JPH02173768A - Linear driver - Google Patents

Abstract

PURPOSE:To realize cost reduction and fast driving by setting the thrust generated by a linear motor corresponding to a guide member side larger than that generated by another linear motor. CONSTITUTION:The thrust generated by the linear motor 20 corresponding to the guide member side is set larger than that by the linear motor 20 positively. Namely, the thrust generated by the linear motor 20 is made larger than that by the linear motor 10 by the quantity of thrust unbalance (corresponding to the thrust difference between the linear motors 10 and 20 due to some reason) and then a force F0 operates on the part D of a coupling member 30 in a figure to make a driving point O deviates from on the copying member 30, thereby maintaining a state of x>y in the figure. Further, this state is maintained even when the thrusts generated by the linear motors 10 and 20 are set large, so an optical mechanism is driven smoothly at a high speed. Consequently, the cost reduction and speed increase of a copying machine are prompted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a linear drive device for driving an optical mechanism built into a copier or the like using two linear motors.

<Prior Art> Among electrophotographic copying machines, those with a fixed document table use a reflective mirror because the optical path length from the document surface to the photoreceptor drum must be constant regardless of the scanning saga. The scanner is equipped with a linear drive device that moves an optical mechanism including a light source (lamp), etc. in a document scanning direction at a predetermined speed pattern. Such linear drive devices have long been based on a wire pulley mechanism driven by a rotary motor, but due to the presence of an elastic body called a wire in the drive force transmission system, copying machines This is a major obstacle in promoting faster speeds, and from this point of view, 2
A method using a near mortar plate was developed.

This type of linear drive device will be explained with reference to FIG. The movers 12.22 of the linear motors 10.20 (corresponding to the first and second linear motors) are connected by a connecting member 30, while the guide member 40 is arranged so as not to obstruct the optical path. The connecting member 30 is pivotally supported by the linear motor 10. The optical mechanism attached to the upper part of the connecting member 30 is controlled by the linear motor control section 50 mainly composed of a microcomputer to control the thrust generated in the linear motor 10.20. (not shown).

To explain in more detail, the linear motor 10.20 includes a stator 11.21 having a structure in which a large number of permanent magnets are alternately magnetized on the upper surface of the stator yoke, and a three-phase winding on the lower surface of the movable yoke. The gap length between the stator 11.21 and the movable element 12.22 is determined by the guide member 40 provided at the lower part of the connecting member 30 and the rolling roller. It is now regulated by 41.

<Problems to be Solved by the Invention> In the conventional linear drive device described above, the connecting member 30 is not supported pivotally by two guide members placed on both sides of the connecting member 30, but by two guide members placed on one side of the connecting member 30. Since the structure is such that the shaft is supported by one guide member 40, the structure of the guide member is simple, and there is a cost advantage in that the bearing does not require high machining accuracy.

However, if such a guide structure is adopted, there is a drawback that the optical mechanism cannot be moved smoothly if an imbalance occurs in the thrust of the linear motor 1O120. That is, if the gap length changes due to thermal expansion of the mover 12.22 due to heat generated in the three-phase winding during driving, or if there is an error in each part of the linear motor 10.20 during assembly, the stator 11 If there are variations in the permanent magnets of .21, etc., use the linear motor 10.2.
If an unbalance occurs in the thrust force of 0 and the thrust force generated by the linear motor 10 is apparently larger than that of the linear motor 20, smooth movement of the optical mechanism is no longer guaranteed (for details) will be explained in the examples). Moreover, if the thrust of the linear motor 10, 20 is set high, the above-mentioned disadvantage will be further aggravated, and this will be a very serious obstacle in promoting both lower costs and higher speeds of copying machines.

The present invention was devised in view of the above circumstances, and although the same guide structure as the conventional one is adopted, the first and second
An object of the present invention is to provide a linear drive device that can smoothly move a moving object even when the thrust of a linear motor is set high.

<Means for Solving the Problems> The linear drive device according to the present invention has linear drive devices arranged on both sides of a long moving object in the length direction and driving the moving object alternately in the width direction. 1. A second linear motor, a guide member disposed at one end in the longitudinal direction of the object to be moved and pivotally supporting the object to be moved, and a linear motor control for controlling the first and second linear motors. Regarding each thrust generated by the first and second linear motors, the thrust generated by the linear motor corresponding to the guide member side is compared with the thrust generated by the other linear motor. It is set large.

Regarding each thrust generated by the first and second linear motors,
The thrust generated by the linear motor corresponding to the guide member side is thicker than the thrust generated by the other linear motor (
Once set, no matter what condition the moving object is driven in,
Based on the narrow guide principle defined in the examples (x
The condition regarding Xy is always maintained as x>y.

<Embodiment> Hereinafter, one embodiment of the linear drive device according to the present invention will be described with reference to the drawings. Figures 1 (a) and (b) are plan and side views showing the schematic structure of the linear drive device, and Figures 2 and 3 show the forces acting on the connecting members necessary to explain the principle of the narrow guide. FIG. 2 shows the case according to the conventional example, and FIG. 3 shows the case according to the present example.

The linear drive device described here is installed in an electrophotographic copying machine, and its schematic structure has already been described in the prior art, so the explanation of the overlapping parts will be omitted, but the explanation will be the same. The insufficient linear motor control section 50 will be explained below.

