JP2608423B2 - Speed-sensitive power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) This invention increases the reaction force of the handle at high speeds,
The present invention relates to a speed-sensitive power steering device that reduces the reaction force at low speed.

(Prior Art) In the conventional power steering shown in FIGS. 4 to 6,
By switching the handle H, the pinion shaft 1 is swung right and left. The swing of the pinion shaft 1 causes the lever 2 to swing about the fulcrum o, and the swing of the lever 2 switches the spool 4 of the steering control valve 3. By switching the spool 4 in this manner, the pressure oil supplied from the pump P is guided to one of the chambers of the power cylinder 5 and the other chamber is communicated with the tank T.

The piston rod 5a of the power cylinder 5 is linked to the wheel 6 via a knuckle arm, and the turning angle of the power cylinder 5 is controlled in accordance with the operation amount of the power cylinder 5.

Then, both ends of the spool 4 face the reaction force chambers 7 and 8, and the reaction force chambers 7 and 8 communicate with each other through a communication passage 9. Furthermore, this communication passage 9 is a port
10 and control port 13 of reaction pressure control valve 12 through passage 11
Is in communication with

The reaction pressure control valve 12 has an inflow port 15 and a tank port 16 in addition to the control port 13 in the main body 14, and a spool hole 17 in the axial direction thereof. The ports 15, 16 on the spool hole 17 side
First and second annular concave grooves 18 and 19 are formed in the opening.

The inflow port 15 communicates via a passage 20 with a supply passage 21 which communicates the pump P with the steering control valve 3, and the tank port 16 communicates with a tank T via a return passage 22.
Is in communication with

Spool 23 slidably housed in spool hole 17
Has one end facing the spring chamber 24. The other end of the spool 23 is connected to the push rod of the solenoid 26 by the action of the spring 25 provided in the spring chamber 24.
27 contact.

An annular groove 28 is provided around the spool 23 in this manner.
However, the annular groove 28 always communicates with the control port 13 regardless of the moving position of the spool 23.

The solenoid 26 of the reaction pressure control valve 12 is electrically connected to the controller C. The controller C controls the exciting current to the solenoid 26 according to the vehicle speed of the vehicle speed sensor 29.

When the vehicle is stopped, the exciting current increases and the push rod 27
6, the annular groove 28 and the first
The annular groove 18 keeps the overlap lp and cuts off the communication with each other. At this time, the second annular concave groove 19 and the annular groove 28 communicate with each other while maintaining the underlap lr at the maximum.

From this state, the vehicle speed gradually increases, the exciting current to the solenoid 26 decreases, and when the spring force of the spring 25 overcomes the pressing force of the push rod 27, the spool 23 moves with the spring force of the spring 25. .

Now, when the handle H is turned in a predetermined direction to switch the spool 4 of the steering control valve 3, the discharge oil of the pump P flows from the supply passage 21 via the steering control valve 32 to one of the power cylinders S. And the other chamber of the power cylinder S
Communicate with

Part of the discharge oil supplied to the pump P in this way flows into the inflow port 15 via the passage 20.

At this time, if the vehicle is stopped, the upstream variable throttle lp maintains the fully closed state, and the pressure oil is cut at the variable throttle lp. Moreover, in this case, the variable throttle lr on the downstream side maintains the fully open state, so that the reaction force chambers 7, 8 are maintained at the tank pressure. In other words, if the steering wheel H is turned while the vehicle is stopped, the reaction force against the steering wheel is minimized, and the entire amount of oil discharged from the pump P is supplied to the power cylinder S.

As the vehicle speed increases, the upstream variable throttle
As the opening area of lp increases, the variable throttle on the downstream side
The opening area of lr becomes smaller. Therefore, part of the pressure oil supplied to the power cylinder S is transferred from the passage 20 to the inflow port 15.
→ The first annular concave groove 18 → flows into the reaction force chambers 7 and 8 of the steering control valve 3 via the annular groove 28, and a part of the oil flows into the tank T via the downstream variable throttle lr. Will be returned. When the pressure oil passes through the variable throttle lr in this manner, a differential pressure is generated before and after that, and this differential pressure acts on the reaction force chambers 7 and 8, thereby generating a reaction force of the handle.

