JPS60261779A - Fully hydraulic type power steering device - Google Patents

Abstract

PURPOSE:To correct the position of a steering handle displaced from the right position by providing a working oil flowing means which is used for compensate the position of the steering handle, in an oil pressure line which connects a steering unit to a steering wheel driving actuator. CONSTITUTION:When a steering unit 2 is driven by the operation of a steering handle 1, oil pressure from a pump 7 is sent into one half of a steering cylinder 4. The cylinder 4 therefore has the steering wheel steered in the same direction as that in which the steering handle 1 is operated. When the steering handle 1 is not in the forward traveling neutral position even if the steering wheel is held in said forward traveling neutral position, because oil leaks inside the steering unit 2, a manual change-over valve 15 which is disposed in oil pressure lines 5 and 6 is changed over to either one of positions to have working oil drained into a tank 8 from one of the oil pressure lines 5 and 6. Thus, the steering handle 1 can be idled and put into the neutral position without shifting operation of the steering cylinder 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fully hydraulic power steering system used in vehicles such as forklift trucks and without a steering gear or mechanical link.

(Prior Art) As a conventional fully hydraulic power steering device, for example, a device as shown in FIG. 5 is known. (Refer to "Nissan Technical Report No. 19J, published by Nissan Motor Co., Ltd., December 9, 1981; pages 170 to 171.") This conventional device has a steering unit 2 (valve mechanism) operated by a steering wheel l, and a steering wheel 3. The vehicle was equipped with a steering cylinder 4 (actuator) for steering, and hydraulic lines 5 and 6 connecting the steering unit 2 and the steering cylinder 4.

In Figure 1, 7 indicates a steering pump, 8 a hydraulic oil tank, 9 a vehicle body, 10 a steering chain, 11 a fixed wheel, and 12 a handle spoke. This figure shows the state when steering to the left.

By steering the steering wheels 3 to the right, the vehicle can turn to the left.

Therefore, by rotating the steering wheel l in the steering direction, an amount of pressure oil sent from the steering pump 7 that is proportional to the steering wheel rotation angle is sent from the steering unit 2 to the steering cylinder 4 according to the arrow in the figure.

The pressure oil sent to the steering cylinder 4 enters the steering cylinder 4 through the hollow part of the cylinder rod 41, and since the cylinder rod 41 is fixed to the vehicle body 9, the cylinder tube 42 changes depending on the amount of oil fed. The steering wheel 3 connected by the steering chain 10 is rotated by an angle corresponding to the rotation angle of the handle l.

(Problems to be Solved by the Invention) However, in such a conventional fully hydraulic power steering device, the steering unit 2 and the steering cylinder 4 are connected only by the hydraulic line 5.6, and the steering gear Because there was no mechanical link, oil leakage inside the steering unit 2 caused a discrepancy between the amount of oil sent to the steering cylinder 4 and the rotation angle of the steering wheel 1.
There was a possibility that the relative position of the steering wheel spokes 12 and the steering wheel 3 would change.

In particular, if the steering wheel 1 is shifted from the neutral position even though the steering wheel 3 is in the straight-ahead neutral position, even if the operator tries to turn the steering wheel 1 to make a curve, the steering wheel 3 is actually in the straight-ahead neutral position. There were times when I would run away.

(Means for Solving the Problems) That is, the present invention was made for the purpose of solving the two problems, and in order to achieve the purpose, the present invention provides a steering unit operated by a steering wheel, A fully hydraulic power steering device that hydraulically steers the steered wheels in response to an operation of the handle, comprising: an actuator that steers a steered wheel; and a hydraulic line that connects the steering unit and the actuator; It is equipped with a switching valve and a hydraulic oil outflow means to correct the position of the handle. 1 (Function) Therefore, when the position of the handle and the position of the steering wheel do not match, the position of the handle can be corrected by draining the hydraulic oil in the hydraulic line from the hydraulic oil draining means.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In describing the embodiment, we will take a fully hydraulic power steering device for a three-wheeled forklift truck as an example.
The same parts as those in the conventional structure will be described with the same reference numerals.

First, the configuration of the first embodiment shown in FIGS. 1 and 2 will be explained.

Reference numeral 1 denotes a handle, and the handle 1 is provided with handle spokes 12 to improve operability. Reference numeral 2 denotes a steering unit, which is directly operated by the handle l; is a lubricating mechanism, which has a function of sending an amount of pressure oil sent from a steering pump 7, which will be described later, to the steering cylinder 4 in an amount proportional to the rotation angle of the steering wheel.

4 is a steering cylinder, which includes a cylinder rod 41.41 fixed to the vehicle body 9, a cylinder tube 42 that is a movable member, and a piston 43 that reciprocates within the cylinder tube 42.

