JPH06174090A - Position pin support structure - Google Patents

Abstract

PURPOSE:To provide a position pin support structure for an internal combustion engine, which can lower bearing stress, reduce wear in the piston pin support section, and is advantageous for a reduction in compression height. CONSTITUTION:A piston pin 2 is of a two part type structure, and is made up of an outer pin for supporting a connecting rod, and of an inner pin 22 for supporting a piston 1. When explosion stroke takes place within a combustion chamber, the piston 1 is lowered down to the side of a lower dead center, that is, to the direction indicated by an arrow head Y2. A flat inner wall surface section 12c within the pin hole 12 of the piston 1, comes in contact with a flat outer wall surface section 22c of the inner pin 22 of the piston pine 1. In this case, since the contact of both of the aforesaid sections is kept at face contact, bearing stress acting on both the inner pin 22 and the pin hole 12 is thereby made low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support structure for a piston pin. This structure can be applied to a piston of an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, a piston pin is used to connect a piston and a connecting rod. The piston pin is fitted in a pin hole formed in the piston. Here, the pressure received by the piston during the explosion process of the internal combustion engine is transmitted to the connecting rod via the piston pin.

By the way, conventionally, as shown in FIG. 10, the cross-sectional shape of the pin hole 100 is circular and the cross-sectional shape of the piston pin 200 is circular. Further, a minute clearance F1 is formed between the inner peripheral surface of the pin hole 100 and the outer peripheral surface of the piston pin 200. This clearance F1 depends on the material of the piston pin 200 and the like,
Generally, when the internal combustion engine is driven, it tends to increase due to the difference in thermal expansion.

[0004]

Conventionally, as described above, the pin hole 100 has a circular cross-sectional shape, and the piston pin 200 has a circular cross-sectional shape. Therefore, during the explosion process, the piston 300 receives the pressure of the combustion chamber.
Is lowered in the direction of the arrow A1, the upper part 100a of the inner peripheral surface of the pin hole 100 of the piston 300 is moved to the piston pin 20.
It contacts the upper part of the outer peripheral surface of 0. At this time, the contact situation is
Line contact state extending in the direction perpendicular to the paper surface of FIG. 10, or
It can be said that the state is close to the line contact state.

Therefore, the surface pressure acting on the pin boss provided with the pin hole 100 becomes large, and it is easy to induce wear of the pin boss and increase the required rigidity thereof. Furthermore, in recent years
The compression height, which greatly affects the weight of the entire piston, that is, the distance between the pin hole shaft center and the top surface of the piston head, is being reduced for the purpose of weight reduction and noise reduction. Then, since the pin hole 100 has a circular shape, there is a limitation in reducing the compression height.

The present invention has been made in view of the above situation, and an object thereof is to reduce the surface pressure acting on the pin hole, which is advantageous in terms of wear reduction, and also to reduce the compression height. However, it is to provide an advantageous piston pin support structure.

[0007]

A piston pin support structure of the present invention comprises a piston having a pin hole extending in a direction orthogonal to the piston drive direction, and a piston pin fitted in the pin hole. In the support structure of No. 3, the inner wall surface of the pin hole of the piston has a flat inner wall surface portion at least on the piston head side, and the piston pin has a flat outer wall surface portion facing the flat inner wall surface portion of the pin hole. It is characterized by that.

[0008]

In the explosion stroke, the piston receives the pressure of the combustion chamber and the piston descends to the bottom dead center side. In this case, the flat inner wall surface portion of the pin hole of the piston contacts the flat outer wall surface portion of the piston pin. At this time, the contact between the two is maintained in a surface contact state.

[0009]

【Example】

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. The piston 1 is formed with a piston head portion 10 that receives the pressure during the explosion stroke. Further, a pin hole 12 is formed in the pin boss portion 1a of the piston 1. The pin hole 12 is in the piston driving direction (arrows Y1, Y
(2 directions).

The piston pin 2 has a two-part structure and is formed by an outer pin 20 for supporting the connecting rod 3 and an inner pin 22 for supporting the piston 1. Inner pin 22
Both ends of are locked by snap rings 2k. Figure 2
As shown in (A), the outer pin 20 has an arc-shaped outer wall surface 20a.
And an odd-shaped through hole 20b. Different shape through hole 20b
Is formed of a flat inner wall surface portion 20c and an arcuate inner wall surface portion 20e. As shown in FIG. 2B, the inner pin 22
Has a cross-sectional shape corresponding to the irregularly shaped through hole 20b,
It has a flat outer wall surface portion 22c and an arcuate outer wall surface portion 22e. A through hole 22i is formed in the inner pin 22.

