JP2015007387A - Piston of internal combustion engine and assembling method for the piston - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston of an internal combustion engine in a simple fluid-spring structure for enabling a variation in capacity of a combustion chamber (a variable compression ratio), and to provide an assembling method for the piston.SOLUTION: The piston of the internal combustion engine includes a piston base part 2 having a top wall 4 forming a piston top surface, a peripheral side wall 6 extending from the outer periphery of the top wall in the axial direction, and a piston skirt 6a, and a piston moving part 3 capable of reciprocating in the center-axis direction of the piston with respect to the piston base part. The piston base part is divided into a top wall portion 2a including the top wall and a skirt portion 2b including the piston skirt by the peripheral side wall, the end of the top wall portion and the end of the skirt portion divided therefrom can be fitted to each other, the end of the top wall portion and the end of the skirt portion are fixed by an insertion hole 28 and an insertion member 29 formed in the radial direction of the piston, and a receiving seat 12 for supporting the piston moving part is formed on the inner face of the skirt portion. Thus, the variable-compression-ratio piston is provided in a simple structure, where a sealed space S formed between the piston top part and the piston moving part functions as a fluid spring including air.

Description

  The present invention relates to a piston for an internal combustion engine and a method for assembling the piston.

Reciprocating internal combustion engines mounted on vehicles tend to downsize using a supercharger (increase the intake air amount with the supercharger and reduce the exhaust amount instead) to reduce vehicle fuel efficiency. .
However, such an internal combustion engine, on the other hand, tends to cause knocking at medium and high loads.

Therefore, in the internal combustion engine, in order to suppress the occurrence of knocking at medium and high loads, a chamber space is separately formed in a part of the combustion chamber as disclosed in Patent Document 1, and a fluid spring structure is formed in the chamber space. A proposal has been made to change the volume of the combustion chamber according to the pressure in the combustion chamber by the action of the fluid spring (variable compression ratio).
However, since this technique incorporates a chamber space and a fluid spring structure in the combustion chamber of the internal combustion engine, the internal combustion engine tends to be considerably complicated.

JP 2012-97656 A

Therefore, it is conceivable to apply this technique to the piston.
However, most of the variable compression ratio pistons depend on the elastic force of the elastic body or change the volume of the combustion chamber depending on the hydraulic pressure, and the volume of the combustion chamber is changed using a fluid spring. There is no piston. Moreover, the variable compression ratio piston tends to have a complicated structure, but there is no piston that has been stepped down to the simplification of the fluid spring.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a piston for an internal combustion engine and a piston assembling method capable of changing the volume of the combustion chamber (variable compression ratio) with a simple fluid spring structure.

  The invention according to claim 1 is a piston base having a top wall forming the piston top surface, a peripheral side wall extending in the axial direction from the outer periphery of the top wall, and a piston skirt, and reciprocating in the piston central axis direction with respect to the piston base. A piston of an internal combustion engine having a movable piston moving part, wherein the piston base is divided by a peripheral wall into a top wall part including a top wall and a skirt part including a piston skirt, and an end of the divided top wall part The end part of the skirt part and the end part of the skirt part are formed so as to be fitable, and the end part of the top wall part and the end part of the skirt part are fixed by an insertion hole formed in the piston radial direction and an insertion member inserted into the insertion hole. The inner surface of the skirt portion has a receiving seat that supports the piston moving portion.

The invention described in claim 2 has an elastic body that urges in the direction of the center axis of the piston, and the elastic body is housed between the piston base and the piston moving part.
According to a third aspect of the present invention, the insertion member is inserted such that one end surface thereof faces the inside of the piston base, the end surface has a recess in the piston radial direction, and the piston moving portion has a recess on the side surface in the piston axial direction. It has decided to have the convex part formed so that insertion was possible.

