JP2005201085A - Cylinder block and engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder block and an engine for suitably avoiding trouble involved with deformation of a bore wall caused by a combustion gas seal structure. <P>SOLUTION: In the bore wall 18 between a cylinder bore 16 and a water jacket 17, at a position lower than a sliding range A of a piston ring 15a, a thin wall portion 18a where a wall thickness of the bore wall 18 is thinned as compared with the sliding range A is formed by recessing a wall surface. A cylinder head 14 is attached to an upper part of the cylinder block 12 through a gasket 13 and when it is fixed by head bolts not shown, an upper end surface 18b of the bore wall 18 is strongly pressed by a thick wall portion 13a of the gasket 13. At that time, the pressing force is absorbed through elastic deformation of the thin wall portion 18a of the bore wall 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cylinder block in which a water jacket is formed around a cylinder bore in which a piston is reciprocated, and an engine formed by assembling such a cylinder block to a cylinder head.

  As shown in FIG. 6A, a cylinder block 100 applied to a water-cooled engine includes a cylinder bore 102 in which a piston 101 is reciprocally movable, and a water jacket 103 formed around the cylinder bore. It is configured. The cylinder block 100 is assembled to the cylinder head 104 with a head bolt or the like.

In many water-cooled engines, a gasket 105 is interposed between the cylinder block 100 and the cylinder head 104 to prevent leakage of combustion gas from the combustion chamber to the outside. Generally, the gasket 105 is formed with a thick portion 105a whose thickness is larger than that of the other portion at a portion corresponding to the outer edge 106a of the cylinder bore 102, and increases the surface pressure of the outer edge 106a of the cylinder bore 102. Thus, the sealing property of the combustion gas is ensured (as described above, Patent Documents 1 to 5).
JP 2000-310155 A Japanese Patent Laid-Open No. 11-6462 JP 2002-138897 A JP 2000-240502 A JP 2002-97999 A

  Incidentally, in order to improve the sealing performance against the combustion gas, it is necessary to increase the surface pressure of the outer peripheral portion of the cylinder bore 102 by increasing the thickness of the thick portion 105a. On the other hand, in recent years, in order to reduce the weight and size of the cylinder block 100, the bore wall 106 and the like between the cylinder bore 102 and the water jacket 103 tend to be formed thinner.

  However, when the thick part 105a is thickened and the bore wall 106 is thinned, the following problems occur. That is, when such a cylinder block 100 is assembled to the cylinder head 104, the thick wall portion 105a receives a strong pressure from above, and the reduced bore wall 106 is shown in FIG. As shown, the elastic deformation occurs greatly. As a result, the roundness of the cylinder bore 102 decreases, and a sufficient surface pressure between the cylinder bore 102 and the piston ring 107 cannot be secured, which may increase the oil consumption. Further, along with the deformation of the bore wall 106, the journal portion 108 of the crankshaft formed therebelow is also deformed, so that its roundness and coaxiality are lowered, and the crankshaft friction is increased. There is also a risk of it.

  Patent Document 1 describes a technique for suppressing deformation of the bore wall due to the combustion pressure in the combustion chamber by increasing the thickness of the bore wall toward the top side of the cylinder block. Patent Documents 2, 3 and 4 disclose a technique for suppressing deformation of the bore wall due to tightening of the head bolt, and Patent Document 5 further describes deformation of the bore wall due to thermal expansion corresponding to combustion in the combustion chamber. Each suppression technique is described. However, none of these techniques is an effective measure for the problems associated with the deformation of the bore wall due to the combustion gas seal structure such as the gasket as described above. The actual situation has not been proposed yet.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a cylinder block and an engine that can suitably suppress problems associated with deformation of the bore wall due to the combustion gas seal structure. is there.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The invention according to claim 1 is a cylinder block in which a water jacket is formed around a cylinder bore in which a piston is reciprocated, and is located in a bore wall between the cylinder bore and the water jacket, and a sliding range of the piston ring. The gist of the invention is that the wall portion is recessed in a lower position to form a thin portion in which the thickness of the bore wall is reduced compared to the sliding range.

  In the above configuration, in the bore wall between the cylinder bore of the cylinder block and the water jacket, the wall surface is recessed in a concave shape, so that the bore wall can be selectively formed in a portion below the sliding range with the piston ring. A thin part with a reduced thickness is formed. In such a cylinder block, when the pressure from above by the combustion gas seal structure when it is assembled to the cylinder head acts on the bore wall, the accompanying deformation of the bore wall is concentrated on the thin wall portion. Therefore, the deformation in the sliding range of the bore wall with the piston ring is suitably suppressed. Further, since the pressing force by the combustion gas seal structure is absorbed by the thin portion, the deformation of the journal portion of the crankshaft corresponding to the pressing force is also suppressed. Therefore, according to the said structure, the malfunction accompanying the deformation | transformation of the bore wall by a combustion gas seal structure can be suppressed suitably.

