JPH02175467A - Speed sensitive power steering device - Google Patents

Abstract

PURPOSE:To prevent deterioration in responsiveness even in case of quick handle operation by providing a variable throttle valve and a variable aperture in a by-pass passage arranged parallel to a steering control valve. CONSTITUTION:An electromagnetic variable throttle valve V and a variable aperture VO disposed on the downstream side thereof are connected to a by-pass passage 6. The electromagnetic variable throttle valve V is electrically connected to a controller C, and the opening of the valve is controlled according to an input signal from a car velocity sensor 5. The opening of the variable aperture VO is controlled, interlocking with the operation of a handle H. During medium high speed running, even if the opening of the electromagnetic variable throttle valve V is kept at maximum, when the handle H is turned largely, the variable aperture VO is closed so as to lessen the rate of flow passing through a by-pass passage 6 and flowing in a tank T among the discharge quantity of a pump P. In other words, even during medium high speed running, the flow rate to a power cylinder PC can be ensured so as to prevent conventional lowering of responsiveness due to shortage of flow.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle speed sensitive power steering device that controls power assist force in accordance with vehicle speed.

(Prior Art) In the conventional device shown in FIG. 4, the supply passage l connected to the pump P is connected to the inflow boat 2 side of the steering control valve SV, and the outflow boat 3 of the steering control valve SV is connected to the inflow boat 2 side of the steering control valve SV. It communicates with the tank T via a return passage 4.

The steering control valve Sv shown in L is switched in relation to the operation of the steering wheel H. A power cylinder PC whose moving direction is controlled according to the switching position of the control valve SV is connected to the steering 1111 valve SV thus constructed.

-An electromagnetic variable throttle valve 9 is connected to the supply passage l, but this '4! Magnetic variable throttle valve 9.

It is electrically connected to controller C. A heavy speed sensor 5 is connected to this controller C.

The vehicle speed sensor 5 thus configured detects the vehicle speed of the vehicle and sends the detected vehicle speed signal to the controller C. The controller C that receives this vehicle speed signal controls the opening degree of the variable throttle valve 9 according to the vehicle speed signal, but the higher the speed of the vehicle, the smaller the opening degree of the RIF variable throttle valve 9. That's what I do.

Between the supply passage 1 and the return passage 4 as described above,
Although the bypass passage 6 is connected, this bypass passage 6
The intersection point between the variable throttle valve 9 and the supply passage 1 is located on the upstream side of the variable throttle valve 9. A discharge valve 7 is connected to this bypass passage 6.

On both sides of the discharge valve 7 thus constructed, a pilot chamber 7a,
7b is provided, and one pilot chamber 7at is connected to the L flow side of the electromagnetic variable throttle valve 9.

The other pilot chamber 7b is connected to the downstream side of the electromagnetic variable throttle valve 9. Further, a spring 8 is provided on the other pilot chamber 7b side, so that the discharge valve 7 maintains the illustrated position in the normal state AE.

When the heavy vehicle is traveling at low speed, the controller C operates in accordance with the vehicle speed signal to maximize the opening degree of the electromagnetic El variable throttle valve 9. In this manner, when the opening degree of the +2T variable throttle valve 9 is maximized, almost no differential pressure is generated before and after the opening, so that the discharge valve 7 maintains the normal position shown in the figure by the action of the spring 8 and closes the bypass passage 6. In other words, almost the entire discharge flow rate from the pump P is supplied to the power cylinder PC via the steering control valve SV.

As the flow ■ supplied to the power cylinder PC increases in this way, the output of the cylinder PC also increases.
The power assist power increases accordingly.

In addition, when the vehicle is running at high speed, the controller C
reduces the opening degree of the electromagnetic variable throttle valve 9. Like this M
As the opening degree of the magnetic variable throttle valve 9 becomes smaller, the pressure difference before and after it becomes larger, and this pressure difference acts on the pilot chambers 7a and 7b of the discharge valve 7. Therefore, the discharge valve 7 opens according to the pressure difference, and a part of the discharge amount of the pump P is transferred to the bypass passage 6 according to the opening degree of the discharge valve 7.
In other words, the flow rate supplied to the steering control valve Sv is reduced by the flow rate returned to the tank T via the bypass passage 6.

Then, when the opening degree of the electromagnetic variable throttle valve 9 becomes fully closed,
Since the entire discharge amount of the pump P is returned to the tank T via the bypass passage 6, the power assist force at that time becomes zero.

(Problems to be Solved by the Present Invention) In the conventional device as described above, if the supply flow rate to the power cylinder PC is extremely reduced when the vehicle is running at medium to high speeds, it may cause rapid steering operation or There was a problem in that when the manipulated variable was increased, a flow rate was insufficient, resulting in poor responsiveness.

