JP2012137063A - Piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston that suppresses wear of an inner surface of a piston.SOLUTION: The piston 10 includes: a piston base part 20; a piston moving part 30 configured to reciprocate relative to the piston base part 20; a storing part 70 formed between the piston base part 20 and the piston moving part 30, a capacity of which varies as the piston moving part 30 reciprocates relative to the piston base part 20; a disk spring 50 stored in the storing part 70, and stretching and contracting while following the movement of the piston moving part 30 relative to the piston base part 20 as the capacity of the storing part 70 varies; and a protective coil spring 40 stored in the storing part 70 while being interposed between an outer circumferential edge 52 in a piston radial direction of the disk spring 50 and a side surface 73 of the storing part 70, and stretching and contracting in synchronization with the stretching and contraction of the disk spring 50.

Description

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

  Conventionally, a variable compression ratio piston including an outer piston and an inner piston has been proposed. A disc spring is accommodated between the outer piston and the inner piston. When the pressure in the combustion chamber increases, the outer piston lowers due to the deflection of the disc spring, and therefore, there is one that prevents the pressure in the combustion chamber from exceeding the intended pressure (see, for example, Patent Document 1).

JP-A-6-17665

  The diameter of the disc spring changes when it is bent. For this reason, in the piston of patent document 1, when a disc spring expands and contracts, it is possible that the outer peripheral edge part of a disc spring contacts the inner surface of a piston. It is considered that the inner surface of the piston is worn by the outer peripheral end of the disc spring contacting the inner surface of the piston.

  An object of this invention is to provide the piston which can suppress abrasion of the inner surface of a piston.

  The piston according to claim 1 is formed between a piston base in which a piston boss is formed, a piston moving part capable of reciprocating with respect to the piston base, and the piston base and the piston moving part. A housing part whose volume changes with the reciprocation of the piston moving part relative to the piston base part, and is housed in the housing part, and follows the movement of the piston moving part relative to the piston base part as the volume of the housing part changes. A disc spring that expands and contracts, and a protection that is accommodated in the accommodating portion and is interposed between the end portion of the disc spring in the radial direction of the piston and the inner wall of the accommodating portion, and expands and contracts in synchronization with the expansion and contraction of the disc spring. A member.

  The piston according to claim 2 is the piston according to claim 1, wherein the end portion is an outer peripheral end portion or an inner peripheral end portion of the disc spring, and the protection member is an outer peripheral end portion of the disc spring or It is a coil spring formed in a spiral shape along the inner peripheral end.

  According to a third aspect of the present invention, in the piston according to the second aspect, a plurality of the disc springs are stacked in the reciprocating direction. The coil spring contacts an outer peripheral end or an inner peripheral end of the disc spring in a stretched state in which the disc spring has a minimum diameter.

  According to a fourth aspect of the present invention, in the piston according to the second or third aspect, the pitch of the coil spring is not more than twice the plate thickness of the disc spring when the volume of the accommodating portion is maximum.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the inner surface of a piston wears.

Sectional drawing which shows the piston which concerns on the 1st Embodiment of this invention. Sectional drawing which shows the state by which the piston shown by FIG. 1 was decomposed | disassembled. Sectional drawing which shows the piston which concerns on the 2nd Embodiment of this invention. Sectional drawing which shows the piston which concerns on the 3rd Embodiment of this invention.

  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 protective coil spring 40, a plurality of disc springs 50, and a retaining ring 60.

  The piston base 20 has a main body 21 and a piston boss 22. As an example, the main body 21 has a circular planar shape and a certain thickness. The piston boss 22 is formed on the main body 21. The piston boss 22 has a hole 24 through which a connecting rod (not shown) is connected via a piston pin.

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

  The piston base 20 is housed inside the piston moving unit 30. The piston moving unit 30 is movable with respect to the piston base 20. The reciprocating direction A of the piston moving part 30 relative to the piston base part 20 is indicated by an arrow in the figure. The reciprocating direction A is a linear direction. The reciprocating direction A is a direction parallel to the outer surface 38 of the piston moving unit 30. The outer surface 38 extends in the same direction. More specifically, the reciprocating direction A of the piston moving unit 30 with respect to the piston base 20 is parallel to the reciprocating direction of the piston in a cylinder (not shown).

