JP3087775B2 - Variable valve timing mechanism for internal combustion engine and method of assembling the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing mechanism for an internal combustion engine, and more particularly to a variable valve timing mechanism for an internal combustion engine that can reduce the resistance and wear of a sliding portion and reduce the external dimensions. .

[0002]

2. Description of the Related Art Various types of variable valve timing mechanisms for internal combustion engines of this type have been proposed. For example, a general valve timing variable mechanism using hydraulic pressure is shown in FIG.

That is, a cylindrical hub 2 is fixed to the end of the camshaft 1, and a sleeve 4 is mounted outside the hub 2 via a piston 3. A timing gear 5 is screwed to the sleeve 4. At the rear end of the sleeve 4, a spacer 6 is fixedly provided together with the timing gear 5. The inter-cam gear 8 is coupled with the spacer 6 and the bearing 7 of the camshaft 1 interposed therebetween, and is fixed by a lock nut 9. The bearing portion 7 of the camshaft 1 is fitted to a bearing portion 19 of a cylinder head 18 and is rotatably supported. An oil seal 20 is interposed between the front end of the bearing 19 of the cylinder head 18 and the outer peripheral surface of the spacer 6.

[0004] The piston 3 incorporated between the sleeve 4 and the hub 2 has a cylindrical structure divided into two parts in the axial direction, and both divided parts are provided with a plurality of pins 10 arranged in the circumferential direction.
Are fixed to each other. Inside and outside of the piston 3, helical splines 11,
12 are formed. A helical spline 13 is formed outside the hub 2 with respect to the spline 11 inside the piston 3, and a helical spline 14 is formed around the inner periphery of the sleeve 4 with respect to the spline 12 outside the piston 3. . The piston 3 is the sleeve 4
Is urged toward the front side by a spring 15 mounted between the end face of the head.

[0005] The cylindrical hub 2 is fixed to the camshaft 1 by a fixing bolt 17 via a locking member 16. The fixing bolt 17 has an axial through hole (not shown) communicating with an oil passage (not shown). Further, a pressure chamber (not shown) into which a hydraulic pressure from an oil passage (not shown) is introduced is provided facing the front part of the piston 3. When hydraulic pressure is introduced into the pressure chamber via the oil passage and the piston 3 moves rearward in the axial direction while compressing the spring 15, the splines 11 and 12 formed on the inner and outer circumferences of the piston 3 in opposite directions to each other. One of the timing gears 5 integrally screwed to the fitted hub 2 and sleeve 4 rotates relative to the other. Thereby, the phase between the camshaft 1 integrated with the hub 2 and the timing gear 5, that is, the valve timing changes.

[0006]

However, in the above-mentioned mechanism, the weight of the variable valve timing mechanism assembly, which protrudes from the bearing 19 of the cylinder head 18 and is disposed in a cantilever state, and acts on the timing gear 5. Due to the tension of the timing belt, an uneven load occurs in the bearing portion 19 of the cylinder head 18, resulting in uneven wear of the bearing portion 19,
Seizure is likely to occur, and since a bending load is applied directly to the sleeve 4 on which the timing gear 5 is screwed, the sleeve 4 bends and deforms, and the smooth sliding movement of the piston 3 is hindered. In addition, the assembly is complicated and the external dimensions are large. Further, the oil seal 20 of the cylinder head bearing 19 is previously mounted on the valve timing variable mechanism assembly side (specifically,
Since it is necessary to assemble the cylinder head 18 after mounting it on the spacer 6), not only the assembling workability is not good, but also the outer peripheral surface of the oil seal may be damaged at the time of assembling.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and an object of the present invention is to suppress uneven wear of a camshaft bearing, to ensure smooth movement of a sliding portion, and to reduce external dimensions. It is an object of the present invention to provide a variable valve timing mechanism of an internal combustion engine that can reduce the number of assembly steps due to the reduction in size and the number of parts.