According to a fourth aspect of the present invention, the piston moving portion has an oil passage that receives hydraulic pressure supplied from the outside, and the convex portion is connected to the oil passage and protruded by the oil pressure from the oil passage.
According to a fifth aspect of the present invention, there is provided a piston base portion having a top wall forming a piston top surface, a peripheral side wall extending in the axial direction from the outer peripheral portion of the top wall, and a piston skirt, and in a piston central axis direction with respect to the piston base portion. It consists of a piston moving part that can reciprocate, and an elastic body that is housed between the piston base part and the piston moving part and urges in the direction of the piston center axis. The piston base part includes a top wall part including a top wall and a piston skirt. The end of the top wall and the end of the skirt are formed so that they can be fitted together, and the end of the top wall and the end of the skirt are arranged in the piston radial direction. A piston assembling method in which an insertion hole is formed and a receiving seat for supporting the piston moving portion is formed on the inner surface of the skirt portion. First, the opening portion of the divided peripheral side wall portion is inserted into the skirt portion so as to overlap the receiving seat. Assemble the ston moving part and the elastic body in this order, then match the insertion holes while fitting the end part of the top wall part and the end part of the skirt part, and insert the insertion member into the matching insertion hole, The piston base was assembled.

According to the invention of claim 1, the piston has a sealed space formed between the piston top portion and the piston moving portion functioning as a fluid spring containing air, and the combustion chamber according to the pressure in the combustion chamber of the internal combustion engine. The volume of the is variable (compression ratio variable).
In particular, in the piston using this fluid spring, the end portion of the skirt portion containing the piston moving portion and the end portion of the top wall portion are fitted, and the insertion member is inserted into the insertion hole formed in the end portion. Since the sealed space is formed between the piston top and the piston moving part, the function of the fluid spring can be easily ensured.

Therefore, a variable compression ratio piston using a fluid spring can be provided with a simple structure.
According to the second and fifth aspects of the present invention, the variable compression ratio of the piston can be easily set according to the internal combustion engine by adding an elastic body that assists the fluid spring. Moreover, even if it has an elastic body, the top wall portion and the skirt portion can be easily fixed while the piston moving portion is accommodated by the operation of inserting the insertion member into the insertion hole as in the case of claim 1.

According to the invention of claim 3, the piston base is held at a position where the target compression ratio is obtained by inserting the convex portion of the lower piston portion into the concave portion of the end face of the insertion member. In addition, since the concave portion to which an impact load is easily applied is formed in the insertion member having high rigidity and strength, the existing member can be used, and a simple and inexpensive structure is sufficient.
According to invention of Claim 4, a convex part can be easily protruded using the hydraulic pressure supplied from the outside.

(A) is a top view of the piston which concerns on the 1st Embodiment of this invention, (b) is a front sectional view similarly. (A) is a front sectional view in which the piston is divided into a piston base and a piston moving part. Front sectional view. The front sectional view which divided | segmented each part of the piston in assembly order. (A) is a top view of the piston which concerns on the 2nd Embodiment of this invention, (b) is a front sectional view similarly. The front sectional view which decomposed | disassembled each part of the piston. The front sectional drawing which shows the assembly method of the piston in order. FIG. 7 is a front sectional view sequentially illustrating a piston assembly method following FIG. 6. The front sectional view showing the piston concerning a 3rd embodiment of the present invention. FIG. 9 is a cross-sectional plan view taken along line AA in FIG. 8. The front sectional view showing the time when the piston is held in the lowest compression ratio state, for example. The front sectional view showing the piston concerning a 4th embodiment of the present invention.

The present invention will be described below based on the first embodiment shown in FIGS.
FIG. 1 (a) shows a plan view of a variable compression ratio piston to which the present invention is applied, which is a piston that varies the compression ratio, and FIG. 1 (b) shows a front sectional view of the piston. FIG. 3 shows an exploded view of the piston.
The structure of the variable compression ratio piston will be described with reference to FIGS. 1 to 3. In the figure, reference numeral 1 denotes a piston body of the piston. As shown in FIG. 2A, the piston body 1 is composed of a combination of an upper piston portion 2 that is a piston base portion and a lower piston portion 3 that is a piston moving portion.