Further, as shown in FIG. 2C, the small end hole 32 of the small end portion 30 of the connecting rod 3 has a circular shape and corresponds to the arc-shaped outer wall surface 20a of the outer pin 20.
As shown in FIG. 2D, the pin hole 12 of the piston 1 has a different shape corresponding to the cross-sectional shape of the inner pin 22, and is formed by a flat inner wall surface portion 12c and a circular arc inner wall surface portion 12e. Has been done. It should be noted that FIG.
The state where the inner pin 22 is press-fitted into 0b is shown. By press fitting,
Both of them are integrated in a detent state.

Next, the case where the piston pin 2 is assembled to the piston 1 will be described. That is, as can be understood from FIG. 1, the small end hole 32 of the small end portion 30 of the connecting rod 3 is formed.
The outer pin 20 is fitted inside by "clearance fitting". In this state, the small end portion 30 is inserted into the hollow portion 1f of the piston 1 from the direction of arrow C1. Then, insert the inner pin 22 into the arrow D1.
It is fitted into the pin hole 12 from the direction, and further fitted into the odd-shaped through hole 20b of the outer pin 20.

As in the conventional case, the piston 1 has a structure shown in FIG.
As shown in, the first land 1h, the second land 1i, the third land 1j, the first ring groove 1m, the second ring groove 1n, and the oil ring groove 1s are formed. Piston 1 mentioned above
Is installed in the bore of a cylinder of an internal combustion engine. When the explosion stroke is performed in the combustion chamber of the internal combustion engine, the piston head portion 10 receives the pressure of the combustion chamber, so that the piston 1
Descends toward the bottom dead center side, that is, in the direction of arrow Y2. In this embodiment, as described above, the inner pin 22 having a different cross-section is fitted in the pin hole 12 having a different cross-section, so that the piston pin 2 is fixed to the piston 1 in a non-rotating state, and therefore the internal combustion engine. The piston pin 2 does not swing with respect to the piston 1 during the driving of, and the connecting rod 3 swings with respect to the outer pin 20.

As described above, when the piston 1 descends toward the bottom dead center side, that is, in the direction of the arrow Y2, as can be understood from FIG. 4, the flat inner wall surface portion 12c of the pin hole 12 of the piston 1 is formed.
However, the flat outer wall surface portion 2 of the inner pin 22 of the piston pin 2
Contact 2c. At this time, the contact between the two is maintained in a surface contact state, so that the surface pressure acting on the inner pin 22 and the pin hole 12 becomes small. Therefore, the required rigidity and wall thickness of the pin boss portion 1a around the pin hole 12 can be reduced, which is advantageous for weight reduction of the piston 1.

Further, in the present embodiment, even if the clearance F2 between the piston 1 and the piston pin 2 is somewhat large, the piston 1 hits the piston pin 2 in a surface contact state as described above, which is advantageous for suppressing abnormal noise. . For example, when the piston pin 2 is made of ceramics and the piston 1 is made of iron-based or aluminum-based metal, the coefficient of thermal expansion of ceramics is smaller than that of metal, so that when the internal combustion engine is driven. The clearance F2 tends to increase under the influence of the temperature rise of the internal combustion engine, which may cause abnormal noise. In this respect, in the present embodiment, as described above, the piston 1 contacts the inner pin 22 in the surface contact state, so the clearance F2
Even if is slightly large, it is advantageous for suppressing abnormal noise.

By the way, when the outer diameter of the inner pin 22 is set to about the outer diameter of the conventional piston pin, the following effects can be expected. (A) Since the outer pin 20 into which the inner pin 22 is press-fitted is provided, the overall rigidity of the piston pin 2 is increased, which is advantageous in improving bending shear strength. (B) Since the outer pin 20 has a large diameter, the inner diameter of the small end hole 32 into which the outer pin 20 fits increases. Therefore, if the surface pressure acting on the small end hole 32 of the small end portion 30 of the connecting rod 3 is the same as in the conventional case, the width dimension (L1 shown in FIG. 1) of the small end portion 30 of the connecting rod 3 can be reduced. With such a structure, as shown in FIG. 1, the pin boss portion 1a can be located closer to the center, and it becomes easy to thrust-support the small end portion 30 of the connecting rod 3 with the pin boss portion 1a. Therefore, it is also advantageous for shortening the axial length of the inner pin 22 and improving the bending resistance of the inner pin 22.

As can be understood from FIG. 1, the inner pin 22
Both ends of are locked by snap rings 2k, so that the degree of press-fitting of the inner pin 22 into the outer pin 20 is increased, or the coefficient of thermal expansion of the inner pin 22 is larger than that of the outer pin 20, If the materials of the outer pin 20 and the inner pin 22 are selected, the degree of press-fitting increases as the temperature of the internal combustion engine rises, which is advantageous for preventing the inner pin 22 from coming off, and the snap ring 2k can be expected to be abolished.

