Patent Description:
In a work vehicle such as a tractor or a seedling transplantor that performs work by transmitting drive to a work machine by a power take off (PTO) shaft, a technique described in PTL <NUM> is known.

PTL <NUM> describes a technique in which, in a work vehicle for spreading a snow melting agent, a forward movement and a backward movement are switched by a forward-reverse lever, rotation of a drive wheel can be detected by a rotation speed sensor, and transmission of drive to a PTO shaft is restricted when the vehicle is stopped (when a rotation speed of the drive wheel is zero) or when the forward-reverse lever is operated to a reverse side, and thus the work machine is operated by transmitting the drive to the PTO shaft only during the forward movement.

PTL <NUM> discloses a working vehicle having the features in the preamble of claim <NUM>. PTL <NUM> and PTL <NUM> disclose further prior art.

In the related-art technique described in PTL <NUM>, determination on the operation of the forward-reverse lever to the reverse side is performed, but the work vehicle may have a configuration in which forward and reverse operations are performed by a forward pedal and a reverse pedal instead of including the forward-reverse lever, and the technique cannot be implemented in a configuration not including the forward-reverse lever.

In addition, in the work vehicle capable of moving forward and backward, a rotation speed of an engine is highly important to be displayed in relation to work, but a vehicle speed that varies due to a speed change or a switch between on and off of a clutch is less important to be displayed than the rotation speed of the engine. Accordingly, there are work vehicles that do not have a function of displaying the vehicle speed, and there are also work vehicles that do not include a vehicle speed sensor that detects rotation of an axle. Therefore, in a work vehicle that does not include a relatively expensive vehicle speed sensor, it is not possible to implement the configuration in PTL <NUM> in which a vehicle speed is detected and the transmission of the drive to the PTO shaft is restricted.

A technical object of the invention is to provide a work vehicle that does not include a forward-reverse lever and is capable of stopping transmission of drive to a PTO shaft at a low cost when the vehicle is stopped or is moving backward.

The above problems are solved by the subject-matter of claim <NUM>.

The invention described in claim <NUM> is a work vehicle (<NUM>) including:.

The advantageous embodiment of the invention described in claim <NUM> is the work vehicle.

According to the invention, in the work vehicle (<NUM>) including the forward pedal (<NUM>) and a reverse pedal (<NUM>) and not including a forward-reverse lever, it is possible to determine, even when an expensive vehicle speed sensor is not provided, a forward movement of the work vehicle (<NUM>) using a relatively low-cost switch and to stop the transmission of drive to the PTO shaft.

In addition, the switch can be compactly installed, and a space can be saved as a whole.

<FIG> is a view illustrating a tractor as an example of a work vehicle according to an embodiment.

In <FIG>, a snow removal tractor <NUM> as an example of the work vehicle according to the invention includes front wheels <NUM> and <NUM> and rear wheels <NUM> and <NUM> at front and rear portions of a traveling vehicle body 1a, and is configured to appropriately decrease rotational power of an engine E, which is mounted in an engine room <NUM> at the front portion of the traveling vehicle body, by a transmission in a transmission case <NUM> and transmit the rotational power to the front wheels <NUM> and <NUM> and the rear wheels <NUM> and <NUM>. The engine room <NUM> is covered with a bonnet <NUM>. A work machine such as an agent spreading machine <NUM> for spreading agents (a snow melting agent, an antifreezing agent, or the like) on a road surface behind the tractor <NUM> is attached to the rear portion of the vehicle body of the tractor <NUM>, and the work machine is driven by power transmitted by a rear PTO shaft <NUM>. A snow removal brush <NUM> as an example of the work machine is attached to the front portion of the vehicle body. The snow removal brush <NUM> is implemented by a rotary brush that flicks off snow on the road surface to lateral sides. The snow removal brush <NUM> is driven by power transmitted by a mid PTO shaft <NUM>.

In the present specification, left and right of the tractor <NUM> in a forward direction are referred to as a left side and a right side respectively, the forward direction is referred to as a front side, and a reverse direction is referred to as a rear side.

