JPH0215430B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power steering device.

(Prior art) Vehicle speed-sensitive power steering devices that reduce the power assist force by reducing the amount of pressure oil supplied to the power cylinder that assists the steering force as the vehicle speed increases are conventional power steering devices for automobiles. Are known.

In this vehicle speed sensitive power steering device, there is a proposal to further correct the amount of pressure oil supplied by the steering speed, as disclosed in Japanese Patent Laid-Open No. 57-66071. That is,
In this proposal, the reference line for the pressure oil supply amount (at zero steering speed) is set at a low level, and the higher the steering speed is, the more the pressure oil supply amount is corrected. Naturally, a response delay occurs until the oil supply amount control valve operates and the pressure oil supply amount actually increases to a predetermined value. In this case, the response delay appears as a lack of pressure oil supply immediately after turning the steering wheel, and as a result,
The driver feels a sense of resistance (feeling like it's stuck) when he or she begins to turn the steering wheel.

(Object of the Invention) In correcting the pressure oil supply amount according to the steering speed, the present invention uses a reference line for the pressure oil supply amount, contrary to the increase correction method according to the steering speed as in the prior art. By setting it to a high level and reducing the pressure oil supply amount,
This solves the problem of insufficient supply of pressurized oil immediately after a steering operation, and enables a good steering operation.

(Structure of the Invention) The power steering device according to the present invention includes: a power cylinder that assists the steering force; an oil pump that supplies pressure oil to the power cylinder; an oil amount control means that controls the amount of pressure oil supplied; and detects the running state of the vehicle. A steering sensor that detects the steering speed of the steering wheel. A controller that receives signals from the driving condition sensor and the steering sensor and issues a control signal to the flow rate control means. means for processing according to the signal processing characteristics, that is, the signal processing characteristics that correct the pressure oil supply amount in the direction of decreasing in response to the transition to high-speed driving state, and the maximum steering set by the signal of the driving state sensor. means for processing signals from the steering sensor in order to reduce the amount of pressure oil supplied from the amount of oil corresponding to the speed to a larger amount as the steering speed is lower, and based on the signal processing, send a control signal to the oil amount control means. It's starting to emanate.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In the power steering device 1 shown in FIG. 1, 2 is a steering wheel, 3 is a left and right wheel that constitutes the front wheels of an automobile, and 4 is a steering linkage that turns the wheels 3, 3 in the left-right direction in accordance with the rotational steering of the steering wheel 2. It is.

In this steering linkage 4, 5 is a steering shaft whose upper end is connected to the steering wheel 2, 6 is an intermediate shaft, and 7 is a lower shaft. A pinion 8 at the lower end of the lower shaft 7 meshes with a rack 10 of a rack shaft 9. Both ends are connected via tie rods 11 to a knuckle arm 12 that supports the wheel 3.

A power cylinder 13 is attached to the rack shaft 9 to assist the steering force of the steering wheel 2. The power cylinder 13 is connected to the rack shaft 9
The chamber is divided into a first chamber 15 and a second chamber 16 by a piston 14 fixed to the chamber. The first chamber 15 and the second chamber 16 communicate with a gear control valve 17 attached to the lower shaft 7 through oil passages 18 and 19.

The gear control valve 17 is connected to the engine 20
A pressure oil supply path 22 communicates with an oil pump 21 driven by
5 and the second chamber 16.
A return passage 23 extends from the gear control valve 17.

The pressure oil supply path 22 is provided with an oil amount control means 24 that controls the amount of pressure oil supplied from the oil pump 21 to the power cylinder 13 . The oil amount control means 24 includes a solenoid valve device 25 and a drain valve device 26. The electromagnetic valve device 25 includes a solenoid 27 and a spool valve 28 whose stroke position is controlled by the solenoid 27, and changes the passage area of the orifice 29 depending on the stroke position of the spool valve 28. That is, as the amount of current applied to the solenoid 27 increases, the spool valve 28 strokes toward the solenoid to throttle the orifice 29 and reduce the amount of pressure oil supplied.
The drain valve device 26 includes a valve body 31 that opens and closes the drain hole 30 and a spring that closes the valve body 31 in the drain hole closing direction. It is designed to drain some of the pressure oil.

