JP2000025627A - Hydraulic power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve steering follow-up traveling property in a low speed area of a vehicle, improve stable feeling of steering in a high speed area and prevent generation of a shimmy phenomenon and a kickback phenomenon by varying a damper effect according to engine speed of an internal combustion engine, in a hydraulic power steering device having a damper valve. SOLUTION: In a hydraulic power steering device 1 constituted by disposing a damper valve 10 in hydraulic fluid circuits 8, 9 connecting an oil path switching valve 11 within a gear box and left and right oil chambers of a power cylinder 6, the damper valve 10 is constituted of a spool valve, a control oil chamber 21 of the spool valve 10 is connected with a hydraulic fluid supply path 18 connecting a hydraulic pump 13 which is driven by an internal combustion engine and discharges hydraulic fluid and an oil path switching valve 11, and opening of the spool valve 10 is made larger when discharge hydraulic pressure of the hydraulic pump 13 rises.

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 system for a vehicle having a damper valve, and more particularly to a vehicle in which the damper effect is variable in accordance with the rotational speed of an internal combustion engine to steer the vehicle in a low speed range. TECHNICAL FIELD The present invention relates to a hydraulic power steering device that improves the steering performance and the stability of steering in a high-speed range.

[0002]

2. Description of the Related Art Conventionally, a hydraulic power steering apparatus used in a vehicle, wherein a damper valve is disposed in a hydraulic oil circuit connecting an oil passage switching valve in a gear box and left and right oil chambers of a power cylinder. As a power steering device, one described in Japanese Utility Model Publication No. 2-49109 is known.

In this case, as shown in FIG. 5, a hydraulic oil circuit 08 for connecting an oil passage switching valve 011 housed in a gear box of a hydraulic power steering device 01 to left and right oil chambers of a power cylinder 06. Check valves 01 and 09 permit oil flow only from the oil passage switching valve 011 to the left and right oil chambers.
0a, 010a, having an initial load, and an oil passage switching valve 01 from the oil chamber side.
Throttle check valve 010b, 01 that allows oil flow only to the 1 side
0b is provided. And these check valves 01
0a, 010a and the throttle check valves 010b, 010b constitute a damper valve.

A hydraulic pump 013, which is a hydraulic source for supplying hydraulic oil to the power cylinder 06, includes a flow control valve 023, a relief valve 024, and a fixed orifice 025. The hydraulic oil is discharged at a discharge amount according to the characteristic diagram shown in FIG.

That is, in a low rotation speed region until the rotation speed of the hydraulic pump 013 reaches a predetermined low speed rotation speed N, an amount of hydraulic oil which gradually increases and reaches a substantially constant high level is discharged. When the pressure exceeds N, the amount of hydraulic oil that gradually decreases and reaches a substantially constant low level is discharged. The hydraulic pump 013 is connected to a crankshaft of an internal combustion engine (not shown) via a transmission mechanism, and has the same rotation speed as the rotation speed of the internal combustion engine.

The above-mentioned conventional hydraulic power steering apparatus
Since the damper valve in 01 does not have a portion where friction occurs, the return performance of the steering handle is good. In addition, since the throttle check valves 010b and 010b have an initial load, even if the rack shaft 04, which also serves as the piston rod of the power cylinder 06, tries to vibrate minutely due to tire imbalance or the like, the left and right oil The flow of hydraulic oil from the chamber side to the oil passage switching valve 011 side is suppressed, and the rack shaft 04 hardly moves, so that the so-called shimming phenomenon, in which the steering handle slightly vibrates, can be prevented. 012 is a reservoir tank.

[0007]

However, the conventional damper valve has the same damper effect irrespective of the rotational speed of the internal combustion engine (the rotational speed of the hydraulic pump) and the speed of the vehicle. When the vehicle is rotating or the vehicle is running at a low speed, the damper effect is not so necessary. On the other hand, the damper effect is necessary when the speed is low, but the damper effect cannot be adjusted according to the degree of such a need. For this reason, there is still room for improvement in the turning followability (turning ability) of the steering wheel particularly in a low speed range of the vehicle.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and makes the damper effect of a damper valve variable according to the rotation speed of an internal combustion engine. It is an object of the present invention to provide a hydraulic power steering device which can improve the steering performance in a high-speed region of a vehicle, and at the same time can prevent the occurrence of a shimmy phenomenon and a kickback phenomenon.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a hydraulic power steering apparatus which solves the above-mentioned problems.
In a hydraulic power steering apparatus in which a damper valve is provided in a hydraulic oil circuit that connects an oil passage switching valve in a gear box and left and right oil chambers of a power cylinder, the damper valve includes a spool valve, and the spool valve The control oil chamber is connected to a hydraulic oil supply path that connects a hydraulic pump driven by an internal combustion engine to discharge hydraulic oil and the oil path switching valve, and when the discharge hydraulic pressure of the hydraulic pump increases, the spool valve The hydraulic power steering device is characterized in that the opening degree of the hydraulic power steering device is increased.