Furthermore, if a certain amount of flow rate is supplied even at medium and high speeds in order to prevent the above-mentioned decrease in responsiveness, the range of flow rate change becomes narrower. As the range of flow rate variation becomes narrower, the degree of freedom in selecting the steering force has to be narrowed accordingly, which also poses a problem in that it becomes difficult to set the optimum steering force for the vehicle speed.

An object of the present invention is to provide a device 2 that does not deteriorate responsiveness even when the steering wheel is operated quickly.

(Means for Solving the Dark Problem) The present invention provides a steering control valve that switches in relation to steering wheel operation, a pump that supplies pressure fluid to the power steering control valve, and a combination of the pump and the steering control valve. A connecting supply passage, a return passage connecting the steering control valve to the tank, a power cylinder that is driven in accordance with the switching direction of the steering control valve, and connecting the supply passage and the return passage; It is equipped with a bypass passage parallel to the steering control valve and a variable throttle valve that divides the pump discharge amount into the steering control valve and the bypass passage, and the opening degree of this RIF variable 1 throttle valve is increased when driving at medium and high speeds. In addition, the opening degree of the bypass passage is adjusted to HVH in relation to the handle operation, and a throttling resistance is applied to the fluid flowing into the bypass passage. It is characterized by the provision of a variable diaphragm.

(Effects of the present invention) Since the present invention is configured as shown in ``-'', the opening degree of the nj variable throttle stop t is controlled according to the vehicle speed of the vehicle. The flow rate discharged to the bypass passage is determined according to the opening degree of this U-shaped throttle valve, and the remaining flow rate is supplied to the steering control valve side. therefore,
In principle, the flow rate supplied to the power cylinder is controlled in accordance with the opening degree of the variable throttle valve.6 Also, the opening degree of the variable throttle provided in the bypass passage J2 is
Since it changes in conjunction with the steering wheel operation, even when the variable throttle is opened to the maximum, in other words, even when the vehicle is running at medium to high speeds, the flow rate supplied to the power cylinder can be increased by continuously changing the steering wheel operation. can do.

(Effects of the present invention) According to the device of the present invention, even when the opening degree of the variable throttle valve is large, such as when driving at medium and high speeds, the opening degree of the variable throttle valve can be made small in conjunction with the handle operation. By reducing the flow rate discharged from the bypass passage, the supply flow m to the power cylinder can be ensured. Therefore, there is no problem of low responsiveness due to insufficient flow rate.

(Embodiment of the present invention) In the embodiment shown in FIGS. 1 to 3, an electromagnetic variable throttle valve V is connected to the bypass passage 6 and a variable throttle vO is connected to the downstream side thereof. , is electrically connected to the controller C, and controls its opening according to the input signal from the vehicle speed sensor 5. The opening within the X unit is maximized when the vehicle is running at medium to high speeds, and minimized when the vehicle is running at low speeds. And the electromagnetic variable throttle valve V
When the opening degree of is maximized, almost the entire discharge amount of the pump P is returned to the tank T via the bypass passage 6. Therefore, the supply flow rate to the power cylinder PC decreases,
The power assist force becomes weaker accordingly. Furthermore, when the opening degree of the electromagnetic variable throttle valve V becomes the minimum, the bypass passage 6 is closed, so that almost all of the discharge amount h1 of the pump P is
is supplied to the power cylinder PC, and the power assist force is maximized.

The variable opening throttle vO provided on the downstream side of the electromagnetic variable throttle valve V as described above changes its opening degree Ilm in conjunction with the operation of the handle H. However, this variable aperture VO
is incorporated in the steering control valve SV, and its specific configuration is as shown in FIG. 2.3.

That is, in the case 12 of the steering control valve Sv,
A stubshaft 7H3 and a pinion shaft 14 are rotatably installed inside the shaft, and these shafts 13 and 14 are connected via a torsion/<-15.

The stub shaft 13 is connected to the handle H and forms a spool portion 16 around it. Then, a sleeve 17 is provided around this spool portion 16,
These spool portion 16 and sleeve 17 together constitute a rotary valve RV.

In addition, the rack shaft 1 is attached to the above-mentioned binion shaft 14.
A binion 14a that engages with the rack 18a is formed, and this rack shaft I8 is connected to the power cylinder P.
C and the wheels.

The pinion shaft 14 thus constructed has a relay chamber 1θ
A plunger 21 is installed together with a spring 20 in this relay chamber 19. The sliding direction of the plunger 21 is parallel to the axes of the stub shear 7H3 and the pinion shaft 14.

