JP2010038048A - Piston of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight piston of an internal combustion engine capable of maintaining an attitude as much as possible when reciprocating. <P>SOLUTION: A first sidewall 5 to a fourth sidewall 8 extend along a virtual surface F including the axis 21 of a piston pin 20 and being a surface with a surface extending in a thrust direction and an anti-thrust direction supposed. The first sidewall 5 and a third sidewall 7 are connected to each other, and the connecting part thereof forms a first skirt 9. A second sidewall 6 and a fourth sidewall 8 are connected to each other, and a connecting part thereof forms a second skirt 10. Each of the first skirt 9 and the second skirt 10 has a surface composed of a cylindrical surface formed by approximately the same diameter as the outside diameter of a piston top 2 and made to slidably contact with the bore of the internal combustion engine during the operation of the engine. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a piston for an internal combustion engine.

  Conventionally, pistons improved for the purpose of reducing the weight of the piston and stabilizing the posture of the piston during reciprocating motion are known. For example, it has a crown portion, a skirt portion below the crown portion, and a pair of pin boss portions that are integrally provided inside the crown portion and the skirt portion and face each other, and an intermediate portion of the skirt portion is deleted A piston is known (see Patent Document 1). In addition, for example, a piston for an internal combustion engine in which a land portion and a skirt portion are formed discontinuously is known (see Patent Document 2). In addition, the cylindrical skirt portion provided at the lower portion of the crown portion is divided and formed in the vertical and horizontal directions, and the divided upper skirt portion and lower skirt portion are separated from both sides of the pair of pin boss portions holding the piston pins. A piston of an internal combustion engine that is supported by a plurality of extended support arms is known (see Patent Document 3).

JP-A-6-193733 Japanese Patent Laid-Open No. 6-101666 Japanese Patent Laid-Open No. 6-53743

  The weight reduction of the piston contributes to the reduction of friction and the wear of the sliding portion with the cylinder liner. Further, the piston suppresses the swinging phenomenon during the reciprocating motion and stabilizes the posture, thereby reducing the oil consumption and suppressing the blow-by. The pistons disclosed in the above-mentioned patent documents aim to reduce the weight of the piston and maintain the posture of the piston, but all have room for improvement.

  Therefore, an object of the present invention is to provide a piston for an internal combustion engine that is further reduced in weight and can maintain its posture as much as possible during reciprocating motion.

  The piston of the internal combustion engine disclosed in the present specification that solves this problem includes a pin boss that is formed on the back surface side of the piston top portion and that is provided with a piston pin, and a sidewall that is provided on the side of the pin boss. The piston includes a skirt provided at the end of the sidewall. The sidewall includes the axis of the piston pin and extends from the pin boss so as to extend along a virtual plane extending in the thrust direction and the anti-thrust direction.

  The oscillation of the piston occurs about the axis of the piston pin. Therefore, assuming a virtual surface that includes the axis of the piston pin and extends in the thrust direction and the anti-thrust direction, a sidewall is provided along the virtual surface. The swing of the piston can be effectively suppressed by providing a skirt at the end of the sidewall. In particular, the swinging of the piston at the top and bottom dead center can be effectively suppressed, and the posture of the piston can be maintained.

  In the piston disclosed in this specification, the sidewall is extended in such a direction as to effectively suppress the swinging of the piston, and a skirt is provided at the end thereof. And the thickness of the piston is reduced as much as possible within the limit that ensures the strength of the piston, and the weight of the piston is reduced.

  According to the piston of the internal combustion engine of the present invention, it is possible to reduce the weight of the piston and to maintain the posture during the reciprocating motion of the piston.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view of a piston (hereinafter simply referred to as “piston”) 1 of an internal combustion engine according to the present embodiment. FIG. 2 is a view schematically showing the piston 1 as seen from the pin hole, that is, the axial direction of the piston pin. FIG. 3 is a diagram schematically showing the piston 1 as viewed from the bottom side. FIG. 4 is a view schematically showing the piston 1 as seen from the thrust side. FIG. 5 is a diagram schematically showing the piston 1 as a cross section taken along line AA in FIG. 4 when viewed from the axial direction of the pin hole (piston pin).

  The piston 1 is made of aluminum, includes a piston top portion 2, and includes a first pin boss 3 and a second pin boss 4 which are disposed to face each other on the back surface side. The first pin boss 3 and the second pin boss 4 are provided with pin holes 3a and 4a, respectively. As shown in FIG. 2, a piston pin 20 is fitted into the pin holes 3 a and 4 a, and a connecting rod (not shown) is attached to the piston 1. In FIG. 2, reference numeral 21 indicates the axis of the piston pin, and reference numeral R indicates the diameter dimension of the piston pin 20.