According to the first aspect of the present invention, since it is configured as described above, it constitutes a damper valve disposed in a hydraulic oil circuit connecting the oil passage switching valve and the left and right oil chambers of the power cylinder. The spool valve has a control oil chamber connected to a hydraulic oil supply path that connects a hydraulic pump driven by an internal combustion engine to discharge hydraulic oil and an oil path switching valve, and is operated according to a discharge hydraulic pressure of the hydraulic pump. When the discharge oil pressure rises, the valve opening is increased.

As a result, when the rotation speed of the internal combustion engine is low and therefore the rotation speed of the hydraulic pump is low and the discharge amount of the hydraulic oil increases based on the characteristic diagram of the power steering, the steering handle is steered. As a result, the discharge pressure of the hydraulic oil also increases, so that the opening of the damper valve is opened, and the hydraulic oil circuit is largely opened. As a result, the hydraulic oil easily flows through the circuit, the damper effect of the damper valve is weakened, the turning followability of the steering wheel in a low-speed range of the vehicle is improved, and a light feeling of steering is obtained. Become.

Also, when the rotation speed of the internal combustion engine is high and therefore the rotation speed of the hydraulic pump is high and the discharge amount of hydraulic oil is reduced based on the characteristic diagram of the power steering, even if the steering wheel is steered. Since the discharge pressure of the hydraulic oil does not increase so much, the opening degree of the damper valve is closed, and the hydraulic oil circuit is opened small. This allows
It becomes difficult for hydraulic oil to flow through the circuit, the damper effect of the damper valve is exerted, the steering followability of the steering wheel in the high-speed range of the vehicle is reduced, the sense of wobble in the neutral state is reduced, and the steering is stabilized. A feeling can be obtained.

Further, in this case, the damper valve exerts its original damper effect, so that the piston rod (rack shaft) of the power cylinder is moved from the wheel side.
The occurrence of minute vibration (shimmy phenomenon) transmitted to the steering wheel via the vehicle during traveling of the vehicle is suppressed. Also,
The so-called kickback phenomenon, in which the steering handle reverses when the wheel rides on a stone or the like, is also suppressed. As a result, steering comfort is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the invention described in claim 1 of the present application shown in FIGS. 1 to 4 will be described below. FIG. 1 is an overall configuration diagram of a hydraulic power steering device according to the present embodiment, FIG. 2 is a schematic configuration diagram of the hydraulic power steering device of FIG. , FIG. 4 is a partially enlarged view of FIG.
FIG. 2 is a characteristic diagram of a hydraulic pump in the hydraulic power steering device of FIG. 1.

Referring to FIG. 1, a hydraulic power steering apparatus 1 according to the present embodiment is a rack and pinion type power steering apparatus, in which an input shaft 2 connected to a steering handle of a vehicle (not shown) switches a gear box 3. A rack shaft 4 having a rack connected to an output shaft (pinion shaft) (not shown) via a torsion bar and engaged with a pinion formed in the output shaft is provided in the valve housing portion 3a. 1 is housed in the power cylinder housing portion 3b so as to be slidable left and right in FIG.

A pair of left and right tie rods 5, 5 are connected to both ends of the rack shaft 4, and a piston 7 of a power cylinder 6 housed in the rack shaft / power cylinder housing portion 3b is connected to an intermediate portion. Have been. Therefore, the rack shaft 4 also serves as a rod of the piston 7.

An oil passage switching valve 11 (rotary valve; see FIG. 2) is accommodated in the switching valve accommodation portion 3a of the gear box 3, and the oil passage switching valve 11 is provided with a distortion amount of the torsion bar. That is, the valve opens according to the relative rotation amount difference between the input shaft 2 and the output shaft, and the hydraulic oil pumped from the hydraulic pump 13 as the hydraulic pressure source via the hydraulic oil supply passage 18 is left The oil is supplied to one of the left and right oil chambers of the power cylinder 6 via the right cylinder oil passage 8 or the right cylinder oil passage 9, and the right cylinder oil passage 9 or the left cylinder oil is supplied from the other of the left and right oil chambers of the power cylinder 6. The hydraulic oil returned via the passage 8 is returned to the reservoir tank 12 via the hydraulic oil return passage 19.