In the present specification, the vertical direction of the cylinder block is defined as an upper side on the side where the cylinder head is assembled and a lower side on the crankcase side.
The gist of the invention described in claim 2 is that, in the invention described in claim 1, the thickness of the bore wall in the sliding range is made constant.

In the above configuration, since the amount of thermal deformation of the bore wall in the sliding range of the piston ring is constant, a decrease in the roundness of the cylinder bore during combustion can be suppressed.
The gist of the invention according to claim 3 is that, in the invention according to claim 1 or 2, the water jacket is set to have a depth to the lower end of the cylinder bore.

  In the above configuration, since the water jacket is extended to the lower end portion of the cylinder bore, the length of the bore wall in the vertical direction of the cylinder block is increased accordingly, so that the thin portion can be provided in a wider range. . Accordingly, it is possible to more reliably and easily provide the thin portion having a size capable of sufficiently absorbing the pressing force outside the sliding range of the piston ring.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the thin portion is formed by recessing a wall surface on the water jacket side of the bore wall in a concave shape. This is the gist.

  In the said structure, the said thin part is formed by denting a bore wall concavely from a water jacket side. Therefore, it becomes possible to make the peripheral wall of the cylinder bore a smooth surface without irregularities, and it becomes easy to finish the cylinder bore peripheral wall.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the upper end of the bore wall protrudes above the upper end of the outer peripheral wall of the water jacket. Is the gist.

In the above configuration, when the cylinder head is assembled, the surface pressure between the gasket and the upper end of the bore wall can be increased, so that the sealing performance of the cylinder bore can be improved.
According to a sixth aspect of the present invention, in an engine formed by assembling a cylinder block having a water jacket around a cylinder bore in which a piston is reciprocated to a cylinder head, the cylinder block is provided between the cylinder bore and the water jacket. A thin-walled portion in the bore wall of the cylinder block that is recessed below the sliding range of the piston ring so that the wall thickness of the bore wall is reduced compared to the sliding range. And a projecting portion that protrudes more toward the cylinder block than the other part of the lower end surface is formed at a part of the lower end surface of the cylinder head that faces the upper end surface of the bore wall. To do.

  In the above configuration, when the cylinder head and the cylinder block are assembled, the surface pressure between the gasket and the upper end of the bore wall can be increased, so that the sealing performance of the cylinder bore can be improved. In this case, the pressing force by the combustion gas seal structure when the cylinder block is assembled to the cylinder head is absorbed by the thin wall portion provided at a position below the sliding range of the piston ring. The deformation of the bore wall in the moving range is preferably suppressed.

(First embodiment)
Hereinafter, a first embodiment embodying the present invention will be described with reference to FIGS.

  As shown to Fig.1 (a), the engine 11 is provided with the cylinder block 12 in which the cylinder bore 16 with which the piston 15 is arrange | positioned was formed, and the cylinder head 14 attached to the upper part.

  Between the opposing surfaces of the cylinder block 12 and the cylinder head 14, a gasket 13 that prevents leakage of combustion gas or the like is interposed. A peripheral portion of the cylinder bore 16 of the gasket 13 is a thick portion 13a that is thicker than other portions. The thick portion 13a has a combustion gas seal structure that increases the surface pressure between the opposed surfaces of the cylinder block 12 and the cylinder head 14 at the periphery of the cylinder bore 16 to prevent combustion gas leakage. A piston ring 15 a is attached to the outer periphery of the piston 15 accommodated in the cylinder bore 16 of the cylinder block 12. The piston 15 is reciprocated in the cylinder bore 16 with the piston ring 15 a being in sliding contact with the peripheral wall of the cylinder bore 16.

  Around the cylinder bore 16, a water jacket 17 through which cooling water is circulated is formed. In this cylinder block 12, the water jacket 17 is formed to a depth up to the lower end of the cylinder bore 16. Incidentally, the water jacket 17 of the cylinder block 12 is configured as a so-called open deck type water jacket whose upper end is opened on the upper surface of the cylinder block 12.

