JPH0793838B2 - Stepping motor positioning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] The present invention relates to a positioning method for a cam driving stepping motor that positions a cam follower by bringing it into contact with a stopper and causing the stepping motor to step out, and a position of the cam follower that rebounds when the stopper comes into contact. For the purpose of preventing deviation, stoppers are provided at two positions of a cam driven by a stepping motor, and the stepping motor is rotated in one direction to bring a cam follower into contact with one stopper,
Next, the stepping motor is rotated in the reverse direction by a predetermined number of steps corresponding to the distance between the stoppers to align the cam follower with the position of the other stopper, thereby performing the initial positioning of the stepping motor.

[Industrial application field]

The present invention relates to a positioning method for a stepping motor for driving a cam, which performs positioning by bringing a cam follower into contact with a stopper and causing a stepping motor to step out.

In the color ribbon shift mechanism of a multicolor printer,
Ribbon shift is performed by cam means driven by a stepping motor. In this case, it is necessary to accurately align the initial position of the stepping motor, which serves as a reference for aligning each shift position of the ribbon, to achieve a highly reliable ribbon shift operation.

[Conventional technology]

In the conventional positioning of a stepping motor for driving a cam, at the time of initializing, the stepping motor is rotated by a certain amount in one direction, and a cam follower is brought into contact with a stopper provided on the cam so that the motor is stepped out of position.

[Problems to be solved by the invention]

In the conventional stepping motor positioning method, when the cam follower comes into contact with the stopper, the cam follower may rebound and cause a positional shift. If the initial position is deviated as described above, there is a problem that the position deviated state naturally continues even if the positioning is controlled by calculating the number of steps thereafter.

In order to solve such a problem, conventionally, a method such as providing a load member such as a spring to a driven member by a cam follower to prevent rebound, or attaching an encoder to a motor to perform positioning has been performed. In such a method, the structure is complicated, the number of parts is increased, and there is a problem in cost.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a positioning method for a stepping motor that prevents displacement of the cam follower due to bounce when the cam follower is brought into contact with a stopper to step out the motor. And

[Means for solving problems]

According to the present invention, stoppers are provided at two positions of a cam driven by a stepping motor, the stepping motor is rotated in one direction to bring a cam follower into contact with one stopper, and then the stepping motor is moved. The stepping motor is initially positioned by rotating the motor in the opposite direction by the number of steps corresponding to the distance between the stoppers and aligning the cam follower with the position of the other stopper.

[Work]

First, the stepping motor is rotated in one direction to bring the cam follower into contact with one of the stoppers to cause step out. Next, the motor is reversely rotated by the number of steps corresponding to the distance between both stoppers. When the cam follower is repelled by the first stopper, the cam follower is reversely rotated by a predetermined number of steps to come into contact with another stopper and be positioned at this stopper. When the cam follower is not repelled by the first stopper, the cam follower is reversely rotated by a predetermined number of steps to stop and be positioned at another stopper position.

〔Example〕

FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention when an eccentric cam is used. As shown in FIG. 2, the eccentric cam 3 is mounted on the output shaft 2 of the stepping motor 1 fixed to the support frame 7. This eccentric 3
Is formed with a spiral cam groove 4 from the central shaft 2 toward the outside. A shaft 6 is fixed to the support frame 7, and a drive lever 5 is rotatably attached to the shaft 6. The drive lever 5 is provided with a pin (cam follower) 11 (FIG. 1) which is engaged in the cam groove 4 of the eccentric cam 3. An operating portion 8 is formed at the tip of the drive lever 5. The inner end of the spiral cam groove 4 is the first stopper.
A second stopper 4b is formed on the outer peripheral part of the outer peripheral portion 4a.
The rotation angle between the first and second stoppers 4a and 4b is 540 ° in this embodiment. Further, the step motor 1 rotates the eccentric cam 3 180 degrees in 30 steps.

