Work vehicle

Abstract

To make it possible to obtain release timing of a parking brake with good accuracy in a work vehicle that performs actuation and release of the parking brake by operation displacement of an operation tool which performs shift operation.SOLUTION: A work vehicle comprises: a left operation tool 12a which adjusts a speed of a left rear wheel by displacement along a first route; a right operation tool 12b which adjusts a speed of a right rear wheel by displacement along a second route; a parking brake operation part 71 which operates a parking brake 16 in response to displacement of a third route branched from the first route of the left operation tool 12 and displacement of a fourth route branched from the second route of the right operation tool 12b; a parking brake release part 72 which releases operation of the parking brake 16 in response to releasing displacement of the left operation tool 12a along the first route from a neutral position or releasing displacement of the right operation tool 12b along the second route from a neutral position; a release displacement calculation part 73 which calculates the releasing displacement; and a calibration part 74 which calibrates the release displacement calculation part 73 at real time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work vehicle equipped with a left operating tool for adjusting the speed of the left rear wheel, a right operating tool for adjusting the speed of the right rear wheel, and a parking brake. [Background technology]

[0002] Patent Document 1 discloses a riding brush cutter as a work vehicle that is equipped with a left travel lever for adjusting the speed of the left rear wheel, a right travel lever for adjusting the speed of the right rear wheel, and a brake device. The brake device is linked to a brake lock mechanism that can be switched between a locked state (which keeps the brake device engaged) and an unlocked state by operating the brake lever or brake pedal.

[0003] Patent Document 2 discloses a zero-turn mower as a work vehicle equipped with a pair of left and right control levers that can be independently operated to a forward speed position, a neutral position, a reverse speed position, and a parking position. The forward speed position, the neutral position, and the reverse speed position are set along a longitudinal displacement path of the control lever. The control lever can also be displaced laterally from an intermediate position, perpendicular to the longitudinal direction, with the terminal position of this lateral displacement set as the parking position. When the control lever reaches the parking position, and the drive wheels are in a predetermined state, the parking brake is activated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 6,708,805 [Patent Document 2] U.S. Patent No. 10,974,597 Summary of the Invention [Problem to be solved by the invention]

[0005] In the work vehicle of Patent Document 1, the parking brake must be activated or released by directly operating the brake lever or brake pedal. Automatic operation of the parking brake, such as by operating a separate operating tool, is not considered. In the work vehicle of Patent Document 2, the parking brake is automatically activated by displacing the control lever to a parking position set on a branch path branching from the neutral position of the gear shift path. While not described in detail, releasing the parking brake involves moving the control lever away from the parking position. If the parking brake is released by moving the control lever away from this parking position, there is a possibility that the vehicle may start moving at that moment if parked in an unstable location. Furthermore, a problem inherent to detection sensors is that if there is significant variation in the detection of the longitudinal lever leaving the parking position, the tolerance range for the release detection must be increased, which results in the problem of inaccurate timing for releasing the parking brake.

[0006] An object of the present invention is to obtain accurate timing for releasing the parking brake in a work vehicle in which the parking brake is activated and released by the operational displacement of an operating tool that performs a gear change operation. [Means for solving the problem]

[0007] The work vehicle according to the present invention includes a front wheel unit, a rear wheel unit having a left rear wheel and a right rear wheel, a variable running power supply unit that supplies rotational power independently to the left rear wheel and the right rear wheel, a left operating tool that adjusts the speed of the rotational power supplied from the variable running power supply unit to the left rear wheel by displacement along a first path that is a speed change path, a right operating tool that adjusts the speed of the rotational power supplied from the variable running power supply unit to the right rear wheel by displacement along a second path that is a speed change path, a parking brake provided on the variable running power supply unit, and a retracted position of a third path branching off from the first path of the left operating tool. a parking brake actuation unit that actuates the parking brake in response to a displacement of the left operating tool from the neutral position (branch point JP) along the first path and a displacement of the right operating tool from the neutral position (branch point JP) along the second path, while the parking brake is in an actuated state, and a parking brake release unit that releases the actuation of the parking brake in response to a release displacement of the left operating tool from the neutral position (branch point JP) along the first path and / or a release displacement of the right operating tool from the neutral position (branch point JP) along the second path; a release displacement calculation unit that calculates the release displacement; and a calibration unit that calibrates the release displacement calculation unit in real time.