It is equipped with

Reference numeral 3 denotes a steering wheel, which is connected to the cylinder tube 42 by a steering chain 10.10, and is steered by movement of the cylinder duplex 4.

5.6 is a hydraulic line that connects the steering unit 2 and the steering cylinder 4;
One of the hydraulic lines 5.6 serves as a feed line for supplying pressurized hydraulic oil from the steering pump 7 during steering, and the other line serves as a return line for returning oil to the hydraulic oil tank 8.

Note that a cylinder rod 41 is connected to the steering cylinder 4.
Pressurized oil is sent through the hollow part of the sleeve, and the sleeve is also returned through the hollow part.

13.14 is a drain oil line as a hydraulic oil draining means, which is connected to the hydraulic line 5.6,
A manual switching valve 15 is provided in the middle of this drain oil line 13. A switch is made between whether to drain the oil to the oil tank 8 or not.

In the figure, 16 indicates a pump pressure line, and 17 indicates a return line. When the /S steering wheel 1 is in the neutral state, all the oil sent from the steering pump 7 to the steering unit 2 passes through the return line 17. Hydraulic oil tank 8
will be returned to.

Further, 18 in the figure is a connection line to the hydraulic oil tank 8.

Next, the operation of the first embodiment will be explained.

During steering, by rotating the steering wheel 1 in the steering direction, the steering pump 15 sends pressure oil out of the pressure oil, and the amount of oil proportional to the angle is transferred from the steering unit 2 to the hydraulic lines 5 and 6. This is done by rotating the steering wheel 3 by an angle corresponding to the rotation angle of the steering wheel 1.

Even though the steering wheel 3 is in the straight-ahead neutral position, if oil leaks inside the steering unit 2 and the handle l is not in the straight-ahead neutral position, switching the manual switching valve 15 to one side will supply hydraulic oil. Since the hydraulic oil is drained from one of the hydraulic lines 5 and 6 through one of the drain oil lines 13 and 14 to the hydraulic oil tank 8t, the steering cylinder 4 remains in the neutral position without moving. This allows the handle l to be rotated idly.

Then, if you turn the steering wheel 1 to the straight neutral position,
When the manual switching valve 15 is returned to its original neutral position, the steering wheel 3
The straight neutral position of the handle 1 can be made to coincide with the straight neutral position of the handle 1.

Next, a second embodiment shown in FIG. 3 will be described. 1. Unlike the first embodiment, which only had a straight-ahead neutral position correction function, this embodiment allows rotation of the steering wheel l according to the steering angle of the steering wheel 3, regardless of the position of the steering wheel 3. This is an example in which position correction can be performed.

Here, to explain the configuration different from the first embodiment, 19 is a cylinder stroke detection means, which is arranged with respect to the cylinder tube 4 of the steering cylinder 4, detects the cylinder stroke, and outputs a stroke signal (S). The steering angle of the steered wheels 3 is indirectly detected by this cylinder stroke.

Reference numeral 20 denotes a handle rotation angle detection means, and the handle 1
It is arranged on the steering shaft 21 of the steering wheel, detects the rotation angle of the steering wheel, and outputs an angle signal (θ).

22 is an electromagnetic switching valve, which has a first solenoid 23 and a second solenoid.
A switching operation is performed by energizing either the first solenoid 23 or the second solenoid 24.

25 is a controller which includes an arithmetic circuit which inputs the angle signal (θ) and calculates a target cylinder stroke Sk according to the handle rotation angle θ, and which differentiates the handle rotation angle θ or the target cylinder stroke Sk with respect to time t. Then, a discrimination circuit that discriminates the steering direction compares the actual cylinder stroke Sj from the stroke signal (S) with the target cylinder stroke Sk, and determines whether the first solenoid 23
Alternatively, a comparator that outputs the solenoid drive signals (a) and (b) to the second solenoid 24 is provided. In this embodiment, the steering wheel rotation angle θ, target cylinder stroke Sk, and actual cylinder stroke Sj have a value of zero when the steering wheel 1 is steered to the leftmost position, and increase to positive values as the steering wheel 1 is steered further to the right. Define it so that

Note that the target cylinder stroke Sk is set in advance to be smaller than the actual cylinder stroke Sj, and the relationship between the handle rotation angle θ and the target cylinder stroke Sk is stored in the storage section of the controller 25.

Note that the other configurations are the same as those in the first embodiment, so the same reference numerals are given and the explanation will be omitted.

Next, the operation of the third embodiment will be explained.

Explaining according to the flowchart shown in FIG. 4, first, the handle rotation angle θ is detected by the handle rotation angle detection means 20.

