JP5617617B2 - piston - Google Patents

Description

  The present invention relates to a piston used in, for example, a reciprocating internal combustion engine.

  2. Description of the Related Art Conventionally, an outer piston (piston moving portion) and an inner piston (piston base), which is a separate member from the outer piston and connected to a connecting rod, have a structure in which the outer piston can reciprocate with respect to the inner piston. Pistons have been proposed.

  The outer piston has an annular peripheral wall portion surrounding the inner piston, and a space capable of accommodating the inner piston is formed inside thereof. A disc spring is accommodated between the inner piston and the outer piston. When the pressure in the combustion chamber increases, the outer piston moves toward the inner piston due to the deflection of the disc spring, and therefore, there is one that prevents the combustion chamber from exceeding the intended pressure (see, for example, Patent Document 1). .

JP-A-6-17665

  In this type of piston, the inner piston is loosely fitted in the outer piston so that the outer piston can reciprocate with respect to the inner piston. That is, a small gap is provided between the inner peripheral surface of the peripheral wall portion of the outer piston and the inner piston.

  When a load is input from the connecting rod to the inner piston, the inner piston is inclined with respect to the outer piston by the gap. At this time, a part of the outer peripheral surface of the piston moving part comes into contact with a part of the inner peripheral surface of the peripheral wall part of the outer piston, and the load concentrates on these parts. When the outer piston reciprocates with respect to the inner piston in this state, the portions of the inner piston and the outer piston that are in contact with each other tend to wear out.

  An object of this invention is to provide the piston which can suppress generation | occurrence | production of the abrasion of the contact part of the piston moving part and piston base resulting from the inclination of the piston base with respect to a piston moving part.

The piston according to claim 1 has a piston base portion having a pin boss, a piston head, and a skirt portion. The piston base portion is accommodated by forming a space inside thereof, and a piston central axis is located with respect to the piston base portion. And a piston moving part capable of reciprocating in the extending direction. The piston moving portion includes a vertical wall having a side surface parallel to the piston central axis on an inner wall on the piston head side forming the space. The piston base extends in the piston radial direction, and a first end faces the inner wall on the skirt portion side forming the space, and is slidable with the inner wall on the skirt portion side with the reciprocation. A moving portion and a second sliding portion that faces the side surface of the vertical wall and is slidable with the side surface as the reciprocating motion is provided. The first sliding portion has a gap between the first sliding portion and the inner wall on the skirt portion side, and between the second sliding portion and the side surface of the vertical wall. the piston base in the said gap between the inner wall of the skirt portion side, said second sliding portion and the longitudinal said than the gap between the side wall piston central axis in a plane perpendicular to the direction of extension The length along the straight line toward the center of is long .

  According to a second aspect of the present invention, in the first aspect, the first sliding portion and the second sliding portion are arranged so as to be shifted in a direction in which the piston central axis extends.

  According to a third aspect of the present invention, in the first or second aspect, the vertical wall is a convex portion that protrudes into the space from the inner wall on the piston head side. The second sliding part is formed on a side wall part protruding from the piston base part to the space along the entire side surface of the convex part.

According to a fourth aspect of the present invention , in the third aspect of the present invention, the central axes of the piston moving part, the convex part, the piston base part and the side wall part are arranged to coincide with the piston central axis. The convex portion includes a pair of flat surface portions parallel to the piston central axis direction and a pair of arcuate surface portions that are parallel to the piston central axis direction and connect the ends of the flat surface portions.
The piston according to claim 5 is the piston according to claim 3 or 4 , wherein a hole through which the convex portion and the side wall portion pass is formed in the center, and the convex portion and the side wall portion are fitted inside the hole. A disc spring that is accommodated in the space in a combined state and expands and contracts with the reciprocation of the piston moving portion with respect to the piston base is provided.

The piston according to claim 6 is the piston according to any one of claims 1 to 5 , wherein the piston base portion includes a first circumferential contact portion. The piston moving portion includes a second circumferential contact portion that can contact the first circumferential contact portion in the circumferential direction of the piston.

  According to the first aspect, it is possible to make contact at two locations separated in the piston radial direction. For this reason, since the load which acts to incline the piston moving part with respect to the piston base acts on each contact part, it can suppress that each contact part wears.