[0008] With this configuration, the release displacement calculation unit, which calculates the release displacement in response to either or both of the release displacement from the neutral position of the left operating tool along the first path and the release displacement from the neutral position of the right operating tool along the second path, is calibrated in real time by the calibration unit. In other words, the calculation of the release displacement, which serves as the base value for releasing the parking brake, is calibrated each time. When the operator starts driving the parked work vehicle again, the release displacement is always calculated based on new calibration results (e.g., zero point adjustment), so the timing to release the parking brake can be obtained with precision.

[0009] In the present invention, the release displacement calculation unit calculates the release displacement from detection values ​​of displacement detection sensors that detect displacements of the left operating tool and the right operating tool along the shift path from the neutral position, and the calibration unit uses detection values ​​of the displacement detection sensors acquired when the left operating tool and the right operating tool are released from the retracted position as release detection values ​​and performs calibration using the release detection values ​​as the zero point. In this configuration, the release displacement, which is a displacement of a predetermined distance from the neutral position on the first path or the second path, is calculated using detection values ​​from the displacement detection sensors that detect displacement of the operating tool on the first path or the second path. To accurately detect the release displacement, it is preferable that the detection value of the displacement detection sensor at the neutral position (reference position) of the operating tool is zero. However, the detected value deviates from zero due to inherent errors of the detection sensors and environmental conditions such as temperature. To accommodate this deviation, it is necessary to provide a predetermined tolerance for the value that determines the release displacement. Such a tolerance reduces the detection accuracy of the release displacement. However, in this configuration, a zero point adjustment is performed in which the separation detection value of the displacement detection sensor is set to the zero point, so there is no need to provide an allowable range for the value that determines the release displacement, and high detection accuracy is achieved in each parking brake release process.

[0010] Furthermore, in the present invention, the arrival at and departure from the retracted positions of the left operating tool and the right operating tool are detected by limit switches, and the calibration unit calibrates the release displacement calculation unit by using the detection value of the displacement detection sensor when the limit switch detects the departure or a predetermined displacement after the departure is detected as the zero point. In this configuration, the arrival at and departure from the retracted positions of the operating tools are detected by limit switches. Furthermore, the detection value of the displacement detection sensor acquired when the departure from the retracted position of the operating tool or a predetermined displacement after the departure is detected is used as the departure detection value in the release displacement calculation unit, so that the calibration unit performs zero point adjustment at a stable timing.

[0011] In the present invention, the dislocation of the left operating tool along the third path and the dislocation of the right operating tool along the fourth path are configured to expand the dislocation passage for the driver to dismount. With this configuration, the dislocation passage for the driver to dismount is expanded by the dislocation of the left operating tool along the third path and the dislocation of the right operating tool along the fourth path, allowing the driver to dismount smoothly. Since the parking brake is activated by the displacement of the left operating tool along the third path and the displacement of the right operating tool along the fourth path, which the driver necessarily performs to dismount, the driver is prevented from forgetting to apply the parking brake when dismounting. Furthermore, the parking brake is also prevented from being released after the driver has dismounted. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a left side view showing the entire riding brush cutter. FIG. [Figure 2] 1 is a plan view showing the entire riding type brush cutter. FIG. [Figure 3] FIG. 3 is a functional block diagram of a control system related to the operating lever unit. [Figure 4] FIG. 4 is a plan view of a guide unit that guides an operating lever. [Figure 5] FIG. 10 is a functional block diagram of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described below with reference to the drawings. In the following description, with respect to the traveling body of a riding brush cutter (an example of a "work vehicle"), the direction of arrow F shown in Figures 1 and 2 will be referred to as the "front of the body," the direction of arrow B as the "rear of the body," the direction of arrow U shown in Figure 1 as the "upper side of the body," the direction of arrow D as the "lower side of the body," the direction of arrow L shown in Figure 2 as the "left side of the body," and the direction of arrow R as the "right side of the body."

