JPH03159878A - Variable capacity pump device for power steering - Google Patents

Abstract

PURPOSE:To reduce the pump driving torque and lessen the heat emittion from pump by furnishing a variable throttling means controlled according to car speed signals on the way of an oil path on the suction side of the pump, which is to discharge the working oil to the discharge oil path coupled with a power steering gear. CONSTITUTION:A radial piston pump 5 driven by engine sucks in e working oil stored in a reserve tank 1 through a suction side oil path 2 and discharges to a power steering gear 3 through a discharge path 4. In this pump 5 a piston 5l is put in pressure contact with the peripheral of an eccentric cam 5g formed on the drive shaft 5d, and the working oil sucked with reciprocative motion of this piston 5l in a cylinder 5k is boosted and discharged. Therein a variable throttle mechanism 6 is installed on the way of the mentioned suction oil path 2. To a proportional solenoid 8 of this variable throttle mechanism 6, a throttle opening control command as decreasing the rate of discharge flow with higher can speed is emitted from a controller 9, which is to be fed with an output signal of a car speed sensor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle speed-sensitive variable capacity bomb device for power steering.

(Conventional technology) Conventionally, when making a low-speed turn with a large steering reaction force, the steering assist force is increased to reduce the steering force required for turning, and when making a high-speed turn with a small steering reaction force, the steering assist force is reduced to reduce the steering force required for turning. For the purpose of suppressing wobbling and ensuring steering stability, a variable displacement pump device for power steering that reduces the discharge flow rate supplied to the power steering gear as the vehicle speed increases is disclosed in, for example, Japanese Patent Laid-Open No. 60-176866. Those described in official gazettes are known.

(Problem to be Solved by the Invention) However, in the variable displacement pump device for power steering, a flow control valve (or variable orifice) is provided in the middle of the discharge oil path of the pump, and the amount of oil discharged from the pump is controlled. Since the configuration is such that the discharge flow rate supplied to the power steering gear is controlled by draining a portion, there have been problems as listed below.

■ The structure uses a flow control valve, etc. to limit the excessive amount of oil discharged from the pump.
Flow control valves, etc. act as flow path resistance in the discharge oil path, causing a large pressure loss in the pump.

As a result, the pump driving torque increases at least by an amount corresponding to the pressure loss, and the amount of heat generated by the pump also increases.

■ Since the flow control valve, etc. is installed in the middle of the discharge oil path, that is, on the high pressure side, the hydraulic liquefaction that acts on the flow control valve, etc. becomes large.

As a result, in order to prevent oil leakage, high machining precision is required for flow control valves, etc., and since the thrust of proportional solenoids etc. also requires high thrust, large flow control valves, etc. must be used. It won't happen.

The present invention has been made with attention to the above-mentioned problems, and in a vehicle speed-sensitive variable displacement pump device for power steering, it is possible to reduce the pump drive torque and the amount of heat generated by the pump, and to improve the machining accuracy of the discharge flow rate control means. The challenge is to achieve a reduction in energy consumption and miniaturization.

(Means for Solving the Problems) In order to solve the above problems, in the variable displacement pump device for power steering of the present invention, a variable throttle means for controlling the discharge flow rate is provided in the middle of the suction oil path of the pump.

That is, the pump is driven by an engine and sucks hydraulic oil from a reserve tank through a suction oil passage and discharges it to a discharge oil passage connected to a power steering gear, and a variable throttle means is provided in the middle of the suction oil passage. , a discharge flow rate control means that takes at least a vehicle speed signal as an input signal and outputs a throttle opening control command to the variable throttle means based on the input signal;
It is characterized by having the following.

(Function) When turning, the discharge flow rate control means that uses the vehicle speed signal as an input signal sends a throttle opening control command to the variable throttle means provided in the middle of the suction oil passage to reduce the discharge flow rate as the vehicle speed increases. Output.

Therefore, when turning at low speeds, the throttle opening of the suction passage is set to a large degree, and a high discharge flow rate is supplied to the power steering gear, providing a large steering assist force and reducing the steering force required for turning. .

In addition, during high-speed turns, the throttle opening of the suction oil passage is set small, and a low discharge flow rate is supplied to the power steering gear, providing a small steering assist force, suppressing steering wheel wobbling, and improving steering stability. is ensured.

(First example) First, the configuration will be explained.

FIG. 1 shows a variable displacement pump device for power steering according to the first embodiment, which is driven by an engine (not shown), sucks hydraulic oil from a reserve tank 1 through an intake oil passage 2,
A radial piston pump 5 (pump) discharges oil to a discharge oil passage 4 connected to the power steering gear 3, a variable throttle mechanism 6 (variable throttle means) provided in the middle of the suction oil passage 2, and a vehicle speed sensor 7. PS controller 9 (discharge flow rate control means) takes the vehicle speed signal as an input signal and outputs a throttle opening control command to the proportional solenoid 8 of the variable throttle mechanism 6 so that the higher the vehicle speed V, the lower the discharge flow rate. ).

