JP2502365B2 - Vehicle fluid pressure supply device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vehicle fluid pressure supply device, and in particular,
A fluid pressure cylinder for the active suspension that has a fluid pressure cylinder interposed between the vehicle body and wheels and a control valve that controls the pressure of this cylinder, and controls roll rigidity, pitch rigidity, etc. by changing the cylinder pressure. Regarding the improvement of the feeding device.

[Conventional technology]

As a conventional fluid pressure supply device for a vehicle body, there is, for example, a structure proposed by the present applicant in Japanese Patent Laid-Open No. 63-251313.

The hydraulic pressure supply device in this conventional example has a variable discharge amount hydraulic pump connected to a rotary drive source such as an engine, and a discharge amount of pressure oil per one rotation of the hydraulic pump during vehicle traveling from when the vehicle is stopped. And a discharge amount control means for increasing the discharge amount. The essential part is a structure in which the hydraulic pressure based on the discharge amount thus controlled is supplied to a hydraulic cylinder interposed between the sprung and unsprung parts via a control valve such as a pressure control valve.

[Problems to be Solved by the Invention]

However, in such a conventional vehicle hydraulic pressure supply device, although the pump discharge amount when the vehicle is stopped is smaller than when the vehicle is running and the horsepower consumption of the hydraulic pump is reduced, the viscosity of the hydraulic oil is reduced in a low temperature environment. Therefore, the discharge flow rate is significantly reduced compared to the pump discharge rate after warming up, and as a result, even the steady consumption flow rate required by the pressure control valve is supplied when the vehicle is stopped or running at extremely low speeds. Therefore, there is an unsolved problem that the line pressure is reduced and it becomes difficult to maintain the vehicle height when the vehicle is stopped or running at an extremely low speed, and in some cases, the muffler or bumper may be damaged.

The present invention has been made by paying attention to such a conventional unsolved problem, and reliably secures a necessary flow rate for maintaining the vehicle height even when the vehicle is stopped in a low temperature environment or when traveling at an extremely low speed. The task to be solved is to do so.

[Means for solving the problem]

In order to solve the above problems, a vehicle fluid pressure supply device of the present invention includes a fluid pressure cylinder provided between a vehicle body and wheels, and a fluid pressure control valve that controls the pressure of the fluid pressure cylinder. A fluid pressure pump connected to a rotary drive source of the vehicle and having a variable discharge amount, a fluid temperature determination means for determining whether or not the temperature of the working fluid is a low temperature below a predetermined temperature, and the vehicle is stopped. State or a very low speed running state, a running state determining means for determining whether or not the running state determining means determines whether the vehicle is in a stopped state or a very low speed running state, the fluid pressure pump discharges the discharge flow rate more than in normal running. And a discharge flow rate control means for decreasing the discharge flow rate of the fluid pressure pump regardless of the determination result of the running state determination means when the fluid temperature determination means determines a low temperature state. The has become the other to a large flow rate.

[Action]

When the fluid temperature determination means determines the low temperature state, the discharge amount control means forcibly increases the discharge flow rate from the fluid pressure pump to a large flow rate regardless of the determination result of the traveling state determination means. Therefore, even when the vehicle is stopped or running at an extremely low speed in a low temperature environment, the shortage of the discharge amount due to the low viscosity of the working fluid is eliminated, the steady consumption flow rate required by the control valve is reliably secured, and the fluid pressure Cylinder operating pressure does not decrease. Therefore, the vehicle height is also reliably maintained at the predetermined value.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

In FIG. 1, 2 is a vehicle body, 4 is a wheel, 6 is an active suspension in which the actuator is interposed between the vehicle body 2 and the wheel 4, and 8 is a hydraulic pressure supply device (fluid pressure supply device) for the active suspension 6, respectively. Show.

The active suspension 8 includes a hydraulic cylinder 10 as an actuator, a pressure control valve 12 as a control valve, an attitude control circuit 16, and an acceleration sensor 18.

The hydraulic cylinder 10 has a cylinder tube 10a attached to the vehicle body 2 side and a piston rod 10b attached to the wheel 4 side, and a pressure chamber L is separated by a piston 10c in the cylinder tube 10a.

