JPH06346781A - Head block fixing structure for engine - Google Patents

Abstract

PURPOSE:To prevent ununiformity of fastening axial force of each fastening bolt during engine operation and to prevent plastic deformation of a head block and the like so as to improve a sealing performance of a gasket. CONSTITUTION:Aluminum alloy head block 4 is fixed to a cylinder block of an engine E by plural fastening bolts 5. Among these fastening bolts 5, fastening bolts 5b, which fasten a vicinity of an exhaust port 34, consist of thinner size bolts than fastening bolts 5a, which fasten other parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for fixing an aluminum alloy head block to a cylinder block of an engine, and more specifically, a structure for improving the sealing property of a gasket between the head block and the cylinder block. Regarding

[0002]

2. Description of the Related Art A cylinder block or a head block of an engine may use an aluminum alloy as a material in order to reduce the weight and improve the cooling performance. This aluminum alloy head block is fixed to the cylinder block with a plurality of fastening bolts arranged at appropriate intervals. Conventionally, the fastening bolts have the same thickness at all fastening portions. It was

[0003]

Since the conventional aluminum alloy head block has a coefficient of thermal expansion larger than that of the iron fastening bolt, when the engine is operated by combustion heat and expanded by the combustion heat, a tensile stress is applied to the fastening bolt. Axial force increases. In particular, the temperature in the vicinity of the exhaust port rises to 200 ° C., and the temperature becomes higher than that in the intake port side and expands greatly, so that the tightening axial force of the fastening bolt becomes stronger than other parts. As a result, the tightening axial force of each part due to the fastening bolt becomes non-uniform, and the tightening axial force of the fastening bolt becomes too large locally, which may cause plastic deformation of the aluminum alloy material such as the head block in this part. There are many.

When the material of the head block is plastically deformed, the flatness of the contact surface with the cylinder block is reduced, and when the engine is cooled due to engine stop or the like and heat contracts, the tightening axial force of the fastening bolt is significantly reduced. Therefore, there is a problem that the sealability of the gasket between the head block and the cylinder block deteriorates. The present invention solves these problems, prevents uneven tightening axial force of each fastening bolt during engine operation, prevents plastic deformation of the head block, etc., and improves gasket sealability. An object of the present invention is to provide an engine head block fixing structure.

[0005]

In order to achieve the above object, the present invention is characterized in that it is configured as follows. That is, in the engine head block fixing structure in which the aluminum alloy head block (4) is fixed to the cylinder block (2) of the engine (E) with a plurality of fastening bolts (5),
The fastening bolt (5a) for fastening the vicinity of the exhaust port (34) of the engine (E) is composed of a bolt having a smaller size than the fastening bolt (5b) for fastening the other portion.

[0006]

Since the fastening bolts in the vicinity of the exhaust port are thinner than the fastening bolts in other portions, even if the head block in this portion undergoes large thermal expansion as the engine operates, the fastening axial force of the fastening bolts The rise is kept low and not too large compared to other parts.

[0007]

Since the tightening axial force of the fastening bolts in the vicinity of the exhaust port does not become excessive, the tightening axial force of each fastening bolt during engine operation is maintained uniform throughout. Moreover,
Since the plastic deformation of the aluminum alloy material is less likely to occur, the flatness of the head block can be kept good, and
The tightening axial force of the fastening bolt does not drop significantly when the engine is cooled. As a result, the sealability of the gasket between the head block and the cylinder block can be maintained high.

[0008]

1 and 2 show an embodiment of the present invention, FIG. 1 is a vertical sectional front view of a vertical overhead valve engine, and FIG. 2 is a plan view showing a head block.

As shown in FIG. 1, the vertical overhead valve engine (E) has a crankcase (1) and a cylinder block (2).
Are integrally formed with an aluminum alloy, and an aluminum alloy head block (4) is fixed to the upper surface of the cylinder block (2) through a gasket (3) with fastening bolts (5). A head cover (6) is fixed to the upper surface of (4).

A cylinder is provided at the center of the cylinder block (2).
A piston (10) which forms (7) and is interlocked with the crankshaft (9) via a connecting rod (8) is internally slidably fitted therein. An oil scraping spoon (12) is connected to the large end (11) of the connecting rod (8), and an oil pan (1) is provided below the crankcase (1).
Lubricating oil stored in 3) is agitated with this spoon (12) and the lubricating oil is lubricated with the splashed oil.

Intake / exhaust valve arranged in the head block (4)
(13) are arranged so as to be inclined with respect to the axis of the cylinder (7), and the rocker arm (14) is arranged at the input end (15) and the crank chamber (16) in the crankcase (1). The valve operating cam (17) is connected via a push rod (18). The rocker arm chamber (19) is formed by a head cover (6) fixed to the head block (4) in a state of covering the rocker arm (14) from the upper side and an upper surface of the head block (4), and the lower surface thereof is on the push rod (18) side. It is formed in an inclined shape that becomes lower as it goes to.

