Piston, internal combustion engine and vehicle

Abstract

A piston 3 comprises a piston head 5, a piston sleeve 6, and an oil flow path 23. The piston sleeve 6 is provided on an underside opposite the piston head 6, and a pin hole 22 is formed along an extension direction that intersects an upward and downward direction in the piston sleeve 6. The oil flow path 23 extends through the piston head 5 and the piston sleeve 6 and has an opening section 31 that is open towards the underside of the piston sleeve 6. A dimension of the opening section 31 along the extension direction of the pin hole 22 is larger than a dimension of the opening section 31 along a width direction that intersects both the upward and downward direction and the extension direction of the pin hole 22.

Description

TECHNICAL AREA

[0001] The present invention relates to a piston, an internal combustion engine and a vehicle. STATE OF THE ART

[0002] In an internal combustion engine, such as one installed in a vehicle, a piston moves up and down within the inner cavity of a cylinder, converting this reciprocating motion into a rotary motion of the crankshaft. A pin hole is formed in the piston skirt, and a piston pin is inserted into this hole. A connecting rod is connected to the piston via the connecting rod, which is positioned between the piston and the connecting rod.

[0003] Furthermore, an internal combustion engine is known in which an oil nozzle is attached to the cylinder and oil is sprayed from the nozzle towards the piston. In this type of internal combustion engine, the piston is cooled, for example, by the oil from the nozzle. Additionally, in this engine, an oil flow path is formed inside the piston, and the oil sprayed from the nozzle can flow into this path. The piston skirt, containing the oil flow path, has an inlet section or similar opening for the oil from the nozzle, opening towards the underside.

[0004] Regarding the piston of the internal combustion engine, it is necessary to reduce its stiffness under stress in the piston skirt, for example, to reduce frictional losses during reciprocating motion. For instance, in designs where the oil flow path is located inside the piston, it is necessary to reduce the stiffness of the piston skirt near the opening section of the oil flow path. SUMMARY

[0005] The problem to be solved by the invention is to provide a piston that can reduce the stiffness in a piston jacket in a structure in which an oil flow path is provided, as well as an internal combustion engine and a vehicle, each containing the piston.

[0006] According to one aspect of the present invention, a piston comprises a piston head, a piston jacket, and an oil flow path. The piston jacket is provided on an underside opposite the piston head, and a pin hole is formed along an expansion direction that intersects an up-and-down direction in the piston jacket. The oil flow path extends through the piston head and the piston jacket and has an opening section that is open to the underside of the piston jacket. A dimension of the opening section along the expansion direction of the piston hole is larger than a dimension of the opening section along a width direction that intersects both the up-and-down direction and the expansion direction of the pin hole.

[0007] According to the present invention, a piston can be provided which can reduce the stiffness in a piston jacket in a structure in which an oil flow path is formed, as well as an internal combustion engine and a vehicle, each containing the piston. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a cross-sectional view that schematically shows an example of a piston structure and its surroundings in an internal combustion engine according to one embodiment. Fig. Figure 2 is a schematic representation showing the piston of the example from Fig. 1 shows from the underside. Fig. Figure 3 is a cross-sectional view showing the piston of the example from Fig. 1 based on a different cross-section than in Fig. 1 schematically represents. Fig. Figure 4 is a schematic representation showing the structure of an opening section and its surroundings as seen from below, where the opening section is an inlet section of an oil flow path in the piston of the example from Fig. 1 forms. Fig. Figure 5 is a schematic diagram showing the structure of an opening section and its surroundings as seen from the bottom, wherein the opening section forms an inflow section of an oil flow path in a piston according to a modification. Fig. Figure 6 is a schematic representation showing the structure of an opening section and its surroundings as seen from below, where the opening section is an inlet section of an oil flow path in a piston according to a modification other than in Fig. 5 forms. Fig. Figure 7 is a cross-sectional view that schematically depicts a piston according to a different modification than in Figure 7. Fig. 5 and Fig. 6 shows. Fig. Figure 8 is a schematic representation showing an example of a vehicle structure in which the internal combustion engine is installed according to the embodiment. DETAILED DESCRIPTION

[0008] One embodiment is described below with reference to the attached drawings.

[0009] In an internal combustion engine installed in a vehicle or the like, one or more pistons and the same number of cylinders as the pistons are provided.