[0008]

According to the present invention, there is provided a camshaft for driving an intake valve or an exhaust valve, a hub fitted to one end of the camshaft, A substantially hollow cylindrical sleeve disposed so as to surround the outer side surface, interposed between the hub and the sleeve, engaged with the hub and the sleeve,
A relative rotation angle difference providing means for providing a relative rotation angle difference between the two by moving in the axial direction of the shaft; and an input member provided integrally with the sleeve and providing a rotational motion to the sleeve. In the variable valve timing mechanism for an internal combustion engine, the sleeve may be moved in the camshaft axial direction.
A bearing portion is provided on an outer peripheral surface at a position where the relative rotation angle difference providing means is provided, and a bearing portion of the sleeve is provided with a half-shaped bearing portion recessed in a cylinder head . The cylinder
The entire bearing is fixed to the head and forms a pair with the bearing.
It is characterized in that it is rotatably sandwiched and supported between a cam cap formed with a half-split bearing portion to be formed .

[0009]

[0010]

[0011]

In addition, the present invention provides a camshaft for driving an intake valve or an exhaust valve, a hub fitted to one end of the camshaft, and a substantially arranged surrounding the outer surface of the hub. A hollow cylindrical sleeve, a relative rotation angle difference providing means interposed between the hub and the sleeve for providing a relative rotation angle difference between the two, and fitted to a bearing recessed in the cylinder head; An oil seal interposed in a gap between the outer peripheral surface of the sleeve and the front end of the cylinder head, and an input member provided integrally with the sleeve to impart rotational motion to the sleeve. In the method for assembling a variable valve timing mechanism, a camshaft in which the piston, the spring, and the hub are fitted to one end of a sleeve having an outer peripheral surface provided with a bearing portion. After assembling, and placing the object bearing portion of the sleeve half shaped bearing portion of the cylinder head,
A half-split bearing so as to cover the half of the bearing part of the sleeve
A cam cap forming a portion is fixed to a bearing portion of the cylinder head to clamp the sleeve, and then an oil seal is provided from a front side of the cylinder head to a gap between the outer peripheral surface of the sleeve and a front end of the cylinder head. Fitting
Thereafter, an input member is fixed to the front end of the sleeve.

[0013]

To describe the operation of the present invention, mosquito sleeve
Means for giving a relative rotation angle difference in the axial direction of the shaft
A bearing portion is provided on the outer peripheral surface at a position where the inner portion of the sleeve is located, and the bearing portion of the sleeve is formed into a half-shape recessed in the cylinder head.
And a bearing fixed to the cylinder head and paired with the bearing.
Since then rotatably sandwiched supported between the mosquito <br/> Mukyappu bearing portions forming half-like constituting the entire bearing unit form a variable
The protruding amount of the change mechanism from the bearing part is small (cantilever
The bias of the load on the bearing portion can be reduced), and the load acting on the bearing portion of the cylinder head can be equalized.
Uneven wear and seizure of the bearing metal can be suppressed, bending deformation of the sleeve can be suppressed, and smooth sliding movement of the piston can be ensured.

[0014]

[0015]

Further, to be bearing portion provided on the outer peripheral surface of the sleeve, rotatably sandwiched supported between a bearing portion to be bearing portion is recessed in the cylinder head of the sleeve and cam cap provided in the bearing section In the method for assembling a variable valve timing mechanism of an internal combustion engine, after a piston, a spring, and a camshaft having a hub fitted to one end thereof are attached to a sleeve provided with a bearing portion on an outer peripheral surface, Split the sleeve bearing part into half of the cylinder head.
Placed on the bearing portion of Jo, so as to cover the target bearing portion half sleeve, the cam cap forms a half-shaped bearing portions were allowed to sandwich the sleeve and fixedly provided to the bearing portion of the cylinder head Since the oil seal is fitted in the gap between the outer peripheral surface of the sleeve and the front end of the cylinder head from the front side of the cylinder head, and the input member is fixed to the front end of the sleeve after that, the valve including the sleeve is included. After incorporating the variable timing mechanism assembly into the cylinder head, the oil seal can be fitted from the front side of the sleeve,
The assembly workability is good, and the outer peripheral surface of the oil seal is not damaged.

[0017]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partially sectional side view showing the structure of an embodiment of a variable valve timing mechanism for an internal combustion engine according to the present invention. FIG. 1 shows a DO having two camshafts for driving an intake valve and an exhaust valve, respectively.
The case where the variable valve timing mechanism according to the present invention is applied to an HC engine is shown.

A hub 24 is fitted to the front end of the cylinder head 22 of one of the camshafts 20 for driving the intake valve or the exhaust valve. The hub 24 is integrally connected to the camshaft 20 by a fixing bolt 28 that is screwed into a female thread (not shown) formed at an end of the camshaft 20 via a locking member 26. Although not shown, a through hole communicating with oil supply means (not shown) is formed in the fixing bolt 28 so that oil can be supplied to the space inside the hub 24 under a predetermined engine operating condition. It can be introduced.