A cabin <NUM> is supported on an upper portion of the traveling vehicle body 1a. Inside the cabin <NUM>, a driver seat <NUM> is disposed at a position on an upper portion of the transmission case <NUM>, and a steering wheel <NUM>, a parking brake (not illustrated), and the like are disposed in front of the driver seat <NUM>. A display panel such as a speed meter (not illustrated), various switches (not illustrated) for operations, and the like are disposed in front of the driver seat <NUM>. Traveling operation tools such as a brake pedal <NUM> and accelerator pedals <NUM> including a forward pedal and a reverse pedal are disposed at a front lower portion of the driver seat <NUM>.

In <FIG>, a hydraulic cylinder case <NUM> is provided above a rear portion of the transmission case <NUM>, and lift arms <NUM> and <NUM> are pivotally attached to both left and right sides of the hydraulic cylinder case <NUM>. The lift arms <NUM> and <NUM> and lower links <NUM> and <NUM> are coupled with lift rods <NUM> and <NUM> interposed therebetween, respectively, and the agent spreading machine <NUM> as an example of the work machine is coupled to rear portions of the lower links <NUM> and <NUM>.

When hydraulic oil is supplied to a hydraulic cylinder 14a accommodated in the hydraulic cylinder case <NUM>, the lift arms <NUM> and <NUM> are pivoted upward, and the work machine (the agent spreading machine) <NUM> is raised via the lift rods <NUM> and <NUM>, the lower links <NUM> and <NUM>, and the like. In contrast, when the hydraulic oil in the hydraulic cylinder 14a is discharged into the transmission case <NUM> which also serves as a hydraulic tank, the lift arms <NUM> and <NUM> descend.

A position sensor SN1 for detecting an inclination angle of each lift arm <NUM>, that is, an up and down movement of the work machine <NUM> is disposed at a base end portion of the lift arm <NUM>.

As the work machine attached to the rear portion of the traveling vehicle body 1a, that is, the work machine to which drive is transmitted from the rear PTO shaft <NUM>, examples include, in addition to the agent spreading machine, agricultural work machines such as a rotary cultivator, a plow, a seeding machine, a seedling transplanter, a fertilizer spreading machine, and a pesticide spraying machine which are used for agricultural work.

As the work machine attached to the front portion of the traveling vehicle body 1a, that is, the work machine to which drive is transmitted from the mid PTO shaft <NUM>, in addition to the snow removal brush <NUM>, a mower for lawn mowing, a loader capable of accommodating and carrying a sample, grass, sand, crop, or the like in a bucket, and the like can be used.

<FIG> is a view illustrating a main part including an engine, a main transmission, and pedals according to the embodiment.

<FIG> is a perspective view seen from a direction of an arrow III in <FIG>.

<FIG> is an enlarged view of switches in <FIG>.

<FIG> is a view illustrating a switch for forward movement detection.

<FIG> is a view illustrating a switch for neutral detection.

<FIG> is a perspective view of the switches and an attachment plate.

<FIG> is a view illustrating an attachment hole of the attachment plate.

In <FIG> and <FIG>, in the tractor <NUM> according to the embodiment, a hydraulic static transmission (HST) <NUM> as an example of the main transmission is disposed at a rear portion of the engine E. In <FIG>, illustration of portions and components not related to a description of the invention is omitted.

A forward pedal <NUM> and a reverse pedal <NUM> are disposed on a right side of the HST <NUM>.

The forward pedal <NUM> is a member for a driver to perform an operation by depressing with a foot to move the tractor <NUM> forward. The reverse pedal <NUM> is a member for the driver to perform an operation by depressing with the foot to move the tractor <NUM> backward.

A base end portion of the reverse pedal <NUM> is supported by a right end of an interlocking shaft <NUM>. The interlocking shaft <NUM> penetrates the HST <NUM> in a left-right direction and is rotatably supported by the HST <NUM>.

In <FIG>, a base end portion of the forward pedal <NUM> is supported by a right end portion of an interlocking sleeve <NUM>. The interlocking sleeve <NUM> has a cylindrical shape extending in the left-right direction, and the interlocking shaft <NUM> penetrates through an inside of the interlocking sleeve <NUM>. One end portion of a forward link arm <NUM> is rotatably coupled to a left end portion of the interlocking sleeve <NUM>. The other end portion of the forward link arm <NUM> is coupled to a trunnion shaft <NUM> of the HST <NUM>.

