JPH04209908A - Assembling method of valve system in engine - Google Patents

Abstract

PURPOSE:To eliminate position adjusting of a driving wheel provided between cams so as to obtain good assembling property by supporting the driving wheel provided between the cams which is inserted into a cam shaft, inside a cylindrical part formed of a bearing cap and a cylinder head, before the mechanism main body of a variable valve timing mechanism is mounted on the cam shaft. CONSTITUTION:In a case where a valve system is assembled on a cylinder head 3, firstly a lock nut 14 and a driving wheel 12 provided between cams of an exhaust side are inserted into the end part of a cam shaft 5 for exhaust, and then the cam shaft 5 for exhaust is set temporarily to the cylinder head 3. A bearing cap 18 is assembled on the end part bearing part 21a of the cylinder head 3, and a cylindrical part G is formed of the bearing cap 18 and the end part bearing part 21a, while the top end part of the boss part 12a of the driving wheel 12 provided between the cams of the exhaust side is supported on the cylindrical part G. After that, the mechanism main body 15 of a variable valve timing mechanism 16 is inserted into the inner circumference side of the bearing cap 18 on the top end part of the cam shaft 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of assembling a valve train for an engine in which a variable valve timing mechanism is attached to a camshaft of the engine.

(Prior art) Conventionally, a variable valve timing mechanism is attached to the camshaft drive mechanism of an engine's valve train, and the valve timing of the exhaust valve or intake valve is adjusted by changing the rotational phase of the crankshaft and camshaft. For example, a technology that changes according to the operating state is disclosed in Japanese Patent Application Laid-open No. 12-1 [12-1].
This is known as seen in Japanese Patent No. 91606.

Furthermore, regarding driving the camshafts, there is also a technology in which only one camshaft is driven from the crankshaft by a timing belt, etc., and the other camshaft is driven from one camshaft via a gear between cams, etc. Are known.

(Problem to be Solved by the Invention) However, when assembling the above-mentioned valve train, a variable valve timing mechanism is disposed on the end side of the camshaft, and the inner part of the variable valve timing mechanism is attached to the other camshaft. The assembly of inter-cam drive wheels that transmit power to the cams is complicated due to the work involved and the relationship with the seal structure.

In other words, the variable valve timing mechanism and inter-cam drive wheel are assembled on the camshaft in advance, and then the camshaft is attached to the cylinder head.In the case where the camshaft is fixed with a bearing cap, the variable valve timing mechanism and the inter-cam drive wheel are attached to the camshaft. It is recommended that the variable valve timing mechanism be assembled after the camshaft has been set in the cylinder head and secured with the bearing cap, due to the ease of assembling the wheels and the placement of the seal member on the bearing. There is a problem if you do. The inter-cam driving wheel is fixed to the main body of the variable valve timing mechanism, and since the inter-cam driving wheel is arranged inside the bearing cap, the inner peripheral side of the inter-cam driving wheel that has been inserted into the camshaft in advance The work of inserting the main body of the variable valve timing mechanism into the cam system is particularly complicated and inefficient because it must be performed while aligning the driving wheels between the cams to concentric positions.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a method for assembling an engine valve train, which improves the ease of assembling a cam-to-cam driving wheel and a variable valve timing mechanism. .

(Means for Solving the Problems) In order to achieve the above object, a method for assembling a valve train of the present invention provides an inter-cam drive that transmits power to one camshaft of a DOHC engine and to the other camshaft. In addition to providing a variable valve timing mechanism capable of changing valve timing, the cam is inserted into one of the camshafts with the inter-cam drive wheel and a lock nut for fixing the inter-cam drive wheel. The shaft is placed on the cylinder head, a bearing cap is attached to the bearing part of the cylinder head, and the driving wheel between the cams is supported in the cylindrical part formed by the bearing cap and the cylinder head, and then the mechanism of the variable valve timing mechanism is installed. The main body is inserted between the camshaft and the bearing cap, the inter-cam drive wheel is attached to the mechanism main body by tightening the nut, and the variable valve timing mechanism is attached to the end of the camshaft.

Furthermore, before inserting the mechanism body of the variable valve timing mechanism into the camshaft, a ring-shaped sealing member for sealing with the mechanism body is inserted into the ring-shaped recess formed by the bearing cap and the cylinder head. It is preferable to keep them fitted.

(Operations and Effects) In the method for assembling a valve train as described above, before mounting the mechanism body of the variable valve timing mechanism on the camshaft,
By supporting the cam-to-cam drive wheel inserted through the camshaft in the cylindrical portion formed by the bearing cap and cylinder head, there is no need to adjust the position of the cam-to-cam drive wheel when assembling the mechanism body, and a good performance is achieved. Installation can be done to get the job done.

