JP2530198B2 - Stroke type step motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a step motor for converting a rotational motion of a rotor into a linear motion via a meshing mechanism, and is particularly stable against a high load. The present invention relates to a stroke type step motor having a built-in switch that can be operated and that can easily detect the position of a linear motion member.

(Prior Art) Since this type of stroke type step motor efficiently converts the rotational force of the rotor into a linear motion, it is an important issue to suppress the axial load of the rotor shaft as much as possible. As disclosed in Japanese Utility Model Laid-Open No. 56-54636, a male shaft of a stepper motor that moves in a straight line has a male screw formed on the outer peripheral surface thereof, and is provided with a detent structure so that it can slide on the axis. ing. A rotor rotatably supported by a pair of ball bearings has a female thread formed in a center hole of the rotor that meshes with a male thread of the rotor shaft, and the rotor shaft rotates so that the rotor shaft moves in the axial direction. Make a linear motion. Therefore, when a high load is applied to the rotor shaft, an axial load is applied to the rotor from the meshing portion of the screw, and the inner ring of the ball bearing is pressed. Here, the purpose of the use of the pair of ball bearings is to efficiently transmit the rotational force of the rotor to the rotor shaft while receiving the axial load.

Further, since a step motor generally obtains a rotation angle proportional to a digital amount, it is suitable for positioning control. For example, in the stroke type step motor described above, the rotor shaft position is detected and the rotor due to the excessive load in the axial direction described above is used. There are systems that require detection of the out-of-step phenomenon. These detection methods are dealt with by detecting a rotation pulse signal using a rotary encoder as disclosed in JP-A-61-185096.

(Problems to be Solved by the Invention) In the above-mentioned conventional technique, although the ball bearing supporting the rotor is superior in durability to other bearings, the load acts on the inner ring of the ball bearing, so the load There is a problem that the ball portion of the ball bearing portion may be worn out depending on the size, rotation speed and operation frequency of the ball bearing and cannot withstand for a long time. Moreover, since the fitting portion of the rotor is located on the side of the center hole of the inner ring and the center hole of the fitting portion has the rotor shaft, the ball bearing has to be large in size.

For example, even if a rotary encoder is mounted to detect the position of the rotor shaft, the detection accuracy may be deteriorated due to the durability problem of the ball bearing. Further, due to the large size of the ball bearing, problems occur in securing a space for mounting the rotary encoder, mounting structure, mounting accuracy, and the like. Further, the ball bearing and the rotary encoder for detecting the position described above are considerably expensive at present.

An object of the present invention is to use a plain type bearing without using a ball bearing, to obtain stable operation under a high load, and to open and close by a member that moves linearly without using a rotary encoder for position detection ( (EN) To provide a stroke type step motor having a switch mechanism that operates (ON / OFF).

[Configuration of the Invention] (Means for Solving the Problems) The above object is to provide a portion in which a rotor rotates on the coaxial center of a shaft press-fitted in a housing of a step motor,
By a switch slider that is integrally provided with a portion where the rotor screw moves in the axial direction via a meshing portion, and further cooperates with a slider mechanism that transmits the axial movement of the rotor screw to the outside via a ball bearing. This is achieved by providing an ON-OFF switch mechanism in the outer peripheral direction of the rotor screw.

