JPS60185672A - Power steering device - Google Patents

Abstract

PURPOSE:To aim at stabilization in a feeling of steering operation to be given to a driver in time of running at high speed, by making initial setting operation reaction at a time when a control valve starts its actuation so as to be larger in time of high speed than that in time of low speed. CONSTITUTION:When a driver operates a steering wheel and thereby a pinion 22 engages a rack, steering resistance out of the steering wheel is transmitted to the pinion 22, and the pinion 22 moves in a right direction of an axis of a valve 23, by way of example, whereby a lever 24 rocks in the right direction with a supporting pin part 24b as a fulcrum. Simultaneously the driving lever 24 rocks, a pin part 24a also rocks, driving a spool valve 23 in the right direction. Like this, for having the spool valve 23 driven, it is necessary to input such large torque as being more than the specified value into the steering wheel, and this torque, serving as initial setting operation reaction, gives a feeling of accurate steering operation to the driver.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a power steering device, and more particularly, to a power steering device that generates a steering assist force when steering the steering wheel of a vehicle to reduce the force required to operate the steering wheel by the driver. The present invention relates to a power steering device.

(Prior Art) Conventionally, there is a power steering device as shown in FIG.
(See No. 855). This power steering device includes a flow control valve 3 interposed between a pump 1 and a control valve 2, and a bypass that discharges pressure oil directly from the flow control valve 3 to a reservoir tank 4 without passing through the control valve 2. A passage 5 is provided, and as the vehicle speed increases, the amount of pressure oil bypassed to the reservoir tank 4 increases and the net flow rate of pressure oil sent to the control valve 2 decreases, as shown in FIG. There is ζ. Reference numeral 7 denotes a steering mechanism incorporating a power cylinder controlled by a control valve 2. Furthermore, a conventional control valve 2 used in such a power steering device is disclosed in Japanese Patent Application Laid-Open No. 57-167869. This control valve 2 uses a centering spring, which keeps the spool valve in a neutral position and is compressed when operating the steering wheel to generate an operation reaction force, giving the driver a reliable feeling of pawl operation. It gives As shown in Fig. 3, the hydraulic characteristics of the power cylinder in such a power steering device are represented by a solid line graph passing through points A, B, and C at low speeds, and -ζ is expressed by A at high speeds. , , B', and a broken line passing through each point of B'. As can be seen from this graph, in this power steering system, the operation force of the steering wheel is increased by increasing the force of G as the vehicle speed increases, in order to improve running stability at high speeds.

However, in such conventional power steering devices, the hydraulic characteristics of the power cylinder are limited only in the region where the steering wheel is operated with a torque greater than the torque TA at point A, as shown in Figure 3. It cannot be changed. Torukiya is control valve 2
This is because it is fixed only by the preload of the centering spring 34. On the other hand, it is desirable that the 1-lux T^ at point A of the hydraulic characteristics be made larger at high speeds than at low speeds in order to stabilize the feeling of water removal given to the driver. Therefore, in the conventional power steering device in which I'A at point A of the hydraulic characteristic is constant, the torque T, 4 is made larger at high speeds than at low speeds to stabilize the sense of operation of the rake claw to the driver. The disadvantage was that it was not possible to

(Purpose of the Invention) Therefore, the present invention aims to improve the initial reaction force of the steering wheel when the control knob/rub starts operating (when the power cylinder starts generating steering assist force) at high altitudes than at low speeds. The purpose is to stabilize the sense of operation of the swivel claws given to the driver when driving at high speeds by increasing the odor °C.

