JPH0311971A - Linear reciprocating shift scanner - Google Patents

Abstract

PURPOSE:To improve reliability by serving the shaft for regulating the motion of scanning system as the yoke in a magnetic circuit. CONSTITUTION:A motion regulating shaft 3 is arranged in the central section of a C-type cylindrical magnet 1 with the axial direction being matched each other. A non-magnetic coil holder 5 is arranged on the shaft 3 through a bearing 4 then coils 6a-6f are applied thereon thus producing a three-phase motor 6. Magnetic field detecting elements 7a-7c are fixed in the gap between adjoining coils on the outer circumference of the holder 5 in order to detect magnetic field and to perform switching control of excitation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to devices that perform linear reciprocating movement, particularly those that use a shaft to regulate movement (for example, the optical system unit of a copying machine or the head of a printer). etc.) related to the drive mechanism.

Conventionally, scanning devices that perform linear reciprocating motion use a shaft to regulate movement, use this shaft as a guide for scanning, and use a rotary motor as the drive source, which is driven via a wire booby mechanism. It was transmitting power. However, in response to the recent demand for higher speeds, simply increasing the power of the rotary motor requires an elastic member (wire pulley mechanism) to be inserted into the transmission mechanism, which causes transient vibrations in the scanning system. could not be provided. To solve this problem, a method using a linear motor in the drive system has been proposed.

Problems to Be Solved Today An example of a configuration using a linear motor that has been proposed in the past is shown in FIG. Here, 20 is a magnet, 21, 22, and 23 are coils, and 24 is a movable yoke made of a magnetic material. The scanning system equipped with this linear motor performs linear reciprocating movement in the direction of the arrow in the figure while controlling the gap between the coil and the magnet, while being restricted in movement by shafts and the like disposed around it.

In the above-mentioned conventional linear motor structure, a magnetic circuit as shown in FIG. 4(C) is formed between the multi-pole magnetized magnet 20 and the mover yoke 24, and current is appropriately passed through the coils 21.2223. The linear motor operates by switching. The problems at this time are (1) Cogging force of the mover yoke, (2) Deflection of the shaft that restricts movement due to the attraction force between the magnet and the mover yoke, and (3) The drive system is mounted on the scanning system. One example of this is an increase in the weight of the scanning system. These solutions include (1), (2)
(1) Reduce cogging force by optimizing the shape of the mover yoke.

(2) The linear motors are arranged symmetrically with respect to the scanning direction so that the suction forces cancel each other out, resulting in a two-axis driving force type.

However, for (1), the cogging force does not become zero, and for (2), the burden on the linear morph thrust increases due to the increase in self-weight, and for (3), it is equivalent. No solution has been found, and if the mover yoke 23 is omitted in the conventional configuration example, an appropriate magnetic circuit cannot be constructed, and although weight reduction can be achieved, the thrust of the near motor will inevitably be significantly reduced.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a linear reciprocating scanning device that can reduce the weight of a linear motor without increasing the number of components.

The present invention provides a linear reciprocating scanning device comprising a shaft that regulates the direction of movement, that is, the direction of linear reciprocating movement, and a linear motor that moves in the axial direction of this shaft. The magnet shape on the stator side is multipole magnetized to have a C-shaped cross section with a part of the cylindrical side wall cut out, and the shaft is placed in the center of the C-shaped magnet on the movable side, and the shaft is slidable on the shaft. The device forms a radial magnetic flux distribution between the stator and mover to form a linear reciprocating scanning device.

In the above configuration, as can be seen by comparing Figures 1(d) and 4(C), ■Mover yoke 23, which is an essential element in the conventional device.
Even if the magnetic circuit is omitted, the magnetic flux distribution necessary for operation as a linear motor can be obtained because the magnetic circuit is constructed between the C-shaped magnet and the movement regulating shaft.

(2) For the above reasons, the movable element yoke can be omitted, so the weight of the scanning system can be reduced.

(2) Since the attractive force of the C-shaped magnet acts in a radial direction with respect to the axial center of the shaft, a large amount of attractive force can be offset, and the amount of deflection of the shaft can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall configuration diagram of the present invention, in which (a) is a side view and (a) is a side view;
b) is a front view, (C) is a top view, and (d) is a ζn flux distribution state diagram. In this figure, the C-type magnet l is shown in Figure 1(e).
As shown in the figure, a cylindrical magnet with multiple poles attached at a constant pitch t in the axial direction becomes the stator of the linear motor. is C-shaped, and a movable element, which will be described later, reciprocates in the axial direction within this notch 2.

