JPH09317689A - Electrically driven air pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease rush current generated when a motor is started, by starting the motor at lower voltage than a predetermined voltage, and increasing voltage gradually up to the predetermined voltage after starting or increasing voltage within an optional time. SOLUTION: Impression of voltage to an electrically driven air pump 3 is controlled in a control unit 1, and driving voltage is supplied from a battery. When a predetermined voltage is applied to the electrically driven air pump 3, rush current is generated within a short time of about 50msec of a starting period and reaches more than several times of normal driving current, and the brush of a motor is terribly worn by this rush current. The consumption current of the motor is approximately proportioned to supply voltage, therefore, when supply voltage at the time of starting is lowered, for example, from 14V to 8V, rush current can be reduced to 8/14. Therefore, the motor is started by lower voltage than a predetermined voltage so that rush current is lowered, and after that, voltage is controlled so as to be a predetermined voltage, thereby the life of the motor can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electric air pump.

[0002]

2. Description of the Related Art As to a technique for improving the life of an electric air pump, as described in JP-A-5-141396, a motor is installed in an air inlet / outlet passage in order to reduce a temperature rise of the motor, which is a drive unit. Techniques for cooling with a flow of air are described. The life of the motor depends on the wear of the brush, and this wear is affected by the temperature, current, and rotation speed of the brush contact portion. Therefore, if the temperature can be reduced among these three elements, the abrasion of the brush can be reduced, and the life of the motor can be improved.

[0003]

The above-mentioned prior art has the following problems. The temperature rise of the motor can be reduced by installing the motor in the air passage. Therefore, the motor becomes a resistor against the flow of air, and in order to obtain the same air flow rate, it is necessary to improve the motor output, that is, increase the current consumption and increase the rotation speed of the motor. The motor also requires a high current, called the inrush current at start-up, which is another cause of life deterioration. Due to the above reasons, it has not been possible to achieve a significant improvement in the service life, but conversely the current consumption increases and the vehicle fuel consumption deteriorates due to battery overload. In addition, the increase in noise accompanying high-speed rotation and the need to improve the balance accuracy of the rotating body due to the higher speed have caused deterioration in manufacturability. Further, the impeller constituting the pump side is generally made of resin in order to reduce the structure, weight and cost. However, the impeller is fixed to the shaft of the motor, and resin creep occurs at the connection with the shaft due to high-speed rotation.Therefore, it is necessary to use a metallic collar as a countermeasure against that creep, which leads to cost reduction. It is a hindrance.

An object of the present invention is to supply a low-cost electric air pump by using the same motor as the conventional one, but improving the life of the motor and eliminating the collar of the impeller.

[0005]

The above object can be achieved by the following. That is, in an electric air pump including an electric motor, an impeller that is connected to a shaft of the motor and rotates, and a pump unit configured by a casing, and a system that supplies drive power to the motor unit of the electric air pump, By providing a means to start by supplying a voltage lower than the voltage and to gradually increase to a predetermined voltage after starting or within an arbitrary time, the inrush current generated at motor starting is reduced and the life of the motor is improved. In addition to reducing the angular acceleration of the motor, the force applied to the connecting part of the rotating impeller that is connected to the shaft of the motor can be reduced and the creep prevention collar used for the impeller can be eliminated. Next to
Reduce costs.