The relay chamber z9 communicates with the bypass passage 6 on the downstream side of the 'jrt magnetic variable throttle valve V via the inboard 22 and the throttle hole 23. Furthermore, this relay chamber 19 has a passage hole 24→a passage 25 formed around the torsion bar 15→
Discharge hole 26 formed in stub shaft 13 → case 12
It is connected to the return passage 4 side via an outflow boat 3 formed in .

In addition, the stub shaft 13 shown in h is provided with a flange portion 27 that protrudes in the radial direction, and the flange portion 27 has a 1-
The plunger 21 is brought into pressure contact. A V-shaped groove 28 is formed on the contact surface with which the plunger 21 presses.

Therefore, from IE with the handle held in the middle position,
When it is turned to either the left or right, the stub shirt 13 also rotates accordingly. However, the pinion shaft 1
Since shaft 4 does not rotate due to the influence of ground resistance, only stub shaft 13 is displaced relative to shaft 2 and pinion shaft 14.

When the stub shirt [3] is relatively displaced as described above, the rotary valve RV is changed depending on the displacement acid, so either one of the chambers of the power cylinder PC is communicated with the pump P via the high pressure boat 29, The other chamber is connected to the tank T via the outflow boat 3. Therefore, the front wheels linked to this power cylinder PC are steered in a predetermined direction. When the power cylinder PC operates like this,
Along with this, the rack shaft 18 moves and the pinion shaft 14 also rotates. In other words, power cylinder P
When C operates, the stub shaft 13 and the pinion shaft 14 continue to rotate while being relatively displaced.

, 1- When the rotary valve RV is switched as described in 1- and the discharge fluid of the pump P is supplied to the power cylinder PC, 1! according to the running speed of the 1E car at that time. The opening degree of the magnetic variable throttle valve ■ is determined, and the supply flow to the power cylinder PC is determined according to the opening degree! As mentioned above, the detour is controlled. At this time, the fluid that has passed through the electromagnetic variable throttle valve V is returned to the tank T in the following manner.

That is, the fluid that has passed through the variable throttle valve V flows through the inboard 22 → throttle hole 23 → relay chamber 18 → through hole 24 → passage 25 →
The discharge hole 28 is returned to the tank T via the discharge boat 3.

When the handle H is operated quickly with the opening degree of the electromagnetic variable throttle valve V fixed as described above, the plunger 21 is pushed out of the ■-shaped groove 28 and rotates relative to the flange portion 27. do. In this way plunger 2
1 is pushed out from the groove 28, the plunger 2I moves against the spring 20 and closes the throttle hole 23.

That is, in this embodiment, the aperture hole 23 and the plunger 21 constitute the variable aperture vO in the circuit diagram of FIG.

Therefore, for example, when driving at medium and high speeds, the electromagnetic variable throttle rib fv
Even when the opening degree of the pump P is maintained at the maximum, if the handle H is turned significantly, the variable throttle valve VO closes, so that part of the discharge amount of the pump P passes through the bypass passage 6 and is transferred to the tank T.
The flow rate flowing into the area decreases. In other words, even when traveling at medium and high speeds, the flow rate to the power cylinder PC can be ensured, so that it is possible to prevent a decrease in responsiveness due to insufficient flow rate as in the conventional case.

Furthermore, since the variable throttle vO is controlled according to the amount of operation of the handle H, the range of flow rate change depending on the vehicle speed can be widened. The wider the range of flow rate variation, the wider the degree of freedom in selecting the steering force, which makes it easier to set the steering force optimal for the vehicle speed.

[Brief explanation of the drawing]

Drawings 1 to 3 show embodiments of this invention.
2 is a sectional view of the main part, FIG. 3 is a partial sectional view showing the relationship between the plunger and the V-shaped groove, and FIG. 4 is a circuit diagram of a conventional device. H...handle, Sv...steering control valve, P
... Pump, 1... Supply passage, T... Tank, 4
...Return passage, PC...Power cylinder, 6...
Bypass passage, ■...Variable throttle valve, vO...Variable throttle.

Claims (1)

[Claims] A steering control valve that switches in relation to steering wheel operation, a pump that supplies pressure fluid to this power steering control valve, a supply passage that connects this pump and the above-mentioned steering control valve, and connecting the steering control valve to a tank. a power cylinder that is driven in accordance with the switching direction of the steering control valve; a bypass passage that connects the supply passage and the return passage and is parallel to the steering control valve; The vehicle is equipped with a variable throttle valve that divides the discharge amount into the steering control valve and the bypass passage, and is configured to increase the opening degree of the variable throttle valve during medium-high speed driving to increase the discharge flow rate to the bypass passage. The vehicle speed sensitive power steering device is provided with a variable throttle in the bypass passage whose opening degree is controlled in relation to steering wheel operation and which applies throttle resistance to the fluid flowing into the bypass passage.