JP5174473B2 - Spring contact structure of image forming apparatus - Google Patents

Description

  The present invention relates to a spring contact structure of an image forming apparatus such as a printer or a copying machine.

  In an image forming apparatus such as a copying machine or a printer that forms an image on a sheet by electrophotography, a spring contact is used as an electrical connection means. An example is shown in FIG.

That is, FIG. 10 is a partial perspective view showing a conventional example of a spring contact structure of an image forming apparatus. The illustrated spring contact 101 is formed by integrating a metal compression spring 102 and a coil spring 103, and the compression spring 102. Is passed through a circular hole 111 a formed in the wall 111 of the main body frame 110, and the coil spring 103 is fixed to the main body frame 110 by being fitted into a boss 113 protruding from the main body frame 110.
JP 2004-167626 A JP-A-11-167335

However, in the conventional spring contact structure shown in FIG. 10, when a force acts on the coil spring 103 of the spring contact 101 in the inner direction (the arrow direction in FIG. 10), the coil spring 193 comes out of the boss 113 (the arrow in FIG. 10). Force), the coil spring 103 comes out of the boss 113. As a countermeasure, a method of fitting the retaining ring to the outer cylinder of the boss 113 is employed, but this method increases the number of parts and the number of assembling steps and increases the cost.

  The present invention has been made in view of the above problems, and the object of the present invention is to securely fix the contact spring without using a retaining ring, thereby reducing the number of parts and the number of assembling steps and reducing the cost. Another object is to provide a contact spring structure for an image forming apparatus.

In order to achieve the above object, according to the first aspect of the present invention, the compression spring of a spring contact comprising an integrated compression spring and a coil spring is passed through a hole formed in the main body frame, and the coil spring is projected from the main body frame. In the spring contact structure of the image forming apparatus formed by fitting to the boss formed,
The compression spring of the spring contact is formed integrally with a small diameter portion and a large large diameter portion whose outer diameter is smaller than the inner diameter of the hole of the main body frame, and the natural length of the large diameter portion is defined between the hole and the wall of the main body frame. The spring constant of the large diameter portion is set to be larger than the spring constant of the small diameter portion, and the small diameter portion of the compression spring is passed through the hole of the main body frame, and the large diameter portion of the main body frame is made longer . and compressively on said mounting portion,
When the contact point of the conveyance unit provided in the image forming apparatus so as to be openable / closable comes into contact with the free end that is the contact point of the coil spring, the large diameter portion of the compression spring is applied by a compressive load larger than the load acting on the free end. Is configured to be held by the mounting portion of the main body frame .

The invention according to claim 2 is characterized in that, in the invention according to claim 1 , the pitch of the large diameter portion of the compression spring is made smaller than the pitch of the small diameter portion.

According to the first aspect of the present invention, the compression spring of the spring contact formed by integrating the compression spring and the coil spring is a two-stage spring having a small diameter portion and a large diameter portion, and the natural length of the large diameter portion is set to the main body frame. The spring constant of the large diameter part is set larger than the spring constant of the small diameter part, and the large diameter part is shrunk to the attachment part of the main body frame. When the contact point of the transport unit of the forming apparatus comes into contact with the free end that is the contact point of the coil spring, the large diameter portion of the compression spring is held on the attachment portion of the main body frame by a compressive load larger than the load acting on the free end. because you so that arrangement, the coil spring is deformed inwardly contact the transport unit to the free end of the coil spring abuts, also the coil spring acts the direction of the force passing from the boss, that the coil spring exit from the boss Absent Therefore, the contact spring can be fixed to the main body frame without using a retaining ring, and the number of parts and assembly steps can be reduced and the cost can be reduced. Since the small diameter portion of the compression spring constituting the two-stage spring is in a free state through a hole formed in the main body frame, it functions as a contact as in the conventional case.

According to the second aspect of the present invention, the spring constant of the large diameter portion can be set larger than the spring constant of the small diameter portion by making the pitch of the large diameter portion of the compression spring smaller than the pitch of the small diameter portion. .

  1 is a partial perspective view of a main body frame of the image forming apparatus, FIG. 2 is an enlarged detail view of a portion A (spring contact mounting portion) in FIG. 1, FIG. 3 is a perspective view of a conveyance unit of the image forming apparatus, and FIG. 5 is a front view of the spring contact (in the direction of arrow B in FIG. 4), FIGS. 6 to 8 are perspective views of a spring contact mounting portion of the main body frame, and FIG. 9 is a spring contact of the main body frame. It is sectional drawing of an attaching part.