The pressure control valve 12 includes a valve housing, a spool slidably arranged in an insertion hole in the valve housing, and a proportional solenoid that presses one end side of the spool according to a command value I. It has a well-known structure including a spool valve (for example, refer to the above-mentioned JP-A-63-251313). The valve housing also has a supply port that corresponds to the spool.
12c, an output port 12o, and a return port 12r are formed, and a hydraulic supply device 8 is connected to the supply port and the return port 12r, and the output port 12o is connected to the hydraulic cylinder 1 via a pipe 20.
It communicates with the pressure chamber L of 0. The output of the output port 12o is fed back to the other end of the spool in order to balance the thrust of the proportional solenoid.

The pressure control valve 12 can control the pressure output from the output port according to the command value I supplied from the attitude control circuit 16 to the proportional solenoid. That is, when the command value I is zero, a predetermined offset pressure is output, and when the command value I increases in the positive or negative direction, it changes with a predetermined proportional gain, and when the line pressure of the hydraulic pressure supply device 8 is reached, saturation occurs. To do. On the other hand, with the urging forces at both ends of the spool balanced,
When the pressure of the pressure chamber L of the hydraulic cylinder 10 fluctuates, the spool slightly moves to allow the working oil to flow between the hydraulic supply device and
Absorb the pressure fluctuation.

In the present embodiment, the acceleration sensor 18 is composed of a sensor that detects lateral, longitudinal, and vertical accelerations generated in the vehicle body 2, and outputs an electric signal G corresponding to the state quantities to the attitude control circuit 16. It is supposed to do. The attitude control circuit 16 performs a calculation such as multiplying the detection signal G by a predetermined gain, calculates a command value I that suppresses the roll and pitch of the vehicle body, and attenuates vertical vibration and supplies the command value I to the pressure control valve 12. To do.

A coil spring 22 having a relatively low spring constant for supporting a static load of the vehicle body 2 is provided between the vehicle body 2 and the wheels 4. Further, the cylinder chamber L is connected to the accumulator 26 via the throttle valve 24, so that a damping force is generated with respect to a high-frequency vibration input in the unsprung resonance region from the road surface side.

On the other hand, the hydraulic pressure supply device 8 has a tank 30 for storing hydraulic oil, and a hydraulic pump 34 having a suction side connected to the tank 30 by a pipe 32. The hydraulic pump 34 is a variable discharge hydraulic pump that is connected to an output shaft 36A of an engine 36 that serves as a rotary drive source of the vehicle, and is specifically a plunger type pump having a plurality of cylinders. Then, every other three cylinders constitute a first hydraulic pump 34A having a relatively large discharge amount per one rotation, and the other three cylinders provide a discharge amount per one rotation. A small second hydraulic pump 34B is configured.

Here, the discharge amount of the first hydraulic pump 34A is determined based on the internal leak flow rate Q ₀ of the control valve necessary for the vehicle body posture change described later, and the discharge amount of the second hydraulic pump 34B is the maximum required flow rate Q _MAX. The discharge flow rate characteristic with respect to the engine speed N is as shown in FIG. In other words, during normal traveling with a high consumption flow rate, the combined discharge amount of the first and second hydraulic pumps 34A, 34B is sufficient, and when the vehicle has a low consumption flow rate or is running at an extremely low speed, the discharge rate of the first hydraulic pump 34A alone. It is supposed to be covered by. Note that N ₀
Is the idle speed.

The discharge port of the first hydraulic pump 34A is the first supply side pipeline 3
It is connected to the supply port 12s of the pressure control valve 12 via 8a, and the return port 12r of the control valve 12 is connected to the tank 30 via the drain side conduit 39. Further, the discharge port of the second hydraulic pump 34B is a spring offset type electromagnetic directional control valve at the position of 3 ports and 2 positions via the second supply side conduit 38b.
It is connected to 40 input ports 40a.

The electromagnetic directional control valve 40 connects the input port 40a and the first output port 40b to each other and connects the second output port when the switching signal CS supplied from the discharge amount control circuit 42 to the solenoid is "ON". When 40c is blocked (hereinafter referred to as "switch position for large flow rate") and the switching signal CS is "OFF",
On the contrary, a switching mode is adopted in which the input port 40a and the second output port 40c are communicated with each other and the first output port 40b is closed (hereinafter, referred to as "small flow rate switching position"). The first output port 40b communicates with the first supply-side conduit 38a via the check valve 44, and the second output port 40c communicates with the conduit.
It communicates with the tank 30 via 46.