(Problems to be Solved by the Present Invention) The conventional device as described above uses the vehicle speed sensor 29, the controller C and the reaction force pressure control valve 12 which is electromagnetically controlled, so that the entire system is expensive. There was a problem of becoming.

An object of the present invention is to provide a power steering device of a vehicle speed sensitive type without using an electric device as in the related art.

(Means for Solving the Problems) The present invention is based on a speed-sensitive power steering device in which both ends of a spool of a steering control valve face a reaction force chamber, and the reaction force chamber communicates with a reaction force pressure control valve. It is to be.

In addition, while assuming the above-described device, the present invention connects a flow control valve that reduces the flow rate in proportion to the vehicle speed to the discharge side of a pump that is linked to the engine and that changes the discharge amount according to the vehicle speed. At the same time, a throttle is provided on the downstream side of the flow control valve, the upstream side of the throttle is connected to one pilot chamber of the reaction pressure control valve, and the downstream side is connected to the other pilot chamber. The reaction force pressure control valve has a port communicating with the reaction force chamber of the steering control valve and a tank port connected to the tank, and is configured to guide fluid from a pressure source to the reaction force chamber of the steering control valve. When the differential pressure before and after the throttling is large, the opening of the flow path connecting the port and the tank port is maximized to reduce the pressure in the reaction chamber, and as the differential pressure decreases, the ports are connected. Let go Having said opening by reducing in that the arrangement to increase the pressure in the reaction chamber.

(Operation of the Present Invention) Since the present invention is configured as described above, the flow rate supplied to the throttle decreases as the vehicle speed increases.
Therefore, the differential pressure before and after the throttling increases as the vehicle speed decreases, and conversely, as the vehicle speed increases, the differential pressure decreases.

Since the differential pressure before and after the throttle acts on both pilot chambers of the reaction pressure control valve, the larger the differential pressure, the more the flow connecting the outflow / inflow port and the tank port of the reaction pressure control valve. The degree of opening of the road increases. Therefore, when the vehicle is traveling at low speed, the pressure in the reaction force chamber is released to the tank, so that the reaction force of the handle is reduced and the operation of the handle is reduced.

On the other hand, if the differential pressure before and after the throttle is small, the degree of opening of the flow path connecting the inflow / outflow port and the tank port becomes small, so that the pressure of the pressure source is supplied to the reaction chamber. Therefore, when the vehicle is running at a high speed, pressure is supplied to the reaction force chamber, so that the reaction force of the handle becomes large, and the operation of the handle becomes heavy.

(Effects of the Present Invention) According to the device of the present invention, since the vehicle speed sensitive type can be realized only by the fluidic device, the whole system is inexpensive.

(Example of the present invention) the first embodiment shown in the first and second figures in conjunction with the engine, but connects the flow control valve V _F on the discharge side of the pump-dependent discharge rate of the vehicle speed, specific configuration of the flow control valve V _F are shown in Figure 2.

That is, a flow control spool 33 is slidably inserted into a valve hole 31 formed in the valve main body 30 with a spring 32 interposed between the flow control spool 33 and the inner end thereof.

Further, a hollow connector 34 is inserted outside the flow control spool, and the screw portion 35 is tightened to press the flange 36 against the side surface of the valve body 30.

The connector 34 as described above has a small-diameter portion 37 at the distal end, and an annular space 38 between the small-diameter portion 37 and the valve hole 31.
And plug the tip of this connector 34
Closed at 39. The plug 39 has a fixed orifice communicating the space 38 and the hollow portion of the connector 33.
Form 40.

A hollow plunger 41 is attached to the connector 34 as described above.
Is slidably inserted, but a spring 42 is interposed between the plunger 41 and the plug 39 so that the plunger 41 normally keeps the illustrated position.