The outer diameter of the inner pin 22 may be smaller than that of a conventional piston pin. (Second Embodiment) The piston pin 2 according to the first embodiment described above has a non-oscillating structure with respect to the piston 1. However, the present invention is not limited to this, and the piston pin 6 may be replaced by a piston pin 6 as in the second embodiment described below. Alternatively, the piston pin 6 and the connecting rod 8 may be swung with respect to No. 5 to prevent them from rotating.

A second embodiment will be described with reference to FIGS. The piston 5 according to the second embodiment shown in FIG. 5 has basically the same structure as the piston 1 of the first embodiment, and in principle, the same parts are designated by the same reference numerals. As shown in FIG. 5, a pin hole 52 is formed in the pin boss portion 5a of the piston 5. The pin hole 52 has a cross-sectionally different shape, and is formed by a flat inner wall surface portion 52c and a circular arc inner wall surface portion 52e. Similarly, the piston pin 6 also has a different cross-sectional shape and includes a flat outer wall surface portion 6c and a circular arc outer wall surface portion 6e. A through hole 6i is formed in the piston pin 6.

Further, as shown in FIG. 7, the connecting rod 8
The small end portion 80 has a small end hole 82 formed therein. The small end hole 82 has a different shape corresponding to the cross-sectional shape of the piston pin 6. That is, the small end hole 82 includes a flat inner wall surface portion 82c and a circular arc inner wall surface portion 82e. Therefore, the protrusion amount of the small end portion 80 of the connecting rod 8 is Δ
K (see FIG. 7) is shortened. Therefore, it is advantageous in reducing the compression height, and the small end 8
The space volume of the hollow portion 1f of the piston 5 in which 0 is fitted is secured to that extent, which is advantageous for improving the cooling performance by the hollow portion 1f.

In this example, the connecting rod 8
The piston pin 6 is press-fitted (the press-fitting margin is, for example, −10 μm to −30 μm) into the small end hole 82, and both are fixed in a non-rotating state. Therefore, the connecting rod 8 and the piston pin 6 swing integrally with the piston 5. In the second embodiment, when the explosion stroke is performed in the combustion chamber of the internal combustion engine, the piston head portion 50 receives the pressure of the combustion chamber, so the piston 5 descends in the direction of arrow Y2. At this time, as in the first embodiment, as can be understood from FIG. 5, the flat inner wall surface portion 52c of the pin hole 52 of the piston 5 is replaced by the flat outer wall surface portion 6c of the piston pin 6.
Contact with the surface contact state. Therefore, like the first embodiment, it is advantageous to reduce the surface pressure acting on the pin hole 52.

Now, in FIG. 5, the compression height H is basically determined by the height of each land, the groove width of each ring groove, the height of the ring supporting portion 1p, and the radius of the pin hole 52. However, there is a limit in narrowing the height of each land and the groove width of each ring groove. Therefore, compression height H
The height hα of the ring support portion 1p (see FIG. 5) and the distance hβ (see FIG. 5) from the axis P1 of the pin hole 52 to the upper portion of the pin hole 52 are reduced in order to reduce It is valid. In this regard, in this embodiment, since the flat inner wall surface portion 52c is formed on the upper portion of the pin hole 52, the radius of the pin hole 52 in the vertical direction can be shortened by ΔA as can be understood from FIG. 6, and the compression height H Is also advantageous in reducing the weight of the piston 5 and reducing the weight of the piston 5. Furthermore, there is an advantage that the center of gravity of the piston 5 can be brought close to the axis P1 of the piston pin 6.

In this example, the piston pin 6 fixed to the connecting rod 8 swings with respect to the pin hole 52. Therefore, as shown in FIG. 6, the radius of curvature of the rounded portions at both ends of the flat inner wall surface portion 52c of the pin hole 52 is set to R ₁
When the radius of curvature of the rounded portions at both ends of the flat outer wall surface portion 6c of the piston pin 6 is R ₂ , the piston pin 6
Considering the swing angle of R ₂ , R ₁ , clearance F 2
To set. Specifically, R ₂ > R ₁ .

The swing of the piston pin 6 will be described with reference to the schematic diagram shown in FIG. FIG. 8 is a schematic view of the swinging form (R ₂ and R ₁ are omitted).
In FIG. 8, the piston pin 6 is indicated by the arrow V in the pin hole 52.
When swinging in one direction, the portion 6u of the piston pin 6
The piston pin 6 is allowed to swing by a swinging angle θ1 until the point hits the portion 52u of the pin hole 52. Also,
When the piston pin 6 swings in the direction of the arrow V2, the portion 6u 'of the piston pin 6 is the portion 52u' of the pin hole 52.
Until it hits, that is, the swing angle θ1 ′ is allowed to swing the piston pin 6. Therefore, in the above schematic diagram, the piston pin 6 is allowed to swing by (θ1 + θ1 ′).

