JP2001001918A - Hydraulic power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic power steering device having good responsive ness with low power consumption without requiring a flow control valve. SOLUTION: This device controls a steered wheel 10 by the operation of a steering wheel 12. In this case, the device is equipped with a double acting steering hydraulic cylinder 26, a two-way flow type hydraulic pump 46 whose ports 48a, 48b are communicated with the volumetric chambers 30a, 30b of the hydraulic cylinder 26, a reversible electric motor 22 for operating the hydraulic pump 46, a means 18 for detecting handle operating condition, and a control means 20 for controlling the electric motor 22 based on the handle operating condition detected by the detecting means 18. Therefore, only changing the rotating direction and speed of the hydraulic pump 46, direction and amount of hydraulic fluid flow to the hydraulic cylinder 26 can be directly controlled. Therefore, a flow control valve is no more required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering device used for a vehicle, particularly an industrial vehicle such as a forklift.

[0002]

2. Description of the Related Art In an industrial vehicle such as a forklift, a hydraulic power steering device that steers a steered wheel by using a hydraulic cylinder (hereinafter referred to as a "steering cylinder") is widely used because of a feature that a large steering force can be obtained. ing. Conventional general hydraulic power steering devices switch a flow control valve such as a rotary valve based on operation of a steering wheel and adjust the supply amount and flow direction of hydraulic oil to a steering cylinder to perform steering control of a steered wheel. It is configured.

[0003]

In such a conventional hydraulic power steering apparatus, the hydraulic oil is delayed in order to enhance the responsiveness of the operation of the steering wheel, that is, when the valve is switched by operating the steering wheel. The hydraulic pump is constantly operated so that the hydraulic oil is constantly circulated so that the hydraulic oil is supplied to the steering cylinder without any problem. For this reason, even when steering is not being performed, power is continuously supplied to the electric motor that drives the hydraulic pump, and there is a problem that useless power is consumed.

[0004] In addition, a flow control valve, particularly a rotary valve, is required to have high precision and high durability, and thus has a problem that it is expensive.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic power steering apparatus which does not require flow control of hydraulic oil by a valve, consumes less power, and has good responsiveness. It is in.

[0006]

In order to achieve the above object, the present invention relates to a double-acting hydraulic power steering apparatus for steering a steered wheel by operating a steering wheel. The two cylinders are configured such that the discharge side of two ports can be switched according to the rotation direction of the rotating shaft, and each port is connected to each volume chamber of the steering cylinder. First hydraulic pump, a reversible electric motor for operating the first hydraulic pump, handle operation state detection means for detecting the operation state of the handle, and operation of the handle detected by the handle operation state detection means Based on the state, the rotation axis of the first hydraulic pump is rotated in a predetermined direction, and the corresponding port of the steering cylinder is rotated from one port. To supply hydraulic oil to the product chamber,
Control means for controlling the electric motor.

In this configuration, since the hydraulic pump serving as the hydraulic pressure source of the steering cylinder is of a two-way flow type, only by changing the rotating direction and the rotating speed of the rotating shaft,
The direction and amount of hydraulic oil flow to the steering cylinder can be directly controlled. Therefore, no flow control valve is required. Also, since the flow of hydraulic oil from the hydraulic pump is already a control flow, there is little delay,
Therefore, it is sufficient to operate the hydraulic pump only at the time of steering, that is, to supply power to the electric motor.

[0008] The hydraulic power steering apparatus according to the present invention further comprises steering state detecting means for detecting the steering state of the steered wheels, and the control means detects the steering state of the steered wheels based on the steering state detected by the steering state detecting means. It is preferable that the dynamic motor be controlled in such a manner.

In addition, a bypass means is provided between hydraulic lines extending from each port of the first hydraulic pump for releasing hydraulic oil to the other hydraulic line when the pressure of one hydraulic line exceeds a predetermined value. Is valid. This allows
For example, even if the hydraulic pump is operated when the tires are locked, the hydraulic oil does not flow to the steering cylinder, and it is possible to prevent the hydraulic line from being overloaded.

Further, in addition to the above components, the hydraulic power steering apparatus according to the present invention further comprises a two-way flow type second hydraulic pump directly operated by a handle, and the second hydraulic pump. A bypass line provided between hydraulic lines extending from each port of the pump and having a normally-closed on-off valve, wherein the control means controls to open the on-off valve when an ignition switch of the vehicle is turned on. Features.

When the key is turned off, the electric motor does not operate.
Cannot be used as the hydraulic pressure source, but the normally closed on-off valve is closed, and the second hydraulic pump serves as the hydraulic pressure source for the steering cylinder. Therefore, even at the time of key-off, hydraulic oil is supplied to the steering cylinder, and steering can be performed. Further, when the key is turned on, the on-off valve is opened, and the ports of the hydraulic pumps communicate with each other through the bypass line. Therefore, the second hydraulic pump does not become a hydraulic source, and the steering cylinder is driven by the first hydraulic pump.