Then, based on the handle rotation angle θ, the controller 25 calculates a target cylinder stroke Sk that has a predetermined relationship with the handle rotation angle θ.

Next, the actual cylinder stroke Sj is detected by the cylinder stroke detection means 19.

Next, the steering wheel rotation angle θ or the target cylinder stroke Sk is differentiated with respect to time, and depending on whether the value is positive or negative, it is determined whether the steering direction is right or left. Note that if it is 0 (zero), the handle 1 is in a fixed state with no turning to the left or right, and at this time, the electromagnetic switching valve 22 is left in the neutral position. In other words, to avoid giving the driver a sense of discomfort, the steering wheel position is not corrected when the vehicle is traveling straight or when the steering wheel is being held.

Next, the target cylinder stroke Sk and the actual cylinder stroke Sj are compared, and the actual cylinder stroke Sj
Solenoid drive signals (, lL), (
b) is output, the electromagnetic switching valve 22 is switched to drain the hydraulic oil from one of the hydraulic lines 5 and 6, and the handle 1 is
is corrected so that it becomes a rotation angle according to the target cylinder stroke Sk. Since the cylinder stroke and the steering angle of the steering wheel 3 have a certain relationship, the steering wheel 1 can be used to steer the steering wheel 3. The rotation angle will be corrected according to the angle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The specific configuration is not limited to this embodiment, and any design changes or the like that do not depart from the gist of the present invention are included in the present invention.

For example, in the embodiment, there are 7 actuators, 2. ．． 7 cases. 1. ．． 79, □, □1. The actuator is not limited to one type, and may be a hydraulic actuator that moves in a rotating direction or in a curved manner.

In addition, in the embodiment, two drain oil lines are used as a hydraulic oil outflow means, but correction is made by rotating only one side of the handle (clockwise or counterclockwise rotation) using a single drain oil line. Good too.

Further, in order to improve safety, the manual switching valve in the first embodiment may include a mechanism that allows switching only when the vehicle is stopped, such as a mechanism linked to a handbrake.

Further, in the second embodiment, the cylinder stroke detection means may be replaced with a steering angle detection means for the steered wheels.

(Effects of the Invention) As described above, according to the present invention, since the position of the steering wheel relative to the position of the steering wheel can be corrected by the hydraulic oil spill means, the relative position change between the steering wheel and the steering wheel due to oil leakage can be corrected. The effect is that it can be eliminated.

Further, since the correction is performed by draining the hydraulic oil from the hydraulic line, air contained in the hydraulic oil can be removed.

Furthermore, in addition to the above-mentioned effects, the first embodiment is extremely simple in terms of structure, since it is only necessary to add a drain oil line and a manual switching valve.

Furthermore, in the second embodiment, the relationship between the target cylinder stroke and the handle rotation angle is set not only as a linear relationship but also as appropriate.

It is also possible to have steering performance that changes depending on the steering wheel rotation angle. For example, when the steering wheel is near the neutral position for straight-ahead driving, the steering angle of the steering wheel is made smaller relative to the steering wheel rotation angle in order to improve the stability of straight-ahead driving, and when the steering wheel is at maximum rotation, the steering angle of the steering wheel is made smaller to improve steering stability. It is also possible to increase the steering angle of the steered wheels relative to the steering wheel rotation angle.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a three-wheel forklift truck equipped with a fully hydraulic power steering device according to the first embodiment of the present invention, FIG. 2 is a hydraulic circuit diagram showing the device according to the first embodiment, and FIG.
The figure is a hydraulic circuit diagram showing the device of the second embodiment, FIG. 4 is an operation flowchart of the device of the second embodiment, and FIG. 5 is a plan view showing a three-wheeled forklift truck equipped with a conventional fully hydraulic power steering device. be. ■... Handle 2... Steering unit 3... Steering wheel 4... Steering cylinder (actuator) 5.
6...Hydraulic line 13.14...Drain oil line (hydraulic oil outflow means) Patent application Nissan Motor Co., Ltd. 0 565-

Claims (1)

[Scope of Claims] 1) A steering unit that is operated by a steering wheel, an actuator that steers a steering wheel, and a hydraulic line that connects the steering unit and the actuator, in response to the operation of the steering wheel, A fully hydraulic power steering device for hydraulically steering steering wheels, characterized in that the hydraulic line is equipped with a switching valve, and a hydraulic oil outflow means for correcting the position of the steering wheel is provided. 2) The switching valve operates upon detecting that the difference between the target stroke of the actuator corresponding to the handle angle and the actual stroke of the actuator exceeds a predetermined value. Fully hydraulic power steering system as described.