In addition, a relatively large-capacity accumulator 46 filled with high-pressure gas is connected to the first supply-side conduit 38a for accumulating and absorbing pulsation, and the first supply-side conduit 38a (connection of the accumulator 46) is connected. A relief valve 48 for setting the line pressure to a predetermined value is connected between the upstream side of the point) and the drain side conduit 39. The accumulator 4 is installed in the second supply side pipe line 38b.
9 is connected, which functions to absorb the rotational shock to the engine when the electromagnetic directional control valve 40 is switched.

Further, the present hydraulic pressure supply device 8 is provided at a predetermined position of the vehicle body 2,
A vehicle speed sensor 50 for detecting a signal V corresponding to the vehicle speed is provided. The vehicle speed sensor 50 is, for example, a pulse detector for magnetically and optically detecting the rotation speed on the output side of the transmission. On the other hand, an oil temperature sensor 52 that detects a signal T corresponding to the temperature of the hydraulic oil is provided at a position in the tank 30 where the hydraulic oil is immersed.
The oil temperature sensor 52 is, for example, a thermistor having a negative temperature coefficient of resistance shown in FIG.

On the other hand, the discharge amount control circuit 42, as shown in FIG.
A comparator 70 for the input oil temperature detection signal R, a comparator 72 for the input vehicle speed detection signal V, an OR circuit 74 that operates according to the comparison result of both comparators 70, 72, and this OR circuit.
And a drive circuit 76 for amplifying the output signal of 74 and outputting the switching signal CS to the electromagnetic directional control valve 40.

Specifically, the comparator 70 compares the oil temperature detection signal R with the reference value R ₀ corresponding to the predetermined temperature T ₀ , and when R ≧ R ₀ , the logical value “1”, when R <R ₀ A judgment signal of logical value “0” is output to the OR circuit 74. Further, the comparator 72 compares the vehicle speed detection signal V with a reference value V ₀ corresponding to a predetermined vehicle speed, and when V ≧ V ₀ , a logical value “1”, and when V <V ₀ , a logical value “0”. The judgment signal of is output to the OR circuit 74. Here, the reference value R ₀ is set to a value capable of discriminating that it is in a low temperature environment through experiments, etc., and the reference value V ₀ is set to a value capable of discriminating during extremely low speed traveling (for example, 2 km / h or less) or when stopped. Has been done. On the other hand, the OR circuit 74 has the logical value "1" when either of the two inputs has the logical value "1".
The signal of is output to the drive circuit 76.

In the above configuration, the oil temperature sensor 52 and the first comparator 70 constitute fluid temperature determination means, the vehicle speed sensor 50 and the second comparator 72 constitute traveling state determination means, and the OR circuit 7
4, the drive circuit 76, and the electromagnetic directional control valve 40 constitute discharge amount control means.

 Next, the overall operation of the above embodiment will be described.

Now, when the engine is turned on with the ignition switch turned on from the parking state, the hydraulic pump
34 also rotates, and the amount of hydraulic oil corresponding to the number of rotations is discharged as shown in FIG.

At this time, if it is assumed that the parking environment temperature is high and the temperature of the hydraulic oil exceeds the preset reference value T ₀ ,
The detection signal R of the oil temperature sensor 52 is R <R ₀ , and the vehicle speed sensor 5
The detection signal V of ₀ is V <V ₀ . Therefore, the comparison results of both comparators 70 and 72 of the discharge amount control circuit 42 are both logical value "0".
And the output of the OR circuit 74 is the logical value “0”,
The switching signal CS is turned off. Therefore, the electromagnetic directional control valve
As described above, 40 takes the "switching position at the time of small flow rate", whereby the second hydraulic pump 34B communicates with the tank via the pipes 38b and 46, so no load operation is performed, and the line pressure to the pressure control valve 12 is reduced. It is covered by the discharge flow rate of the first hydraulic pump 34A.