When the ignition switch of the vehicle is turned on and the tire is locked, the on-off valve may be controlled to be closed. In such a case, the hydraulic oil tends to flow from the second hydraulic pump to the steering cylinder. However, since the piston in the steering cylinder is restrained by the tire lock, the flow of the hydraulic oil from the second hydraulic pump is large. The added resistance makes it difficult to move the steering wheel.

Further, in the hydraulic power steering apparatus according to the present invention, the rotating shaft of the first hydraulic pump and the handle are mechanically connected to each other so that the first hydraulic pump can be moved from the handle to the first hydraulic pump. The control means controls the electric motor so that the electric motor assists the torque applied to the rotating shaft. In this case, even when the electric motor cannot be driven due to, for example, a key-off state, the steering can be performed by directly operating the first hydraulic pump with the handle.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In addition, through all the figures,
The same or corresponding parts are denoted by the same reference characters, and repeated description will be omitted.

FIG. 1 is an explanatory diagram showing the overall configuration of a hydraulic power steering apparatus according to a first embodiment of the present invention. In this power steering device, the rear wheels are
The steering wheel (steering wheel) 12 for steering is applied to a forklift that becomes zero.
And a steering mechanism 14 for steering the steered wheels 10 are of a so-called separated type in which the steering mechanism 14 is mechanically separated. This separation type power steering device includes a steering wheel 12 and a steering mechanism 14.
Since there is no mechanical transmission mechanism between them, the space in the machine base (not shown) can be effectively used. In particular, in the case of forklifts, the hydraulic piping is placed inside the machine,
There is an advantage that the degree of freedom of layout such as piping is increased.

A steering shaft 16 extends downward from the handle 12 and is rotatably supported. A rotary encoder 18 is attached to an intermediate portion of the steering shaft 16 as detection means for detecting an operation state of the steering wheel 12. As the rotary encoder 18, an absolute value type that can detect a rotation angle, a rotation speed, and a rotation direction from a reference position is preferable.
The output unit of the rotary encoder 18 is connected to a control device 20 including a microcomputer or the like that comprehensively controls the steering of the steered wheels 10. As will be described later, the control device 2
0 detects a rotation angle, a rotation speed, and a rotation direction of the steering shaft 16, that is, an operation state of the steering wheel 12, based on an output signal from the rotary encoder 18,
Based on the result, the electric motor 22 in the steering mechanism 14 is controlled.

A load device 24 for applying a load to the steering shaft 16 and the steering wheel 12 is connected to the lower end of the steering shaft 16. The load device 24 compensates for a decrease in operability due to the mechanical separation of the steering shaft 16 from the steering mechanism 14, and generates a load corresponding to the state of the steered wheels 10 to provide the driver with a normal load. It is intended to provide a steering feeling equivalent to that of the non-separable type steering device. The load device 24 according to the present embodiment regulates the further turning operation of the steering wheel 12 when the steered wheels 10 reach the steering end (steering limit) or when the tires are locked. A follow-up limit is given to the rotation operation of the steering wheel 12 so that the rotation speed of the steering wheel 12 does not greatly deviate from the rotation speed (steering speed) of the steered wheels 10. As such a load device 24, a load device using an electric motor or the like has been conventionally proposed, but the load device of the present embodiment is configured by a hydraulic circuit. The configuration of the load device 24 will be described later.

The steering mechanism 14 has a steering cylinder 26 as a drive source for steering the steered wheels 10.
The steering cylinder 26 is a double-acting double-rod type hydraulic cylinder, and includes a cylinder tube 28, a piston 32 that divides the inside thereof into two volume chambers 30 a and 30 b, and is arranged so as to be able to reciprocate. And a pair of steering rods 34 attached to the surface and extending from each end face of the cylinder tube 28. The cylinder tube 28 is fixed to a machine base, for example, a rear axle beam (not shown), and an end of each steering rod 34 is connected to a knuckle arm 38 that rotatably supports the steering wheel 10 via a lever 36. Mechanically connected. The knuckle arm 38 is attached to the rear axle beam so as to be rotatable in the horizontal direction by a king pin 40 extending in the vertical direction. Therefore, by controlling the supply of hydraulic oil to the steering cylinder 26 and operating the steering rod 34, the knuckle arm 38
Is rotated, whereby the steered wheels 10 are steered.

In order to set the steering end, a stopper (not shown) that comes into contact with the knuckle arm 38 and regulates its movement is provided integrally with the rear axle beam.

