KR101488286B1 - Hydraulic power steering apparatus having limiter - Google Patents

Abstract

The present invention relates to a hydraulic power steering apparatus in which a chamber inside a housing is partitioned by a piston into a left compartment and a right compartment and a piston is moved by a hydraulic pressure difference in the left compartment and the right compartment, Pressure line and a low-pressure line. The high-pressure line and the low-pressure line are connected to the direction control valve for selectively supplying and recovering hydraulic fluid to the left compartment or the right compartment according to the rotation of the steering wheel. And a limiter for opening the high-pressure line and the low-pressure line when the hydraulic pressure in the high-pressure line exceeds the critical pressure, is connected to the high-pressure line, And the piston is moved in accordance with the opening / closing state of the direction control valve Characterized in that the threshold pressure determined depending on whether or not movement of the piston.

The present invention having the above-described structure has an effect of suppressing a load generated in each component due to an excessive increase in hydraulic pressure occurring in the gear box of the power steering.

High pressure line, direction control valve, limiter

Description

Technical Field [0001] The present invention relates to a hydraulic power steering apparatus having a limiter,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic power steering apparatus for a vehicle, and more particularly, to a hydraulic power steering apparatus configured to prevent an excessive hydraulic pressure from being generated inside a housing.

A steering apparatus is a device that is operated to change the traveling direction of a vehicle according to a driver's intention, and is a device for converting the rotational motion of a steering wheel into a turning motion of a load wheel.

The steering device is classified into a manual steering device and a power steering device (power steering device) depending on the presence or absence of a power assist device for supporting rotation.

In recent years, a power steering apparatus is mounted on almost all vehicles in order to improve the ease of operation, and the power steering apparatus is largely divided into a hydraulic type and a motor type.

The motor type is used for a small-sized vehicle having a relatively small load, and the hydraulic type is mainly used for an advanced vehicle and a large-sized bus.

The hydraulic system includes an operating device including a steering shaft, a steering column, and a joint coupled with a steering wheel, a gear device connected to the operating device for generating a driving force in accordance with the rotational direction of the operating device, As shown in Fig.

The gear device includes a sensor for sensing the degree of rotation of the steering wheel, a hydraulic pump, and a controller for controlling the hydraulic pump, and controls the flow and pressure of the hydraulic fluid so that the piston slides according to a predetermined process. The sliding piston is threaded in the longitudinal direction on the outer circumference and the thread is mated with the thread of the sector shaft which pivots the rod wheel to form a rack and pinion.

In addition, the piston may be connected to an operating device through which a rotational force is directly transmitted from the steering wheel, such as a worm gear, so that the piston can be slid without oil pressure.

However, when the load wheel is in the maximum rotational angle state in the gearbox, the maximum hydraulic pressure that is applied gives a great load to each component such as a steering gear, a hydraulic pump and a ring cage mechanism, Durability.

In addition, in the frequent maximum rotation angle state and the maximum maximum rotation angle state, the temperature of the power steering fluid may increase, and the normal function of the power steering may not be exhibited properly.

In particular, the greater the likelihood that such a problem would occur more frequently when larger hydraulic pressures such as heavy trucks or buses were operating. Further, in the case of a large-sized vehicle, the hydraulic pressure higher than the hydraulic pressure acting during traveling is set to the atmospheric pressure so that the steering can be performed even in the stationary state. Therefore, it was necessary to lower the atmospheric pressure in the high-pressure line when the steering was not input.

Accordingly, it is a primary object of the present invention to provide a power steering apparatus that suppresses an increase in hydraulic pressure even when the steering oil pressure continuously increases in a maximum rotation angle state, as well as when steering is not input.

To achieve the above object, the present invention provides a hydraulic power steering apparatus in which a chamber inside a housing is partitioned by a piston into a left compartment and a right compartment, and a piston moves by a hydraulic pressure difference in the left compartment and the right compartment And the hydraulic oil supplied to the chamber is supplied from a hydraulic pump through a high-pressure line and is recovered through a low-pressure line. The high-pressure line and the low-pressure line are connected to selectively connect the hydraulic oil to the left compartment or the right compartment And the other end is branched and connected to the low-pressure line. When the hydraulic pressure in the high-pressure line exceeds the critical pressure, the high-pressure line and the high-pressure line are connected to each other. And a limiter for opening the low-pressure line, But the piston is moved along the closed state, characterized in that the threshold pressure determined depending on whether or not movement of the piston.