[0014] This riding brush cutter is also known as a zero-turn mower, and as shown in FIGS. 1 and 2, its traveling body is equipped with a front wheel unit 1 having a pair of left and right front wheels that can rotate freely, and a rear wheel unit 2 having a left rear wheel and a right rear wheel that can be driven. The traveling body has a body frame 8. The front wheels are configured as caster wheels. A driver's section 4 with a driver's seat 3 is formed at the front of the traveling body. A traveling motor unit 5 consisting of a left motor and a right motor that independently supply rotational power to the left rear wheel and the right rear wheel is provided below the driver's section 4. A battery pack 6 that supplies power to the traveling motor unit 5 is provided at the rear of the traveling body. A brush cutter 7 is provided between the front wheel unit 1 and the rear wheel unit 2. The brush cutter 7 is supported on the body frame 8 via a link mechanism 9 that operates to raise and lower the brush cutter 7 relative to the traveling body. The grass cutting device 7 is provided with a cutting blade housing 10, and a cutting blade 11 provided inside the cutting blade housing 10 so as to be rotatable around a support shaft (not shown) extending in the vertical direction of the vehicle body.

[0015] 1 and 2, the driver's section 4 is provided with an operating lever unit 12 as a control device for adjusting the speed and direction of the traveling vehicle body. A left operating lever 12a (an example of a left operating tool) and a right operating lever 12b (an example of a right operating tool) that constitute the operating lever unit 12 are located on either side of the driver's seat 3. The driver gets in or out of the vehicle by passing between the left operating lever 12a and the right operating lever 12b and stepping on a floor plate formed in front of the driver's seat 3.

[0016] As shown in FIG. 3, the left operating lever 12a and the right operating lever 12b each pivotally displace about a first pivot axis P1. This pivotal displacement is a displacement in the fore-and-aft direction of the vehicle body, and is referred to as a longitudinal displacement. Furthermore, the left operating lever 12a and the right operating lever 12b each also pivotally displace about a second pivot axis P2. This pivotal displacement is a displacement in the transverse direction of the vehicle body, and is referred to as a lateral displacement.

[0017] 3 and 4, a guide unit 40 is provided to guide the base ends of the left operating lever 12a and the right operating lever 12b to ensure stable displacement (swing) of the operating lever unit 12. The guide unit 40 is a plate structure, and has formed on its upper surface a vertical guide slot 41 that guides the vertical displacement of the left operating lever 12a or the right operating lever 12b, and a horizontal guide slot 42 that guides the lateral displacement of the left operating lever 12a or the right operating lever 12b. The vertical guide slot 41 is connected to the horizontal guide slot 42 at its center.

[0018] As shown in FIG. 4 , the shift path (displacement path) of the left operating lever 12a, which is guided by the vertical guide slot 41 for vertical displacement, is referred to as the first path L1, and the shift path (displacement path) of the right operating lever 12b, which is guided by the vertical guide slot 41 for vertical displacement, is referred to as the second path L2. The displacement path of the left operating lever 12a, which is guided by the lateral guide slot 42 for horizontal displacement, is referred to as the third path L3, and the displacement path of the right operating lever 12b, which is guided by the lateral guide slot 42 for horizontal displacement, is referred to as the fourth path L4. The first path L1 and the third path L3 are connected at a branch point JP, and the second path L2 and the fourth path L4 are connected at the branch point JP. The first path L1 and the third path L3 are approximately perpendicular to each other at the branch point JP, and the second path L2 and the fourth path L4 are approximately perpendicular to each other at the branch point JP.

[0019] 3, a potentiometer 13 is provided near the base end of the left operating lever 12a as a vertical displacement detection sensor that detects the vertical displacement of the left operating lever 12a along the first path L1. Similarly, a potentiometer 13 is provided near the base end of the right operating lever 12b as a vertical displacement detection sensor that detects the vertical displacement of the right operating lever 12b along the second path L2. Each potentiometer 13 is connected to the control device 50. When the parking brake 16 is activated, part of the vertical displacement of the left operating lever 12a and the right operating lever 12b from the branch point JP is used as a release displacement that releases the operation of the parking brake 16.

[0020] Furthermore, a limit switch 14 is provided near the base end of the left operating lever 12a to detect when the left operating lever 12a is at a specific position (first detection position) set on the third path L3. Similarly, a limit switch 14 is provided near the base end of the right operating lever 12b to detect when the right operating lever 12b is at a specific position (second detection position) set on the fourth path L4. Each limit switch 14 is connected to the control device 50.