The small diameter portion 37 of the connector 34 has a variable orifice 43
The variable orifice 43 is fully opened when the plunger 41 is at the normal position shown in the drawing, and when the plunger 41 moves against the spring 42, the opening area of the variable orifice 43 is reduced. .

Further, on the outer periphery of the plunger 41, a pressure chamber 44 formed in combination with the connector 34 is provided.
The space 38 communicates with the space 38 through the through hole 45.

Reference numeral 46 in the figure denotes an inflow port for guiding the discharge oil of the pump P to the space 38, and 47 denotes an outflow port formed in the connector 34.

The flow control spool 33 includes first and second land portions 48 and 49.
Along with the action of the spring 32, usually
It is in pressure contact with the plug 39. When the flow control spool 33 presses the plug 39 as described above, the bypass passage 50 and the space 38
Communication with is interrupted.

In the above state, when the pressure in the space 38 rises and the acting force overcomes the spring force of the spring 32, the flow control spool 33 moves to connect the space 38 and the bypass passage 50.

Outlet port 47 of the flow control valve V _F which is as described above,
The passage 51 communicates with the port 10 of the steering control valve 3 in the same manner as in the prior art.
52 are formed.

Since the configuration of the steering control valve 3 is completely the same as that of the conventional steering control valve, the details thereof are omitted, and each component is described with the same reference numeral.

The reaction force pressure control valve V connected to the passage 51
_O has a spool 54 slidably mounted in the valve body 53 and both ends of the spool 54 are connected to the pilot chambers 55 and 56.
It is facing.

Squeeze one of the pilot rooms 55
52, and connect the other pilot chamber 56 to the throttle
The other pilot chamber 56 is provided with a spring 57 while being connected to the downstream side of 52.

In the valve body 53 as described above, a pressure port 58 connected to the passage 51 on the downstream side of the throttle 52, an inflow / outflow port 59 connected to the reaction force chambers 7 and 8 of the steering control valve 3, and a tank T An annular groove is formed inside the pressure port 58 and the tank port 60 while forming the communicating tank port 60.
61 and 62 are formed.

The spool 54 also has an annular recess 63 formed thereon, and on both sides of the annular recess 63, shallow annular steps 64 and 65 are formed. The annular grooves 61 and 62 together form a variable orifice.

When the spool 54 is at the normal position by the action of the spring 57, the pressure port 58 and the inflow / outflow port 59 communicate with each other in a fully opened state, while the communication between the inflow / outflow port 59 and the tank port 60 is cut off.

Thus, during traveling of the vehicle, but the pump P is discharged to the pressure fluid operated, the pressure fluid flows to the steering control valve V _F of the inlet port 46.

The pressure oil that has flowed into the inflow port 46 flows out of the outflow port 47 via the fixed orifice 50 and the variable orifice 43.

At this time, if the vehicle is running at a low speed, the pump P
, The pressure difference between the fixed orifice 40 and the variable orifice 43 in the fully opened state hardly occurs.

Therefore, the pressure in the pressure chamber 44 is also maintained relatively low, so that the plunger 41 holds the illustrated normal position,
The variable orifice 43 is kept fully open. Therefore, almost all of the flow rate flowing from the inflow port 46 flows out of the outflow port 47.

When the vehicle speed increases from the above state, the discharge amount of the pump P increases accordingly, so that the differential pressure across the fixed orifice 40 and the variable orifice 43 increases. If the pressure difference increases, the pressure in the pressure chamber 44 becomes relatively high, so that the plunger 41 moves against the spring 42, but in the middle speed range, the opening of the variable orifice 43 is narrowed, In the range, the variable orifice 43 is fully closed.

As described above, if the variable orifice 43 is closed or its opening area becomes smaller, the outflow port 47 becomes smaller.
The amount of effluent from the tank is also reduced.