The hydraulic pump 13 is not shown, but
The engine is connected to a crankshaft of the internal combustion engine via a transmission mechanism, and rotates at the same rotational speed as the internal combustion engine. As shown schematically in FIG. 2, a flow control valve 23, a relief valve 24 and a fixed orifice 25 are provided, and by the cooperation of these, the characteristic shown in FIG. Discharge the working oil in the discharge amount according to the diagram. This characteristic diagram is the same as the characteristic diagram of the conventional hydraulic pump 013.

Therefore, when the rack of the output shaft meshes with the pinion and the rack shaft 4 moves left and right,
The tie rods 5, 5 integrally move left and right according to the left and right movement to steer the left and right wheels, and are discharged from the hydraulic pump 13 in accordance with the rotation speed of the internal combustion engine and controlled to be switched by the oil passage switching valve 11. The operating oil is supplied to one of the left and right oil chambers of the power cylinder 6, and the piston 7, the rack shaft 4, and the tie rods 5, 5 move integrally left and right to superimpose steering of the left and right wheels based on the steering assist force. It is supposed to do it.

Here, as shown in FIG. 1, a damper valve 10 is mounted on a casing of the switching valve housing portion 3a of the gear box 3. As shown in detail in FIGS. 2 and 3, the damper valve 10 includes a spool valve, and a left and right cylinder oil passage (hydraulic oil circuit) connecting the oil passage switching valve 11 and the left and right oil chambers of the power cylinder 6. These oil passages can be opened and closed at the same time, and the damper effect can be adjusted strongly.

Therefore, when the oil passages 8 and 9 are throttled to enhance the damper effect, even if vibrations from the wheels are transmitted to the power cylinder 6 during traveling of the vehicle, the piston 7 and the rack shaft 4 Since the lateral movement is suppressed, it is possible to suppress the transmission of the vibration to the steering handle (not shown) via the rack shaft 4. Thus, it is possible to prevent the occurrence of the shimmy phenomenon in which the steering handle slightly vibrates.

Also, when a wheel rides on a stone,
The so-called kickback phenomenon, in which the steering wheel is reversed, can be prevented for the same reason. As a result, steering comfort is improved. As described below, the damper effect of the damper valve 10 is made variable according to the rotation speed of the internal combustion engine.

Next, the detailed structure and operation of the damper valve 10 and the effects of this embodiment will be described. The damper valve 10 is provided with a spool in a spool housing hole 16 of a valve casing (sleeve) 26 as better shown in FIG.
14 in one direction by spring 15 (left direction in FIG. 2)
And the land part 14a at the center
Are formed on both sides thereof with annular U-shaped grooves 14b and 14c.

These annular U-shaped grooves 14b, 14c come into contact with and separate from the port portions 8a, 9a in which the left and right cylinder oil passages 8, 9 open into the spool housing hole 16, and these port portions 8a
, 9a, the degree of opening of these oil passages 8, 9 is adjusted.

A control oil chamber 21 to which the operating oil pressure for moving the spool 14 of the damper valve 10 is supplied is formed on the left end side of the spool accommodating hole 16 in FIG. Connected to the discharge side of the hydraulic pump 13.
The back pressure chamber 17 on the right end side of the spool housing hole 16 in which the spring 15 is housed is connected to the reservoir tank 12 via an oil passage 20 and a return passage 19.

Therefore, when the rotation speed of the internal combustion engine is low, the rotation speed of the hydraulic pump 13 is lower than N in the characteristic diagram of FIG. 4, and the discharge amount of the hydraulic oil is relatively large, the steering handle is steered. Then, a throttle action occurs in the oil passage switching valve 11 and the discharge pressure of the hydraulic oil increases, so that the damper valve
The high pressure of the hydraulic oil acts on the control oil chamber 21 of 10, and the spool
2 is moved to the right in FIG. 2 by overcoming the urging force of the spring 15.

Then, the annular U-shaped groove 14b of the spool 14
, 14c are port portions 8a of the left and right cylinder oil passages 8, 9,
9a, the left and right cylinder oil passages 8, 9 are opened to a greater extent (the opening degree of the damper valve 10 is large), so that the hydraulic oil easily flows through these oil passages. Damper effect is weakened.