Wherein the limiter is formed with a relief mounting chamber and a plunger mounting chamber in which a first stepped chamber is formed on the upper side and a second stepped chamber having an inner diameter smaller than that of the first stepped chamber is formed on the lower side, A second flow path connecting the low pressure line to one side of the relief mounting chamber, a third flow path connecting the plunger mounting chamber to the direction control valve, and a second flow path connecting the plunger mounting chamber to the chamber A fifth flow path connecting the first stepped chamber and the plunger mounting chamber and a sixth flow path connecting the relief mounting chamber to the plunger mounting chamber and a second stepped chamber connected to the second flow path by a plunger And a lower end connected to the relief plate so as to be slid in the relief mounting chamber so as to slide in the second step chambers, wherein the first step chambers and the plunger mounting chambers are closed at an upper end in a tapered shape, And the other side is formed with a third flow path and a fourth flow path formed along the outer circumferential surface so as to connect the seventh flow path with the fifth flow path or the sixth flow path, A relief spring mounted on the relief plunger so as to close the first step chambers; And a plunger spring mounted to the flow check plunger to close the third flow path and the fourth flow path and to open the sixth flow path and the seventh flow path.

로 정해지는 것을 특징으로 한다. 이때, 'K'는 릴리프스프링의 스프링상수이고, 'δ'는 릴리프스프링이 압축된 길이이며, A1 와 A2 는 각각 제1단차실의 내경의 면적과 제2단차실의 내경의 면적이다. 반면, 피스톤이 정지하도록 방향조절밸브가 폐쇄된 상태에서, 제1유로와 제2유로를 개통시키는 임계압력(P2)는,

로 정해진다.In a state in which the directional control valve is opened so as to move the piston, the critical pressure P1, which opens the first flow path and the second flow path,

. Here, 'K' is the spring constant of the relief spring, 'δ' is the compressed length of the relief spring, and A1 and A2 are respectively the area of the inner diameter of the first stepped seal and the inner diameter of the second stepped seal. On the other hand, in a state in which the direction control valve is closed so as to stop the piston, the critical pressure P2, which opens the first flow path and the second flow path,

Respectively.

The present invention having the above-described structure has an effect of suppressing a load generated in each component due to an excessive increase in hydraulic pressure occurring in the gear box of the power steering.

That is, the hydraulic pressure is prevented from rising excessively when the steering wheel is in the rotating state (when the piston is moving) and when the steering wheel is in the stopped state (when the piston is stopped).

The limiter is connected to the outside of the gear box, and can be applied to an existing gear box.

Hereinafter, a power steering system according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

1, the power steering apparatus of the present invention is provided with a gear box, a hydraulic pump 81 and an oil tank 82. The hydraulic pump 81 receives a high-pressure line 80 from the oil tank 82 And the working oil in the gear box is recovered to the oil tank 82 through the low-pressure line 90. [0034]

The gear box is provided with a chamber inside the housing 60. A piston 61 is mounted in the chamber and is partitioned into a left compartment 62a and a right compartment 62b on one side and the other side of the piston 61. [ The piston 61 is coupled with a sector shaft 63 connected to a load wheel (wheel) by a rack and pinion so that the sector shaft 63 is configured to rotate in accordance with the slide of the piston 61. The operating fluid supplied from the high-pressure line 80 for moving the piston 61 is connected to the left compartment 62a or the right compartment 62b via the direction control valve 70 and the directional control valve 70 To the low-pressure line (90).

When the piston 61 moves to the left, the directional control valve 70 connects the right compartment 62b to the high-pressure line 80 so that the hydraulic fluid is supplied to the right compartment 62b, and at the same time, The left compartment 62a is connected to the low-pressure line 90 so that the operating oil is recovered from the left compartment 62a. The directional control valve 70 is configured to allow the hydraulic fluid to flow only when the steering wheel (not shown) rotates, that is, when the piston 61 moves. Therefore, when the piston 61 is not moving, the hydraulic fluid supplied from the high-pressure line 80 is not introduced into the chamber but is recovered to the oil tank 82 through the low-pressure line 90. [ For reference, the direction control valve 70 is implemented by a conventional 5-port direction control valve capable of realizing the above-described functions.