(Structure of the Invention) A power steering link arrangement 1 according to the invention includes a steering mechanism that transmits the operation of a steering wheel to a steering shaft;
A pump that pressurizes the hydraulic fluid sucked in from the reservoir tank and sends out the pressure fluid, and a pump that is connected to the above-mentioned rudder mechanism to provide steering control to the steering mechanism. a power cylinder that applies 11τ assistance; a 2-roll valve that opens and closes the pump and the power cylinder that communicates the pump and the power cylinder with a response to steering resistance from the steering shaft; and a flow control valve that is interposed between the control valve and the control valve and changes the flow rate of the pressure fluid sent to the control valve depending on the vehicle speed;
a bypass path for directly discharging the flow rate change of the pressure fluid due to the flow rate control valve to the reservoir tank, and an orifice is provided in the bypass path, and the orifice communicates with the bypass path between the flow rate control valve. A reaction force chamber for generating a reaction force for operating the steering wheel is provided in the control valve.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 4 is a diagram showing a power steering device according to an embodiment of the present invention.

First, to explain the configuration, in FIG. 4, 11 is a pump that pressurizes incompressible oil (hydraulic fluid) taken in from the reservoir tank 14 and sends out pressure oil (pressure fluid), and 12 is a pump that pumps out pressure oil (pressure fluid). This is a control valve that opens and closes an oil passage communicating between the pump 11 and a power cylinder (not shown) connected to a steering mechanism that steers steering wheels (not shown) in response to steering resistance from the opposite shaft. A flow control valve 13 is interposed between the pump 11 and the control valve 12, and this flow control valve I3 changes the flow rate of pressure oil sent from the pump 11 to the control valve 12 in accordance with the vehicle speed.已、
As shown in FIG. 2, as the vehicle speed increases, the net flow rate of pressure oil to the control valve 12 is reduced. A bypass passage 15 is connected to the flow rate control valve 13, and the flow rate control valve 13 is connected to this bypass passage 15.
A change in the flow rate of pressure oil to the control valve 12 is directly outputted to the reservoir tank 14 by υ1.

An orifice 18 is provided in the middle of the bypass path 15, and two reaction chambers 19 and 20 in which the control valve 12 exists communicate with each other in the middle of the bypass path I5 between the orifice 18 and the flow rate control valve 13. are doing. The control valve 12 includes a spool valve 23 that is slidably housed in a spool housing 21.
3, the support pin portion 24 is connected to the pinion 22 through the engagement of the rank (not shown) and the pinion 22 by operating the steering wheel (not shown).
The drive pin portion 24a of the drive lever 24, which swings in the axial direction of the spool valve 23 with b as a fulcrum, is engaged (,z).

A centering spring 17 is interposed between the spool housing 21 and the spool valve 23 coaxially with the spool valve 23, and biases the spool valve 23 to maintain it at a neutral position in the axial direction. Reaction force chambers 19 and 20 are provided at both ends of the spool housing 21 coaxially with the spool valve 23, and as described above, these reaction force chambers 19 and 20 communicate with the bypass passage 15 midway. ing. The reaction force chambers 19 and 20 on the spool valve 23 side are closed by reaction force pistons 25 and 26, respectively, and these reaction force pistons 25 and 26 are closed by step portions 21a and 21b formed in the spool housing 21. Movement to the 23 side is restricted. Small-diameter protrusions 23a and 23b are formed at both ends of the spool valve 230, and when the spool valve 23 is in the neutral position, the tips of the first protrusion 23a and the protrusion 23b are connected to the stepped portion 21a of the spool housing 21. The stepped portion 21 b 4 is in slight contact (without any exchange of pressure) with the anti-moldstones 25 and 26 which are stopped in contact with each other.