The positioning principle of this embodiment will be described below. First, the stepping motor is rotated 90 steps to rotate the eccentric cam 3 in the direction of arrow B. As a result, the pin 11 comes into contact with the second stopper 4b regardless of the position in the cam groove 4. For example, when the drive lever is at the position of 5a and the pin 11 is at the position shown by the dotted line, the drive lever gradually rises due to the rotation of the eccentric cam 3 in the direction of the arrow B, and when the pin comes into contact with the second stopper 4b, the drive lever moves to 5b. Is reached, and the stepping motor goes out of step. Next, the stepping motor is reversely rotated by 90 steps to rotate the eccentric cam 3 in the direction of arrow A one and a half rotations. This causes the drive lever to reach position 5c and pin 11
Is determined by the position of the first stopper 4a at the inner end of the cam groove 4.
That is, even if the lever bounces and the pin 11 bounces at the second stopper 4b in the first operation, the pin 11 abuts the first stopper 4a and stops in the next operation. The probability that the lever bounces and the pin 11 bounces is experimentally about 1/300. Therefore, the lever bounces at the first movement and the first stopper 4a at the next movement.
The probability that the lever will spring is 1/300 × 1/300 = 1/9000
It is 0 and can be almost ignored. If the lever does not spring at the second stopper 4b in the first operation, the pin 11 does not abut the first stopper 4a in the next operation, and the pin 11 does not just contact the first stopper 4a.
Stop at position 4a. That is, the distance between the stoppers 4a and 4b is set to be slightly longer than the length of 90 steps corresponding to one and a half rotations within the allowable positioning error range. After reaching the position of the first stopper 4a, the eccentric cam 3 may be rotated again in the direction of the arrow B to repeat the positioning operation to enhance the reliability.

An application example of the present invention is shown in FIG. This example shows an ink ribbon shift mechanism of a multicolor printer. Reference numeral 8 is a platen, 10 is a print head, and a ribbon cartridge 9 is pivotally attached to a shaft 12 as shown by an arrow E. The eccentric cam 3 rotates as indicated by an arrow C to swing the drive lever 5 as indicated by an arrow D. As a result, the ribbon cartridge 9 swings as shown by the arrow E, and the desired ribbon faces the platen 8.
In this case, since the initial position of the stepping motor surely corresponds to the predetermined initial position of the lever 5, the drive control based on the number of steps ensures the predetermined shift position (for example,
Ribbon cartridges can be placed at 180 ° rotations every 30 steps (4 positions).

〔The invention's effect〕

As described above, in the stepping motor positioning method according to the present invention, stoppers are provided at two locations on the cam, one of the stoppers is brought into contact with the cam follower, and then the motor is reversely rotated by a predetermined number of steps and the other is rotated. The cam follower is positioned at the stopper position. Therefore,
Positional displacement due to the bouncing of the cam follower at the time of contact with the stopper is almost eliminated, and highly reliable positioning is achieved with a simple structure without cost and without imposing an excessive load on the motor.

[Brief description of drawings]

FIG. 1 is an explanatory view of the operating principle of the embodiment of the present invention, FIG. 2 is an explanatory view of the mechanism of the embodiment of the present invention, and FIG. 3 is an explanatory view of an application example of the present invention. 1 ... Stepping motor, 3 ... Excene cam, 4 ... Cam groove, 4a, 4b ... Stopper, 5 ... Drive lever, 11 ... Pin.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI G05B 19/18 (56) References JP-A-62-239204 (JP, A) JP-A-62-159135 (JP , A) JP 62-103703 (JP, A) JP 60-61802 (JP, A) JP 61-199894 (JP, A) Actual development JP 62-57805 (JP, U)

Claims (2)

[Claims] 1. A cam (3) driven by a stepping motor (1) is provided with stoppers (4a, 4b) at two positions, and the stepping motor (1) is rotated in one direction to move a cam follower (11). The stepping motor is brought into contact with one stopper (4b), and then the stepping motor is rotated in the reverse direction by a predetermined number of steps corresponding to the distance between the two stoppers to move the cam follower (11) to the position of the other stopper (4a). A stepping motor positioning method, wherein the stepping motor (1) is initially positioned by aligning the stepping motor with the stepping motor. 2. The stepping motor according to claim 1, wherein the cam is an eccentric cam (3) having a cam groove 4 formed in a spiral shape from the vicinity of the rotating shaft toward the outside. Positioning method.