Of these, the upper piston portion 2 has a top wall 4 that forms the top surface of the piston, a peripheral side wall 6 that extends from the outer periphery of the top wall 4 along the piston axial direction, and an end from the peripheral side wall 6 that extends in the piston axial direction. It has a piston skirt 6a and is formed in a concave shape.
An annular receiving seat 12 is formed at the lowermost portion of the inner peripheral surface of the peripheral side wall 6. Here, the receiving seat 12 is formed of an L-shaped cross-sectional portion protruding inward from the inner peripheral surface of the peripheral side wall 6. A plurality of piston ring grooves 13 are provided on the outer peripheral surface of the peripheral side wall 6.

  Further, the upper piston portion 2 will be described in detail. As shown in FIG. 2 (b), the upper piston portion 2 is a peripheral side wall 6, a concave top wall portion 2a including the top wall 4, a piston skirt 6a, It is divided into a cylindrical skirt portion 2 b including the receiving seat 12. Here, the point near the piston skirt 6a of the peripheral side wall 6 is divided into the dividing wall 26 and divided into the top wall 2a and the skirt 2b.

  A columnar guide post portion 8 protrudes from the center of the inner surface of the top wall 4 of the divided top wall portion 2a. Moreover, the edge part of the divided | segmented top wall part 2a and the edge part of the skirt part 2b are fixed so that attachment or detachment is possible using the fitting part 27 which mutually fits, and the fixing pin 29 which is an insertion member. Specifically, as shown in FIG. 2B, the fitting portion 27 is, for example, an insertion portion 30a formed of an annular convex wall portion on the end surface of the peripheral wall portion 6 serving as an end portion of the top wall portion 2a. And a receiving portion 30b formed of an annular stepped wall portion that is paired with the convex wall portion is provided on the end face of the peripheral side portion 6 that is the end portion of the skirt portion 2b. These insertion part 30a and the receiving part 30b fit. In addition, a pair of pin holes 28 (corresponding to the insertion holes of the present application) are formed in each portion of the wall portion of the insertion portion 30a and the wall portion of the receiving portion 30b that overlap in the piston radial direction, for example, four wall portions in the circumferential direction. Is formed. The pin hole 28 of the insertion part 30a is a through hole, and the pin hole 28 of the receiving part 30b is a bottomed hole (concave). Then, by inserting (press-fitting) the fixing pins 29 into the respective pin holes 28 from the outside, the divided top wall portion 2a and skirt portion 2b are fixed, and the upper piston portion 2 is assembled.

On the other hand, the lower piston portion 3 has a disk-shaped base portion 14, a pair of pin boss portions 16 protruding from one side surface of the base portion 14, and a guide tube portion 9 protruding from the center of the other side surface of the base portion 14. Configured.
The base portion 14 of the lower piston portion 3 is accommodated in the upper piston portion 2 through the dividing portion 26 so as to be capable of reciprocating. Along with this accommodation, the base portion 14 is supported by the receiving seat 12, the guide tube portion 9 and the guide post portion 8 are slidably fitted, and the pin boss boss portion 16 is disposed outside the upper piston portion 2, and the top wall A sealed space S is formed between 4 and the base portion 14. As shown in FIGS. 1 and 3, the sealed space S is formed so that the inner peripheral surface of the peripheral side wall 6 can accommodate the base portion 14 so as to be slidable, and between the sliding surfaces (with the outer peripheral surface of the base portion). The space between the inner peripheral surfaces of the peripheral side walls is formed by sealing with, for example, lubricating oil. Thereby, the sealed space S functions as a fluid spring containing air, which is an important element for changing the compression ratio.

The volume of the sealed space S forming the fluid spring is variable according to the pressure of the combustion chamber (internal combustion engine) applied from the top surface of the piston, and the volume of the combustion chamber is variable (variable compression ratio). In other words, the upper piston portion 2 of the variable compression ratio piston has a protruding state (state indicated by a solid line) indicated by an arrow in FIG. The variable compression ratio having this fluid spring (sealed space S) is configured to vary from a high compression ratio state α that raises to a retreat state (state indicated by a two-dot chain line), that is, a low compression ratio state β that lowers the compression ratio. The piston is easily assembled.

