JP3716653B2 - Linear motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The linear motor according to the present invention is used in a state where it is incorporated in various mechanical devices such as a nursing bed, a lifting table, a CT scanner, a truck cabin tilt device, and a lifter.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, a combination of an electromagnetic solenoid, an electric motor, and a feed screw mechanism is known as an electric linear actuator.
Among these, the electromagnetic solenoid can be made small and light, but it is difficult to obtain a large stroke, and the force that can be obtained is limited.
Moreover, since the combination of the electric motor and the feed screw mechanism is combined with an independent mechanism, it is large and heavy. In addition, a device using a general sliding screw mechanism has a large loss at the sliding friction portion and is inefficient. On the other hand, the one using the ball screw mechanism is costly and has a larger size instead of being efficient.
In view of such circumstances, the present invention was invented to realize a linear motor that is small and light, can obtain a large stroke, and is efficient.
[0003]
[Means for Solving the Problems]
The linear motor of the present invention includes a drive side member that is rotatably supported in a motor housing, a rotor fixed to the outer peripheral surface of the drive side member in the motor housing, and an inner peripheral surface of the rotor on the outer periphery of the rotor. A stator fixed in the motor housing in a state of being opposed to the surface, and an outer diameter smaller than the inner diameter of the drive side member, and in an eccentric state with respect to the drive side member, on the inner diameter side of the drive side member The driven side member supported so as to be able to rotate and displace in the axial direction, and the outer peripheral surface of the driven side member and the inner peripheral surface of the driving side member are formed on one peripheral surface. The same pitch as the thread groove formed in the circumferential direction on the other circumferential surface of the spiral thread groove and the outer peripheral surface of the driven side member and the inner peripheral surface of the driving side member And an engagement groove having a part of the driven side member And an output member coupled with the last load bearing freely rolling. A part of the thread groove in the circumferential direction and a part of the engagement groove in the circumferential direction are engaged with each other.
[0004]
In addition, among the constituent elements constituting the linear motor of the present invention as described above, the combination state of the driving side member and the driven side member is, for example, the following modes (1) to (3) Can be considered.
(1) The drive side member is a nut member having an internal thread formed on the inner peripheral surface thereof, and the driven side member is a screw rod shape having an external thread formed on the outer peripheral surface thereof. A drive member is disposed in parallel to the nut member, and a part of the female screw in the circumferential direction and a part of the male screw in the circumferential direction are engaged with each other.
(2) On the inner peripheral surface of the driving side member, a plurality of mutually parallel protrusions provided in the circumferential direction are formed, and external threads are formed on the outer peripheral surface of the driven side member. The driving side member and the driven side member are arranged in parallel to each other, and a part of the protrusion in the circumferential direction and a part of the male screw in the circumferential direction are engaged with each other.
(3) On the outer peripheral surface of the driven side member, a plurality of parallel protrusions each provided in a circumferential direction are formed, and on the inner peripheral surface of the driving side member, a female screw is formed, respectively, The driven side member and the driving side member are arranged in parallel to each other, and a part of the protrusion in the circumferential direction and a part of the female screw in the circumferential direction are engaged with each other.
[0005]
[Action]
The linear motor of the present invention configured as described above rotates the drive-side member based on energization, thereby rotating the driven-side member while rotating the driven-side member, and by the output member, Take out axial displacement.
That is, on the basis of energization, the driving side member having the rotor fixed to its outer peripheral surface rotates, and the driven side member is rotated based on the engagement between the screw groove and the engaging groove as the driving side member rotates. ,Rotate. At this time, the circumferential speed of these screw grooves and the circumferential speed of the engaging grooves are equal to each other. Further, the pitch of the thread grooves that mesh with each other is equal to the pitch of the engagement grooves. On the other hand, since the pitch circle diameter of these thread grooves and the pitch circle diameter of the engagement grooves are different, the driven side member rotates one or more times while the driving side member rotates once. As a result, the driven member and the output member coupled to the driven member are displaced in the axial direction by the amount that the driven member rotates more than the driven member.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
1-3 show a first example of an embodiment of the present invention corresponding to the above-mentioned (1). The linear motor 1 of this example supports a cylindrical nut member 3 that is a drive side member inside a motor housing 2 so as to be rotatable only. That is, the motor housing 2 is configured to be hollow by closing the opening of the bottomed cylindrical housing body 4 with the disc-shaped lid 5. Further, the inner diameter of the intermediate portion in the axial direction of the nut member 3 is made smaller than the inner diameter of the portion other than the intermediate portion, and a female screw 6 having a pitch circle diameter D ₀ is formed in the intermediate portion. A rotor 7 is fitted and fixed to the outer peripheral surface of the intermediate portion of the nut member 3. On the other hand, a stator 8 is fixed to the inner peripheral surface of the motor housing 2, and the inner peripheral surface of the stator 8 and the outer peripheral surface of the rotor 7 are closely opposed to each other. In this example, an AC motor is used as the driving motor. However, the structure of the motor itself is not particularly limited, and is not the gist of the present invention, and thus detailed description is omitted.