Furthermore, before inserting the mechanism body of the variable valve timing mechanism into the camshaft, fitting a seal member to a bearing cap attached to the cylinder head,
This seal part shrine can be installed in an appropriate state, and good sealing performance can be ensured while improving assembly performance.

(Example) The present invention will be described in detail below with reference to the drawings.

Fig. 1 shows a schematic front configuration of a V-type engine with a biased valve train to which an assembly method according to an embodiment of the present invention is applied, and Fig. 2 shows a valve train of the first bank (left side in Fig. 1). FIG. 3 shows the cross-sectional side structure of the main part of the device, and FIG. 3 shows the cross-sectional planar structure of the main part.

In the V-type engine 1, a first cylinder head 3 and a second cylinder head 4 are arranged obliquely on a cylinder block 2 at the lower center, forming first and second banks IA and IB. Two camshafts 5 and 6 are installed in each as a valve train. The center side has an intake camshaft 6, and the outside side has an exhaust camshaft 5, which are driven by a crankshaft 7 via a timing belt 8. That is, the crank pulley 7a at the end of the crankshaft 7 disposed at the bottom of the cylinder block 2, and the driving force transmission wheels 9, 9 (cam pulleys) at the ends of the camshafts 5, 5 on the exhaust side of both banks 1A, 1B. ) is connected to the timing belt 8 via idlers lla to 11d, and the driving force is transmitted to the intake side camshaft 6 by inter-cam drive wheels 12 and 13 (inter-cam gear), synchronizing with engine rotation. It is driven by

In the case of the illustrated engine, each cylinder is provided with four valves (two intake valves and two exhaust valves), and for example, the exhaust valve 10 (see FIG. 2) is driven to open and close by each cam portion 5a of the exhaust side camshaft 5. be done.

To be more specific, the driving force transmitting wheel 9 is installed on the outer periphery of the shaft portion at the tip of the gas phase camshaft 5, or the driving force transmitting wheel 9 The intake valve 4 has variable opening/closing timing of the exhaust valve 10 by changing the rotational phase.
The variable valve timing mechanism 16 is attached to the mechanism main body 15 side of the variable valve timing mechanism 16 that changes the overlap period with the valve timing mechanism 16.

Further, an exhaust-side inter-cam drive wheel 12 disposed around the outer periphery of the exhaust camshaft 5 is attached to the rear end side of the mechanism body 15 by fastening a lock nut 14. An intake-side cam-to-cam drive wheel 13 that meshes with the exhaust-side cam-to-cam drive wheel 12 is fixed to the end of the intake-side camshaft 6 to transmit rotational force. A friction gear 17 for reducing backlash is attached to the intake-side inter-cam drive wheel 13.

The exhaust side and intake side camshafts 5 and 6 as described above are mounted on the upper surface of the cylinder head 3, and the cylinder head 3 has a structure for supporting the front end of each camshaft 5 and 6. Bearing caps 18 (see FIG. 2) are attached from above to the end bearing parts 21a and 21b on both sides, and An intermediate bearing portion 22 is provided to support the cam cap 19, and a cam cap 19 is attached to the intermediate bearing portion 22.

The exhaust side end bearing portion 21a supports the exhaust camshaft 5 via the mechanism body 15 of the variable valve timing mechanism 16, and the mechanism body 15 has a wide flange-like front portion. The rear portion extends in a cylindrical shape along the exhaust camshaft 5, and the middle portion of this cylindrical portion is formed as a journal portion 15a supported by the bearing portion formed by the end bearing portion 21a and the bearing cap 18,
The front step portion of the journal portion 15a abuts the bearing portion formed by the end bearing portion 21a and the bearing cap 18 from the front. Further, the exhaust side inter-cam drive wheel 12 is fitted behind the journal portion 15a, and a threaded portion 15b (screw) for threading the lock nut 14 is formed on the outer periphery of the rear end portion. .

On the other hand, the exhaust side inter-cam drive wheel 12 is connected to the mechanism main body 1.
The boss part 12a has a center-side boss part 12a that is fitted behind the journal part 15a of the mechanism body 15, and the boss part 12a extends forward in a cylindrical shape, and the tip part touches the rear end step part of the journal part 15a of the mechanism main body 15. It is fixed in a state of contact. Further, the tip of the boss portion 12a of the exhaust-side inter-cam drive wheel 12 is connected to the bearing cap 18 and the end bearing portion 21 of the cylinder head 3.
It is inserted into a cylindrical portion G formed in a step shape on the inner circumferential side of the rear end of a. The above structure restricts thrust movement of the mechanism main body 15 back and forth with respect to the end bearing portion 21a of the cylinder head 3.