The trunnion shaft <NUM> is a known member for changing an inclination angle of a swash plate (not illustrated) inside the HST <NUM>. By controlling an inclination angle of the trunnion shaft <NUM>, it is possible to move forward (forward rotation) or move backward (reverse rotation) and change a speed (change of a rotational speed).

One end portion of a reverse link arm <NUM> is rotatably coupled to the interlocking shaft <NUM> at a position leftward than the left end portion of the interlocking sleeve <NUM>. The other end portion of the reverse link arm <NUM> is coupled to the trunnion shaft <NUM> of the HST <NUM>.

In <FIG>, a forward movement detection cam <NUM> as an example of an interlocking portion and a neutral detection cam <NUM> as an example of a second interlocking portion are disposed at a left end portion of the interlocking shaft <NUM>. The forward movement detection cam <NUM> and the neutral detection cam <NUM> are disposed adjacent to each other in an axial direction of the interlocking shaft <NUM>. Therefore, an installation space can be saved as compared with a case where the two cams <NUM> and <NUM> are installed apart from each other.

In <FIG>, the forward movement detection cam <NUM> according to the embodiment is a substantially fan-shaped plate member, and a diameter from the interlocking shaft <NUM> is formed such that an upper portion 211a has a diameter larger than that of a lower portion 211b.

In <FIG>, the neutral detection cam <NUM> according to the embodiment is a substantially fan-shaped plate member, a diameter from the interlocking shaft <NUM> is formed such that an upper portion 212a and a lower portion 212b have the same diameter and an intermediate portion 212c between the upper portion 212a and the lower portion 212b has a diameter smaller than that of the upper portion 212a and the lower portion 212b. Therefore, the neutral detection cam <NUM> has a fan shape in which a portion at the intermediate portion 212c is recessed with respect to a peripheral direction of the neutral detection cam <NUM>.

A forward movement detection switch <NUM> as an example of a switch and a neutral detection switch <NUM> as an example of a second switch are disposed in front of the cams <NUM> and <NUM>.

The forward movement detection switch <NUM> and the neutral detection switch <NUM> are disposed adjacent to each other in the axial direction of the interlocking shaft <NUM> so as to correspond to the forward movement detection cam <NUM> and the neutral detection cam <NUM>.

The forward movement detection switch <NUM> includes a box-shaped switch main body 213a. A contact portion 213b protruding rearward is provided on a lower portion of a rear surface of the switch main body 213a. A forward plate spring portion 213c is disposed on a rear side of the switch main body 213a, and an upper end of the forward plate spring portion 213c is supported by the switch main body 213a. A forward cam follower 213d that can be brought into contact with a front surface (outer peripheral surface) of the forward movement detection cam <NUM> is provided at a lower end of the forward plate spring portion 213c.

The forward cam follower 213d is brought into contact with the outer peripheral surface of the forward movement detection cam <NUM> by an elastic force of the forward plate spring portion 213c. In the embodiment, a position, a shape, and a size of each member are set such that the forward plate spring portion 213c is not in contact with the contact portion 213b in a state in which the forward cam follower 213d is in contact with the small-diameter lower portion 211b, and the forward plate spring portion 213c is in contact with the contact portion 213b in a state in which the forward cam follower 213d is in contact with the large-diameter upper portion 211a. When the forward plate spring portion 213c and the contact portion 213b are in contact with each other, the forward plate spring portion 213c and the contact portion 213b are energized to turn on the forward movement detection switch <NUM>. When the forward plate spring portion 213c and the contact portion 213b are not in contact with each other, the forward movement detection switch <NUM> is turned off. The positions and the like of the members are set such that the forward cam follower 213d is in contact with a boundary portion 211c between the upper portion 211a and the lower portion 211b in a state in which the forward pedal <NUM> and the reverse pedal <NUM> are not depressed (a neutral state, a non-drive transmission state). A diameter of the boundary portion 211c is the same as that of the upper portion 211a and larger than that of the lower portion 211b.

The neutral detection switch <NUM> has a similar configuration as the forward movement detection switch <NUM>, and includes a switch main body 214a, a contact portion 214b, a neutral plate spring portion 214c, and a neutral cam follower 214d.

