JPH0932720A - Piezo drive type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a pump drive part without hurting a sending out ability by providing an excitation means consisting of a piezo element joined to a spring and connecting a drive circuit by which the resonance drive signal of a spring mass system can be outputted. SOLUTION: When an electric signal is generated by a frequency matched with a peculiar frequency of a spring 1 - a piston 3 from a oscilator 14, the electric signal is inputted to a piezo element 2 after the amplification by an amplifier 13 through a signal line 12. As the piezo element 2 exchanges an inputted electric signal to a mechanical vibration, the piezo element 2 is vibrated by the electric signal from the osilator 14 and the vibration is transmitted to the spring 1 - the piston 3. Thereby, the piston 3 generates a resonance phenomenon and carries out a reciprocating motion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezo drive type pump, and more particularly to a pump suitable for use as a hydraulic pump for vehicles and as an actuator for a rear-end collision prevention system.

[0002]

2. Description of the Related Art Conventionally, as a mechanical pump, a vane pump, a gear pump, a plunger pump, or the like has been representatively used as a hydraulic pump for a vehicle or the like, and there is a pump using a piezo element as a drive unit. To do. In a hydraulic circuit using these pumps, first, a liquid is introduced from a reservoir tank containing a liquid serving as a medium to the pump inlet side, and the pump is driven to deliver the pressurized liquid from the pump outlet side. Various devices are connected to the pump outlet side, and the various devices operate by feeding the pressurized liquid. There is also a method in which an accumulator for accumulating the pressurized liquid is attached to the pump outlet side, and the liquid accumulated in the accumulator is sent to various devices to perform the operation.

[0003]

By the way, it is necessary to accumulate a sufficient amount of oil in the accumulator in order to move various equipments of the vehicle, and for this reason, improvement of the pumping capacity of the pump is required.

However, in the conventional pump, not only the volume of the pump but also the size of the pump drive section must be increased in order to improve the delivery capacity. As a result, the occupancy rate in the vehicle increases, which is a constraint in designing. In addition, there is a problem that the weight of the vehicle is inevitable because the weight of the pump increases due to the size increase of the pump itself.

The present invention has been made in view of the above points, and an object of the present invention is to provide a piezo drive type pump having means for reducing the size of the pump drive section without impairing the pumping ability of the pump. .

[0006]

A spring-mass system including a piston and a pair of springs supporting both ends of the piston is provided in a pump housing, and the pump housing has an inlet port opened to a pump chamber defined by the piston. And an outlet port are formed, and at the one end of the pump housing, a vibrating means formed of a piezo element joined to the spring is provided, and a resonance drive signal of the spring mass system can be output to the vibrating means. The drive circuit is connected.

[0007]

In the piezo drive type pump of the present invention constructed as described above, the drive circuit sends a drive signal to the piezo element so that the piston provided in the pump housing and the pair of springs supporting both ends thereof cause resonance drive. input. The piezo element converts the drive signal received from the drive circuit into vibration and transmits the vibration to the spring-piston that serves as a spring-mass system. Due to this vibration, the spring-piston makes a reciprocating motion and the volume of the partitioned pump chamber is varied to act as a pump. By operating the pump by utilizing the resonance drive as described above, the pump drive unit can be downsized without impairing the pumping capability of the pump. It is also possible to prevent the weight of the pump from increasing as the pump driving unit becomes smaller.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the piezo-driven pump according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a structural explanatory view of a piezo drive type pump according to an embodiment. As shown in this figure, the piezo drive type pump of the embodiment is provided with a cylinder 7 having a circular cross section in the pump housing, and the bottom surface of the left side of the cylinder 7 generates vibration in response to an electric signal. The piezo element 2 is attached. From the piezo element 2, the signal line 12
Is drawn out of the pump housing, and the signal line 12 is connected to the oscillator 14 via the amplifier 13. The oscillating device 14 is capable of generating a frequency signal that matches the natural frequency of the spring 1-piston 3 inside the cylinder 7, which is a model of a spring-mass system described later. A cylinder-shaped piston 3 is arranged inside the cylinder 7, and the inside of the cylinder 7 is divided into two pump chambers 6 by the piston 3. Each of the two pump chambers 6 is provided with an inlet port 8 and an outlet port 9, and the inlet port 8 is equipped with a one-way valve 4 so that only liquid can be introduced into the pump chamber 6 from the outside. Similarly, the port 9 is also provided with the one-way valve 4 so that only the liquid can be delivered from the pump chamber 6. The piston 3 can reciprocate inside the cylinder 7. A spring 1 is attached to the right side of the piston 3 so as to connect the right bottom surface of the piston 3 and the right bottom surface of the cylinder 7. A spring 1 similar to the spring 1 provided on the right side of the piston 3 is attached to the left side of the piston 3 so as to connect the left bottom surface of the piston 3 and the piezo element 2 attached to the left bottom surface of the cylinder 7. . In this state, the piston 3 is balanced by the pair of left and right springs 1, and the two pump chambers 6 partitioned by the piston 3 have the same volume.

