JP2000073941A - Electric pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric pump capable of restricting reduction of magnetostriction quantity caused by temperature fall of a super-magnetostrictive element by keeping temperature of the super-magnetostrictive element as a drive source for a piston to discharge fluid by reciprocating action at a prescribed value or more. SOLUTION: In an electric pump 1 using a super-magnetostrictive element 9 which is elongated by application of a magnetic field as a drive source for a piston 5 to discharge fluid by reciprocating action, it is provided with a temperature sensor 30 to detect temperature of the super-magnetostrictive element 9, a heating means H to heat the super-magnetostrictive element 9, and a control device 33 to actuate the heating means H based on an output of the temperature sensor 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric pump using a giant magnetostrictive element which expands by applying a magnetic field as a driving source of a piston for discharging a fluid by reciprocating operation.

[0002]

2. Description of the Related Art In recent years, brake systems for vehicles have been actively provided with intelligent brake functions such as an anti-lock brake system and a traction control system. With the advance of such intelligence, it has become indispensable to electrically pump and reduce the size of a pump incorporated in a brake device as a hydraulic pressure generation source.

[0003] From such a background, a pump unit that discharges a fluid by reciprocating a piston housed in a housing, and a piston that uses a solid element that can electrically control expansion and contraction as a driving source for reciprocating the piston. An electric pump including a driving unit has been proposed. In this case, piezoelectric ceramics and giant magnetostrictive elements have been proposed as solid-state elements whose expansion and contraction operations can be electrically controlled (JP-A-7-16).
No. 7327, JP-A-8-334082, etc.).

However, a high voltage is required for the expansion and contraction operation of the piezoelectric ceramics, and there is a problem that a power supply and a control circuit provided for controlling the expansion and contraction operation of the piezoelectric ceramics increase in size. On the other hand, the expansion and contraction operation of the giant magnetostrictive element is performed by applying a magnetic field to the giant magnetostrictive element from a coil arranged around the giant magnetostrictive element. The power supply and control circuit provided for controlling the expansion and contraction of the device can be reduced in size.
Therefore, it is more advantageous to use a giant magnetostrictive element as a drive source of an electric pump of a vehicle brake device in which weight reduction and downsizing are important issues.

[0005]

However, the giant magnetostrictive element has a magnetostriction caused by expansion and contraction generated under a predetermined applied magnetic field.
As shown by the characteristic line f in FIG. 2, when the element temperature is 0 ° C. or higher, the temperature is stable. However, when the element temperature falls to 0 ° C. or lower, the temperature rapidly decreases as the temperature decreases. Therefore, when a giant magnetostrictive element is used as a drive source of an electric pump of a vehicle brake device, sufficient pump performance can be obtained in a cold region due to a decrease in magnetostriction due to a decrease in element temperature. There was a risk of disappearing. The present invention has been made in view of the above circumstances, in an electric pump using a giant magnetostrictive element, by maintaining the temperature of the giant magnetostrictive element at a specified value or more, caused by the temperature drop of the giant magnetostrictive element It is an object of the present invention to provide an electric pump capable of suppressing a decrease in magnetostriction and maintaining stable pump performance even when used in a cold region or the like.

[0006]

An electric pump according to the present invention for achieving the above object uses a giant magnetostrictive element which expands by applying a magnetic field as a driving source of a piston for discharging a fluid by reciprocating operation. Electric pump
A temperature sensor for detecting the temperature of the giant magnetostrictive element, a heating means for heating the giant magnetostrictive element, and operating the heating means based on an output of the temperature sensor to raise the temperature of the giant magnetostrictive element to a specified value or more. And a control device for holding.

[0007] According to the above configuration, when the temperature of the giant magnetostrictive element drops to a specified value in an environment where the electric pump is used, for example, in a cold region or the like, the control device operates the heating means to cause the giant magnetostrictive element to operate. Is kept above the specified value. Therefore, if the reference temperature for operating the heating means is previously set to an appropriate value, the temperature of the giant magnetostrictive element is always maintained at an appropriate value of 0 ° C. or more at which the magnetostriction amount is stabilized, and the temperature of the giant magnetostrictive element is maintained. The decrease in the magnetostriction caused by the decrease can be suppressed.

When the output of the temperature sensor falls below a specified value, the control device operates as a heating means by supplying a current to generate heat in a coil provided for applying a magnetic field to the giant magnetostrictive element. It is preferable to adopt a configuration in which these are performed.

In this case, the coil provided for applying a magnetic field to the giant magnetostrictive element also serves as a heating means for heating the giant magnetostrictive element to a specified temperature or higher when used in a low-temperature environment. There is no need to provide a dedicated heating means for heating.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the electric pump according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing one embodiment of an electric pump according to the present invention. The electric pump 1 is incorporated as a hydraulic pressure generating source into a hydraulic brake device for a vehicle. The electric pump 1 is a solid-state element that can electrically control a piston 5 housed in a bottomed cylindrical housing 3 by contacting the piston 5. By reciprocating the giant magnetostrictive element 9
It comprises a pump section 7 for discharging a fluid.