[0007]
The nut member 3 is a deep groove type or angular type ball provided between the outer peripheral surfaces of both end portions of the nut member 3 and the inner surface of the bottom plate portion 9 constituting the housing body 4 and the inner surface of the lid body 5. The bearings 10 and 10 support the inner center portion of the motor housing 2 so as to be rotatable only (not displaceable in the axial direction). Accordingly, the nut member 3 rotates within the motor housing 2 (without being displaced in the axial direction) based on energization to the stator 8.
[0008]
The motor housing 2 supports a drive member 11 having a circular shape so as to be freely rotated and displaced in the axial direction. The outer diameter of the driven member 11 is smaller than the inner diameter of the portion where the female screw 6 is formed at the intermediate portion of the nut member 3. In addition, a male screw 12 having a pitch circle diameter of d ₀ is formed on the outer peripheral surface of the intermediate portion of the driven side member 11. Such a driven side member 11 is supported at a portion slightly deviated from the central portion of the motor housing 2 (by δ described below) so as to be freely rotatable and displaceable in the axial direction. That is, the portions near the both ends of the intermediate portion of the driven side member 11 inside the support cylinder portions 14 and 14 formed at the center portion of the bottom plate portion 9 and the lid 5 of the housing body 4 constituting the motor housing 2, It is supported by bearings 13 and 13 that support a radial load but not a thrust load, such as a slide bearing and a needle bearing. In this state, the central axis of the driven member 11 is δ {= (D ₀ −d ₀ ) / 2} which is ½ of the difference in pitch circle diameter with respect to the central axis of the nut member 3. Eccentric. Therefore, the male screw 12 formed on the outer peripheral surface of the driven member 11 is meshed only with a part in the circumferential direction with the female screw 6 formed on the inner peripheral surface of the nut member 3. In the case of this example, one of the male screw 12 and the female screw 6 corresponds to the thread groove described in the claims, and the other corresponds to the engagement groove.
[0009]
The output member 15 is coupled to the distal end portion (right end portion in FIG. 1) of the driven side member 11 by a deep groove type ball bearing 16 that is a bearing for supporting a thrust load. Accordingly, the output member 15 is displaced in the axial direction in synchronization with the driven member 11 while rotating with respect to the driven side member 11.
Further, in the illustrated example, a preload means such as a compression coil spring 17 is provided between the outer surface of the lid 5 constituting the motor housing 2 and the output member 15. The thrust of the compression coil spring 17 applies a thrust load to the driven member 11 via the output member 15 to apply a preload to the meshing portion of the male screw 12 and the female screw 6. . Thus, even when a thrust load is not applied to the output member 15, when the power is transmitted from the nut member 3 to the driven member 11, the meshing portion does not slip. However, the preload means as described above is not always necessary if the linear motor 1 is used in a state where the output member 15 is always subjected to a thrust load.
[0010]
The linear motor 1 of the present example configured as described above is configured to rotate the driven member 11 while rotating the driven member 11 by rotating the nut member 3 to which the rotor 7 is fixed based on energization to the stator 8. The axial displacement of the driven member 11 is taken out by the output member 15. That is, when the output member 15 is displaced in the axial direction, the nut member 3 having the rotor 7 fixed to the outer peripheral surface thereof is rotated in a predetermined direction based on energization of the stator 8.