The neutral cam follower 214d is brought into contact with an outer peripheral surface of the neutral detection cam <NUM> by an elastic force of the neutral plate spring portion 214c. In the embodiment, a position, a shape, and a size of each member are set such that the neutral plate spring portion 214c is not in contact with the contact portion 214b in a state in which the neutral cam follower 214d is in contact with the small-diameter intermediate portion 212c, and the neutral plate spring portion 214c is in contact with the contact portion 214b in a state in which the neutral cam follower 214d is in contact with the large-diameter upper portion 212a or lower portion 212b. When the neutral plate spring portion 214c and the contact portion 214b are in contact with each other, the neutral plate spring portion 214c and the contact portion 214b are energized to turn on the neutral detection switch <NUM>. When the neutral plate spring portion 214c and the contact portion 214b are not in contact with each other, the neutral detection switch <NUM> is turned off. The positions and the like of the members are set such that the neutral cam follower 214d is in contact with the intermediate portion 212c in a state in which the forward pedal <NUM> and the reverse pedal <NUM> are not depressed (the neutral state, the non-drive transmission state).

In <FIG>, the forward movement detection switch <NUM> and the neutral detection switch <NUM> are supported on a left side wall of the HST <NUM> via an attachment plate <NUM>. The attachment plate <NUM> includes a plate-shaped switch support portion 216a, a connection portion 216b extending rightward from a lower end of the switch support portion 216a, and an attached portion 216c extending rearward from a right end of the connection portion 216b.

The forward movement detection switch <NUM> and the neutral detection switch <NUM> are supported by the switch support portion 216a. In the embodiment, the forward movement detection switch <NUM> and the neutral detection switch <NUM> having the similar configuration are disposed adjacent to each other, and as compared with a case where the two switches have different configurations or are disposed at separated positions, the two switches <NUM> and <NUM> can be supported by one attachment plate <NUM>, the configuration can be simplified, costs can be reduced, and an installation space can also be saved.

A pair of front and rear attachment holes 216d are formed in the attached portion 216c. The attachment plate <NUM> is supported on the left side wall of the HST <NUM> by a screw <NUM> passing through each of the attachment holes 216d. As illustrated in <FIG>, the attachment hole 216d according to the embodiment is an arc-shaped long hole along an arc centered on the interlocking shaft <NUM>. Therefore, when the positions of the switches <NUM> and <NUM> are finely adjusted, a positional relationship around the interlocking shaft <NUM> is easily adjusted.

In <FIG>, in the tractor <NUM> according to the embodiment, when neither the forward pedal <NUM> nor the reverse pedal <NUM> is depressed, the cam followers 213d and 214d are in contact with the boundary portion 211c and the intermediate portion 212c of the cams <NUM> and <NUM> respectively, the forward movement detection switch <NUM> is turned on, and the neutral detection switch <NUM> is turned off.

In <FIG>, when the forward pedal <NUM> is depressed, the interlocking sleeve <NUM> rotates in a direction indicated by a solid arrow Ya in <FIG>. As the interlocking sleeve <NUM> rotates, the forward link arm <NUM> moves in a direction of a solid arrow Ya, and the trunnion shaft <NUM> also rotates in a direction of a solid arrow Ya. Accordingly, the HST <NUM> outputs a rotational speed in the forward direction corresponding to a rotation amount of the trunnion shaft <NUM>. As the trunnion shaft <NUM> rotates, the reverse link arm <NUM> also moves in a direction of a solid arrow Ya, and the interlocking shaft <NUM> rotates in a direction of a solid arrow Ya.

In <FIG>, when the interlocking shaft <NUM> rotates in the direction of the solid arrow Ya, the two cams <NUM> and <NUM> also rotate in a direction of a solid arrow Ya. Therefore, the cam followers 213d and 214d are brought into contact with outer peripheral surfaces of the lower portions 211b and 212b of the cams <NUM> and <NUM> respectively, and both the forward movement detection switch <NUM> and the neutral detection switch <NUM> are turned off.

In <FIG>, when the reverse pedal <NUM> is depressed, the interlocking shaft <NUM> rotates in a direction indicated by a dashed arrow Yb in <FIG>. As the interlocking shaft <NUM> rotates, the reverse link arm <NUM> moves in a direction of a dashed arrow Yb, and the trunnion shaft <NUM> also rotates in a direction of a dashed arrow Yb. Accordingly, the HST <NUM> outputs a rotational speed in the reverse direction corresponding to a rotation amount of the trunnion shaft <NUM>.