[0021] A driving motor unit 5 that supplies rotational power to the rear wheel unit 2 is connected to the control device 50 via a motor driver unit 15. The driving motor unit 5 includes a left motor that supplies rotational power to the left rear wheel and a right motor that supplies rotational power to the right rear wheel. The motor driver unit 15 includes a left motor driver 15a for the left motor and a right motor driver 15b for the right motor. A control signal from the control device 50 to the motor driver unit 15 is generated by a wheel control unit 60 built in the control device 50.

[0022] The control device 50 controls the rotation of the traveling motor unit 5 based on the vertical displacement of the operation lever unit 12. Specifically, the further the left operation lever 12a is displaced forward from the branch point JP on the first path L1, the higher the forward rotation speed of the left rear wheel, and the further the left operation lever 12a is displaced rearward from the branch point JP on the first path L1, the higher the reverse rotation speed of the left rear wheel. Similarly, the further the right operation lever 12b is displaced forward from the branch point JP on the second path L2, the higher the forward rotation speed of the right rear wheel, and the further the right operation lever 12b is displaced rearward from the branch point JP on the second path L2, the higher the reverse rotation speed of the left rear wheel. The positions of the branch points JP of the left operation lever 12a and the right operation lever 12b are neutral positions, which are neutral states in which no power is supplied.

[0023] The branch point JP functions as a neutral position where the transmission of rotational power to the rear wheel unit 2 is zero, so when the left operating lever 12a is positioned on the third path L3, the transmission of rotational power to the left rear wheel is zero and the neutral state is maintained. Similarly, when the right operating lever 12b is positioned on the fourth path L4, the transmission of rotational power to the left rear wheel is zero and the neutral state is maintained.

[0024] As shown in FIG. 3, a parking brake 16 is interposed between the traveling motor unit 5 and the rear wheel unit 2. The parking brake 16 includes a left brake interposed between the left motor and the left rear wheel, and a right brake interposed between the right motor and the right rear wheel. The parking brake 16 and the control device 50 are connected via a brake driver 17. A control signal from the control device 50 to the brake driver 17 is generated by a parking brake control unit 70 built in the control device 50. In this embodiment, the parking brake 16 is configured as an electromagnetic brake.

[0025] In this embodiment, the variable rotational power traveling power supply unit PSU, which supplies rotational power to the rear wheel unit 2 based on the displacement position of the operating lever unit 12, is made up of the traveling motor unit 5, the parking brake 16, and a transmission mechanism (not shown). The transmission mechanism includes a transmission shaft and a transmission gear.

[0026] The parking brake control unit 70 includes a parking brake activation unit 71 , a parking brake release unit 72 , a release displacement calculation unit 73 , and a calibration unit 74 .

[0027] When the left operating lever 12a of the operating lever unit 12 reaches a first detection position (parking brake actuated position) which is a retracted position and the left limit switch 14 is turned ON, and the right operating lever 12b reaches a second detection position (parking brake actuated position) which is also a retracted position and the right limit switch 14 is turned ON, the parking brake control unit 70 activates the left and right brakes of the parking brake 16 (brake ON). As a result, the traveling vehicle body enters a parking state in which the parking brake 16 is actuated (parking brake actuated state).

[0028] As shown in FIG. 2, the left operating lever 12a of the operating lever unit 12 rises from the left side of the driver's seat 3 and bends toward the vehicle centerline in the transverse direction, with a grip formed in the tip region of this bent portion. Similarly, the right operating lever 12b of the operating lever unit 12 rises from the left side of the driver's seat 3 and bends toward the vehicle centerline in the transverse direction, with a grip formed in the tip region of this bent portion. In other words, the grip of the left operating lever 12a and the grip of the right operating lever 12b face each other, obstructing the exit path when the driver exits the driver's seat 3. As the left operating lever 12a moves along the third path L3 and the right operating lever 12b moves along the fourth path L4, the distance between the grip of the left operating lever 12a and the grip of the right operating lever 12b increases. In particular, when the left operating lever 12a and the right operating lever 12b are displaced to positions that turn on the respective limit switches 14, an exit passage for the driver to exit the vehicle is opened. When the driver exits the vehicle, the left operating lever 12a is displaced along the third path L3, and the right operating lever 12b is displaced along the fourth path L4, at which point the parking brake 16 is activated.

