JP4443328B2 - piston - Google Patents

Description

  The present invention relates to a piston used in a hydraulic cylinder or a hydraulic shock absorber.

  In general, a hydraulic cylinder and a hydraulic shock absorber have a piston rod inserted into the cylinder through a piston, and the piston includes a piston body and a synthetic resin ring fitted to the outer periphery of the piston body. The inner periphery of the cylinder is slidably contacted via a ring.

  And as a piston used for this kind of hydraulic cylinder and hydraulic shock absorber, what was indicated by JP, 2002-295777, A (patent documents 1 reference) is developed, for example.

  As shown in FIG. 10, the piston P includes a piston main body 1 coupled to the piston rod 3 and a synthetic resin ring 2 fitted to the outer periphery of the piston main body 1. Are provided with a plurality of annular grooves 1a, 1b, 1c, 1d, 1e, and 1f. The ring 2 is formed on the ring body 2a along the outer periphery of the piston body 1 and on the inner periphery side of the ring body 2a. A plurality of inner peripheral annular projections 2c and 2d fitted in the annular grooves 1a to 1e, and an end lip 2b formed at the end of the ring body 1 and curled outwardly, the piston P is placed in the cylinder. When inserted, the end lip 2b comes into contact with the inner circumference of the cylinder.

  As a method for forming the above-described piston P, the one disclosed in JP 2002-295679 A (see Patent Document 2) has been developed.

That is, as shown in FIGS. 11 (a) and 11 (b), the piston P is formed by a piston body 1 having a plurality of annular grooves 1d, 1c and the like on the outer periphery along the axial direction, In a piston composed of a ring body 2a fitted to the outer periphery and a ring 2 comprising an inner peripheral annular projection 2c fitted to each annular groove 1d, 1c, etc., a disc-shaped synthetic resin ring The inner peripheral end of the base material A is fitted into the end surface side annular groove of the piston body 1, and then the ring base material A is fixed to the piston body 1 by the die 9 while the piston body 1 is fixed by the fixing jigs 7 and 8. Further, the ring base material A is heated and softened during the pressing process, and the ring body 2a along the outer periphery of the piston body 1 and the inner ring-side annular protrusions flowed into the annular grooves 2c. Are formed.
Japanese Patent Laying-Open No. 2002-295777 (FIG. 1) JP 2002-295679 A (drawing)

  The conventional piston P is not particularly defective in function, but it is desired to improve the following problems.

  That is, as shown in FIG. 12, when the end lip 2b of the ring 2 is pressurized with the die 9 and pressed against the piston main body 1 side, tensile residual stresses X1 and X2 are generated on the outer peripheral side as indicated by the arrows. Compressive residual stresses Y1 and Y2 are generated on the circumferential side.

  As a result, as shown in FIG. 13, the end lip 2b exerts a force on the ring 2 by the residual stresses X1, X2 and Y1, Y2 immediately after the die 9 is removed with respect to the pressing position Z1 of the die 9. In a state where there is no action, it warps to the position Z2, and if it is left for a long time, it warps greatly to the position Z3.

  Therefore, as shown in FIG. 2, when the piston P is inserted into the cylinder (not shown), the inner diameter of the cylinder is substantially equal to the outer shape of the ring 2, so that the end lip 2b is warped to the position Z3. Then, the tightening allowance S1 becomes large. Therefore, the upper end portion of the end lip 2b is pressed against the inner peripheral surface of the cylinder, and the surface pressure between the end lip 2b and the cylinder is increased to increase the friction.

  This increases the sliding resistance when the piston rod of the hydraulic cylinder or the hydraulic shock absorber is extended and the smooth movement cannot be achieved, so that the long-term stability of the ride comfort and the maneuverability of the vehicle is lowered.

  Accordingly, an object of the present invention is to reduce the residual stress generated during pressure molding at the end lip of the ring body, thereby reducing the change in the tightening allowance after being left in the cylinder for a long period of time, and extending the smooth expansion and contraction operation. It is to provide a piston that can be achieved stably over a period of time.