[0010] Furthermore, each of the one or more pistons moves back and forth within the interior of a corresponding cylinder. For example, a four-cylinder internal combustion engine has four pistons and four cylinders, and each of the four pistons moves back and forth within the interior of one of the four cylinders. In the internal combustion engine, each of the one or more pistons is connected to a crankshaft via a connecting rod. The reciprocating motion of the one or more pistons rotates the crankshaft. More precisely, the reciprocating motion of the piston is converted into the rotary motion of the crankshaft. In this embodiment, at least one piston in the internal combustion engine is provided with a structure described below. The structure described below is applicable to both diesel and gasoline engines.

[0011] Fig. Figure 1 is a cross-sectional view that schematically shows an example of the structure of a piston 3 and its surroundings in an internal combustion engine 1 according to the embodiment. As in Fig. As shown in Figure 1, the internal combustion engine 1 comprises a cylinder 2 and the piston 3. In the internal combustion engine 1 and the piston 3, an up and down direction (direction indicated by arrow Y1 and arrow Y2) and a front and back direction (direction indicated by arrow Z), which intersects the up and down direction (perpendicular or substantially perpendicular to it), are defined. Fig. Figure 1 shows a cross-section along the upward and downward directions and the forward and reverse directions. In the internal combustion engine 1 and the piston 3, one side of the upward and downward direction is referred to as the top (side of arrow Y1), and the side opposite the top of the upward and downward direction is referred to as the bottom (side of arrow Y2).

[0012] Cylinder 2 is cylindrical, with its central axis extending both upwards and downwards, and piston 3 is located within an internal cavity of cylinder 2. Piston 3 moves back and forth within this internal cavity in an upward and downward direction. This upward and downward movement is therefore also referred to as the reciprocating motion of piston 3. In the internal combustion engine 1, an intake port (not shown) and an exhaust port (not shown) are located on the upper surface relative to piston 3. Furthermore, the space between the intake port and the exhaust port, respectively, and piston 3 forms a combustion chamber. Additionally, a crankshaft (not shown) is located on the lower surface relative to piston 3 in the internal combustion engine 1.

[0013] In internal combustion engine 1, for example, a cycle is repeatedly performed, in which four steps—namely an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke—form a cycle. During the intake stroke of internal combustion engine 1, gas is introduced from the intake port into the combustion chamber of the inner cavity of cylinder 2, and the piston 3 moves upwards towards the bottom until it reaches bottom dead center. Then, during the compression stroke, the piston 3 moves upwards from bottom dead center towards the top until it reaches top dead center. The top dead center reached by the piston 3 during the compression stroke is also called compression top dead center.In the cyclic operation of the diesel engine, the combustion chamber temperature rises to a high temperature during the compression stroke, and the gas in the combustion chamber is ignited by the jet of diesel fuel at any point during top dead center (TDC) and in the period immediately preceding TDC, thus combusting the gas in the combustion chamber. Conversely, in the cyclic operation of the gasoline engine, gasoline is introduced into the combustion chamber along with gas during the intake stroke, and the gas in the combustion chamber is ignited by a spark plug or similar device at any point between TDC and the period immediately preceding TDC, thus combusting the gas in the combustion chamber. During the expansion stroke, the piston 3 moves from TDC to bottom dead center (BDC).Then, during the exhaust stroke, piston 3 moves from bottom dead center to top dead center towards the top, and the gas is expelled from the exhaust port into the interior of cylinder 2. Due to the cyclic operation of the internal combustion engine 1 described above, piston 3 moves back and forth between top dead center and bottom dead center twice, completing four strokes in one cycle.

[0014] The piston 3 comprises a piston head 5 and a piston sleeve 6. The piston sleeve 6 is located on the underside relative to the piston head 5. In the example of Fig. 1. The piston sleeve 6 is connected to the piston head 5 from below. Furthermore, in the piston 3, an end face (upper end face) 7 is formed on the top side by the piston head 5 and an end face (lower end face) 8 is formed on the bottom side by the piston sleeve 6. In addition, in the example of Fig. 1. The piston head 5 is formed in a columnar shape with an outer circumferential section 11, and the piston jacket 6 is formed in a cylindrical shape with an outer circumferential section 12 and an inner circumferential section 13. During the reciprocating movement of the piston 3, the outer circumferential section 11 of the piston head 5 and the outer circumferential section 12 of the piston jacket 6 slide relative to the inner circumferential section of the cylinder 2 in an upward and downward direction. In the piston 3 of the example of Fig. 1. A space 15 is formed on the inner circumferential side of the piston shell 6, and the space 15 is covered by the piston shell 6 over the entire circumference of the piston 3. Furthermore, the space 15 opens towards the underside, and a bottom surface 16 of the piston head 5 borders the space 15 from the top.