[0029] The parking brake release unit 72 releases the operation of the parking brake 16 in response to the left operation lever 12a or the right operation lever 12b leaving the parking brake applied position and reaching the branch point JP, and further in response to either or both of a release displacement of the left operation lever 12a from the neutral position along the first path L1 and a release displacement of the right operation lever 12b from the neutral position along the second path L2. The release displacement calculation unit 73 calculates a release displacement, which is the displacement of the left operation lever 12a and the right operation lever 12b from the branch point JP, based on the detection value of the potentiometer 13. The calibration unit 74 calibrates the release displacement calculation unit 73 in real time using the detection value (release detection value) of the potentiometer 13 when the operation lever unit 12 leaves the parking brake applied position.

[0030] An example of a control procedure for releasing the parking brake 16 by the parking brake control unit 70 is as follows. (#1) A release detection signal is sent from the limit switch 14 to the parking brake control unit 70, indicating that the left operating lever 12a of the operating lever unit 12 has released from the first detection position (parking brake actuated position) on the third path L3, or that the right operating lever 12b has released from the second detection position (parking brake actuated position) on the fourth path L4. (#2) In response to receiving the separation detection signal, the calibration unit 74 records the detection values ​​of each potentiometer 13 that detects the vertical displacement of the operating lever unit 12 (left operating lever 12a and right operating lever 12b) as separation detection values. (#3) Furthermore, the calibration unit 74 calibrates the release displacement calculation program of the release displacement calculation unit 73 so that the release detection value is regarded as a reference value (zero point) (zero point calibration). (#4) The release displacement calculation unit 73 calculates the release displacement using a calibrated release displacement calculation program (i.e., a program that determines the difference between the reference value, which is the separation detection value, and the detection value of each potentiometer 13 as the release displacement). (#5) When the calculated release displacement reaches a preset release displacement value, the parking brake release unit 72 sends a release command to the brake driver 17 to release the parking brake 16. The release displacement value may be adjustable or may be fixed. In this case, the release displacement value is preferably a value that causes the traveling motor unit 5 to supply slight rotational power to the rear wheel unit 2 in order to prevent the traveling vehicle body from moving slightly when the parking brake 16 is released.

[0031] [Another embodiment] (1) In the control procedure for releasing the parking brake 16 described above, the detection values ​​of the potentiometers 13 at the time when the operating lever unit 12 is released from the parking brake applied position are recorded as the release detection values. Alternatively, the detection values ​​of the potentiometers 13 at the time when the operating lever unit 12 is laterally displaced a predetermined distance (maximum value being the distance to the branch point JP) from the parking brake applied position may be recorded as the release detection values. To realize this alternative embodiment, as shown in FIG. 5 , a lateral potentiometer 140 is provided for detecting lateral displacement (displacement along the third path L3 and the fourth path L4), which is the pivotal displacement of the left operating lever 12a and the right operating lever 12b of the operating lever unit 12 about the second pivot axis P2. The lateral potentiometer 140 is connected to the control device 50, and the parking brake control unit 70 can sequentially detect the lateral displacement of the left operating lever 12a and the right operating lever 12b. Therefore, the parking brake control unit 70 can release the parking brake 16 by detecting a lateral displacement of the operating lever by a predetermined angle from the neutral position (branch point JP).

[0032] (2) This is a modified example of the other embodiment of (1), and the detection value of each potentiometer 13 at the time of detecting a lateral displacement of the operating lever unit 12 that exceeds a predetermined displacement rate from the parking brake applied position is recorded as a release detection value. The displacement rate is calculated by a differential calculator of the parking brake control unit 70 to which a signal from the lateral potentiometer 140 is input, and the predetermined displacement rate is usually set based on the operating behavior of the operating lever unit 12 when the driver tries to start driving from a parked state.