(Ripple effect associated with reduction of compression height H) If the compression height H can be reduced, the following ripple effect can be obtained. That is,
By reducing the compression height H, the weight of the piston can be reduced. Therefore, the reciprocating weight of the piston is reduced, the exciting force is reduced, and it is possible to contribute to the reduction of vibration and noise, and particularly to the reduction of muffled noise in a high rotation range. Therefore, in an internal combustion engine equipped with a balance shaft for reducing muffled noise, it is easy to simplify and eliminate the balance shaft, which contributes to cost reduction.

In order to confirm the effect of reducing the vibration and noise, the vertical vibration of the engine mount and the sound inside the vehicle at the center of the front seat and the window of the front seat were measured at a rotation speed of 1000 to 6000 rpm. confirmed. Furthermore, as the weight of the piston becomes lighter, the internal combustion engine blows up better, which contributes to improvement in acceleration. Further, as the compression height H is reduced, the height of the cylinder block can be reduced, so that the overall height of the internal combustion engine can be reduced.
The mountability in the engine room is improved. Therefore, it is also advantageous to mount the internal combustion engine upright. Further, as the compression height H is reduced, the moment about the axis of the pin hole is reduced, the piston posture is improved, and thus the weight of the land portion can be reduced. Also, with the improvement of piston posture, the piston ring posture is also improved, which can contribute to the reduction of the tension of the piston ring, the reduction of friction, the improvement of the sealing property between the piston ring and the bore inner peripheral surface, and the consumption of blow bio-oil. Can contribute to the reduction of In addition, since the moment acting on the piston is reduced, it is possible to contribute to the reduction of thrust force and the impact sound of the piston. Further, as the thrust force is reduced, the piston skirt surface pressure is reduced, so that various ripple effects can be expected, which can contribute to the reduction of wear of the skirt sliding surface and the bore sliding surface.

Besides, the present invention is not limited to the embodiments described above and shown in the drawings. For example, FIG.
As shown in the example shown in Fig. 6, the shape of the through hole 6i of the piston pin 6 can be made similar to the outer wall of the piston pin 6 in consideration of the uniform thickness and the like. Can be carried out.

[0028]

According to the piston pin support structure of the present invention, when the piston moves to the bottom dead center side, the flat inner wall surface portion of the pin hole of the piston contacts the flat outer wall surface portion of the piston pin. Therefore, the contact between the two is maintained in a surface contact state. Therefore, the surface pressure acting on the pin hole can be reduced. Therefore, it is advantageous in reducing the required rigidity and wall thickness in the vicinity of the pin hole, and is advantageous in reducing the weight of the piston.

Further, according to the support structure of the piston pin of the present invention, since the flat inner wall surface portion is formed at least on the piston head side of the inner wall surface of the pin hole, the diameter of the pin hole in the piston driving direction. Can be shortened, which is advantageous in reducing the compression height. Further, it is also advantageous in reducing the weight of the piston. This can be expected to have numerous ripple effects.

[Brief description of drawings]

FIG. 1 is a sectional view of a piston equipped with a connecting rod and a piston pin.

2A is a sectional view of an outer pin, FIG. 2B is a sectional view of an inner pin, FIG. 2C is a sectional view of a small end hole of a small end portion of a connecting rod, and FIG. 4) is a sectional view of a pin hole of a piston.

FIG. 3 is a perspective view showing a state in which an outer pin and an inner pin are assembled.

FIG. 4 is a configuration diagram of a main part for explaining an operating state.

FIG. 5 is a front view of a piston according to a second embodiment.

FIG. 6 is a configuration diagram showing a state in which a piston pin is fitted in a pin hole.

FIG. 7 is a front view of a connecting rod.

FIG. 8 is a schematic diagram illustrating swing of a piston pin with respect to a pin hole.

FIG. 9 is a front view of a piston pin according to a modification of the second embodiment.

FIG. 10 is a configuration diagram of a main part for explaining an operation state according to a conventional example.

[Explanation of symbols]

In the figure, 1 is a piston, 12 is a pin hole, 12c is a flat inner wall surface portion, 2 is a piston pin, 20 is an outer pin, 22 is an inner pin, 22c is a flat outer wall surface portion, and 3 is a connecting rod.

Claims (1)

[Claims] 1. A piston pin support structure comprising a piston having a pin hole extending in a direction orthogonal to the piston driving direction, and a piston pin fitted into the pin hole. A wall surface has a flat inner wall surface portion at least on the piston head side, and the piston pin has a flat outer wall surface portion facing the flat inner wall surface portion of the pin hole. Support structure.