The hub 24 and the substantially hollow cylindrical sleeve 30 disposed so as to surround the outer periphery thereof are axially divided into two parts and fixed to each other by a plurality of circumferentially arranged pins 36. The rotation can be made relative to each other via a cylindrical piston 32 as a relative rotation angle difference providing means. That is, the helical spline 40 formed on the outer periphery of the hub 24 and the helical spline 42 formed on the inner periphery of the sleeve 30 mesh with the helical spline 34 formed on the inner and outer periphery of the piston 32 in opposite directions. When the piston 32 slides rearward in the axial direction of the camshaft 20, the hub 24 and the sleeve 30 rotate relative to each other.

The piston 32 is normally urged forward (to the left in FIG. 1) by a spring 38. Then, as described above, when oil is introduced into the hub 24 from oil supply means (not shown) under a predetermined engine operating state, the oil resists the urging force of the spring 38. Then, the piston 32 is pushed rearward in the axial direction of the camshaft 20, and a relative rotation angle difference is generated between the hub 24 and the sleeve 30, whereby the valve timing is changed. The axial movement of the camshaft 20 and the hub 24 is regulated by a spring 44 that urges the hub 24 toward the rear end of the cylinder head 22.

A piston as the relative rotation angle difference providing means in the camshaft axial direction on the outer peripheral surface of the sleeve 30
The bearing portion 4 is located at substantially the center of the position where the
8 is formed, the object bearing portion 48 includes a half-like bearing portion 46 which is recessed in the cylinder head 22, the serial
And is fixed to the head 22 to form a pair with the bearing 46.
Bearing that is also formed in a half-shape
It is rotatably fitted to the cam cap 22a as a part . Further, the movement of the sleeve 30 in the axial direction is performed by fitting the sleeve 30 into the annular recess 50 of the cylinder head 22.
Receiving part 5 formed as an annular projection on the outer periphery of
2 regulated. An oil seal 54 is interposed between the front opening of the cylinder head 22 and the outer peripheral surface of the sleeve 30, and is sealed in a liquid-tight manner.

A plate 58 is screwed to the front end surface of the sleeve 30 by bolts 56. Further, a timing gear 62 as an input member is screwed to the plate 58 by a bolt 60. In this embodiment, a timing belt (not shown) is wound around the timing gear 62, and the rotational movement of a crankshaft (not shown) is transmitted to the timing gear 62 and the sleeve 30 integrally connected thereto. You. A drive side cam gear 66 is screwed to the rear end of the sleeve 30 by bolts 64. The drive-side inter-cam gear 66 transmits the rotation of the timing gear 62 to a driven-side inter-cam gear that drives the other cam shaft indicated by a virtual line in the drawing.

Next, to explain the action of this embodiment, the phase of the cam shaft axial direction of the sleeve 30
Forming a target bearing portion 48 on the outer circumferential surface of the position for underlying the pair rotation angle difference imparting means, to be bearing portion of the sleeve, the half-shaped bearing portion 46 which is recessed in the cylinder head 22, this
Fixed to the cylinder head 22 in pairs with the bearing 46
It is also a half-split bearing that constitutes the entire bearing
The variable valve timing mechanism assembly itself including the sleeve 30 is fitted to the cam head 22a formed between the cylinder head 2 and the cylinder head 2.
2 and the bearing portion 4 of the sleeve 30
8 and the load acting on the bearing portion 46 of the cylinder head 22 can be equalized.
Uneven wear and image sticking can be suppressed. In the present embodiment, since the bearing portion 48 is formed substantially at the center of the sleeve 30 as viewed in the axial direction of the camshaft 20, the above-described operation is more excellent. Further, since the sliding portion of the piston 32 is disposed inside the bearing portion 48 of the sleeve 30, that is, the sliding portion of the piston 32 is reliably supported by the bearing portion 46 of the cylinder head 22, so that the timing gear 62 3 in the sliding portion of the piston 32 caused by the tension of the timing belt acting on the sleeve 3
The amount of bending deformation of zero can be suppressed, and a smooth sliding movement of the piston 32 can be ensured.