The radial piston pump 5 has a pump casing 5a.
bearing 5b. Drive shaft 5 rotatably supported by 5c
d, and an eccentric cam 5 provided at the center of the drive shaft 5d, which is formed in an oil-tight state by oil seals 5e and 5f.
9, a suction chamber 5j formed in a portion where the eccentric cam 59 is provided and communicating with the suction port 5h and the suction path 5l;
A plurality of fixed cylinders 5k are formed in equiangular radial directions from the suction chamber 5J, a piston 5β disposed in each of the fixed cylinders 5k, and a subring 5m that presses the piston 5β against the outer periphery of the eccentric cam 59. and the piston 5I2. a suction side port 5n that is opened in the side wall of the suction chamber 5n and retracts from the suction chamber 5J as the piston reciprocates;
A cylinder chamber 50 that can communicate via the suction side boat 5n, a discharge passage 5p that communicates with the cylinder chamber 50, a delivery valve 5q provided in the middle of each discharge passage 5p, and a discharge from each delivery valve 5q. It has a discharge port 5r that collects oil in one place.

In the figure, 5s is a cylinder sleeve, 5t is a pin, and 5u is a casing plate.

The variable throttle mechanism 6 includes a valve body 6a fixed to the bomb casing 5a, a valve hole 6b formed in the valve body 6a, and a spool slidably provided in the valve hole 6b in the left-right direction in the drawing. 6c, a spring 6d that urges the spool 6c to the left in the drawing, a rod 6e that applies electromagnetic force by the proportional solenoid 8 to the right in the drawing to the spool 6C, and a rod 6e connected to the suction oil passage 2 and the suction port 6f. An inlet passage 69 that communicates with the suction boat 5h of the pump 5, an outlet passage 6h that communicates with the suction boat 5h of the pump 5, a communication passage 6j that communicates the inlet passage 69 with the spring chamber 61, and the spring chamber 61 and the rod chamber 6k. When the electromagnetic force to the proportional solenoid 8 is zero, the passage area (aperture opening) of the throttle part 6m is the minimum, and the electromagnetic force to the proportional solenoid 8 is the maximum. It is configured so that the aperture opening is at its maximum.

Next, the effect will be explained.

(B) Aperture opening setting function FIG. 2 shows the relationship between the suction chamber pressure P and the discharge flow rate.

According to FIG. 2, when the drive shaft rotation speed of the pump 5 is Ni, the suction chamber pressure P becomes P1, and the discharge flow rate Q becomes the specific discharge flow rate Qio. That is, when the suction chamber pressure P becomes equal to or higher than Pi, a discharge flow IQ equal to or greater than the specific discharge flow rate Qio is obtained.

It can be seen that when the suction chamber pressure P'b<Pi or less, the discharge flow rate 0 is limited to the specific discharge flow rate 010 or less. This is because the differential pressure between the cylinder chamber 50 and the suction chamber 5J becomes small, and the specific discharge amount cannot be sucked in from the suction side port 5n at 5° C. of the piston.

That is, when the drive shaft rotation speed of the pump 5 is equal to or higher than Ni, the suction chamber pressure P is set to Pmin (> Pg: air separation pressure).
By changing the flow rate from Qmin to Pi, it is possible to obtain a discharge flow rate Q that changes from Qmin to Oio.

On the other hand, in the power steering pump, the maximum required flow rate is when the engine is idling, so if the drive shaft rotation speed of the pump 5 at that time is Ni, the throttle part 6m is throttled so that the suction chamber pressure Pb<Pi when the pump Ni is rotating. Set the maximum area of opening.

Further, the minimum area of the throttle opening of the throttle portion 6m is set so that the suction chamber pressure P'b<Pmin.

Further, while the suction chamber pressure P is from Pmin to Pi, the relationship between the suction chamber pressure P and the discharge flow rate Q does not change.

This is because the differential pressure between the cylinder chamber 50 and the suction chamber 5J is constant (during piston suction, the suction ends with the air generated by cavitation remaining, so the cylinder chamber pressure is constant at the air separation pressure P9), and the pump This is because even if the rotational speed of the drive shaft increases and the number of suctions increases, the time for each suction becomes shorter, and the amount of suction from the five suction side ports does not change.

Therefore, by setting the aperture opening as described above, the third
As shown in the figure, when the pump drive shaft rotation speed is N1 or more, the minimum discharge flow rate Qmin to prevent pump seizure etc.
The flow rate can be controlled by adjusting the aperture opening between the flow rate and the specific discharge flow 'Jx O io, and the range shown by hatching in FIG. 4 is the flow rate control range.

