JPS58134216A - Cam shaft bearing structure for internal-combustion engine - Google Patents

Abstract

PURPOSE:To ensure the axial flatness of the bearing face when fastening a cylinder head to a cylinder block, by inclining the opposite side to the cylinder block fastening side of a lower cam holder of a cam shaft to the cylinder head side. CONSTITUTION:Since it is fastened to a cylinder block through bolts 15, 151 provided in front and rear of the inside A near to space S of a lower cam holder 16, the inside A is pressed downward while the outside B will deform upward because it is not fastened directly to the cylinder block through bolts. Said upward deformation is absorbed because the downwardly inclined face c is formed at the outside of the lower cam holder 16, thereby the outside B will be a flat face where the inside A and the bottom are continuous in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camshaft bearing structure for an OHC type (overhead camshaft type) internal combustion engine.

The camshaft of an OHC type internal combustion engine is supported between a lower bearing and an upper bearing on the cylinder head side. It takes O
In an HC internal combustion engine, if a common camshaft is installed between the parallel cylinder openings and the cylinder heads, and the camshaft is driven by a transmission mechanism such as a sprocket or chain drive installed in the middle, the center of the cylinder head Since it is necessary to provide a space for the transmission mechanism such as a cam chain chamber in the head, the wall thickness around the space in the head becomes thinner, and there is a risk that the rigidity will be relatively reduced. In particular, modern internal combustion engines use light alloys such as aluminum alloys due to the need for weight reduction, and when the cylinder head is connected to the cylinder block with multiple bolts, the tightening load of these bolts can cause some deformation. There is a risk that this will occur in the low-rigidity part of the cavity, and such deformation will spread to the lower bearing of the camshaft installed on the cylinder head. When tightened in that direction, it deforms in the direction of the camshaft. Microscopically, this single camshaft is supported in an arched shape, which is undesirable.

In order to solve the above problem, increasing the wall thickness of the cylinder head to prevent such deformation may be considered, but this would increase the weight of the cylinder head, leading to an increase in the weight of the entire internal combustion engine. This would be against the request.

The present invention has been made to improve the above-mentioned problems, and the object thereof is to provide a lower bearing of a camshaft provided on a cylinder head, in which the other side of the bearing in the axial direction is opposite to the cylinder block tightening side. The inclination of the part far from the tightening side of the bearing absorbs the deformation of this side during tightening, and when the cylinder head is tightened to the cylinder block, the above inclination causes the bearing surface to move in the axial direction. The flatness of the camshaft is ensured, the camshaft is supported without bending, and this is achieved without reinforcing or increasing the rigidity of the bearing or cylinder head by increasing the wall thickness, thereby reducing the weight of the cylinder head. An object of the present invention is to provide a camshaft bearing structure for an internal combustion engine that smoothly supports a camshaft.

□ Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional front view of an internal combustion engine, and in this embodiment, the internal combustion engine is of a varnished cylinder type with cylinders arranged side by side on the left and right sides, and is of the DOHC type.

The internal combustion engine 1 has two cylinder blocks 2.2 arranged in parallel.
Each block is supported by a crankcase (not shown) with a binding plate, and each piston 3 is slidably inserted into the block 2.2, and cylinder heads 4, 4 are connected to the top of the block 2.2. A camshaft 5 is horizontally mounted on the heads 4, 4 in the front and rear, and the camshaft 5 is connected to the left and right heads 4, 4.
The camshafts 5 are mounted horizontally in the left and right direction so as to rest on top of each camshaft, and have two camshafts in the front and back for intake and exhaust, respectively. 6' and a chain 77 wound around it,
In the figure, 8 is an upper cam holder forming an upper bearing of the camshaft, and 9 is a cylinder head cover.

The cylinder head 4.4 is composed of a cylinder head block 10, the details of which are shown in FIG. 2, and the left and right cylinder heads 4.4 are integrally cast as a cylinder lock 10. The block 1o has a surrounding frame 1 on the heads 4, 4.
1, and a storage space S for a cam chain 7 passing through in the vertical direction is provided between the heads 4.4 within the surrounding frame 11, and the heads 4.4 face the left and right sides of the center space S. At the front and back of each outer side of the heads 4.4, binding bosses 12 are provided at four locations in total, and at the front and rear of the opposing inside sides of the heads 4, 4, binding bosses are also provided at the portions close to the empty space S. 13 are provided at four locations, and binding boss portions 14 are provided on the left and right outside the front and rear ends of the space S.
... are provided at four locations in total, and these 12 binding boss portions 12, 13. ...and Porto 15 and H binding boss part 1
4, the cylinder head block 10 is screwed and fastened to the cylinder block 2 by bolts 151.

