Cylinders, internal combustion engines, and vehicles

Abstract

To reduce friction between the piston and the inner wall surface. [Solution] The cylinder according to the embodiment includes an inner wall surface that forms an internal space in which a piston is arranged. The inner wall surface has a first region on the thrust side, a second region on the anti-thrust side, a third region on the front side, and a fourth region on the rear side. The frictional characteristics of the inner wall surface in at least the first or second region are different from the frictional characteristics in at least the third or fourth region.

Description

Technical Field

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[0001] The present disclosure relates to a cylinder, an internal combustion engine, and a vehicle.

Background Art

[0002] The piston of an internal combustion engine mounted on a vehicle or the like reciprocates along the vertical direction of the cylinder in the internal space formed by the inner wall surface of the cylinder. On the inner wall surface of the cylinder, a surface pattern is formed for improving lubricity (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an internal combustion engine, the piston receives a thrust force or a counter-thrust force in parallel with the reciprocating motion of the piston, so the piston tilts to the thrust side or the counter-thrust side, but does not rotate to the front side and the rear side. Therefore, on the inner wall surface, the contact state between the piston and the inner wall surface is different depending on the position in the circumferential direction of the cylinder. Therefore, in an internal combustion engine, it is required to form an inner wall surface according to the contact state and reduce the friction between the piston and the inner wall surface.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to reduce the friction between the piston and the inner wall surface. ​​​​​The cylinder according to this embodiment includes an inner wall surface that forms an internal space in which a piston is arranged. The inner wall surface has a first region on the thrust side, a second region on the anti-thrust side, a third region on the front side, and a fourth region on the rear side. The frictional characteristics of the inner wall surface in at least the first or second region are different from the frictional characteristics in at least the third or fourth region. [Effects of the Invention]

[0007] According to this disclosure, friction between the piston and the inner wall surface can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of the configuration of a vehicle according to this embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of the configuration of the internal combustion engine 1 when the piston according to the embodiment is in the neutral position. [Figure 3] Figure 3 is a schematic diagram showing an example of the configuration of the internal combustion engine 1 when the piston according to the embodiment is tilted relative to the neutral position. [Figure 4] Figure 4 is a schematic diagram showing the internal space of the cylinder according to the embodiment, and its vicinity, as viewed from the intake valve side. [Figure 5] Figure 5 is a schematic diagram showing a part of the configuration of the inner wall surface of the cylinder according to the embodiment. [Modes for carrying out the invention]

[0009] Figure 1 is a schematic diagram showing an example of the configuration of a vehicle 100 according to an embodiment. As shown in Figure 1, the vehicle 100 comprises an internal combustion engine 1, a transmission 110, and at least one wheel 40. When the internal combustion engine 1 is driven, the driving force is transmitted to at least one wheel 40 via the transmission 110.

[0010] Figure 2 is a schematic diagram showing an example of the configuration of an internal combustion engine 1 when the piston 3 of the embodiment is in the neutral position. The neutral position will be described later. As shown in Figure 2, the internal combustion engine 1 comprises an intake valve (not shown), a cylinder 2, a piston 3, a piston pin 4, a crank arm (not shown), and a crankshaft (not shown). The internal combustion engine 1 of the embodiment is, for example, a four-stroke engine that constitutes one cycle consisting of four processes: intake, compression, expansion, and exhaust. The internal combustion engine 1 of the embodiment is, for example, a diesel engine. The piston 3 is equipped with a plurality of piston rings. The plurality of piston rings of the embodiment include a top ring 7, a second ring 8, and an oil ring 9.

[0011] Cylinder 2 extends along the central axis A1 and is formed in a cylindrical or other tubular shape. Cylinder 2 has a tubular inner wall surface 11. The inner wall surface 11 forms an internal space in cylinder 2. Hereafter, the direction around the central axis A1 of cylinder 2 will be referred to as the circumferential direction.