And, as described above, if the differential pressure across the orifice increases, the pressure acting on the flow control spool 33 also increases, so that the spool 33 moves against the spring 32,
The space 38 communicates with the bypass passage 50. Therefore,
The surplus flow rate flowing from the inflow port 46 is returned from the bypass passage 50 to the tank T.

In other words, the pump P itself is, the more the traveling speed of the vehicle if increased, but increase its discharge amount, the flow control valve V _F, the more the traveling speed if raised, outflow from the outlet port 47 Is to reduce.

When the vehicle travels at low speed, the amount of outflow from the outflow port 47 increases, and the flow rate passing through the throttle 52 increases accordingly. In this way, the greater the flow rate that passes through the throttle 52, the greater the differential pressure across the throttle 52, but the differential pressure at that time is reduced by the pilot chambers 55, 5 in the reaction force control valve V _O.
A pressure difference of 6.

Therefore, when the differential pressure across the restrictor 52 becomes large enough to overcome the spring force of the spring 57, the spool 54 moves against the spring 57 and switches from the normal position to the position shown. When the spool 54 is switched in this way, the communication between the pressure port 58 and the inflow / outflow port 59 is cut off, and the inflow / outflow port 59 and the tank port 60 communicate with each other in a fully opened state.

Therefore, the reaction chambers 7, 8 of the steering control valve 3 are:
Outflow / inlet port 59 → annular recess 63 → annular groove 62 → tank port
Since it communicates with the tank T via 60, no pressure is generated in the reaction force chambers 7, 8.

Therefore, even if the handle H is operated, the reaction force does not act, and the handle operation force is correspondingly reduced.

When the vehicle speed from the state rises, since the plunger 41 of the flow control valve V _F as gradually close the variable orifice 43 to move, outflow from the outflow port 47 is reduced Go. When the flow rate decreases in this manner, the differential pressure across the throttle 52 also decreases, so that the reaction force pressure control valve V _O
The pressure difference between the two pilot chambers 55 and 56 also becomes smaller.

Therefore, the spool 54 is connected to the pressure difference and the spring
It moves to a position where the spring force of 57 is balanced, but according to the vehicle speed at this time, in other words, according to the moving position of the spool 54, the opening degree of the flow process of the pressure port 58 and the inflow / outflow port 59, The opening degree of the flow process of the inflow / outflow port 59 and the tank port 60 is different.

For example, in a medium speed range in which the spool 54 slightly moves from the position shown in the drawing due to the action of the spring 57, the pressure port 58 and the inflow / outflow port 59 communicate with each other through the annular step 64, and the inflow / outflow port 59 and the tank port 60 communicate with each other through the annular step 65.

Therefore, in this case, a part of the pressure fluid supplied to the passage 51 is supplied to the reaction force chambers 7 and 8, and a part of the pressure fluid also flows to the tank T. The reaction chambers 7, 8
A little pressure acts on the handle H, and the operating force of the handle H is slightly increased by the pressure action.

When the vehicle travels at high speed, there is almost no pressure difference across the throttle 52, so the pilot chamber 5 of the reaction force pressure control valve V _O is not affected.
No pressure chamber is generated in 5, 56. Therefore, the spool 54 returns to the normal position due to the spring force of the spring 57, and the pressure port 58 and the inflow / outflow port 59 communicate with each other in a fully open state, while the communication between the inflow / outflow port 59 and the tank port 60 is cut off. .

Then, the pressure fluid supplied to the passage 51 is
The reaction chambers 7 and 8 are supplied to the reaction chambers 7 and 8 via the outflow / inflow port 59 and the communication between the reaction chambers 7 and 8 and the tank T is cut off. The pressure is at its maximum. When the pressure in the reaction chambers 7 and 8 is maximized, the steering operation becomes heavier.

As described above, the steering control valve 3 is the same as the conventional one, and the passage 51 is changed according to the switching position of the control valve 3.
Is supplied to one of the chambers of the power cylinder 5 and the other of the chambers communicates with the tank T.

