JPH05263865A - Rotor holding structure of built-in type stepping motor of variable damping force type shock absorber - Google Patents

Abstract

PURPOSE:To prevent a thrust load given to two bearings to hold both ends of a rotor, to improve the response of a stepping motor, and to reduce the consuming power. CONSTITUTION:This rotor holding structure 50 holds the rotor 22 of a stepping motor rotatable around the axial line 14. Two bearings 38 and 40 set separating each other along the axial line 14, a circular stopper 24 fixed to a piston and to hold the bearing 38, a cylindrical body 26 fitted playable to the rotor and fixed to the stopper at one end, a circular member 46 fixed to the other end of the cylindrical body, and a guide member 44 to hold the bearing 40 are provided. The guide member 44 is fixed to the circular member 46 by welding under the condition to fit to the circular member by remaining a clearance extending around the axial line 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor having a built-in shock absorber with a variable damping force, and more particularly to a rotor support structure for a stepping motor.

[0002]

2. Description of the Related Art A damping force variable type shock absorber incorporated in a suspension of an automobile or the like generally applies a damping force by driving a valve element for controlling an effective passage sectional area of a bypass passage provided in a piston by an actuator. A stepping motor, which is designed to increase and decrease and is incorporated in a rod portion of a piston as an actuator, has been conventionally known.

As one of the structures for supporting the rotor of such a built-in stepping motor, for example, Japanese Patent Application No. 3-25.
No. 3066 specification and drawings, first and second bearings (5) spaced apart from each other along an axis (14) and supporting a rotor (66) rotatably about the axis.
8, 56) and an annular first bearing support member (62) fixed to the piston rod (26) and supporting the first bearing.
A cylindrical body loosely fitted to the rotor and fixed to the first bearing support member at one end, and a second bearing fitted inside the other end of the cylindrical body and fixed to the other end of the cylindrical body by welding. A rotor support structure for a stepping motor having a second bearing support member (60) that supports the rotor is conventionally known.

[0004]

In the conventional rotor support structure as described above, one end of the cylindrical body is fixed to the first bearing support member (62) by welding, and the first bearing support member has the first bearing support member (62). The bearing (58) and the rotor (66) are mounted, the second bearing (56) is mounted on the rotor, and the second bearing support member (60) is fitted to the other end of the cylindrical body and the second bearing. ) Is mounted, and then the second bearing support member is welded to the other end of the cylindrical body. However, when the second bearing support member is welded to the other end of the cylindrical body, the cylindrical body inevitably partially thermally expands in the axial direction and then thermally contracts. Thrust load is applied to the first and second bearings due to the support member being pressed against the second bearing,
As a result, there is a problem that the rotation resistance of the stepping motor increases, its responsiveness deteriorates, and power consumption easily increases.

In view of the above-mentioned problems in the rotor supporting structure of the built-in stepping motor of the conventional damping force variable type shock absorber, the present invention does not apply a thrust load to the first and second bearings. Accordingly, it is an object of the present invention to provide an improved rotor support structure capable of improving the responsiveness of the stepping motor and reducing the power consumption.

[0006]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide a rotor support structure for a stepping motor for driving a valve element for damping force switching, which is built in a piston of a shock absorber. First and second bearings that are distant from each other and rotatably support the rotor around the axis, and an annular first bearing support member that is fixed to the piston and supports the first bearing. A tubular body that is loosely fitted to the rotor and fixed to the first bearing support member at one end, an annular member fixed to the other end of the tubular body, and a first bearing that supports the second bearing. A second bearing support member, and the second bearing support member is welded to the annular member in a state of being fitted to the annular member leaving a predetermined clearance extending around the axis. Fixed to the annular member by Is achieved by the support structure of the stepping motor rotor, characterized by being.