  A first sidewall 5 and a second sidewall 6 are provided on the side of the first pin boss 3. A third side wall 7 and a fourth side wall 8 are provided on the side of the second pin boss 4.

  The first sidewall 5 extends from the first pin boss 3 in the thrust direction. The second sidewall 6 extends from the first pin boss 3 in the anti-thrust direction. The third sidewall 7 extends from the second pin boss 4 in the thrust direction. The fourth sidewall 8 extends from the second pin boss in the anti-thrust direction.

  These first side wall 5 to fourth side wall 8 are extended along a virtual plane F shown in the drawing. The imaginary surface F is assumed to include a surface including the axis 21 of the piston pin 20 and extending in the thrust direction and the anti-thrust direction.

  The first side wall 5 and the third side wall 7 are joined together, and the joined part forms a first skirt 9. The second side wall 6 and the fourth side wall 8 are joined together, and the joined part forms a second skirt 10. The surfaces of the first skirt 9 and the second skirt 10 are formed of cylindrical surfaces having a diameter substantially the same as the outer diameter of the piston top 2 and are in sliding contact with a bore (not shown) of the internal combustion engine during engine operation.

  The thickness Ts in the height direction of the first skirt 9 and the second skirt 10 is set to be equal to or less than the thickness Tw in the height direction of the first side wall 5 to the fourth side wall 8. Temporarily, the thickness Ts in the height direction of the first skirt 9 and the second skirt 10 is thicker than the thickness Tw in the height direction of the first sidewall 5 to the fourth sidewall 8, and the first pin boss 3 and the second pin boss. The closer to 4, the lower the strength, the lower the strength. Therefore, in the piston 1, the dimensions of the first skirt 9 and the second skirt 10 are set as described above, and the first skirt 9 and the second skirt 10 supported by the first sidewall 5 to the fourth sidewall 8 are set. Strength is secured. In particular, the strength of the first skirt 9 and the second skirt 10 is ensured by maintaining the above dimensional relationship in the continuous portion of the first sidewall 5 to the fourth sidewall 8 and the first skirt 9 and the second skirt 10. be able to. Thereby, the fall of the 1st skirt 9 and the 2nd skirt 10 and crack generation can be suppressed.

  The thickness Tw in the height direction of the first side wall 5 to the fourth side wall 8 is thinner than the diameter dimension R of the piston pin 20. Further, the center in the height direction of the first side wall 5 to the fourth side wall 8 is included in the virtual plane F. That is, the center in the height direction of the first side wall 5 to the fourth side wall 8 coincides with the height position of the center of the piston pin 20.

  The piston top part 2 is formed in a disk shape, and a ring groove 25 for mounting a compression ring and an oil ring (not shown) is formed on the outer periphery thereof. Note that the number of the ring grooves 25 is not limited to the two shown in the figure, and may be three, for example, which are generally employed.

  The piston 1 as described above has a so-called skeleton structure in which the piston top portion 2 and the first sidewall 5 to the fourth sidewall 8 are not connected. The first side wall 5 to the fourth side wall 8 have dimensions that can ensure the required rigidity, for example, the width, the thickness in the height direction, the R of the joint portion with the first pin boss 3 and the second pin boss 4. Designed considering the size of the shape. The piston 1 is thinned as much as possible within a range in which necessary rigidity can be ensured, and the weight is reduced. Since the piston top 2 and the first sidewall 5 to the fourth sidewall 8 are not connected, the force applied to the piston top 2 is not directly transmitted to the first sidewall 5 to the fourth sidewall 8. . This also leads to suppression of swinging of the piston 1.

  FIG. 6 is a perspective view of a conventional piston 101 shown as a comparative example. The piston 101 has a skirt 103 extending downward from the piston top 102. The skirt 103 is connected to a side wall 106 provided on the side of the first pin boss 104 and the second pin boss 105 disposed opposite to the back side of the piston top 102.

  The piston 1 of this embodiment achieves weight reduction by significantly reducing the area of the skirt and the side wall as compared with the piston 101 of the comparative example.

