JPH01175578A - Steering device for skid steering vehicle - Google Patents

Abstract

PURPOSE:To enable pivot turning to be smoothly carried out, when pivots are turned, by steering a vehicle so that the direction of wheels approach the actual proceeding direction of the vehicle. CONSTITUTION:When pivot turning in the right direction is carried out, the steering lever 25b on the left side is tilted forward, and the steering lever on the right side is tilted backward. Then, a limit switch 27bf and a limit switch 27ar are pushed by the extended parts 26a, 26b of trunnion levers 23a, 23b so as to be turned ON. A control box 28, receiving this ON signal, sends a control signal so as to change over the positions of control valves in a hydraulic circuit 29 so that wheels 4 can be brought into the pivot turning condition. As a result, the piston rods of all the hydraulic cylinders 21 are retracted to steer the front and rear, right and left wheels 4, so that the directions of the wheels 4 agree with the proceeding direction, thereby smooth pivot turning can be enabled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a steering device for a skid steer vehicle such as a skid steer loader, and in particular, to a steering device for a skid steer vehicle such as a skid steer loader. This article relates to a device to facilitate the process.

[Prior Art] FIG. 5 of the drawings schematically shows a power transmission system of a typical skid steer vehicle. skid steer vehicle 1
is equipped with two independently controlled drive devices 2, and the output shaft 3 of each drive bag f2 is connected to the left and right wheels 4 via final reduction gears 5, respectively. The drive device 2 may include a hydrostatic type that generates hydraulic pressure with a hydraulic pump directly connected to the engine and drives a hydraulic motor using the hydraulic pressure, or an output shaft of the engine, a transmission device attached to it, and a clutch. Mechanical drive devices and the like are known.

Such a steering operation of the skid steer vehicle 1 is performed by tilting a steering lever (not shown) interlocked with the drive device 2 to generate a rotation difference between the left and right wheels 4.

[Problems to be Solved by the Invention] However, in the conventional skid steer vehicle 1 as described above, the direction of the wheels is fixed in the longitudinal direction of the vehicle, so when making a pivot turn, the direction of the wheels is fixed as shown in FIG. To,
A large sliding angle α occurs between the rotational direction of the wheel 4 (black arrow) and the actual traveling direction of the wheel 4 (white arrow).

This causes problems such as excessive resistance occurring between the tires and the road surface, excessive load on the engine, causing stalling or pitching, and increased tire wear.

An object of the present invention is to solve such problems.

[Means for Solving the Problems] Therefore, according to the present invention, each wheel is attached to the machine frame so as to be able to swing from side to side, and a drive means for swinging these wheels is provided to control the steering state. A detection means is provided for detecting the wheel, and a control means is provided for operating the drive means to change the direction of each of the wheels so as to reduce the sideslip angle when the detection means detects that the pot is in a turning state. It features a steering device for skid steer vehicles.

[Operation] In the steering device according to the present invention configured as described above, the direction of the wheels approaches or coincides with the actual traveling direction of the wheels during pivot turning, so that pivot turning can be performed smoothly.

[Embodiments] Hereinafter, preferred embodiments of the steering device for a skid steer vehicle according to the present invention will be described in detail with reference to the drawings.

Note that the same reference numerals are used for the same or equivalent parts as in the conventional configuration.

In FIGS. 1 and 2, the wheels 4 of the skid steer vehicle 1 are each attached to a machine frame 6 so as to be swingable left and right. To be more detailed,
As clearly shown in FIG. 3, an axle shaft 9 connected to a drive device (not shown) via a chain 7 and a sprocket 8 is rotatably supported by a bearing 10 protruding from the machine frame 6. A spline portion 12 extends from the tip of the axle shaft 9 via a constant velocity universal joint 11. This universal joint 11 must be capable of reliably transmitting torque regardless of the magnitude of the inclination angle of the spline portion 12, and the conventionally known Barfield type is suitable.

The wheel 4 is mainly composed of a wheel hub 13 made of a roller bearing, a rim 15 integrally connected to an outer race 14 of the wheel hub 13, and a tire 16 fitted into the rim 15. The spline portion 12 passes through the inner race 17 of the wheel hub 13 and is connected to the outer race 14. Further, the spindle yoke 18 integrated with the inner race 17 is connected to the tip support member 10 of the bearing 10.
' is attached by two pins 19 to the wheel 4.
can swing approximately horizontally about the common axis of these bins 19. A steering arm 20 is bolted to the upper part of the spindle yoke 18, and the steering arm 20 is connected to the machine frame 6.
A hydraulic cylinder 21 is interposed between the tip of the cylinder and the tip of the cylinder.

By hydraulically controlling the hydraulic cylinder 21, which is the driving means, the wheels 4 can be brought into the neutral state shown in FIG.
It is oscillated between the pivoting state shown in FIG. In addition, the bending angle α of the wheel in the pivot turning state is an angle at which the tank slip angle at the time of pivot turning becomes small, and the best angle is an angle that corresponds to the actual traveling direction of the wheel 4.

