JPS6212072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that increases or decreases steering force depending on the driving situation of a vehicle.

The steering resistance of the vehicle decreases as the vehicle speed increases. Therefore, the required flow rate of pressure oil to be supplied to the power steering actuator decreases proportionally as the speed increases. In order to meet such demands, the present applicant filed a patent application No. 52-120192.
Speed-sensitive power steering devices have been proposed, such as No. 52-126209.

Now, to explain this based on Figure 1,
The flow rate control unit 1 sends hydraulic oil (pressure fluid) from a hydraulic pump driven in synchronization with a vehicle engine to an actuator 3b such as a power cylinder via a control valve 3a of a power steering unit 2.
A portion of it is bypassed and returned to the tank.

In the flow rate control unit 1, a control spool 5 is slidably housed in a cylindrical valve hole 4, and the control spool 5 divides the valve hole 4 into a front pressure chamber 6 and a back pressure chamber 7. There is.

An inlet port 8 that connects to the discharge side of the hydraulic pump and a bypass port 9 that returns part of the discharged oil to the tank are opened in the valve hole 4, and communication between these inlet ports 8 and bypass port 9 is controlled by a control spool. 5 opens and closes, while an outlet port 10 communicating with the control valve 3a opens into the valve hole 4.

A partition wall 11 is provided in the valve hole 4 between the inlet port 8 and the outlet port 10,
Both ports 8 and 10 communicate with each other through a through hole 12 formed in the center of this partition wall, and this through hole 1
A tapered metering rod 13 is inserted into 2, thereby forming a variable orifice O between the two to regulate the flow rate delivered to the actuator 3b via the outlet port 10. The base end of the metering rod 13 penetrates the side wall of the main body and protrudes outward, and the metering rod 13 has a minimum diameter section 16a at the distal end and a maximum diameter section 16b at the base end, and has a tapered section between them. 16c is formed while
The spring 19 causes the rod 13 to move to the smallest diameter portion 16.
energized so that a is located in the through hole 12.

A chamber 20 partitioned by a partition wall 11 and downstream of the variable orifice O communicates with the above-mentioned afterpressure chamber 7 through a passage 21, thereby controlling the front pressure of the orifice throttle acting on the left end of the control spool 5. In response, the after pressure of the orifice throttle is applied to the right end of the control spool 5.

Further, a spring 22 interposed between the right end of the control spool 5 and the side wall acts, so that
The control spool 5 moves to a position where the pressure before orifice throttling in the front pressure chamber 6 is balanced with the resultant force of the after throttling pressure in the rear pressure chamber 7 and the elastic force of the spring 22.

Then, the running speed of the vehicle is electrically adjusted so that the metering rod 13 is moved forward and backward with respect to the through hole 12 in accordance with the vehicle speed, and the opening degree of the variable orifice O is adjusted in accordance with the steering resistance that is proportional to the running speed. A vehicle speed detecting section 25 is provided to detect the vehicle speed, and the metering rod 13 is operated proportionally based on the output of the vehicle speed detecting section 25.

A drive circuit 3 to which the output of the vehicle speed detection section 25 is supplied
2 controls the supply current to a solenoid 34 arranged around a movable iron core integral with the measuring rod 13 in order to drive the measuring rod 13 in accordance with the detected vehicle speed. As a result of the above, the hydraulic pump is now driven in synchronization with the engine rotation, and its discharge flow rate increases as the rotation speed increases. This pressure oil is sent through the inlet port 8, prepressure chamber 6, through hole 12 (variable orifice O), chamber 20, and outlet port 10 to the control valve 3a and actuator 3b.

The flow rate is determined based on the opening degree of the variable orifice O and the differential pressure across it. At this time, the front pressure of the orifice throttle acts on the left end of the control spool 5, and the rear pressure also acts on the left end of the control spool 5. It is led to the afterpressure chamber 7 via the rear pressure chamber 7 and acts on the right end of the control spool 5.

Therefore, the control spool 5 moves to the right until these pressure differences and the pressing force of the spring 22 are balanced.

When the pump discharge amount increases above a certain level and the differential pressure across the orifice reaches a predetermined value, the bypass port 9 is activated based on the rightward movement of the control spool 5.
opens, and a portion of the flow is bypassed to the tank so as to keep the differential pressure above constant.

Therefore, if the opening area of the variable orifice O determined by the position of the metering rod 13 with respect to the through hole 12 is constant, and if the pump discharge rate increases in this state, the differential pressure will increase and the control spool 5 will move to the right. Along with this, the opening degree of the bypass port 9 increases, and in the end, the excess flow is transferred to the bypass port 9 so as to keep the flow rate supplied to the power steering section 2 almost constant.
Let it escape to the side. When the vehicle is stopped, the opening area of the variable orifice O is maximized, and this flow rate is set in advance so that sufficient steering output can be obtained even when the vehicle is stationary. Next, when the vehicle is running, the output value of the speed signal detected by the vehicle speed detection unit 25 increases as the vehicle speed increases, so the current supplied to the solenoid 34 via the drive circuit 32 also increases. ,
It will increase accordingly. As a result, the metering rod 13 constituting the variable orifice O moves to the right while compressing the spring 19 according to the vehicle speed, so that as the vehicle speed increases, the opening area of the variable orifice O decreases.

At this time, the control spool 5 operates so that the differential pressure across the orifice is kept constant, so the flow rate passing through the orifice is controlled in proportion to the opening area. In other words, as the vehicle speed increases, the flow rate is controlled to be supplied to the power steering section 2. The flow rate decreases. As the vehicle speed increases, the steering resistance decreases, so the required flow rate also decreases accordingly.In this way, the metering rod 13 responds to the vehicle speed to always supply an appropriate flow rate to the power steering section 2. .