[0015] In the outer area 11 of the piston head 5, ring grooves 17 are formed that are recessed towards the inside, as in the example of Fig. 1. Three annular grooves 17 are formed. Each of the annular grooves 17 extends along the circumferential direction of the piston 3 and is formed circumferentially over its entire circumference. Furthermore, in the structure in which several annular grooves 17 are formed, the annular grooves 17 are spaced apart from each other in the upward and downward directions. A piston ring (not shown) is attached to each of the annular grooves 17. It should be noted that the number of annular grooves 17 formed in the piston head 5 is adjusted to a suitable number according to the internal combustion engine 1 in which the piston 3 is used.

[0016] Fig. Figure 2 is a schematic representation showing piston 3 from the example. Fig. 1 shows a view from below. A cross-section S1 in Fig. 2 is in Fig. 1 shown. As in Fig. 1 and Fig. As shown in Figure 2, the piston sleeve 6 comprises a pair of pin projections 21. The paired pin insert sections 21 are arranged longitudinally spaced apart from each other and face each other with the gap 15 between them. Furthermore, the paired pin insert sections 21 are spaced apart circumferentially by half a circumference or substantially half a circumference of the piston 3. A pin hole 22 is formed in each of the two pin insert sections 21, and each of the two pin holes 22 penetrates the piston sleeve 6 from the outer circumferential region 12 to the inner circumferential region 13. The pin hole 22 extends longitudinally in each of the pin insert sections 21. Additionally, a central axis C of each of the pin holes 22 extends along the front and rear directions.Thus, the front and back directions are also referred to as the expansion direction of the bolt hole 22, the penetration direction of the bolt hole 22 and the axial direction of the bolt hole 22.

[0017] In the internal combustion engine 1, a piston pin (not shown) passes through each of the pin holes 22, and the piston pin is secured in the pin holes 22 of the piston skirt 6. Additionally, the piston 3 is connected to a connecting rod (not shown) via the piston pin. Thus, the piston pin 3 is coupled to the crankshaft via the piston pin and the connecting rod between them. Furthermore, during the cyclic operation of the internal combustion engine 1, the piston 3 pivots around the piston pin parallel to the reciprocating motion described above. This pivoting motion of the piston around the piston pin is also referred to as oscillation. The pivot axis of the piston during this motion is coaxial or substantially coaxial with the central axis of the piston pin and coaxial or substantially coaxial with the central axis C of each of the pin holes 22.

[0018] Furthermore, a lateral direction (indicated by the arrow X) is defined in piston 3, which intersects (is perpendicular or substantially perpendicular to) both the up-and-down direction (reciprocating direction) and the forward-and-backward direction (the expansion direction of the bolt holes 22). In the internal combustion engine 1, piston 3 is inclined with respect to the up-and-down direction (the central axis of cylinder 2) due to the oscillatory motion described above from a neutral state. In the neutral state, one side of the lateral direction of piston 3 coincides with or substantially coincides with a thrust side, and one side opposite the thrust side in the lateral direction of piston 3 coincides with or substantially coincides with an anti-thrust side. Therefore, the lateral direction of piston 3 is also referred to as the thrust-anti-thrust direction. It should be noted that Fig. 1 shows a cross-section perpendicular or substantially perpendicular to the width direction of the piston 3.

[0019] In the internal combustion engine 1, lateral pressure occurs between piston 3 and cylinder 2 because piston 3 is tilted in the up-and-down direction by its oscillating motion. At top dead center of compression and in the time immediately before and after top dead center of compression, which includes the point of transition from the compression stroke to the expansion stroke, a portion on the upper side pivots towards the thrust side relative to the pin holes 22, relative to its neutral position. Furthermore, immediately after top dead center of compression, maximum lateral pressure occurs on the thrust side relative to the central axis of cylinder 2.

[0020] As in Fig. 1 and Fig. As shown in Figure 2, an oil flow path 23 extends through the piston head 5 and the piston skirt 6 in the piston 3. In the internal combustion engine 1, an oil nozzle 25, which can spray oil, is attached to the cylinder 2. The oil nozzle 25 includes a nozzle opening 27 and sprays oil from the nozzle opening 27. The oil nozzle 25 is located in the inner cavity of the cylinder 2 on the underside with respect to the piston 3. As the piston 3 moves towards bottom dead center due to the reciprocating motion described above, the piston 3 approaches the oil nozzle 25. Conversely, as the piston 3 moves towards top dead center, it moves away from the oil nozzle 25. Fig. Figure 1 shows a state in which piston 3 is at or near bottom dead center.

