JPH082411Y2 - Cylinder head of internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a cylinder head of an internal combustion engine, in particular, a cylinder head having a hydraulic path for a variable valve timing mechanism.

2. Description of the Related Art A cam pulley or cam sprocket around which a timing belt or cam chain is wound is rotatably attached to a cam shaft, and a hydraulic actuator that uses a helical gear or the like causes the cam pulley to rotate relative to each other by a predetermined angle. Various variable valve timing mechanisms capable of changing the phase with respect to the crank angle in two ways have been proposed, and some of them have been put to practical use (for example, see Japanese Patent Laid-Open No. 55-96311).

In this case, as shown in the above publication, the hydraulic actuator is arranged at the end of the cam shaft, and the lubricating oil pumped from the hydraulic pump of the engine passes through the cam bearing portion of the cylinder head. The oil is introduced into the oil passage inside the camshaft and supplied to the actuator. Further, the switching of the valve timing, that is, the switching of whether or not to operate the actuator is performed by relieving the hydraulic pressure on the cylinder head side. That is, one end communicates with the oil supply path,
And the other end is equipped with an oil discharge path open to the outside,
In addition, the electromagnetic relief valve opens and closes it in ON and OFF.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the device described in the above publication, the relief hole at the tip of the oil discharge path is open toward the inside of the front end wall of the cylinder head, and the relief oil is discharged to the upper surface of the cylinder head. Will be.

Therefore, if the actuator becomes inoperable in the engine high-speed rotation range where the pump flow rate is large, a large amount of the relief oil may overflow to the upper surface of the cylinder head together with the lubrication oil used in the valve train. Yes, it is not preferable. The lubricating oil that has flowed out to the upper surface of the cylinder head flows down to the crankcase through an oil return passage that is vertically formed at the side of the cylinder head and the cylinder block, but the passage area of this oil return passage increases or The increase may cause a decrease in rigidity of the cylinder block and the like.

Therefore, the present invention is directed to an oil supply path for supplying lubricating oil from a hydraulic pressure source to a variable valve timing mechanism actuator arranged at an end of a camshaft via a cam journal, and an internal cylinder head. An internal combustion engine having an oil discharge path formed at 1, one end communicating with the oil supply path and the other end opened as a relief hole, and an electromagnetic relief valve for opening and closing the oil discharge path inside the cylinder head. In the cylinder head, the relief hole is formed in the cylinder head, and is opened toward the front end chain chamber, and the discharged lubricating oil flows down along the side wall surface of the chain chamber. It is characterized by being placed on the side.

Action In the above configuration, the lubricating oil that is relieved when the actuator is not operating is discharged into the chain chamber through the relief hole. Then, it flows down to the lower crankcase through the cam chain outer peripheral side of the chain chamber.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing a front end portion of a cylinder head 1 according to the present invention, and FIG. 2 is a sectional view of a main part taken along line II-II thereof.

The cylinder head 1 is formed by casting an aluminum alloy or the like, has a side wall 2 formed so as to surround the periphery thereof, and has cam bearing portions 3 formed at a plurality of positions so as to connect the side walls 2 to each other. Are formed. The example shown is
A camshaft is provided on each of the intake side and the exhaust side, which is provided with a DOHC type valve mechanism, but the variable valve timing mechanism is provided only on the intake side camshaft 4.

At the front end of the cylinder head 1, the cam chain 5
The chain case portion 6 for accommodating A and 5B (see FIG. 3) is
The front surface is recessed so that the front surface is open, the chain cover 7 is attached to the front surface, and the chain chamber 8 is defined between the both. The chain chamber 8 is connected to a chain chamber on the cylinder block side (not shown) and communicates with the crankcase as a whole.

At the front end of the intake side cam shaft 4 supported by the cam bearing portion 3, a cylindrical variable valve timing mechanism actuator 9 is arranged. This actuator 9
Is the inner cylinder 10 fixed to the flange portion 4a of the camshaft 4.
And an outer cylinder 11 having a sprocket part 11a on the periphery thereof are configured to be relatively rotated by a predetermined angle (for example, about 10 °) by hydraulic pressure, and are attached to the camshaft 4 by a fixing bolt 12. There is. Also, the actuator 9 works together with the cam chain 5 in the chain chamber 8
Housed within.

Next, a hydraulic system for the actuator 9 will be described. First, as an oil supply path, a tip of an oil gallery 13 is formed in the vicinity of the cam bearing portion 3 at the front end portion of the cylinder head 1 so as to face upward, and a cam bracket 14 to be combined with the cam bearing portion 3 is formed. On the bottom surface (see FIG. 2), that is, the joint surface with the cylinder head 1, approximately L
The oil supply passage 15 is formed in a V shape so as to guide the lubricating oil from the oil gallery 13 to the inner peripheral side of the cam bearing surface. The oil gallery 13 communicates with the discharge side of the hydraulic pump via an oil gallery on the cylinder block side (not shown).

Further, on the camshaft 4 side, an oil groove 16 and an oil hole 17 which coincide with the tip of the oil supply passage 15 are formed in the cam journal portion 4A. The oil hole 17 reaches an oil passage 18 formed between the inner circumference of the camshaft 4 and the outer circumference of the fixing bolt 12, and communicates with the inside of the actuator 9 through the oil passage 18.