  The thickness Tw in the height direction of the first side wall 5 to the fourth side wall 8 is also made thinner than the diameter dimension R of the piston pin 20 as described above. Further, the thickness Ts in the height direction of the first skirt 9 and the second skirt 10 is set to be equal to or less than the thickness Tw in the height direction of the first sidewall 5 to the fourth sidewall 8. However, the first side wall 5 to the fourth side wall 8 are extended along the virtual plane F shown in the drawing. Further, the center in the height direction of the first side wall 5 to the fourth side wall 8 is included in the virtual plane F. That is, the center of the first sidewall 5 to the fourth sidewall 8 in the height direction coincides with the height position of the center of the piston pin.

  Oscillation during the reciprocating motion of the piston 1 occurs around the axis 21 of the piston pin 20. Therefore, by providing the first sidewall 5 to the fourth sidewall 8, the first skirt 9, and the second skirt 10 as described above, the swing of the piston 1 can be effectively suppressed. In particular, the swing of the piston 1 at the top and bottom dead center can be effectively suppressed, and the posture of the piston 1 can be maintained. If the posture of the piston 1 can be maintained, the thrust force is reduced, the surface pressure in the first skirt 9 and the second skirt 10 is reduced, and the skirt area can be reduced. The reduction in the skirt area enables further weight reduction. If the weight is further reduced, the thrust force can be further reduced. Thus, the maintenance of the posture of the piston 1 and the weight reduction bring a synergistic effect.

  Such a piston 1 not only reduces friction due to its weight reduction, but also reduces wear and noise, and also maintains a good posture of the piston 1 so that blow-by and oil consumption can be reduced. Hereinafter, effects obtained by the configuration of the piston 1 will be listed.

First, the weight reduction of the piston 1 reduces the inertial mass, resulting in a reduction in thrust force. When the thrust force is reduced, the friction during the reciprocating motion of the piston is reduced, and as a result, improvement in fuel consumption of the internal combustion engine is expected. If the fuel efficiency is improved, the amount of CO ₂ emission is also suppressed.

  The weight reduction of the piston 1 also contributes to a reduction in wear of the sliding portion with the bore of the internal combustion engine. Conventionally, a piston has been subjected to surface treatment on a sliding portion for the purpose of reducing friction. This surface treatment takes time for processing and may cause an increase in manufacturing cost. If it is the piston 1 of a present Example, reliability will improve by the abrasion reduction effect, and it can also make a surface treatment simple. By making the surface treatment simple, an increase in manufacturing cost can be suppressed.

  In addition, the inertial force of the piston 1 is reduced due to the weight reduction, and the vibration and noise can be reduced by reducing the thrust force resulting therefrom. As described above, the reduction of the thrust force reduces the skirt surface pressure and enables the skirt area to be reduced.

Further, the piston 1 of this embodiment can suppress the swinging phenomenon and maintain the posture during the reciprocating motion. As a result, oil consumption and blow-by can be reduced. As a result, it is possible to obtain an effect of suppressing the accumulation of sludge and deposits, it is possible to lengthen the interval of oil maintenance, and it is possible to make the oil maintenance-free. In addition, it is possible to use low-viscosity oil as the accumulation of sludge and deposits is suppressed.
Further, with the piston 1, the engine startability at the time of cold start is improved with the weight reduction of the piston. In the cold state, the aluminum piston 1 is contracted, and the gap with the bore becomes large, so that the aluminum piston 1 is easily oscillated. However, the piston 1 of this embodiment is very lightweight, has a low thrust force, and has a small friction, so that the piston 1 starts to move smoothly. For this reason, the piston 1 has good startability during cold start. As a result, the reduction of auxiliary equipment capacity can reduce harmful exhaust gas and cost.

  FIG. 7 is a graph showing the friction reduction effect when traveling in an urban area by comparing the piston 1 of this embodiment with the conventional piston 101 shown in FIG. As is apparent from the graph, the piston 1 of this example showed a significant reduction in friction compared to the conventional piston 101. In addition, it is thought that the effect of reducing the friction is a combination of the effect of reducing the weight, the effect of reducing the thrust force, and the effect of reducing the skirt area.

  FIG. 8 is a graph showing the oil consumption reduction effect in comparison with the piston 1 of this embodiment and the conventional piston 101 shown in FIG. As is apparent from the graph, the piston 1 of this example has a reduction in oil consumption compared to the conventional piston 101. The oil consumption increases as the internal combustion engine is operated under high speed and high load conditions. However, the oil consumption reduction effect of the piston 1 tends to become more prominent as the internal combustion engine operates under high speed and high load conditions.

