JPS6356640A - Magnification varying device for copying machine - Google Patents

Abstract

PURPOSE:To smoothly move a mirror by providing an eccentric cam which is driven and rotated by a driving source for moving a lens and moves the mirror, and maximizing the radius of the cam when the mirror is set at an unmagnification position. CONSTITUTION:When desired power data is inputted from an operation panel, the specific number of pulses are inputted to a stepping motor 20, which is rotated as specified to move a through lens 14 to the position of desired power through a driving 21, a 1st intermediate gear 22, a driving pulley 31, and a wire 34. Further, the rotation of the 1st intermediate gear 22 is transmitted to the eccentric cam 41 through a 2nd intermediate gear 23 and a 3rd intermediate gear 24 and further a mirror holder 39 is moved in an optical-axis direction through a cam follower 54, an arm 52, and a mirror cover 44 to position the mirror 15 at a position suitable to the desired power. Further, the mirror holder 49 rotates by its rotation under the guidance of a slanting guide hole 72 formed in a support plate 42 to set the mirror 15 at a specific rotational position, so the position of incidence on a photosensitive drum is held constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnification changing device for a copying machine.

(Prior Art) In general, this type of magnification changing device uses a through lens that focuses the light beam from the original surface on the optical axis in accordance with the change in magnification, taking into account space efficiency or economic efficiency inside the copying machine. At the same time, a device is employed that moves a mirror that reflects the light beam from the through lens toward the photosensitive drum in order to correct the optical path length.

As an example of this type of device, for example,
The one described in Publication No. 36 is known. In this conventional example, as shown in Fig. 7, a stepping motor (drive source) a
The wire b is moved by the rotation of the through lens C.
while moving the stepping motor a onto the optical axis.
The eccentric cam d is rotationally driven by the rotation of the eccentric cam d, and a mirror f having a cam follower e that is in pressure contact with the eccentric cam d is moved. In FIG. 7, g is a tension spring for pressing the cam follower e against the eccentric cam d.

(Problems to be Solved by the Invention) According to the above-mentioned conventional example, for example, when the magnification range is x0.
In the case of a large range such as 5 to x2.0, the slope of the cam curve of the eccentric cam d becomes large as shown in FIGS. 6 and 7, and the cam radius also becomes large. Therefore, the position where the slope of the cam curve is maximum (for example, the position of ×0.5)
Let T be the transmitted torque of the eccentric camshaft when cam follower e contacts S, and let NX be the component force in the optical axis direction of the transmitted force N, then Nx = T / RX cos θ (R is the radius, θ is the cam inclination ), and the component force NX becomes smaller as shown in FIG. Therefore, the force that propels the mirror f becomes smaller, and there is a risk that the stepping motor a will overtorque and step out.

(Means for Solving the Problems) In order to solve the above problems, the present invention includes a through lens that moves on the optical axis to change the magnification, and a light beam from the through lens that is reflected toward the photosensitive drum. and a magnification changing device for a copying machine, which is equipped with a mirror that moves in conjunction with the lens for optical path length correction, comprising an eccentric cam that moves the mirror by being rotationally driven by a drive source that moves the lens; The eccentric cam is characterized by having the largest radius when the mirror is at the same magnification position.

(Function) According to the above configuration, at a position S where the inclination of the cam is large (for example, a position of x0.5), the radius R of the eccentric cam becomes small, and the transmission force F becomes large, so that The component force Fx can also be increased.

Conversely, at a position where the radius of the cam is large, that is, at a position M near equal magnification, the inclination of the cam becomes close to 0, and the component force Fx of the transmitted force in the optical axis direction can also be increased. That is, the same load as in the conventional example can be moved with a smaller drive torque than in the conventional example.

(Example) An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 shows an example of an electrophotographic copying machine equipped with a magnification changing device according to the present invention. A photosensitive drum 1 that can be rotated in a counterclockwise direction is disposed approximately in the center of the copying machine body, and around it are an eraser lamp 3 and a charger 4.
, a microtoning type developing device 5, a transfer charger 6, a copy paper separation charger 7, and a blade type cleaning device 8 are provided. The photosensitive drum 1 is charged by passing through the charger 4 and the eraser lamp 3, and receives image exposure from the optical system 9.