  According to the second aspect, the piston base and the piston moving part come into contact with each other at two different locations in the direction in which the central axis of the piston extends, and therefore, local wear occurs between the piston base and the piston moving part. Can be suppressed.

  According to the third aspect, since the piston can receive and receive the thrust force that is input, it is possible to suppress local wear between the piston base portion and the piston moving portion. Moreover, it can suppress that a piston moving part inclines with respect to a piston base part.

  According to the fourth aspect, since the expansion and contraction of the disc spring can be guided by the convex portion or the side wall portion, it is possible to prevent the disc spring from shifting in the housing portion.

  According to the fifth aspect, it is possible to prevent the piston moving portion from rotating with respect to the piston base portion.

Sectional drawing which shows the piston which concerns on one Embodiment of this invention. FIG. 2 is an exploded cross-sectional view showing a state where the piston shown in FIG. 1 is disassembled. Sectional drawing of the piston shown along F3-F3 line shown by FIG. Sectional drawing which shows the state in which the piston shown by FIG. 1 has a maximum compression state.

  A piston according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing the piston 10. FIG. 2 is an exploded cross-sectional view showing a state where the piston 10 is disassembled. As shown in FIGS. 1 and 2, the piston 10 includes a piston base portion 20, a piston moving portion 30, a plurality of disc springs 50, and a retaining ring 60.

  The piston base portion 20 has a main body portion 21, a pin boss 22, and a side wall portion 23. As an example, the main body 21 has a circular planar shape and a certain thickness. The main body 21 extends in the piston radial direction D, which is a direction perpendicular to the central axis X0 of the piston 10. The central axis X0 is a straight line passing through the center of the piston 10 when the piston 10 is viewed along the direction in which the central axis X0 extends.

  The pin boss 22 is formed on the main body 21. The pin boss 22 is a part to which a connecting rod (not shown) is connected. In the present embodiment, since the connecting rod is connected via a piston pin (not shown), the pin boss 22 is formed with a hole 22a through which the piston pin passes.

  The side wall 23 is formed on the main body 21 so as to protrude from the surface of the main body 21 opposite to the pin boss 22. The side wall portion 23 will be described in detail later.

  The piston moving part 30 includes a piston head 31, a ring part 33 in which a ring groove 32 is formed, a skirt part 34, and a convex part 35. The skirt portion 34 is integrally formed so as to rise from the peripheral edge portion of the ring portion 33. Therefore, the piston moving part 30 has a concave shape on the inside.

  The convex portion 35 is formed in an inner space formed by the piston head 31, the ring portion 33, and the skirt portion 34, and is disposed inside the piston head 31. The convex portion 35 protrudes inward. The convex portion 35 will be described in detail later.

  The piston base 20 is accommodated inside the piston moving part 30 so as to be capable of reciprocating relative to the piston moving part 30. Since the piston base 20 is accommodated in the piston moving part 30, the center axis X1 of the piston moving part 30 coincides with the center axis X0 of the piston 10. The central axis X1 of the piston moving unit 30 is a straight line passing through the center C1 of the piston moving unit 30 when the piston moving unit 30 is viewed in the direction in which the central axis X1 extends. The reciprocating motion will be described in detail later.

  FIG. 3 is a cross-sectional view of the piston 10 taken along line F3-F3 shown in FIG. FIG. 3 shows the piston 10 cut along a direction perpendicular to the central axis X <b> 0 of the piston 10. As shown in FIG. 3, when the outer peripheral surface 21a of the main body 21 of the piston base 20 is viewed in the direction in which the central axis X0 extends, the shape formed by the edge of the outer peripheral surface 21a is a circle. The shape formed by the edge of the inner peripheral surface 73 of the piston moving unit 30 is a circle when viewed along the direction in which the central axis X0 extends.

  The inside of the piston moving part 30 has a size that allows the main body part 21 to be reciprocated. In order to enable reciprocal movement, a slight gap S <b> 1 is formed between the inner peripheral surface 73 and the outer peripheral surface 21 a of the main body 21. This gap S1 is small. With this gap S1, the piston moving part 30 can reciprocate (moving closer and moving away) with respect to the piston base 20. In FIG. 3, the gap S <b> 1 between the outer peripheral surface 21 a of the main body portion 21 of the piston base portion 20 and the inner peripheral surface 73 of the piston moving portion 30 is exaggerated and drawn greatly. However, in actuality, the piston base 20 is fitted in the piston moving part 30 with a small gap that allows the piston moving part 30 to reciprocate with respect to the piston base 20 (that is, loose fitting). For this reason, the gap S1 is small.