Further, since the timing gear 62 is screwed to the front end surface of the sleeve 30, bending deformation of the sleeve 30 due to the tension of the timing belt is further suppressed, and the piston 32
Can more smoothly slide. In this embodiment, since the timing gear 62 is screwed onto the front end surface of the sleeve 30 via the plate 58, the tension of the timing belt acting on the timing gear 62 is partially changed by the deformation of the plate 58. The effect of being absorbed is also obtained.

Further, a spring 38 for urging the piston 32 toward the front side of the sleeve 30 is provided.
Is locked by the drive-side inter-cam gear 66 screwed to the rear end portion, so that there is no need to separately provide a retainer or the like for locking the spring 38, so that the number of parts can be reduced and the outer shape can be reduced. The size can be reduced.

In addition, in assembling the variable valve timing mechanism into the cylinder head 22, the piston 32, the spring 38, and the hub 24 are fitted to one end of the sleeve 30 provided with the bearing portion 48 on the outer peripheral surface. After assembling with the camshaft 20, the bearing portion 48 of the sleeve 30 is placed on the bearing portion 46 of the cylinder head 22, and the cam cap 22 is covered so as to cover the bearing portion 48 of the sleeve 30.
a is fixed to the bearing portion 46 of the cylinder head 22 so that the sleeve 30 is sandwiched, and then the oil seal 54 is fitted from the front side of the cylinder head 22 into the gap between the outer peripheral surface of the sleeve 30 and the front end of the cylinder head 22. Since the timing gear 62 is fixed to the front end of the sleeve 30 after that, the variable valve timing mechanism assembly including the sleeve 30 is assembled to the cylinder head 22 and then the oil seal 54 is attached to the front end of the cylinder head 22. Unlike the case where the oil seal 54 is previously mounted on the variable valve timing mechanism assembly and then assembled into the cylinder head 22, the assembly workability is good and the outer peripheral surface of the oil seal 54 is damaged. There is no fear.

Next, another embodiment of the present invention will be described. FIG. 2 is a partially sectional side view showing the structure of another embodiment of the variable valve timing mechanism for an internal combustion engine according to the present invention. The basic configuration of this embodiment is the same as that of the first embodiment. However, in this embodiment, an adapter 59 is attached to the front end of the sleeve 30 by bolts 57.
A timing gear 62 as an input member is screwed to the adapter 59 by a bolt 61. The sleeve 3 for the cylinder head 22
The bearing of the cylinder head 22 is formed by giving the adapter 59 a journal function.
The fitting of the portion corresponding to the bearing portion 48 of the sleeve 30 is provided solely for restricting the movement of the sleeve 30 in the axial direction. That is, in the present embodiment, since the tension of the timing belt acting on the timing gear 62 is borne by the bearing portion of the adapter 59 of the cylinder head 22, the amount of bending deformation generated in the sleeve 30 is reduced by the first amount.
While it can be further suppressed as compared with the embodiment,
Since the outer diameter of the bearing portion can be reduced as compared with the case where the bearing portion 48 is provided on the sleeve 30, the lubricity of the bearing portion can be improved, and uneven wear and seizure can be suppressed. In order to provide the adapter 59 with a function of restricting the axial movement of the sleeve 30, the imaginary line (two-dot chain line) in FIG.
As shown in the above, the bearing portion 47 may be provided on the cylinder head 22 and the bearing portion 49 may be provided on the adapter 59 so that the thrust can be received at the same time. Other operations are the same as those described in the first embodiment.

In this embodiment, as described above, the relative rotation angle difference providing means for providing the relative rotation angle difference between the input member and the camshaft is of a hydraulic drive type. For example, a method using an actuator such as a solenoid coil or a motor may be used.

[0029]