In this way, the flow rate is controlled according to the vehicle speed,
To always give a driver appropriate steering force (sensation). However, the steering resistance that the wheels receive varies depending on various other conditions.

For example, if the load of a vehicle such as a truck increases due to the state of cargo, the steering resistance increases accordingly, and if the tire pressure decreases, the resistance also relatively increases.

Therefore, even if only the vehicle speed is taken as a control signal, an appropriate steering output may not necessarily be obtained.

Therefore, if the flow rate of the working fluid is controlled by detecting the vehicle load, tire pressure, etc., which are variable factors in steering resistance, it is possible to achieve output control corresponding to the steering resistance. Providing a means to detect this will lead to an increase in manufacturing costs and the complexity of the control system.

By the way, the pressure oil supplied to the power steering device is discharge oil of a hydraulic pump driven in synchronization with engine rotation, and as the load on the power steering section 2 increases, the pump discharge pressure increases accordingly. is also on the rise.

As a result, by detecting the pump discharge pressure, that is, the circuit supply pressure, it is possible to determine the steering resistance that is a load on the power steering section 2, and therefore, the flow rate is increased in response to the increase in the circuit supply pressure. Then, the output can be increased according to the steering resistance.

The present invention has focused on this point, and by giving the pressure-receiving parts of the control spool a difference in area and making it possible to control the flow rate in response to the circuit supply pressure, it is possible to accurately control the steering resistance with an extremely simple configuration. An object of the present invention is to provide a power steering device that can obtain a corresponding steering output.

Embodiments of the present invention will be described below based on FIG.

In the present invention, the pressure receiving portion 7a of the control spool 5' on the rear pressure chamber 7 side is configured to have a larger diameter than the pressure receiving portion 6a on the front pressure chamber 6 side, thereby providing a difference in pressure receiving area at both ends of the spool.

Therefore, the valve hole 4' is formed in a step hole between the small diameter part 4a and the large diameter part 4b, and the pressure receiving part 7a is formed in the large diameter part 4b.
Position it so that it can slide freely.

Since the other configurations are the same as those in FIG. 1, a detailed explanation will be omitted, but the same parts will be denoted by the same reference numerals.

The control spool 5' moves according to the balance between the hydraulic pressure acting on its front and rear ends and the elastic force of the spring 22. After-pressure of the throttle acts on .

The control spool 5' is displaced while adjusting the opening degree of the bypass port 9 that controls the return flow rate until these acting forces are balanced, thereby controlling the differential pressure across the orifice O.

At this time, if the load on the power steering section 2, which varies depending on the steering resistance, is the same, the above-mentioned differential pressure is basically controlled to a constant value, and the position of the metering rod 13 that controls the opening area of the orifice O is adjusted. The steering output is controlled by increasing/decreasing the flow rate in proportion to the vehicle speed, and in this way, an appropriate steering output can be obtained depending on the vehicle speed.

On the other hand, the pressure after the orifice throttle is proportional to the load acting on the power steering section 2, that is, the steering resistance, and the pressure increases as the steering resistance increases.

Now, if we consider the dynamic balance of the control spool 5', P ₁ S ₁ = P ₂ S ₂ + F …………(1) where, P ₁ : Before pressure of throttle, P ₂ : After throttle Pressure S ₁ : Area of pressure receiving part 6a, S ₂ : Area of pressure receiving part 7a F: Spring acting force From equation (1), P ₁ - P ₂ = 1/S ₁ {(S ₂ - S ₁ ) P ₂ + F}... ......(2
) Therefore, from this equation (2), it can be seen that the differential pressure across the orifice (P ₁ −P ₂ ) is proportional to the rear pressure P ₂ of the throttle and the spring acting force F.

Here, in the case of the conventional example where S ₁ =S ₂ , P ₁ -P ₂ =F/S ₁ (3), and the differential pressure across the orifice depends only on the spring acting force.

As a result, the differential pressure (P ₁ − P ₂ ) increases as the pressure after the throttle P ₂ increases relatively, so even if the orifice area is constant at this time, the flow rate is proportional to the differential pressure. As a result, the steering output increases or decreases depending on the steering resistance.

That is, according to the present invention, it is possible to control the supply amount of hydraulic oil in response to changes in steering resistance without having to specifically detect vehicle weight, tire pressure, etc., which are functions of steering resistance. Based on this, it becomes possible to appropriately increase or decrease the steering output.

As described above, according to the present invention, although it has an extremely simple configuration, it is possible to appropriately control the steering output in response to steering resistance, and it has the effect of always providing an accurate steering feel. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a sectional view showing essential parts of the present invention. 1...Flow control section, 2...Power steering section, 5'...
... Control spool, 6... Front pressure chamber, 6a... Front pressure side pressure receiving part, 7... Back pressure chamber, 7a... Back pressure side pressure receiving part,
12...Through hole, 13...Measuring rod, 25...Vehicle speed detection section, 34...Solenoid.

Claims (1)

[Claims] 1. A flow control unit installed in a flow path that guides pump discharge oil to a power steering unit, a variable orifice formed by freely inserting the flow control unit into a through hole provided in the flow path, and a variable orifice that responds to the differential pressure between the front and rear of this orifice. It consists of a control spool that bypasses a portion of the discharged oil, a vehicle speed detection section that electrically detects the vehicle speed, and a solenoid that controls the position of the metering rod according to this detection signal. In the power steering device, the opening degree of the orifice is reduced according to the increase in rear pressure by forming an area difference in a pressure receiving part of the orifice front and rear differential pressure of the control spool, and increasing the steering output according to the increase in rear pressure. Power steering device.