A breather device (20) is provided on the side of the rocker arm chamber (19), and the breather device (20) has a box-shaped upper part of the head block (4) to form an inflow chamber (20). 21), one side of the head cover (6) is also formed into a box shape to form a breather chamber (22), and the inflow chamber (21) and the breather chamber (22) are partitioned by a breather plate (23), A reed valve (24) is provided on the breather chamber (22) side of the plate (23).

A fuel tank (25) is provided above the head cover (6).
Is provided and is fixedly supported by the stay (26). A lubricating oil replenishment tank (27) is installed inside this fuel tank (25) and the on-off valve
Crankcase (1) through the lubricating oil passage (29) with (28)
Connect to the oil pan (30) inside. This lubricating oil refill tank
The same amount of lubricating oil as the amount of lubricating oil between the upper limit and the lower limit of the lubricating oil surface in the oil pan (30) is accommodated in (27).

On the other hand, the oil surface detecting tool (31) is provided at the lower limit position (L) of the lubricating oil surface on the oil pan (30), and the lubricating oil surface inside the oil pan (30) is located below the lower limit position (L). When it also detects that the valve has dropped, the control device (32) gives an alarm and opens / closes the valve.
The valve (28) is opened to supply the entire amount of the lubricating oil in the lubricating oil replenishment tank (27) into the oil pan (30).

Generally, in an engine mounted on a work machine, if the surrounding space, that is, the engine room is small and the lubricating oil supply port is provided directly on the crankcase, it is difficult to supply oil. For this reason, it is common to replenish the lubricating oil from the oil supply port in the upper part of the engine while performing the oil detection with the oil detection rod placed in the oil detection pipe. However, in order to make the engine room compact, it is desired to omit the oil detecting pipe, and it is difficult to replenish the lubricating oil while the oil is being detected.

Since this embodiment is constructed as described above, when the oil level in the oil pan (30) reaches the lower limit position (L), an appropriate amount of lubricating oil up to the upper limit position is added to the lubricating oil replenishment tank (27). )
Since the oil can be replenished from above, it is not necessary to perform oil inspection or lubrication oil replenishment until the level of the lubricating oil reaches the lower limit, and the oil detection operation at the time of replenishment is also unnecessary, and the lubrication oil can be replenished with an extremely simple operation. The opening operation of the on-off valve (28) may be manually performed by an operator based on an alarm.

As shown in FIG. 2, the head block (4) of this engine is arranged around the cylinder 5 in plan view.
It is fixed to the cylinder block (2) by a fastening bolt (5). Among these five fastening bolts (5), M10 size fastening bolts (5a) are used on the intake port (33) side and the like, but in the vicinity of the exhaust port (34), it is thinner than this. M8 size fastening bolts (5b) are used.

In this way, the exhaust port (3
4) Connect the fastening bolts (5b) in the vicinity to the fastening bolts (5a) in other parts.
Even if a high tensile stress is applied to the fastening bolt (5b) in this part by thermal expansion by making it thinner than this, the tightening axial force that increases due to this is much smaller than when using an M10 size bolt. . As a result, even when the engine (E) is in operation, the tightening axial force of the fastening bolts (5b) in the vicinity of the exhaust port (34) does not become excessive, and the tightening axial forces of the fastening bolts (5) are totally. Since the aluminum alloy material is uniformly maintained and plastic deformation of the aluminum alloy material is unlikely to occur, the sealing property of the gasket (3) between the head block (4) and the cylinder block (2) is maintained high.

Although the vertical overhead valve engine has been described in the above embodiments, any type of engine may be used as long as it uses an aluminum alloy head block.
For example, it can be applied to a horizontal engine and a side valve engine.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a vertical overhead valve engine according to an embodiment of the present invention.

FIG. 2 is a plan view showing a head block of a vertical overhead valve engine.

[Explanation of symbols]

2 ... Cylinder block, 4 ... Head block, 5 ... Fastening bolt, 5a ... Fastening bolt for fastening near exhaust port,
5b ... Fastening bolts for fastening other parts, 6 ... Head cover, 34 ... Exhaust port, E ... Vertical overhead valve engine.

Claims (1)

[Claims] 1. A cylinder block (2) of an engine (E) having a head block (4) made of aluminum alloy and a plurality of fastening bolts.
In the structure for fixing the head block of the engine fixed by (5), the fastening bolt (5b) that fastens the vicinity of the exhaust port (34) of the engine (E) is thinner than the fastening bolt (5a) that fastens other parts. An engine head block fixing structure characterized by being composed of size bolts.