JP2000282811A - Support structure of cam shaft with variable valve timing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the sense of incongruity given to a driver by a method, wherein the influence of hammering generated due to interference between a cam shaft and a bearing increased owing to provision of a variable valve timing mechanism is suppressed. SOLUTION: A variable valve timing mechanism 20, situated at the forward end of a cam shaft 6, relatively turns a cam pulley 13 and the cam shaft 6 in synchronism with the crank shaft. A thrust bearing 15 to regulate displacement in the axial direction of the cam shaft 6 is situated at the internal part of a cam chamber 10 in a state to be covered with a head cover 5. Thereby, hammering generated along with interference between the cam shaft 6 and the thrust bearing 15 hardly leaks to the external part of an internal combustion engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a variable valve timing mechanism for varying the opening / closing timing (valve timing) of an engine valve with respect to the rotation phase of an engine output shaft. The present invention relates to a structure for supporting a camshaft supported by the engine.

[0002]

2. Description of the Related Art As is well known, a variable valve timing mechanism that varies the valve timing of an engine valve according to the operating state of an internal combustion engine has been put to practical use. An example of such a variable valve timing mechanism is disclosed in JP-A-6-1590.
Japanese Patent Application Publication No. 20-205200 discloses that the valve timing of an engine valve that is opened and closed with the rotation of the camshaft is made variable by changing the relative rotation phase of the camshaft with respect to the crankshaft that is the engine output shaft. A described mechanism is described.

FIG. 4 shows a side sectional structure of a camshaft provided with such a variable valve timing mechanism, and a side sectional structure of a cylinder head portion provided with the camshaft.

As shown in FIG. 4, a distal end of a camshaft 106 provided with a plurality of cams 107 is drivingly connected to a crankshaft (not shown) serving as an engine output shaft via a timing belt or the like. A cam pulley 113 that rotates in synchronization with the crankshaft is mounted to be rotatable relative to the camshaft 106. This cam pulley 113
Is connected to the camshaft 1 via a variable valve timing mechanism 120 also provided at the tip of the camshaft 106.
06.

The variable valve timing mechanism 12
0 changes the relative rotational phase between the camshaft 106 and the cam pulley 113 appropriately,
The valve timing of an engine valve (not shown) that is driven to open and close by a cam 107 provided in the engine is variable.

The camshaft 106 provided with the variable valve timing mechanism 120 is mounted on the cylinder head 101.
The cam chamber 11 of the internal combustion engine is provided by a plurality of bearings 111 and 112 provided between
It is supported in 0. Of these bearings, the bearing 112 provided for each cylinder is a simple sliding bearing that rotatably supports the camshaft 106.

On the other hand, a bearing 111 located on the outermost wall of the cylinder head 101 and located at the most distal end of the camshaft 106 is a slide bearing that rotatably supports the camshaft 106, It also serves as a thrust bearing for restricting the axial displacement of the shaft 106. Generally, a thrust bearing for restricting the displacement of the camshaft in the axial direction is provided on the outer wall of the cylinder head for ease of processing and the like.

[0008] The cam cap 102 is provided with a hydraulic control valve for controlling the hydraulic pressure supplied to the variable valve timing mechanism 120. Further, the cam chamber 110 in which the camshaft 106 is disposed is provided in the head cover 1.
05 covers its upper surface.

[0009]

As described above, the camshaft 106 includes the cylinder head 101 and the head cover 1.
05 in the cam chamber 110 formed between
The bearings 1 and 112 are rotatably supported, and the bearing 111 restricts displacement in the axial direction.

However, the camshaft 1 provided with the variable valve timing mechanism 120 at its end as described above.
In 06, since the weight of the end of the camshaft 106 increases and the cam pulley 113 is not fixed to the end of the camshaft 106, the fluctuation of the force in the axial direction increases. As a result, the displacement of the camshaft 106 in the axial direction increases, causing an increase in hammering noise due to the interference between the camshaft 106 and the thrust bearing 111, and giving an uncomfortable feeling to the driver and the like.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the influence of a tapping sound caused by interference between a camshaft and a bearing, which is increased by providing a variable valve timing mechanism. Another object of the present invention is to provide a camshaft support structure with a variable valve timing mechanism, which can reduce a sense of discomfort given to a driver or the like.

[0012]

In order to achieve the above object, the present invention is directed to a cam provided with a variable valve timing mechanism for varying a valve timing of an engine valve with respect to a rotation phase of an engine output shaft. The gist is a structure for supporting a shaft on an internal combustion engine, wherein a thrust bearing for restricting displacement of the camshaft in the axial direction is provided in a cam chamber covered by a head cover of the engine.