Further, as means for detecting the steering state of the steered wheels 10, a steering angle sensor 42 for detecting a steering angle is provided. Although there are various types of the steering angle sensor 42, a potentiometer that detects the amount of rotation of the king pin 40 is preferable because of its simple structure and excellent durability. The steering angle detection signal of the steering angle sensor 42 is input to the control device 20 and is used for steering control.

Each volume chamber 30 of the steering cylinder 26
a, 30b, hydraulic lines 44, 45 extend, and each port 48 of a hydraulic pump (first hydraulic pump) 46, respectively.
a, 48b. This hydraulic pump 46
It is a two-way flow type represented by an external gear pump, etc.
By changing the rotation direction of the rotation shaft 50, the discharge function and the suction function of the ports 48a and 48b are exchanged.
The hydraulic pump 46 is of a fixed displacement type,
The discharge amount also increases and decreases in proportion to the increase and decrease of the rotation speed of zero.

The rotary shaft 50 of the hydraulic pump 46 is connected to the rotary shaft 52 of the electric motor 22. This electric motor 2
2 is a reversible / variable speed type. That is, the rotating shaft 52 is rotatable in both forward and reverse directions, and its rotation speed is also variable. The electric motor 22 is connected to the control device 20, and the rotation speed and the rotation direction of the rotating shaft 52 are controlled by the control device 20. Therefore, the electric motor 22
, The discharge port of the hydraulic pump 46 can be switched and the discharge amount can be adjusted.

Between the hydraulic line 44a and the hydraulic line 44b, there is provided a bypass circuit (bypass means) 58 in which two relief valves 54a and 54b and two check valves 56a and 56b are incorporated. This bypass circuit 5
8, the hydraulic oil is supplied to the steering cylinder 2 when the pressure in one of the hydraulic lines 44a, 44b becomes a predetermined value or more.
6 is bypassed to the other hydraulic lines 44b and 44a to prevent the hydraulic circuit from being overloaded.

Reference numeral 60 denotes an oil tank. This is because the circuit composed of the steering cylinder 26 and the hydraulic pump 46 is a closed circuit and therefore compensates for a change in the volume of hydraulic oil due to a change in temperature. For the same purpose, an accumulator can be used instead of the oil tank 60.

In such a configuration, various steering control methods can be adopted. Here, one example is described.

First, when the driver rotates the steering wheel 12 in either the left or right direction from a state where the steering angle of the steered wheels 10 is zero, that is, a neutral straight traveling state, the steering shaft 16 is also rotated integrally with the steering wheel 12. , A signal is sent from the rotary encoder 18 to the control device 20. The control device 20 detects a handle operation state such as a rotation angle, a rotation speed, and a rotation direction of the handle 12 from a reference position based on an output signal from the rotary encoder 18, and controls the electric motor 22 according to the detection result. At a predetermined rotational speed.

When the electric motor 22 is driven, the rotating shaft 5
Hydraulic oil is supplied from one port, for example, port 48a of the hydraulic pump 46 determined by the rotation direction
The fluid is discharged at a flow rate corresponding to the rotation speeds of 0 and 52, and flows into one volume chamber 30a of the steering cylinder 26 through the hydraulic line 44a. As a result, the piston 32 starts moving toward the other volume chamber 30b. Hydraulic oil is pushed out from the other volume chamber 30b of the steering cylinder 26 with the movement of the piston 32, and the port 48b side of the hydraulic pump 46 has a negative pressure. Returned to 46.

When the piston 32 moves, its operation is controlled by a knuckle arm 3 via a steering rod 34 and a lever 36.
8, the steered wheels 10 are changed to a predetermined steering angle at a predetermined steering speed. In addition, the rotation angle (position of the handle 12) of the handle 12 from the reference position is previously stored in the control device 20.
It is preferable that the steering angle of the steered wheels 10 is stored in advance, and the steering angle of the steered wheels 10 is constantly detected based on an output signal from the steering angle sensor 42 to feedback-control the electric motor 22.

At the time of this steering, the control device 20 electrically recognizes the operation of the steering wheel and drives the electric motor 22, and almost simultaneously with the start of driving of the electric motor 22, the hydraulic oil is supplied from the hydraulic pump 46 at a predetermined flow rate. Since the vehicle is discharged and supplied to the steering cylinder 26, the response of the operation of the steered wheels 10 to the operation of the steering wheel becomes extremely good. This eliminates the necessity of constantly energizing the electric motor 22 as in the related art, and enables power saving.

When the steering wheel 12 is further rotated in the same direction, the steering wheel 12 reaches the vicinity of the steering end. When the control device 20 detects that the steered wheel 10 has reached a predetermined position before the steering end based on a signal from the steering angle sensor 42, the control device 20 stops energizing the electric motor 22. When the power supply to the electric motor 22 is stopped, the supply of the hydraulic oil to the steering cylinder 26 is stopped, and the rotation of the steered wheels 10 is stopped. However, since the inertial force of the rotor or the like acts in practice, the hydraulic pump 46 continues to rotate for a very short time. For this reason, the steered wheels 10 stop immediately before the steering end or stop at the steering end.
At the steering end, an impact force is generated because the knuckle arm 38 comes into contact with the stopper. However, since the power steering device of the present embodiment is a separate type, the impact force is not transmitted to the steering wheel 12 and the driver feels discomfort. I will not give.