[0007]

According to the above construction, the second bearing support member for supporting the second bearing is fitted into the annular member leaving a predetermined clearance extending around the axis line, and in that state Since it is fixed by being welded to the annular member fixed to the other end of the body, when the annular member is welded to the other end of the cylinder, the cylinder partially thermally expands in the axial direction and then the heat is applied. Even when contracted, the annular member can freely displace in the axial direction with respect to the second bearing support member without biasing the second bearing support member against the second bearing. Even when these members are partially thermally expanded and then thermally contracted when the members are welded to the annular member, the thermal contraction mainly occurs in the radial direction, and these members hardly thermally contract in the axial direction, Therefore, the second bearing support member is pressed against the second bearing by the annular member. It is not, thereby the power consumption with its responsiveness rotational resistance of the stepping motor is increased is prevented from being deteriorated is reduced.

[0008]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view showing a built-in stepping motor of a shock absorber incorporating a first embodiment of a rotor support structure according to the present invention, and FIG. 2 shows the rotor support structure shown in FIG. It is an expanded longitudinal section shown.

In FIG. 1, reference numeral 10 indicates a piston rod of a shock absorber. A rod end member 12 is fixed to the lower end of the piston rod 10 by screwing, and the rod end member 12 is not shown in the figure.
A piston body having a damping force generation valve is fixed to the. The piston rod 10 has a stepping motor housing hole 16 extending along the axis 14 of the piston rod 10, and a stepping motor 18 is arranged in the housing hole. The stepping motor 18 includes a stator assembly 20 and a rotor 22 that fits on the stator assembly 20 and rotates about an axis 14.
It has become.

In the illustrated embodiment, the stator assembly 2
Reference numeral 0 denotes a stopper 24 as an annular first bearing support member fixed to the piston rod 10 in the accommodation hole 16 by the rod end member 12, and one end fixed to the stopper 24 by welding along the axis line 14. A cylindrical body 26 extending, a plurality of stator magnetic pole members 28 annularly arranged around the cylindrical body 26 in two rows, a resin bobbin 30 integrally holding each stator magnetic pole member 28, and a bobbin. Three
A coil 32 formed by winding a conductive wire around 0
And the lower stator magnetic pole member 28 and the stopper 24 in the drawing.
And an annular spacer 34 interposed between the spacer and the flange portion of the.

As shown in FIG. 1, rotor 22 includes a substantially cylindrical rotor body 36, which includes rotor body 36.
Are rotatably supported about the axis 14 by a first bearing 38 and a second bearing 40 which are spaced from each other along the axis 14. On the outer peripheral surface of the rotor main body 36, a plurality of permanent magnets 42 aligned in the circumferential direction and aligned with the stator magnetic pole member 28 are fixed, and a plurality of permanent magnets 42 are fixed.
The radial outer peripheral surface of each permanent magnet is slightly spaced inward in the radial direction from the inner peripheral surface of the cylindrical body 26.
The coil 2 rotates around the axis 14 when a current is applied to the coil 32.

Bearing 38, as shown in detail in FIG.
The inner race is a small diameter portion 36b at the lower end of the rotor body 36.
The outer race is fixed to the inner peripheral surface of the cylindrical portion 24b of the stopper 24 by press fitting. On the other hand, the outer race of the bearing 40 is the rotor body 36.
The inner race is fixed to the inner peripheral surface of the upper end thereof by press-fitting, and the inner race is fixed to the outer peripheral surface of the cylindrical portion 44b of the lower side of the guide member 44 as the second bearing supporting member by press-fitting. The upper cylindrical portion of the guide member 44 is welded in a state in which it is fitted with an annular member 46 fixed to the upper end of the cylindrical body 26 by welding, leaving a predetermined clearance 48 extending around the axis line 14. By doing so, it is fixed to the annular member 46.

In the particular embodiment shown, the clearance 48 is a cylindrical portion extending along the axis 14 and the axis 1.
4 and a portion extending vertically, and the width of the portion extending vertically is set to be larger than the width of the cylindrical portion. Further, the annular member 46 has a shoulder portion 46a for receiving the upper end of the cylindrical body 26, and the annular member 46 and the guide member 44 form an annular shape around the axis 14 along the clearance at the upper end portion of the clearance 48 in the figure. For example, they are fixed to each other by being welded by electron beam welding.

