JPH04224264A - Construction of crankshaft for engine - Google Patents

Abstract

PURPOSE:To provide simple and low cost construction of crankshaft bearing of engine by preventing a cylinder liner from being deformed due to tightening of a cylinder head to a cylinder block and also preventing bearing caps from being deformed due to piston load. CONSTITUTION:In a construction of bearings J in which a crankshaft 22 is supported by bearings 23 and bearing caps 24 at the lower end of a cylinder block 2 formed by aluminum allay, cap fixing bolts 26 which are connected to the bearings 23 through caps 24 and head bolts 27 which are inserted from the cylinder head side through the cylinder block 2 and connected to the caps 24 for tightening the overall bearings together are provided. The head bolts 27 are provided at the outer side than the cap fixing bolts 26 as viewed in the lateral direction of an engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crank bearing structure for an engine.

0002

[Prior Art] Generally, in a conventional engine, a cylinder head is arranged on the upper surface of the cylinder block, and a head bolt is screwed into the cylinder block from the upper surface of the deck portion of the cylinder head downward through the cylinder head. The cylinder head and cylinder block are fastened together.

[0003] Furthermore, in such conventional engines,
A crank whose crankshaft consists of a bearing part formed at the lower end of the cylinder block, a bearing cap attached to the lower surface of the bearing part, and a bearing arranged between the bearing part and the bearing cap and in direct sliding contact with the crankshaft. It is rotatably supported by bearings. Then, the bearing cap fastening bolt is screwed upward into the bearing part from the bottom surface of the bearing cap.
This allows the bearing cap to be fastened to the bearing portion of the cylinder block (see, for example, Japanese Utility Model Publication No. 163948/1983).

0004

[Problems to be Solved by the Invention] In recent years, there has been a demand for lighter engines, and efforts have been made to use aluminum alloys for cylinder blocks, which were conventionally mainly made of cast iron. However, aluminum alloy has low rigidity at high temperatures, so if the cylinder block is made of aluminum alloy, the rigidity of the cylinder block will decrease, and the cylinder liner will deform due to the tightening force of the head bolts screwed around the cylinder liner. There are problems that arise. Note that such deformation occurs especially on the exhaust side (high temperature side) of the cylinder liner.
It tends to occur in the areas of

Furthermore, as shown in FIG. 2, a crankshaft 10
1 is rotatably supported by a crank bearing having a bearing portion 102 of the cylinder block and a bearing cap 103, and the bearing cap 103 is connected to the bearing portion 102 by two bearing cap fastening bolts 104.
In the conventional crank bearing structure in which the bearing cap 103 is fastened to the
Deformation occurs in the upper part of the crankshaft 101 in the direction of the double arrow P, opening in the radial direction of the crankshaft 101. As a result, the crankshaft 101
There are problems such as vibration and engine noise.

On the other hand, in addition to the ordinary bearing cap fastening bolts shown in FIG. 2, bolts that fasten the bearing cap to the cylinder block from the side are used to firmly fasten the bearing cap to the cylinder block. Possible countermeasures include preventing deformation due to piston load. However, if this is done, there is a problem that the shape of the bearing cap becomes complicated and the manufacturing cost increases.

The present invention has been made to solve the above-mentioned conventional problems, and is capable of preventing deformation of the cylinder liner due to the fastening of the cylinder head to the cylinder block, and also prevents deformation of the cylinder liner due to the piston load. An object of the present invention is to provide a simple and inexpensive engine crank bearing structure that can prevent deformation of the engine.

[0008]

[Means for Solving the Problems] In order to achieve the above object, a first invention provides a crankshaft with a bearing portion formed at the lower end of a cylinder block, and a bearing cap attached to the lower end surface of the bearing portion. In an engine crank bearing structure that rotatably supports a shaft, a bearing cap fastening bolt is fastened to the bearing part from the bottom surface of the bearing cap through the bearing cap, and a bolt is fastened to the bearing part from the cylinder head side through the cylinder head and cylinder block. To provide a crank bearing structure for an engine, characterized in that a head bolt is fastened to a bearing cap and fastens a cylinder head, a cylinder block, and a bearing cap together.

[0009] A second invention provides an engine crank bearing structure according to the first invention, characterized in that the cylinder block is formed of an aluminum alloy.

[0010] A third invention is characterized in that in the engine crank bearing structure according to the first invention, the head bolt is fastened to the bearing cap on the outside of the bearing cap fastening bolt when viewed in the engine width direction. We provide crank bearing structures for engines that

[0011]

[Examples] Examples of the present invention will be explained in detail below. As shown in FIG. 1, a cylinder head 1 of an engine CE is arranged on the upper surface of a cylinder block 2 made of aluminum alloy, and a cylinder head cover 3 is provided on the upper surface of the cylinder head 1.
is installed. Further, an oil pan 5 is attached to the lower surface of the cylinder block 2 via an upper block 4.

When the intake valve 6 is opened, the engine CE sucks the air-fuel mixture into the combustion chamber 8 from the intake port 7, compresses this air-fuel mixture with the piston 9, and fires the spark plug (not shown). ignition and combustion, and when the exhaust valve 10 is opened, the combustion gas is discharged to the exhaust port 11. Note that the intake port 7 is connected to an intake passage 12 and the exhaust port 11 is connected to an exhaust passage 13. Here, the intake valve 6 is connected to the intake valve cam 1 attached to the intake valve camshaft 15 via the intake valve HLA 14.
6, it is opened and closed at a predetermined timing. Further, the exhaust valve 10 is opened and closed at predetermined timing by an exhaust valve cam 19 attached to an exhaust valve camshaft 18 via an exhaust valve HLA 17.