When the hydraulic pump 26 is still driven by inertia or the like when the steered wheels 10 reach the steering end, further movement of the piston 32 of the steering cylinder 26 is restricted. The pressure in the side hydraulic line 44a increases. When this pressure becomes equal to or higher than a predetermined value, the relief valve 54a is opened, and the hydraulic oil passes through the relief valve 54a and the check valve 56b, bypasses the steering cylinder 26, and is connected to the port 4 of the hydraulic pump 46.
8b directly. As a result, the pressure in the hydraulic line 44a does not increase to a predetermined value or more, and it is possible to prevent an excessive load from being applied to each element of the hydraulic circuit. Also, when the tire is locked before reaching the steering end, for example, when the steered wheel 10 gets into the side groove, the stoppage of the power supply to the electric motor 22 is delayed, so that the pressure in the hydraulic line 44a increases. In such a case, too, the hydraulic oil flows through the bypass circuit 58, so that an excessive increase in pressure is prevented.

When the handle 12 is turned in the opposite direction, the discharge port 48a is switched to the other port 48b, and the flow of hydraulic oil is only reversed, and the power steering apparatus operates in the same manner as described above. That will be easy to understand.

Incidentally, since the power steering apparatus in the above embodiment is of a separate type, the steering wheel 12 can be freely rotated regardless of the state of the steered wheels 10. This has the effect that the lock-to-lock rotation of the handle 12 can be set freely according to the situation or the like. On the other hand, the steering wheel 12 can be freely rotated even when the tire is locked at the steering end or the like, or when the steering wheel 12 is rotated at a high speed, the rotation speed of the steering wheel 12 and the steering There is a possibility that the steering speed of the wheel 10 is greatly deviated. For this reason, a steering feeling different from a normal non-separable type steering device is given to the driver.

Therefore, as described above, in this embodiment, the load device 24 is attached to the lower end of the steering shaft 16 so as to obtain a normal steering feeling as much as possible.

The load device 24 is, as clearly shown in FIG.
The rotary shaft 62 includes a hydraulic pump 64 connected to the other end of the steering shaft 16. This hydraulic pump 64
Is a constant displacement two-way flow type similar to the hydraulic pump 46 described above.

Port 66a and port 6 of the hydraulic pump 64
6b from the hydraulic line 68a and the hydraulic line 6 respectively.
8b, these hydraulic lines 68a, 68b are connected at point P1 to form one loop line. Each hydraulic line 68a, 68b has a hydraulic pump 6
4, the flow control valves 70a and 70b and the solenoid valves 72a and 72b are arranged in series.
In addition, the point P in each hydraulic line 68a, 68b
2 and the point P3, the flow control valves 70a, 70
b and bypass lines 74a, 74b bypassing the on-off valves 72a, 72b are connected.
Check valves 76a and 76b that allow only the flow from point P3 to point P2 are attached to 4a and 74b. The flow control valves 70a and 70b and the on-off valves 72a and 72b are substantially the same, so that the hydraulic circuit of the load device 24 has a symmetrical structure with the hydraulic pump 64 as the center.

The flow control valves 70a and 70b adjust the flow rate by using the flow rate on the inlet side (the flow rate on the ports 66a and 66b side of the hydraulic pump 64) as a switch. In the illustrated embodiment, a two-port two-position spool is used. It takes the form of a valve. That is, the illustrated flow control valves 70a, 70b are connected from one port 66a, 66b to the other port 66b,
It is of a type that allows only the flow to the port 66a. In the first position, which is the spring offset position, there is no load between the ports in an open state, and in the second position, the flow path area between the ports is reduced. I have. The flow control valves 70a and 70b have an orifice 78 on the inlet side and a pilot line 80 at a point P4 on the upstream side.
Is connected, and when the flow rate at the point P4 reaches a predetermined value, the first position is switched to the second position.

The on-off valves 72a and 72b are driven by a solenoid 82, and the energization of the solenoid 82 is controlled by the controller 20. The on-off valves 72a and 72b are of a normally open type, and the flow path is shut off by energizing the solenoid 82.

Further, in order to compensate for a change in the volume of hydraulic oil due to a change in temperature, the oil tank 60 is placed at a point P1.
Is connected.