[0012] The piston 3 is positioned in the internal space formed by the inner wall surface 11 and is connected to the crank arm via a piston pin 4 or the like, which extends in a direction perpendicular or nearly perpendicular to the central axis A1 of the cylinder 2. The crank arm is rotatably mounted on the crankshaft. The piston 3 reciprocates in the internal space along the central axis A1 of the cylinder 2, in parallel with the rotation of the crank arm with the crankshaft as the axis of rotation. The axial direction of the cylinder 2 is aligned with the direction of movement of the piston 3.

[0013] During the intake stroke of the internal combustion engine 1, piston 3 descends toward the crankshaft relative to the intake valve, reaching bottom dead center. During the compression stroke, piston 3 rises from bottom dead center toward the intake valve, reaching top dead center. During the expansion stroke, the fuel gas supplied into cylinder 2 burns. Also during the expansion stroke, piston 3 descends again toward bottom dead center. And during the exhaust stroke, it rises again toward the intake valve from bottom dead center.

[0014] In piston 3, for example, the piston crown surface 12, top land 13, top ring groove 14, second land 15, second ring groove 17, third land 18, oil ring groove 19, and piston skirt 21 are formed in order from the intake valve side.

[0015] The piston crown surface 12 is the end face on the intake valve side of the piston 3 and faces the intake valve side.

[0016] The top ring 7 is positioned in the top ring groove 14. The second ring 8 is positioned in the second ring groove 17. The oil ring 9 is positioned in the oil ring groove 19.

[0017] The piston skirt 21 has an end face 21a facing the crankshaft side on the piston 3. The end face 21a corresponds to the lower end of the piston 3. A piston pin hole 22 into which the piston pin 4 is inserted is formed in the piston skirt 21. The central axis A2 of the piston pin 4 is coaxial or approximately coaxial with the central axis of the piston pin hole 22.

[0018] The piston 3 performs a so-called oscillating motion, rotating around the central axis A2 of the piston pin 4 as the pivot point, in parallel with the rotation of the crank arm. In Figure 2, the central axis A3 of the piston 3 is not inclined with respect to the central axis A1 of the cylinder 2, but is shown aligned with the central axis A1 of the cylinder 2. This state of the piston 3 is called the neutral state. The central axis A3 of the piston 3 is, for example, coaxial with the central axis of the top land 13. However, it is not limited to this, and the central axis A3 of the piston 3 may be coaxial with the central axis of any component of the piston 3, such as the second land 15, the third land 18, or the piston skirt 21.

[0019] FIG. 3 is a schematic diagram showing an example of the configuration of the internal combustion engine 1 when the piston 3 according to the embodiment is inclined with respect to the neutral state. In the piston 3, a width direction (X-axis direction in FIGS. 2 and 3) that intersects (is orthogonal or substantially orthogonal) with both the direction along the central axis A1 of the cylinder 2 (Y-axis direction in FIGS. 2 and 3) and the direction in which the piston pin 4 extends (Z-axis direction in FIGS. 2 and 3) is defined. In the expansion process, the piston 3 receives the maximum thrust force toward one side in the width direction due to the combustion of the fuel gas supplied into the cylinder 2. As a result, as shown in FIG. 3, the portion located on the intake valve side with respect to the piston pin hole 22 in the neutral state inclines from the neutral state toward one side in the width direction. Further, among the portions of the piston 3, the portion located on the crankshaft side with respect to the piston pin hole 22 in the neutral state inclines from the neutral state toward the opposite side to the portion located on the intake valve side. Hereinafter, this state is referred to as the first inclined state. Further, due to the piston receiving the maximum thrust force, the side toward which the portion located on the crankshaft side with respect to the piston pin hole 22 in the neutral state inclines is referred to as the thrust side Th (negative X-axis direction), and the opposite side is referred to as the anti-thrust side ATh (positive X-axis direction). Hereinafter, one side in the direction in which the piston pin 4 extends is referred to as the front side Fr, and the side opposite to the front side Fr is referred to as the rear side Rr.