A controller 32 that issues a control signal to the solenoid 27 is linked to the oil amount control means 24, and this controller 32 includes a running state sensor 33 that detects the running state (vehicle speed) of the vehicle and is attached to the lower shaft 7 of the steering linkage 4. A steering sensor 34 that detects the steering speed of the steering wheel 2 and a battery 35 are connected. The amount of current applied to the solenoid 27 is controlled by a controller 32 based on signals from a running state sensor 33 and a steering sensor 34.

The specific configuration of the controller 32 is shown in FIG.

In the same figure, 36 is an F/V converter that converts the pulse signal from the running state sensor 33 into voltage;
7 is from the driving state sensor 33 side and the steering sensor 34
38 is a set voltage output section that outputs a set voltage corresponding to the maximum steering speed; 39 is an adder that adds the output voltage of the amplifying section 37 and the set voltage. The output of the adder 39 and the output of the triangular wave generator 40 are input to the (+) side and (-) side of the comparator 41, respectively, and the output terminal of the comparator 41 is used to turn on the current to the solenoid 27. - Connected to the base of the transistor 42 that controls off. Further, 43 is a determination unit that determines whether or not the steering wheel 2 is being operated, which uses the output of the steering sensor 34 and the reference voltage generator 44.
The relay switch 48 is provided between the set voltage output section 38 and the adder section 39. The relay coil 46 is connected to the relay coil 46 and is turned on when the relay coil 46 is energized.

In the above circuit configuration, the voltage corresponding to the vehicle speed V input to the (+) side of the operational amplifier 49 in the amplifying section 37 is Ev, and the steering speed θ is input to the (-) side.
When the voltage corresponding to Eθ is assumed to be Eθ, the output voltage of the amplifying section 37 is K(Ev−Eθ). Note that K is a constant. Then, if the set voltage is Eo, the adder 3
The output voltage E of No. 9 is E=K(Ev−Eθ〓)+Eo.

Therefore, if we consider the relationship between the vehicle speed V and the pressure oil supply amount Q when the steering speed θ = 0, Eθ = 0
Moreover, since the set voltage Eo is not added, the output voltage of the adding section 39 is E=KEv, and the vehicle speed V=
If the output voltage at V ₁ (high speed) is E ₁ and the output voltage at V=V ₂ (low speed) is E ₂ , then E ₁ >E ₂ . this
The relationship between E ₁ , E ₂ and the pulsating voltage Ew of the triangular wave generator 40 is shown in FIG. 3a, and when the vehicle speed is high, the pulse signal output from the comparator 41 is The pulse width W ₁ is wide, and conversely, when the vehicle speed is low, the pulse width W ₂ becomes narrow as shown in FIG. 3c. Therefore, the amount of current applied to the solenoid 27 increases as the vehicle shifts to high-speed travel, and the amount of pressure oil supplied to the power cylinder 13 via the oil amount control means 24 decreases. The relationship between this vehicle speed V and the pressure oil supply amount Q is the fourth
In the figure, it is indicated by the line θ=0.

Next, looking at the relationship between the steering speed θ〓 of the steering wheel 2 and the amount of pressure oil supplied, when operating the steering wheel 2, the input voltage E of the comparator 41 is Ev, Eθ〓, Eo
is involved, and E=K(Ev−Eθ〓)+Eo. E when the steering speed θ = θ ₁ (large) and θ = θ ₂ (small) are respectively
If E ₁₁ and E ₂₂ , then E ₁₁ < E ₂₂ , and this E ₁₁ ,
The relationship between _E22 and the pulsating voltage Ew is as shown in FIG. 5a. When the steering speed is high, the pulse width W ₁₁ from the comparator 41 is narrow as shown in FIG. 5b.
When the steering speed is low, the pulse width W ₂₂ becomes wider as shown in FIG. 5c. Therefore, as the steering speed increases, the amount of current supplied to the solenoid 27 decreases, and the drain amount decreases, so as shown in FIG. 6, the pressure oil supply amount Q increases, and as a result, As shown in FIG. 7, the steering torque T remains approximately constant regardless of the magnitude of the steering speed.