The second embodiment shown in FIG.
_An inflow / outflow port 66 and a tank port 67 are formed in the _O valve body 53. The inflow / outflow port 66 communicates with the passage 51 via a fixed orifice 68 and also communicates with the reaction force chambers 7 and 8 of the steering control valve 3. An annular groove 69 is formed inside the inflow / outflow port 66, and an annular recess 70 and an annular step
The annular groove 69 and the annular step 71 are combined to form a variable orifice.

The configuration other than the above is the same as that of the first embodiment. Therefore, during low-speed traveling, the pressure in one pilot chamber 55 connected to the upstream side of the throttle 52 overcomes, and the spool 54
Is switched to the position shown in the figure, and the inflow / outflow port 66 and the tank port 67 are communicated in the fully opened state. Therefore, the pressure in the reaction chambers 7 and 8 is released from the inflow / outflow port 66 to the tank T via the tank port 67, so that no pressure acts on the reaction chambers 7 and 8. Thus, the pressure chamber 7,
Since no pressure acts on 8, the operating force of the handle H is reduced.

On the other hand, when the vehicle is running at medium speed, the differential pressure across the throttle 52 decreases, so the pressure difference between the pilot chambers 55 and 56 also decreases, and the spool 54 moves by the spring 57. At this time, the annular groove 69 and the annular step 71 And the variable orifice composed of.

When the variable orifice is opened as described above, the pressure fluid in the passage 51 flows to the tank T according to the opening degree, and at that time, a pressure difference occurs before and after the variable orifice. And
Since the pre-pressure acts on the reaction force chambers 7 and 8, a reaction force corresponding to the pre-pressure is generated, and the steering operation becomes slightly heavy.

In addition, during high-speed running, the pressure difference between the front and rear of the throttle 52 is minimized, so that the spool 54 switches to the normal position, and the communication between the inflow / outflow port 66 and the tank port 67 is cut off.

Therefore, the pressure of the passage 51 acts on the reaction force chambers 7 and 8,
Increase the handle operation.

In both of the above embodiments, the pressure source for supplying pressure to the inflow / outflow port is determined to be the pressure on the passage 51 side. However, a small pump may be specially provided as this pressure source.

[Brief description of the drawings]

FIGS. 1 and 2 show a first embodiment of the present invention.
FIG. 1 is a circuit diagram showing a specific section of a reaction force pressure control valve,
FIG. 2 is a sectional view of a flow control valve, FIG. 3 is a circuit diagram of a second embodiment, FIGS. 4 to 6 show a conventional apparatus, and FIG. FIG. 5 is a cross-sectional view of a steering control valve, and FIG. 6 is a cross-sectional view of a main part of a reaction pressure control valve. P: Pump, 3: Steering control valve, 5: Power cylinder, 7, 8 ... Pressure chamber, H: Handle, 52 ...
… Throttle, V _O … reaction force pressure control valve, 55, 56… pilot room, 59… outflow / inlet port, 60… tank port.

Claims (1)

(57) [Claims] 1. A speed-sensitive power steering system in which both ends of a spool of a steering control valve face a reaction force chamber, and the reaction force chamber communicates with a reaction force pressure control valve. A discharge control side for reducing the flow rate in proportion to the vehicle speed is connected to the discharge side of the pump, the discharge amount of which is variable in accordance with the vehicle speed, and a throttle is provided downstream of the flow control valve. A port connected to one of the pilot chambers of the reaction pressure control valve, the downstream side thereof is connected to the other pilot chamber, and the reaction pressure control valve has a port communicating with the reaction chamber of the steering control valve; A tank port connected to the tank is provided, and a fluid from a pressure source is guided to a reaction chamber of the steering control valve, and the port communicates with the tank port when the differential pressure across the throttle is large. The pressure in the reaction chamber is reduced by maximizing the opening of the flow path, and the pressure in the reaction chamber is increased by decreasing the opening of the passage connecting the two ports as the differential pressure decreases. Speed-sensitive power steering system.