[0020] On the other hand, during the movement of the piston 3, there may be a case where the portion located on the crankshaft side with respect to the piston pin hole 22 in the neutral state inclines from the neutral state toward the anti-thrust side ATh, and the portion located on the intake valve side with respect to the piston pin hole 22 inclines from the neutral state toward the thrust side Th. That is, there may be a case where the piston 3 inclines with an inclination opposite to the inclination of the piston 3 in the first inclined state. Hereinafter, such an inclined state is referred to as the second inclined state. The piston 3 inclines in either the first inclined state or the second inclined state.

[0021] When the piston 3 inclines, the contact area between the thrust side Th portion of the outer peripheral surface of the piston ring and the inner wall surface 11 becomes smaller than the contact area in the neutral state. At this time, the above-mentioned portion, for example, makes edge contact with the inner wall surface 11. Thereby, the contact pressure that the inner wall surface 11 receives from the above-mentioned portion when the piston 3 inclines becomes larger than the contact pressure in the neutral state. Similarly, the contact pressure that the inner wall surface 11 receives from the anti-thrust side ATh portion also becomes larger when the piston 3 inclines than the contact pressure in the neutral state. Therefore, the contact states between the thrust side Th and anti-thrust side ATh portions of the outer peripheral surface of the piston ring and the inner wall surface 11 when the piston 3 inclines are different from the contact states in the neutral state.

[0022] On the other hand, in the front-rear direction, the piston 3 does not incline or hardly inclines. For this reason, during the movement of the piston 3, the contact area between the rear side Rr or front side Fr portion of the outer peripheral surface of the piston ring and the inner wall surface 11 does not change or hardly changes. Therefore, when the piston 3 inclines, the contact states on the rear side Rr and front side Fr of the piston ring are different from the contact states on the thrust side Th and anti-thrust side ATh.

[0023] Also, in the piston skirt 21, the thrust side Th portion is not in contact with the inner wall surface 11 in the neutral state. On the other hand, the thrust side Th portion may come into contact with the inner wall surface 11 depending on the inclination of the piston 3. That is, the contact state of the thrust side Th portion changes depending on the inclination of the piston 3. Similarly, the contact state of the anti-thrust side ATh portion of the piston skirt 21 changes depending on the inclination of the piston 3.

[0024] In contrast, the rear side Rr and front side Fr portions of the piston skirt 21 are not in contact with the inner wall surface 11 whether the piston 3 is in the neutral state or inclined. Thus, during the movement of the piston 3, the contact states on the rear side Rr and front side Fr of the piston skirt 21 are different from the contact states on the thrust side Th and anti-thrust side ATh.

[0025] Furthermore, during the compression process, the combustion pressure at the thrust-side Th portion of the piston ring's outer surface may differ from the combustion pressure at the anti-thrust-side AThr portion of the piston ring's outer surface. Therefore, the contact state between the thrust-side Th portion of the piston ring's outer surface and the inner wall surface 11 may differ from the contact state between the anti-thrust-side AThr portion of the piston ring's outer surface and the inner wall surface 11. Additionally, due to the inner circumferential portion of the piston ring being subjected to the pressure of the compressed gas, the contact state between the thrust-side Th portion of the piston ring's outer surface and the inner wall surface 11 may differ from the contact state between the anti-thrust-side AThr portion of the piston ring's outer surface and the inner wall surface 11. Furthermore, the contact state between the thrust-side Th portion of the piston skirt 21 and the inner wall surface 11 may differ from the contact state between the anti-thrust-side AThr portion of the piston skirt 21 and the inner wall surface 11.

[0026] Next, the configuration of the inner wall surface 11 of cylinder 2 will be described. Figure 4 is a schematic diagram of the internal space and its vicinity of cylinder 2 according to the embodiment, viewed from the intake valve side. Figure 5 is a schematic diagram showing a part of the configuration of the inner wall surface 11 of cylinder 2 according to the embodiment. In Figure 5, cylinder 2 is unfolded, and a part of the inner wall surface 11 is viewed from the side of the internal space formed by the inner wall surface 11 of cylinder 2. The vertical direction in Figure 5 is along the axial direction of cylinder 2. The imaginary upper line P1 shown by the dashed line in Figure 5 represents the portion of the inner wall surface 11 that faces the top ring 7 when the piston 3 is at top dead center. The imaginary upper line P2 shown by the dashed line in Figure 5 represents the portion of the inner wall surface 11 that faces the end face 21a of the piston skirt 21 when the piston 3 is at bottom dead center.