Next, the piston 21 of Example 2 is demonstrated, referring FIG. 9, FIG. FIG. 9 is a diagram schematically illustrating the piston of Example 2 as viewed from the axial direction of the piston pin. FIG. 10 is a diagram schematically illustrating the piston of Example 2 as viewed from the thrust side. The piston 21 of the second embodiment is different from the piston 1 of the first embodiment in that the piston 21 of the second embodiment further includes vertical skirts 22 and 23 that extend vertically below the piston top 2. Is a point.
Since other configurations are the same as those of the first embodiment, common components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

  The upper and lower skirts 22 are provided on both sides of the first skirt 9 formed at a portion where the first sidewall 5 and the third sidewall 7 are joined. Further, the upper and lower skirts 23 are provided on both sides of the second skirt 10 formed at a portion where the second sidewall 6 and the fourth sidewall 8 are joined.

  The upper and lower skirts 22 and 23 are reinforcements that suppress deformation of the first skirt 9 and the second skirt 10. When the interval between the first skirt 9 and the second skirt 10 is narrowed, the piston easily swings. By thus providing the upper and lower skirts 22 and 23, the swing of the piston 21 is suppressed. If the swing of the piston 21 is suppressed, oil consumption can be suppressed and noise deterioration can also be suppressed.

  Further, since the upper and lower skirts 22 and 23 are provided, the skirt surface pressure is reduced, and a wear reduction effect is expected.

  Next, the piston 31 of Example 3 is demonstrated, referring FIG. 11, FIG. FIG. 11 is a diagram schematically illustrating the piston 31 when viewed from the pin hole, that is, the axial direction of the piston pin. FIG. 12 is a diagram schematically showing the piston 31 as a cross section taken along line BB in FIG. 11 when viewed from the axial direction of the piston pin.

The piston 31 of the third embodiment is different from the piston 1 of the first embodiment in that the piston 31 of the third embodiment further includes area enlarged portions 9a and 10a at the center of the first skirt 9 and the second skirt 10. is there.
Since other configurations are the same as those in the first embodiment, common components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

The area enlargement portion 9a is provided at the center of the first skirt 9 so as to protrude upward, that is, toward the piston top 2 side. Similarly, the area expanding portion 10a is provided at the center of the second skirt portion 10 so as to protrude upward, that is, toward the piston top 2 side.
By providing the area enlargement portions 9a and 10a, the area sliding with the bore increases, so that the skirt surface pressure can be reduced. Thereby, wear reduction with the bore in the piston 31 is achieved.

  In addition, the magnitude | size and position of the area expansion parts 9a and 10a can be suitably determined according to a request | requirement. In the piston 31, considering that the temperature on the side close to the piston top 2, that is, the side close to the combustion chamber of the internal combustion engine, is increased, the first skirt 9, Two skirts 10 are provided so as to protrude above.

Next, the piston of Example 4 will be described with reference to FIG. FIG. 13 is an explanatory diagram showing an enlarged view of the periphery of the second skirt 10 as a cross section. The fourth embodiment is different from the third embodiment in that a chamfered portion 10 a 1 is provided on the upper edge of the central portion of the area expanding portion 10. Although not shown in the drawing, a chamfered portion is also provided at the central upper edge of the area expanding portion 9.
Since other configurations are the same as those of the first embodiment, common components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

  The chamfered portion 10a1 forms an oil film with the bore of the internal combustion engine in the area expanding portion 10a to obtain a squeeze effect. Due to the squeeze effect, a non-sliding portion with the bore is formed, and wear reduction is achieved.

  In addition, in Example 4, although it is set as the structure which provided the chamfering part 10a in the area expansion part 10a (9a), in the piston 1 of Example 1 which does not have the area expansion parts 9a and 10a, the chamfering part was provided. It can also be configured. That is, a chamfered portion may be provided on the upper edges of the first skirt portion 9 and the second skirt portion 10 to obtain a squeeze effect.

Next, the piston 41 of Example 5 is demonstrated, referring FIG. 14, FIG. FIG. 14 is an explanatory view showing a cross section of the piston 41. FIG. 15 is an explanatory view showing an enlarged periphery of the second skirt having a cross section. The piston 41 of the fifth embodiment is different from the piston 1 of the first embodiment in that a ring groove 11 is provided in the first skirt 9 and the second skirt 10 of the piston 41 of the fifth embodiment. This is the point where a ring 12 that can come into contact is mounted.
Since other configurations are the same as those of the first embodiment, common components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

The ring 12 can maintain the posture of the piston 41 by contacting the bore of the internal combustion engine.
Under operating conditions where the thrust force is weak, such as the low rotation speed and low load range of the internal combustion engine, the ring 12 controls the oil consumption by the sealing force of the ring 13 by contacting the bore of the internal combustion engine, thereby reducing blow-by. Also contribute.