  As shown in FIG. 2, a groove 61 is formed in the inner wall portion of the skirt portion 34 to receive and fix a retaining ring 60 that is continuous in an annular shape. The retaining ring 60 is fixed in the groove 61 in a state in which the piston moving part 30 is assembled to the piston base 20 (the piston base 20 is accommodated in the piston moving part 30 and shown in FIG. 1). Is done.

  As shown in FIG. 1, a part of the retaining ring 60 protrudes from the groove 61 to the inside of the piston moving unit 30. Then, when the main body 21 of the piston base 20 hits the retaining ring 60, the piston base 20 is prevented from being detached from the piston moving part 30.

  The outer peripheral surface 38 of the piston moving unit 30 is parallel to the central axis X <b> 1 of the piston moving unit 30.

  Next, the reciprocation of the piston moving unit 30 with respect to the piston base 20 will be described. As shown in FIG. 1, the reciprocating direction of the piston moving part 30 relative to the piston base 20 is indicated by arrows in the figure. The reciprocating direction A is a linear direction. The reciprocating direction A is parallel to the direction in which the central axis X0 of the piston 10 extends. The reciprocating direction A of the piston moving part 30 with respect to the piston base 20 is parallel to the reciprocating direction of the piston 10 in a cylinder (not shown).

  Next, the side wall part 23 and the convex part 35 are demonstrated. As shown in FIG. 1, the convex portion 35 is formed on the piston moving portion 30 on the side opposite to the piston head 31, and is disposed in the piston moving portion 30.

  The convex portion 35 extends in parallel to the central axis X <b> 1 of the piston moving portion 30. The central axis X2 of the convex portion 35 coincides with (is the same as) the central axis X1. The central axis X2 passes through the center C2 of the convex portion 35 when viewed in the direction in which the central axis X2 extends. When the convex portion 35 is viewed in the direction in which the central axis X2 extends, the center C2 of the convex portion 35 overlaps the center C1 of the piston moving portion 30.

  When the piston base 20 is housed in the piston moving part 30, the central axis X3 passing through the center C3 of the piston base 20 and the central axis X1 passing through the center C1 of the piston moving part 30 are seen in the reciprocating direction A. Or nearly overlap. The central axis of the main body 21 is the same as the central axis X3 of the piston base 20.

  As described above, the term “substantially overlap” means that a gap is formed between the outer peripheral surface 21a of the main body portion 21 of the piston base 20 and the inner peripheral surface 73 of the piston moving portion 30, and will be described later. This is because one of the side wall portion 23 and the convex portion 35 fits into the other so as to be reciprocally movable. Since the piston moving part 30 can be displaced with respect to the piston base part 20 by this gap, the central axes X3 and X1 may be displaced from each other. The central axes X3 and X1 are both parallel to the central axis X0.

  Returning to the description of the convex portion 35. The outer peripheral surface 35a of the convex portion 35 is parallel to each other and faces each other and is parallel to the direction in which the central axis X2 extends, and is parallel to the direction in which the central axis X2 extends and extends between the ends of the flat portion 35b. And a pair of arcuate surface portions 35c to be connected. The shape of the plane (cross section and front end surface) perpendicular to the direction in which the central axis X2 of the convex portion 35 extends is constant in the direction in which the central axis X2 extends, and does not shift in the direction across the direction in which the central axis X2 extends. The same shape (the shape shown in FIG. 3) is maintained.

  For this reason, when a plane (cross section and tip surface) perpendicular to the direction in which the central axis X2 of the convex portion 35 extends is viewed in the direction in which the central axis X2 extends, the shape formed by the outer edge 39 of the convex portion 35 is the convex portion 35. The distance from the center C2 is not uniform. The tip surface 37 of the convex portion 35 is a plane perpendicular to the direction in which the central axis X2 extends.