Therefore, the output voltage E of the adder 39 when the steering wheel 2 is not being steered is different from that when the steering wheel 2 is not being steered.
KEv, during steering is KEv+(Eo−KEθ〓), and E _k >
Since KEθ〓, the output voltage during steering is higher than that during non-steering by (Eo - KEθ〓), and the amount of current applied to the solenoid 27 increases accordingly, resulting in the pressure oil supply amount Q.
decreases. In other words, the amount of decrease in the pressure oil supply amount Q corresponds to the value of (Eo - KEθ〓), and since Eθ〓 increases as the steering speed increases, the amount of decrease conversely becomes smaller. The relationship between the steering speed θ〓 and the amount of decrease is shown in Fig. 4, and the steering speed θ〓=
The amount of decrease q ₁ when θ ₁ (large) is θ = the amount of decrease when θ ₂ (small)
q less than ₂ .

That is, when the steering speed θ = 0, the pressure oil supply amount Q is the largest, and the lower the steering speed θ = 0, the greater the reduction amount becomes, and the pressure oil supply amount becomes optimal for that steering speed. Here, the relationship between the input state of the steering speed signal from the steering sensor 34, the amount of pressure oil supplied, the steering torque, and time is as shown in FIG. In other words, when a steering speed signal is input, there is a slight response delay and the pressure oil supply amount Q decreases from the maximum value Qmax to the optimal value _Q1 , but during this response delay, the pressure oil supply amount Q is in a state where it is more than the optimal value Q ₁ ,
The phenomenon of insufficient pressure oil supply does not occur. Therefore, although the steering torque T remains slightly low from the minimum value Tmin until it reaches the optimum value _T1 , the driver does not feel any resistance (squeezing) at the beginning of the steering operation.

In the above embodiment, the signal from the running state sensor 33 and the signal from the steering sensor 34 are combined to control one oil amount control means 24. A first oil amount control means and a second oil amount control means that responds to the signal from the steering sensor 34 are provided in parallel in the pressure oil supply path 22, and each flow rate control means is controlled individually based on the driving state signal and the steering speed signal. It may also be controlled.

Further, as the driving state sensor, an engine rotation sensor, a transmission gear position sensor, etc. may be used in addition to the vehicle speed sensor.

Further, in the embodiment, the reference voltage generator 44 is used in the determination unit 43 for determining whether or not the steering wheel is being operated, but the (-) side of the comparator 45 may be grounded and the reference voltage may be set to 0V.

(Effects of the Invention) The present invention sets the pressure oil supply amount characteristic when the steering speed is zero to a level corresponding to the maximum steering speed, and reduces the pressure oil supply amount according to the steering speed to a greater extent as the steering speed is lower. This makes it possible to secure the required amount of oil corresponding to the steering speed at the start of the steering operation, so that the driver does not feel stuck in the steering operation (resistance), and the operability of the steering can be improved.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention; FIG. 1 is an overall configuration diagram of a power steering device, FIG. 2 is a control circuit diagram, and FIG. , Figures 3b and 3c are output characteristic diagrams of the same comparator, Figure 4 is a characteristic diagram showing the relationship between vehicle speed and pressure oil supply amount, and Figures 5a, b, and c are graphs showing the relationship between changes in steering speed. FIG. 6 is a characteristic diagram showing the relationship between steering speed and pressure oil supply amount; FIG. 7 is a characteristic diagram showing the relationship between steering speed and steering torque; FIG. 8 is an explanatory diagram of the response delay, and a, b, and c are characteristic diagrams showing the input state of the steering speed signal, the amount of pressurized oil supplied, and the change over time in the steering torque, respectively. 1... Power steering device, 2... Steering, 3... Wheels, 13... Power cylinder,
21...Oil pump, 22...Pressure oil supply path, 2
4...oil amount control means, 32...controller, 3
3... Running state sensor, 34... Steering sensor.

Claims (1)

[Claims] 1. A power cylinder that assists the steering force of the steering wheel, an oil pump that supplies pressure oil to the power cylinder, and an oil amount control means that controls the amount of pressure oil supplied from the oil pump to the power cylinder.
A driving condition sensor detecting the driving condition of the vehicle, a steering sensor detecting the steering speed of the steering wheel,
Processes the signal from the driving condition sensor according to predetermined signal processing characteristics, reduces the amount of pressure oil supply in response to transition to high-speed driving condition, processes the signal from the steering sensor, and processes the signal from the steering sensor. and a controller that issues a control signal to the flow rate control means to correct the amount of pressure oil supplied by decreasing the amount of oil corresponding to the maximum steering speed set by the signal from the amount corresponding to the maximum steering speed set by the signal. power steering device.