[0033] (3) In the control procedure for releasing the parking brake 16 described above, the parking brake 16 is released when the calculated release displacement reaches a preset release displacement value. Alternatively, the parking brake 16 may be released in response to either or both of a displacement of the left operating lever 12a from the neutral position (branch point JP) along the first path L1 that exceeds a predetermined displacement rate, or a displacement of the right operating lever from the neutral position along the second path L2 that exceeds a predetermined displacement rate. This displacement rate is calculated by a differential calculator in the parking brake control unit 70 to which a signal from the potentiometer 13 is input, and the predetermined displacement rate is usually set based on the operation behavior of the operating lever unit 12 when the driver attempts to start driving from a parked state.

[0034] (4) In the above-described embodiment, an example was shown in which the front wheel unit 1 and the rear wheel unit 2 were provided as the traveling device, and the traveling motor unit 5 was provided as a drive device that drives the traveling device, but this is not limited to this. For example, a crawler-type traveling device or a traveling device that combines a mini crawler and wheels may be provided. Also, a continuously variable transmission that receives engine power and changes the speed of the input power before transmitting it to the traveling device to drive the traveling device may be provided. (5) In the above-described embodiment, the parking brake 16 is configured as an electromagnetic brake. However, other brake structures may be adopted instead, such as a mechanical brake operated by an electric actuator. (6) In the above-described embodiment, the operating tool is an operating lever that swings around a swing fulcrum. However, other types of operating tools, such as a sliding type operating tool, may also be used. (7) In the above-described embodiment, limit switch type or potentiometer type detection devices are used to detect the behavior of each path of the operating lever unit 12, but detection devices such as magnetic detection devices or optical detection devices may also be used. [Industrial Applicability]

[0035] The present invention can be applied to various types of work vehicles, such as transport vehicles, in addition to brush cutters. [Explanation of symbols]

[0036] 1: Front wheel unit 2: Rear wheel unit 5: Travel motor unit 12: Operating lever unit 12a: Left operating lever 12b: Right operating lever 13: Potentiometer 14: Limit switch 16: Parking brake 17: Brake driver 50: Control device 60: Wheel control unit 70: Parking brake control unit 71: Parking brake actuator 72: Parking brake release part 73: Release displacement calculation unit 74: Calibration section L1: First pathway L2: Second pathway L3: Third pathway L4: 4th pathway

Claims

1. The front wheel unit, a rear wheel unit having a left rear wheel and a right rear wheel; a variable driving power supply unit that supplies rotational power independently to the left rear wheel and the right rear wheel; a left operating tool that adjusts the speed of rotational power supplied from the variable running power supply unit to the left rear wheel by displacement along a first path that is a speed change path; a right operating tool that adjusts the speed of the rotational power supplied from the variable running power supply unit to the right rear wheel by displacement along a second path that is a speed change path; a parking brake provided in the variable driving power supply unit; a parking brake actuation unit that actuates the parking brake in response to displacement of the left operating tool to a third path branched from the first path to a retracted position and displacement of the right operating tool to a fourth path branched from the second path to a retracted position; a parking brake release unit that releases the operation of the parking brake in response to either or both of a release displacement of the left operating tool from the neutral position along the first path and a release displacement of the right operating tool from the neutral position along the second path when the parking brake is in an actuated state; a release displacement calculation unit that calculates the release displacement; a calibration unit that calibrates the release displacement calculation unit in real time; A work vehicle equipped with:

2. 2. The work vehicle according to claim 1, wherein the release displacement calculation unit calculates the release displacement from a detection value of a displacement detection sensor that detects displacement of the left operating tool and the right operating tool from the neutral position along the shift path, and the calibration unit uses the detection value of the displacement detection sensor obtained when the left operating tool and the right operating tool are released from the retracted position as a release detection value, and performs calibration such that the release detection value is set as a zero point.

3. 3. The work vehicle according to claim 2, wherein the arrival of the left operating tool and the right operating tool at the retracted position and the departure of the left operating tool from the retracted position are detected by limit switches, and the calibration unit calibrates the release displacement calculation unit by setting the detection value of the displacement detection sensor at the time of detection of the departure by the limit switch or at a predetermined displacement after the detection of the departure as the zero point.

4. 2. The work vehicle according to claim 1, wherein a dismounting passage for a driver to dismount is expanded by displacement of the left operating tool along the third path and displacement of the right operating tool along the fourth path.

Images