According to this structure, the axial displacement of the camshaft, which increases due to the provision of the variable valve timing mechanism, is reduced by the thrust bearing provided inside the cam chamber covered by the head cover of the engine. Be regulated. For this reason, with the displacement of the camshaft in the axial direction, the tapping noise generated by the interference between the camshaft and the thrust bearing is generated inside the cam chamber covered by the head cover, and the internal combustion engine It is hard to leak outside.

[0014] The invention described in claim 2 is the first invention.
In the supporting structure for a camshaft with a variable valve timing mechanism described in the above, the gist is that the thrust bearing is provided at the other end of the shaft end of the camshaft where the variable valve timing mechanism is provided.

According to the above configuration, since the thrust bearing is provided at the other end of the shaft end provided with the variable valve timing mechanism, the processing is facilitated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described in detail. FIG. 1 shows a side structure of a camshaft with a variable valve timing mechanism and a cross-sectional structure of a side of a cylinder head portion on which the camshaft is pivotally supported.

As shown in FIG. 1, the camshaft 6
Cam caps 2, 3, and 4 fixed to the upper surface of the cylinder head 1 and the cylinder head 1 by bolts (not shown)
Are mounted in a cam chamber 10 formed between the cylinder head 1 and the head cover 5.

In the camshaft 6, a cam pulley 13 is mounted on the tip end of the cylinder head 1 protruding from the tip side outer wall 1 a so as to be rotatable relative to the camshaft 6. The cam pulley 13 is drivingly connected to a crankshaft (not shown) as an engine output shaft via a timing belt (not shown), and rotates in synchronization with the crankshaft. The cam pulley 13 is connected to the camshaft 6 via a variable valve timing mechanism 20 provided at the tip of the camshaft 6. The rotation of the cam pulley 13 is transmitted to the camshaft 6 via the variable valve timing mechanism 20.

Hereinafter, the variable valve timing mechanism 20
The configuration will be briefly described. FIG. 2 shows a side sectional structure of the variable valve timing mechanism 20, and FIG. 3 shows a front structure thereof.

As shown in FIG. 2, the variable valve timing mechanism 20 includes an internal rotor 40, a housing 42, a cover 45, and the like. The internal rotor 40 is attached to the camshaft 6 by a center bolt 46 so as to be integrally rotatable. Also, the housing 42 and the cover 45
Is a cam pulley 1 which is relatively rotatably provided at the tip end of the camshaft 6 by the fixing bolt 54 as described above.
3 and rotatably mounted.

Further, as shown in FIG.
A plurality of (four in this example) vanes 41 are radially formed on the outer periphery of the. On the other hand, the vane 4 of the internal rotor 40 is provided on the inner periphery of the housing 42 in the manner shown in FIG.
The same number of protrusions 44 as one are formed, and the vanes 41 are respectively accommodated in recesses 43 formed between the adjacent protrusions 44.

The tip of each vane 41 is in sliding contact with the inner periphery of the recess 43, and the tip of the projection 44 is
Is in sliding contact with the outer periphery of. Therefore, the inner rotor 40 and the camshaft 6, the cam pulley 13 and the housing 42
The front cover 45 and the front cover 45 can be relatively rotated about the same axis.

In the recess 43, two spaces 47 and 48 are formed by being partitioned by the vanes 41. Hereinafter, of these two spaces 47 and 48, the space 47 on the side of the rotation direction of the cam shaft 6 with respect to the vane 41 (the direction indicated by the arrow A in FIG. 3) will be referred to as a retard pressure chamber.
The space 48 on the opposite side is referred to as an advanced pressure chamber.

As shown in FIG. 2, the retard side pressure chamber 47 and the advance side pressure chamber 48 are provided with a retard side oil chamber formed inside the camshaft 6 or the cylinder head 1 (FIG. 1). The passage 23 and the advance side oil passage 22 are connected to the hydraulic control valve 19. The hydraulic control valve 19 further includes an oil supply path 21 through which the oil pumped and discharged by the oil pump 16 is sent from the oil pan 14, and a drain path 32 for recirculating the oil to the oil pan 14. Is connected.

The hydraulic control valve 19 is an electromagnetic valve driven and controlled by an electronic control unit 18 for controlling the operation of the internal combustion engine. Then, based on the command signal from the electronic control unit 18, one of the oil supply passage 21 and the drain passage 32 is selectively connected to the retard side oil passage 23 and the advance side oil passage 22, respectively. In this manner, the drain passage 32 is supplied so that oil is supplied to the oil passage connected to the oil supply passage 21 by the hydraulic control valve.
The oil is discharged from the oil passage connected to the oil passage. As a result, the pressure of the oil filled in each of the pressure chambers 47 and 48 is changed.