Thus, the bearings 38 and 40, the stopper 2
4, the cylindrical body 26, the guide member 44, and the annular member 46 form a rotor support structure 50 that rotatably supports the rotor 22 of the stepping motor 18 around the axis 14.

As shown in FIG. 1, the rotor body 36
A ball screw device 52 is arranged inside. The ball screw device 52 has a ball screw shaft 56 extending along the axis 14 and having a spiral groove for receiving a plurality of balls 54 on the outer peripheral surface, and an inner peripheral surface fixed to the inner peripheral surface of the rotor body 36 on the outer peripheral surface. And an outer race member 58 having a spiral groove for receiving the plurality of balls 54. Shaft 56
Has an integrally formed projection 56a having a rectangular cross section at the upper end thereof, and the projection is fitted in a hole 60 having a rectangular cross section provided in the guide member 44 so as to be capable of reciprocating along the axis 14, and thereby the rotor body 36. When the shaft rotates, the shaft 56 moves upward or downward in the figure along the axis 14 without rotating in accordance with the rotation direction.

The shaft 56 integrally has a small diameter portion 56b extending downward from the lower end along the axis 14, and the piston and the rod end member 12 have a small diameter portion 56b at the tip thereof, which is not shown in the drawing. The valve element of the damping force control valve that controls the effective passage cross-sectional area of the provided bypass passage is fixed. Thus, when the rotor 22 rotates about the axis 14, its rotational movement is converted by the ball screw device 52 into a reciprocating movement of the shaft 56 along the axis 14, thereby driving the valve element to increase or decrease the damping force. Is becoming

Since the damping force generating valve and the damping force control valve provided on the piston do not form the subject of the present invention,
A detailed description thereof will be omitted, but if necessary, Japanese Patent Application No. 3-24827 filed by the same applicant as the applicant of the present application
Please refer to the description and drawings of Japanese Patent Application No. 6 or Japanese Patent Application No. 3-253066.

Further, in the illustrated embodiment, the radial outer peripheral edge of each stator magnetic pole member 28 substantially abuts the wall surface of the receiving hole 16 of the piston rod 10, but the bobbin 3
0 and the coil 32 are spaced inward in the radial direction from the wall surface of the accommodation hole 16, and the space defined by these is filled with silicone oil 62 having excellent electrical insulation and thermal conductivity. There is. Further, the axial line 14 is formed on the outer peripheral surface of the portion of the piston rod 10 that houses the stepping motor 18.
A plurality of cooling fins 64 annularly extending around the piston rod 1 are provided so that heat generated in the stepping motor 18 passes through the silicone oil 62 and the piston rod 1
0, and further, the cooling fins 64 efficiently transmit to the oil around the cooling fins, which is not shown in the figure, which prevents the stepping motor temperature from rising to a high temperature. It has become.

When forming the rotor supporting structure 50 of the stepping motor constructed as described above, first, as shown in FIG. 2, the flange portion 24a of the stopper 24 is first formed.
The stopper 24 so that the lower end of the cylindrical body 26 comes into contact with the stopper 24.
One end of the cylindrical body is fitted to the cylindrical portion 24b, and the cylindrical body is fixed to the stopper by welding over the entire circumference at the axial position indicated by A in FIG. Next, as shown in FIG. 1, the small diameter of the rotor main body 36 is adjusted so that the upper end of the shoulder 38a of the rotor main body 36 of the rotor 22 in which the ball screw device 52 and the like are arranged contacts the inner race of the bearing 38 in the drawing. The bearing 38 is mounted by press-fitting the inner race into the portion 36b.