  A groove 37 into which the retaining ring 60 is fitted is formed in the piston moving unit 30. The retaining ring 60 supports the piston base 20 so that the piston base 20 accommodated in the piston moving part 30 does not come off.

  Here, the state of the piston 10 will be described. As described above, the piston moving part 30 is movable with respect to the piston base part 20 in the approaching direction A1 parallel to the reciprocating movement direction A and in the leaving direction A2. As shown in FIG. 1, a state where the piston moving unit 30 is located farthest from the piston base 20 is defined as an initial state P1. FIG. 1 shows an initial state P1. In the initial state P1, the main body portion 21 is in contact with the retaining ring 60, and therefore, the movement of the piston moving portion 30 relative to the piston base portion 20 is suppressed. A state (not shown) in which the piston moving unit 30 is closest to the piston base 20 is defined as a maximum compression state. The maximum compression state is a state in which a disc spring 50 described later is bent to the maximum.

  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. In the present embodiment, the accommodating portion 70 is formed by the inner wall 36 of the piston moving portion 30 and the main body portion 21 of the piston base portion 20.

  An end surface 71 on the piston base 20 side of the accommodating portion 70 is a surface of the main body portion 21 of the piston base 20 and is a surface perpendicular to the reciprocating direction A. The planar shape of the end surface 71 viewed in the reciprocating direction A is a circle. The end surface 72 of the accommodating portion 70 on the piston moving portion 30 side is a surface perpendicular to the reciprocating direction A, and the planar shape seen in the reciprocating direction A is a circle. A side surface 73 of the accommodating portion 70 is an inner surface of the inner wall 36 of the piston moving portion 30 and extends in parallel with the reciprocating direction A. 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. The inner wall 36 having the side surface 73 is an example of the inner wall referred to in the present invention.

  The protective coil spring 40 is accommodated in the accommodating portion 70. The protective coil spring 40 is an example of a protective member in the present invention. The protective coil spring 40 is formed in a spiral shape along an outer peripheral end portion 52 of a disc spring 50 described later. The protective coil spring 40 is arranged in a posture in which the expansion / contraction direction is parallel to the reciprocating direction A. The cross-sectional shape of the protective coil spring 40 is a circle.

  In the wall portion that forms the housing portion 70, holding grooves 74 and 75 that hold both end portions of the protective coil spring 40 are formed in the end wall portion of the piston moving portion 30 and the end wall portion of the piston base portion 20. Has been. As shown in FIG. 1, a gap is provided between the outer surface of the protective coil spring 40 and the side surface 73 of the accommodating portion 70. This is to suppress wear on the side surface 73 of the accommodating portion 70 due to expansion and contraction of the protective coil spring 40.

  As shown in FIG. 1, in this embodiment, three disc springs 50 are used as an example. The number of disc springs 50 is not limited to three. There may be one or other plural numbers such as four or five. The disc springs 50 are the same. The disc spring 50 has a circular planar shape. A plurality of disc springs 50 are stacked and accommodated in the protective coil spring 40. A direction B in which the plurality of disc springs 50 overlap is a direction in which the disc springs 50 extend and contract, and is parallel to the reciprocating direction A. In the initial state P <b> 1, among the plurality of disc springs 50, the disc spring 50 disposed at one end contacts the end surface 71 of the accommodating portion 70, and the disc spring 50 disposed at the other end is the end surface 72 of the accommodating portion 70. To touch.

  The natural frequency of the disc spring 50 and the natural frequency of the protective coil spring 40 are different. In other words, the protective coil spring 40 having a natural frequency different from the natural frequency of the disc spring 50 is selected.

  In addition, although the diameter of the disc spring 50 is changed by expanding and contracting, the characteristic of changing the diameter with respect to expansion and contraction varies depending on the shape and size of the disc spring. Therefore, there are those having the maximum diameter when the disc spring is extended and those having the maximum diameter when the disc spring is compressed, but either disc spring can be applied. In the present embodiment, description will be made using a disk spring having a maximum diameter in a compressed state.