[0021] Inside cylinder 2, the oil nozzle 25 sprays oil upwards, splashing it onto the reciprocating piston 3. The oil from the nozzle 25 cools the piston 3 and improves its lubrication. The amount of oil sprayed from the nozzle 25 varies according to the pressure inside cylinder 2. For example, the amount of oil sprayed from the nozzle 25 increases during and immediately after the combustion of the gas in the combustion chamber at top dead center (TDC), compared to other times. When the piston 3 is at or near TDC, i.e., when the piston 3 is approaching the nozzle 25, the nozzle 25 can cause the ejected oil to flow into the oil flow path 23 of the piston 3.It should be noted that in the state in which the piston 3 is at a certain distance from the oil nozzle 25 to the top of the, the oil ejected from the oil nozzle 25 does not flow into the oil flow path 23.

[0022] Fig. Figure 3 is a cross-sectional view showing piston 3 of the example from Fig. 1 based on a different cross-section than in Fig. 1 schematically represents. Fig. Figure 3 shows a cross-section that runs perpendicular or substantially perpendicular to the width direction of the piston 3 and extends from the cross-section Fig. 1 is offset in the lateral direction of the piston 3. In particular, in Fig. 3 a cross-section S2 of Fig. 2 shown. As in Fig. 1 and Fig. As shown in Figure 3, the oil flow path 23 includes a cooling chamber 26 formed inside the piston head 5. Within the piston head 5, the cooling chamber 26 extends in the upward and downward directions between the end face 7 on the top of the piston 3 and the bottom 16 of the piston head 5. Furthermore, the cooling chamber 26 is formed on the inside of the piston 3 with respect to the ring grooves 17. In the example of Fig. 1 and Fig. 3 The cooling chamber 26 extends along the circumferential direction of the piston 3. Furthermore, the cooling chamber 26 is formed over the entire circumference in the circumferential direction and extends in a ring-shaped manner in the circumferential direction.

[0023] Furthermore, the oil flow path includes 23, as described in the Fig. 1 to Fig. Figure 3 shows opening sections 31 and 35 facing outwards. Each of the opening sections 31 and 35 opens towards the underside in the piston casing wall 6. In the example of Fig. 1 to Fig. Each of the opening sections 31 and 35 is located on the top side with respect to the end face 8 on the underside of the piston 3 and opens towards the chamber 15. Furthermore, the oil flow path 23 includes connecting paths 32 and 36. Connecting path 32 establishes a connection between opening section 31 and cooling chamber 26 and extends from opening section 31 towards cooling chamber 26 to the top side. Additionally, connecting channel 36 establishes a connection between opening section 35 and cooling chamber 26 and extends from opening section 35 towards cooling chamber 26 to the top side. It should be noted that Fig. Figure 1 shows a cross-section through the opening section 31 and the connecting channel 32 and Fig. Figure 3 shows a cross-section through the opening section 35 and the connecting channel 36.

[0024] In the examples of Fig. 1 to Fig. In the following example, the opening section 35 and the communication path 36 are arranged at a distance from the opening section 31 and the communication path 32 both in the extension direction of the bolt holes 22 and in the width direction of the piston 3. Furthermore, the opening section 35 and the communication path 36 are arranged such that they are spaced from the opening section 31 and the communication path 32 by half a circumference or substantially half a circumference in the circumferential direction of the piston 3. However, in one example, a configuration can be chosen such that the opening section 35 and the communication path 36 are spaced at a distance from the opening section 31 and the communication path 32 with respect to the extension direction of the bolt holes 22, but are not, or not substantially, offset from the opening section 31 and the communication path 32 with respect to the width direction of the piston 3.Furthermore, in an example, such a configuration can be assumed that the opening section 35 and the connecting channel 36 are arranged at a distance from the opening section 31 and the connecting channel 32 with respect to the width direction of the piston 3, but are not or substantially not offset from the opening section 31 and the connecting channel 32 with respect to the expansion direction of the bolt holes 22.

[0025] As in Fig. As shown in Figure 1, when the piston 3 is at or near bottom dead center, the oil nozzle 25 is inserted into the chamber 15 from below, and the opening sections 31 are located opposite the opening section 31 from below in the chamber 15. Furthermore, when the piston 3 is at or near bottom dead center, the oil nozzle 25 sprays oil towards the opening section 31, and the oil from the oil nozzle 25 flows through the opening section 31 into the oil flow path 23. Thus, the opening section 31 forms an inlet section through which the oil from the oil nozzle 25 flows into the oil flow path 23. The oil flowing in from the opening section 31 flows through the connecting path 32 towards the cooling chamber 26.