The present invention includes a limiter (100) that lowers the hydraulic pressure in the high pressure line (80) when the hydraulic pressure in the high pressure line (80) exceeds the threshold pressure. The limiter 100 is connected to the low pressure line 90 and the high pressure line 80 and is also connected to either the left compartment 62a or the right compartment 62b and the direction control valve 70 in the chamber.

Referring to FIG. 2, the limiter 100 is constructed by mounting a relief plunger 20 and a flow rate check plunger 30 to a casing 10 having an oil chamber and a space therein.

The casing (10) has a relief mounting chamber (19) formed therein so that a relief plunger (20) having a tapered shape is formed so that its upper end gradually becomes smaller in diameter, A plunger mounting chamber 31 in which the flow rate check plunger 30 is slidably mounted at a predetermined distance from the seal 19 is formed. A first stepped chamber 18a is formed at an upper side of the relief mounting chamber 19 so as to narrow the inner diameter of the relief plunger 20 so as to close the inlet thereof. And a second stepped chamber 18b in which the lower end of the relief plunger 20 is fitted is formed to the lower side of the relief mounting chamber 19.

A first flow path 11 is formed in the casing 10 so that the first step chamber 18a is connected to the high pressure line and a second flow path 12 is formed so that the relief mounting chamber 19 is connected to the low pressure line. do. The first step chamber 18a is connected to the plunger mounting chamber 31 through the fifth flow path 15 and the relief mounting chamber 19 is connected to the plunger mounting chamber 31 through the sixth flow path 16. [ Lt; / RTI > The fifth flow path 15 and the sixth flow path 16 are spaced apart from each other by a predetermined distance so that they can be opened or closed depending on whether the flow rate check plunger 30 slides and meets the flow path groove 32 And is connected to the plunger mounting chamber 31 so as not to be connected to each other. A seventh flow path 17 is formed on the other side of the plunger mounting chamber 31 and the seventh flow path 17 connects the plunger mounting chamber 31 and the second step chamber 18b. A third flow path 13 is formed in the plunger mounting chamber 31 so as to be connected to the direction control valve. The plunger mounting chamber 31 is connected to either the left compartment or the right compartment in the chamber, Is formed at a predetermined distance from the third flow path 13. The third flow path 13 and the fourth flow path 14 are formed in a direction in which the flow rate check plunger 30 can be slid by the hydraulic pressure.

The relief spring 40 closes the first stepped chamber 18a by the elasticity of the relief spring 40 and the flow rate check plunger 30 is moved to the fifth flow path 15 by the elasticity of the plunger spring 50. [ And connects the sixth flow path 16 and the seventh flow path 17 with each other.

The thus configured limiter 100 operates as follows when the steering is performed (when the piston moves).

Referring to FIG. 3A, when the piston moves, the directional control valve connects either the left compartment or the right compartment to the high pressure line and the other to the low pressure line. Accordingly, the hydraulic oil having increased hydraulic pressure flows into the plunger mounting chamber 31 through the third flow path 13 and the fourth flow path 14, and the flow rate check plunger 30 is slid. The flow path groove 32 of the flow rate check plunger 30 opens the fifth flow path 15 and the seventh flow path 17 so that the hydraulic pressure in the first stepped chamber 18a and the second stepped chamber 18b Pressure line.

At this time, P1 * A1 (pressure acting on the upper end of the relief plunger) < P1 * A2 + K * delta (pressure acting on the lower end of the relief plunger) [P1 & 'Is the initial value of the relief spring moved by compression, and A1 and A2 are the initial values of the inner diameter of the first stepped chambers and the inner diameters of the inner diameters of the second stepped chambers, respectively, and' K 'is the spring constant of the relief spring, Of the area].

로 정해진다.However, when the value of P1 is increased, the value of P1 * A1 becomes larger than the value of P1 * A2 + K * delta at any moment (since the value of K * As shown in FIG. 3B, the critical pressure P1 for opening the high-pressure line and the low-pressure line when the piston is moving,

Respectively.

4A, when there is no flow of the hydraulic fluid in the chamber and no hydraulic pressure is generated in the direction control valve and the chamber, the fifth flow path 15 is closed by the flow check plunger 30, The six-flow path 16 and the seventh flow path 17 are opened.