[0027] As shown in Figure 4, the inner wall surface 11 has a first region 11Th on the thrust side Th, a second region 11ATh on the anti-thrust side ATh, a third region 11Fr on the front side Fr, and a fourth region 11Rr on the rear side Rr. In one example, each of the first region 11Th, the second region 11ATh, the third region 11Fr, and the fourth region 11Rr is formed over the entire length of the range in which the piston skirt 21 can move in the vertical direction of the cylinder 2. Specifically, the upper end of each region is located on the intake valve side of the inner wall surface 11, relative to the portion of the inner wall surface 11 that faces the intake valve side end of the piston skirt 21 when the piston 3 is at top dead center. Also, the lower end of each region is located on the crankshaft side of the inner wall surface 11, relative to the portion of the inner wall surface 11 that faces the end face 21a of the piston skirt 21 when the piston 3 is at bottom dead center (the portion of the straight line P2). However, this is not limited to this example; in other examples, each region may be formed over the entire length of the range in which the piston ring can move in the vertical direction of the cylinder 2. Specifically, the upper end of each region is located on the intake valve side of the inner wall surface 11, beyond the portion of the inner wall surface 11 that faces the top ring 7 when the piston 3 is at top dead center (the portion of the straight line P1). The lower end of each region is located on the crankshaft side of the inner wall surface 11, beyond the portion of the inner wall surface 11 that faces the oil ring 9 when the piston 3 is at bottom dead center. Alternatively, the upper end of each region may be located on the intake valve side of the portion of the straight line P1, and the lower end of each region may be located on the crankshaft side of the portion of the straight line P2. Furthermore, the upper end of each region may coincide with the upper end of the inner wall surface 11, and the lower end of each region may coincide with the lower end of the inner wall surface 11.

[0028] The first region 11Th and the second region 11ATh are, for example, aligned in the circumferential direction of the inner wall surface 11 without vertical displacement relative to each other. However, the configuration is not limited to this, and at least two regions of each region may be aligned in the circumferential direction of the inner wall surface 11 without vertical displacement relative to each other.

[0029] In this embodiment, the first region 11Th is not continuous with either the third region 11Fr or the fourth region 11Rr in the circumferential direction of the cylinder 2. Similarly, the second region 11ATh is not continuous with either the third region 11Fr or the fourth region 11Rr in the circumferential direction of the cylinder 2. Specifically, the first region 11Th is adjacent to the third region 11Fr and located away from the third region 11Fr in the circumferential direction of the cylinder 2. Between the first region 11Th and the third region 11Fr, a region that is neither of the respective regions is formed. Similarly, the first region 11Th is adjacent to the fourth region 11Rr and located away from the fourth region 11Rr in the circumferential direction of the cylinder 2. Similarly, the second region 11ATh is adjacent to both the third region 11Fr and the fourth region 11Rr and located away from both the third region 11Fr and the fourth region 11Rr in the circumferential direction of the cylinder 2.

[0030] Here, the friction characteristics of the inner wall surface 11 will be described. Different friction characteristics result in different friction even under the same contact conditions. In each of the multiple parts located circumferentially offset from each other on the inner wall surface 11, the friction characteristics are adjusted according to the contact condition between that part and the piston 3. For example, in the first region 11Th, the friction characteristics are adjusted according to the contact condition between the first region 11Th and the piston 3, and in the third region 11Fr, the friction characteristics are adjusted according to the contact condition between the third region 11Fr and the piston 3. The same applies to the friction characteristics of other regions. At least the friction characteristics of the inner wall surface 11 in the first region 11Th or the second region 11ATh are different from the friction characteristics in at least one of the third or fourth regions. In a preferred example, the friction characteristics in the first region 11Th and the second region 11ATh are different from the friction characteristics in the third region 11Fr and the fourth region 11Rr.