Next, the effect will be explained. When the driver rotates the steering wheel (not shown) and the pinion 22 engages with the rank (not shown), steering resistance from the steering wheel (not shown) is transmitted to the pinion 22 via the rank, and the pinion 22 is connected to the spool, for example. By moving the valve 23 to the right on the axis, the drive lever 24 swings to the right about the support pin portion 24b as a fulcrum. As the drive lever ~24 moves IJ, the drive pin part 24a also swings, and the drive pin part 24a4J:
The spool valves 2 and 3 are driven to the right against the (=J force of the centering spring 17 and the pressure of the force chamber 20. In this way, the spool valve 23 acts against the force of the centering spring 17 and the pressure of the force chamber 20. In order for the steering wheel (not shown) to be driven against the pressure of The predetermined input torque of the steering wheel when starting (
(referred to as the initial setting repetition reaction force), it is possible to give the driver a reliable feel of the steering operation. As described above, when the spool valve 23 moves, for example, to the right, an oil passage communicating between the pump 11 and the power cylinder (not shown) is opened, and the power cylinder applies a steering assist force to the steering mechanism (not shown). When the vehicle speed increases, the flow control valve 1
3, the flow rate of the pressure oil sent to the control valve 12 decreases (Fig. 2), and the steering assist force from the power cylinder also decreases, so it is necessary to increase the torque applied manually to the steering wheel. The operating force becomes heavier, which can improve driving stability. Furthermore, as the vehicle speed increases, the flow rate of pressure oil discharged from the flow rate i1i control valve 13 to the reservoir tank 4 through the bypass path 15 also increases. and the flow control valve 13.
The pressure of the pressure oil in 5 increases as shown in FIG. This increased pressure is also applied to the reaction force chambers 19 and 20 of the control valve 12, so the higher the speed, the greater the force required to move the spool valve 23, causing the control valve 12 to start operating. The initial setting reaction force of the steering wheel when doing so requires a large value. In other words, such initial setting operation reaction force is the one at low speed (as shown in Fig. 6).
The value (TAa) at high speed changes to be larger than that at high speed (rA, ).This makes it possible to stabilize the steering feel given to the driver when driving at high speed.

In the embodiment, a rack-and-pinion type power steering device has been described, but there is no need to be limited to this type.

Further, in the embodiment, a spool valve type power steering device has been described, but other types (for example, a low re-valve type) may be used as long as the principles of the present invention can be applied.

(Effects of the Invention) As explained above, according to the present invention, the initially set steering reaction force of the steering wheel when the control valve starts operating is made larger at high speeds than at low speeds. It is possible to stabilize the steering operation feeling given to the driver when driving at high speed. Additionally, the fact that the spool valve does not move until it overcomes the pressure in the reaction force chamber has the effect that the apparent stiffness of the steering increases as the vehicle travels at higher speeds, making the steering characteristics more favorable.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram showing a conventional power steering device, and Fig. 2 is a bypass i'Jrt amount of pressure fluid to the reservoir tank by the flow control valve shown in Fig. 1 (diagonal line OB
) and the net flow rate of pressure fluid to the control valve (
3 is a graph showing the hydraulic characteristics of the power steering device shown in FIG.
The solid line passing through each point of , C is the one at low speed, A, B',
The broken line passing through each point of C' is the one at high speed. Fig. 4 is an overall schematic diagram showing a power steering device according to an embodiment of the present invention, and Fig. 5 shows vehicle speed and reaction force chamber 19.20.
Figure 6 is a graph showing the relationship between the pressure and the hydraulic pressure of the power steering system shown in Figure 4. The dashed line passing through each point of 8'', B //, C // is 1r
This is at G speed. 11----Pump, +2--Control valve, 13--First volume control valve, 14--Reservoir tank, +5--Bypass path, +8--Orifice, 19.20 -----One reaction force chamber. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Agagun Part

Claims (1)

[Claims] A steering mechanism that transmits the operation of the steering wheel to the steering wheels, a pump that pressurizes hydraulic fluid sucked from a reservoir tank and sends out the pressure fluid, and a power cylinder that is connected to the steering mechanism and provides steering assist force to the steering mechanism. a control valve that opens and closes a wave path that communicates the pump and the power cylinder in response to steering resistance from the steering wheels; a flow rate control valve that changes the flow rate of the pressure liquid sent to the tank, and a bypass path that discharges the flow rate change of the pressure liquid caused by the flow rate control valve directly to a reservoir tank, and an orifice is provided in the bypass path, A power steering device characterized in that the control valve is provided with a reaction force chamber that communicates with a bypass path between the orifice and the flow rate control valve and generates a reaction force for operating the steering wheel.