[0011]
As the nut member 3 rotates, the driven member 11 rotates based on the engagement between the female screw 6 and the male screw 12. At this time, the peripheral speed of the female screw 6 and the peripheral speed of the male screw 12 are equal to each other. Further, as shown in FIG. 3, the pitch P of the female screw 6 and the pitch P of the male screw 12 that mesh with each other are equal to each other. In contrast, the different pitch circle diameter d ₀ of the pitch circle diameter D ₀ and the external thread 12 of the internal thread _{6 (D 0> d 0)} . For this reason, while the nut member 3 rotates once, the driven side member 11 rotates one rotation or more (D ₀ / d ₀ times).
[0012]
As a result, the driven-side member 11 is rotated by an amount that the driven-side member 11 rotates more than the nut member 3 (for each rotation of the nut member 3 (D ₀ / d ₀ ) −1 times). The output member 15 coupled to the driven member 11 is displaced [P · {(D ₀ / d ₀ ) −1}] in the axial direction. The driven member 11 is displaced in the axial direction while rotating. However, since the output member 15 is rotatable with respect to the driven member 11, the output member 15 does not rotate and is axially moved. The member to which the distal end portion of the output member 15 is coupled is pushed and pulled.
The engagement state between the female screw 6 and the male screw 12 is close to rolling contact, and the sliding contact state is slight. For this reason, the power loss at the engaging portion between the female screw 6 and the male screw 12 is small, and the linear motor 1 as a whole can have high efficiency.
[0013]
Next, FIG. 4 shows a second example of the embodiment of the present invention, which also corresponds to the above item (1). In the case of the linear motor 1a of this example, a cylindrical output member 15a is connected to the distal end portion (right end portion in FIG. 4) of the driven side member 11a by a deep groove type ball bearing 16 and the driven side member 11a. It is coupled so as to freely rotate in the axial direction and in synchronization with the driven side member 11a. An expandable / contractible bellows 18 is provided between the outer surface of the lid 5 constituting the motor housing 2 and the base end portion (left end portion in FIG. 4) of the output member 15a. The preloading means as in the first example described above is not provided. Further, a coupling cylinder 19 for coupling the motor housing 2 to another portion is provided at the center of the outer side surface (left side surface in FIG. 4) of the bottom plate portion 9 of the housing body 4 constituting the motor housing 2. One end (the right end in FIG. 4) is joined. When the structure of this example is used, the other end portion of the coupling cylinder 19 and the tip end portion (the right end portion in FIG. 4) of the output member 15a are coupled and supported to a portion whose interval should be enlarged or reduced. Further, a thrust load in a direction approaching each other is applied to the coupling cylinder 19 and the output member 15a in use.
[0014]
Further, in the case of this example, in order to increase (longen) the stroke, a long member is used as the driven member 11a, and the external thread 12a is formed on the outer peripheral surface of the driven member 11a over almost the entire length. Is forming. Such a driven member 11a is supported at both ends of the motor housing 2 by deep groove ball bearings 20 and 20, respectively, so as to be rotatable and displaceable in the axial direction. That is, the outer rings 21 and 21 constituting the respective ball bearings 20 and 20 are fixed to the bottom plate portion 9 of the housing body 4 and the center portion of the lid body 5 constituting the motor housing 2 by an interference fit or adhesion, Inner rings 22 and 22 constituting the ball bearings 20 and 20 are externally fitted to the driven member 11a by gap fitting. In the case of the structure of this example, the male screw 12a formed on the outer peripheral surface of the driven side member 11a may be a triangular thread screw at a low processing cost, but the inner peripheral surfaces of the inner rings 22 and 22 described above. In consideration of the friction state, it is preferable to use a square screw including a trapezoidal screw. Since other configurations and operations are the same as those in the case of the first example described above, the same parts are denoted by the same reference numerals, and redundant description is omitted.
[0015]
Next, FIG. 5 shows a third example of the embodiment of the present invention. In the case of this example, the nut member 3a, which is a drive side member, is configured by connecting a large diameter portion 23 and a small diameter portion 24 that are concentric with each other by a step portion 25. Of these, the small-diameter portion 24 is supported at the inner central portion of the motor housing 2 by a pair of ball bearings 10 and 10 each of which is a deep groove type or an angular type, and the large-diameter portion 23 is , And protrudes out of the motor housing 2. And the internal thread 6a is formed in the internal peripheral surface of this large diameter part 23. FIG.
