JP2014211195A - Method for molding chain-positioning member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding a chain-positioning member that can readily mold a resin chain-positioning member having a smooth sliding surface without any warpage.SOLUTION: The method for molding a chain-positioning member for injection molding the resin chain-positioning member having the chain sliding surface at one side surface in the longitudinal direction thereof includes a step of injecting a resin toward a direction along a side wall surface 21a corresponding to the sliding surface in a cavity 21 of a molding die 2 to mold the whole body of the chain-positioning member.

Description

  The present invention relates to a method for forming a chain positioning member, and more particularly, to a method for forming a chain positioning member that can easily mold a resin-made chain positioning member that is prevented from warping and has a smooth sliding surface.

  As shown in FIG. 4, the cam chain driving device in the four-cycle engine includes a crank sprocket 101 fixed to the crankshaft, cam sprockets 102 and 103 fixed to the camshaft, and the sprockets 101 and 102. 103, and the cam chain 200 is run in the direction indicated by the arrow in the figure by rotating the crankshaft, and the camshaft is rotated to interlock the cam operation. ing.

  In the cam chain 200, the cam chain guide 10 is disposed on the tension side, and the cam chain tensioner 20 is disposed on the slack side. Each of the cam chain guide 10 and the cam chain tensioner 20 has an elongated shape along the traveling direction of the cam chain 200, and abuts the cam chain 200 on one side surface in the longitudinal direction. It has sliding surfaces 10a and 20a that move.

  The cam chain guide 10 and the cam chain tensioner 20 are positioned so that the sliding surfaces 10a and 20a are brought into contact with the cam chain 200 to guide the travel of the cam chain 200, or a predetermined tension is applied to the cam chain 200. It is a chain positioning member that positions so as to be applied.

  Conventionally, in such a chain positioning member, the sliding surface with the chain is formed as a separate member from the main body portion (Patent Document 1). In this case, the main body portion is made of resin, the sliding surface is formed of a metal having excellent wear resistance, and the chain positioning member is configured by assembling them together.

JP 2009-293690 A

  In recent years, a request for weight reduction of an engine has led to a demand for weight reduction of a chain positioning member, and it has been studied to injection-mold the entire chain positioning member using a resin.

  However, if the entire chain positioning member is injection-molded using resin, the molded product tends to warp in the lateral direction (width direction orthogonal to the longitudinal direction), and the streaky flow mark is formed on the sliding surface. There has been a problem that the rate of occurrence of defective products is increased due to easy outbreak.

  When the lateral warping of the chain positioning member increases, the sliding surface will not be linear, and the function of positioning the chain will be impaired, causing the chain to meander or, in the worst case, disengage from the sprocket. There is a risk of falling. Further, if there is a flow mark on the sliding surface, there is a possibility that the sliding of the chain cannot be smoothly guided.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming a chain positioning member that can easily form a resin chain positioning member that has a smooth sliding surface and is prevented from warping.

  Still another subject of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

  1. A method for molding a chain positioning member, which comprises injection molding a resin chain positioning member having a sliding surface of a chain on one side surface in a longitudinal direction, wherein a side wall surface corresponding to the sliding surface in a cavity in a molding die A method for forming a chain positioning member, wherein the entire chain positioning member is molded by injecting resin in a direction along the direction.

  2. 2. The molding of the chain positioning member according to claim 1, wherein the resin is injected so that the flow direction of the resin at the time of injection into the cavity is maintained as it is to the position of the side wall surface without substantially changing the direction. Method.

  3. A gate is disposed at any end in the longitudinal direction of the cavity, and resin is injected from the gate toward a direction along a side wall surface in the cavity corresponding to the sliding surface. 3. A method for forming a chain positioning member according to 1 or 2.

  4). 4. The method of forming a chain positioning member according to any one of 1 to 3, wherein the chain positioning member is a cam chain guide that positions the travel of the cam chain for the engine on the sliding surface.

  According to the method for forming a chain positioning member according to the present invention, the occurrence of warpage is suppressed, and a resin chain positioning member having a smooth sliding surface can be easily formed.