In the above-mentioned state, the spring 1 is released from the oscillator 14.
-When an electric signal is generated at a frequency that matches the natural frequency of the piston 3, the electric signal passes through the signal line 12, is amplified by the amplifier 13, and is input to the piezo element 2. Since the piezo element 2 replaces the input electric signal with mechanical vibration, the piezo element 2 vibrates by the electric signal from the oscillating device 14, and the vibration is transmitted to the spring 1-piston 3. As a result, the piston 3 causes a resonance phenomenon and reciprocates.

During the reciprocating movement of the piston 3, for example, when the piston 3 moves to the right, the volume of the pump chamber 6L increases as the piston 3 moves, and the increased volume corresponds to the amount of liquid from the inlet port 8 through the pump chamber 6L. Flow into. When the piston 3 moves to the rightmost side, the volume of the pump chamber 6L becomes maximum. After that, the piston 3 starts moving to the left and the volume of the pump chamber 6L is reduced. Pump room 6 at this time
The liquid in L is discharged from the outlet port 9 as the pump chamber 6L is contracted.
And the volume of the pump chamber 6L becomes minimum when the piston 3 moves to the leftmost end. Since the pump chamber 6R is one side bisected by the piston 3, the pump chamber 6R is the liquid discharge side when the pump chamber 6L is the liquid suction side, and the pump chamber 6L is the liquid discharge side when the pump chamber 6L is the liquid discharge side. The chamber 6R is on the liquid suction side. For this reason, the pump chamber 6L and the pump chamber 6R perform operations opposite to each other, and the liquid is discharged from the pump chamber 6 twice during one reciprocation of the piston 3.

FIG. 2 shows an example in which the piezo drive type pump according to the above embodiment is used as an actuator of a rear-end collision prevention system for a vehicle.

The main braking circuit for braking the vehicle is
The master cylinder 15 is operated by the operation of the brake petal, and the brake fluid 19 supplied from the reservoir tank 18 is supplied.
However, braking is performed by operating the wheel cylinder 23 from the master cylinder 15 via the automatic brake actuator 21 and the brake pressure control valve 22. Also, brake pressure control valve 2
A sensor 24 and an electronic control unit 25 that receives a signal from the sensor 24 for performing an antilock action are connected to the device 2.

A subordinate brake circuit is provided in the vehicle in addition to the main brake circuit. A pump 27 is provided in the subordinate brake circuit. The pump 27 uses the piezo drive type pump described in FIG. Has been done. Pump 27
A reservoir tank 26 is connected to the inlet side of the, and an accumulator 28 is connected to the outlet side. The path on the accumulator 28 side is connected to the aforementioned automatic brake actuator 21 via the switching control valves 29 and 33. An electronic control unit 25 is connected to the switching control valves 29 and 33, and the electronic control unit 25 is operable by receiving a signal from an inter-vehicle distance sensor 30 attached to the outer edge of the vehicle.

In the embodiment configured as described above, when performing a normal braking operation, the master cylinder 15 is operated by the stepping operation of the brake petal 17, and the brake fluid 19 is sent to the wheel cylinder 23 for braking. . When the pedal force of the brake petal 17 is excessively large and acts on the wheel cylinder 23, the electronic control unit 25 opens and closes the brake pressure control valve 22 at an appropriate time by a signal from the sensor 24 to perform an antilock action.