(Operation) According to the present invention, a portion where the rotor is supported by a pair of plain bearings and rotates, and a female screw provided in a center hole of the rotor screw are engaged with each other on a coaxial center of a shaft that is press-fitted and fixed in the housing of the step motor. The rotor screw has an outer peripheral shape that is a polygonal shape, and a polygonal hole that is similar to the polygonal shape and that is slightly larger is provided on the inner peripheral side of the rotor. The rotation of the rotor screw causes the rotor screw to make a straight swiveling motion.
Further, an inner ring of a ball bearing is press-fitted to a part of the outer periphery of the rotor screw, and a slider is press-fitted to the outer ring of the ball bearing so that the straight forward turning motion of the rotor screw gives an external load to the slider, for example. For example, the slider can perform only linear movement. As a result, even if a high load acts on the slider, a load is applied to the meshing portion, and the rotor rotating on the shaft is not affected by an external load. Further, a simple switch mechanism which is turned on and off by a switch slider which linearly cooperates with the slider by a part of the slider or the ball bearing outer ring is provided in the outer peripheral direction of the rotor screw to detect the position of the slider and the step motor. It is possible to combine the detection of abnormal operation.
The initial position of the slider of the step motor can be detected by operating the step motor in the direction in which the switch mechanism is turned on during the initial operation and moving the slider until the switch mechanism pushes the switch mechanism to turn it on. For example, if the system is reset by the level change that the switch mechanism turns on, the normal positioning control becomes possible from that point.
Further, after that, the slider is operated for x pulses in the direction in which the switch mechanism is turned off, then the direction is reversed, and the number of operation pulses until the switch mechanism is turned on again is counted to detect the normal or abnormal operation of the step motor. Can be done.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional view of a stroke type step motor showing an embodiment according to the present invention. By the rotating magnetic fields of the coils 15a and 15b in the steps 14a and 14b, N is generated in the circumferential direction.
A rotor 3 having magnets 2 magnetized to have a plurality of poles and S poles alternately is a pair of plain bearings press-fitted to the center position of the rotor 3 on the outer circumference of a shaft 4 press-fitted and fixed to the end cover 1. It is supported by 6a and 6b and rotates. The magnet 2 and the rotor 3 are integrally formed, and the positional relationship between the rotor 3 and the shaft 4 in the axial centerline direction is such that the thrust washer 5a, which is interposed on the end surface of each plain bearing 6a, 6b, 5b, and the shaft 4 is fitted with a stop ring 7 for preventing the rotor 3 from coming off. Polygonal holes, in this example, hexagonal holes 8 are integrally formed in the rotor 3, and a rotor screw 13 is provided on the inner peripheral side of the hexagonal holes 8.
The outer periphery of the rotor screw 13 has a similar hexagonal shape that is slightly smaller than the hexagonal hole 8 of the rotor 3, and a female screw is formed in the center hole thereof so that the rotor 3 of the shaft 4 rotates. The male screw and the meshing mechanism 12 are integrally provided on the extension of the coaxial center of the portion.
As a result, when the rotor 3 is rotated, the rotor screw 13 is linearly swung by the hexagonal phase fitting and the meshing mechanism 12. On the other hand, the inner ring of the ball bearing 9 is press-fitted at a position facing a side opposite to the rotor 3 at a part of the outer periphery of the rotor screw 13, and the slider 10 is press-fitted to the outer ring of the ball bearing 9 to fit the rotor. If the linear turning motion of the screw 13 gives an external load to the slider 10, for example, the slider 10 can perform only linear motion. Next, a switch mechanism 25 is provided on the outer peripheral portion of the portion of the rotor 3 where the magnet 2 is not attached, and the switch mechanism 25 has a movable plate 18a having a contact point 17a.
A fixed plate 18b having a contact point 17b and an insulator 16 for insulating and fixing the two plates are housed and fixed in the cover 11. A switch slider 19 for moving the movable plate 18a is configured to co-operate by linear movement of the slider 10 or the outer ring of the ball bearing (in the embodiment, the outer ring of the ball bearing 9). FIG. 2 is a sectional view showing the switch mechanism 25.
The movable plate 18a and the fixed plate 18b have a substantially semicircular shape and are separately fixed to the insulator 16 via rivets 23. The protrusion 22 is formed on the movable plate 18a.
Is formed and is fitted into the groove portion 21 of the switch slider 19. The switch slider 19 has the groove portion.
A protrusion 20 that abuts the slider 10 or the outer ring portion of the ball bearing 9 is formed on the surface opposite to 21, and the slider 10 co-acts with the linear motion described above to move the movable plate 18a to make contact. The switch mechanism 25 is turned on by pressing the 17a and 17b into contact with each other. In Fig. 2, the switch mechanism 25 is OFF.
Shows the state, and at this time, the switch slider 19
Is moved to the left side in the figure by the elasticity of the movable plate 18a and is pressed against the insulator 16. FIG. 3 is a view taken in the direction of arrow A in FIG. 2, and the insulator 16 is provided with a guide portion 24 for allowing the switch slider 19 to make a smooth linear movement. Next, the operation of this stroke type step motor will be described. In FIG. 1, the slider 10
If a high external load such as a spring pressure is applied to the
A load is applied to the screw meshing mechanism 12 of the rotor screw 13 and the shaft 4 via the ball bearing 9, but the shaft 4 is press-fitted and fixed to the end cover 1 so that the meshing mechanism 12 actually receives the load. As a result, the rotor 3 rotating on the shaft 4 is not affected by the external load. Further, the screw meshing mechanism 12 has a meshing error due to each screw precision error, so-called backlash, and the backlash backlash causes an eccentric force due to an external load to cause an axial center of the rotor screw 13 with respect to an axial center of the shaft 4. However, by setting a large hexagonal fitting size of the rotor screw 13 and the rotor 3, it is possible to absorb the deviation of the axial center of the rotor screw 13, so that the rotor can be loaded against a high load. No. 3 enables smooth and stable rotation. Next, FIG. 4 is a longitudinal sectional view showing a state in which the switch mechanism 25 of FIG. 1 is turned off. When the rotor screw 13 moves to the right on the axial center line, the slider 10 or the outer ring of the ball bearing 9 contacts the protrusion 20 of the switch slider 19, and the rotor screw 13 further moves to the right. , The movable plate 18 that cooperates with the switch slider 19
The contact 17a of a contacts the contact 17b of the fixed plate 18b, and the switch mechanism 25 is turned on. The first
The figure shows this state. When the system is reset by the level change in which the switch mechanism 25 is turned on, that point is the origin position of the rotor screw 13 and the slider 10, and regular positioning control is possible from that point. Further, after that, the step motor is operated to move the rotor screw 13 to the left by the amount of x pulses in the direction in which the switch mechanism is turned off, and then the moving direction is reversed and the operation pulse amount until the switch mechanism 25 is turned on again. By counting and collating, the normal or abnormal operation of the step motor can be easily detected.