  The cylinder block 12 has a bore wall 18 that partitions the cylinder bore 16 and the water jacket 17, and the wall thickness of the bore wall 18 in the sliding range A of the piston ring 15a is constant. On the other hand, the position below the sliding range A of the piston ring 15a of the bore wall 18 is recessed in a concave shape from the water jacket 17 side toward the cylinder bore 16 side. Thereby, the lower side of the bore wall 18 below the sliding range A of the piston ring 15a is a thin portion 18a which is thinner than the thickness of the sliding range A of the piston ring 15a. That is, in the cylinder block 12, a portion having lower rigidity than other portions is intentionally formed below the sliding range A of the piston ring 15a of the bore wall 18.

  Below the cylinder bore 16 of the cylinder block 12 is formed a crankcase 19 in which a crankshaft serving as an engine output shaft is accommodated. A journal portion 20 is formed in the crankcase 19 to rotatably support the crankshaft.

  As shown in FIG. 1B, when the cylinder block 12 and the cylinder head 14 are fastened and fixed, the upper end surface 18b of the bore wall 18 is formed by the thick portion 13a of the gasket 13 interposed therebetween. Pressed strongly. At this time, the thin-walled portion 18a at the lower end portion of the thinned bore wall 18 is elastically deformed flexibly and absorbs most of the pressing force. For this reason, the deformation of the bore wall 18 due to the pressing of the thick portion 13a concentrates on the thin portion 18a, and the bore wall 18 and the journal portion 20 in the sliding range A of the piston ring 15a are not pressed. The accompanying deformation will be suitably suppressed.

According to the embodiment detailed above, the following effects are exhibited.
(1) By thinning the wall surface of the bore wall 18 of the cylinder block 12 into a concave shape, a thin wall in which the wall thickness of the bore wall 18 is selectively reduced in a portion below the sliding range A of the piston ring 15a. A portion 18a is formed. For this reason, when the pressure from above by the thick part 13a of the gasket 13 when it is assembled to the cylinder head 14 acts on the bore wall 18, the deformation of the bore wall 18 associated therewith is concentrated on the thin part 18a. It comes to occur. Therefore, the deformation in the sliding range A with the piston ring 15a of the bore wall 18 is suitably suppressed. Further, since the pressing force by the thick portion 13a is absorbed by the thin portion 18a of the bore wall 18, deformation of the journal portion 20 of the crankshaft according to the pressing force is also suppressed. Therefore, the malfunction accompanying the deformation | transformation of the bore wall 18 by the thick part 13a can be suppressed suitably. As a result, the upper limit of the pressing force of the thick wall portion 13a that can suppress the decrease in the roundness of the cylinder bore 16 and the decrease in the roundness and the coaxiality of the journal portion 20 of the crankshaft to an allowable range is improved. . Therefore, it becomes easy to ensure the combustion gas sealing performance.

  (2) Since the wall thickness of the bore wall 18 in the sliding range A of the piston ring 15a is constant, the amount of thermal deformation is constant. For this reason, the fall of the roundness of the cylinder bore 16 at the time of combustion can be suppressed.

  (3) Since the water jacket 17 is extended to the lower end portion of the cylinder bore 16 and the length of the bore wall 18 in the vertical direction of the cylinder block 12 is increased accordingly, the thin portion 18a can be provided in a wider range. it can. Therefore, the thin portion 18a having a size capable of sufficiently absorbing the pressing force can be more reliably and easily provided outside the sliding range A of the piston ring 15a.

  (3) The thin wall portion 18a is formed by recessing the bore wall 18 from the water jacket 17 side. For this reason, it becomes possible to make the surrounding wall of the cylinder bore 16 into a smooth surface without unevenness, and it becomes easy to finish the cylinder bore 16 surrounding wall.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. 2 with a focus on differences from the first embodiment.

  As shown in FIG. 2 (a), also in the cylinder block 40 of the present embodiment, the thickness of the bore wall 18 below the sliding range A of the piston ring 15a is thinner than the other parts. The thin portion 18a thus formed is formed. On the other hand, in the cylinder block 40 of the present embodiment, the upper end surface 18b of the bore wall 18 protrudes above the upper end surface 22a of the outer peripheral wall 22 of the water jacket 17 in a state before assembly with the cylinder head 14. Is formed.

