first brake means is inactive. On the other hand, when the brake pedal 15 is depressed beyond the set operation position, the transmission rod 30 moves downward together with the spool 27 and the piston 36 moves downward together with the transmission rod 30 as described above. Due to the movement of the piston 36, the brake fluid chamber 42 and the relief port 39a are shut off, and a brake pressure is generated in the brake fluid chamber 42 and supplied to the service brake 19. The brake means is activated. In this case, the brake pressure generated in the brake fluid chamber 42 increases / decreases in accordance with the movement stroke of the piston 36, that is, the operation amount of the brake pedal 15, and thus is controlled to the wheel 6 by the first brake means. The power is increased or decreased according to the amount of operation of the brake pedal 15.

  Thus, the inching valve 16 and the master cylinder 18 are incorporated in the brake operating device 17, and the inching valve 16 and the master cylinder 18 operate in conjunction with the operation of the brake pedal 15. become. That is, as described above, when the brake pedal 15 is not depressed, both the spool 27 of the inching valve 16 and the piston 36 of the master cylinder 18 are in the non-operating position. In this state, the second brake Both the means and the first brake means are not operating. On the other hand, when the brake pedal 15 is depressed, the depression of the brake pedal 15 moves the spool 27 downward via the pressing roller 25 and the push member 26, whereby the inching valve 16 is closed and the second brake means Operates. The movement of the spool 27 is not transmitted to the piston 36 when the operation of the brake pedal 15 is up to the set operation range position, and the first brake means is not activated by the operation up to the set operation position. When 15 is stepped over the set operation position, the movement of the spool 27 is transmitted to the piston 36 via the transmission rod 30 to move the piston 36 downward, whereby the brake pressure is supplied to the service brake 19. Thus, the first brake means is activated.

  By the way, as described above, the first spring 31 is interposed between the spool 27 and the transmission rod 30 and is contracted by the movement of the spool 27 accompanying the operation of the brake pedal 15. In the operation up to the setting operation position, the movement of the spool 27 is not transmitted to the piston 36 because the first spring 31 is contracted, that is, the first brake means is not operated. By changing the urging force of the spring 31, the setting operation position, that is, the operation position of the brake pedal 15 at which the piston 27 starts to move can be changed. That is, in the present embodiment, as described above, the urging force of the first spring 31 is set to be sufficiently smaller than the urging force of the second spring 35. Therefore, the spool 27 and the transmission rod 30 are Until the contact, only the first spring 31 is reduced and the second spring 35 is not reduced. However, by increasing the urging force of the first spring 31 as compared with the present embodiment, The transmission rod 30 can be moved before the transmission rod 30 comes into contact with the transmission rod 30. In this case, as the urging force of the first spring 31 is increased, the transmission rod 30 can be moved at a time when the moving stroke of the spool 27 is small, and thus the urging force of the first spring 31 is changed. Thus, it is possible to change the setting operation position of the brake pedal 15 at which the piston 27 starts to move, that is, the first brake means starts to operate, whereby the first brake means accompanying the operation of the brake pedal 15 can be performed. And the second brake means can be easily changed.

  In the present embodiment configured as described, the work vehicle includes an HST travel drive device that drives the wheels 6 by a hydraulic motor 4 connected to the variable displacement hydraulic pump 1 in a closed circuit, and a brake that brakes travel. As a device, the first brake means that operates by the brake pressure output from the master cylinder 18 to apply the braking force to the wheel 6 and the pump discharge by the operation of the inching valve 16 connected to the capacity control circuit 10 of the hydraulic pump 1. There are provided second brake means for reducing the flow rate and applying a braking force to the hydraulic motor 4, and a brake pedal 15 to be operated to operate the first and second brake means. The master cylinder 18 is incorporated in the brake operating device 17 as one unit, and the brake pedal 1 It will operate in conjunction with each other due to the operation.

  As a result, the inching valve 16 and the master cylinder 18 can share the members that operate the inching valve 16 and the master cylinder 18 in accordance with the operation of the brake pedal 15 (in this embodiment, the pressing roller 25 and the push member 26). As a result, the number of parts can be reduced and space can be saved. Further, by attaching the brake actuator 17 to the vehicle body, the inching valve 16 and the master cylinder 18 are attached to the vehicle body, and the first brake means and the second brake means are attached when the brake actuator 17 is attached to the vehicle body. There is no need to adjust the interlocking relationship with the vehicle, and it is easy to install on the vehicle body, and there is no risk of adjustment errors during installation to the vehicle body, providing a stable quality brake device. can do.