  As shown in FIG. 1, in the initial state P <b> 1 of the piston 10, the disc spring 50 when the piston 10 is in the maximum compression state is interposed between the outer peripheral end 52 of the disc spring 50 and the inner surface of the protective coil spring 40. The clearance S1 is formed in consideration of deflection (expansion to the outside). Specifically, the gap S1 is such that the disc spring 50 does not contact the protective coil spring 40 so that the deflection of the disc spring 50 is not hindered by the disc spring 50 contacting the protective coil spring 40. Is taken into account.

  In the piston 10 configured as described above, even if the position of the disc spring 50 is shifted in the accommodating portion 70, the side surface 73 of the accommodating portion 70 is protected by the protective coil spring 40. The end 52 does not contact the side surface 73. For this reason, it is suppressed that the side surface 73 of the accommodating part 70 is worn.

  In addition, since the natural frequency of the protective coil spring 40 is different from the natural frequency of the disc spring 50, the protective coil spring 40 and the disc spring 50 can be prevented from resonating.

  Moreover, the structure which follows the movement of the piston moving part 30 with respect to the piston base part 20 can be simply made by using an elastic body as an example of the protection member of the present invention. Moreover, a protection member can be simply comprised by using a coil spring as an elastic body.

The coil spring 40 is formed by spirally forming a linear spring material at a constant pitch. The pitch is preferably large enough that the disc spring 50 does not pass through the gap between the coil springs 40. . For example, if a coil spring whose pitch is equal to or less than twice the plate thickness of the disc spring 50 in the initial state P1 is used, the outer peripheral end of each disc spring of the plurality of disc springs 50 is covered with the coil spring more than half a circle. The spring can be prevented from passing through the pitch of the coil spring and coming into contact with the side surface 73 of the accommodating portion 70. The initial state P1 is an example of a state in which the volume of the housing portion is maximized, which is referred to in the present invention.

  Next, a piston according to a second embodiment of the present invention will be described with reference to FIG. In addition, the structure which has the same function as 1st Embodiment attaches | subjects the code | symbol same as 1st Embodiment, and abbreviate | omits description. In this embodiment, a protective coil spring 80 is used. Other structures are the same as those in the first embodiment. Hereinafter, a structure different from that of the first embodiment will be described in detail.

  FIG. 3 is a cross-sectional view showing the piston 10 of the present embodiment. The protective coil spring 80 is an example of a protective member in the present invention. As shown in FIG. 3, the protective coil spring 80 has a size that contacts the entire circumferential direction of the outer peripheral end 52 of the disc spring 50 in the initial state P1. The protective coil spring 80 is formed in a spiral shape along the outer peripheral end portion 52 of the disc spring 50. The initial state P1 is an example of the expansion / contraction state in which the diameter of the disc spring is minimized as referred to in the present invention.

  Specifically, the protective coil spring 80 has a diameter that contacts the outer peripheral end 52 of the disc spring 50 in an expanded and contracted state where the diameter of the disc spring 50 is minimized. For this reason, the inner side 81 of the protective coil spring 80 contacts the entire circumferential direction of the outer peripheral end 52 of the disc spring 50. The diameter of the protective coil spring 80 increases following the increase in the diameter of the disc spring 50.

  Even when the disc spring 50 is compressed to the maximum compression state (the maximum compression state of the piston 10) between the outer side portion 82 of the protection coil spring 80 and the side surface 73 of the housing portion 70, the protection coil spring 80 is A gap S <b> 2 is provided so that the deflection of the disc spring 50 is not obstructed by contact with the side surface 73 of the housing portion 70. In other words, even when the piston 10 is in the maximum compression state, the protective coil spring 80 does not contact the side surface 73 of the housing portion 70.

  In the present embodiment, in addition to the effects of the first embodiment, the protective coil spring 80 compresses the plurality of disc springs 50 from the outside toward the inside, so that the disc springs 50 are prevented from shifting from each other. The

  Next, a piston according to a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, configurations having the same functions as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, the protective member 110 is used in place of the protective coil spring 40 as the protective member in the present invention. Other structures are the same as those in the first embodiment. Hereinafter, a structure different from that of the first embodiment will be described in detail.