With the system described above, the motor starting voltage of the electric air pump can be supplied at a voltage equal to or lower than a predetermined voltage by repeating the on / off operation.
Alternatively, the supply voltage can be arbitrarily controlled by the ratio.
When the same motor is used, the inrush current generated when starting the motor largely depends on the starting voltage, and the inrush current increases as the starting voltage increases. Therefore, it is possible to lower the inrush current by controlling the supply voltage at the start to be lower than the predetermined voltage so that the voltage will be the predetermined voltage after the start. In addition, more linear voltage control becomes possible.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system diagram of a vehicle exhaust secondary air system using an electric air pump. The electric air pump 3 sucks and compresses the air that has passed through the air cleaner 2 under the control of the control unit 1, and the solenoid valve 5 turns on and off the secondary air passage. Send to the exhaust side in front of 7. The voltage is applied to the electric air pump under the control of the control unit 1, and the drive voltage is supplied from the battery. Therefore, unless special control is performed, the applied voltage is the same as the battery power supply voltage and is considered to be almost constant. Fig. 2 shows the structure of a vortex pump type, which is a type of electric air pump. The motor 8 as a drive unit is surrounded by a motor cover 9, and is fixed to a casing 10 of the two casings with a screw 12. The impeller 13 has a shaft 15 of the motor 8 and a pump passage 16 concentrically with the casing 10. The other casing 11 is fixed so as to constitute the pump passage 1 by the impeller 13 and the casing 10.
6 is fixed to the casing 10 so that the suction port 17 and the discharge port 18 communicate with the pump flow path 16.
FIG. 3 shows a sectional view taken along the line AA of FIG. The shaft 15 of the motor 8 of the rotor driving unit and the impeller 13 are fixed by press fitting,
Alternatively, a metal collar 14 is provided as a measure against creep of the impeller 13 by screwing. FIG. 4 shows an inrush current waveform at the time of starting when a predetermined supply voltage (14 V) is applied to the electric air pump. Inrush current is about 5 at start
It occurs for a short time of 0 msec, and reaches about 5.6 times the normal drive current thereafter. This inrush current causes the motor 8
The brush wear will be severe. Further, the current consumption of the motor 8 is almost proportional to the supply voltage, and for example, the supply voltage at the start is 1
By lowering from 4V to 8V, the inrush current is 8/1
It can be reduced to 4. FIG. 5 shows the result of a life test of the electric air pump. (A) shows that the number of times of operation is increased and the number of times of inrush current is increased by setting the ON time to be short. (B) shows that the number of times of operation and the number of times of inrush current generation are reduced by setting the ON time to be twice as long as (a). From this figure, it can be seen that the life of (b) where the number of operations is small is about 1.14 when the life of (a) is 1. From this result, it can be seen that the life of the motor 8 depends on the number of operations, that is, the number of times the inrush current is generated. This means that if the motor 8 is used under the same operating conditions, the lower the inrush current, the longer the life. It means that it is possible to plan. Therefore, it is possible to improve the service life by starting at a voltage lower than a predetermined voltage so that the inrush current becomes low as shown in FIG. 4 and then controlling the voltage to reach a predetermined voltage. Further, FIG. 6 shows a comparison of the number of revolutions due to the difference in the supply voltage. As you can see from this figure,
By lowering the supply voltage from 14V to 8V, the rotation speed can be reduced by about 0.6 times, and since there is almost no difference due to the supply voltage in the time required to reach the maximum rotation speed, the angular acceleration is the same. It can be thought of as a ratio. The force applied to the fixed portion of the shaft 15 of the motor 8 and the impeller 13 due to the rotation is approximately proportional to the square of the angular acceleration when the impeller 13 is the same. Therefore, according to this control, the force applied to the fixed part can be reduced to 0.6 squared, that is, 0.36 times, and the stress of the fixed part can also be reduced to 0.36 times, so The metal collar 14 for creep prevention used can be eliminated, and a low-cost pump can be manufactured. The concept of this control is shown in FIG. FIG. 7A shows the motor 8 by this control.
A schematic diagram of the voltage supplied to the device is shown in (b) and (c), and a simplified diagram of the operating condition when duty control is further performed is shown in (d). The effect can be obtained by such control.

[0008]

According to the present invention, the motor is started by supplying a voltage lower than a predetermined voltage, and a means for gradually increasing the voltage to a predetermined voltage after the start or within an arbitrary time is provided. By reducing the inrush current generated at the time of starting, improving the life of the motor, and reducing the angular acceleration of the motor, the force applied to the connecting portion of the rotating impeller connected to the shaft of the motor is reduced,
The creep prevention collar used for the impeller can be eliminated and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram of an exhaust secondary air system.

FIG. 2 is a cross-sectional view of an electric air pump that is a vortex pump.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a waveform diagram of a motor inrush current.

FIG. 5 is an explanatory diagram showing a comparison of motor lives due to a difference in the number of operations (the number of times of inrush current generation).

FIG. 6 is a characteristic diagram showing a comparison of the number of revolutions of the electric air pump depending on the difference in supply voltage.

FIG. 7 is a voltage characteristic diagram in one embodiment of the present invention.

[Explanation of symbols]

1 ... Control unit, 3 ... Electric air pump, 8 ...
Motor, 13 ... Impeller, 14 ... Metal collar.

Claims (4)

[Claims] 1. An electric air pump comprising an electric motor, an impeller that is connected to a shaft of the motor and rotates, and a pump portion constituted by a casing, and a system for supplying drive power to the motor portion of the electric air pump. An electric air pump comprising means for starting a motor by supplying a voltage lower than a predetermined voltage, and gradually increasing the voltage to a predetermined voltage after the start or within an arbitrary time. 2. The drive voltage according to claim 1, wherein the drive voltage is turned on.
An electric air pump that changes using off control. 3. The electric air pump according to claim 2, wherein the drive voltage is changed by duty control. 4. The electric air pump according to claim 2, wherein the control circuit is provided in the control unit or in the electric air pump.