  When the cylinder head 14 is fastened and assembled to the upper portion of the cylinder block 40 as shown in FIG. 2 (b), the upper end surface 18b of the bore wall 18 protruding upward as described above is The jacket 17 is pushed down to the same height as the upper end surface 22 a of the outer peripheral wall 22. Since the deformation of the bore wall 18 accompanying the depression at this time concentrates on the thin wall portion 18a, the sliding range A of the piston ring 15a of the bore wall 18 and the deformation of the journal portion 20 of the crankshaft are suitably suppressed. The

  In the present embodiment, the shimless bead type gasket 21 constituted by a plate material formed with a bead 21a bent in a convex shape on the periphery of the cylinder bore 16 is used as a head gasket for preventing leakage of combustion gas and the like. Adopted. Although the shimless bead type gasket 21 has a simple structure and low cost, the seal surface pressure is generated by the elastic recovery force of the bead 21a, so that the seal surface pressure generated by the gasket itself is low and the combustion pressure is high. Adoption to the engine is usually difficult. Further, in the shimless bead type gasket 21, the bead 21a repeatedly expands and contracts in accordance with the gap fluctuation between the cylinder block 40 and the cylinder head 14 due to the cylinder head 14 being pushed up by the combustion pressure, and the durability is reduced due to fatigue. There are concerns.

  In this respect, in the present embodiment, the bore wall 18 is assembled in a compressed state in the cylinder extending direction, and the seal surface pressure is also generated by the elastic recovery force. Therefore, even a shimless bead type gasket 21 having a low seal surface pressure generated by the gasket itself can ensure a sufficient combustion gas sealing performance. Further, the elastic recovery force of the thin wall portion 18a causes the upper end surface 18b of the bore wall 18 to follow the push-up of the bottom surface of the cylinder head 14 by the combustion pressure, so that the gap variation between the cylinder block 40 and the cylinder head 14 is suppressed. become. Therefore, repeated expansion and contraction of the bead 21a is reduced, and the reliability of the shimless bead type gasket 21 can be improved. If a sufficient sealing surface pressure can be ensured by only the elastic recovery force of the bore wall 18, the structure related to the generation of the sealing surface pressure such as the thick wall portion and the bead at the periphery of the cylinder bore 16 of the gasket is omitted. Anyway.

(Third embodiment)
The structure in which the thin-walled portion 18a is formed at a position below the sliding range A of the piston ring 15a of the bore wall 18 in the cylinder blocks 12 and 40 of each of the above embodiments is a so-called closed upper end opening of the water jacket. The present invention can be similarly applied to a cylinder block having a closed deck type water jacket.

  For example, in the cylinder block 30 provided with the closed deck type water jacket 29 shown in FIG. 3A, the wall surface of the bore wall 31 is positioned below the sliding range A of the piston ring 15a and the water jacket 29 By being recessed from the side, a thin portion 31a having a thickness smaller than that of the sliding range A is formed. Even in such a case, the depression of the bore wall 31 due to the seal surface pressure of the combustion gas seal structure is absorbed by the elastic deformation of the thin portion 31a, so that the sliding range A of the piston ring 15a of the bore wall 31 and the journal of the crankshaft The deformation of the part 20 is preferably suppressed.

  As shown in FIG. 3 (a), a protrusion 31b is formed on the top surface of the cylinder block 30 and corresponding to the upper end surface of the bore wall 31. You may make it do. When such a cylinder block 30 is assembled to the cylinder head 14, as shown in FIG. 3B, the top surface of the protrusion 31 b is substantially different from other parts of the top surface of the cylinder block 30 due to the bottom surface of the cylinder head 14. It is pushed down to the same height. As a result, the bore wall 31 is assembled in a compressed state in the cylinder extending direction, and a seal surface pressure is generated by its elastic recovery force. Can be played.

Each embodiment described above may be changed as follows.
In the case of a cylinder block with a cylinder liner, it is possible to configure a cylinder block having the same effects as those of the third embodiment in the mode shown in FIG. That is, in the cylinder block 24 shown in FIG. 4A, the cylinder liner 26 is mounted on the inner periphery of the cylinder bore 25. Here, the upper end portion of the cylinder liner 26 protrudes above the upper end surface of the cylinder block 24 on which the cylinder head 14 is placed. When such a cylinder block 24 is assembled to the cylinder head 14, as shown in FIG. 4B, the upper end portion of the cylinder liner 26 protruding upward is pushed down by the bottom surface of the cylinder head 14, and the bore wall 27 Is assembled in a compressed state in the cylinder stretching direction. Since the seal surface pressure is generated by the elastic recovery force of the bore wall 27, the same effects as those of the second embodiment or effects equivalent thereto can be achieved.

  ・ Even in the cylinder block 12 having the open deck type water jacket as shown in FIG. 1, the cylinder liner is mounted on the inner periphery of the cylinder bore 16 with the upper end surface protruding above the top surface of the cylinder block. By doing so, the same effect as the cylinder block 40 of 2nd Embodiment can be show | played.

  As shown in FIG. 5 (a), a protrusion projecting toward the cylinder block 12 from the other portion of the lower end surface at a portion facing the upper end surface 18b of the bore wall 18 on the lower end surface of the cylinder head 33. Even when the portion 33a is formed, the same effects as those of the first to third embodiments can be obtained. When such a cylinder head 33 is assembled to the cylinder block 12, as shown in FIG. 5B, the upper end surface 18b of the bore wall 18 is pushed down by the convex portion 33a. At this time, the deformation of the bore wall 18 due to the depression is concentrated on the thin wall portion 18a, and the deformation of the sliding range A of the piston ring 15a of the bore wall 18 and the journal portion 20 of the crankshaft is preferably suppressed. Is done. As a result, since the bore wall 18 is assembled in a compressed state in the cylinder extending direction, the seal surface pressure is generated by the elastic recovery force of the bore wall 18.

  In each of the above embodiments, the thin wall portion is formed by recessing the wall surface of the bore wall on the water jacket side, but the same can be achieved by recessing the wall surface of the bore wall on the cylinder bore side. The thin wall portion can be formed. Also in this case, effects other than the above (2) can be obtained.

  In each of the above embodiments, the wall thickness of the bore wall in the sliding range A of the piston ring 15a is made constant. However, the wall thickness may be changed depending on the part as necessary. However, in such a case, the wall thickness of the bore wall in the sliding range A of the piston ring 15a is such that the roundness of the cylinder bore can be sufficiently suppressed at least against the pressing by the combustion gas seal structure when the cylinder head is assembled. It is necessary to make it more than the thickness which can ensure.

  In each of the above embodiments, the water jacket is set to have a depth up to the lower end of the cylinder bore. However, the thin wall portion having a size capable of sufficiently absorbing the pressure by the combustion gas seal structure when assembling the cylinder head is provided. If it can be formed outside the sliding range A of the piston ring 15a, it does not necessarily have to be so.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing (a) an exploded sectional structure of an engine and (b) a sectional structure in an assembled state in the first embodiment of the present invention. Sectional drawing which shows together (a) decomposition | disassembly sectional structure of an engine, and (b) sectional structure in the assembly state about 2nd Embodiment of this invention. Sectional drawing which shows together (a) decomposition | disassembly sectional structure of an engine, and (b) sectional structure in the assembly state about 3rd Embodiment of this invention. Sectional drawing which shows combined with (a) decomposition | disassembly cross-section structure of an engine, and (b) the cross-section structure in the assembly | attachment state about the example of a change of the embodiment. Sectional drawing which shows together (a) decomposition | disassembly cross-section structure of an engine, and (b) cross-section structure in the assembly | attachment state about another modification of the embodiment. Sectional drawing which shows (a) the decomposition | disassembly cross-section structure and (b) the cross-section structure in the assembly state about the conventional engine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine, 12, 24, 30, 40 ... Cylinder block, 13, 21 ... Gasket, 14, 33 ... Cylinder head, 15 ... Piston, 15a ... Piston ring, 16, 25, 32 ... Cylinder bore, 17, 23, 29 ... Water jacket, 18, 27, 31 ... Bore wall, 18a, 27a, 31a ... Thin wall part, 18b ... Upper end face of bore wall, 22 ... Outer peripheral wall, 22a ... Upper end face of outer peripheral wall, 33a ... Convex part, A ... The sliding range of the piston ring.

Claims (6)

In a cylinder block in which a water jacket is formed around a cylinder bore in which a piston is reciprocated,
In the bore wall between the cylinder bore and the water jacket, the wall surface is recessed in a position lower than the sliding range of the piston ring, so that the bore wall is compared with the sliding range. A cylinder block characterized by forming a thin wall portion with a reduced thickness. 2. The cylinder block according to claim 1, wherein a thickness of the bore wall in the sliding range is constant. The cylinder block according to claim 1 or 2, wherein the water jacket is set to have a depth up to a lower end portion of the cylinder bore. The cylinder block according to any one of claims 1 to 3, wherein the thin portion is formed by recessing a wall surface of the bore wall on the water jacket side in a concave shape. The cylinder block according to any one of claims 1 to 4, wherein an upper end of the bore wall protrudes above an upper end of an outer peripheral wall of the water jacket. In an engine formed by assembling a cylinder block, in which a water jacket is formed around a cylinder bore where a piston is reciprocated, to a cylinder head,
Compared to the sliding range, the wall surface of the cylinder block between the cylinder bore and the water jacket is recessed below the sliding range of the piston ring in the bore wall of the cylinder block. While forming a thin wall portion with a reduced wall thickness of the bore wall,
An engine characterized in that a convex portion projecting toward the cylinder block from the other portion of the lower end surface is formed at a portion of the lower end surface of the cylinder head facing the upper end surface of the bore wall.

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