[0026] Furthermore, when the oil flows from opening section 31 into oil flow path 23, the oil that has flowed through cooling chamber 26 flows through connecting channel 36 towards opening section 35. The oil then flows out of oil flow path 23 through opening section 35. Thus, opening section 35 forms an outlet section through which the oil flows out of oil flow path 23. Since the oil flows in oil flow path 23 as described above, opening section 31 is also referred to as the inlet opening, and connecting channel 32 is also referred to as the inlet-side connecting channel. Additionally, opening section 35 is also referred to as the outlet opening, and connecting channel 36 is also referred to as the outlet-side connecting channel.It should be noted that if the oil does not flow from the opening section 31 into the oil flow path 23, the oil flows from the cooling chamber 26 through the connecting channel 32 towards the opening section 31. In this case, the oil flows out of the oil flow path 23 through the opening section 31.

[0027] Fig. Figure 4 is a schematic diagram showing the structure of the opening section 31 and its surroundings as seen from below, where the opening section 31 is the inlet section of the oil flow path 23 in the piston 3 of the example from Fig. 1 forms. Fig. Figure 4 shows, on an enlarged scale, the part of opening section 31 and its surroundings in Fig. 2. In the example of Fig. 2 and Fig. 4 The opening section (inlet opening) 31 is formed in an elliptical shape, the major axis of which extends along the extension direction of the bolt holes 22 and the minor axis of which extends along the width direction of the piston 3. Thus, a dimension L1 of the opening section 31 along the extension direction of the bolt holes 22 is larger than a dimension L2 of the opening section 31 along the width direction of the piston 3.

[0028] Furthermore, an opening edge surrounding the opening section 31 comprises parts 41 and 42, which adjoin the opening section 31 in the width direction, and parts 43 and 44, which adjoin the opening section 31 in the extension direction (front and rear direction) of the bolt holes 22. Part 41 adjoins the opening section 31 on one side in the width direction, and part 42 adjoins the opening section 31 on a side opposite part 41 in the width direction. Furthermore, parts 41 and 42 are opposite each other, with the opening section 31 lying between them. On the other hand, part 43 adjoins the opening section 31 on one side in the front and rear direction, and part 44 adjoins the opening section 31 on a side opposite part 43 in the front and rear direction. Furthermore, parts 43 and 44 are opposite each other, with the opening section 31 lying between them. In the example of Fig. 2 and Fig. Parts 41 to 44 are formed because the opening section 31 is shaped in the elliptical shape described above, in curved shapes, and in arc-shaped forms that project towards a side pointing away from a central axis A1 of the opening section 31. Furthermore, the radius of curvature of each of parts 41 and 42 is larger than the radius of curvature of each of parts 43 and 44.

[0029] Furthermore, the examples of Fig. 1 to Fig. 4. The cross-sectional shape of the connecting channel 32 is circular or substantially circular. Furthermore, the diameter of the circular shape representing the cross-sectional shape of the connecting channel 32 is small compared to the major axis of the elliptical shape of the opening section 31. In the oil channel 23, a section 33 with a varying cross-sectional shape is formed between the opening section 31 and the connecting channel 32. In the section 33 with the varying cross-sectional shape, the cross-sectional shape of the oil channel 23 gradually varies between the elliptical shape of the opening section 31 and the circular shape representing the cross-sectional shape of the connecting channel 32. Moreover, in the example of Fig. 1 to Fig. 4. The central axis A1 of the opening section 31 is coaxial or substantially coaxial with a central axis A2 of the connecting path 32. Thus, the opening section 31 is designed to be coaxial or substantially coaxial with the connecting path 32. It should be noted that in the example of Fig. 1 to Fig. 4. The opening section 35, which forms the outlet section, is designed in a circular or substantially circular shape. Furthermore, the cross-sectional shape of the connecting channel 36 is congruent or substantially congruent circular or substantially circular with the opening section 35. In addition, the opening section 35 is designed to be coaxial or substantially coaxial with the connecting channel 36.

[0030] As described above, in this embodiment and similar versions, the opening section 31 of the oil flow path 23 opens towards the underside of the piston skirt 6, and the dimension L1 of the opening section 31 along the extension direction of the pin holes 22 is larger than the dimension L2 of the opening section 31 along the width direction of the piston 3. This structure increases the area near the opening section 31 where the thickness of the piston skirt 6 is small. During the cyclic operation of the internal combustion engine 1, a load F acts on the piston 3 from the width direction. The load F comprises a lateral pressure between the piston 3 and the cylinder 2 as well as a rotational force due to the oscillating motion. In this embodiment and similar versions, because the area where the thickness of the piston skirt 6 is small is increased as described above, the stiffness towards the load F in the piston skirt 6 is reduced (relaxed).Particularly near the opening section 31, the stiffness of the piston jacket 6 is reduced. This reduction in stiffness of the piston jacket 6 reduces frictional losses during the reciprocating movement of the piston 3.