  As shown in FIG. 1, the side wall portion 23 is formed on the main body portion 21 of the piston base portion 20 on the side opposite to the pin boss 22. The side wall portion 23 has a cylindrical shape and extends parallel to the central axis X3 of the piston base portion 20. When viewed in the direction in which the central axis X4 extends, the central axis X4 of the side wall 23 passes through the center C4 of the side wall 23 and coincides with the central axis X3 of the piston base 20 (the same). The outer peripheral surface 23a of the side wall 23 is parallel to the direction in which the central axis X4 extends (in other words, the reciprocating direction A). As shown in FIG. 3, when the side wall portion 23 is viewed in the direction in which the central axis X <b> 4 extends, the center C <b> 4 of the side wall portion 23 overlaps the center C <b> 3 of the piston base portion 20.

  The shape formed by the outer edge 23b of the side wall 23 is a circle on a plane (cross section and front end surface) perpendicular to the direction in which the central axis X4 of the side wall 23 extends. The shape formed by the outer edge 23b in the plane perpendicular to the direction in which the central axis X4 extends of the side wall portion 23 (the cross section and the front end surface) is constant in the direction in which the central axis X4 extends and crosses the reciprocating direction A. And the same shape (shown in FIG. 3) is maintained.

  The side wall part 23 is formed with a concave part 24 into which the convex part 35 fits in a reciprocating manner. The concave portion 24 opens toward the convex portion 35. The shape formed by the inner edge 24b of the recess 24 in the plane perpendicular to the direction in which the central axis X4 of the side wall 23 extends (the cross section and the tip surface) is the shape of the plane perpendicular to the direction in which the central axis X4 of the projection 35 extends. And a shape that is larger by a gap that allows the convex portion 35 to reciprocate within the concave portion 24.

  Specifically, as shown in FIG. 3, the inner peripheral surface 24a of the recess 24 is parallel to the direction in which the central axis X4 extends and is parallel to each other, and the direction in which the central axis X4 extends. And an arcuate surface portion 26 that connects the end of the flat surface portion 25. The bottom surface 27 is a plane perpendicular to the direction in which the central axis X4 extends.

  In a plane (cross section and tip surface) perpendicular to the reciprocating direction A of the side wall 23, the shape formed by the inner edge 24b is constant in the direction in which the central axis X4 extends, and the direction crosses the direction in which the central axis X4 extends. And the same shape (the shape shown in FIG. 3) is maintained.

  In FIG. 3, the gap S <b> 2 between the outer peripheral surface 35 a of the convex portion 35 and the inner peripheral surface 24 a of the concave portion 24 is exaggerated and drawn greatly. However, actually, the convex portion 35 is fitted in the concave portion 24 with a small gap that allows the piston moving portion 30 to reciprocate with respect to the piston base portion 20 (that is, loose fitting). For this reason, this gap S2 is small.

  Here, in the plane perpendicular to the reciprocating direction A of the piston 10, the gap S <b> 1 between the outer peripheral surface 21 a of the main body portion 21 and the inner peripheral surface 73 of the piston moving portion 30, and the recess 24 of the side wall portion 23. The clearance S2 between the inner peripheral surface 24a and the outer peripheral surface 35a of the convex portion 35 will be described.

  First, the central axes and the reciprocating direction A will be summarized. The center axes X1, X2, X3, and X4 described above are parallel to each other and parallel to the center axis X0 of the piston 10 and the reciprocating direction A. Since the piston base 20 is accommodated in the piston moving part 30, the central axis X0 of the piston 10 coincides with the central axis X1 of the piston moving part 30. When the central axis X3 of the piston base 20 and the central axis X1 of the piston moving part 30 are arranged so as to coincide with each other, all the central axes X1, X2, X3, X4 coincide with the central axis X0. The centers C1, C2, C3, and C4 overlap in the direction in which the central axis X0 extends.

  When the piston 10 reciprocates in the cylinder, it receives a thrust force in the piston radial direction D perpendicular to the piston pin. At this time, the piston 10 is pressed against the inner wall of the cylinder (not shown), and the skirt portion 34 is deformed inside the piston 10. The gaps S1 and S2 are formed at the same time when the outer peripheral surface 21a of the main body 21 and the inner peripheral surface 73 of the piston moving portion 30 come into contact with each other when the piston 10 receives a thrust force and the skirt portion 34 is deformed inside the piston 10. The outer peripheral surface 35a of the convex portion 35 and the inner peripheral surface 24a of the concave portion 24 are set so as to contact each other. This point will be described more specifically.