Next, the rotor 22 and the like are inserted into the cylindrical body from the upper end in the figure of the cylindrical body 26, and the outer race of the bearing 38 is press-fitted into the cylindrical section 24b so that the lower end abuts the shoulder portion 24c of the stopper 24 in the figure. Fix by doing. Next, a shoulder portion 36c near the upper end of the rotor body 36
The outer race of the bearing 40 is fixed to the upper end of the rotor body by press fitting so that the lower end of the bearing 40 contacts the inner race of the bearing 40, and the upper end of the bearing 40 contacts the shoulder portion 44a of the guide member 44 and the inner race of the inner race. The guide member is mounted so that is fixed to the lower cylindrical portion 44b of the guide member 44 by press fitting.

Next, a clearance 48 extending annularly around the axis is formed between the guide member 44 and the annular member 46 is fitted to the upper end of the cylindrical body so that the shoulder portion 46a contacts the upper end of the cylindrical body 26. After that, the upper end of the cylindrical body is fixed to the annular member 46 by welding over the entire circumference at the axial position indicated by B in FIG. 2, and further, the guide member 44 and the annular member 46. Are fixed to each other by welding in an annular shape at the radial position indicated by C in FIG.

3 to 5 are enlarged partial vertical cross-sectional views showing the essential parts of the second to fourth embodiments of the rotor support structure according to the present invention. In these figures, the portions corresponding to those shown in FIGS. 1 and 2 are designated by the same reference numerals as those shown in FIGS. 1 and 2.

In the second embodiment shown in FIG. 3, the annular member 46 has a cylindrical shape having an outer diameter that fits in the upper end of the cylindrical body 26 in a press fit manner. Also in this embodiment, the clearance 48 is composed of a cylindrical portion extending along the axis 14 and a portion extending perpendicularly to the axis 14.

In the third embodiment shown in FIG. 4, the annular member 46 has an outer diameter that fits in the upper end of the cylindrical body 26 in a press-fitting manner and has a substantially L-shaped cross-sectional shape. Have The clearance 48 has a stepwise cross-sectional shape, and has a first cylindrical portion extending along the axis 14, a portion extending perpendicularly to the axis 14 and a second portion extending along the axis 14. It consists of a cylindrical part.

In the fourth embodiment shown in FIG. 5, the annular member 46 has a cylindrical shape having an outer diameter which is press fit into the upper end of the cylindrical body 26 as in the case of the second embodiment. Is playing. Further, the clearance 48 is composed only of a cylindrical portion extending along the axis 14. In any of the second to fourth embodiments, the annular member 46 and the guide member 44
Are fixed to each other by being welded annularly around the axis 14 along the clearance at the upper end portion of the clearance 48 in the figure, for example by electron beam welding.

Thus, according to each of the illustrated embodiments, the upper end of the cylindrical body 26 is annular with the clearance 48 extending annularly around the axis 14 between the guide member 44 and the annular member 46. Since it is welded to the member 46, the guide member 44 is not urged downward in the figure by the cylindrical body 26 and the annular member 46 even if the welded portion of the cylindrical body 26 thermally contracts in the axial direction. Further, when the guide member 44 and the annular member 46 are welded, even if the welded portions of these members undergo thermal contraction, thermal contraction occurs mainly in the radial direction, and these two members hardly contract in the axial direction. Even when the guide member 44 and the annular member 46 are fixed to each other by welding, the bearing 40 is not biased downward by the guide member in the figure. Therefore, an excessive thrust load is not applied to the bearings 38 and 40, and it is surely avoided that the frictional resistance of these bearings increases due to the thrust load, thereby improving the responsiveness of the stepping motor. The power consumption can be reduced.

Further, according to the illustrated embodiment, the space between the piston rod 10, the bobbin 30 and the coil 32 is filled with silicone oil 62, and the portion of the piston rod 10 which houses the stepping motor 18 is also filled. Since a plurality of cooling fins 64 are provided on the outer peripheral surface of the, the heat generated in the stepping motor is efficiently transmitted to the oil around the piston rod through the silicon oil 62 and the cooling fins 64, and thereby the stepping motor is cooled. It is possible to reliably prevent the temperature of the motor from rising excessively.