In <FIG>, when the interlocking shaft <NUM> rotates in the direction of the dashed arrow Yb, the two cams <NUM> and <NUM> also rotate in a direction of a dashed arrow Yb. Therefore, the cam followers 213d and 214d are brought into contact with outer peripheral surfaces of the upper portions 211a and 212a of the cams <NUM> and <NUM> respectively, and both the forward movement detection switch <NUM> and the neutral detection switch <NUM> are turned on.

Accordingly, in the tractor <NUM> according to the embodiment, the forward movement detection switch <NUM> is turned off when the forward pedal <NUM> is depressed and a forward movement operation is performed, and the forward movement detection switch <NUM> is turned on when the reverse pedal <NUM> is depressed and a reverse movement operation is performed or in a neutral state in which neither the pedals <NUM> nor <NUM> is operated. The neutral detection switch <NUM> is turned off in the neutral state, and is turned on when both of the pedals <NUM> and <NUM> are operated (a forward moving state or a reverse moving state: a non-neutral state).

Therefore, based on detection results of the forward movement detection switch <NUM> and the neutral detection switch <NUM>, it is possible to determine whether the tractor <NUM> is moving forward, moving backward, or in the neutral state (the drive is not transmitted) based on a combination of ON and OFF states of the two switches <NUM> and <NUM>.

In the embodiment, the two switches including the forward movement detection switch <NUM> and the neutral detection switch <NUM> are used, but the neutral detection switch <NUM> and the neutral detection cam <NUM> are not necessarily required if it is only to determine whether the vehicle is moving forward, stopped, or moving backward. In the embodiment, the neutral state can be reliably detected by providing the neutral detection switch <NUM> and the neutral detection cam <NUM>.

In addition, the upper portion 212a of the neutral detection cam <NUM> may be set to have a smaller diameter similar to that of the lower portion 211b of the forward movement detection cam <NUM>, the neutral detection switch <NUM> may detect the neutral state, the forward movement, or the backward movement, and the forward movement/the backward movement/the neutral state may be determined based on a combination of the detection results of the two switches <NUM> and <NUM>.

Further, regarding the shape (diameter of the fan shape) of the cams <NUM> and <NUM>, a configuration for switching between the ON and OFF states as described above is described as an example, but is not limited thereto. For example, in the forward movement detection cam <NUM>, the upper portion 211a and the boundary portion 211c may have a smaller diameter while the lower portion 211b may have a larger diameter, and in the neutral detection cam <NUM>, the intermediate portion 212c may have a diameter larger than other portions.

In <FIG>, a control unit C of the tractor <NUM> according to the embodiment switches a PTO clutch <NUM> to a non-transmission state based on the detection results of the switches <NUM> and <NUM> when the tractor <NUM> is not in the forward moving state (in the neutral state or the reverse moving state), that is, when the forward movement detection switch <NUM> is turned on or the neutral detection switch <NUM> is turned off. The PTO clutch <NUM> is a clutch that is disposed in a power transmission path from the engine E to the rear PTO shaft <NUM> and that switches between transmission and non-transmission of the power. Since the PTO clutch <NUM> is known in the related art, a detailed description thereof will be omitted.

Claim 1:
A work vehicle (<NUM>) comprising:
a PTO shaft (<NUM>) configured to transmit power to a work machine (<NUM>);
a transmission (<NUM>);
a forward pedal (<NUM>) to be operated to move a vehicle body (1a) of the work vehicle (<NUM>) forward;
a switch (<NUM>); and
a PTO clutch (<NUM>), characterized in that
the switch (<NUM>) is configured to determine whether the forward pedal (<NUM>) is operated,
the PTO clutch (<NUM>) is configured to switch the power to the PTO shaft (<NUM>) to a non-transmission state when it is determined that the forward pedal (<NUM>) is not operated based on a determination result of the switch (<NUM>),
the forward pedal (<NUM>) is provided on one of left and right sides of the transmission (<NUM>), the left and right of the work vehicle (<NUM>) in a forward direction being referred to as a left side and a right side respectively, and
the switch (<NUM>) is provided on the other of the left and right sides of the transmission (<NUM>).