  FIG. 4 is a cross-sectional view showing the piston 10. As shown in FIG. 4, the protection member 110 is accommodated in the accommodation portion 70. The protection member 110 is made of an elastically deformable resin material (for example, rubber), and houses the disc spring 50 inside. The protection member 110 has a shape having a circumferentially continuous wall that covers the outer peripheral end portion 52 of the disc spring 50 in the circumferential direction, and has a cylindrical shape as an example. The inner surface 111 of the protection member 110 is bonded and fixed to the outer peripheral end 52 of the disc spring 50. For this reason, the outer peripheral ends 52 of the plurality of disc springs 50 are connected via the protection member 110.

  The protection member 110 can be elastically deformed following the movement of the piston moving unit 30 with respect to the piston base 20. The natural frequency of the protection member 110 is different from the natural frequency of the disc spring 50. In the initial state P1, even when the disc spring 50 is compressed to the maximum compression state between the outer surface 112 of the protection member 110 and the side surface 73 of the housing portion 70 (the maximum compression state of the piston 10), the protection member 110 is A gap S <b> 3 is provided so that the deflection of the disc spring 50 is not obstructed by contacting the side surface 73 of the housing portion 70. In other words, even when the piston 10 is in the maximum compression state, the protection member 110 does not contact the side surface 73 of the housing portion 70.

  In the present embodiment, the same effect as in the first embodiment can be obtained. Moreover, the resonance suppression effect of the disc spring 50 and the protection member 110 can further be enhanced by using rubber having a higher attenuation rate than the metal material as the protection member.

  Further, since the protection member 110 is made of resin (in this embodiment, rubber is used as an example), the inner surface 111 of the protection member 110 can be bonded to the outer peripheral end 52 of the disc spring 50. As a result, the protection member 110 and the plurality of disc springs 50 can be managed as one member, so that the number of components of the piston 10 can be reduced.

  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, when using a piston in which a column for preventing the rotation of the piston moving part relative to the piston base is provided inside the disc spring, the above-mentioned between the column and the inner peripheral end 53 of the disc spring is used. By arranging the elastic member, the same effect as that of the first embodiment can be obtained. Even when such a piston is used, the contact pressure between the disc spring and the elastic member is larger on the outside than the inside of the disc spring, so that the surface pressure is dispersed and the above-described effects can be maintained for a long time. it can.

  Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. Furthermore, you may combine the component covering different embodiment suitably.

  DESCRIPTION OF SYMBOLS 10 ... Piston, 20 ... Piston base, 22 ... Piston boss, 30 ... Piston moving part, 40 ... Protection coil spring (protection member), 50 ... Disc spring, 52 ... Outer edge part (end part), 53 ... Inner circumference End part (end part), 70 ... accommodating part, 80 ... protective coil spring (protective member), 110 ... protective member.

Claims (5)

A piston base on which a piston boss is formed;
A piston moving part capable of reciprocating with respect to the piston base;
An accommodating portion that is formed between the piston base and the piston moving portion and has a volume that changes as the piston moving portion reciprocates with respect to the piston base;
A disc spring which is accommodated in the accommodating portion and expands and contracts following the movement of the piston moving portion with respect to the piston base as the volume of the accommodating portion changes.
A protective member that is accommodated in the accommodating portion and is interposed between an end of the disc spring in the radial direction of the piston and an inner wall of the accommodating portion, and expands and contracts in synchronization with expansion and contraction of the disc spring. A characteristic piston. The end is an outer peripheral end or an inner peripheral end of the disc spring,
2. The piston according to claim 1, wherein the protection member is a coil spring formed in a spiral shape along an outer peripheral end or an inner peripheral end of the disc spring. A plurality of the disc springs are stacked in the reciprocating direction,
The piston according to claim 2, wherein the coil spring is in contact with an outer peripheral end or an inner peripheral end of the disc spring in a stretched state in which the diameter of the disc spring is minimized. 4. The piston according to claim 2, wherein the coil spring has a pitch equal to or less than twice a plate thickness of the disc spring when the volume of the housing portion is maximum. 5. A plurality of the disc springs are stacked in the reciprocating direction,
2. The piston according to claim 1, wherein the protection member is formed of a resin and connects outer peripheral ends or inner peripheral ends of the plurality of disc springs.

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