  First, the gaps S1 and S2 when the piston 10 is not used will be described.

  1 and 3 show a state where the piston moving part 30 and the centers C1 and C3 of the piston base 20 overlap in the reciprocating direction A. FIG. In other words, the center axes X3 and X1 are in an overlapping state. As shown in FIG. 3, when the piston base portion 20 and the piston moving portion 30 are arranged so that the centers C1 and C3 overlap, the outer peripheral surface 21a of the main body portion 21 is parallel to the direction in which the central axis X0 extends. And, in a plane perpendicular to the direction in which the central axis X0 extends, the gap S1 between the inner peripheral surface 73 of the piston moving unit 30 and the outer peripheral surface 21a of the main body 21 of the piston base 20 is continuous in the circumferential direction. The length along the straight line toward the center C3 of the piston base 20 is L1, and is uniform in the circumferential direction of the outer peripheral surface 21a.

  A gap S2 between the inner peripheral surface 24a of the concave portion 24 of the side wall portion 23 and the outer peripheral surface 35a of the convex portion 35 is formed in an annular shape that is continuous in the circumferential direction. In the state shown in FIG. 3, in the range between the arc surface portion 35c of the convex portion 35 and the arc surface portion 26 of the concave portion 24, the length along the straight line toward the center C1 is L2, and is uniform in the circumferential direction. Further, in the range between the flat portion 35b of the convex portion 35 and the flat portion 25 of the concave portion 24, the length along straight lines perpendicular to each other is L2, which is uniform.

  The length L1 is larger than the length L2 (L1> L2). This is determined in consideration of the thrust force received by the piston 10 and the deformation of the piston 10 of the skirt portion 34.

  Next, the gaps S1 and S2 when the piston 10 is used, that is, when the internal combustion engine is operating will be described. When the internal combustion engine is in operation, the piston 10 receives a thrust force in the piston radial direction D perpendicular to the piston pin and is pressed against the cylinder inner wall. At this time, a force acts on the skirt portion 34 in the direction of the central axis X0 as a reaction force of the thrust force. First, the convex part 35 and the concave part 24 which are short gap S2 part contact | abut, and will slide. At this time, the contact portion between the piston base 20 and the piston moving portion 30 is only the convex portion 35 and the concave portion 24, and the load can be transmitted while suppressing an increase in sliding resistance. Further, when the thrust force is increased, particularly in a high-load operation state, the force acting on the skirt portion 34 is increased, and the skirt portion 34 is deformed to the inside of the piston 10 and the outer peripheral surface which is the long gap S1 portion. When 21a and the inner peripheral surface 73 are in contact with each other, a large thrust force is distributed and transmitted at two locations.

  By determining the widths (L1, L2) of the gaps S1, S2 in the state where the piston 10 is not used as described above, the sliding resistance is suppressed by bringing them into contact at one place when the thrust force is small. When the thrust force is applied, the load can be dispersed by making contact at two locations.

  The convex portion 35 is an example of a vertical wall referred to in the present invention. The inner peripheral surface 24a is an example of a second sliding portion referred to in the present invention. The main body portion 21 is an example of a first sliding portion referred to in the present invention.

  Next, the state of the piston 10 will be described. The piston moving part 30 is movable with respect to the piston base part 20 in a direction A1 approaching parallel to the central axis X0 and a direction A2 leaving. A state where the piston moving unit 30 is located farthest from the piston base 20 is referred to as an initial state P1. FIG. 1 shows a state in which the piston 10 is cut parallel to the reciprocating direction A through the center C3 of the piston base 20 in the initial state P1.