The image forming apparatus according to the present embodiment is a color laser printer. As shown in FIG. 1, a spring contact 1 shown in FIGS. 4 and 5 is provided on one end face (right end face) in the width direction of the main body frame 10. A mounting portion for mounting is formed. As shown in detail in FIG. 2, the attachment portion includes two walls 11, 12 that are erected vertically on the side surface of the main body frame 10, a circular hole 11 a formed in one wall 11 , and the main body frame 10. It is comprised by the cylindrical boss | hub 13 standingly integrated by the side surface.

  Further, a conveyance unit 20 shown in FIG. 3 is provided at the front portion of the image forming apparatus so as to be openable and closable. Secondary transfer rollers 21 and registration rollers are provided above and below the inner surface side (rear surface side) of the conveyance unit 20. Each 22 is rotatably supported. A contact 23 that abuts against the spring contact 1 shown in FIGS. 4 and 5 and is electrically connected is projected from the upper right side of the transport unit 20.

  Incidentally, as shown in FIGS. 4 and 5, the spring contact 1 is formed by integrating a compression spring 2 and a coil spring 3 wound in directions orthogonal to each other. 2 is a small-diameter portion 2A having a length L1 (d1 <D) smaller than the inner diameter D (see FIGS. 2 and 9) of the circular hole 11a formed in the wall 11 of the main body frame 10. (Minimum diameter) d2 is configured as a two-stage spring integrally formed with a large diameter portion 2B having a length L2 (<L1) of (d2> D) larger than the inner diameter D of the circular hole. The large diameter portion 2B constitutes a conical spring.

  Further, as shown in FIG. 5, the free end 3a of the coil spring 3 of the spring contact 1 is bent into a U shape, and the contact 23 of the transport unit 20 shown in FIG. In FIG. 4 and FIG. 5, the free end 3a is in the position shown by the solid line in FIGS. 4 and 5, and when the contact 23 of the transport unit 20 comes into contact with this, the coil spring 3 is torsionally deformed. Move to the position shown.

  Here, the large-diameter portion 2B of the compression spring 2 is shrunk to the attachment portion 14 between the wall 11 (circular hole 11a) and the wall 12 of the main body frame 10 shown in FIG. The length (length at no load) L2 is set to be longer than the length L of the mounting portion 14 of the main body frame 10 (L2> L).

  The spring constant of the large diameter portion 2B of the compression spring 2 is set larger than the spring constant of the small diameter portion 2A. Specifically, the pitch P2 of the large diameter portion 2B of the compression spring 2 is set smaller than the pitch P1 of the small diameter portion 2A (P2 <P1).

  As shown in FIGS. 6 to 9, the spring contact 1 configured as described above passes the small-diameter portion 2A of the compression spring 2 through the circular hole 11a formed in the wall 11 of the main body frame 10, and the large-diameter portion 2B. Is attached to the main body frame 10 by fitting the coil spring 3 into the boss 13 of the main body frame 10 after being mounted on the mounting portion 14 between the wall 11 (circular hole 11a) and the wall 12 of the main body frame 10.

  Thus, when the transport unit 20 shown in FIG. 3 rotates around the pivot point at the lower end and is closed, the contact 23 projecting from the transport unit 20 becomes a spring contact as shown in FIG. The coil spring 3 is torsionally deformed by coming into contact with the free end 3a of the one coil spring 3. As a result, the free end 3a of the coil spring 3 moves from the solid line position shown in FIGS. 4 and 5 to the chain line position, and a force F in the inner direction (the arrow direction in FIG. 4) acts on the coil spring 3. For this reason, a force in the direction of pulling the coil spring 3 from the boss 13 (in the direction of the arrow in FIG. 6) acts.

  However, in the present embodiment, the compression spring 2 of the spring contact 1 formed by integrating the compression spring 2 and the coil spring 3 is a two-stage spring having a small diameter portion 2A and a large diameter portion 2B. Since the large-diameter portion 2B is contracted to the attachment portion 14 between the wall 11 (circular hole 11a) and the wall 12 of the main body frame 10, the main body frame 10 of the spring contact 1 is applied by the compressive load acting on the large-diameter portion 2B. Can be fixed, and one fulcrum of the coil spring 3 is fixed to the main body frame 10. Therefore, the contact 23 of the transport unit 20 comes into contact with the free end 3a of the coil spring 3 as shown in FIG. 6 and the coil spring 3 is deformed inward, and a force in the direction of coming out of the boss 13 acts on the coil spring 3. However, the coil spring 3 does not come off from the boss 13. Therefore, the contact spring 1 can be securely fixed to the main body frame 10 without using a retaining ring which has been necessary in the past, and the number of parts and assembly man-hours can be reduced and the cost can be reduced. The small-diameter portion 2A of the compression spring 2 constituting the two-stage spring is in a free state through a circular hole 11a formed in the wall 11 of the main body frame 10, and thus functions as a contact as in the conventional case. .