[0031] Furthermore, in one embodiment, the radius of curvature of each of the parts 41 and 42 adjacent to the opening section 31 in the lateral direction of the piston 3 is larger than the radius of curvature of each of the parts 43 and 44 adjacent to the opening section 31 in the expansive direction of the bolt holes 22. By increasing the radius of curvature of each of the parts 41 and 42, the reaction force of the piston jacket 6 against the load F is reduced, even when the piston jacket 6 absorbs the load F in the lateral direction. Since the reaction force of the piston jacket 6 against the load F is reduced, the stiffness towards the load F in the piston jacket 6 is further reduced.

[0032] Additionally, in the example of Fig. 1 to Fig. 4 The opening section 31 of the oil flow path 23 is formed in an elliptical shape, the principal axis of which extends along the direction of extension of the bolt holes 22. Thus, in the opening section 31, the structure in which dimension L1 is larger than dimension L2 is appropriately achieved, and in the opening edge of the opening section 31, the structure in which the radius of curvature of each of parts 41 and 42 is larger than the radius of curvature of each of parts 43 and 44 is appropriately achieved.

[0033] In one embodiment, the opening section 31, which serves as an inlet opening, is additionally designed to be coaxial with the connecting path 32. This structure makes it possible to prevent the oil that has flowed from the opening section 31 into the oil flow path 23 from flowing back due to an impact on a wall surface or the like. This allows the oil flowing in from the opening section 31 to easily reach the cooling chamber 26, thus improving oil collection efficiency.

[0034] Fig. Figure 5 is a schematic diagram showing the structure of the opening section 31 and its surroundings as seen from below, where the opening section 31 forms the inlet section of the oil flow path 23 in the piston 3 according to one modification. Also in the modification of Fig. In section 5, the dimension L1 of the opening section 31 along the extension direction of the bolt holes 22 is larger than the dimension L2 of the opening section 31 along the width direction of the piston 3. Additionally, the opening edge of the opening section 31 comprises parts 41 and 42, which adjoin the opening section 31 in the width direction, and parts 43 and 44, which adjoin the opening section 31 in the extension direction (front-to-back direction) of the bolt holes 22. Each of the parts 41 to 44 is formed in an arcuate (curved) shape that projects to a side facing away from the central axis A1 of the opening section 31. In the present modification, however, the opening section 31 is not elliptically shaped.Furthermore, in the opening edge of the opening section 31 a straight section is formed between section 41 and each of sections 43 and 44, and a straight section is formed between section 42 and each of sections 43 and 44.

[0035] In the present modification, as in the embodiment described above and similar embodiments, the radius of curvature of each of the parts 41 and 42 adjacent to the opening section 31 in the lateral direction is larger than the radius of curvature of each of the parts 43 and 44 adjacent to the opening section 31 in the extensible direction (front-to-back direction) of the bolt holes 22. Due to the structure described above, the area in which the thickness of the piston jacket 6 is small is also increased near the opening section 31 in the present modification, and the reaction force of the piston jacket 6 against the load F in the lateral direction is reduced. Accordingly, in the present modification, as in the embodiment described above and similar embodiments, the stiffness of the piston jacket 6 is reduced (relaxed).

[0036] Fig. Figure 6 is a schematic diagram showing the structure of the opening section 31 and its surroundings as seen from below, wherein the opening section 31 forms the inflow section of the oil flow path 23 in the piston 3 according to a modification that differs from the modification in Fig. 5 differs. In the modification in Fig. In Figure 6, the opening section 31 is formed in a rectangular shape with rounded corners. Furthermore, the opening edge of the opening section 31 comprises a pair of longitudinal edges 45 and 46, which are the parts adjacent to the opening section 31 in the width direction, and a pair of cross-sectional edges 47 and 48, which are the parts adjacent to the opening section 31 in the extension direction (front-to-back direction) of the bolt holes 22. In the present modification, in the rounded rectangular shape of the opening section 31, the longitudinal side edges 45 and 46 extend along the extension direction of the bolt holes 22, and the short side edges 47 and 48 extend along the width direction of the piston 3. Accordingly, in the opening section 31, the longitudinal side of the rectangular shape with rounded corners extends along the front and back of the piston 3 (the extension direction of the bolt holes 22).