In the load device 24 having such a configuration, when the rotation speed of the handle 12 is lower than a predetermined value (for example, about 2.6 rps) at the time of operating the handle, the flow control valves 70a and 70b are turned off. In the first position, the on-off valves 72a and 72b are open. Then, as the steering wheel 12 rotates, hydraulic oil is sent out from one of the ports of the hydraulic pump 64 to which the steering shaft 16 is connected, for example, the port 66a. Since the check valve 76a for preventing the flow from the point P2 to the point P3 is provided in the bypass line 74a on the port 66a side, the hydraulic oil is supplied to the flow control valve 70a in the hydraulic line 68a.
And flows to the point P1 through the on-off valve 72a.
Since the flow control valve 70b in the hydraulic line 68b allows only the flow from the point P2 to the point P3, the hydraulic oil is returned to the port 66b of the hydraulic pump 64 via the bypass line 74b (see FIG. 2). See the flow indicated by the solid arrow).

During such a flow, a pressure corresponding to the discharge flow rate of the hydraulic pump 64 is generated on the port 66a side of the hydraulic pump 64. Since the discharge flow rate of the hydraulic pump 64 corresponds to the rotation speed of the handle 12, the relationship between the oil pressure at the point P4 and the rotation speed of the handle 12 is as shown in the area A in FIG. The pressure in the hydraulic circuit is a load that the hydraulic oil applies to the hydraulic pump 64. Accordingly, a load corresponding to the hydraulic pressure acts on the handle 12, and this acts to give a certain weight to the rotation operation of the handle 12. In addition, as shown in the area A of FIG. 3, the hydraulic pressure increases as the rotation speed of the handle 12 increases, so that the load on the handle 12 gradually increases. Such a state gives a steering feeling similar to that of a conventional general non-separable type steering device.

On the other hand, when the rotation speed of the handle 12 exceeds the rotation speed (2.6 rps) of the following limit, the flow rate at the point P4 of the hydraulic circuit exceeds a predetermined value, and the flow control valve 70a
Switches from the first position to the second position. As a result, the flow passage area of the hydraulic line 68a is reduced, and the internal pressure of the hydraulic circuit is rapidly increased (see the region B in FIG. 3). Therefore,
The load acting on the handle 12 increases, making it difficult to continue the rotation operation in the same direction. In a conventional general non-separable type steering device, the handle 12 is approximately 2.6.
When the rotation operation is performed at rps, the handle 12 is set to be suddenly heavier, and the same operation feeling as this can be obtained in the present embodiment.

When the steering wheel 12 is further turned in the same direction at the time of tire lock such as when the steered wheel 10 reaches the steering end or gets into the side groove, the control device 20 transmits the signal from the rotary encoder 18 and the steering angle sensor 42. It is determined that the tire is locked because the steering angle does not change in spite of the turning operation of the steering wheel 12 based on the output signal of the steering wheel 12. And, the solenoid 8 of the on-off valve 72a
2, and the on-off valve 72a is closed. As a result, the flow of the hydraulic oil from the port 66a to the port 66b of the hydraulic pump 64 is blocked, and the steering wheel 12 cannot be turned. At the same time, the driver knows that the tire lock has occurred.

In the tire locked state, the hydraulic line 6
8b is in the first position and the on-off valve 72b
b is in the open state. Therefore, if the driver tries to turn the handle 12 in the opposite direction, the port 66 of the hydraulic pump 64
b becomes the discharge port, and the hydraulic oil returns to the port 66a of the hydraulic pump 64 through the hydraulic line 68b and the bypass line 74a (see the flow indicated by the dotted arrow in FIG. 2). That is, the load device 24 does not restrict the reverse operation of the steering wheel 12, and can rotate the steered wheels 10 in the reverse direction.

Load device 2 utilizing such a hydraulic circuit
No. 4 is particularly effective in a battery car because the power consumption is extremely small. Further, as other modes of the load device using the hydraulic circuit, those shown in FIGS. 4A to 4C can be considered. These are the ones in which the positions and numbers of the flow control valves, the on-off valves, and the check valves are changed, but those skilled in the art will understand from the drawings that they can perform the same functions as the load device 24 in FIG. .

Next, a hydraulic power steering apparatus according to a second embodiment of the present invention will be described with reference to FIG. The power steering device according to the second embodiment is different from the power steering device according to the first embodiment in that a load device is not connected to the steering wheel 12, but the relationship between the steering mechanism 14 and the steering wheel 12 is the first. This is the same as the embodiment. Therefore, in FIG. 5, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Also in the second embodiment, a constant displacement / two-way flow type hydraulic pump (second hydraulic pump) similar to the hydraulic pump 64 of the load device 24 in the first embodiment is provided at the lower end of the steering shaft 16. 90 rotation shafts 92 are connected. The ports 94a and 94b of the hydraulic pump 90 are connected to the volume chambers 30a and 30b of the steering cylinder 26 by hydraulic lines 96a and 96b, respectively. Each of the hydraulic lines 96a and 96b is provided with check valves 98a and 98b that allow only the flow of hydraulic oil from the hydraulic pump 90 to the steering cylinder 26. The check valves 98a and 98b are of a pilot operated type, and the check function can be released by the pilot pressure. The pilot lines 99a and 99b are connected to the other hydraulic line (for the check valve 98a, the hydraulic line 96).
b, the check valve 98b is connected to the hydraulic line 96a), and the internal pressure of the other hydraulic line is used as the pilot pressure.