Due to the combustion pressure of the air-fuel mixture, the piston 9 reciprocates in the axial direction (up and down direction) of the cylinder liner 20, and this reciprocating movement of the piston 9 is caused by the connection between the connecting rod 21 and the crank pin (not shown). The rotational motion is converted into a rotational motion and transmitted to the crankshaft 22.

Here, the crankshaft 22 includes a bearing portion 23 formed at the lower end of the cylinder block 2, and a bearing portion 23 formed at the lower end of the cylinder block 2.
3, a bearing cap 24 attached to the lower surface of the
Bearings 25a and 25b are arranged between the bearing portion 23 and the bearing cap 24 and are in direct sliding contact with the crankshaft 22.
It is rotatably supported by a crank bearing J consisting of.

The bearing cap 24 is fastened to the bearing portion 23 using two bearing cap fastening bolts 26. Here, each bearing cap fastening bolt 26 passes upward from the lower surface of the bearing cap 24 and is screwed into the bearing portion 23 in the vicinity of the crankshaft 22 when viewed in the engine width direction (left and right direction in FIG. 1). ing. This bearing cap fastening bolt 2
6, sufficient vertical connection rigidity between the bearing cap 24 and the bearing portion 23 is ensured. Note that since the bearing cap fastening bolt 26 is disposed near the crankshaft 22, the crankshaft 22 can be reliably supported against a strong downward explosive load applied to the crankshaft 22.

By the way, the cylinder head 1, cylinder block 2, and bearing cap 24 are fastened together using two head bolts 27, thereby fixing the cylinder head 1 to the upper surface of the cylinder block 2. Each head bolt 27 passes downward through the cylinder head 1 and cylinder block 2 from the upper surface of the deck portion of the cylinder head 1, and is screwed into the bearing cap 24. Here, each head bolt 27 is screwed into the bearing cap 24 on the outside of the bearing cap fastening bolt 26 when viewed in the engine width direction (left and right direction in FIG. 1), that is, near both ends in the engine width direction. In this way, both ends of the bearing cap 24 are firmly fixed to the cylinder block 2 by the head bolts 27, so that the rigidity of the bearing cap 24 in the crankshaft radial direction is increased. Therefore, even if a piston load acts on the bearing cap 24, the upper part of the bearing cap 24 is deformed in the radial direction of the crankshaft as explained in the "Problems to be Solved by the Invention" of this application (see FIG. 2). is prevented and engine noise is reduced.

Further, each head bolt 27 only passes through the cylinder block 2 downward, and is not screwed into the cylinder block 2. Therefore, the cylinder head 1 and the cylinder block 2 are only fixed by the surface pressure of their contact surfaces, and the tightening force of the head bolts 27 does not act on the cylinder block 2. For this reason,
Even though the cylinder block 2 is made of an aluminum alloy with relatively low rigidity, the cylinder liner 20 does not deform. Therefore, deformation of the cylinder liner 20 can be prevented while reducing the weight of the engine CE.

[0018]

According to the first aspect of the invention, the bearing cap fastening bolt ensures sufficient vertical connection rigidity of the bearing cap to the cylinder block. The bearing cap is firmly fixed to the cylinder block by the head bolt, increasing the rigidity of the bearing cap in the radial direction of the crankshaft, thereby preventing deformation of the upper part of the bearing cap in the radial direction of the crankshaft due to the piston load. Further, since the head bolt is not screwed into the cylinder block, and therefore the tightening force of the head bolt does not act on the cylinder block, deformation of the cylinder liner is prevented.

According to the second invention, basically the same operation and effect as the first invention can be obtained. Furthermore, even though the cylinder block is made of an aluminum alloy with relatively low rigidity, the cylinder block is not subjected to the tightening force of the head bolts, so deformation of the cylinder liner is prevented. Therefore, the weight of the engine is reduced and deformation of the cylinder liner is prevented.

According to the third invention, basically the same operation and effect as the first invention can be obtained. Furthermore, since the bearing cap fastening bolt is arranged near the crankshaft, the crankshaft can be reliably supported against explosive loads. Furthermore, since the head bolt is screwed into the bearing cap near both ends in the engine width direction,
Deformation of the bearing cap in the crankshaft radial direction is more reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is an explanatory partial cross-sectional elevation view of an engine equipped with a crank bearing structure according to the present invention.

FIG. 2 is an elevational view of a conventional bearing cap attached to a cylinder block.

[Explanation of symbols]

CE...Engine J...Crank bearing 1...Cylinder head 2...Cylinder block 20...Cylinder liner 22...Crankshaft 23...Bearing part 24...Bearing cap 26...Bearing cap fastening bolt 27...Head bolt

Claims (3)

[Claims] 1. An engine crank bearing structure in which a crankshaft is rotatably supported by a bearing formed at a lower end of a cylinder block and a bearing cap attached to a lower end surface of the bearing, A bearing cap fastening bolt is fastened to the bearing part from the bottom of the bearing cap through the bearing cap, and a bolt is fastened to the bearing cap from the cylinder head side by passing through the cylinder head and cylinder block and connects the cylinder head, cylinder block, and bearing cap together. An engine crank bearing structure characterized by having a head bolt for tightening. 2. The engine crank bearing structure according to claim 1, wherein the cylinder block is made of an aluminum alloy. 3. The engine crank bearing structure according to claim 1, wherein the head bolt is fastened to the bearing cap on the outside of the bearing cap fastening bolt when viewed in the engine width direction. structure.