In order to achieve the above object, a piston according to the present invention comprises a piston body and a ring fitted to the outer periphery of the piston body, and the piston body includes a plurality of annular grooves along the axial direction on the outer periphery. ring and ring body along the the outer periphery of the disc-shaped synthetic resin base material of the piston body piston body formed pressure by heating soften while and push the outer periphery of inner fitted to flow into the inside each of the annular grooves In a piston composed of a circumferential annular protrusion, after the ring body is pressure molded , the end lip outer periphery corner of the ring body is cut off to reduce the residual stress of the end lip generated during pressurization. It is characterized by having made it.

Since the outer peripheral corner of the end lip of the ring body is cut after the ring body is pressure-molded, the residual stress of the end lip generated during the pressure molding is reduced by the amount of cutting, and the end lip gradually There is little action to warp.

  For this reason, when inserted into the cylinder and used, there is little increase in friction between the end lip and the cylinder.

  In addition, even if the end lip is warped, the tightening allowance itself can be reduced, and the change in the allowance for the cylinder of the end lip after being left for a long period of time is correspondingly reduced. The period becomes stable and small, and the expansion and contraction operation of the piston becomes smooth. Therefore, it is possible to improve the riding comfort of the vehicle and stabilize the operability.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 8. The piston according to the present invention is used for a hydraulic cylinder or a hydraulic shock absorber, and its basic structure is shown in FIG. It is the same as the prior art.

That is, as shown in FIG. 1, the piston P according to the present invention comprises a piston body 1 and a ring 2 fitted to the outer periphery of the piston body 1 as in the prior art. a plurality of annular grooves 1a extending along, 1b, 1c, 1d, 1e , comprises a 1f, heated and softened while narrowing the ring 2 is press the same disk-shaped synthetic resin matrix a with the conventional Figure 11 on the outer circumference of the piston body 1 a ring body 2a along the outer periphery of the piston body 1 formed pressure by, those which are composed of a plurality of inner circumferential side annular projection 2c fitted to flow into the respective annular grooves 1a~1f .

  In the present invention, particularly, as shown in FIG. 2, since the end lip 2b is warped to the position Z4 by residual stress immediately after removing the die 9, the outer peripheral side of the end lip 2b in this position. The residual stress of the end lip 2b generated at the time of pressure molding is reduced by cutting the corner.

  In this case, there are various patterns for cutting the corner of the end lip 2b. As a typical cutting form, for example, as shown in FIG. 2, a circular truncated cone-shaped inclined surface 10 whose diameter is reduced toward the left end surface of the end lip 2 b is formed.

  That is, as shown in FIG. 2, the ring 2 is pressed against the piston body 1 with a die 9 and molded, and then the outer peripheral side corner of the end lip 2b is cut along the line 11 with a cutter or the like to form the inclined surface 10. ing.

  In this case, the diameter of the left end surface, which is the outermost end of the end lip 2b, is smaller than the diameter of the ring body 2a, thereby reducing the amount of residual stress generated during pressure forming of the end lip 2b.

  Moreover, the clamping allowance S2 for the cylinder is smaller than the conventional clamping allowance S1, and the sliding resistance of the piston 2 to the cylinder is reduced.

  As described above, in the present invention, since the outer peripheral side corner of the end lip 2b is cut and the inclined surface 10 is formed, the residual stress of the end lip 2b is reduced by the cut, and is also left for a long time. Even if the rear end lip 2b is warped to the maximum, the imaginary position of the left end surface, which is the outermost end, has a smaller diameter as compared with the position Z3 when the outer peripheral corner of the end lip 2b is not cut.

  Therefore, according to the present invention, the tightening margin of the end lip 2b with respect to the inner peripheral surface of the cylinder can be reduced, and at the same time, the tightening margin can be stabilized for a long period of time, and the piston can be smoothly expanded and contracted in the cylinder. Operation can be realized over a long period of time.

  Further, when the inclined surface 10 is formed as described above, when the end lip 2b is inserted into the cylinder, it is the cutting start point B that contacts the inner peripheral surface of the cylinder, and the angle θ of the cutting start point B is an obtuse angle. Therefore, even when sliding in the cylinder, the surface pressure against the inner circumferential surface of the cylinder does not increase, the oil film on the inner circumferential surface of the cylinder is not cut, and the occurrence of stick slip can be prevented.