A movement regulating shaft 3 is installed in the cylindrical center of the C-shaped magnet 1 with its axis aligned with the axis of the cylinder, and a coil holder 5 made of a non-magnetic material is connected to the movement regulating shaft 3 via a bearing 4. is provided. On the outer periphery of the coil holder 5, coils 6a to 6f are arranged in a determined pinch and positional relationship to correspond to the magnetization pitch L of the C-type Eff stone 1 and to correspond to the 6 coils of the 3-phase motor in this embodiment. It's wrapped. Magnetic field detection elements 78 to 7c are attached to the outer periphery of the coil holder 5 in gaps between adjacent coils, and detect the passing magnetic field to form a signal for controlling switching of excitation. The side edge of the coil holder 5 is connected to the C-shaped magnet 1.
It is led out from the notch 2 of the C-shaped magnet 1 and becomes a support 8 on which a driven body (not shown) such as an optical system unit or a printer head is mounted.

One end of the support 8 is integrated with the coil holder 5 as described above, but high-speed linear reciprocating movement and high magnification are required, as in the optical system scanning unit of a copying machine shown in FIG. As a drive mechanism for the device, a linear motor is provided on the other end of the support 8, with a similar C-shaped magnet as a stator and a coil holder with a coil wound as a mover, and the support 8 connects the linear motors on both sides. It may be configured as follows. By arranging the linear motors at both ends of the scanning system in this manner, it becomes possible to drive the center of gravity of the scanning system, allowing high-speed and highly accurate control.

In addition, the copying machine shown in FIG. 2 shows a structure in which two optical scanning units having the same structure move back and forth in a straight line while sharing the shaft 3 as a movement regulating shaft.
Even if the number of drive systems increases relative to the scanning system, there is no need for a mover yoke like in the conventional structure, so as a result, the weight of the drive system does not increase compared to the conventional example, and the motor generated The thrust of the engine can be effectively utilized.

In addition, as shown in the above embodiment, the near motor may be provided only on one end side of the support body 8, and the other end may be constructed as a slidable structure that allows the support body 8 to move back and forth in a straight line.

In FIG. 1, the position/speed detection mechanism and control mechanism of the linear motor are not shown.

In the above configuration, the magnetic circuit for driving the linear motor forms a radial direction with respect to the axial center between the cylindrical C-shaped magnet l and the coils 68 to 6f on the coil holder, as shown in (d). The linear motor reciprocates in the direction of arrow P by energizing the coils 6a to 6f and appropriately switching the excitation using signals from the magnetic field detection elements 73 to 7c as in the conventional linear motor. In the structure of this embodiment, the magnetic flux is distributed radially, so that the movable element yoke, which was necessary in the conventional structure to form a magnetic circuit, is no longer necessary. Therefore, the weight of the drive system can be reduced, the cogging force can be reduced to zero, and a high-speed, high-precision linear motor can be provided. Furthermore, regarding the deflection of the shaft due to the attractive force of the magnet-mover yoke, which was a problem in the conventional example, since the attractive force acts in a radial direction with respect to the axial center of the shaft, the amount of cancellation of the bow absorption force increases, resulting in As a result, the amount of deflection of the shaft is reduced, and the movement accuracy of the scanning system is improved.

Although the near motor shown in the above embodiment is a 3-phase motor with 6 coils, it can also be applied to a 3-phase motor with 3 coils, a 2-phase motor with 4 coils, a 2-phase motor with 2 coils, etc. The linear motor according to the present invention can also cope with the required thrust force and shape limitations of the linear motor.

As is clear from the above explanation, according to the present invention, the shaft that regulates the movement of the scanning system also serves as the yoke that constitutes the magnetic circuit of the linear motor, thereby reducing (i) cogging that occurs in the linear motor; The force can be reduced to zero, enabling high-precision control. (11) By reducing the number of parts in the operating system, its own weight can be reduced, the capacity can be increased, and high-speed performance can be given to the operating system. iii) Magnet-yoke (shaft in the present invention)
To provide a high-speed, high-precision linear near motor, which has effects such as a small amount of deflection of the shaft that regulates movement and facilitates gap management between the magnet and the yoke, since a large amount of offset of the attractive force between the magnets and the yoke can be obtained. This makes it possible to significantly improve the reliability of precision equipment drive systems.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and FIG. 1 (al is a side view, FIG. 1(b) is a front view, FIG. 1(C) is a top view, and FIG. 1(d) is a magnetic flux Distribution state diagram, FIG. 1(e) is an axial sectional view, FIG. 2 is a top view of a copying machine optical system scanning unit showing an example of application of the present invention, and FIG. 3 shows various forms of the mover of the near motor. 4 shows a conventional device. 1--C-shaped magnet, 2-notch 3--movement regulating shaft 5-coil holder 68-6
f--coil, 7a~7cm magnetic field detection element.

Claims (1)

[Claims] (1) In a linear reciprocating scanning device in which the shaft and the shaft are used as guides to restrict movement in the axial direction of the shaft by the driving force of a linear motor, the magnetic circuit of the linear motor moves the magnet shape on the stator side to the cylindrical side wall. C with notched part
A linear reciprocating scanning device characterized in that the C-shaped magnet is magnetized with multiple poles, and the movement regulating shaft is arranged at the center of the C-shaped magnet.