JPH07250465A - Stepping motor - Google Patents

Abstract

PURPOSE:To provide a stepping motor, which can decrease the friction and abrasion of a screw part and can alleviate a rotating load. CONSTITUTION:This stepping motor 1 has the structure, wherein the rotation of a rotor 4 is converted into the movement in the axial direction by the action of a screw, and an output shaft 9 is moved into the axial direction. The motor is formed in the tubular shape, and a plurality of permanent magnets 7 are provided at the outer surface part. At the same time, the following parts are provided. A screw supporting part 8 having a tapped hole at the shaft-center position is provided in a rotor 4. The output shaft 9 has a male screw at the outer surface part. The output shaft 9 is screwed and inserted into the tapped hole of the screw supporting part 8 of the rotor 4. A spring bearing member 10 is arranged in the rotor 4 so that the member 10 can be moved in the axial direction and has a tapped hole at the shaft center position. The output shaft 9 is screwed and inserted into the tapped hole. A compression spring 11 is arranged between the rotor 4 and the spring bearing member 10 and energizes the rotor 4 and the spring bearing member 10 into the relative axial direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor applicable to a flow control valve used in an intake system, an exhaust system, etc. of an internal combustion engine.

[0002]

2. Description of the Related Art As a flow control valve used in an intake system, an exhaust system, etc. of an internal combustion engine, a valve chamber having a plurality of ports is formed in a valve housing, and a lift type valve body and a valve seat portion are formed in the valve chamber. There is known a flow control valve having a structure in which a motor for moving a valve shaft of a valve element is attached to a valve housing (see, for example, Japanese Utility Model Laid-Open No. 4-108367).

A step motor is generally used for this type of flow control valve, and the step motor has a female screw on the inner circumference of a rotor having an internal space at the axial center position.
An output shaft having a male screw is inserted so as to be screwed with a female screw in the rotor, and a valve element is attached to the tip of the output shaft directly or via the valve shaft. Then, through the threaded portion between the rotor and the output shaft, the rotation of the rotor is converted into axial movement,
The output shaft, that is, the valve element is moved in the axial direction to open and close the valve.

[0004]

By the way, a flow control valve of this type used in an internal combustion engine receives considerable vibration during operation of the engine, but suppresses vibration of an output shaft mounted via a screw, In order to prevent backlash peculiar to the operation of the screw, conventionally, a compression coil spring for urging the output shaft (valve body) in one direction is provided between the valve body and the housing or between the output shaft and the housing. Has been.

This compression coil spring 30 is shown in FIG.
As shown in, the valve is provided between the upper portion of the valve body 31 and the housing 33 that supports the output shaft (valve shaft) 32 above the valve body 31, and the valve is fully closed when the output shaft 32 is most protruded downward. When the valve is fully opened when the shaft 32 is most pulled back upwards, the compression coil spring 3 is closed when the valve is fully closed.
Since the height of 0 is high and the compression rate thereof is small, the spring load applied to the output shaft 32 is small, but when the valve is fully opened, the compression coil spring 30 is compressed and the spring load increases.

For this reason, the spring constant of the compression coil spring 30 mounted for the purpose of suppressing the vibration of the output shaft 32 and preventing backlash is as follows: when the valve is fully closed, that is, when the compression rate is small and the spring load is small. Since the spring force is set to have a sufficient spring force to prevent vibration and the like, the spring load of the coil spring that is in a compressed state when the valve is fully opened is considerably large.

Therefore, in the step motor, when the valve body is moved in the opening direction (upper side), the rotational load of the step motor is increased, and there is a problem that the torque of the step motor is increased and the shape is increased. Further, when the biasing force of the compression coil spring 30 increases, the frictional force between the rotor 34 and the screw portion 35 of the output shaft 32 increases, and there is a problem that the wear of that portion increases.

The present invention has been made in view of the above points, and an object of the present invention is to provide a step motor capable of reducing friction and wear of a screw portion and reducing a rotational load.