  Further, the ring 12 is pushed into the ring groove 11 in a high rotation and high load region of the internal combustion engine. As a result, the first skirt 9 and the second skirt 10 come into contact with the bore of the internal combustion engine, and the swing of the piston 41 is suppressed. Thereby, abrasion of a sliding part is suppressed.

  The specifications of the ring 12 can be variously changed according to the request. For example, a function required for a compression ring can be provided, or a function required for an oil ring can be provided.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the case of a piston having a pair of pin bosses at the lower portion of the head has been described. However, the piston may be a so-called single pin boss type piston integrally having a pin boss at the lower center of the head.

FIG. 1 is a perspective view of the piston of the first embodiment. FIG. 2 is a diagram schematically illustrating the piston of Example 1 as viewed from the axial direction of the piston pin. FIG. 3 is a diagram schematically illustrating the piston of Example 1 as viewed from the bottom surface side. FIG. 4 is a diagram schematically illustrating the piston of Example 1 as viewed from the thrust side. FIG. 5 is a view schematically showing the piston of Example 1 as a cross section taken along line AA in FIG. 4 as viewed from the axial direction of the piston pin. FIG. 6 is a perspective view of a piston of a comparative example. FIG. 7 is a graph showing the effect of reducing friction when traveling in an urban area. FIG. 8 is a graph showing the effect of reducing oil consumption. FIG. 9 is a diagram schematically illustrating the piston of Example 2 as viewed from the axial direction of the piston pin. FIG. 10 is a diagram schematically illustrating the piston of Example 2 as viewed from the thrust side. FIG. 11 is a diagram schematically illustrating the piston of Example 3 as viewed from the axial direction of the piston pin. FIG. 12 is a diagram schematically showing the piston of Example 3 as a cross section taken along the line BB in FIG. 11 as viewed from the axial direction of the piston pin. . FIG. 13 is an explanatory diagram showing an enlarged view of the periphery of the second skirt of Example 4 and a cross section thereof. FIG. 14 is an explanatory view showing a cross section of the piston of the fifth embodiment. FIG. 15 is an explanatory view showing an enlargement of the periphery of the second skirt of the piston shown in FIG.

Explanation of symbols

1, 21, 31, 41 ... piston 2 ... piston top 3 ... first pin boss 3a, 4a ... pin hole 4 ... second pin boss 5 ... first sidewall 6 ... second sidewall 7 ... third sidewall 8 ... first 4 side wall 9 ... 1st skirt 10 ... 2nd skirt 11 ... Ring groove 12 ... Ring

Claims (9)

A pin boss formed on the back side of the piston top and to which a piston pin is attached;
A sidewall provided on the side of the pin boss,
A skirt provided at the end of the sidewall,
The internal combustion engine piston according to claim 1, wherein the sidewall includes an axis of a piston pin and extends from the pin boss so as to extend along a virtual plane extending in a thrust direction and an anti-thrust direction.   The piston of the internal combustion engine according to claim 1, wherein a thickness of the sidewall in a height direction is thinner than a diameter dimension of the piston pin.   The piston of the internal combustion engine according to claim 1, wherein a center line in the height direction of the sidewall is included in the virtual plane. The pin boss includes a first pin boss and a second pin boss arranged to face each other on the back surface side of the piston top,
The sidewall includes a first sidewall extending in a thrust direction from the first pin boss, a second sidewall extending in an anti-thrust direction, and a third sidewall extending in a thrust direction from the second pin boss. A sidewall and a fourth sidewall extending in the anti-thrust direction,
The skirt includes a first skirt formed at a joint portion between the first sidewall and the third sidewall, and a second skirt formed at a joint portion between the second sidewall and the fourth sidewall. And a piston for an internal combustion engine according to claim 1.   2. A piston for an internal combustion engine according to claim 1, wherein the thickness of the skirt in the height direction is equal to or less than the thickness of the sidewall in the height direction.   2. A piston for an internal combustion engine according to claim 1, further comprising a vertical skirt extending in the vertical direction below the top of the piston.   The piston of the internal combustion engine according to claim 1, wherein the skirt has an area enlarged portion.   The piston of the internal combustion engine according to claim 1, wherein the skirt has a chamfered portion at an upper edge.   2. The piston of an internal combustion engine according to claim 1, wherein a ring groove is provided in the skirt, and a ring capable of contacting the cylinder bore is attached to the ring groove.

Images