[0031] In a more preferable example, the frictional properties of the first region 11Th are different from those of the second region 11ATh. However, the frictional properties of the first region 11Th and the second region 11ATh may be identical.

[0032] Furthermore, the frictional characteristics of the region sandwiched between the first region 11Th and the third region 11Fr may be different from those of the first region 11Th and the third region 11Fr. Similarly, the frictional characteristics of the region sandwiched between the first region 11Th and the fourth region 11Rr may be different from those of the first region 11Th and the fourth region 11Rr. Furthermore, the frictional characteristics of the region sandwiched between the second region 11ATh and the third region 11Fr may be different from those of the second region 11ATh and the third region 11Fr. Furthermore, the frictional characteristics of the region sandwiched between the second region 11ATh and the fourth region 11Rr may be different from those of the second region 11ATh and the fourth region 11Rr. Furthermore, the region between the first region 11Th and the third region 11Fr may be divided into multiple regions, and the frictional properties of each of these regions may differ from those of the others. The same explanation can be applied to the region between the first region 11Th and the fourth region 11Rr, the region between the second region 11ATh and the third region 11Fr, and the region between the second region 11ATh and the fourth region 11Rr.

[0033] On the inner wall surface 11, for example, a surface pattern is formed. By varying the specifications of the surface pattern according to the part of the inner wall surface 11, a configuration is realized in which the friction characteristics vary depending on the part. The specifications of the surface pattern are, for example, grooves formed on the inner wall surface 11. The specifications of the surface pattern can be varied according to, for example, the depth of the grooves, the angle between the grooves and the direction along the vertical direction of the cylinder 2, and the area ratio of the grooves formed on the inner wall surface 11. In this embodiment, the surface pattern 31 in the first region 11Th and the surface pattern 32 in the second region 11ATh are different from the surface pattern 33 in the third region 11Fr and the surface pattern 34 in the fourth region 11Rr.

[0034] Furthermore, it is also possible to achieve a configuration in which friction characteristics differ depending on the part of the inner wall surface 11 by applying different heat treatments or the like to different parts of the inner wall surface 11, thereby varying the hardness of the inner wall surface 11 depending on the part. Alternatively, a configuration in which friction characteristics differ depending on the part can be achieved by varying both the surface pattern and the hardness of the inner wall surface 11 depending on the part.

[0035] According to the embodiment described above, the inner wall surface 11 has a first region 11Th on the thrust side Th, a second region 11ATh on the anti-thrust side AThr, a third region 11Fr on the front side Fr, and a fourth region 11Rr on the rear side Rr. The friction characteristics between the piston 3 and the inner wall surface 11 in at least the first region 11Th and the second region 11ATh are different from the friction characteristics in at least the third region 11Fr and the fourth region 11Rr. As mentioned above, the contact state at the rear side Rr and the front side Fr is different from the contact state at the thrust side Th and the anti-thrust side AThr, but the friction characteristics of the inner wall surface 11 are adjusted according to the contact state. This makes it possible to reduce friction between the piston 3 and the inner wall surface 11. Furthermore, with this configuration, friction can be reduced compared to an inner wall surface 11 having uniform friction characteristics around its entire circumference, such as an inner wall surface 11 with a uniform surface pattern formed around its entire circumference.

[0036] Furthermore, according to the embodiments described above, the contact state between the thrust-side Th portion of the piston 3, including the outer circumferential surface of the piston ring and the piston skirt 21, and the inner wall surface 11 may differ from the contact state between the anti-thrust-side AThr portion of the piston 3 and the inner wall surface 11. In one example, the friction characteristics of the first region 11Th are different from those of the second region 11ATh, and a configuration is realized in which the friction characteristics differ depending on the contact state, thereby further reducing the friction between the piston 3 and the inner wall surface 11.

[0037] Furthermore, according to one example of the embodiment described above, each of the first region 11Th, the second region 11ATh, the third region 11Fr, and the fourth region 11Rr is formed over the entire length of the range in which the piston skirt 21 can move in at least in the vertical direction of the cylinder 2. This makes it possible to reduce friction between the piston skirt 21 and the inner wall surface 11.

