JPH11263235A - Steering device for traveling vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the straight stability while transmitting the straight restoring force applied to wheels to a steering wheel in an upper part turning type traveling vehicle. SOLUTION: An upper hydraulic motor 23 to be operated in response to the operation of a steering wheel 16 is arranged in an upper rotating body, and a steering unit 24 for changing the steering angle of wheels 18, 18 and a lower hydraulic motor 27 connected to the steering unit 24 are arranged in a lower traveling body, and both the hydraulic motors 23, 27 are connected by oil passages 28, 29 through a rotary joint 22 so as to form a closed circuit 30. With this structure, the straight restoring force applied to the wheels 18, 18 at the time of traveling is transmitted to the steering wheel 16 through the oil pressure of the closed circuit 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering system for a traveling vehicle in which an upper revolving unit is mounted on a lower traveling unit having wheels, such as a wheel crane or a wheel shovel, and the wheels are operated from a driver seat of the upper revolving unit. It concerns the device.

[0002]

2. Description of the Related Art A traveling vehicle provided with an upper revolving structure as described above (hereinafter referred to as an upper revolving type traveling vehicle) is equipped on a general traveling vehicle such as a truck due to the uniqueness that the upper revolving structure rotates. It is not possible to directly adopt a configuration in which an integral power steering unit connected to a steering wheel is connected to a front wheel via a mechanical link mechanism such as an arm or a drag link.

For this reason, in a conventional upper turning type traveling vehicle, as shown in FIG. 3, a steering unit (power booster) 1 is arranged on an upper revolving unit, and steering cylinders 2 and 3 are arranged on a lower traveling unit, respectively. The front wheel is steered by supplying high-pressure hydraulic oil according to the operation amount of the handle 4 from the steering unit 1 to the steering cylinders 2 and 3 through a rotary joint 5 arranged at the center of rotation of the upper swing body. (2-8)
940).

In FIG. 3, reference numeral 6 denotes a hydraulic pump as an oil supply source driven by an engine. Further, in FIG. 2, the internal mechanism of the steering unit 1 is schematically represented by hydraulic symbols of the servo valve 7 and the hydraulic motor 8.

[0005]

However, according to the above-mentioned prior art, since the rectilinear restoring force applied to the front wheel by the well-known wheel alignment mechanism is not transmitted to the steering wheel 4 during traveling, the neutral position (straight traveling position) ) Does not work automatically.

That is, the rectilinear restoring force received by the front wheel is applied to the steering cylinders 2 and 3, and the cylinders 2 and 3 try to discharge hydraulic oil toward the steering unit 1. The steering wheel automatically returns to the neutral position after the operation of the steering wheel. In this neutral position, the discharged hydraulic oil is blocked, so that the straight forward restoring force received by the front wheel is not transmitted to the steering wheel 4.

For this reason, the driver has to return the steering wheel 4 to the neutral position by measuring each time after turning the steering wheel 4 and turning the curve.

[0008] Therefore, the vehicle may fluctuate especially when changing lanes that require quick steering operation, which not only reduces the driving safety of the vehicle but also increases the size of the large turning vehicle. In addition to this, the driver of the surrounding vehicle sometimes gives fear.

[0009] Under the circumstances described above, the conventional upper turning type traveling vehicle requires a long time to learn driving skills because the steering wheel operation is not easy, and requires special driving skills considerably different from those of ordinary traveling vehicles. I was

Accordingly, the present invention provides an upper turning type traveling vehicle in which the rectilinear restoring force received by the wheel can be transmitted to the steering wheel to ensure the rectilinearity, and the transmission loss of the rectilinear restoring force is small so that the steering wheel can be reliably returned. It is an object of the present invention to provide a steering device for a traveling vehicle that requires a compact device.

[0011]

According to a first aspect of the present invention, there is provided a traveling vehicle in which an upper revolving body having a driver's seat having a steering wheel is rotatably mounted on a lower traveling body having wheels. An upper hydraulic motor that operates in response to the operation of the steering wheel is arranged on the upper revolving superstructure, while a lower traveling body is provided with a steering unit that changes a steering angle of a wheel and a lower hydraulic motor connected to the steering unit. The upper and lower hydraulic motors are connected to each other by an oil path via a rotary joint disposed at the center of rotation of the upper revolving unit to form a closed circuit, and the rectilinear restoring force received by the wheel during traveling is closed. It is configured to be able to transmit to the handle via the hydraulic pressure of the circuit.

According to the above configuration, when the handle is operated, the upper hydraulic motor rotates in a closed circuit to exert a pump action, and discharges an amount of oil corresponding to the handle operation amount. The oil discharged from the upper hydraulic motor is sent to the lower hydraulic motor, which rotates and drives the steering unit to steer the wheels.