Side view showing an example of chain positioning member Sectional drawing which follows the (ii)-(ii) line | wire in FIG. Sectional drawing which shows the shaping die explaining the shaping | molding method of the chain positioning member which concerns on this invention Schematic showing an example of a cam chain drive device provided with a chain positioning member Sectional drawing which shows the shaping die explaining the shaping | molding method of the conventional chain positioning member Diagram explaining how to measure warpage

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1 is a side view showing an example of a chain positioning member, and FIG. 2 is a cross-sectional view taken along line (ii)-(ii) in FIG. Here, a cam chain guide that guides the travel of the cam chain will be described as an example of the chain positioning member in the same manner as the cam chain guide 10 shown in FIG.

  The entire cam chain guide 1 is injection-molded with resin, and a sliding surface 1a on which the cam chain slides on one side surface in the longitudinal direction (left-right direction in FIG. 1) to position the cam chain travel. have. The sliding surface 1a extends linearly along the longitudinal direction, and is provided with standing wall portions 1b and 1b on both side edges thereof, thereby forming a U-shaped cross section.

  When such a cam chain guide 1 is injection-molded, conventionally, a molding die 300 shown in FIG. 5 has been used. In this molding die 300, a gate 302 for injecting resin into a cavity 301 for molding the cam chain guide 1 corresponds to the sliding surface 1a of the cam chain guide 1 in the vicinity of one end in the longitudinal direction of the cavity 301. The resin is disposed on the side opposite to the side wall surface 301a and is configured such that resin is injected from the gate 302 toward the side wall surface 301a as indicated by an arrow in the figure.

  When resin is injected from the gate 302 into the cavity 301 using the molding die 300, the resin first strikes the side wall surface 301a corresponding to the sliding surface 1a, and the course is changed in the lateral direction while the flow of the resin is disturbed. It will be filled in the longitudinal direction. As a result of confirmation by the present inventor, air is entrained due to the disturbance of the resin at this time, and appearance defects occur in the molded product, so that a streaky flow mark is likely to appear on the sliding surface 1a of the molded product. all right.

  In addition, the occurrence of such resin turbulence breaks the balance when the resin shrinks, and the shrinkage rate between the resin flow direction (longitudinal direction) and the shrinkage rate perpendicular to the flow direction. It has also been found that the difference in the above becomes large, and due to this, the molded product is likely to warp.

  For this reason, in the present invention, the cam chain guide 1 is injection-molded using the molding die 2 illustrated in FIG. 3 devised so that the resin can be prevented from flowing in the cavity while being disturbed. I am doing so.

  In this molding die 2, a gate 22 for injecting resin into a cavity 21 for molding the cam chain guide 1 is disposed at one end portion (left end portion in FIG. 3) in the longitudinal direction of the cavity 21. The end portion where the gate 22 is disposed is a portion corresponding to one end portion in the longitudinal direction of the cam chain guide 1. Then, as indicated by an arrow in the drawing, resin is injected from the gate 22 along the side wall surface 21a corresponding to the sliding surface 1a of the cam chain guide 1 toward the right in the drawing. The whole is configured to be injection-molded at a time.

  When resin is injected from the gate 22 into the cavity 21 using the molding die 2, the longitudinal direction flows in the right direction in the figure along the side wall surface 32 corresponding to the sliding surface 1 a, and the inside of the cavity 21. The whole is filled. For this reason, the injected resin does not collide with the side wall surface 22 as in the conventional case and is not disturbed.

  As a result, the cam chain guide 1 that is a molded product does not have a poor appearance due to the disturbance at the time of resin injection on the sliding surface 1a, and a streak-like flow mark as in the conventional case may occur. The smooth sliding surface 1a is formed. Further, since the disturbance during the resin injection is eliminated, the balance is not lost when the resin contracts, and the occurrence of warping as in the conventional case is suppressed, and the sliding surface 1a having excellent linearity is formed. become. Accordingly, it is possible to easily mold the resin cam chain guide 1 in which the occurrence of warpage is suppressed and the sliding surface 1a with the cam chain is smooth.