As described in detail above, according to the present invention,
Exhibits the following excellent effects. (1) The relative position of the sleeve in the camshaft axial direction
To be bearing portion provided on the outer peripheral surface of the position for underlying the rotational angle difference imparting means, to be bearing portion of the sleeve, the half-shaped bearing portion which is recessed in the cylinder head, solid to the cylinder head
Halves that form a pair with the bearing part and constitute the entire bearing part
It is rotatably pinched and supported between the cam cap and the cam bearing that has the shape of a bearing , so that the amount of protrusion of the variable mechanism from the bearing is small.
(With less bias in the load on the bearing due to cantilever)
As a result, the load acting on the bearing portion of the cylinder head can be equalized, uneven wear and seizure of the bearing metal can be suppressed, the bending deformation of the sleeve can be suppressed, and the smooth sliding movement of the piston can be achieved. Can be secured. ( 2 ) A bearing portion is provided on the outer peripheral surface of the sleeve, and the bearing portion of the sleeve is rotatably sandwiched and supported between a bearing portion recessed in the cylinder head and a cam cap provided on the bearing portion. In the method for assembling a variable valve timing mechanism for an internal combustion engine, a piston, a spring, and a camshaft having a hub fitted to one end thereof are assembled to a sleeve provided with a bearing portion on an outer peripheral surface, and then the sleeve is assembled. of the bearing part is placed on the half-shaped bearing portion of the cylinder head, so as to cover the target bearing portion half sleeve, half-shaped
The cam cap forming the bearing is fixed to the bearing of the cylinder head , and the sleeve is clamped.The oil seal is fitted from the front side of the cylinder head into the gap between the outer peripheral surface of the sleeve and the front end of the cylinder head. Then, since the input member is fixed to the front end of the sleeve, the oil seal can be fitted from the front side of the sleeve after the variable valve timing mechanism assembly including the sleeve is assembled into the cylinder head. As a result, the assembling workability is good, and the outer peripheral surface of the oil seal is not damaged.

[Brief description of the drawings]

FIG. 1 is a partially sectional side view showing the structure of an embodiment of a variable valve timing mechanism for an internal combustion engine according to the present invention.

FIG. 2 is a partially broken side sectional view showing the structure of another embodiment of the variable valve timing mechanism for an internal combustion engine according to the present invention.

FIG. 3 is a partially sectional side view showing a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 20 Camshaft 22 Cylinder head 24 Hub 28 Fixing bolt 30 Sleeve 32 Piston 34, 40, 42 Helical spline 46 Bearing part 48 Bearing part 54 Oil seal 58 Plate 59 Adapter 62 Timing gear 66 Gear between drive side cams

Claims (2)

(57) [Claims] 1. A camshaft for driving an intake valve or an exhaust valve, a hub fitted to one end of the camshaft, and a substantially hollow cylindrical member disposed so as to surround an outer surface of the hub. and the sleeve, is interposed between the hub and the sleeve, the hub and the
Engage the sleeve and move it in the axial direction of the camshaft.
A variable valve timing mechanism for an internal combustion engine, comprising: a relative rotation angle difference providing means for providing a relative rotation angle difference between the two; and an input member provided integrally with the sleeve and providing rotation movement to the sleeve. The relative rotation in the camshaft axial direction of the sleeve.
A bearing portion is provided on the outer peripheral surface at a position where the rolling angle difference applying means is provided, and the bearing portion of the sleeve is fixed to a half-shaped bearing portion recessed in the cylinder head and to the cylinder head.
And a half-split shape that forms a pair with the bearing and constitutes the entire bearing
A variable valve timing mechanism for an internal combustion engine, which is rotatably held between a cam cap formed with a bearing portion and a bearing. 2. A camshaft for driving an intake valve or an exhaust valve, a hub fitted to one end of the camshaft, and a substantially hollow cylindrical member disposed so as to surround an outer surface of the hub. A sleeve, a relative rotation angle difference providing means interposed between the hub and the sleeve to provide a relative rotation angle difference therebetween, and the sleeve fitted to a bearing recessed in a cylinder head. A valve timing variable mechanism for an internal combustion engine, comprising: an oil seal interposed in a gap between an outer peripheral surface and a front end portion of the cylinder head; and an input member provided integrally with the sleeve to impart rotational motion to the sleeve. In the assembling method, the piston, the spring, and the camshaft having the hub fitted to one end thereof are assembled to a sleeve provided with a bearing portion on an outer peripheral surface thereof. Was followed, of the sleeve is placed to be bearing portion half shaped bearing portion of the cylinder head, half the bearing portion so as to cover half shaped of the sleeve
After the cam cap forming the bearing portion is fixed to the bearing portion of the cylinder head and the sleeve is sandwiched, oil is injected from the front side of the cylinder head into the gap between the outer peripheral surface of the sleeve and the front end of the cylinder head. A method for assembling a variable valve timing mechanism for an internal combustion engine, wherein a seal is fitted and an input member is fixed to a front end of the sleeve after that.