Further, between the hydraulic lines 98a and 98b,
A bypass line 102 having a normally closed solenoid on-off valve 100 is connected. The energization of the solenoid 104 of the on-off valve 100 is controlled by the control device 20.

Further, between the hydraulic lines 96a and 96b,
A bypass line 108 having two check valves 106a and 106b is connected. Check valves 106a, 106b
Between them, an oil tank 60 of a hydraulic circuit in the steering mechanism 14 is connected. Each hydraulic line 96a, 96b
The check valves 106a and 106b adjacent to the valve allow only the flow of hydraulic oil from the oil tank 60 to the hydraulic lines 96a and 96b.

In this configuration, when the ignition switch of the forklift is turned on, the control device 20 energizes the solenoid 104 of the on-off valve 100,
The on-off valve 100 is opened. As a result, even if the rotating shaft 92 of the hydraulic pump 90 is rotated by the rotation operation of the handle 12, the hydraulic oil pumped from the hydraulic pump 90 flows through the bypass line 102 and is not supplied to the steering cylinder 26. On the other hand, the electric motor 22 connected to the hydraulic pump 46 in the steering mechanism 14 is controlled by rotating the handle 12 as in the first embodiment. At this time, the hydraulic oil supplied from the hydraulic pump 46 to the steering cylinder 26 does not flow out to the hydraulic lines 96a, 96b by the check valves 98a, 98b.
Therefore, the manner of steering is substantially the same as in the first embodiment.

On the other hand, in the key-off state, power is not supplied to the control device 20 and the electric motor 22, so that steering using the hydraulic pump 46 is not performed, but the hydraulic pump directly connected to the steering shaft 16 is not operated. 90 serves as a hydraulic pressure source for the steering cylinder 26, and the steering becomes possible. More specifically, when the key is turned off, the on-off valve 100 is closed, and the handle 12 is closed.
Is operated to rotate the rotary shaft 92 of the hydraulic pump 90, hydraulic oil is discharged from one of the ports, for example, the port 94a, and this hydraulic oil is supplied to the volume chamber 30a of the steering cylinder 26 through the hydraulic line 96a. Is done. At this time, the internal pressure of the hydraulic line 96a exceeds a predetermined value, and the check function of the check valve 98b in the other hydraulic line 96b is released. Therefore, when hydraulic oil is supplied to one of the volume chambers 30a, the piston 32 moves, and the other volume chamber 3a moves.
The hydraulic oil in Ob returns to the port 94b of the hydraulic pump 90 through the hydraulic line 96b. As described above, the steered wheel 10 is steered by the movement of the piston 32.

When the steering wheel 10 is locked such as reaching the steering end, the piston 32 does not move even if hydraulic oil is supplied to the steering cylinder 26. You can know that the tire is locked. Nevertheless, when the steering wheel 12 is rotated in the same direction, the hydraulic oil supplied to the volume chamber 30a of the steering cylinder 26 is sent from the hydraulic line 44a to the oil tank 60 through the relief valve 54a. And the hydraulic pump 90
Since the hydraulic line 96b on the suction port 94b side has a negative pressure, the hydraulic oil is supplied from the oil tank 60 to the check valve 1
06b, and is returned to the hydraulic pump 90.

As described above, the steering can be performed even in the key-off state, which is effective, for example, when the forklift is towed due to the battery running out.

In the second embodiment, similarly to the first embodiment, when the tire is locked at the time of key-on, steering end, or the like, the control device 20 controls the steering angle sensor 4.
2 and the signal from the rotary encoder 18, the state can be detected.
00, the energization of the solenoid 104 is stopped, and the on-off valve 10
It is preferred that 0 be closed. Even when the key is on, if the tire lock occurs and the on-off valve 100 is closed, the state becomes the same as when the key is off, and the flow of hydraulic oil discharged from the hydraulic pump 90 is limited as described above,
This is because the handle 12 becomes heavy and the driver can recognize the tire lock.

In the first and second embodiments, the operation state of the steering wheel 12 is detected by the rotary encoder 18, but the operation state of the steering wheel may be detected by the torque sensor. FIG. 6 shows a hydraulic power steering device according to a third embodiment of the present invention using a torque sensor.