The pump portion 7 defines a liquid chamber 12 between the piston 5 and the end wall 4 closing the open end of the housing 3, and a discharge port 12 a formed through the end wall 4,
Check valves 14 and 15 are provided at the inlet 12b, respectively. The check valve 14 of the discharge port 12a is
The flow path is opened during the discharge stroke of the piston 5, and the flow path is closed during the suction stroke. On the other hand, the check valve 15 of the suction port 12b opens the flow path during the suction stroke, and closes the flow path during the discharge stroke. A seal ring 16 is provided at a contact portion between the end wall member 4 and the housing 3. Further, a piston seal 17 for sealing between the housing 3 and the piston 5 is provided on the inner peripheral surface of the housing 3 on which the piston 5 slides. The piston 5 is urged by a return spring 19 disposed in the liquid chamber 12 in a direction away from the end wall member 4 (that is, in a direction in which it contacts the giant magnetostrictive element 9 which is a solid element).

The electric pump 1 includes the above-described giant magnetostrictive element 9 having a characteristic of extending when a magnetic field is further applied thereto, and a coil 2 for applying a magnetic field to the giant magnetostrictive element 9 when a current is applied.
0, a temperature sensor 30 that is closely attached to the periphery of the giant magnetostrictive element 9 and detects the temperature of the giant magnetostrictive element 9, and a giant magnetostrictive element 9 so that the expansion and contraction of the giant magnetostrictive element 9 is transmitted to the piston 5.
3 housing and holding coil and coil 20 inside the cylinder
And a power source 22 which is a source of a current applied to the coil 20.
And a coil 20 interposed between the power supply 22 and the coil 20.
Control device 33 for controlling the expansion and contraction operation of the giant magnetostrictive element 9 by controlling the current applied to the device, and unloading which operates based on a control signal from the control device 33 to release the discharge pressure of the pump section 7 to the reservoir. Means 35 are provided.

The housing 3 is slidably accommodated in the cylinder so as to be continuous with the accommodating area of the giant magnetostrictive element 9 and the coil 20 so that the expansion / contraction operation of the giant magnetostrictive element 9 is transmitted to the piston 5. At the same time, it functions as a yoke constituting a closed magnetic circuit that covers these areas. Further, the return spring 19 of the piston 5 also functions as a preload spring for improving the elongating operation of the giant magnetostrictive element 9.

The control device 33 includes a pump operation control circuit (not shown) that causes the giant magnetostrictive element 9 to expand and contract at a predetermined cycle by applying a current to the coil 20 in order to properly reciprocate the piston 5 during a braking operation or the like. And an element temperature control circuit (not shown) for starting current application to the coil 20 and heating the coil 20 so that the giant magnetostrictive element 9 is heated when the detected value of the temperature sensor 30 decreases to a specified value. ing.

The amount of expansion and contraction of the giant magnetostrictive element 9 is proportional to the strength of the magnetic field applied from the coil 20. Therefore, the piston 5
Is performed by raising the magnetic field generated by the coil 20 from an initial value to a predetermined value and causing the giant magnetostrictive element 9 to perform a predetermined elongation operation.
By lowering the magnetic field generated by 0 from a predetermined value to an initial value,
This is performed by causing the giant magnetostrictive element 9 to perform a predetermined contraction operation.

The pump operation control circuit of the control device 33 controls the coil 2 so that the magnetic field generated by the coil 20 rises from an initial value to a predetermined value during the discharge stroke by the piston 5.
The current applied to the coil 20 is controlled such that the magnetic field generated by the coil 20 drops from a predetermined value to an initial value during the suction stroke. The pump operation control circuit realizes such repetition of the discharge step and the suction step by setting the current supplied to the coil 20 to an alternating current having a predetermined cycle.

The element temperature control circuit of the control device 33 is adapted to maintain the temperature of the giant magnetostrictive element 9 at a specified value or more when the expansion and contraction characteristics of the giant magnetostrictive element 9 decrease due to use in a low-temperature environment. Then, the giant magnetostrictive element 9 is heated based on the value detected by the temperature sensor 30. In the present embodiment, a weak alternating current is applied to the coil 20 to cause the coil 20 to generate heat, and the heat of the coil 20 keeps the temperature of the giant magnetostrictive element 9 at a specified value. That is, in the case of the present embodiment, the coil 20 provided for applying a magnetic field to the giant magnetostrictive element 9 is also used as the heating means H of the giant magnetostrictive element 9.

In the case of the present embodiment, the unloading means 35 includes a suction-side flow path 41 that connects between a reservoir (not shown) and the suction-side check valve 15, and a load (not shown).
A two-position switching type solenoid valve provided in a bypass passage 43 for communicating a discharge side flow passage 42 communicating between a discharge side check valve 14 and a wheel cylinder of a hydraulic brake device. During the heating operation, the bypass passage 43 is opened to make the suction side flow passage 41 and the discharge side flow passage 42 communicate with each other. When the pump is operated by the pump operation control circuit, the bypass passage 43 is closed to close the suction side flow passage 41 and the discharge side flow passage. The channel 42 is brought into a non-communication state.