  The state in which the piston moving unit 30 is closest to the piston base 20 is defined as a maximum compression state P2. 4 is a cross-sectional view showing a state where the piston 10 in the maximum compression state P2 is cut in the same manner as in FIG. As shown in FIG. 4, the maximum compression state P <b> 2 is a state in which the tip surface 37 of the convex portion 35 is in surface contact with the bottom surface 27 of the concave portion 24, and the piston moving portion 30 cannot approach the piston base 20 any further. For this reason, the length along the direction in which the central axis X0 of the convex portion 35 extends is determined based on a state in which the piston moving portion 30 is closest to the piston base 20 that is set in advance with respect to the piston 10. .

  In a state in which the piston moving part 30 is assembled to the piston base 20, a housing part 70 is formed between the piston base 20 and the piston moving part 30. The accommodating part 70 has a side wall part 23 and a convex part 35 arranged at the center, and has a shape having a space around the side wall part 23 and the convex part 35. The end surface 71 on the piston base 20 side of the housing part 70 is the surface of the main body part 21 of the piston base 20 and is a plane perpendicular to the direction in which the central axis X3 of the piston base 20 extends. The inner peripheral surface 73 extends parallel to the direction in which the central axis X1 of the piston moving unit 30 extends. The internal space of the housing part 70 changes depending on the relative position of the piston moving part 30 with respect to the piston base part 20.

  As shown in FIG. 1, the plurality of disc springs 50 are accommodated in the accommodating portion 70. The disc springs 50 are the same. As shown in FIG. 3, the disc spring 50 has a circular shape when viewed in the reciprocating direction A, and a through hole 51 through which the side wall portion 23 and the convex portion 35 are passed is formed at the center. The shape of the inner edge 53 of the through hole 51 viewed in the reciprocating direction A is a circle. A direction B in which the plurality of disc springs 50 overlap is a direction in which the disc springs 50 are bent, and is parallel to a direction in which the central axis X0 extends.

  The disc spring 50 is accommodated in the accommodating portion 70 in a state in which the initial load is input and compressed in advance. The disc spring 50 urges the piston base 20 in a direction away from the piston moving unit 30 by an elastic force. For this reason, the piston 10 is maintained in the initial state P1. When a force larger than the initial load input to the disc spring 50 is applied to the piston head 31, the disc spring 50 is compressed and the piston moving unit 30 moves toward the piston base 20. That is, the piston 10 is compressed.

  The disc spring 50 has a piston base portion when viewed in the direction in which the central axis X0 extends even in a state in which the piston 10 is deformed by a thrust force, a maximum compression state, and a state in which these two states are combined. It has a size that does not protrude from the outer peripheral surface 21a (outer edge) of the 20 main body portions 21. For this reason, an annularly continuous gap S <b> 3 is provided between the outer edge 52 of the disc spring 50 and the inner peripheral surface 73 of the accommodating portion 70. In FIG. 3, in order to clearly describe the gaps S <b> 1 and S <b> 3, a range F <b> 3 a that is a part of the piston 10 is shown enlarged.

  Next, the relationship between the side wall part 23 and the disc spring 50 is demonstrated. As shown in FIG. 3, when the center C5 of the disc spring 50 overlaps the center C4 of the piston base 20 in the direction in which the center axis X0 extends, the size of the side wall 23 is different from that of the outer peripheral surface 23a of the side wall 23. An annular continuous gap S4 is set between the inner edge 53 of the spring 50.

  Even when the disc spring 50 moves in a direction intersecting with the direction in which the central axis X0 extends (for example, a direction perpendicular to the direction in which the central axis X0 extends), the outer edge 52 of the disc spring 50 has an inner circumference. The size is set such that the inner edge 53 of the disc spring 50 can contact the outer peripheral surface 23 a of the side wall portion 23 and stop the disc spring 50 from shifting before contacting the surface 73.

  Specifically, in the initial state P1, and in a state where the center C2 of the convex portion 35, the center C5 of the disc spring 50, and the center C3 of the piston base 20 overlap each other in the reciprocating direction A, the gap S4 is It is formed in an annular shape that is continuous in the direction. The length of the gap S4 along the straight line toward the center C3 in a plane perpendicular to the direction in which the central axis X0 extends is L4, which is a uniform length in the circumferential direction.