The optical system 9 is installed below the document table 80 to scan the document, and includes an illumination lamp 10 as a light source and a reflector 1.
6, sub-reflector 17, slit 18, movable mirror 11.1
2.13, a through lens 14, and a mirror 15. The light source 10 and the movable mirror 11 are connected to the photosensitive drum 1.
The movable mirror 12.13 moves to the left at a speed of (v/n; where n: copy magnification) with respect to the circumferential velocity (V) (constant regardless of whether the magnification is the same or variable magnification), and the movable mirror 12.13 moves at a speed of (v/n). 2n) to the left. When changing the copying magnification, the through lens 14 moves on the optical axis and the mirror 15 moves and swings, but this magnification changing device will be described in detail later.

On the other hand, copy sheets p held in a stack in a cassette 81 are transported by a paper feed roller 82 in synchronization with the image on the photosensitive drum 1 as appropriate, and after image transfer, pass through a transport path 83 and pass through a fixing roller 84. After passing, it is discharged onto the tray 86 by the discharge roller 85.
This will be explained with reference to the drawings and FIG. This magnification changing device allows stepless selection of magnification from enlargement to reduction, specifically from maximum enlargement (X2.0) to normal magnification (XL, O).
It is possible to appropriately select the magnification from 1 to the maximum reduction (Xo, 5).

The magnification changing device generally includes a lens moving mechanism 30, a mirror moving mechanism 40, a mirror swinging mechanism 70, a stepping motor (drive source) 20 that drives these, and a drive transmission mechanism.

A drive gear 21 is provided on the output shaft of the stepping motor 20.
is fixed, and a first intermediate gear 22 meshes with this drive gear 21. A drive pulley 31 and a second intermediate gear 23 are fixed to a shaft (pulley shaft) 29 of the first intermediate gear 22.
The intermediate gear 23 meshes with a third intermediate gear 24 fixed to a shaft (cam shaft) 28 of an eccentric cam 41 for continuously moving the mirror 15.

Therefore, the driving force of the stepping motor 20 is transmitted to the driving pulley 31 of the lens moving mechanism 30 via the driving gear 21 and the first intermediate gear 22, while the driving force of the stepping motor 20 is transmitted to the driving pulley 31 of the lens moving mechanism 30 via the driving gear 21 and the first
The signal is transmitted to the eccentric cam 41 of the mirror moving mechanism 40 via the intermediate gear 22, the second intermediate gear 23, and the third intermediate gear 24.

The lens moving mechanism 30 moves the through lens 14 to the light amount X.
It is movably mounted on a guide shaft 32 and a guide rail 33 (shown only in FIG. 2) installed in parallel with the drive boob, and the wire 34 wound around the drive boob IJ31 is stretched around a rotatable pulley 35,36. Moreover, the middle part of the wire 34 is fixed to the side part of the through lens 14.

The mirror moving mechanism 40 is configured as follows.

That is, the guide hole 43 is formed in the support plate 42 fixed to the main body.
is provided in a direction parallel to the optical axis X, while the mirror cover 44
A guide shaft 45 is provided on the side surface and the end surface of the mirror holder 49, respectively.
a, 45b are provided protrudingly, and these guide shafts 45a
, 45b are inserted into the guide hole 43 so that the mirror 15 is guided movably in the optical axis X direction. The pair of guide shafts 45a and 45b are connected at their ends by a connecting plate 46. Further, as shown in FIG. 2, a roller 47 is provided on the inner surface of the coupling plate 46.
An elastic holder 48 is attached to the tip of the elastic holder 48.
The roller 47 is moved to the support plate 4 by the elastic force of the elastic holder 48.
2, the side surface of the mirror cover 44 is brought into close contact with the support plate 42, and the end surface of the mirror holder 49 is brought into close contact with the inner surface of the side wall of the mirror cover 44, so that the mirror 14
The surface angle with respect to the optical axis X is set to be appropriate. still,
The mirror holder 49 has a guide shaft 50 at its other end and is guided and supported by a guide plate 51 attached to the main body.

The mirror 15 is moved in the optical axis X direction by rotation of the eccentric cam 41 by less than 360°. For this reason, a mirror cover 44 that is integral with the mirror 15 in the optical axis direction is provided.
An arm 52 is provided that protrudes toward the eccentric cam 41 from the cam follower 52, and a cam follower 54 disposed at the tip of the arm 52 is eccentrically moved by a tension spring 60 applied to a coupling plate 46 integrated with the mirror cover 44 in the direction of light flux propagation. It is brought into contact with the cam 41.

As a result, the mirror 15 is always biased in the direction in which the light beam travels, but this biasing force becomes weaker as the mirror moves farther back and toward the photosensitive drum l. Note that the eccentric cam 41 is located between the cam follower 54 and the mirror 15.