[0038] Furthermore, according to one example of the above-described embodiment, each of the first region 11Th, the second region 11ATh, the third region 11Fr, and the fourth region 11Rr is formed over the entire length of the cylinder 2, at least in the vertical direction, over the range in which the piston ring can move. This reduces friction between the piston ring and the inner wall surface 11.

[0039] Furthermore, according to one example of the above-described embodiment, it is possible to provide an internal combustion engine 1 having an inner wall surface 11 whose friction characteristics between the piston 3 and the inner wall surface 11 in the first region 11Th and the second region 11ATh are different from those in the third region 11Fr and the fourth region 11Rr. And it is possible to provide a vehicle 100 equipped with the above-described internal combustion engine 1.

[0040] In this embodiment, a piston 3 used in a diesel engine, one of the internal combustion engines 1, is described as an example, but the invention is not limited to this. The piston 3 may be used not only in a diesel engine, but also in other internal combustion engines 1, such as a gasoline engine.

[0041] Furthermore, in the embodiment, a configuration in which the first region 11Th, the second region 11ATh, the third region 11Fr, and the fourth region 11Rr are not continuous in the circumferential direction is described as an example, but the embodiment is not limited to this. A configuration in which at least two or more of the regions are continuous in the circumferential direction is also possible.

[0042] Furthermore, the present invention is not limited to the embodiments described above, and can be modified in various ways during implementation without departing from its essence. Also, each embodiment may be combined as appropriate, and in that case, combined effects can be obtained. Moreover, the above embodiments include various inventions, and various inventions can be extracted by selecting combinations from the multiple disclosed constituent elements. For example, if the problem can be solved and effects obtained even if some constituent elements are deleted from all the constituent elements shown in the embodiment, then the configuration with these deleted constituent elements can be extracted as an invention. [Explanation of symbols]

[0043] 1...Internal combustion engine, 2...Cylinder, 3...Piston, 4...Piston pin, 7...Top ring, 8...Second ring, 9...Oil ring, 11...Inner wall surface, 11Th...First area, 11ATh...Second area, 11Fr...Third area, 11Rr...Fourth area, 12...Piston crown surface, 13...Top land, 14...Top ring groove, 15...Second land 15, 17...Second ring groove, 18...Third land, 19...Oil ring groove, 21...Piston skirt, 22...Piston pin hole, 31-34...Surface pattern, 40...Wheel, 100...Vehicle, 110...Transmission, A1-A3...Center axis, ATh...Anti-thrust side, Fr...Front side, Th...Thrust side, Rr...Rear side.

Claims

1. It has an inner wall surface that forms an internal space in which the piston is arranged, The inner wall surface has a first region on the thrust side, a second region on the anti-thrust side, a third region on the front side, and a fourth region on the rear side. The frictional characteristics of the inner wall surface in at least the first or second region are different from the frictional characteristics in at least the third or fourth region. Cylinder.

2. The cylinder according to claim 1, wherein the frictional characteristics of the inner wall surface in the first and second regions are different from the frictional characteristics in the third and fourth regions.

3. The cylinder according to claim 1, wherein the first region and the second region are aligned in the circumferential direction of the inner wall surface without being offset from each other in the vertical direction.

4. The cylinder according to claim 1, wherein each of the first, second, third, and fourth regions is formed over the entire length of the piston skirt of the piston, at least in the vertical direction.

5. The cylinder according to claim 1, wherein each of the first, second, third, and fourth regions is formed over the entire length of the piston ring of the piston, at least in the vertical direction.

6. The cylinder according to claim 1, wherein the friction characteristics of the first region are different from those of the second region.

7. The cylinder according to claim 1, wherein in at least the first region or the second region, at least one of the surface pattern formed on the inner wall surface and the hardness of the inner wall surface is different from that of at least the third region or the fourth region.

8. A cylinder according to any one of claims 1 to 7, A piston is disposed in the internal space formed by the cylinder, An internal combustion engine equipped with [a specific feature / feature].

9. A vehicle equipped with an internal combustion engine as described in claim 8.

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