  In the present embodiment, the natural length L2 of the large-diameter portion 2B of the compression spring 2 is longer than the length L of the attachment portion 14 between the wall 11 (circular hole 11a) and the wall 12 of the main body frame 10 ( L2> L), the large-diameter portion 2B is fixed in a compressed state at the mounting portion 14, and one fulcrum of the coil spring 3 connected to the large-diameter portion 2B is reliably secured by the compressive load acting on the large-diameter portion 2B. The coil spring 3 is securely prevented from coming off from the main body frame 10.

  In this embodiment, since the pitch P2 of the large diameter portion 2B of the compression spring 2 is smaller than the pitch P1 of the small diameter portion 2A (P2 <P1), the spring constant of the large diameter portion 2B is the spring constant of the small diameter portion 2A. Bigger than. For this reason, a compression load larger than the compression load acting on the small diameter portion 2A of the compression spring 2 acts on the large diameter portion 2B, and the fixing of the large diameter portion 2B is affected by the compression load acting on the small diameter portion 2A. Minimized.

  Further, the embodiment in which the present invention is applied to the spring contact structure of a color laser printer has been described above. However, the present invention can be applied to a spring contact structure of another image forming apparatus such as a copying machine or a facsimile in addition to a printer. Of course, the same applies.

2 is a partial perspective view of a main body frame of the image forming apparatus. FIG. FIG. 2 is an enlarged detail view of a portion A (spring contact mounting portion) of FIG. 2 is a perspective view of a transport unit of the image forming apparatus. FIG. It is a side view of the spring contact which concerns on this invention. It is a front view (figure of the arrow B direction of FIG. 4) of the spring contact which concerns on this invention. It is a perspective view of the spring contact attachment part of a main body frame. It is a perspective view of the spring contact attachment part of a main body frame. It is a perspective view of the spring contact attachment part of a main body frame. It is sectional drawing of the spring contact attachment part of a main body frame. It is a perspective view of the spring contact attachment part of the main body frame which shows the conventional spring contact structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spring contact 2 Compression spring 2A Small diameter part of compression spring 2B Large diameter part of compression spring 3 Coil spring 3a Free end of coil spring 10 Main body frame 11, 12 Wall of main body frame 11a Circular hole (hole) of wall
13 Body frame boss 14 Body frame mounting portion 20 Conveying unit 21 Secondary transfer roller 22 Registration roller 23 Contact d1 Outer diameter of small diameter portion of compression spring d2 Outer diameter of large diameter portion of compression spring D Inner diameter of circular hole L Main body Length of frame mounting part L1 Length of small diameter part of compression spring (free length)
L2 Length of large diameter part of compression spring (free length)
P1 Pitch of small diameter part of compression spring P2 Pitch of large diameter part of compression spring

Claims (2)

A spring contact of an image forming apparatus formed by passing the compression spring of a spring contact comprising an integrated compression spring and a coil spring through a hole formed in the main body frame and fitting the coil spring into a boss protruding from the main body frame. In structure
The compression spring of the spring contact is formed integrally with a small diameter portion and a large large diameter portion whose outer diameter is smaller than the inner diameter of the hole of the main body frame, and the natural length of the large diameter portion is defined between the hole and the wall of the main body frame. The spring constant of the large diameter portion is set to be larger than the spring constant of the small diameter portion, and the small diameter portion of the compression spring is passed through the hole of the main body frame, and the large diameter portion of the main body frame is made longer . and compressively on said mounting portion,
When the contact point of the conveyance unit provided in the image forming apparatus so as to be openable / closable comes into contact with the free end that is the contact point of the coil spring, the large diameter portion of the compression spring is applied by a compressive load larger than the load acting on the free end. Is configured to be held by the mounting portion of the main body frame . 2. The spring contact structure for an image forming apparatus according to claim 1, wherein the pitch of the large diameter portion of the compression spring is smaller than the pitch of the small diameter portion.

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