  Specifically, as shown in FIG. 3, first, the base portion 14 of the lower piston portion 3 is fitted into the divided skirt portion 2b from the opening portion 7 as shown in FIG. It is piled up on the receiving seat 12 on the side. At this time, lubricating oil is applied to the inner surface of the peripheral side wall 6 in advance. The base portion 14 is fitted in the skirt portion 2b so as to be able to reciprocate in the piston axial direction while being sealed with lubricating oil. The pin boss part 16 (part connected to the connecting rod) protrudes out of the skirt part 2b.

Thereafter, the top wall 2a is assembled to the end of the divided skirt 2b. For this, first, the insertion portion 30a of the top wall portion 2a and the receiving portion 30b of the skirt portion 2b are fitted, and the two are fitted so that the pin holes 28 match each other. The fixing pin 29 is press-fitted (inserted) into the matched pin hole 28. Thereby, the top wall part 2a and the skirt part 2b are fixed.
With this fixing, a sealed space S is formed between the top wall 4 (piston top portion) and the base portion 14 (lower piston portion 3) supported by the receiving seat 12 as shown in FIG. In this sealed space S, the trapped air functions as a fluid spring, and supports the lower piston portion 3 so as to be displaceable in the piston axial direction.

Thereby, the variable compression ratio piston for changing the volume of the combustion chamber is assembled.
Therefore, in the compression ratio variable piston, the structure in which the skirt portion 2b and the top wall portion 2a in which the lower piston portion 3 is fitted so as to be able to reciprocate is fixed by the fixing pin 29 forms the sealed space S as a fluid spring as it is. Because of the structure, a variable compression ratio piston can be easily manufactured.
4 to 7 show a second embodiment of the present invention.

This embodiment is a modification of the first embodiment, and an elastic body, for example, a plurality of disc spring members 20 arranged in series, is accommodated between the upper piston portion 2 and the lower piston portion 3, and the upper piston portion. 2, the force in the piston axial direction is added.
4 is a plan view and a front sectional view of a variable compression ratio piston to which a disc spring member 20 is added, and FIG. 5 is a sectional view in which each part of the variable compression ratio piston is disassembled.

  In order to assist the function of the fluid spring formed in the sealed space S, the structure in which the disc spring member 20 (elastic body) is added can be obtained by adding the disc spring member 20 that assists the elastic force of the insufficient fluid spring. The piston compression ratio can be easily set according to the internal combustion engine. In addition, since the disc spring member 20 to be added may be a spring member that only assists the fluid spring, the work load when assembling the piston is minimized.

FIGS. 6A and 6B and FIGS. 7A to 7C show a procedure for assembling the variable compression ratio piston.
Here, an annular protrusion 10 is provided on the inner surface of the top wall 4 to suppress the disc spring member 20.
The piston assembly method will be described. First, the lower piston portion 3 and the disc spring member 20 are sequentially arranged from the opening portion 7 at the end of the skirt portion 2b divided as shown in FIGS. 6 (a) and 6 (b). The base part 14 of the lower piston part 3 and the disc spring member 20 are assembled to the receiving seat 12 so as to overlap in order. Next, the top wall 2a is assembled.

At this time, the top wall portion 2a is aligned with the pin hole 28 of the skirt portion 2b, and the guide post portion 8 protruding from the top wall 4 as shown in FIG. Insert into the protruding guide tube 9. Using the guide tube portion 9 as a guide, the insertion portion 30a at the end of the top wall portion 2a and the receiving portion 30b at the end of the skirt portion 2b are fitted.
At this time, since the disc spring member 20 is in a free state, as shown in FIG. 7A, the protruding portion 10 abuts against the disc spring member 20 before the pin holes 28 match each other. Therefore, as shown in FIG. 7B, a load F is applied, and the pin hole 28 of the insertion portion 30a and the pin hole 28 of the receiving portion 30b are matched with each other while fitting the top wall portion 2a and the skirt portion 2b. .