(Example) Operation of the variable throttle mechanism A pressure balance is maintained at both ends of the sboule 6c by an intra-sboule communication passage 6β.

When the current value energized to the proportional solenoid 8 is increased, the subur 6C is pushed from the rod 6e by electromagnetic force and moves to the right in the drawing against the spring 6d, increasing the throttle opening of the throttle section 6m.

Also, if the current value applied to the proportional solenoid 8 is reduced,
On the contrary, the biasing force of the spring 6d of 1 0 overcomes the electromagnetic force, and the Subur 6C moves to the left in the drawing, reducing the aperture opening.

That is, the subur 6C is stopped at a position where the electromagnetic force generated by the proportional solenoid 8 and the biasing force generated by the spring 6d are balanced, and the aperture opening degree can be obtained in accordance with the magnitude of the electromagnetic force.

(c) When turning at low speed, a large current value is supplied from the PS controller 9 to the proportional solenoid 8 in accordance with the vehicle speed information from the vehicle speed sensor 7, and the aperture opening degree is set to a large value.

Furthermore, when turning at high speed, a small (or zero) current value is supplied from the PS controller 9 to the proportional solenoid 8 in accordance with vehicle speed information from the vehicle speed sensor 7, and the aperture opening degree is set small.

Therefore, when turning at low speed with a large steering reaction force, a discharge flow rate close to the specific discharge flow rate Qio is supplied to the power steering gear 3, and a large steering assist force is applied, reducing the steering force required for turning. Ru.

11 In addition, during high-speed turns with small steering reaction force, a discharge flow rate close to the minimum discharge flow rate Qmin is supplied to the power steering gear 3, and a small steering link assist force is applied, suppressing steering wheel wobbling and improving steering performance. Stability is ensured.

Furthermore, even when there is no current applied to the proportional solenoid 8 due to a failure in the electrical control system due to a disconnection, the minimum discharge flow ff
By securing iomin, pump 5 in case of fail.
Burn-in is prevented.

In addition, in order to reduce response delay, a steering angle sensor, etc. is added to the input sensor, and the steering angle, steering speed, etc. The turning operation may be predicted based on the steering force or the like, and control may be applied in advance to increase the discharge flow rate.

As explained above, in the variable displacement pump device for bass steering according to the first embodiment, since the variable throttle mechanism 6 for controlling the discharge flow rate is provided in the middle of the suction oil path 2 of the pump 5, the following The features listed below can be obtained.

■ The discharge oil passage 4 from the pump 5 does not have a conventional valve, flow control valve, etc. that acts as a flow resistance in the discharge oil passage 4, so pressure loss in the pump 5 is reduced. .

As a result, the pump drive torque can be reduced compared to the prior art, and the amount of heat generated by the pump 5 is also reduced.

■ Since the variable throttle mechanism 6 that controls the discharge flow rate is installed in the middle of the suction oil passage 2 on the low pressure side, the variable throttle mechanism 6
The hydrostatic force acting on the Subur 6c becomes smaller.

As a result, oil leakage can be sufficiently prevented even if the machining accuracy of the valve hole 6b, subur 60, etc. of the variable throttle mechanism 6 is lowered compared to the conventional technology, and the thrust by the proportional solenoid 8 is also increased. Since no thrust is required, the variable diaphragm mechanism 6 can be made compact.

(Second Embodiment) FIG. 5 shows a variable displacement pump device for power steering according to a second embodiment.
In contrast to the configuration in which the minimum diaphragm opening is obtained when the current applied to the proportional solenoid 8 is zero, in this 21st embodiment, the maximum diaphragm opening is obtained when the current applied to the proportional solenoid 8 is zero. The difference is that

That is, the subru 6c has a different land position from the first embodiment.
' The only difference is that it is structurally different.

Note that the other configurations are the same as those in the first embodiment, so corresponding configurations are denoted by the same reference numerals and description thereof will be omitted.

As for the effects, the electrical control system failed due to disconnection.
Since the specific discharge flow ftQio can be supplied to the power steering gear 3 even when no current value is applied to the proportional solenoid 8, the steering force is prevented from increasing in the event of a failure.

Note that other effects are the same as those in the first embodiment, so their explanations will be omitted.

(Third Embodiment) FIG. 6 shows a variable displacement pump device for power steering according to a third embodiment.
The third embodiment differs in that the suction chamber pressure P of the pump 5 is feedback-controlled.

That is, when comparing the variable throttle mechanism 6 with the first embodiment, the spool internal communication passage 6°C is eliminated, and the feedback pressure oil passage 6 that communicates the outlet side passage 6h with the spring chamber 61 is provided, and the rod chamber 6k is The configuration includes a communication path 6o that communicates the intake port 6f with the intake port 6f.

Note that the other configurations are the same as those in the first embodiment, so corresponding configurations are denoted by the same reference numerals and description thereof will be omitted.