The drive device of the skid steer vehicle 1 of this embodiment is a hydrostatic type, and as shown in FIG. 4, it has two axial piston type hydraulic pumps 22a and 22b arranged coaxially with each other and integrated. ing. These hydraulic pumps 22
By changing the inclination angle of a swash plate (not shown), the output of the drive device can be changed by changing the discharge amount and flow direction of hydraulic oil.

The swash plates of the hydraulic pumps 22a, 22b are connected to trunnion levers 23a, 23b and connecting rods 24a, 24, respectively.
It is connected to steering levers 25a and Z5b arranged on the left and right sides of the driver's seat through Z5b, and a steering operation can be performed by tilting the steering levers 25a and 25b.

Each trunnion lever 23a, 23b extends downward, and a pair of limit switches 27af, 27ar and a pair of limit switches 27bf, 27br are arranged before and after the extension portions 26a, 26b, respectively, and the steering lever 25a , 25b is tilted forward beyond a predetermined angle, the front limit switches 27d, 27
When the bf button is pressed and the vehicle tilts backward, the rear limit switches 27ar and 27br buttons are pressed. The signal from the limit switch 27 is sent to a control box 28 which is a control means, and the control box 28 controls a control valve (not shown) in a hydraulic circuit 29 related to the hydraulic cylinder 21 according to the input signal. do.

In such a configuration, the operation of the steering device of the present invention will be explained.

When making a rightward pivot turn, tilt the left steering lever 25b forward, and tilt the right steering lever 25b forward.
A is tilted backward, but at this time, limit switch 27bf and limit switch 2far are connected to trunnion lever 23a.
, 23b is pushed by the extensions 26m and 26b and turned ON. Upon receiving this ON signal, the control box 28 controls the hydraulic circuit 2 to bring the wheels 4 into a pivot state.
A control signal is issued to switch the position of control valve 9. As a result, all hydraulic cylinders 21
The piston rod retracts, and the front, rear, left and right wheels 4 move to the second position.
As shown in the figure, the orientation of the wheels 4 matches the direction of travel, and pivoting is performed smoothly.

In addition, in the case of a leftward pivot turn, the limit switch 27af and the limit switch 27bf are turned on, but the control box 28 sends a control signal in the same way as in the rightward direction, and the wheels 4 are turned to the pivot position shown in FIG. It will be in a turning state.

In cases other than the above-mentioned pivot rotation, that is, forward movement, backward movement,
In the case of a slow turn, the control box 28 recognizes the current steering condition based on the signal from the limit switch 27, and maintains the wheels 4 in the neutral condition shown in FIG. Even in the case of a pivot turn, if the extension part 26 of the trunnion lever 23 does not touch the button on the limit switch 2, the wheels 4 will remain in a neutral state, but the wheels 4 will remain in a neutral state. There is no problem because the resistance between and.

In the above embodiment, the steering state is detected by the limit switch 27 which is turned on and off depending on the position of the extension part 26 of the trunnion lever 23. However, as such detection means, the inclination angle of the steering lever 25 or the trunnion lever 23 is used to detect the steering state. Detection means and connecting rod 24
Various methods can be considered, such as means for detecting the amount of movement. Also,
Although the drive device of the skid steer vehicle 1 in the above embodiment is a hydrostatic type, those skilled in the art will easily understand that the present invention is also applicable to skid steer vehicles equipped with a mechanical drive device.

[Effects of the Invention] As described above, according to the present invention, since the wheels can be oriented in the sliding direction, pivoting is smoothed. Therefore, the load on the engine is reduced, engine stalling is prevented, and vehicle instability such as picking can be avoided. The present invention is particularly effective in heavy skid steer vehicles and skid steer vehicles under load.

[Brief explanation of the drawing]

1 and 2 are schematic explanatory diagrams showing one embodiment of the steering device of the present invention, and FIG. 1 is a neutral state,
The figures show the pivot turning states, and Fig. 3 shows the 1st
4 is a schematic explanatory diagram showing the relationship between the detection means for detecting the steering state and the control means for controlling the hydraulic cylinder, and FIG. 5 is a cross-sectional view taken along the line A-A in the figure. A schematic explanatory diagram of a power transmission system in a vehicle,
FIG. 6 is a schematic explanatory diagram showing a skidding state when a conventional skid steer vehicle makes a pivot turn.・・・
・Axle shaft 11...Universal joint 16...Tire 20...
- Steering arm 21... Hydraulic cylinders 23a, 23b... Trunnion levers 25a, 25b
...Steering lever 27af, 27ar, 27
bf, 27br-Limit switch 28...Control box 29...Hydraulic circuit Patent applicant Toyota Industries Corporation Size 1
Sun 1 Sun 1 Procedure amendment writing method) April 1, 1986

Claims (1)

[Claims] Each wheel is attached to the machine frame so as to be able to swing from side to side, driving means for swinging each wheel is provided, and detection means for detecting a steering state is provided, and the detection means detects that the pivot is in a turning state. A steering device for a skid steer vehicle, comprising a control means for operating the drive means to change the direction of each of the wheels so that a sideslip angle is reduced when the skid steer vehicle is detected.