Thereafter, the fixing pin 29 is press-fitted (inserted) into the matched pin hole 28 as shown in FIG. As a result, the top wall 2a is fixed to the skirt 2b while forming a sealed space S between the top wall 2a and further pushing the disc spring member 20 into the skirt 2b.
For this reason, even if the disc spring member 20 is added, as in the first embodiment, the fitting of the top wall portion 2a and the skirt portion 2b and the operation of inserting the fixing pin 29 into the insertion hole 28 can be easily performed. The top wall 2a and the skirt 2b can be fixed and the sealed space S can be formed.

8 to 10 show a third embodiment of the present invention.
This embodiment is a modification of the first and second embodiments, and uses a fixed pin 29 that fixes the divided upper piston portion 2 to change the variable compression ratio piston to the target compression ratio, here most The compression ratio is kept low so that the compression ratio is low.
In this holding structure, the pin hole 28 of the receiving portion 30b is formed from a through hole so that the insertion end of the fixing pin 29 faces the inside of the skirt portion 2b, and each fixing pin facing the upper piston portion 2 is formed. 29 (four) end surfaces (one side end surface; end surface on the distal end side in the insertion direction) are provided with a circular lock hole 33 formed by a concave portion recessed in the piston radial direction, and locked to the outer peripheral end of the base portion 14 of the lower piston portion 3. A structure is provided in which a convex portion that can be inserted into the hole 33, here, an insertion pin portion 35 is provided.

  Specifically, as shown in FIGS. 8 and 9, the insertion pin portion 35 has a concave shape that is recessed in the piston radial direction at each portion (four locations) of the outer peripheral surface of the base portion 14 of the lower piston portion 3. A structure is used in which the cylinder portion 36 is formed and the pin member 37 is reciprocally moved in the cylinder portion 36. Specifically, the pin member 37 is supported by a guide member 38 installed in the cylinder portion 36 so as to be displaceable in the reciprocating direction (piston radial direction). At the same time, it is urged in a retracting direction by a return spring member 39 housed in the cylinder portion 36 and is housed in the base portion 14 so as to protrude.

  Further, in the base 14, for example, the cylinder portions 35 (four pieces) are divided into two groups, and these are communicated with the journal surfaces 16b of the boss holes 16a of the pin boss portions 16 (two pieces) for each group. Paths 40a and 40b (two systems) are provided. That is, one end of each oil passage 40a, 40b opens to the journal surface 16b, and the other end opens to the cylinder portion 36, respectively.

  Here, the journal surface 16b is a portion that is rotatably connected to a connecting rod 42 (hereinafter referred to as a connecting rod 42) via a piston pin 41 (both are shown by a two-dot chain line in FIG. 6). The connecting rod 42 is formed with a relay oil passage 44 (illustrated by a two-dot chain line in FIG. 8) for guiding control hydraulic pressure from a crankshaft (not shown) to the journal surface 16b. When the hydraulic pressure is supplied to the cylinder portion 36 through the oil passages 40 a and 40 b, the pin member 37 is pushed out (projected) from the base 14 and inserted into the lock hole 33 of the fixing pin 29.

At this time, the lock hole 33 is set at a position where the target compression ratio is maintained, in this case, at a position where the compression ratio is low.
That is, as shown in FIG. 10, when the control oil pressure is applied to the pin member 37, the pin member 37 and the lock hole 33 are fitted at a low compression ratio. As a result, the upper piston portion 2 is locked, and the low compression ratio state is maintained as it is.