In other words, in such a stopped state, there is almost no posture variation and vibration input from the road surface, so the consumption flow rate is small, and the discharge flow rate of the first hydraulic pump 34A is sufficient for the engine 36.
There is an energy-saving effect that the load of is reduced and the horsepower consumption is reduced.

It is assumed that acceleration is started from the above-mentioned stopped state. However, while the vehicle speed is in the extremely low speed running state below the reference value, V <
Since V ₀ is maintained, the switching signal CS is kept off, and the hydraulic pressure co-supply by the independent operation of the first hydraulic pump 34A described above is continued. That is, in this extremely low speed traveling state, the posture fluctuation is small and the flow rate consumed is still small. Therefore, the small discharge amount by the first hydraulic pump 34A is sufficient to suppress the horsepower consumption.

When the vehicle further accelerates and enters the start state, the vehicle speed exceeds the reference value, and therefore the detection signal V ≧ V ₀ , the determination signal of the second comparator 72 becomes the logical value “1”, and the OR circuit 74 Has a logical value "1", and the switching signal CS is turned on. As a result, the electromagnetic directional control valve 40 takes the "large flow rate switching position" described above, and the discharge flow rate is increased by the amount due to the second hydraulic pump 34B.

On the other hand, when the above-mentioned start is started, a backward acceleration is generated and a scut phenomenon in which the rear part of the vehicle body sinks tends to occur. Therefore, the acceleration sensor 18 detects a signal G corresponding to the acceleration, and the posture control circuit 16 outputs a command value I for suppressing the scat to each pressure control 12, so that the pressure control valve
Each of 12 controls the operating pressure of each hydraulic cylinder 10 according to the command value I. That is, in the hydraulic cylinder 10 on the rear wheel side, a large amount of hydraulic oil is made to flow from the hydraulic pressure supply device 8 via the pressure control valve 12 to increase the pressure in the pressure chamber L to generate a force against the scut, and the scut To improve riding comfort.

In this way, when the vehicle body attitude control is started after exiting the extremely low-speed running state and a large amount of hydraulic oil needs to be consumed,
Since both hydraulic pumps 34A and 34B are operating as described above, there is no shortage of the amount of oil, and reliable posture control can be performed.

Furthermore, after reaching straight traveling at a constant speed, a large amount of flow rate is consumed even when turning, for example.However, even in such a case, the switching signal CS for the electromagnetic directional control valve 40 is kept on. Therefore, sufficient hydraulic oil is guaranteed by both hydraulic pumps 34A and 34B.

On the other hand, when the parking environment is a snowfall area, the temperature of the hydraulic oil is in a low temperature state below a preset reference value T ₀ ,
It is assumed that the ignition switch is turned on and the engine is rotated from this low temperature state.

Immediately after this engine rotation, the detection signal V of the vehicle speed sensor 50 is V <V ₀ , but the detection signal R of the oil temperature sensor 52 is R ≧
Since it becomes R ₀ , as described above, the output of the OR circuit 74 becomes the logical value “1”. As a result, the switching signal CS is turned on, and the switching valve 40 takes the "switching position at the time of large flow rate", so that the combined discharge amount of both hydraulic pumps 34A, 34B forms the line pressure regardless of the stopped state. Hold the vehicle height. That is,
Even if viscosity is high due to low temperature of hydraulic oil, both hydraulic pumps 34A and 34B are forcibly and automatically operated to increase the discharge flow rate of hydraulic pump 34. It is possible to solve the situation that the discharge amount becomes insufficient only by the first hydraulic pump 34A and it becomes difficult to maintain the vehicle height at the time of stop.

Then, even after the above-mentioned stop state is changed to the start state, the operating states of both hydraulic pumps 34A and 34B are continuously continued. Therefore, a sufficient vehicle height is ensured even when the vehicle is running at an extremely low speed when starting to start, and damage to the muffler and the like can be reliably prevented. In addition, during normal traveling, a discharge amount commensurate with the required large flow rate is secured, and stable attitude control is performed as described above.