  In the above state, the length along the straight line toward the center C3 of the gap S3 between the inner peripheral surface 73 of the piston moving unit 30 and the outer edge 52 of the disc spring 50 is L3, and is a uniform length in the circumferential direction. And L3> L4. Even if the lengths L3 and L4 are in the operating state of the piston 10, the relationship in which the length along the straight line toward the center C1 of the gap S3 is larger than the length along the straight line toward the center C1 of the gap S4 is maintained. Is set to In FIG. 3, the gaps S3 and S4 are greatly exaggerated for explanation. However, in practice, the gaps S3 and S4 are small.

  Next, an example of assembly work of the piston 10 will be described. After the plurality of disc springs 50 are accommodated in the piston moving part 30, the piston base 20 is accommodated in the piston moving part 30. At this time, the position is adjusted so that the convex portion 35 fits into the concave portion 24 of the side wall portion 23. When the convex portion 35 is accommodated in the concave portion 24 of the side wall portion 23, the piston base portion 20 can be pushed into the piston moving portion 30 as it is.

  When the shape of the plane (cross section and tip surface) perpendicular to the direction in which the central axis X2 of the convex portion 35 extends is viewed in the direction in which the central axis X2 extends, the distance from the center C1 of the piston moving unit 30 is not uniform. Since the piston moving portion 30 does not rotate with respect to the piston base 20 due to the shape, the piston base 20 can be pushed into the piston moving portion 30 smoothly.

  When the piston base portion 20 is accommodated in the piston moving portion 30, the retaining ring 60 is then fitted into the groove 61. When this operation is finished, the assembly of the piston 10 is finished.

  Next, the operation of the piston 10 will be described. The piston 10 moves in the cylinder under the pressure of the combustion chamber in a cylinder (not shown). This movement is transmitted to the crankshaft via the connecting rod. As a result, the crankshaft rotates.

  Since the piston base 20 is connected to the crankshaft via the connecting rod, it does not rotate during movement in the cylinder. Further, the piston moving part 30 does not rotate with respect to the piston base part 20.

    The disc spring 50 expands when compressed. At this time, even if the disc spring 50 moves in a direction crossing the reciprocating direction A, the outer edge 52 of the disc spring 50 does not contact the inner peripheral surface 73 of the piston moving portion 30 by the side wall portion 23. Movement is not hindered.

  The above operation is the same when the piston 10 returns from the compressed state toward the initial state P1.

  In the piston 10 formed in this way, when the thrust force received by the piston 10 is small, the outer peripheral surface 21a of the main body 21 and the inner peripheral surface 73 of the piston moving unit 30 do not come into contact with each other, so that the sliding resistance can be suppressed. it can. When the thrust force received by the piston 10 is large, the inner peripheral surface 24 a of the concave portion 24 of the side wall portion 23 and the outer peripheral surface of the convex portion 35 come into contact with each other, and the inner peripheral surface 21 a of the main body portion 21 and the piston moving portion 30 The peripheral surface 73 contacts. As described above, the load applied to the contact portion between the piston base portion 20 and the piston moving portion by the thrust force received by the piston 10 by making contact at two locations shifted from each other in the reciprocating direction A and the piston radial direction D is the above two locations. Therefore, the wear of the piston 10 can be suppressed.

  Further, since the convex portion 35 is surrounded by the side wall portion 23 and is fitted in the concave portion 24 around the outer peripheral surface 35 a, the piston moving portion 30 can be prevented from being inclined with respect to the piston base portion 20.

  Further, the gap S4 between the inner edge 53 of the disc spring 50 and the outer peripheral surface 23a of the side wall 23 is set to be larger than the gap S3 between the outer edge 52 of the disc spring 50 and the inner peripheral surface 73. Therefore, the side wall portion 23 can prevent the disc springs 50 from shifting in the piston radial direction D, and the outer edge 52 of the disc spring 50 comes into contact with the inner peripheral surface 73 of the piston moving portion 30 to move the piston moving portion 30. Will not hinder the movement.

  Further, when viewed in the direction in which the central axis X0 extends, the shape of the flat surface (tip surface and cross section) perpendicular to the direction in which the central axis X0 extends of the convex portion 35 has a distance from the center C1 of the piston moving unit 30 that is The concave portion 24 of the side wall portion 23 has a uniform shape, and the convex portion 35 is fitted with a gap (that is, similar to a plane perpendicular to the direction in which the central axis X0 of the convex portion 35 extends, Since the piston moving part 30 tries to rotate in the circumferential direction of the piston with respect to the piston base 20, the convex part 35 comes into contact with the inner surface of the concave part 24. It is possible to prevent the piston moving part 30 from rotating with respect to the base part 20. The side wall portion 23 is an example of a first circumferential contact portion. The convex portion 35 is an example of a second circumferential contact portion.