The linear motor control unit 50 is a control circuit mainly composed of a microcomputer called a so-called software servo. A basic configuration that compares the position data of the optical mechanism given by the output of the provided linear encoder 51, and generates each excitation current to be supplied to the mover 12.22 of the linear motor 10.20 according to the comparison result. It becomes. This basic configuration is the same as the conventional one. However, even if commands suitable for moving the optical mechanism by a predetermined amount are issued to the linear motors 10 and 20 under the same conditions, the magnitude of the excitation current supplied to the mover 22 of the linear motor 20 is By increasing the excitation current supplied to the mover 12 of the motor 10,
The thrust force generated by the linear motor 20 is set to be larger than that of the linear motor 10.

In the linear drive device configured as described above, even if the thrust of the linear motor 10.20 is set to be large (
The optical mechanism can be smoothly moved based on the narrow guide principle described later. Before explaining this operating principle, let us explain the reason why the optical mechanism cannot be moved smoothly in a conventional linear drive device when the thrust of the linear motor 10.20 is set to a large value. Refer to and explain.

In the case of the conventional example, the thrust forces generated in the linear motors 10 and 20 are usually set to be equal. However, in practice, linear motors 10.2
The two thrust forces may not be exactly the same due to various factors, and the thrust force generated by the linear motor 10 may be larger than the other thrust force. FIG. 2 shows such a state, in which a force F0 corresponding to the difference in thrust between the linear motors 10 and 20 is acting on a portion A in the figure of the connecting member 30. When this side F0 acts on the opposite side of the guide member of the connecting member 30, the bearings of the connecting member 30 and the guide member 40 will exert a force on the guide surfaces B and C, and as a reaction, force F and frictional force μF ( μ is a coefficient of friction), and this resultant force F acts on both parts shown in the figure, respectively. However, X, which is also shown in the figure, represents the distance between the guide member 40 and the driving point O where the vectors of the resultant forces F generated at both parts shown intersect, while y represents the distance between the guide member 40 and the force F0. It represents the distance between the connecting member 30 and the part A in the figure.

Here, the principle of the narrow guide is a condition regarding x and y that makes it possible to smoothly move the connecting member 30, that is, the optical mechanism, on the condition that this type of guide structure is adopted. This is a well-known matter in terms of statics. That is, when y≧X, the optical mechanism cannot move smoothly, but when X>y, the optical mechanism can move smoothly.

That is, in the conventional linear drive device, if the thrust force generated in the linear motor 10.20 becomes unbalanced due to some factor and the state shown in FIG. 2 occurs, y≧
X, and the optical mechanism cannot be moved smoothly. In addition, if the thrust generated by the linear motor 10.20 is set larger, the linear motor 10.2
The unbalance of thrust generated at zero becomes significant, and the above-mentioned disadvantages are further aggravated.

Therefore, in the case of the linear drive device according to the present invention,
Among the linear motors 10 and 20, the thrust of the linear motor 20 corresponding to the guide member side is made larger than the other one, so that the state of x>y is maintained in any case, thereby making the optical mechanism smooth. So that you can move around. That is, as shown in FIG. 8, the thrust generated by the linear motor 20 compared to the linear motor IO is reduced by the amount of thrust imbalance (the difference in thrust between the linear motor 10 and the linear motor 20 caused by some factor). If the force F0 is increased by an amount corresponding to
0, and the state of x>y is maintained.

Moreover, this state does not collapse even when the thrust generated by the linear motors 10 and 20 is set to a large value, so that the optical mechanism can be driven smoothly and at high speed.

Furthermore, if errors occur in each part when assembling the linear motor 10.20, or if thermal expansion occurs in the mover 12.22 etc. due to heat generated by the three-phase winding during driving and the gap length changes, the stator Even if there are variations in the magnetic properties of the permanent magnets in 11.21, the optical mechanism can be driven smoothly, so high assembly precision is not required, and inexpensive parts can be used. This is of great significance in promoting both higher speed and lower cost copying machines.

Note that the linear drive device according to the present invention is not only applicable to copying machines, but also means to increase the thrust of the linear motor corresponding to the guide member by changing the number of windings of the mover and the magnetic flux density of the stator. Alternatively, the magnetic permeability of the movable yoke of the movable element may be increased, or the gap length may be decreased. Furthermore, it goes without saying that the structure and type of the linear motor and guide member are not limited.

<Effects of the Invention> As described above, in the case of the linear drive device according to the present invention, even if the thrust generated by the first and second linear motors is set to a large value, based on the narrow guide principle, <x % y
Since the configuration is such that the condition for x > y is always maintained, even with this type of guide structure,
A moving object can be moved smoothly and at high speed. Therefore, it is of great significance in promoting both lower costs and higher speeds of devices.

[Brief explanation of the drawing]

FIGS. 1 and 3 are diagrams for explaining an embodiment of the linear drive device according to the present invention, and FIGS. 1(a), (
b) is a plan view and a side view showing the schematic structure of the linear drive device;
Figures 2 and 3 are vector diagrams showing the forces acting on the connecting members necessary to explain the principle of the narrow guide. Figure 2 shows the case of the conventional example, and Figure 3 shows the case of the present example. It shows. 10, 20...Linear motor 40...Guide member 50...Linear motor control unit Patent applicant Sharp Corporation

Claims (1)

[Claims] (1) First and second linear motors that are arranged on both sides of a long moving object in the length direction and drive the moving object alternately in the width direction, and the length of the moving object. The guide member is disposed at one end of the direction and pivotally supports the moving object, and a linear motor control section that controls the first and second linear motors. A linear drive device characterized in that, regarding each thrust generated by a linear motor, the thrust generated by the linear motor corresponding to the guide member side is set to be larger than the thrust generated by the other linear motor.