On the other hand, the rectilinear restoring force received by the wheel during traveling is transmitted to the lower hydraulic motor via the steering unit, and the motor performs a pumping operation to rotate the upper hydraulic motor. Conveyed to.

By the transmission function of the rectilinear restoring force, the steering wheel after the steering is automatically returned to the neutral position in the same manner as a general traveling vehicle.

That is, although the wheel of the lower traveling structure is operated from the driver's seat of the upper revolving structure, it has rectilinear recov- ery and the steering wheel operation becomes easy.

Here, as another means for securing the rectilinear restoring force in the upper turning type traveling vehicle, hydraulic cylinders (steering cylinders) are arranged on the upper turning body and the lower traveling body, respectively, and these are connected by a closed circuit. It is conceivable to adopt a configuration in which the upper steering cylinder is operated by the output of the steering unit operated by the steering wheel, and the lower steering cylinder is interlocked with this.

However, according to this configuration, both the upper and lower steering cylinders need to have large capacities in accordance with the steering unit having a large output, so that the entire device becomes large.

In addition, the sliding resistance of the cylinder also increases, making it difficult for the straight-line restoring force to be transmitted to the handle, and the return of the handle becomes poor.

On the other hand, according to the configuration of the present invention, since the upper and lower hydraulic motors are used on the input side of the steering unit whose torque is much smaller than the output side, the motor capacity can be reduced. For this reason, the device can be downsized, and the transmission resistance of the straight-line restoring force is small, so that the return of the steering wheel is ensured.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows an overall schematic configuration of a wheel crane which is an example of an upper turning traveling vehicle to which the present invention is applied.

In FIG. 1, reference numeral 11 denotes a lower traveling body, on which an upper revolving body 12 is mounted via a revolving bearing 13 so as to be rotatable about a vertical axis X.

The upper revolving unit 12 has a telescopic boom 1
4 is provided so that it can be raised and lowered, and the cabin (operator's cab)
A steering wheel 16 is provided in the cabin 15.

On the other hand, the lower traveling body 11 is provided with a front wheel 18 which is a steered wheel in this embodiment at a front portion of a traveling frame 17 and a rear wheel 19 at a rear portion on both right and left sides.

The traveling body frame 17 is provided at its rear end with an engine box 20 in which an engine (not shown) for driving and operating the crane is accommodated. Outriggers are provided on both left and right sides of the front and rear parts. 21
... are provided.

Further, a rotary joint 22 (shown in FIG. 2) is provided around a vertical axis X, which is the center of rotation of the upper revolving unit 12, and the hydraulic pipes on the lower traveling unit 11 side and the upper revolving unit 12 side are connected to each other. The connection is made via the joint 22.

Next, the hydraulic circuit configuration of the steering device will be described with reference to FIG.

An upper hydraulic motor 23 is connected to a handle shaft 16a that is rotated by operating the handle 16 on the upper revolving structure side that is above the rotary joint 22.

On the other hand, an integral type (other type such as a booster type) steering unit 24 is arranged on the lower traveling body side below the rotary joint 22, and the output side of the unit 24 is provided. Link 2 provided in
5 are front left and right wheels 1 via tie rods 26.
8, 18 are connected to knuckle arms 18a, 18a.

A lower hydraulic motor 27 is provided on the input side of the steering unit 24, and the lower hydraulic motor 27 and the upper hydraulic motor 23 are connected by oil passages 28 and 29.

Thus, both motors 23 and 27 and oil passage 2
8, 29 form a closed circuit 30, and this closed circuit 3
The steering wheel operating force is transmitted to the steering unit 24 by the hydraulic pressure of 0, and the wheels 18 are steered.

That is, when the handle 16 is operated,
The upper hydraulic motor 23 is driven by the rotational force of the handle shaft 16a.
Rotates in the handle rotation direction by an amount corresponding to the amount of rotation, and exerts a pump action to discharge oil.

Then, the lower hydraulic motor 27 rotates by the amount of the discharged oil to drive the steering unit 24, and the unit 24 performs a known boosting action, and the output corresponding to the input is output to the link 25, the tie rod. 26, is applied to the front wheels 18, 18 via a knuckle arm 18a, and the wheels 18, 18 are steered.

After the steering, the straight-line restoring force applied to the wheels 18, 18 is transmitted to the lower hydraulic motor 27 via the steering unit 24 via a path reverse to the above, and the motor 27 exerts a pumping action. To rotate the upper hydraulic motor 23.

As a result, the wheels 18, 18 return to the rectilinear position and the rectilinear restoring force is
At the same time, the handle 16 automatically returns to the neutral position (straight forward position) at the same time.