The variable valve timing mechanism 20 is operated by a difference in oil pressure between the oil filled in the pressure chambers 47 and 48. That is, if a difference occurs in the oil pressure in each of the pressure chambers 47 and 48, a difference also occurs in the forces acting on both side surfaces of the vane 41, and the internal rotor 40 is connected to the housing 42.
, A driving force for relative rotation is generated. By rotating the internal rotor 40 relative to the housing 42 in this manner, the rotational phase of the cam shaft 6 and the cam pulley 13 connected thereto is changed. As a result, the rotation phase of the camshaft 6 with respect to the crankshaft is changed, and the opening / closing valve timing (valve timing) of an engine valve (not shown) that is driven to open and close with the rotation of the camshaft 6 is made variable.

As described above, the operation amount of the variable valve timing mechanism 20 is controlled based on the drive control of the hydraulic control valve 19 by the electronic control unit 18 so that the valve timing according to the operating state of the internal combustion engine is obtained. You. In addition,
In the present embodiment, the hydraulic control valve 19 is actually disposed so as to be built in the cam cap 2 as shown in FIG.

In the present embodiment, the camshaft 6 having such a variable valve timing mechanism 20 mounted at the tip thereof is connected to the upper surface of the cylinder head 1 and the cam cap 2 in the manner shown in FIG. 3 and 4 are supported by bearings 11, 12, and 15 formed therebetween. Among these bearings, a bearing 11 provided on the outer wall 1a of the cylinder head 1 and located on the most distal end side (a side on which the cam pulley 13 is mounted) of the camshaft 6, and two cams 7 provided for each cylinder The bearing 12 provided therebetween is a slide bearing that rotatably supports the camshaft 6.

On the other hand, the bearing 15 formed on the rearmost end of the camshaft 6 (the side opposite to the side on which the cam pulley 13 is mounted) is a slide bearing that rotatably supports the camshaft 6 and The camshaft 6 also serves as a thrust bearing for restricting the axial displacement of the camshaft 6.

In this embodiment, the thrust bearing 15 is provided in the cam chamber 10 which is covered with the head cover 5 and hermetically closed as described above. For this reason, even if the camshaft 6 and the thrust bearing 15 interfere with each other due to the axial displacement of the camshaft 6 to generate a tapping sound, the tapping sound is less likely to leak to the outside of the internal combustion engine. In addition, the provision of the variable valve timing mechanism 20 increases the displacement of the camshaft 6 in the axial direction,
Even if the tapping sound increases, the uncomfortable feeling given to the driver and the like by the tapping sound can be sufficiently suppressed.

Incidentally, in the internal combustion engine in which the hydraulically operated variable valve timing mechanism 20 is provided at the tip of the camshaft 6 as in the present embodiment, the cylinder head 1 closest to the variable valve timing mechanism 20 is generally used. Exterior wall 1
The structure is such that oil is supplied and discharged through a bearing 11 provided at a. In this regard, in the present embodiment, the bearing 11 may be a slide bearing that merely supports the camshaft 6 rotatably, and the portion of the camshaft 6 corresponding to the bearing 11 may be a stepped portion such as a thrust bearing. Since there is no need to form such an external shape, the external shape can be simplified. For this reason, the pressure chambers 47, 48 of the variable valve timing mechanism 20
Thus, it is easy to form an oil passage for supplying and discharging oil, and the degree of design freedom can be increased.

Further, in this embodiment, the thrust bearing 15 which needs to form a step or the like at the corresponding camshaft 6 is connected to the other end of the shaft end of the camshaft 6 on which the variable valve timing mechanism 20 is provided. , So that processing and the like can be facilitated.

The effects obtained by the above-described camshaft supporting structure with a variable valve timing mechanism of the present embodiment are listed below. (1) Since the thrust bearing 15 that regulates the axial displacement of the camshaft 6 is provided inside the cam chamber 10 that is covered and sealed by the head cover 5, interference between the camshaft 6 and the thrust bearing 15 is provided. The tapping sound caused by this is less likely to leak out of the internal combustion engine. For this reason,
Even if the thrust bearing 15 itself increases in the thrust bearing 15 due to the provision of the variable valve timing mechanism 20, the unpleasant sensation given to the driver by the striking noise can be kept low.