  Further, in this device, the brake operating device 17 includes a spool 27 that constitutes the inching valve 16 and a piston 36 that constitutes the master cylinder 18, and the spool 27 is operated in accordance with the operation of the brake pedal 15. The second brake means is actuated by movement, and the first brake means is actuated by moving the piston 36 in conjunction with the movement of the spool 27. By arranging the spool 27 and the piston 36 coaxially in this way, the second and first brake means can be operated by moving the piston 36 in conjunction with the movement of the spool 27 with a simple structure. Therefore, it is possible to contribute to the simplification of the structure of the brake operating device 17.

  Further, a first spring 31 that is contracted by the movement of the spool 27 accompanying the operation of the brake pedal 15 is interposed between the spool 27 and the piston 36 (between the spool 27 and the transmission rod 30 in the present embodiment). And when the operation of the brake pedal 15 reaches a preset operation position, only the spool 27 moves and the piston 36 does not move, and the brake pedal is operated beyond the set operation position. In some cases, the spool 27 and the piston 36 move in conjunction with each other. Thus, when the brake pedal 15 is operated, the second brake means is actuated first, and then the first brake means is actuated, whereby the burden on the first brake means during travel braking is imposed. Can be reduced. Moreover, by changing the urging force of the first spring 31, the piston 27 starts to move, that is, the setting operation position of the brake pedal 15 at which the first brake means starts operating can be changed. Thus, the interlocking relationship between the first brake means and the second brake means accompanying the operation of the brake pedal 15 can be easily changed.

  The brake operating device 17 includes a push member 26 that transmits an operation of the brake pedal 15 to the spool 27 when pressed by a pressing roller 25 provided on the brake pedal 15. It is arranged coaxially with the spool 27 and the piston 36. Thus, the operation of the brake pedal 15 can be transmitted to the spool 27 with a simple structure, which can contribute to the simplification of the structure of the brake actuator 17.

  Further, a brake pedal 15 is integrally assembled with the brake operating device 17. Thereby, the brake pedal 15 is attached at the same time by attaching the brake operating device 17 to the vehicle body, and adjustment of the positional relationship between the brake operating device 17 and the brake pedal 15 becomes unnecessary at the time of attaching to the vehicle body. This can greatly contribute to the improvement of workability in the installation work.

  Of course, the present invention is not limited to the above embodiment. For example, in the above embodiment, the first spring 31 is interposed between the spool 27 and the transmission rod 30. The transmission rod 30 and the piston 36 may be interposed. In the present embodiment, the transmission rod 30 is separate from the spool 27 and the piston 36, but may be formed integrally with the spool 27 or the piston 36.

  The present invention relates to a work vehicle such as a wheel loader equipped with an HST travel drive device. As a brake device, the first brake means using a master cylinder and the second brake means using a control valve are provided. It can be used when providing.

DESCRIPTION OF SYMBOLS 1 Hydraulic pump 4 Hydraulic motor 5 Wheel 10 Capacity control circuit 14 Inching oil path 15 Brake pedal 16 Inching valve 17 Brake actuator 18 Master cylinder 19 Service brake 25 Press roller 26 Push member 27 Spool 31 First spring 36 Piston

Claims (5)

  Brake output from a master cylinder as a brake device that brakes the travel of the work vehicle in a work vehicle having an HST travel drive device that drives wheels by a hydraulic motor connected to a variable displacement hydraulic pump in a closed circuit The first brake means that operates by pressure to apply braking force to the wheels and the control valve connected to the displacement control circuit of the variable displacement hydraulic pump reduces the pump discharge flow rate and applies braking force to the hydraulic motor. In providing two brake means and a brake pedal operated to actuate the first and second brake means, a brake actuating device in which the control valve and the master cylinder are incorporated as one unit is provided, The control valve and the master cylinder are operated in conjunction with the operation of the brake pedal. Braking device in a work vehicle according to claim.   2. The brake operating device according to claim 1, wherein the spool constituting the control valve and the piston constituting the master cylinder are coaxially arranged, and the spool is moved in accordance with the operation of the brake pedal. The brake device for a working vehicle is characterized in that the first brake means is activated by the movement of the piston and the movement of the piston in conjunction with the movement of the spool.   In Claim 2, between the spool and the piston, an ammo that shrinks due to the movement of the spool accompanying the operation of the brake pedal is interposed, and when the operation of the brake pedal reaches a preset operation position, only the spool is operated. And the piston does not move, and the spool and the piston move in conjunction with each other when the brake pedal is operated beyond the set operation position.   4. The brake operating device according to claim 2, further comprising a push member that transmits the operation of the brake pedal to the spool when pushed by the member on the brake pedal side, and the push member is arranged coaxially with the spool and the piston. The brake device in the working vehicle characterized by the above-mentioned.   The brake device for a working vehicle according to any one of claims 1 to 4, wherein a brake pedal is integrally assembled with the brake operation device.

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