As described above, when the damper effect of the damper valve 10 is weakened, the left and right movement of the rack shaft 4 is performed smoothly, so that the steering of the steering handle becomes light and the steering is easily performed. Steering followability is improved. In addition, since the followability of the return of the steering handle is also improved, a light feeling of steering can be obtained. Thus, normal power assist is performed.

In this case, the minute vibration during traveling of the vehicle transmitted from the wheel side (not shown) to the power cylinder 6 is slightly transmitted to the steering handle via the left and right movement of the rack shaft 4, and a shimming phenomenon occurs. ,
Since the internal combustion engine is rotating at low speed, no problem occurs.

When the rotation speed of the internal combustion engine is high, the rotation speed of the hydraulic pump 13 is higher than N in the characteristic diagram of FIG. 4, and the discharge amount of hydraulic oil is relatively small, the steering wheel is steered to Even if the throttling action occurs in the path switching valve 11,
Since the discharge pressure of the hydraulic oil does not increase so much, a low pressure of the hydraulic oil acts on the control oil chamber 21 of the damper valve 10 to move the spool 14 to the left in FIG.

Then, the annular U-shaped groove 14b of the spool 14
, 14c are port portions 8a of the left and right cylinder oil passages 8, 9,
9a, the left and right cylinder oil passages 8 and 9 are narrowed (the opening degree of the damper valve 10 is small), and it becomes difficult for hydraulic oil to flow through these oil passages.
The damper effect is enhanced.

As described above, when the damper effect of the damper valve 10 is enhanced, the left and right movements of the rack shaft 4 are not smoothly performed, so that the steering of the steering handle becomes heavy and the steering becomes difficult to turn. Steering followability decreases. As a result, the sense of wobble at the neutral position at high speed of the vehicle is reduced, and a sense of stability of steering can be obtained.

In this case, since the damper valve 10 exhibits its original damper effect, the minute vibration (shimmy phenomenon) transmitted to the steering handle from the wheel side (not shown) via the rack shaft 4 during the vehicle running is obtained. Generation is suppressed. In addition, the occurrence of a kickback phenomenon in which the steering wheel is reversed when the wheel rides on a stone is also suppressed for the same reason. As a result, steering comfort is improved.

In this embodiment, the damper valve 10
Is mounted on the casing of the switching valve accommodating portion 3a of the gear box 3, but is not limited to this. The hydraulic oil connecting the oil passage switching valve 11 in the switching valve accommodating portion 3a and the left and right oil chambers of the power cylinder 6 is provided. What is necessary is just to install in the circuit 8 and 9 in the place which can be made on a layout.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a hydraulic power steering device according to an embodiment of the invention described in claim 1 of the present application.

FIG. 2 is a schematic configuration diagram of the hydraulic power steering device of FIG. 1, with a part cut away.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a characteristic diagram of a hydraulic pump in the hydraulic power steering device of FIG.

FIG. 5 is a diagram showing a conventional example.

[Explanation of symbols]

1. Hydraulic power steering device 2. Input shaft 3.
Gear box, 3a: switching valve housing part, 3b: rack shaft / power cylinder housing part, 4 ... rack shaft, 5 ... tie rod, 6 ... power cylinder, 7 ... piston, 8 ... left cylinder oil passage, 8a ... port part , 9 ... right cylinder oil passage, 9a ... port, 10 ... damper valve, 11 ... oil passage switching valve (rotary valve), 12 ... reservoir tank, 13 ... hydraulic pump, 14 ... spool, 14a ... land, 14b , 14c ... annular groove, 15 ... spring, 16 ... spool storage hole, 17 ... spring storage chamber, 18 ... hydraulic oil supply path, 19 ... hydraulic oil return path, 20 ... oil path, 21 ... control oil chamber, 22 ...
Oil passage, 23: flow control valve, 24: relief valve, 25: fixed orifice, 26: valve casing (sleeve).

Claims (1)

[Claims] 1. A hydraulic power steering system in which a damper valve is provided in a hydraulic oil circuit that connects an oil passage switching valve in a gear box and left and right oil chambers of a power cylinder, wherein the damper valve is provided from a spool valve. The control oil chamber of the spool valve is connected to a hydraulic oil supply passage connecting the hydraulic pump driven by an internal combustion engine to discharge hydraulic oil and the oil passage switching valve, and the discharge hydraulic pressure of the hydraulic pump has increased. The hydraulic power steering apparatus is characterized in that the opening of the spool valve is increased.