Here, the upper and lower hydraulic motors 2
Since the motors 3 and 27 are provided on the input side of the steering unit 24, the torque acting on the motors 23 and 27 is extremely small, about 1/100 of the output side.

Accordingly, the motors 23 and 27 and the oil passages 28 and 29 connecting them may have a small capacity, and the rotational resistance and the pipe resistance of the motor can be reduced.
The transmission loss of the rectilinear restoring force transmitted from the steering wheels 8 and 18 to the handle 16 is extremely small.

That is, the rectilinear restoring force is transmitted to the handle 16 without waste, and the handle 16 is reliably returned to the neutral position.

The upper and lower hydraulic motors 23,
In the present invention, the name “motor” is used for the device 27, but this is different from a motor in a narrow sense only driven by a pump, and a rotary actuator having both a pump function and a motor function as described above is used. It points.

The upper and lower hydraulic motors 2
Motor drain lines 31 and 32 are connected to 3 and 27, respectively, and the oil in the closed circuit 30 is discharged out of the system through the motor drain lines 31 and 32, so that the oil amount in the closed circuit 30 gradually increases. To decrease.

Further, the oil decreases due to the contraction of the oil caused by the decrease in the oil temperature. If the oil is left as it is, there is a possibility that the above-described steering action and straight-running restoring action may be reduced.

Therefore, the two-side oil passage 2 constituting the closed circuit 30
The oil supply circuit 33 is connected to 8, 29.

The oil supply circuit 33 includes two oil passages 28, 2
Check valve 3 that allows oil to flow in and prevents outflow
4 and 35, and an oil supply pump 36 driven by an engine (not shown). When the closed circuit 30 is pressurized by the oil supply circuit 33 during operation of the engine and the amount of oil is reduced, Oil is supplied to ensure the desired steering action and straight-line restoring action.

In FIG. 2, reference numeral 37 denotes an oil supply circuit relief valve for setting the circuit pressure of the oil supply circuit 33.

Reference numeral 38 denotes a hydraulic pump for the steering unit as a hydraulic source of the steering unit 24, 3
Reference numeral 9 denotes a flow divider provided in an oil path connecting both the pump and tank ports of the steering unit 24 to the pump 38 and the tank T, and reference numeral 40 denotes a relief valve for setting the discharge pressure of the pump 38.

[0046]

As described above, according to the present invention, in an upper turning type traveling vehicle, an upper hydraulic motor that operates in accordance with operation of a steering wheel is arranged on the upper revolving body side, while a wheel is mounted on the lower traveling body side. A steering unit that changes the steering angle of the steering unit and a lower hydraulic motor connected to the steering unit are arranged, and the two hydraulic motors are connected to each other by an oil path via a rotary joint to form a closed circuit.
Since the straight running restoring force received by the wheels during traveling is transmitted to the handle via the hydraulic pressure of this closed circuit, the wheels of the lower running structure are operated from the driver seat of the upper revolving structure, but the straight running restoring performance is improved. Excellent, handle operation becomes easy.

That is, even a traveling vehicle having an upper turning type can operate with the same feeling as a general traveling vehicle such as a truck without wobbling when changing lanes.

In addition, since the upper and lower hydraulic motors are used on the input side of the steering unit whose torque is much smaller than the output side, the motor capacity can be small. For this reason, the device can be downsized, and the transmission resistance of the straight-line restoring force is small, so that the return of the steering wheel is ensured.

[Brief description of the drawings]

FIG. 1 is a side view showing an overall schematic configuration of a wheel crane to which the present invention is applied.

FIG. 2 is a hydraulic circuit configuration diagram of the steering device according to the embodiment of the present invention.

FIG. 3 is a hydraulic circuit configuration diagram of a conventional steering device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 16 Handle 18, 18 wheel 23 Upper hydraulic motor 27 Lower hydraulic motor 28, 29 Hydraulic path which connects both hydraulic motors 30 Closed circuit 24 Steering unit 25 Link which connects steering and wheel 26 Same tie rod 18a, 18a Same knuckle arm

Claims (1)

[Claims] 1. An upper part of a lower traveling body having wheels,
In a traveling vehicle in which an upper revolving body having a driver's seat having a steering wheel is rotatably mounted, an upper hydraulic motor that operates in response to operation of the steering wheel is disposed on the upper revolving body, while a lower traveling body is provided. A steering unit for changing the steering angle of the wheel and a lower hydraulic motor connected to the steering unit, and the upper and lower hydraulic motors are connected to each other via a rotary joint disposed at the center of rotation of the upper rotating body. A steering device for a traveling vehicle, wherein the steering device is configured to be connected by an oil path to form a closed circuit, and to transmit a rectilinear restoring force received by the wheel during traveling to the steering wheel via hydraulic pressure of the closed circuit.