In front and behind the cylinder head 4.4 of the cylinder head block 10, lower cam holders 16, which serve as lower bearings for the camshafts, are provided on the left and right sides inside the center of the cylinder head, and the cam holders 16 are semicircles that open upward. It has a concave shape, and both ends are open to the left and right, that is, in the axial direction of the camshaft 5. In addition, in the lower cam holder 16 main body, the support part 21 of the intake/exhaust valve and the lower cam holder 16 are arranged close to each other in order to shorten the width direction of the engine, and the camshaft 5 is cantilever-supported by the lower cam holder 16, so that the axis of the lower cam holder 16 is The length in the direction is required, and as shown in the figure, it forms a square shape. As shown in the figure, the intake and exhaust valve holding parts 21 are varnished cylinders made of four pulps per cylinder, so four of them are provided in each cylinder head 4, 4. At the front and back of the cylinder head 4° 4 and outward from the center are provided recesses Sl for storing the pulp rocker arms (not shown), and specifically, they are provided at the four corners of the surrounding frame 11.

The above-mentioned parts including the lower cam holder are entirely cast as one piece, and the lower cam holders 16 are arranged symmetrically in the axial direction, and in the embodiment, a lubricating oil groove 17 that is long in the axial direction is formed in the bottom of each of the lower cam holders 16 . The inner side A in the axial direction from the center of the concave surface 18 of the holder 16... has a flat bottom in the axial direction, and the outer side B in the axial direction from the center has the bottom in the cylinder head 4 direction with respect to the axial direction, i.e. Tilt C downward. The amount of inclination is approximately equal to the amount of deformation when the cylinder head block 10 is connected, and the outer end B of the outer side B is lowered in the axial direction with respect to the inner side A by about 25μ with respect to the extension line inward. It is tilted from the center, and the tilt angle θ is determined as appropriate.

In the figure, reference numeral 19 denotes a chain tensioner, which is fixed to boss portions 20 provided on the left and right sides of the intermediate portions of the cylinder heads 4, 40 in the longitudinal direction.

Between the left and right lower cam holders 16, that is, 16-
1 and 16-2. Camshaft 5 between 16-3 and 16-4
Horizontally hang the cam holder 8 on top of each cam holder.
The camshaft 5, which is horizontally suspended in the front and rear, is rotatably supported. Since the upper cam holder 8 supports the camshaft 5 in a cantilever manner with the lower cam holder 16, it supports the upper surface of the camshaft in order to receive the reaction force accompanying the opening and closing of the intake and exhaust valves. It has a support 81 extended to . In addition, i22'+' in the figure
zAtsuba Kamho・□・11 Lubricating oil retaining groove formed on the concave surface of the bearing of the cylinder, 23 is the oil passage provided on the camshaft, 24 is the cylinder head cover 9
The mounting bolt 25 is a rocker arm shaft.

Next, to explain its functions and effects in detail, the lower kamuho ruda 1
The front and back of the inside near the empty space S of 6 are boss parts 13..., 14
Since it is connected to the cylinder block with bolts 15..., 151 through Since B is far from the binding part and there is a recess Sl on this side, and it is not directly connected to the cylinder block side with bolts, it deforms slightly upward, and this upward deformation is caused by the downward slope surface mentioned above. Since C is formed on the outside, it is absorbed, and when the cylinder head block 10 is assembled, the outside B becomes a flat surface where the inside A and its bottom are continuous in the axial direction, and therefore, due to the upward deformation of the outside, the camshaft No load is applied to cause the camshaft 7 to deform into an upward arch, and the camshaft 7 is supported by the lower cam holder which is flat in the axial direction. Therefore, smooth rotation of the camshaft is ensured, and uneven wear V of the bearings and camshaft is prevented. In the above, we took advantage of the deformation of the cylinder head block when it was tied together, provided an inclined part in the lower cam holder in anticipation of this, and corrected it by the deformation of the inclined part. There is no need to increase the strength and rigidity by increasing the wall thickness of the head (it is possible to reduce the thickness of the cylinder head without increasing the weight of the cylinder head, making it possible to reduce the weight of the cylinder head and improve the weight of internal combustion engines). The above can be achieved with a simple configuration of forming an inclined portion.

The present invention has many advantages as described above.

In the embodiment, the present invention is applied to a DOHC or OHC type internal combustion engine, but the type may be arbitrary, and the present invention can also be applied to a single cylinder type internal combustion engine.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a longitudinal sectional front view of an internal combustion engine, Fig. 2 is a plan view of the cylinder head taken along the line 2-2 in Fig. 1, and Figs. Enlarged cross-sectional view of the section,
FIG. 4 is a vertical sectional side view of the main part of the bolted joint. In the drawing, 4 is a cylinder head, 5 is a camshaft, and 8.
16 is a bearing, C is an inclined surface, and 13.14 is a binding portion. Patent applicant Honda Motor Co., Ltd.

Claims (1)

[Claims] The camshaft bearing half-rested in the cylinder head,
The camshaft is supported between this and a separate bearing half,
In an internal combustion engine in which the cylinder head is connected to the cylinder block at one axial direction of the bearing half on the cylinder head side, the other axial direction of the cylinder head side bearing half is connected in the radial direction of the camshaft. A camshaft bearing structure for an internal combustion engine characterized by being inclined outward.