[0016]
Further, a rotor 7a and a commutator 26 are provided in an intermediate portion of the small diameter portion 24 and between the pair of ball bearings 10 and 10. On the other hand, on the inner peripheral surface of the housing body 4 constituting the motor housing 2, a stator 8 a, which is a permanent magnet, is disposed on a portion facing the outer peripheral surface of the rotor 7 a, and a portion facing the outer peripheral surface of the commutator 26. Are provided with a pair of brush holders 27, respectively. Then, the front end surfaces of the brushes 28 and 28 held by these brush holders 27 are elastically pressed against the outer peripheral surface of the commutator 26 to constitute a DC motor for rotationally driving the nut member 3a. Yes.
[0017]
On the other hand, the shaft-like output member 15b can be rotated and displaced in the axial direction by bearings 13 and 13 that support a radial load but not a thrust load, such as a slide bearing and a needle bearing, inside the small diameter portion 24. I support it. A driven-side member 11b is supported by an angular ball bearing 29 at a portion located inside the large-diameter portion 23 at the base end portion (right end portion in FIG. 5) of the output member 15b. The base end portion of the output member 15b is ½ of the difference between the pitch circle diameter D ₀ of the female screw 6a and the pitch circle diameter d ₀ of the male screw 12b described below with respect to the nut member 3a {δ = (D ₀₋ d ₀ ) / 2} is decentered by δ. Then, a part in the circumferential direction of the male screw 12b formed on the outer peripheral surface of the driven shaft member 11b and a part in the circumferential direction of the female screw 6a formed on the inner peripheral surface of the large-diameter portion 23 are engaged with each other. ing.
[0018]
The linear motor 1b of this example is used in a state where a thrust load in the left direction in FIG. 5 is applied to the output member 15b. The outer ring and the inner ring of the ball bearing 29 are fitted to the inner peripheral surface of the driven shaft member 11b and the outer peripheral surface of the base end portion of the output member 15b in a state that they do not move regardless of the thrust load. Accordingly, the output member 15b rotates with respect to the driven shaft member 11b, but is displaced together with the driven shaft member 11b in the axial direction.
[0019]
In the case of the linear motor 1b of the present example configured as described above, when the rotor 7a is energized through the brushes 28, 28 and the nut member 3a having the rotor 7a fixed to the outer peripheral surface thereof is rotationally driven, the female screw 6a The driven shaft member 11b is displaced in the axial direction while rotating based on the engagement between the screw and the male screw 12b. Of these, the displacement in the axial direction is taken out by the output member 15b, and the member engaged with the end of the output member 15b is displaced.
[0020]
Next, FIG. 6 shows a fourth example of the embodiment of the present invention, which also corresponds to (1) described above. This example shows the case where the present invention is applied to a flat motor (disk type motor). For this reason, in the case of the linear motor 1c of this example, the nut member 3b which is a driving side member and the driven side member 11c are supported inside the flat motor housing 2a. That is, the nut member 3b is supported by the deep groove type or angular type ball bearings 10 and 10 at the intermediate portion in the axial direction of the motor housing 2a so as to be rotatable only. Further, a flat and disc-like rotor 7b is fixed to a portion between the ball bearings 10 and 10 on the outer peripheral surface of the intermediate portion of the nut member 3b. And this rotor 7b and the stator 8b provided in the inner surface of the baseplate part 9a of the housing main body 4a which comprises the said motor housing 2a are made to oppose each other through the clearance of a thrust direction.
[0021]
On the other hand, at both ends of the motor housing 2a, portions near the both ends of the driven side member 11c are respectively supported by bearings 13 and 13 that support radial loads, such as slide bearings and needle bearings, but not thrust loads. , Support. Therefore, the driven member 11c is supported on the inner side of the motor housing 2a so as to be rotatable and displaceable in the axial direction. And in the middle part of the outer peripheral surface of the driven side member 11c, a part in the circumferential direction of the male screw 12c formed between the pair of bearings 13 and 13 and the inner peripheral surface of the nut member 3b. Part of the circumferential direction of the female screw 6b formed over the entire length is meshed with each other.
[0022]
Further, the output member 15c is coupled to the inner diameter side of the driven side member 11c by deep groove type or angular type ball bearings 30 and 30 which are bearings for supporting a thrust load.
In the case of the linear motor 1c of the present example configured as described above, when the nut member 3b is rotationally driven, the driven side member 11c is displaced in the axial direction while rotating. The output member 15c is taken out and the member engaged with the end of the output member 15c is displaced.