  Thereby, the upper piston part 2 continues to hold the position of the target compression ratio (FIG. 10). Moreover, the lock hole 33 to which an impact load is easily applied is formed on the fixing pin 29 having high rigidity and strength (to fix the top wall portion 2a and the skirt portion 2b). There is no need for a structure, and existing parts can be reused, making the structure simple and inexpensive. In particular, when the oil passages 40a and 40b for guiding the hydraulic pressure supplied from the outside to the cylinder portion 36 are formed in the lower piston portion 3, the pin member 37 can be protruded with a simple structure.

The oil passage structure for projecting the pin member 37 is not limited to two systems, but may be one system or another structure. Of course, the structure may be maintained in a high compression ratio state.
FIG. 11 shows a fourth embodiment of the present invention.
In this embodiment, the variable compression ratio piston of the first embodiment is combined with the technology of the third embodiment that restricts the movement of the lower piston portion 3 with hydraulic pressure and maintains the target compression ratio. It is. Even if it does in this way, there exists an effect similar to embodiment mentioned above.

However, in FIGS. 4 to 11, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
The present invention is not limited to the above-described embodiments, and may be implemented in various ways without departing from the spirit of the present invention. In the embodiment described above, an example in which a disc spring member is used as an elastic body has been described. However, the present invention is not limited thereto, and other elastic bodies may be used.

2 Upper piston part (piston base)
2a Top wall part 2b Skirt part 3 Lower piston part (piston moving part)
4 Top wall 6 Peripheral side wall 6a Piston skirt 12 Receiving seat 28 Pin hole (insertion hole)
29 Fixing pin (insertion member)
30a Insertion part 30b Receiving part S Sealed space

Claims (5)

A piston base having a top wall forming a piston top surface, a peripheral side wall extending in an axial direction from an outer periphery of the top wall, and a piston skirt;
A piston moving part capable of reciprocating in the piston central axis direction with respect to the piston base part;
A piston of an internal combustion engine having
The piston base is
The peripheral wall is divided into a top wall including the top wall and a skirt including the piston skirt,
The divided end portion of the top wall portion and the end portion of the skirt portion are formed so as to be fitted,
The end portion of the top wall portion and the end portion of the skirt portion are fixed by an insertion hole formed in the piston radial direction and an insertion member inserted into the insertion hole,
The piston of the internal combustion engine, wherein an inner surface of the skirt portion has a receiving seat that supports the piston moving portion. It has an elastic body that urges in the direction of the piston center axis,
The piston of the internal combustion engine according to claim 1, wherein the elastic body is accommodated between the piston base and the piston moving part. The insertion member is inserted with one end face facing the inside of the piston base,
The end surface has a recess in the piston radial direction,
The piston of the internal combustion engine according to claim 1 or 2, wherein the piston moving part has a convex part formed on the side surface in the piston axial direction so as to be able to be inserted into the concave part. The piston moving part has an oil passage that receives hydraulic pressure supplied from the outside,
The piston of the internal combustion engine according to claim 3, wherein the convex portion is connected to the oil passage and protrudes by oil pressure from the oil passage. A piston base having a top wall forming a piston top surface, a peripheral side wall extending in an axial direction from an outer periphery of the top wall, and a piston skirt;
A piston moving part capable of reciprocating in the piston central axis direction with respect to the piston base part;
It is housed between the piston base and the piston moving part, and consists of an elastic body that urges in the piston central axis direction,
The piston base is
The peripheral wall is divided into a top wall including the top wall and a skirt including the piston skirt,
The divided end portion of the top wall portion and the end portion of the skirt portion are formed so as to be fitted,
An insertion hole is formed in the end portion of the top wall portion and the end portion of the skirt portion in the piston radial direction,
A method of assembling a piston having a receiving seat for supporting the piston moving part on the inner surface of the skirt part,
First, the piston moving part and the elastic body are assembled in this order so as to overlap the receiving seat from the divided opening part of the peripheral side wall part into the skirt part,
Thereafter, the insertion holes are fitted together while fitting the end portion of the top wall portion and the end portion of the skirt portion,
A piston assembling method, wherein an insertion member is inserted into the matched insertion hole to assemble the piston base.

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