Further, particularly according to the first embodiment shown in FIGS. 1 and 2, since the annular member 46 has the shoulder portion 46a for receiving the upper end of the cylindrical body 26, the annular member 46 is formed into the cylindrical body. It can be easily and accurately positioned and fixed to the upper end of 26.

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to these embodiments, and various other embodiments within the scope of the present invention. It will be apparent to those skilled in the art that

For example, in the illustrated embodiment, the bobbin 30
The space between the coil 32 and the wall surface of the accommodation hole 16 is filled with silicone oil 62. The liquid filled in this space is any liquid having excellent electrical insulation and thermal conductivity. You can Also, in the illustrated embodiment, the cooling fins 64 extend annularly around the axis 14,
The cooling fins may be provided to extend along the axis 14, for example.

In the illustrated embodiment, the rotor 22 of the stepping motor 18 has its rotational movement in the axis line 14.
Although a ball screw device 52 for converting into a linear motion along the axis is provided, one end of a drive shaft is fixedly connected to the rotor 22, and the other end of the drive shaft is provided with a valve element for increasing or decreasing the damping force by rotational displacement. It may be fixed.

[0033]

As is apparent from the above description, according to the present invention, the second bearing support member for supporting the second bearing is an annular member leaving a predetermined clearance extending around the axis. It is fitted and fixed in that state by being welded to the annular member fixed to the other end of the tubular body, so that when the annular member is welded to the other end of the tubular body, the tubular body moves in the axial direction. The annular member is free to displace in the axial direction with respect to the second bearing supporting member without urging the second bearing supporting member against the second bearing even if it partially thermally expands and then thermally contracts. When the second bearing support member is welded to the annular member, even if these members partially thermally expand and then thermally contract, the thermal contraction occurs mainly in the radial direction, and these members are almost The second bearing support member does not shrink due to heat in the axial direction. Since it is not pressed against the second bearing, it effectively prevents the thrust load due to heat shrinkage from being applied to the first and second bearings. The responsiveness of the motor can be improved and the power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a built-in stepping motor of a shock absorber incorporating a first embodiment of a rotor support structure according to the present invention.

FIG. 2 is an enlarged vertical sectional view showing a rotor support structure shown in FIG.

FIG. 3 is an enlarged partial vertical sectional view showing a main part of a second embodiment of the rotor support structure according to the present invention.

FIG. 4 is an enlarged partial vertical sectional view showing a main part of a third embodiment of the rotor support structure according to the present invention.

FIG. 5 is an enlarged partial vertical cross-sectional view showing an essential part of a fourth embodiment of the rotor support structure according to the present invention.

[Explanation of symbols]

 10 ... Piston rod 18 ... Stepping motor 20 ... Stator assembly 22 ... Rotor 24 ... Stopper 26 ... Cylindrical body 28 ... Stator magnetic pole member 36 ... Rotor body 38, 40 ... Bearing 44 ... Guide member 46 ... Annular member 48 ... Clearance 50 ... Rotor support structure 52 ... Ball screw device 62 ... Silicon oil 64 ... Cooling fin

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Kono 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation

Claims (1)

[Claims] 1. A support structure for a rotor of a stepping motor, which is incorporated in a piston of a shock absorber and drives a valve element for switching a damping force, and which is spaced from each other along an axis to rotate the rotor around the axis. The first and second bearings that can be supported, the annular first bearing support member that is fixed to the piston and that supports the first bearing, and the first bearing support member that is loosely fitted to the rotor and is the first end at one end. A second bearing support having a tubular body fixed to the bearing support member, an annular member fixed to the other end of the tubular body, and a second bearing support member that supports the second bearing. The member is fixed to the annular member by being welded to the annular member while being fitted to the annular member leaving a predetermined clearance extending around the axis line. Motor low Support structure.