  The molding process of the piston P of the present invention is the same as FIG. As shown in FIG. 9, a rough surface 1A having a corrugated shape or a sawtooth shape is formed on the inner peripheral surfaces, for example, side surfaces of the annular grooves 1b to 1e to prevent the ring 2 from coming off in the direction of arrow B. preferable.

  FIG. 3 shows another embodiment of the present invention, which is a smooth surface obtained by post-processing or simultaneous processing of the portion where the outer peripheral surface of the ring body 2a and the inclined surface 10 on the end lip 2b side are connected, for example, The convex curved surface 12 has a smaller sliding resistance with respect to the cylinder. Other configurations and operational effects are the same as those in FIG.

  4 to 8 show other embodiments of the present invention, and these show various shape patterns when the outer peripheral corner of the end lip 2b is cut off.

  FIG. 4 is the same in that the outer peripheral side corner of the end lip 2b is cut out to form the inclined surface 10A, but this is the one where the cutting position is closer to the outside of the corner.

  FIG. 5 shows a curved surface 10B formed by cutting.

  FIG. 6 shows a curved surface 10C having a larger curvature than the curved surface 10B of FIG. 5 in forming a curved surface as in the case of FIG.

  In FIG. 7, the outer peripheral side corner of the end lip 2b is cut out in the same manner as in FIG. 2 to form the inclined surface 10D. In this case, the cutting start point is further from the cutting start point B of FIG. The portion close to the outer surface is cut off in all the portions where the ring 2 is deformed and warped in the radial direction due to residual residual stress.

  For this reason, the tightening margin becomes zero or close to zero, and a piston having a smaller sliding resistance than that of the other embodiments can be realized even after being left for a long time.

  FIG. 8 shows a rectangular surface 10E having a cut section obtained by cutting the outer peripheral corner of the end lip 2b at a right angle or a right angle.

  The operational effects of the above embodiments are the same as those of the embodiment of FIGS. 1 and 2, and the cutting form is not limited to that shown in the figure, for example, the end lip 2b is warped. The portion may be cut horizontally along the ring main body 2a. In short, any portion that cuts the outer corner of the end lip 2b to reduce the residual stress can be used.

It is a partially cutaway longitudinal side view of the piston according to the present invention. It is an expanded sectional view of the edge part lip part of FIG. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the edge part lip part of the piston concerning other embodiments. It is an expanded sectional view of the annular groove of FIG. It is a partial notch longitudinal side view of the conventional piston. (A), (b) is sectional drawing of the piston main body, ring base material, and die | dye which show the process of shape | molding the conventional piston. It is an expanded sectional view which shows the residual stress at the time of the conventional piston shaping | molding. It is an expanded sectional view of the edge part lip part of the conventional piston.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piston main body 1a, 1b, 1c, 1d, 1e, 1f Annular groove 2 Ring 2a Ring main body 2b End lip P Piston 10 Inclined surface

Claims (4)

It consists of a piston body and a ring fitted to the outer periphery of the piston body. The piston body has a plurality of annular grooves along the axial direction on the outer periphery, and the ring has a disc-shaped synthetic resin base material on the outer periphery of the piston body. a ring body along the outer periphery of the piston body by heating soften and formed under pressure while and push in the piston is configured with an inner circumferential side annular projection fitted to flow into the in each annular groove, the ring A piston characterized in that after the main body is pressure-molded, the end lip outer peripheral side corner of the ring main body is cut to reduce the residual stress of the end lip generated during pressurization.   2. The piston according to claim 1, wherein when the end lip outer peripheral side corner is cut off, the diameter of the end of the end lip is made smaller than the diameter of the ring body.   The piston according to claim 1, wherein the end lip outer peripheral corner is cut to form an annular inclined surface whose diameter is reduced toward the end surface of the end lip.   4. The piston according to claim 3, wherein a continuous portion between the outer peripheral surface of the ring main body and the inclined surface of the end lip is formed into a smooth surface.

Images