[0023]
Next, FIG. 7 shows a fifth example of the embodiment of the present invention corresponding to the above-mentioned (2). In the case of this example, a plurality of parallel protrusions 31, 31 provided in the circumferential direction on the outer peripheral surface of the shaft-like driven side member 11 d are arranged at equal intervals (at equal pitches). ) And the portions where the protrusions 31 and 31 are formed are the engagement grooves described in the claims. The pitch P of each of the protrusions 31 and 31 is the same as the pitch P of the female screw 6 formed on the inner peripheral surface of the nut member 3.
[0024]
Also in the case of the structure of this example as described above, when the nut member 3 is rotated, the driven member 11d is displaced in the axial direction while rotating. In particular, in the case of this example, the nut member 3 is compared with the case of the first to fourth examples in which the external threads 12, 12a, 12b, and 12c are formed on the outer peripheral surfaces of the driven side members 11, 11a, 11b, and 11c. The amount of displacement of the driven side member 11d in the axial direction increases each time one rotation is made. That is, in this example, every time the nut member 3 makes one rotation, the driven member 11d is displaced in the axial direction by P · (D ₀ / d ₀ ). Other configurations and operations are the same as those in any of the first to fourth examples described above, and thus illustrations and descriptions regarding the equivalent parts are omitted.
[0025]
Although illustration is omitted, contrary to the case of the fifth example shown in FIG. 7, male threads are formed on the outer peripheral surface of the driven member in place of the plurality of protrusions, and in place of the nut member. The driving side is formed with a plurality of parallel protrusions, each provided in the circumferential direction, on the inner peripheral surface at the same pitch as the male screw formed on the outer peripheral surface of the driven side member to form an engaging groove. Members can also be provided. Further, when adopting a structure in which a plurality of protrusions are formed to form an engaging groove, the driven side member is expressed by θ = tan ⁻¹ (P / π · D ₀ ) with respect to the driving side member. It is also possible to increase the contact area of the engaging surface between the ridge and the screw by inclining by the angle θ.
[0026]
【The invention's effect】
Since the present invention is configured and operates as described above, it is possible to realize a linear motor that is small and efficient, can obtain a large stroke and a large force, and can easily design various mechanical devices.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first example of an embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
3 is a cross-sectional view taken along the line BB of FIG.
FIG. 4 is a sectional view showing a second example of the embodiment of the present invention.
FIG. 5 is a sectional view showing the third example.
FIG. 6 is a sectional view showing a fourth example.
FIG. 7 is a view similar to FIG. 3, showing the fifth example.
[Explanation of symbols]
1, 1a, 1b, 1c Linear motor 2, 2a, 2b Motor housing 3, 3a, 3b Nut member 4, 4a Housing body 5 Cover body 6, 6a, 6b, 6c Female thread 7, 7a, 7b Rotor 8, 8a, 8b Stator 9, 9a Bottom plate part 10 Ball bearing 11, 11a, 11b, 11c, 11d Driven side member 12, 12a, 12b, 12c Male thread 13 Bearing 14 Support cylinder part 15, 15a, 15b, 15c Output member 16 Ball bearing 17 Compression Coil spring 18 Bellows 19 Coupling cylinder 20 Ball bearing 21 Outer ring 22 Inner ring 23 Large diameter part 24 Small diameter part 25 Step part 26 Commutator 27 Brush holder 28 Brush 29 Ball bearing 30 Ball bearing 31 Projection

Claims (1)

A drive-side member that is rotatably supported in the motor housing, a rotor fixed to the outer peripheral surface of the drive-side member in the motor housing, and a state in which the inner peripheral surface faces the outer peripheral surface of the rotor A stator fixed in the motor housing and an outer diameter smaller than the inner diameter of the drive side member, and in a state of being eccentric with respect to the drive side member, is rotated and axially moved toward the inner diameter side of the drive side member. A driven-side member supported so as to be displaceable, and a helical thread groove formed on one of the outer peripheral surface of the driven-side member and the inner peripheral surface of the driving-side member; An engaging groove having the same pitch as the thread groove, formed in the circumferential direction on the other peripheral surface of the outer peripheral surface of the driven side member and the inner peripheral surface of the driving side member; A thrust load can be supported on a part of the driven side member. And an output member coupled by gully bearings, linear motors is mutually engaged with a portion of the circumferential direction in the circumferential direction of the part and the engaging groove of the screw groove.

Images