The hydraulic power steering apparatus shown in FIG. 6 is substantially the same as the power steering apparatus of the first embodiment shown in FIG. 1 with respect to the steering mechanism 14 having a steering cylinder 26 as a component. . However, the power steering device of FIG.
4 is not provided, and is a non-separable type in which the steering shaft 16 and the rotating shaft 50 of the hydraulic pump 46 are mechanically connected. More specifically, the steering shaft 16 and the rotating shaft 50 of the hydraulic pump 46 are connected by a joint 110 that enables relative angular displacement within a certain range. Although various types of such a joint 110 are considered such as a spring joint, a so-called mesh joint is used in the third embodiment.

As shown in FIG. 7, the meshing joint 110 is fixed to an engaging piece 112 projecting from the lower end of the steering shaft 16 in the radial direction and to the upper end of the rotary shaft 50 of the hydraulic pump 46. Groove 114 into which engaging piece 112 is fitted
And a cup-shaped member 116 having Since the width of the groove 114 is larger than the width of the engagement piece 112, the steering shaft 16 is rotatable within a certain range with respect to the rotation shaft 50 of the hydraulic pump 46.
Further, elastic members 118a and 118b are arranged between each engagement surface of the engagement piece 112 and a groove surface facing the engagement surface. A pair of elastic members 118a, 11 in each groove 114
8b are equal in thickness, so that the engagement piece 11
2 is arranged at the center of the groove 114. This elastic material 118
A pressure sensor (not shown) is incorporated in each of a and 118b so that the pressure or torque applied by the engagement piece 112 can be detected. The output signal of this pressure sensor (torque sensor) is
Sent to

The rotary shaft 50 of the hydraulic pump 46 is connected to the rotary shaft 5 of the electric motor 22 via a suitable transmission mechanism 120.
2 are connected. In the present embodiment, since the rotation speed of the rotating shaft 52 and the rotation speed of the steering wheel (steering shaft) 12 match, the electric motor 2
In the case where the rotation speed of No. 2 is higher than the rotation speed of the handle 12, the transmission mechanism 120 needs to have a deceleration function. The control of the electric motor 22 by the control device 20 is the same as in the first and second embodiments.

In such a configuration, when the steering wheel 12 is rotated in one direction, the elastic member 118a or 118b on the joint 110 in the same rotation direction is compressed according to the torque applied to the steering wheel 12, and the steering shaft 16 A relative angular displacement occurs between the hydraulic pump 46 and the rotating shaft 50. At this time, the torque applied to the handle 12 is detected by a pressure sensor in the compressed elastic member 118a or 118b, and the magnitude is detected by the control device 20. The control device 20 controls the driving of the electric motor 22 so that the rotation shaft 50 of the hydraulic pump 46 is rotated in the same direction as the steering shaft 16 at a rotation speed corresponding to the magnitude of the torque. The hydraulic pump 46 is the electric motor 2
As described above in the description of the first embodiment, the hydraulic oil is discharged from the ports 48a and 48b according to the rotation direction and supplied to the steering cylinder 26 to perform steering.

When the operation of the handle 12 is completed and the rotary shaft 50 of the hydraulic pump 46 is moved by the same amount as the rotation of the handle 12, the relative angular displacement between the steering shaft 16 and the rotary shaft 50 disappears, and the pressure is reduced. The output from the sensor returns to the initial state. Therefore, the control device 20 recognizes the end of the steering operation from the output of the pressure sensor, and
Stop supplying power to

The above operation is performed when the key is turned on. However, since the present embodiment is a non-separable type power steering device, the operating force from the steering wheel 12 can be directly transmitted to the hydraulic pump 46, and the operation is performed when the key is turned off. Even steering is possible.

FIG. 8 shows a modification of the hydraulic power steering apparatus according to the third embodiment. In this device, the driving force of the electric motor 22 is directly transmitted to the rotating shaft 50 of the hydraulic pump 46. Specifically, both ends of the rotary shaft 50 of the hydraulic pump 46 are projected from the pump casing, one end is connected to the rotary shaft 52 of the electric motor 22, and the other end is connected to the steering shaft 16 by the transmission mechanism 130. Connected through. Further, the steering shaft 16 includes the first shaft 1
6a and a second shaft 16b, and a joint 110 and a pressure sensor (torque sensor) capable of relative angular displacement similar to those shown in FIG. 7 are arranged between the two shafts.

The control method for such a configuration is the same as that of the power steering apparatus shown in FIG.
When the rotation speed of the hydraulic pump 46 is higher than the rotation speed of the handle 12, the discharge amount per rotation of the hydraulic pump 46 is as shown in FIG.
Must be smaller than the hydraulic pump shown in
In order to match the rotational speeds of the rotation shaft 50 and the steering shaft 16, the transmission mechanism 130 needs to have a speed increasing function.