  The resin used in the present invention is not particularly limited. For example, polyamide resin such as nylon 66 (PA66) or nylon 46 (PA46) can be used (however, nylon is a registered trademark of DuPont).

  In the present invention, the position of the gate 22 is not particularly limited as long as the resin can be injected in the direction along the side wall surface 21 a corresponding to the sliding surface 1 a in the cavity 21. Preferred examples can be given. Although FIG. 3 shows an example in which the cavity 21 is arranged at the left end in the longitudinal direction, it is also preferable that the cavity 21 is arranged at the right end in FIG. In the present invention, the injection is performed so that the flow direction of the resin at the time of injection into the cavity 21 (the flow direction in the gate 22) is maintained as it is to the position of the side wall surface 21a without substantially changing the direction. Is preferred.

  In the above description, the cam chain guide 1 is exemplified as the chain positioning member. However, in the same way as the cam chain tensioner 20 shown in FIG. 4, the cam chain tensioner is used for positioning so as to apply a predetermined tension to the cam chain. The molding method and molding die according to the present invention can be similarly applied to the case where the entire cam chain tensioner is injection-molded with resin.

  In addition, the molding method and the molding die according to the present invention are not limited to molding a chain positioning member for positioning the cam chain for an engine, but are formed entirely of resin and are formed on one side surface in the longitudinal direction. The present invention can be widely applied to the case of forming a chain positioning member for positioning the running of the chain.

Example 1
By using a cam chain guide molding die in which a gate is arranged at the position shown in FIG. 3 and injecting resin (PA66) from the gate, the length in the longitudinal direction is 279.5 mm and the width of the sliding surface is 13 mm. Ten cam chain guides were injection molded.

  Each cam chain guide obtained was placed on a flat measurement surface as shown in FIG. 6 with one side of the both side surfaces arranged so as to sandwich the sliding surface, and the measurement surface by warpage. By measuring the height H of the tip lifted from the measurement surface from the measurement surface, the degree of occurrence of lateral warpage was measured.

  As a result, the warpage (H) was all within the range of 0.03 mm to 0.10 mm, and the sliding surface had good linearity.

  Further, when the sliding surface was visually observed, there was no noticeable appearance defect and no generation of streak-like flow marks was observed.

(Comparative example)
Except for using a cam chain guide molding die in which a gate is arranged at the position shown in FIG. 5, ten cam chain guides similar to those in the first embodiment are injection-molded, and the lateral direction is the same as in the first embodiment. The degree of warpage was measured.

  As a result, the warp (H) was 3.1 mm to 5.9 mm, and a large warp was generated as compared with Example 1.

  Further, when the sliding surface was visually observed, generation of streak-like flow marks was confirmed in all cam chain guides.

1: Cam chain guide (chain positioning member)
DESCRIPTION OF SYMBOLS 1a: Sliding surface 1b: Standing wall part 2: Molding die 21: Cavity 21a: Side wall surface 22: Gate

Claims (4)

A method for molding a chain positioning member, which comprises injection molding a resin chain positioning member having a sliding surface of the chain on one side surface in the longitudinal direction,
A method of forming a chain positioning member, comprising: molding a whole of the chain positioning member by injecting resin toward a direction along a side wall surface corresponding to the sliding surface in a cavity in a molding die.   2. The chain positioning member according to claim 1, wherein the flow direction of the resin at the time of injection into the cavity is injected so as to be maintained up to the position of the side wall surface without substantially changing the direction. Molding method.   A gate is arranged at any end in the longitudinal direction of the cavity, and resin is injected from the gate toward a direction along a side wall surface in the cavity corresponding to the sliding surface. Item 3. A method for forming a chain positioning member according to Item 1 or 2.   The said chain positioning member is a cam chain guide which positions the driving | running | working of the cam chain for engines on the said sliding surface, The shaping | molding method of the chain positioning member in any one of Claims 1-3 characterized by the above-mentioned.

Images