[0037] Due to this structure, in the present modification, the dimension L1 of the opening section 31 along the expansion direction of the bolt holes 22 is also larger than the dimension L2 of the opening section 31 along the width direction of the piston 3. Thus, in the present modification, the area where the thickness of the piston jacket 6 is small is also increased near the opening section 31. Accordingly, in the present modification, as in the embodiment described above and the like, the stiffness of the piston jacket 6 is reduced.

[0038] It should be noted that in this embodiment and the like, the shape of the opening section 31, which forms the inlet section, is not particularly restricted if the structure is adopted in which the dimension L1 of the opening section 31 along the expansion direction of the bolt holes 22 is larger than the dimension L2 of the opening section 31 along the width direction of the piston 3. For example, if dimension L1 is larger than dimension L2, the opening section 31 can have a rounded polygonal shape, such as a rounded triangular shape, instead of a rounded rectangular shape. By using a structure in which dimension L1 is larger than dimension L2, the area in which the thickness of the piston jacket 6 is small is increased near the opening section 31, and the stiffness towards the load F in the piston jacket 6 is reduced.Furthermore, in this embodiment and the like, it is advantageous that in the opening edge of the opening section 31, the radius of curvature of the part (e.g., 41, 42) that borders the opening section 31 in the lateral direction is larger than the radius of curvature of the part (e.g., 43, 44) that is adjacent to the opening section 31 in the extension direction of the bolt holes 22. This structure reduces the reaction force of the piston jacket 6 against the load F in the lateral direction, and further reduces the stiffness of the piston jacket 6 towards the load F.

[0039] Fig. Figure 7 is a cross-sectional view that schematically depicts a piston 3 according to a different modification than in Figure 3. Fig. 5 and Fig. 6 shows. Fig. Figure 7 shows a cross-section that runs perpendicular or substantially perpendicular to the width direction of the piston 3 and passes through the opening section 31 and the connecting channel 32. Also in the modification of Fig. 7. The dimension L1 of the opening section 31 along the expansion direction of the bolt holes 22 is larger than the dimension L2 of the opening section 31 along the width direction of the piston 3. Furthermore, the opening section 31, which forms the inlet section, is designed in a suitable shape where dimension L1 is larger than dimension L2, and in one example, the opening section 31 is designed in an elliptical shape, as in the example of Fig. 1.

[0040] In the present modification, the central axis A2 of the connecting path 32 is inclined with respect to the upward and downward directions and the central axis A1 of the opening section 31. Thus, the central axis A1 of the opening section 31 is not coaxial with the central axis A2 of the connecting path 32, and the opening section 31 is not designed to be coaxial with the connecting path 32. Since, in the present modification, dimension L1 is larger than dimension L2, the area where the thickness of the piston jacket 6 is small is increased near the opening section 31, and the stiffness towards the load F in the piston jacket 6 is reduced.

[0041] In the embodiment and the like, if the opening section 31 is configured such that dimension L1 is larger than dimension L2, the opening section 31 may not be designed coaxially to the communication path 32, as in the modification according to Fig. 7. In this embodiment and the like, however, it is preferable for the opening section 31 to be designed coaxially or substantially coaxially with the communication path 32. By using this structure, the oil flowing in from the opening section 31 can easily reach the cooling chamber 26, thereby improving the oil collection efficiency.

[0042] Additionally, in the embodiment described above and similar embodiments, the cross-sectional shape of the connecting channel 32 differs from the shape of the opening section 31. In one modification, however, the cross-sectional shape of the connecting channel 32 can be congruent or substantially congruent with the shape of the opening section 31. In an example, such as the example of Fig. 1 to Fig. 4 or the like, the opening section 31 is formed in an elliptical shape, the principal axis of which extends along the direction of expansion of the bolt holes 22. Furthermore, the cross-sectional shape of the connecting path 32 is an elliptical shape congruent or substantially congruent with the opening section 31.

[0043] Additionally, in the embodiment described above and the like, the opening section 35, which forms the outlet section, opens in the piston jacket 6, but the embodiment and the like are not limited to this. In one modification, the opening section 35 opens to the underside in the lower surface 16 of the piston head 5. In this case as well, the opening section 31 forming the opening section is designed in a shape similar to one of the shapes of the embodiment described above and the like. Thus, in the present modification, too, the dimension L1 of the opening section 31 along the direction of expansion of the bolt holes 22 is larger than the dimension L2 of the opening section 31 along the width direction of the piston 3.

[0044] In one modification, the opening section 35, which serves as an exhaust port, opens towards the underside of the piston jacket wall 6. Furthermore, instead of forming the opening section 31, which serves as an inlet port, in one of the forms described above, or in addition to forming the opening section 31 in one of the forms described above, the opening section 35 is formed in a form described below. In particular, in the present modification, the dimension of the opening section 35 along the extension direction of the bolt holes 22 is larger than the dimension of the opening section 35 along the width direction of the piston 3. This structure increases the area in which the thickness of the piston jacket 6 is small near the opening section 35, which forms the exhaust section, and reduces the stiffness under the load F in the piston jacket 6.