In a state where the bypass passage 43 is opened and the suction side flow passage 41 and the discharge side flow passage 42 communicate with each other, the discharge port of the discharge side check valve 14 is connected to a reservoir (not shown) via the suction side flow passage 41. Communicating. In the electric pump 1 having the above configuration, when a weak alternating current for heating is passed through the coil 20,
A magnetic field is applied from the coil 20 to the giant magnetostrictive element 9, whereby the pump unit 7 is driven to generate a small amount of hydraulic pressure and discharge even though it is small. However, if the discharge port of the discharge-side check valve 14 is in communication with the reservoir by the unloading means 35, the discharge pressure from the pump unit 7 escapes to the reservoir, so that the inconvenience due to the discharge pressure from the pump unit 7 does not occur. .

If the unloading means 35 is provided as described above, the pump unit 7 is substantially turned off when an alternating current is supplied to the coil 20 for the purpose of heating the giant magnetostrictive element 9 as in the present embodiment. And the giant magnetostrictive element 9 can be heated. However, in order to heat the giant magnetostrictive element 9, a direct current may be applied to the coil 20 instead of the alternating current. In this case, the unloading means can be omitted. Alternatively, the giant magnetostrictive element 9 may be configured to perform a pump operation while maintaining the temperature of the giant magnetostrictive element 9 at a specified value by heating the temperature of the giant magnetostrictive element 9 as an alternating current obtained by superimposing an alternating current on a direct current.

According to the electric pump 1 described above, the operating environment of the electric pump 1 is, for example, in a cold region or the like, and the giant magnetostrictive element 9 is used.
Is decreased to the specified value, the control device 33 operates the coil 20 as a heating means to maintain the temperature of the giant magnetostrictive element 9 at or above the specified value. Therefore, if the reference temperature for operating the coil 20 as the heating means is set to an appropriate value in advance, the temperature of the giant magnetostrictive element 9 is reduced to 0 ° C. at which the magnetostriction amount is stabilized.
By maintaining the above appropriate value at all times, it is possible to suppress a decrease in the magnetostriction caused by a decrease in the temperature of the giant magnetostrictive element 9, and to maintain stable pump performance even when used in a cold region or the like.

In addition, in the electric pump 1 of the present embodiment, the coil 20 provided for applying a magnetic field to the giant magnetostrictive element 9 has a heating function of heating the giant magnetostrictive element 9 to a specified temperature or higher when used in a low-temperature environment. Since it is not necessary to equip the heating means for heating the giant magnetostrictive element 9 with a dedicated heating means, it is possible to prevent an increase in the number of components and to reduce the size and cost of the apparatus.

In the above embodiment, the giant magnetostrictive element 9
Although the coil 20 equipped to apply a magnetic field to the coil was also used as a heating means for heating the giant magnetostrictive element 9, the coil 20 was provided separately from the coil 20, such as a heater wire for heating the giant magnetostrictive element 9. A heating means may be provided.

[0024]

According to the electric pump of the present invention, when the temperature of the giant magnetostrictive element is reduced to a specified value in a use environment, for example, in a cold region, the control device activates the heating means to activate the giant magnetostrictive element. Keep the temperature above the specified value. Therefore, if the reference temperature for operating the heating means is previously set to an appropriate value, the temperature of the giant magnetostrictive element is always maintained at an appropriate value of 0 ° C. or more at which the magnetostriction amount is stabilized, and the temperature of the giant magnetostrictive element is maintained. It is possible to suppress the characteristic deterioration due to the decrease, and to maintain stable pump performance even when used in a cold region or the like. Also,
As described in claim 2, when the output of the temperature sensor falls below a specified value, the control device operates as a heating means by supplying a current to generate heat in a coil provided for applying a magnetic field to the giant magnetostrictive element. In the case of the configuration, the coil provided for applying a magnetic field to the giant magnetostrictive element is also used as a heating means for heating the giant magnetostrictive element to a specified temperature or more when used in a low-temperature environment, and the heating of the giant magnetostrictive element is performed. Therefore, it is not necessary to provide a dedicated heating means, so that it is possible to prevent an increase in the number of components and to reduce the size and cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric pump according to an embodiment of the present invention.

FIG. 2 is a characteristic correlation diagram between the magnetostriction amount of the giant magnetostrictive element and the element temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric pump 3 Housing 4 End wall material 7 Pump part 9 Giant magnetostrictive element 12 Liquid chamber 19 Return spring 20 Coil (heating means) 22 Power supply 33 Control device 35 Unloading means

Claims (2)

[Claims] 1. An electric pump using a giant magnetostrictive element that expands by applying a magnetic field as a drive source of a piston that discharges a fluid by reciprocating operation, comprising: a temperature sensor for detecting a temperature of the giant magnetostrictive element; A motor that heats the giant magnetostrictive element, and a control device that operates the heating means based on an output of the temperature sensor to maintain the temperature of the giant magnetostrictive element at or above a specified value. Type pump. 2. The control device according to claim 1, wherein when the output of the temperature sensor falls below a predetermined value, the control device operates as a heating unit by supplying a current to generate heat in a coil provided for applying a magnetic field to the giant magnetostrictive element. The electric pump according to claim 1, wherein the electric pump is driven.