On the other hand, as an oil discharge path, an oil discharge port 21 that coincides with the oil groove 16 is formed at the bottom of the cam bearing portion 3, and the oil discharge port 21 and a relief valve mounting hole on the side of the cylinder head 1 are formed. An oil passage 23 is formed to communicate with the relief valve 22, and a relief hole 24 is formed so as to intersect with the base of the relief valve mounting hole 22. An electromagnetic relief valve 25 that opens and closes between the oil passage 23 and the relief hole 24 is screwed into the relief valve mounting hole 22.

As shown in FIG. 4, the electromagnetic relief valve 25 has a cylindrical valve case 26 closely fitted to the tip of the relief valve mounting hole 22 and a slidably fitted inner circumference of the valve case 26. A bottomed cylindrical plunger 27 that opens and closes the communication hole 26a,
A solenoid 29 for pressing the plunger 27 via a rod 28 and a return spring 30 are provided. The plunger 27 inner peripheral side and the relief hole 24 side are the plunger 27
Through the communication hole 27a and the communication hole 26b of the valve case 26. That is, in the non-excited state of the solenoid 29, the plunger 27 is in the open position shown in FIG. 4 by the urging force of the return spring 30, and the oil passage 23 and the relief hole are
24 is kept in communication. Further, when the solenoid 29 is excited, the plunger 27 slides to close the communication hole 26a, so that the oil passage 23 and the relief hole 24 are not communicated.

The relief hole 24 is opened in the chain chamber 8 at the front end of the cylinder head 1 as shown in FIGS. 1 and 3. Specifically, as shown in FIG. 3, the cylinder head 1 is opened at the outer peripheral side of the loci of the cam chains 5A and 5B. Further, below the opening of the relief hole 24, the housing 32 of the chain tensioner 31 is located, and its upper surface 32a guides the lubricating oil discharged from the relief hole 24 toward the outer peripheral side of the chains 5A, 5B. Inclined to the outside.

In FIG. 3, reference numeral 33 is a cam sprocket for the exhaust side camshaft.

In the above-described configuration, the relatively high pressure lubricating oil pumped from the hydraulic pump (not shown) is constantly supplied from the oil gallery 13 to the oil passage 18 via the oil groove 16 of the cam journal portion 4A and the like. Therefore, when the electromagnetic relief valve 25 is turned on and the oil discharge path is blocked, the actuator 9
The hydraulic pressure acts on the inside of the camshaft 4 to change the phase of the camshaft 4 from the initial state by a predetermined angle.

On the other hand, if the electromagnetic relief valve 25 is in the OFF state,
As described above, since the oil discharge path from the oil discharge port 21 to the relief hole 24 is in a communication state, the lubricating oil guided to the oil path 18 is discharged to the low pressure side through the oil discharge path, No hydraulic pressure acts on the actuator 9. Therefore, the phase of the camshaft 4 is maintained in the initial state.

As described above, while the electromagnetic relief valve 25 is in the OFF state, the lubricating oil continues to be discharged from the relief hole 24, but this lubricating oil is discharged into the very wide chain chamber 8 and passes through the chain chamber 8. Since it flows down quickly to the crankcase side, it does not overflow onto the upper surface of the cylinder head 1. Moreover, the lubricating oil that has flowed out of the relief hole 24 is, as shown by the arrow in FIG. 3, the housing 32 of the chain tensioner 31.
It flows laterally along the upper surface 32a, and the chain case portion 6
Since it will run down along the side wall surface of the cam chain 5
Collisions with A and 5B can be avoided, and therefore increase in output loss and increase in oil splash will not occur.

Effect of the Invention As is apparent from the above description, in the cylinder head of the internal combustion engine according to the present invention, a large amount of lubricating oil that is relieved when the actuator for the variable valve timing mechanism is inoperative returns to the crankcase through the chain chamber. Therefore, even if the relief flow rate is high, it can be processed sufficiently,
A large amount of lubricating oil will not overflow onto the upper surface of the cylinder head as in the conventional case. Further, by setting the relief hole opening position on the outer peripheral side of the cam chain locus, it is possible to prevent the lubricating oil from colliding with the cam chain.

[Brief description of drawings]

FIG. 1 is a plan view showing an essential part of a cylinder head according to the present invention, FIG. 2 is a sectional view taken along the line II-II, and FIG. 3 is a sectional view showing a structure of a chain chamber interior, FIG. FIG. 4 is a sectional view of an electromagnetic relief valve. 1 ... Cylinder head, 4 ... Intake side camshaft, 8
...... Chain chamber, 9 ...... Actuator, 15 ...... Oil supply passage, 21 ...... Oil discharge port, 24 ...... Relief hole, 25 ......
Electromagnetic relief valve.

Claims (1)

[Scope of utility model registration request] 1. An oil supply path for supplying lubricating oil from a hydraulic pressure source to an actuator for a variable valve timing mechanism arranged at an end of a camshaft via a cam journal, and an inside of a cylinder head, one end of which is the oil. A cylinder head of an internal combustion engine comprising an oil discharge path communicating with a supply path and having the other end opened as a relief hole, and an electromagnetic relief valve for opening and closing the oil discharge path inside the cylinder head. Is formed in the cylinder head and opened toward the front end chain chamber, and is arranged on the outer peripheral side of the cam chain locus so that the discharged lubricating oil flows down along the side wall surface of the chain chamber. Cylinder head of internal combustion engine.