P3 * A2 + K * delta (pressure acting on the lower end of the relief plunger) < RTI ID = 0.0 > 'P2' is the hydraulic pressure of the high pressure line, 'P3' is the hydraulic pressure of the low pressure line, 'K' is the spring constant of the relief spring, ' A2 are the areas of the inner diameters of the first step chambers and the inner diameters of the second step chambers, respectively].

로 정해진다. However, since the hydraulic pressure P3 of the low-pressure line is close to zero (zero), the critical pressure P2 at which the relief plunger 20 opens the high-pressure line and the low-pressure line as shown in FIG.

Respectively.

Therefore, when the steering is performed and of course there is no steering, it is possible to lower the hydraulic pressure of the high-pressure line by varying the critical pressure with each other. This lowered hydraulic pressure reduces the load on the ring cage mechanism and prevents the temperature of the operating oil from rising.

As described above, the embodiments disclosed in the present specification and drawings are only illustrative of specific examples in order to facilitate understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

1 is a sectional view schematically showing the overall configuration of a power steering apparatus according to a preferred embodiment of the present invention;

2 is a cross-sectional view of a limiter in accordance with a preferred embodiment of the present invention;

Figs. 3a and 3b are cross-sectional views respectively showing the state before and after the operation of the limiter when the piston moves,

Figures 4a and 4b are cross-sectional views, respectively, before and after actuation of the limiter when there is no movement of the piston.

DESCRIPTION OF REFERENCE NUMERALS

10: casing 20: relief plunger

30: Flow check plunger 40: Release spring

50: Plunger spring

Claims (4)

A hydraulic power steering apparatus in which a chamber inside a housing is partitioned by a piston into a left compartment and a right compartment and a piston moves by a hydraulic pressure difference in the left compartment and the right compartment, The hydraulic oil supplied to the chamber is supplied from a hydraulic pump through a high pressure line and is recovered through a low pressure line. The high pressure line and the low pressure line are connected to selectively supply hydraulic oil to the left compartment or the right compartment And a direction regulating valve for recovering, And a limiter that opens and closes the high-pressure line and the low-pressure line when the hydraulic pressure in the high-pressure line exceeds the threshold pressure, and one end of the limiter is connected to the low- A critical pressure is determined according to whether the piston is moved or not, Wherein the limiter includes a relief mounting chamber and a plunger mounting chamber in which a first stepped chamber is formed on the upper side and a second stepped chamber having a smaller inner diameter is formed on the lower side, A third flow path connecting the plunger mounting chamber to the direction control valve, a fourth flow path connecting the plunger mounting chamber to the chamber, and a third flow path connecting the plunger mounting chamber to the chamber, A fifth flow path connecting the first stepped chamber and the plunger mounting chamber, a sixth flow path connecting the relief mounting chamber to the plunger mounting chamber and a seventh flow path connecting the second stepped chamber to the plunger mounting chamber, A relief plunger having an upper end tapered to close the inlet of the first stepped seal and the plunger mounting chamber and a lower end to be seated in the relief mounting chamber to slide in the second stepped chamber, A flow check plunger that opens and closes the third and fourth flow paths, and a flow check plunger that opens and closes the third flow path and the fourth flow path, the other side being formed with a flow path groove along the outer peripheral surface to connect the seventh flow path with the fifth flow path or the sixth flow path. And a relief spring to which the relief plunger is mounted to close the first step chambers; And a plunger spring mounted to the flow check plunger to close the third and fourth flow paths and to open the sixth and seventh flow paths. delete 2. The apparatus as claimed in claim 1, wherein the critical pressure (P1) for opening the first flow path and the second flow path, in a state in which the direction control valve is opened so as to move the piston,

(K: spring constant of the relief spring, delta: initial movement value of the relief spring, A1: area of the first stepped inner diameter, A2: area of the second stepped inner diameter) 2. The apparatus according to claim 1, wherein, in a state in which the direction control valve is closed so as to stop the piston, the critical pressure P2, which opens the first flow path and the second flow path,

(K: spring constant of the relief spring, delta: initial movement value of the relief spring, A1: area of the first stepped inner diameter, A2: area of the inner diameter of the second stepped thread, )

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