[0045] In addition, it is advantageous in the present modification that, at the opening edge of the opening section 35, the radius of curvature of the part adjacent to the opening section 35 in the lateral direction (as viewed from the piston 3) is larger than the radius of curvature of the part adjacent to the opening section 35 in the extension direction of the bolt holes 22 (as viewed from the opening section 35). In this case, the opening section 35 is, for example, formed in an elliptical shape whose principal axis extends along the extension direction of the bolt holes 22. This structure reduces the reaction force of the piston jacket 6 against the load F in the lateral direction, and further reduces the stiffness of the piston jacket 6 towards the load F.

[0046] Furthermore, the internal combustion engine 1 with the piston 3 described above is, for example, installed in a vehicle. Fig. Figure 8 is a schematic diagram showing an example of the structure of a vehicle 100 in which the internal combustion engine 1 is installed according to the embodiment. As in Fig. As shown in Figure 8, the vehicle 100 comprises the internal combustion engine 1, a transmission 101, and at least one wheel 102. In the example of Fig. Figure 8 shows a vehicle with four wheels 102, but the number of wheels 102 is not specifically limited. In the vehicle 100, the driving force is transmitted via the transmission 101 to one or more of the at least one wheels 102 by the internal combustion engine 1, which performs the cyclic operation. The vehicle 100 can move by transmitting the driving force to one or more of the at least one wheels 102. In a case where four wheels 102 are provided, as in the example of Fig.As shown in Figure 8, either a two-wheel drive, in which the driving force is transferred to two wheels 102, or an all-wheel drive, in which the driving force is transferred to the four wheels 102, can be used.

[0047] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the attached claims and their equivalents. Reference symbol list 1 Internal combustion engine 2 cylinders 3 pistons 5 Piston head 6 piston jacket 7 Upper end face of the piston 8 Lower end face of the piston 11 Outer circumferential section of the piston head 12 Outer circumferential section of the piston jacket 13 Inner circumferential section of the piston jacket 15 Space in the piston casing 16 Underside of the piston head 17 ring grooves in the piston head 21 bolt projections 22 bolt holes 23 Oil flow path 25 Oil nozzle 26 cold storage rooms 27 Oil nozzle opening 31 Opening section / Inlet opening 32 Connection channel / Inlet-side connection channel 33 Section with varying cross-sectional shape 35 Opening section / Outlet opening 36 Connection channel / Outlet-side connection channel 41-44 parts of the opening edge of opening section 31 45-48 edges of the rectangular opening section 100 vehicles 101 Gearbox 102 wheels

Claims

[1] Piston (3), comprising: a piston head (5); a piston jacket (6) provided on an underside with respect to the piston head (5) and in which a bolt hole (22) is formed along an expansion direction that intersects an upward and downward direction; and an oil flow path (23) extending through the piston head (5) and the piston jacket (6) and having an opening section (31) opening towards the underside in the piston jacket (6), wherein a dimension of the opening section (31) along the extension direction of the bolt hole (22) is larger than a dimension of the opening section along a width direction that intersects both the up and down direction and the extension direction of the bolt hole (2). [2] Piston (3) according to claim 1, wherein in an opening edge of the opening section (31) of the oil flow path (23) a radius of curvature of a part which borders the opening section in terms of width is larger than a radius of curvature of a part which borders the opening section (31) in terms of the course of the bolt hole (22). [3] Piston (3) according to claim 2, wherein the opening section (31) of the oil flow path (23) is formed in an elliptical shape, the main axis direction of which extends along the expansion direction of the bolt hole (22). [4] Piston (3) according to claim 1, wherein the oil flow path (23) comprises a cooling chamber formed in an interior of the piston head (5) and (26) a connecting channel (32, 36) which establishes a connection between the opening section (31) and the cooling chamber (26), and the opening section (31) is formed coaxially with the connecting channel (32, 36). [5] Piston (3) according to claim 1, wherein the opening section (31) forms an inlet section through which oil flows from an oil nozzle (25) into the oil flow path (23). [6] Internal combustion engine (1), comprising: the piston (3) according to any one of claims 1 to 5; and an oil nozzle (25) which can expel oil and cause the expelled oil to flow into the oil flow path (23) of the piston (3). [7] Vehicle (100) comprising the internal combustion engine (1) according to claim 6.

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