By the way, when the running state is changed to the stopped state, when the oil temperature at that time is higher than the predetermined value T ₀ ,
Return to the independent operation of the first hydraulic pump 34A to reduce the horsepower consumption. However, when the oil temperature is lower than the predetermined value T ₀ ,
The first and second hydraulic pumps 34A, 34B are activated, and the vehicle height value is reliably maintained. Also, first, even if the oil temperature is higher than the predetermined value T _0, by gradually from the middle drop below a predetermined value T _0, automatically both pumps 34A, becomes 34B operating, decrease in vehicle height Prevent from happening.

Although the thermistor is used as the oil temperature sensor 52 in the above embodiment, the present invention is not limited to this, and a temperature switch such as a bimetal may be used. Further, instead of the vehicle speed sensor 50, the vehicle body acceleration may be used as shown in the third embodiment described in Japanese Patent Laid-Open No. 63-251313.

On the other hand, the variable discharge hydraulic pump according to the present invention does not necessarily have to have the above-described two-stage switching structure.
Pump, second pump, first + second pump three-stage switching (However, in this case, the discharge amount of the second pump is the first
It is also possible to reduce the total horsepower consumption by controlling the total discharge rate more precisely according to the oil temperature by installing a continuously variable flow rate switching pump. Further, by increasing the number of switching stages in such a manner, when the operating oil reaches a low temperature environment during traveling, the discharge amount can be controlled in the increasing direction to achieve stable discharge amount. A means to measure the warm-up time by performing idling operation in the low temperature state of is provided, and when this measured value reaches a predetermined value, it is considered that the temperature of the hydraulic oil has risen sufficiently and the idling operation and the There is also an application example in which the increase in the discharge amount during low-speed traveling can be stopped and the reduction in horsepower consumption due to the low discharge amount can be promoted.

Furthermore, although a case has been described with the above embodiment where hydraulic oil is used as the working fluid, the present invention is not necessarily limited to this, and any fluid having a low compression rate can be applied.

〔The invention's effect〕

As described above, in the present invention, when the predetermined low temperature state is determined, the discharge flow rate of the fluid pressure pump is forcibly made to be a large flow rate regardless of the determination of the traveling state determination means. At times, when the viscosity of the working fluid decreases and the amount of discharge becomes insufficient, the amount of discharge increases automatically, so the minimum required flow rate can be secured without being affected by temperature, and the vehicle height can be kept constant. In addition, the suspension function that uses the fluid pressure cylinder as an actuator is not impaired, while the increase function at low temperature is used to minimize the discharge amount of the fluid pressure pump during warming up and reduce horsepower consumption. The effect is that it can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a graph showing a discharge flow rate characteristic with respect to a rotational speed of a hydraulic pump, and FIG. 3 is a graph showing a resistance value characteristic of a thermistor forming an oil temperature sensor. FIG. 4 is a block diagram showing a discharge amount control circuit. In the figure, 2 is a vehicle body, 4 is wheels, 6 is an active suspension, 8 is a hydraulic pressure supply device (fluid pressure supply device), 10 is a hydraulic cylinder (fluid pressure cylinder), 12 is a pressure control valve (control valve), 36 Is a hydraulic pump (fluid pressure pump), 36 is an engine as a rotary drive source, 40 is an electromagnetic direction switching valve, 42 is a discharge amount control circuit, 50 is a vehicle speed sensor, and 52 is an oil temperature sensor.

Claims (1)

(57) [Claims] 1. A fluid pressure supply device for a vehicle, which supplies a fluid pressure to a fluid pressure cylinder interposed between a vehicle body and a wheel through a control valve for controlling the pressure of the fluid pressure cylinder. A variable discharge fluid pressure pump connected to a rotary drive source, a fluid temperature determination means for determining whether or not the temperature of the working fluid is a low temperature below a predetermined temperature, and a vehicle in a stopped state or a very low speed running state. A traveling state determining means for determining whether or not, and a discharge flow rate controlling means for lowering the discharge flow rate of the fluid pressure pump when the traveling state determining means determines a stopped state or an extremely low speed traveling state as compared with during normal traveling, When the fluid temperature determination means determines a low temperature state, the discharge flow rate control means sets the discharge flow rate of the fluid pressure pump to a large flow rate regardless of the determination result of the traveling state determination means. A fluid pressure supply device for a vehicle.