  In the present embodiment, the side wall portion 23 and the convex portion 35 are used as a structure for stopping the rotation of the piston moving portion 30 in the circumferential direction of the piston with respect to the piston base portion 20. However, it is not limited to this. For example, the piston base 20 may be separately provided with a protrusion that protrudes toward the piston moving part 30, and the piston moving part 30 may be formed with a recess into which the protrusion is fitted. The recess has a gap with the protrusion so as not to hinder the reciprocation of the piston moving part 30 relative to the piston base 20. When the piston moving part 30 tries to rotate with respect to the piston base 20 by fitting the protrusion into the recess, the protrusion comes into contact with the inner surface of the recess. This prevents the piston moving part 30 from rotating in the piston circumferential direction with respect to the piston base 20. In this case, the protrusion becomes the first circumferential contact portion, and the concave portion becomes the second circumferential contact portion.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. For example, the shape of the outer peripheral edge of the convex portion and the shape of the inner peripheral edge of the concave portion viewed in the piston central axis direction may be elliptical. Further, the convex portion may be provided on the piston base side, and the side wall portion may be provided on the piston moving portion side. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above.

  DESCRIPTION OF SYMBOLS 10 ... Piston, 20 ... Piston base, 21 ... Main-body part (1st sliding part), 22 ... Pin boss | hub, 22a ... Hole, 23 ... Side wall part (2nd circumferential direction contact part), 24a ... Inner peripheral surface (Second sliding part), 30 ... piston moving part, 31 ... piston head, 34 ... skirt part, 35 ... convex part (vertical wall), 50 ... disc spring, X0 ... central axis, D ... piston radial direction.

Claims (6)

A piston base with pin bosses;
A piston moving part which has a piston head and a skirt part, has a space on the inside, accommodates the piston base part, and can reciprocate in the direction in which the piston central axis extends with respect to the piston base part. ,
The piston moving part includes a vertical wall having a side surface parallel to the piston central axis on an inner wall of the piston head forming the space,
The piston base extends in the piston radial direction, and a first end faces the inner wall on the skirt portion side forming the space, and is slidable with the inner wall on the skirt portion side with the reciprocation. A moving portion, and a second sliding portion that faces the side surface of the vertical wall and is slidable with the side surface along with the reciprocating motion.
The first sliding portion has a gap between the first sliding portion and the inner wall on the skirt portion side, and between the second sliding portion and the side surface of the vertical wall. the piston base in the said gap between the inner wall of the skirt portion side, said second sliding portion and the longitudinal said than the gap between the side wall piston central axis in a plane perpendicular to the direction of extension piston, characterized in that a long length along the straight line toward the center of. The piston according to claim 1, wherein the first sliding portion and the second sliding portion are arranged so as to be shifted in a direction in which the piston central axis extends. The vertical wall is a convex portion protruding into the space from the inner wall on the piston head side,
3. The piston according to claim 1, wherein the second sliding portion is formed on a side wall portion that protrudes from the piston base portion to the space along the entire side surface of the convex portion. . The piston moving part, the convex part, the piston base part, and the central axis of the side wall part are arranged to coincide with the piston central axis,
The convex portion includes a pair of plane portions parallel to the piston central axis direction and a pair of arc surface portions parallel to the piston central axis direction and connecting between the ends of the plane portions.
The piston according to claim 3, characterized in that: A hole through which the convex part and the side wall part pass is formed in the center, and the piston movement with respect to the piston base is accommodated in the space with the convex part and the side wall part fitted inside the hole. The piston according to claim 3 or 4 , further comprising a disc spring that expands and contracts as the portion reciprocates. The piston base includes a first circumferential contact portion,
The said piston moving part comprises the 2nd circumferential contact part which can contact | abut with the said 1st circumferential contact part in the piston circumferential direction. Any one of Claims 1-5 characterized by the above-mentioned. The piston according to claim 1.

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