The cam curve of the eccentric cam 41 is formed as shown in FIG.
) The cam radius at S is made smaller. When compared with the conventional eccentric cam d shown by the imaginary line in this figure (see FIG. 6), the eccentric cam 41 of this embodiment has a cam radius at the L and S positions that corresponds to the conventional eccentric cam d. 1. It is clear that the cam radius at s is smaller than the cam radius at s.

Further, near the same magnification where the cam radius is necessarily at its maximum, the cam inclination is close to 0, and the mirror movement load is extremely small, and is sufficiently smaller than the driving torque at the L and S positions.

Next, the mirror swing mechanism 70 will be explained. The end face of the mirror holder 49 is formed as shown in FIG. As the guide shafts 45b and 50 move, they rotate about the guide shafts 45b and 50. and the inclined guide hole 7
By appropriately determining the shape of mirror 2, the light beam reflected by mirror 15 can be configured to enter a fixed position on photosensitive drum 1, no matter what magnification position the mirror 15 is at.

The operation of the magnification changing device having the above configuration will be explained below.

When desired magnification data is input from an operation panel or the like, a predetermined number of pulses are input to the stepping motor 20 based on this data, causing the stepping motor 20 to rotate a predetermined amount. The predetermined number of pulses is determined by the through lens 1.
The same magnification position of 4 is photoelectrically detected, and the number is used to rotate the stepping motor 20 in forward and reverse directions from this same magnification position to move the through lens 14 to the position of the desired magnification.

The rotation of the stepping motor 20 is controlled by the drive gear 21, the first
It is transmitted to the through lens 14 via the intermediate gear 22, drive pulley 31, and wire 34, and moves the through lens 14. In FIG. 3, Ll indicates the lens position at the maximum magnification, Ml the same magnification position, and Sl the lens position at the minimum magnification.

Further, the rotation transmitted to the first intermediate gear 22 is transferred to the second intermediate gear 2.
3. It is transmitted to the eccentric cam 41 via the third intermediate gear 24, and further via the cam follower 54, arm 52, and mirror cover 44, moves the mirror holder 49 and its attached parts in the optical axis direction to achieve the desired magnification. Mirror 1 in the suitable position
Position 5. In FIG. 3, L2 indicates the mirror position at the maximum magnification, M2 the same magnification position, and S2 the mirror position at the minimum magnification.

Furthermore, the mirror holder 49 rotates while being guided by an inclined guide hole 72 formed in the support plate 42 by its own movement.
Since mirror 15 is centered at a predetermined rotational position, mirror 1
The position at which the light beam reflected by 5 enters the photosensitive drum 1 can be kept constant regardless of the magnification.

Furthermore, in this embodiment, the cam follower 54 of the swinging arm 52 is brought into pressure contact with the eccentric cam 41 by a spring (tension spring) 60 that biases the mirror 15 in the light flux traveling direction. The eccentric cam 41 whose cam radius can be made small at the magnification position can be used, and the biasing force of the spring 60 can be minimized at these positions S and L, so that the eccentric cam 41 can be rotationally driven. The load on the drive source 21 can be reduced.

(Effects of the Invention) Since the present invention has the above-mentioned configuration and operation, it has the advantage that the mirror can be moved smoothly and overtorque of the drive source can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of an embodiment of the present invention, FIG. 2 is a plan view of the main parts, FIG. 3 is a sectional view schematically showing the entire copying machine to which the invention is applied, and FIG. The figure is a plan view showing the cam curve of the eccentric cam, FIG. 5 is an exploded perspective view showing the mirror swing mechanism, FIG. 6 is a schematic plan view showing the transmission force between the eccentric cam and the mirror in the conventional example, FIG. 7 is a perspective view showing a conventional example.

Claims (2)

[Claims] (1) A through lens that moves on the optical axis to change the magnification, and a mirror that reflects the light beam from the through lens toward the photosensitive drum and moves in conjunction with the lens to correct the optical path length. A magnification changing device for a copying machine, comprising an eccentric cam that is rotationally driven by a drive source that moves the lens to move the mirror, and the eccentric cam has the largest radius when the mirror is placed at the same magnification position. A magnification changing device for a copying machine, characterized by: (2) The cam follower, which moves together with the mirror, is brought into pressure contact with the eccentric cam by an elastic member that biases the mirror in the light flux traveling direction, and the elastic member is configured such that the elastic force of the elastic member is the smallest at maximum expansion or minimum contraction. A magnification changing device for a copying machine according to claim 1, wherein the magnification changing device is arranged such that: