JP2006183520A - Engine seal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of an engine by simplifying a seal structure for preventing leakage of combustion gas.
An annular housing groove 41 is formed in a cylinder block 15 so as to surround a cylinder bore 42, and an annular housing groove 44 is formed in the cylinder head 20 so as to face the housing groove 41. The seal ring 46 accommodated in the accommodating grooves 41 and 44 between the cylinder block 15 and the cylinder head 20 is formed using iron having a smaller linear thermal expansion coefficient than the aluminum alloy forming the cylinder block 15 and the cylinder head 20. Therefore, the seal ring 46 can be brought into tight contact with the cylinder block 15 and the cylinder head 20 as the engine temperature rises, and combustion gas leakage can be prevented by the low-cost seal ring 46 having a simple structure. It becomes possible.
[Selection] Figure 3

Description

  The present invention relates to an engine seal structure for preventing leakage of combustion gas from a combustion chamber.

  A cylinder head having a valve operating mechanism is assembled on an upper portion of a cylinder block that accommodates the piston so as to be able to reciprocate. A combustion chamber is defined by the piston, the cylinder block, and the cylinder head. When driving the engine, the piston is moved in the direction of bottom dead center to take in the air-fuel mixture into the combustion chamber, and then the piston is moved in the direction of top dead center to compress the air-fuel mixture in the combustion chamber. Then, by burning the compressed air-fuel mixture, the piston is pushed down by the combustion pressure and the crankshaft is rotated. As described above, since the engine is driven by the high-pressure combustion gas generated in the combustion chamber, it is necessary to prevent the combustion gas from being blown out in order to drive the engine normally, and between the cylinder block and the cylinder head. The head gasket is sandwiched.

As a basic structure of such a head gasket, a steel vest type in which a sheet material such as graphite is pasted on a core material formed by a thin steel plate, or a sheet material such as graphite is sandwiched between thin steel plates. There is a sandwich type. In addition, there is a metal gasket or the like in which an iron plate or a stainless steel plate is used in a single layer state or a laminated state in order to improve the mechanical strength as the pressure of the combustion gas increases (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-182341

  However, in the above-described head gasket, it is necessary to form a bead that maintains a high surface pressure applied to the head gasket, or to form a grommet portion so as to surround the cylinder bore to prevent the combustion gas from being blown out. Therefore, the manufacturing cost of the head gasket tends to increase, which has been a factor in raising the manufacturing cost of the engine. In addition, many of the above-described head gaskets cannot be reused when disassembling and servicing the engine, which increases the running cost.

  An object of the present invention is to reduce the manufacturing cost of an engine by simplifying a seal structure that prevents leakage of combustion gas.

  The engine seal structure according to the present invention is an engine seal structure including a cylinder body that reciprocally accommodates a piston, and a cylinder head that is assembled to an end surface of the cylinder body to define a combustion chamber. An annular first housing groove is formed on the end surface of the cylinder body so as to surround the cylinder bore that houses the cylinder bore, and an annular second housing groove is formed on the end surface of the cylinder head so as to face the first housing groove. An annular seal member is accommodated in the accommodation chamber formed by the first and second accommodation grooves, and a metal material having a different linear thermal expansion coefficient is used for the metal material forming the cylinder body and the cylinder head. Forming the seal member.

  The engine seal structure of the present invention is characterized in that the seal member is formed using a metal material having a smaller linear thermal expansion coefficient than the metal material forming the cylinder body and the cylinder head.

  According to the present invention, an annular seal member is sandwiched between a cylinder body and a cylinder head each having a receiving groove, and a metal having a different linear thermal expansion coefficient with respect to the metal material forming the cylinder body and the cylinder head. Since the seal member is formed using the material, the airtight state of the combustion chamber can be reliably maintained as the engine temperature rises. That is, by utilizing the difference between the thermal expansion amount of the cylinder body and the cylinder head and the thermal expansion amount of the seal member, the seal member can be brought into close contact with the cylinder body and the cylinder head. As a result, it is possible to prevent combustion gas from leaking with a seal member having a very simple structure without using a conventional head gasket having a complicated shape, thereby reducing the manufacturing cost of the engine.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a four-cycle engine 10 (hereinafter referred to as an engine) having a seal structure according to an embodiment of the present invention. FIG. 2 is a sectional view schematically showing an intake / exhaust system of the engine 10. It is. The illustrated engine 10 is a general-purpose engine 10 used as a power source for a generator or a compressor.

  First, as shown in FIG. 1, the engine 10 includes a crankcase 12 that rotatably accommodates a crankshaft 11 and a cylinder 14 that reciprocally accommodates a piston 13. And a cylinder body, that is, a cylinder block 15. The crankshaft 11 that is rotatably accommodated in the crankcase 12 and the piston 13 that is reciprocally accommodated in the cylinder 14 are connected via a connecting rod 16, and the crankshaft 11 is reciprocated by the reciprocating motion of the piston 13. Is to be rotated. Lubricating oil L is stored in the crankcase 12, and the lubricating oil L is scraped up by an oil dipper 17 provided on the connecting rod 16, and is supplied to each sliding portion in the engine 10. It is like that.

  As shown in FIG. 2, a cylinder head 20 including a valve operating device is assembled to the upper end surface of the cylinder block 15, and a combustion chamber 21 is defined by the cylinder head 20, the cylinder block 15, and the piston 13. The cylinder head 20 is formed with an intake port 22 that supplies an air-fuel mixture to the combustion chamber 21 and an exhaust port 23 that discharges the combustion gas. An intake valve 24 that opens and closes the intake port 22 and an exhaust port 23 are provided. An exhaust valve 25 that opens and closes is assembled so as to be openable and closable. Further, in order to open and close the intake valve 24 and the exhaust valve 25, a cam shaft 26 having a cam 26a is rotatably mounted on the cylinder head 20. When the cylinder head 20 is assembled to the cylinder block 15, it is tightened via a head bolt (not shown).

  An intake side rocker arm 28 that opens and closes the intake valve 24 and an exhaust side rocker arm 29 that opens and closes the exhaust valve 25 swing on the rocker shaft 27 that is mounted on the cylinder head 20 in parallel with the cam shaft 26. Mounted freely. Further, a timing chain 32 for transmitting the rotation of the crankshaft 11 to the camshaft 26 is stretched between the crank sprocket 30 fixed to the crankshaft 11 and the cam sprocket 31 fixed to the camshaft 26. The intake valve 24 and the exhaust valve 25 are opened and closed at an appropriate timing in synchronization with the crank angle.

  As shown in FIG. 1, an engine cover 35 is attached to the side of the crankcase 12, and a cooling fan 36 connected to the crankshaft 11 is accommodated in the engine cover 35. The cooling air generated by the engine is blown along the engine cover 35 to the crankcase 12, the cylinder 14, or the like. Further, a recoil mechanism 37 is provided adjacent to the cooling fan 36, and the recoil mechanism 37 is connected to the crankshaft 11 via a clutch mechanism (not shown). When starting the engine 10, the operator can start and rotate the crankshaft 11 by pulling the recoil lever 38 of the recoil mechanism 37.

  Subsequently, the seal structure of the combustion chamber 21 will be described. FIG. 3 is an exploded perspective view showing an assembled state of the cylinder block 15 and the cylinder head 20. Note that the cylinder head 20 shown in FIG. 3 is shown in a state of being inverted in the vertical direction for easy understanding. As shown in FIG. 3, an annular first housing groove 41 is formed in the upper end surface 40 of the cylinder block 15, and a cylinder bore 42 that houses the piston 13 is surrounded by the housing groove 41. An annular second receiving groove 44 is formed on the lower end surface 43 of the cylinder head 20 so as to face the receiving groove 41 of the cylinder block 15. In the receiving grooves 41 and 44 formed in the cylinder block 15 and the cylinder head 20, a seal ring 46 that is an annular seal member is received. The cylinder block 15 and the cylinder head 20 are formed using an aluminum alloy, while the seal ring 46 is formed using iron having a smaller linear thermal expansion coefficient than the aluminum alloy.

  4A is a sectional view showing the seal structure of the combustion chamber 21 in the range A of FIG. 1, and FIG. 4B is an explanatory view showing the expanded state of the cylinder block 15, the cylinder head 20, and the seal ring 46. FIG. is there. As shown in FIG. 4A, the seal ring 46 has a rectangular cross-sectional shape, and is housed in close contact with the housing chamber 45 formed by the pair of housing grooves 41 and 44. When the engine 10 having such a seal structure is started, each member constituting the engine 10 expands as the temperature rises. That is, as shown in FIG. 4B, each of the cylinder block 15, the cylinder head 20, and the seal ring 46 expands radially outward, but is formed using an aluminum alloy. Since the thermal expansion amount (arrow b) of the seal ring 46 formed using iron having a small linear thermal expansion coefficient is smaller than the thermal expansion amount (arrow a) of the cylinder block 15 and the cylinder head 20, the cylinder block 15 The cylinder head 20 pushes the seal ring 46 outward in the radial direction.

  That is, by utilizing the difference in the linear thermal expansion coefficient of the metal material, the surface pressure applied to the inner peripheral surface 46a of the seal ring 46 as the temperature of the engine 10 rises can be increased. The airtight state of the combustion chamber 21 can be maintained by the seal ring 46 that is in close contact with the fuel cell 20. In this way, since the leakage of combustion gas can be prevented by the seal ring 46 having a very simple structure without using a conventional head gasket having a complicated shape, the manufacturing cost of the engine 10 can be reduced. Become. Further, by using the iron seal ring 46 as a head gasket, the mechanical strength and sag resistance of the head gasket can be remarkably improved. When the engine 10 is disassembled and maintained, the head gasket, that is, the seal ring 46 is used. It can be reused. In addition, when the cylinder head 20 is assembled to the cylinder block 15, the cylinder head 20 can be positioned by the seal ring 46 protruding from the upper end surface 40 of the cylinder block 15. Therefore, the cylinder block 15 and the cylinder head 20 are positioned. It is also possible to reduce the number of knock pins.

  Next, FIGS. 5A to 5C are cross-sectional views showing a seal structure according to another embodiment of the present invention. 5 (A) to 5 (C) show the same parts as those shown in FIG. 4 (A), and the same members as those in FIG. 4 (A) are denoted by the same reference numerals. The description is omitted. First, as shown in FIG. 5A, a plurality of grooves 50b may be formed on the inner peripheral surface 50a of the seal ring 50. By forming such a groove 50b, the contact area of the seal ring 50 with respect to the cylinder block 15 and the cylinder head 20 can be reduced, so that the surface pressure applied to the inner peripheral surface 50a of the seal ring 50 can be increased. It is possible to improve the airtight performance of the seal structure. Further, as shown in FIG. 5B, when the annular lip portions 52a and 52b are formed on both end faces 51a and 51b of the seal ring 51, both end faces 51a and 51b of the seal ring 51 are tightened by tightening the head bolts. It is possible to increase the surface pressure applied to the seal structure and improve the airtight performance of the seal structure. Further, as shown in FIG. 5C, the gas chamber 55 may be formed outside the seal ring 46 by widening the width of the first and second receiving grooves 53 and 54. By forming such a gas chamber 55, even if the combustion gas flows along the inner peripheral surface 46 a of the seal ring 46 in the cold state immediately after the engine is started, the flowing combustion gas is transferred to the gas chamber 55. It can be stored.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the illustrated engine 10 is a four-cycle engine having a valve operating mechanism, but is not limited to this. Even a two-cycle engine in which an intake port and an exhaust port are formed in a cylinder bore is not limited to this. The seal structure of the invention can be effectively applied.

  Needless to say, the cylinder block 15 and the cylinder head 20 may be formed using a metal material other than an aluminum alloy, and the seal ring 46 may be formed using a metal material other than iron.

It is sectional drawing which shows the 4-cycle engine provided with the seal structure which is one embodiment of this invention. 1 is a cross-sectional view schematically showing an intake / exhaust system of an engine. It is a disassembled perspective view which shows the assembly | attachment state of a cylinder block and a cylinder head. (A) is sectional drawing which shows the seal structure of a combustion chamber in the range A of FIG. 1, (B) is explanatory drawing which shows the expansion state of a cylinder block, a cylinder head, and a seal ring. (A)-(C) are sectional drawings which show the seal structure which is other embodiment of this invention.

Explanation of symbols

10 Engine 13 Piston 15 Cylinder block (Cylinder body)
20 Cylinder head 21 Combustion chamber 40 Upper end surface (end surface)
41 receiving groove (first receiving groove)
42 Cylinder bore 43 Lower end face (end face)
44 Accommodation groove (second accommodation groove)
45 Storage chamber 46 Seal ring (seal member)
50 Seal ring (seal member)
51 Seal ring (seal member)
53 receiving groove (first receiving groove)
54 Accommodation groove (second accommodation groove)

Claims (2)

An engine seal structure comprising: a cylinder body that reciprocally accommodates a piston; and a cylinder head that is assembled to an end surface of the cylinder body to define a combustion chamber;
An annular first receiving groove is formed on the end surface of the cylinder body so as to surround the cylinder bore that houses the piston,
Forming an annular second accommodation groove on the end surface of the cylinder head so as to face the first accommodation groove;
An annular seal member is accommodated in the accommodation chamber formed by the first and second accommodation grooves,
A seal structure for an engine, wherein the seal member is formed using a metal material having a different linear thermal expansion coefficient with respect to a metal material forming the cylinder body and the cylinder head.   The engine seal structure according to claim 1, wherein the seal member is formed using a metal material having a smaller linear thermal expansion coefficient than the metal material forming the cylinder body and the cylinder head. Seal structure.

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