As described above, in the present invention, the high operating force and the eccentric force generated by the sudden change of the load are received by the screw meshing mechanism of the rotor screw and the shaft, so that the action of these forces directly on the rotor becomes extremely small. Therefore, a pair of plain type bearings that are small and inexpensive can be used as the bearings that support the rotor. Further, by incorporating a simple switch mechanism in the motor, it is possible to realize a stroke type stepping motor that can easily perform rotor screw positioning control and abnormal operation detection.

EFFECTS OF THE INVENTION According to the present invention, stable operation can be obtained against a high load without using an expensive ball bearing as a bearing for supporting the rotation of the rotor, and an expensive rotary encoder and complicated detection associated therewith can be obtained. The position of the rotor screw can be detected without the need for a circuit, and a small-sized, inexpensive stroke-type step motor with good assembling can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a stroke type step motor showing an embodiment according to the present invention, FIG. 2 is a sectional view showing a switch mechanism, FIG. 3 is an arrow A view of FIG. 2, and FIG. It is a longitudinal cross-sectional view showing the switch mechanism OFF in the figure. 1 ... End cover, 2 ... Magnet, 3 ... Rotor, 4 ...
… Shaft, 5a, 5b …… Thrust washer, 6a, 6b …… Plain bearing, 7 …… Stop ring, 8 …… Hexagonal hole, 9
...... Ball bearing, 10 ...... Slider, 11 ...... Cover, 12 ...... Mating mechanism, 13 ...... Rotor screw, 14a, 14b ...... Stator,
15a, 15b …… coil, 16 …… insulator, 17a, 17b …… contact, 18a
...... Movable plate, 18b ...... Fixed plate, 19 ...... Switch slider, 20 ...... Projection part, 21 ...... Groove part, 22 ...... Projection part,
23 …… Rivet, 24 …… Guide part, 25 …… Switch mechanism

Claims (1)

(57) [Claims] 1. A stroke type step motor that converts the rotation of a rotor of a step motor into a linear motion, supports the rotation of the rotor, has one end press-fitted and fixed in a housing of the step motor, and has a male screw in the direction of the other end. A shaft to be formed, a rotor screw that makes a linear swivel motion by meshing with the male screw in the axial direction of the rotation by the rotation of the rotor, a slider that transmits the motion of the rotor screw to an external load through a ball bearing, and the slider Alternatively, a stroke type stepping motor is provided with a switch slider that cooperates with the linear motion of the rotor screw via the outer ring of the ball bearing, and a switch mechanism that operates by the linear motion of the slider.