As for the effects, when the current supplied to the proportional solenoid 8 is constant, the spool 6c moves to control the suction chamber pressure P to a constant throttle opening, which improves the discharge flow rate control accuracy and improves the machining accuracy. Less affected by variations.

Note that other effects are the same as those in the first embodiment, so their explanations will be omitted.

(Fourth Embodiment) Fig. 7 shows a variable displacement pump device for power steering according to a fourth embodiment. However, in this fourth embodiment, in order to further improve the control accuracy, a pressure sensor 10 is provided at the outlet side passage 6h position to monitor the suction chamber pressure P. The difference is that the configuration controls the discharge flow rate.

Note that 6p is a communication passage that communicates the spring chamber 6l and the suction port 6f.

Note that the other configurations are the same as those in the first embodiment, so corresponding configurations are denoted by the same reference numerals and description thereof will be omitted.

Therefore, in this fourth embodiment, since the throttle opening degree can be controlled while monitoring the suction chamber pressure P using the signal from the pressure sensor 10, it is possible to control the discharge flow rate more accurately.

In addition, in order to sense the discharge flow rate, a throttle is generally provided in the middle of the discharge oil passage 4, and the pressure difference is measured before and after the throttle, but in this case, the configuration of the flow sensor becomes complicated, leading to increased costs and Since the restriction acts as a flow resistance and increases the pressure loss of the pump 5, problems such as an increase in the pump driving torque and heat generation of the pump 5 occur, but such problems do not occur in the fourth embodiment.

Note that other effects are the same as those in the first embodiment, so their explanations will be omitted.

(Fifth Embodiment) FIG. 8 shows a variable displacement pump device for power steering according to a fifth embodiment, in which the variable throttle means of the first to fourth embodiments includes a proportional solenoid 8 and a Subur valve serving as a throttle. Whereas the variable aperture mechanism 6 was a combination of
The fifth embodiment uses a duty solenoid valve 16 that can change the apparent throttling effect by changing the time ratio of opening and closing the valve based on the duty solenoid signal.

Note that the other configurations are the same as those in the first embodiment, so corresponding configurations are denoted by the same reference numerals and description thereof will be omitted.

Functionally, the duty solenoid valve 16 has an ON-OFF valve configuration that switches between the previous time and the closed state, so it is resistant to contamination by dust and fine particles.

Furthermore, since the duty 1 7 solenoid valve 16 with a simple valve configuration is effectively used, the cost is low, and furthermore, in the event of a failure such as a wire breakage, the discharge flow rate with the throttle opening fully open can be ensured.

Note that other effects are the same as those in the first embodiment, so their explanations will be omitted.

Although the embodiment has been described above based on the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change within the scope of the gist of the present invention, it is included in the present invention. .

(Effects of the Invention) As explained above, in the present invention, in a vehicle speed-sensitive variable displacement pump device for power steering, a variable throttle means for controlling the discharge flow rate is provided in the middle of the suction oil path of the pump. Therefore, it is possible to reduce the pump driving torque and the amount of heat generated by the pump, and also to reduce the machining accuracy and downsize of the discharge flow rate ffil m means.

[Brief explanation of the drawing]

Fig. 1 is an overall diagram showing a variable displacement pump device for power steering according to the first embodiment of the present invention, Fig. 2 is a characteristic diagram of discharge flow rate with respect to suction chamber pressure, and Fig. 3 is a characteristic diagram of discharge flow rate with respect to throttle opening. , FIG. 4 is a diagram showing the discharge flow rate control range with respect to the pump rotation speed, FIG. 5 is an overall view showing a variable displacement pump device for power steering according to the second embodiment of the present invention, and FIG. 6 is a diagram showing the third embodiment of the present invention. FIG. 7 is an overall view showing a variable displacement pump device for power steering according to the fourth embodiment of the present invention, and FIG. 8 is a general view showing a variable displacement pump device for power steering according to the fifth embodiment of the present invention. FIG. 2 is an overall view showing a variable displacement pump device. 1... Reserve tank 2... Suction oil path 3... Power steering gear 4... Discharge oil path 5... Radial piston pump (pump) 6... Variable throttle mechanism (variable throttle means) 7 ...Vehicle speed sensor 1 9 8...Proportional solenoid 9...PS control (discharge flow rate control means) 16...-Duty solenoid (variable throttle means) De valve

Claims (1)

[Scope of Claims] 1) A pump driven by an engine that sucks hydraulic oil from a reserve tank through a suction oil passage and discharges it to a discharge oil passage connected to a power steering gear, and a pump provided in the middle of the suction oil passage. A power steering system characterized by comprising: variable throttle means configured to control the variable throttle means; and discharge flow rate control means that receives at least a vehicle speed signal as an input signal and outputs a throttle opening control command to the variable throttle means based on the input signal. Variable displacement pump device for use.