(2) Further, as a result that the bearing 15 located at the rearmost end of the camshaft 6 is a thrust bearing, it is located closest to the variable valve timing mechanism 20 and formed on the outer wall 1a of the cylinder head 1. The bearing 11 can be configured as a plain bearing that simply supports the camshaft 6 rotatably. For this reason, the outer shape of the bearing 11 can be simplified, and the oil passages 47 and 4 for supplying and discharging oil to and from the variable valve timing mechanism 20.
8 can be easily formed. In addition, these oil passages 4
The degree of freedom of design such as 7, 48 can be increased.

(3) Also, a thrust bearing 15 which needs to form a step or the like at the corresponding camshaft 6 is provided at the other end of the camshaft 6 at the shaft end where the variable valve timing mechanism 20 is provided. Therefore, the processing and the like can be facilitated.

The above-described embodiment can be modified as follows. -In the present embodiment,
Although the rearmost bearing 15 of the camshaft 6 is configured as a thrust bearing, a thrust bearing is provided at another portion of the camshaft 6 within the cam chamber 10 sealed by the head cover 5. Is also good. Even in such a case, effects similar to those of the present embodiment can be obtained.

In the present embodiment, the cam pulley 13 and the camshaft 6 to which the rotation of the crankshaft is transmitted via the timing belt are relatively rotated by the variable valve timing mechanism 20. The camshaft support structure of the present invention has a structure in which the variable valve timing mechanism relatively rotates a cam sprocket to which rotation is transmitted via a timing chain, or a gear to which rotation of a crankshaft is transmitted and a camshaft relative to each other. The present invention may be applied to a configuration in which the camshaft is rotated, or a configuration in which two camshafts provided for intake and exhaust are driven and connected by gears, and one of them is provided with a variable valve timing mechanism. In such a case, the same effect as in the present embodiment can be obtained.

The variable valve timing mechanism provided on the camshaft to which the support structure of the present invention is applied is not limited to the so-called vane type variable valve timing mechanism as in the present embodiment. In addition, the present invention can be similarly applied to a camshaft provided with a variable valve timing mechanism such as a helical gear type. Further, the support structure according to the present invention can be similarly applied to a camshaft provided with a variable valve timing mechanism using a drive source other than the hydraulic pressure, such as an electric type.

[0039]

According to the first aspect of the present invention, the tapping noise between the camshaft and the thrust bearing which is increased by providing the variable valve timing mechanism is generated inside the cam chamber covered by the head cover. And it is difficult for the gas to leak out of the internal combustion engine. For this reason, it is possible to reduce the sense of discomfort given to the driver or the like due to the tapping sound.

According to the second aspect of the present invention, since the thrust bearing is provided at the other end of the shaft end where the variable valve timing mechanism is provided, the machining is facilitated.

[Brief description of the drawings]

FIG. 1 is a side and side sectional view showing one embodiment of a support structure of a camshaft with a variable valve timing mechanism according to the present invention.

FIG. 2 is a sectional view showing a side sectional structure of a variable valve timing mechanism.

FIG. 3 is a sectional view showing a front sectional structure of a variable valve timing mechanism.

FIG. 4 is a side sectional view showing a conventional camshaft supporting structure with a variable valve timing mechanism.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 1a ... Outer wall, 2, 3, 4 ... Cam cap, 5 ... Head cover, 6 ... Cam shaft, 7 ... Cam, 10 ... Cam chamber, 11, 12 ... Sliding bearing, 13 ...
Cam pulley, 14 oil pan, 15 thrust bearing, 16 oil pump, 18 electronic control unit, 19 ...
Hydraulic control valve, 20 ... variable valve timing mechanism, 21 ...
Oil supply passage, 22: advance side oil passage, 23: retard side oil passage, 32: drain passage, 40: internal rotor,
41 ... Vane, 42 ... Housing, 43 ... Recess, 44 ...
Projecting portion, 45: cover, 46: center bolt, 47: retard pressure chamber, 48: advance pressure chamber, 54: mounting bolt.

Claims (2)

[Claims] 1. A structure in which a camshaft provided with a variable valve timing mechanism for varying a valve timing of an engine valve with respect to a rotation phase of an engine output shaft is supported by an internal combustion engine. A camshaft support structure with a variable valve timing mechanism, wherein a thrust bearing for regulating displacement is provided inside a cam chamber covered by a head cover of the engine. 2. The cam with a variable valve timing mechanism according to claim 1, wherein the thrust bearing is provided on the other end of the shaft end of the camshaft on which the variable valve timing mechanism is provided. Shaft support structure.