JPH0452404Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to the valve train structure of a SOHC engine.

(Prior art) In SOHC engines, the camshaft and two
The book locker shafts are arranged closely parallel to each other on the cylinder head. As one of the mounting structures for each of these shafts, for example, as disclosed in Japanese Utility Model Application Publication No. 59-157504, the camshaft is mounted so as to pass through the bearing hole of a bearing part integrally formed on the cylinder head side. On the other hand, it is known that the rocker shaft is fastened and fixed to the upper surface of the bearing portion using a mounting bolt. In this case, the width dimension of the bearing hole of the bearing part is approximately the same as the width dimension of the cam journal part of the camshaft so that the entire area of the cam journal part can be supported, and the width dimension of the bearing hole of the above-mentioned mounting bolt is The mounting position is usually set so that the mounting bolt is located approximately at the widthwise center of the bearing hole in the camshaft direction. In other words, the cam journal part, bearing part, and mounting bolt of the camshaft are overlapped with each other in the camshaft direction.

However, in such a structure, the camshaft and rocker shaft are generally installed close to each other, so when the mounting bolt is tightened,
Inevitably, the tip of the mounting bolt will be close to the inner peripheral surface of the bearing hole, and in some cases, the tightening force of the mounting bolt may cause the tip of the mounting bolt to become close to the inner peripheral surface of the bearing hole. There was a problem in that the part corresponding to the camshaft bulged inward (see reference numeral 51 in Fig. 2), which impaired the roundness of the bearing hole and made it easier for the camshaft to seize. .

(Purpose of the invention) The present invention is an attempt to solve the problems pointed out in the above-mentioned section of the prior art. It will be installed
The purpose of this invention is to propose a valve train structure that can prevent seizure of the camshaft due to deformation of the bearing in a SOHC engine.

A bearing part that is integrally molded and has a bearing hole inside is provided in the upper part of the cylinder head, and a camshaft is disposed so as to pass through the bearing hole of the bearing part, and the cam of the camshaft is inserted through the bearing hole. While the journal part is rotatably supported, a rocker shaft, which is arranged parallel to the camshaft, is mounted on the upper part of the bearing part by means of a mounting bolt screwed into the bearing part and at a position close to the bearing hole. In the SOHC engine which is fixed by a camshaft, the cam journal portion of the camshaft and the mounting bolt are arranged eccentrically relative to the bearing portion in the axial direction thereof.

(Function) In the present invention, by the above means, the mounting bolt and the cam journal of the camshaft are arranged eccentrically in the axial direction with respect to the bearing.
Even if the part of the bearing hole corresponding to the mounting bolt bulges inward and loses its roundness to some extent by tightening the mounting bolt, this deformation will not extend to the part corresponding to the cam journal part. The effect is that the roundness in this portion is maintained well.

(Embodiment) Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. 1 and 2.

Fig. 1 shows a cylinder head portion of a four-cylinder intake two-valve SOHC engine for automobiles to which a valve train structure according to an embodiment of the present invention is applied, and in the figure, reference numeral 1 indicates the cylinder head. . In the center of the upper surface 1a of the cylinder head 1, five bearings 2, which will be described later, are arranged at equal intervals in the engine longitudinal direction (crankshaft direction).

As shown in FIGS. 1 and 2, the bearing portion 2 is integrally formed with the cylinder head 1 so as to protrude upward from the surface 1a of the cylinder head 1, and has a groove extending in the direction of the crankshaft approximately at the center thereof. An extending bearing hole 21 is provided therethrough. A camshaft 3, which will be described later, is rotatably attached to the cylinder head 1 by means of the five bearings 2, 2, . . . arranged in a row at predetermined intervals.

The camshaft 3 is provided with four cam groups 40 at predetermined intervals in the axial direction, each consisting of three cams: an exhaust valve driving cam 41 and two intake valve driving cams 42 and 43 located on both sides. cam group 40,
It is composed of a stepped shaft body having large diameter cam journal portions 31, 31, . . . formed on both sides of 40, respectively. This camshaft 3 is connected to the bearing hole 2 of each of the above-mentioned bearing parts 2, 2, which are coaxially arranged.
1, 21... from one side to the other side, and by rotatably supporting each cam journal part 31, 31... by each bearing hole 21, 21... It is attached to the cylinder head 1 side, but in that case, in order to apply the present invention in this embodiment, the width dimension and mutual pitch of the cam journal parts 31, 31... of the camshaft 3 are set as described later. In addition, each of the above-mentioned bearing parts 2, 2...
It is set relative to... That is, in this embodiment, first, the cam journal part 31 corresponding to the bearing part 2 located at the center in the axial direction is
This is constituted by a pair of left and right cam journal parts 31A and 31B that are formed separately and appropriately spaced in the axial direction, and each of the cam journal parts 31A and 31B is located on both sides in the width direction of the corresponding bearing hole 21. (In other words, in this bearing part 2, the bearing hole 21
The central part in the width direction is a play area that does not contribute to the shaft support function).

On the other hand, each cam journal part 31, 31... corresponding to each bearing part 2, 2... other than the bearing part 2 in the central part has its width measured by the width dimension of the bearing hole 21 of the bearing part 2. Moreover, in the assembled state, each cam journal part 31, 3
1... is configured to be supported biased toward one side in the width direction of each bearing hole 21, 21... (in other words, in the bearing hole 21 of each of these bearing portions 2, 2... (Only one side in the width direction contributes to the shaft support action, and the other side is a play part that does not contribute to the shaft support action.)