[0009]

In order to achieve the above object, a step motor of the present invention converts the rotation of a rotor into an axial movement by the action of a screw to move an output shaft in the axial direction. In, a rotor formed in a tubular shape and provided with a plurality of permanent magnets on the outer peripheral portion and a screw support portion having a screw hole at the axial center position, and a screw on the outer peripheral portion, and a screw support portion of the rotor The output shaft that is screwed into the screw hole and is axially movable in the rotor, and has a screw hole at the shaft center position, and the output shaft is screwed into the screw hole and inserted. And a spring means arranged between the rotor and the spring receiving member for urging the rotor and the spring receiving member in the relative axial direction.

Here, a compression coil spring or a spring washer can be used as the spring means.

[0011]

[Operation / Effect] With the step motor having such a configuration,
When the rotor is rotated to the left, for example, by the activation, the rotation of the rotor is converted into an axial movement of the output shaft by the action of the screw support portion of the rotor and the screw portion of the output shaft, and the output shaft projects its tip. To move. On the other hand, when the rotor rotates to the right, the output shaft moves so as to pull back its tip by the action of the screw support portion of the rotor and the screw portion of the output shaft.

During this time, the spring means disposed between the rotor and the spring receiving member constantly urges the rotor and the spring receiving member in the relative axial direction, so that the output shaft and the screw supporting portion of the rotor and the output. At the threaded portion where the shaft and the spring receiving member are screwed together, one thread ridge surface is always in contact with each other to prevent the rattling of the screw.

For this reason, when the step motor is used in a flow rate control valve that vibrates violently, the vibration of the output shaft can be suppressed to a minimum and the backlash of the screw portion can be prevented.

Further, since the spring load of the spring means may be set to a minimum value capable of preventing the vibration of the output shaft and the backlash of the screw portion, the frictional force of the screw portion can be made smaller than that of the prior art. The wear of the part can be reduced.

Further, the spring load of the spring means arranged between the rotor and the spring receiving member is always constant at the minimum value, and the output shaft operates so as to compress the compression coil spring as in the conventional case. Therefore, the load on the output shaft can be significantly reduced, and the required torque can be reduced to reduce the size of the motor.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional view of a flow control valve to which the step motor of the present invention is applied. Reference numeral 2 denotes a housing of the step motor 1. In the housing 2, a stator having an exciting coil 3 wound around a bobbin is fixed, and a rotor 4 is arranged inside the stator. The rotor 4 is rotatably supported by the housing 2 at its upper and lower parts via ball bearings 5 and 6.

The rotor 4 is formed in a tubular shape as a whole, and a plurality of permanent magnets 7 are fixed to the outer peripheral portion thereof. Further, a screw support portion 8 having a screw hole at the center is formed at the axial center position of the rotor 4, and since it is formed on the inner periphery thereof, a male screw 9a of an output shaft 9 described later is screwed into the screw 8a.

Further, as shown in the enlarged view of FIG. 3, a spring receiving member 10 is arranged inside the axial position of the rotor 4 at a position facing the screw supporting portion 8. The spring receiving member 10 has a screw hole having a female screw 10a at the center, and the output shaft 9 is inserted into the screw hole by screwing the female screw 10a and the male screw 9a. Further, as shown in FIG. 2, the spring receiving member 10 has a protrusion and a flat portion, and by engaging the protrusion and the flat portion with the corresponding recesses in the rotor 4, the spring receiving member 10 can be moved in the axial direction. While allowing, it can rotate with the rotor 4.

A compression coil spring 11 is arranged between the spring receiving member 10 arranged in the rotor 4 and the screw supporting portion 8. The compression coil spring 11 urges the screw support portion 8 of the rotor 4 to which the output shaft 9 is screwed and the spring receiving member 10 in the mutually opposite axial directions, and the spring load thereof is the spring receiving member 10 and the screw supporting portion. It can be set arbitrarily by adjusting the interval of 8.

The spring load of the compression coil spring 11 is such that when the flow control valve is actually used and is subjected to vibration, vibration of the output shaft 9 due to rattling of the screw portion, friction and wear of the screw portion, The minimum value is set so that backlash can be effectively suppressed.

The lower portion of the output shaft 9 projects downward from the rotor 4, penetrates the cover plate 12 fixed to the lower portion of the housing 2, and the valve body 13 is fixed to the tip thereof. The lower portion of the output shaft 9 is formed to have a modified cross section, and the bearing portion of the cover plate 12 prevents the rotation of the output shaft 9 and supports the output shaft 9 so as to be movable in the axial direction. Further, a stopper 9b for stopping at the pulling back end and the projecting end is provided on a part of the output shaft 9.