Further, in the slave brake circuit, a pulse having a frequency at which the spring-piston resonates is input from an external device to a piezo element in the pump 27, and the piezo element converts the input electrical energy into mechanical vibration energy. By converting into, the inside of the pump 27 is operated. The pump 27 sucks the brake fluid 32 from the reservoir tank 26 and sends the brake fluid 32 to the accumulator 28. When the target pressure is applied to the accumulator 28, the pressure detector 31 installed in the circuit operates to stop the pump 27 and maintain a constant pressure in the circuit.

When an obstacle comes within a certain distance around the vehicle while the vehicle is moving in such a state,
In order to avoid a rear-end collision with an obstacle, the inter-vehicle distance sensor 30 operates, and the electronic control unit 25 receiving the signal from the inter-vehicle distance sensor 30 switches the switching control valve 29 from the closed state to the released state. By this operation, the brake fluid 32 flows into the automatic brake actuator 21 via the switching control valve 29 by the pressure from the accumulator 28.

When the brake fluid 32 flows into the automatic brake actuator 21, the path for transmitting normal brake pressure is cut off, and the wheels can be automatically braked.

When the switching control valve 29 is closed and the switching control valve 33 is opened, the hydraulic pressure is released and the automatic braking is released.

From this, for example, even when the driver does not notice the obstacle while driving the vehicle, the inter-vehicle distance sensor 30 catches the obstacle and automatically brakes the vehicle, so that an accident due to a rear-end collision can occur. It is possible to prevent it.

Further, the piezo drive type pump for generating the braking force for preventing the rear-end collision does not cause the pumping action by stacking a plurality of piezo elements which originally have a small displacement, but utilizes the resonance phenomenon, so that the mechanical system is used. The efficiency of can be improved. This makes it possible to reduce the size and weight of the pump drive unit,
It is suitable when a device such as a vehicle is required to be small and lightweight.

Further, the operation and stop of the piezo drive type pump can be repeated easily by changing the frequency of the signal from the oscillating device 14 to generate or suppress the mechanical resonance of the spring 1-piston 3. I can.

In the above embodiment, the piezo element 2 is mounted only on the left bottom surface of the cylinder 7, but the piezo element 2 is mounted on the left and right bottom surfaces of the cylinder 7 and the phases of the left and right piezo elements 2 are shifted by a half cycle. When the frequency signals are input, the spring 1-piston 3 is vibrated from both ends. Therefore, the time from when the pump is stopped to when the pump is operated is shortened, and the amplitude of the reciprocating motion of the piston 3 is increased. The advantage is that the delivery capacity is improved.

[0023]

As described above, according to the present invention,
By causing the spring-piston composed of the spring-mass system to resonantly drive and act as a pump, it is possible to reduce the size of the pump drive unit without impairing the delivery capability. Further, it is possible to prevent the weight of the pump from increasing as the pump driving unit becomes smaller.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a piezo drive type pump according to an embodiment.

FIG. 2 is an application example using a piezo drive type pump.

[Explanation of symbols]

 1 Spring 2 Piezo Element 3 Piston 4 One Way Valve 6 (6R, 6L) Pump Chamber 7 Cylinder 8 Inlet Port 9 Outlet Port 12 Signal Line 13 Amplifier 14 Oscillator 15 Master Cylinder 17 Brake Petal 18 Reservoir Tank 19 Brake Fluid 21 Automatic Brake Actuator 22 Brake Pressure Control Valve 23 Wheel Cylinder 24 Sensor 25 Electronic Control Device 26 Reservoir Tank 27 Pump 28 Accumulator 29, 33 Switching Control Valve 30 Inter-Vehicle Distance Sensor 31 Pressure Detector 32 Brake Fluid

Claims (1)

[Claims] 1. A spring-mass system comprising a piston and a pair of springs supporting both ends thereof is provided in a pump housing, and an inlet port and an outlet port opened in a pump chamber defined by the piston are provided in the pump housing. And a vibrating means formed of a piezo element joined to the spring is provided at one end of the pump housing, and a driving circuit capable of outputting a resonance drive signal of the spring mass system is provided to the vibrating means. Piezo-driven pump characterized by being connected.