On the other hand, on both sides of the upper surface 2a of each of the bearing parts 2, 2..., a pair of left and right rocker shafts 4, which are arranged parallel to the camshaft 3, as shown in FIGS.
4 is installed. To attach the rocker shaft 4 to the bearing part 2, the rocker shaft 4 is held by a holding member 5.
This is done by fastening the mounting bolts 6 to the bearing portion 2 side via the mounting bolts 6. in this case,
Since these three shafts are arranged close to each other, when the rocker shaft 4 is tightened to the bearing part 2 side with the mounting bolt 6, the tip end 6a of the mounting bolt 6 touches the peripheral edge of the bearing hole 21. As a result, as shown by reference numeral 51 in FIG.
A part of the peripheral edge of the cam shaft 3 bulges inward, and the existence of this bulge deformed portion 51 impairs the roundness of the bearing hole 21, and in some cases, the sliding rotation of the camshaft 3 may be impaired. As mentioned above, there is a risk that this may be inhibited and lead to burn-in. Mounting bolt 6 like this
By adopting the mounting structure of the Rocker shaft 4,
Deformation of the bearing hole 21 due to the tightening of the mounting bolts as described above is unavoidable.

Therefore, in this embodiment, such deformation is performed in a portion of the bearing hole 21 that does not actually contribute to the supporting action of the camshaft 3, thereby reducing the deformation and deformation in the portion that actually contributes to the supporting action of the camshaft 3. Seizure of the camshaft 3 caused by this is prevented in advance. Specifically, as shown in Figure 1,
By applying the present invention, the mounting position of the mounting bolt 6 in each bearing part 2, 2 is set eccentrically in the axial direction with respect to the cam journal part 31 of the camshaft 3 (i.e., the play part of the bearing hole 21). It is set to .
Therefore, each of the mounting bolts 6, 6, . It will be screwed to a portion corresponding to section 32. Therefore, by tightening the mounting bolt 6, the bearing hole 21
Even if the part corresponding to the mounting bolt 6 is slightly deformed, the deformation does not extend to the supporting part of the cam journal part 31 of the camshaft 3, and the roundness of this part is maintained well. Seizure between the bearing part 2 and the bearing part 2 can be prevented in advance and reliably.

In this embodiment, especially in the bearing part 2 at the center in the axial direction, the two mounting bolts 6, 6 are placed at an intermediate position between the pair of left and right cam journal parts 31A, 31B (i.e., in the play area of the bearing hole 21). The camshaft 3 is attached to a portion corresponding to the camshaft 3, and is appropriately offset in the axial direction of the camshaft 3. By doing this, in addition to the effect of preventing seizure of the camshaft 3 as in the case of the other bearings 2, 2, the bolts between the two rocker shafts 4, 4 can be prevented. Since the hole pitches are different, there is an advantage that incorrect assembly of the rocker shafts 4, 4 (that is, mis-assembly of the rocker shaft for the intake valve and the rocker shaft for the exhaust valve) can be reliably prevented.

(Effects of the invention) The valve train structure of the SOHC engine of the present invention is provided with a bearing part that is integrally molded on the upper part of the cylinder head and has a bearing hole inside, and a cam is connected to the bearing hole of the bearing part. A shaft is disposed through the bearing hole, and the cam journal part of the camshaft is rotatably supported by the bearing hole.A rocker shaft, which is disposed parallel to the camshaft, is placed above the bearing part and is connected to the bearing hole. In the SOHC engine, the cam journal part of the camshaft and the mounting bolt are fixed to the bearing part by a mounting bolt screwed to a position close to the bearing hole. It is characterized by being arranged in a mutually eccentric state in the direction.

Therefore, according to the valve train structure of the SOHC engine of the present invention, since the mounting bolt and the cam journal part of the camshaft are arranged eccentrically in the axial direction with respect to the bearing part, the mounting bolt Even if the part of the bearing hole that corresponds to the mounting bolt bulges inward due to tightening and the roundness of this part is slightly lost, this deformation will not extend to the part that corresponds to the cam journal part. Because the roundness of the zuko part is maintained well,
A practical effect is obtained in that seizure between the bearing hole and the cam journal portion is prevented in advance and reliably.

[Brief explanation of drawings]

FIG. 1 is a plan view of a camshaft of an engine equipped with a valve train structure according to an embodiment of the present invention, and FIG. 2 is an enlarged longitudinal cross-sectional view of FIG. 1. 1...Cylinder head, 2...Bearing section, 3...
Cam shaft, 4...Rotzker shaft, 5...Press member, 6
...Mounting bolt, 21...Bearing hole, 31...Cam journal part, 32...Small diameter part, 51...Bulging deformation part.

Claims (1)

[Scope of utility model registration request] A bearing part that is integrally molded and has a bearing hole inside is provided in the upper part of the cylinder head, and a camshaft is arranged so as to pass through the bearing hole of the bearing part, and the camshaft is While the cam journal part is rotatably supported, a rocker shaft, which is arranged parallel to the camshaft above the bearing part, is attached to a mounting bolt screwed into the bearing part and at a position close to the bearing hole. In the SOHC engine fixed by twisting, the cam journal part of the camshaft and the mounting bolt are arranged eccentrically relative to the bearing part in the axial direction thereof. Valve train structure of SOHC engine.