Although the preferred embodiments of the present invention have been described in detail, it goes without saying that the present invention is not limited to the above embodiments.

For example, in the above embodiment, the steering cylinder 26 is a double rod type. However, if the steering mechanism is of a type in which a knuckle arm is connected to a bell crank by a tie rod (not shown), one steering rod is used. Therefore, a single rod type steering cylinder can be used.

As the means for detecting the operating state of the steering wheel 12 and the means for detecting the steering state of the steered wheels 10, various sensors other than the above-described encoder, torque sensor and potentiometer can be used. If the handle state detecting means or the like is changed to another type, the control method is also changed as appropriate.

The vehicle to which the present invention is applied is not limited to a forklift, but may be another industrial vehicle such as a shovel road.

[0068]

As described above, according to the present invention, 2
Since the hydraulic oil from the hydraulic pump is directly supplied to the double-acting steering cylinder using a directional flow type hydraulic pump, the response is good and there is no need to keep the hydraulic pump running all the time. . Therefore, it is possible to reduce the power consumption of the electric motor that operates the hydraulic pump,
This is particularly effective for battery vehicles.

Further, an expensive valve for switching the flow direction is not required, and the cost of the apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a hydraulic power steering device according to a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a load device that can be used in the power steering device of FIG.

FIG. 3 is a graph showing a relationship between a discharge side pressure of a hydraulic pump and a rotation speed of a handle in the load device of FIG. 2;

FIGS. 4A to 4C are hydraulic circuit diagrams showing modified examples of the load device, respectively.

FIG. 5 is an explanatory view schematically showing a hydraulic power steering device according to a second embodiment of the present invention.

FIG. 6 is an explanatory view schematically showing a hydraulic power steering device according to a third embodiment of the present invention.

FIG. 7 is a perspective view showing a structure of a joint used in the power steering device of FIG.

FIG. 8 is a schematic explanatory view showing a modification of the third embodiment of the present invention.

[Explanation of symbols]

Reference numeral 10: Steering wheel, 12: Steering wheel, 14: Steering mechanism, 16
... Steering shaft, 18 ... Rotary encoder (handle state detecting means), 20 ... Control device (control means), 22 ... Electric motor, 24 ... Load device, 26 ... Steering cylinder (hydraulic cylinder), 42 ... Steering angle sensor (Steering) State detecting means), 46... First hydraulic pump, 58
... bypass circuit (bypass means), 90 ... second hydraulic pump, 100 ... on-off valve, 102 ... bypass line, 11
0: Joint, 118a, 118b: Elastic material (torque sensor: handle state detecting means).

Claims (6)

[Claims] 1. A hydraulic power steering apparatus for steering a steered wheel by operating a steering wheel, wherein a double-acting hydraulic cylinder that steers the steered wheel, and discharge ports of two ports according to a rotation direction of a rotating shaft. A first hydraulic pump of a two-way flow type, wherein each of the ports is connected to each of the volume chambers of the hydraulic cylinder; and a reversible electric pump for operating the first hydraulic pump. A motor; a handle operation state detecting means for detecting an operation state of the handle; and a rotation axis of the first hydraulic pump in a predetermined direction based on the operation state of the handle detected by the handle operation state detection means. Control means for controlling the electric motor to rotate and supply hydraulic oil from one of the ports to a corresponding volume chamber of the hydraulic cylinder Hydraulic power steering apparatus comprising: a. 2. A steering state detecting means for detecting a steering state of the steered wheels, wherein the control means controls the electric motor based on a steering state of the steered wheels detected by the steering state detecting means. 2. The hydraulic power steering apparatus according to claim 1, wherein: 3. A bypass means for releasing hydraulic oil to another hydraulic line between hydraulic lines extending from each port of the first hydraulic pump when the pressure of one hydraulic line exceeds a predetermined value. The hydraulic power steering device according to claim 1 or 2, further comprising: 4. A rotating shaft which is rotated by a torque from the handle, wherein a discharge side of two ports is switched according to a rotating direction of the rotating shaft. A two-way flow type second hydraulic pump communicating with each volume chamber of the hydraulic cylinder, and a hydraulic pressure line extending from each port of the second hydraulic pump and having a normally closed on-off valve The hydraulic power according to any one of claims 1 to 3, wherein the control unit controls to open the on-off valve when an ignition switch of the vehicle is turned on. Steering device. 5. The hydraulic system according to claim 4, wherein the control device controls the on-off valve to close when a tire lock occurs while an ignition switch of the vehicle is turned on. Power steering device. 6. A rotating shaft of the first hydraulic pump and the handle are mechanically connected to each other so as to be transmitted mechanically, and a torque applied from the handle to a rotating shaft of the first hydraulic pump is applied to the electric motor. The control means controls the electric motor so that the electric motor is assisted.
4. The hydraulic power steering device according to claim 3.