As shown in FIG. 1, the step motor 1 having the above-described structure has the valve body 13 at the tip of its output shaft and the valve chamber 16.
It is secured downwardly to the top of the valve housing 15 for insertion therein.

A circulation hole 17 having a valve seat 17a on the periphery thereof is formed below the valve chamber 16, and the circulation hole 17 is opened and closed by raising and lowering the valve body 13. An inlet port 18 is provided on the right side of the valve chamber 16 and an outlet port 19 is provided on the left side of the valve housing 15.

Next, the operation of the flow control valve will be described. When closing the valve, the step motor 1 rotates the rotor 4 to the left. When the rotor 4 rotates to the left, the rotation of the rotor 4 is converted into the axial movement of the output shaft 9 by the action of the screw support portion 8 of the rotor 4 and the screw portion of the output shaft 9, and the output shaft 9 has its tip end. Move to stick out.

On the other hand, when the valve is opened, the step motor 1 rotates the rotor 4 rightward. When the rotor 4 rotates to the right, the output shaft 9 moves so as to pull back the tip thereof by the action of the screw support portion 8 of the rotor 4 and the screw portion of the output shaft 9.

During this time, the compression coil spring 11 disposed between the screw support portion 8 of the rotor 4 and the spring receiving member 10 constantly urges the rotor 4 and the spring receiving member 10 in the relative axial direction. Therefore, in the screw supporting portion 8 of the output shaft 9 and the rotor 4, and in the screw portion where the output shaft 9 and the spring receiving member 10 are screwed, one screw thread surface is always in contact with each other, and rattling of the screw is prevented.

Therefore, when the step motor 1 is used in a flow rate control valve that vibrates violently, the vibration of the output shaft 9 can be suppressed to a minimum and the backlash of the screw portion can be prevented. .

Further, since the spring load of the compression coil spring 11 may be set to the minimum value capable of preventing the vibration of the output shaft 9 and the backlash of the screw portion, the frictional force of the screw portion can be made smaller than before. It is possible to reduce wear of the threaded portion.

Further, the spring load of the compression coil spring 11 arranged between the rotor 4 and the spring receiving member 10 is always the minimum value regardless of the movement of the output shaft 9, and as in the conventional case, Since the output shaft does not operate to compress the compression coil spring, the load on the output shaft 9 can be significantly reduced. Therefore, the required motor torque can be reduced, and the motor can be downsized.

FIG. 4 shows another embodiment. In this example, instead of the compression coil spring 11, a spring washer 21 such as a wave washer is used as a spring receiving member 20 and a screw supporting portion 28.
The spring washer 21 urges the spring receiving member 20 and the screw support portion 28 in the relative axial direction. Even when this spring washer 21 is used, it operates in the same manner as above,
The operation and effect are similar, but when the spring washer 21 is used, the rotor 4 is more effective than when the compression coil spring is used.
The axial length of can be shortened.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a flow control valve using a step motor of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged cross-sectional view of the inside of a rotor.

FIG. 4 is an enlarged cross-sectional view of the inside of a rotor of another embodiment.

FIG. 5 is a vertical sectional view of a flow control valve using a conventional step motor.

[Explanation of symbols]

1-step motor, 4-rotor, 7-permanent magnet, 9-
Output shaft, 10-spring receiving member, 11-compression coil spring.

Claims (3)

[Claims] 1. A step motor that converts the rotation of a rotor into an axial movement by the action of a screw to move an output shaft in the axial direction. The step motor is formed in a tubular shape, and a plurality of permanent magnets are provided on an outer peripheral portion of the step motor. A rotor having a screw support portion having a screw hole at an axial position, an output shaft having a screw on an outer peripheral portion and screwed into a screw hole of the screw support portion of the rotor, and the inside of the rotor A spring receiving member that is movably arranged in the axial direction, has a screw hole at the axial center position, and the output shaft is screwed into the screw hole and is inserted; and the rotor and the spring receiving member. A stepping motor provided between the spring and the spring means for urging the rotor and the spring receiving member in the relative axial direction. 2. The step motor according to claim 1, wherein the spring means is a compression coil spring. 3. The spring means is a spring washer.
Step motor described.