Furthermore, a positioning pin 23 and a groove 12b are formed between the mechanism main body 15 and the boss portion 12a of the exhaust-side inter-cam drive wheel 12 to match the mutual phases. That is, a positioning pin 23 is provided upright on the rear outer periphery of the mechanism body 15, and a vertical groove 12b that engages with the positioning pin 23 is formed at a predetermined position in the boss portion 12H of the exhaust-side inter-cam drive wheel 12. There is.

Further, a ring-shaped seal member 24 is inserted into the ring-shaped recess F on the inner peripheral side of the front end of the bearing cap 18 and the end bearing portion 21a of the cylinder head 3. Furthermore, a flange portion 18a extending forward is connected to the bearing cap]8, and a belt cover 41 that covers the front of the cylinder head 3 is disposed at the tip of the flange portion 18a. On the other hand, a bottom cover 42 is disposed from the rear end of the bearing camp 18 to cover the upper part of the cylinder head 3.

At the distal end shaft portion of the exhaust camshaft 5 located inside the mechanism main body 5 as described above, the support that comes into contact with the distal end shaft portion of the camshaft 5 or the inner surface of the mechanism main body] 5 is the portion 5.
A predetermined width is formed between the journal portion 15a of the mechanism body] 5 and the threaded portion 5b into which the lock nut 14 is threaded.

That is, the bearing portion 5b is in contact with the inner circumferential surface of the mechanism main body 15 with a small clearance, and the other tip shaft portions of the camshaft 5 are formed to have a small diameter so that the clearance is larger than this.

Note that a hexagonal portion 5C is formed in the middle of the exhaust camshaft 5 so that it can be rotated with a tool.

Here, the variable valve timing mechanism 16 is hydraulically operated, and is supplied with engine lubricating oil from an oil pump (not shown) of the engine or from the other end of the camshaft 5 depending on the operating condition. The detailed structure of the variable valve timing mechanism 16 will be explained.

A cylindrical front case 25 is fixed to the flange-shaped front end of the mechanism main body 15 into which the distal end shaft of the exhaust camshaft 5 is fitted, and the driving force transmission wheel 9 (
The inner circumference of the cam pulley is fixed. front case 2
A ring member 26 is attached to the tip of the ring member 5, and a lid member 38 is fixed to the tip of the ring member 26.

Further, a cylindrical spacer 27 is integrally fixed to the tip of the exhaust camshaft 5 with a mounting bolt 29 via a stopper member 28. This mounting bolt 29 attaches the variable valve timing mechanism 16 to the camshaft 5.

A ring-shaped piston 30 is installed inside the front case 25 between it and the spacer 27. The piston 30 has a structure in which it is divided into two parts in the axial direction, and both parts are fixed to each other by a plurality of pins 31 arranged at equal intervals in the circumferential direction. Helical splines in opposite directions are formed on the inside and outside of the piston 30.

A helical spline is formed on the outside of the spacer 27 corresponding to the helical spline on the inside of the piston 30, and a helical spline is formed on the inner periphery of the front case 25 in correspondence to the spline on the outside of the piston 30. Further, the piston 30 is urged toward the distal end side by a spring 36 installed between the piston 30 and the end surface of the mechanism main body 15.

Furthermore, a knock pin 32 and a groove 27a are formed between the exhaust camshaft 5 and the spacer 27 of the variable valve timing mechanism 16 to match the mutual phases. That is, a knock pin 32 that projects in the axial direction is provided upright at the tip of the camshaft 5, and a vertical groove 27a that engages with the knock pin 32 is formed at a predetermined position in the inner peripheral portion of the spacer 27.

On the other hand, an oil passage (not shown) is formed in the exhaust camshaft 5 along its axis, and passes through the inside of the mounting bolt 29 and passes through the groove of the ring member 26 from inside the tip to the head of the piston 30. When the piston 30 compresses the spring 36 and moves in the axial direction when hydraulic pressure is introduced, the spacer 27 that fits with the helical splines in the opposite direction formed on the inner and outer circumferences of the piston 30 is connected to the front case. 25, that is, rotates relative to the driving force transmission wheel 9. This changes the phase between the exhaust camshaft 5 and the driving force transmission wheel 9, that is, the valve timing.

Next, to explain how to assemble the above-mentioned valve train to the cylinder head 3, first, after inserting the lock nut 14 and the exhaust side cam drive wheel 12 into the end of the exhaust camshaft 5, the exhaust camshaft 5 to cylinder head 3
Temporarily set to . Then, the exhaust side cam drive wheel 12
After performing phase alignment between the intake camshaft 6 and the intake side inter-cam drive wheel 13 fixed to the intake camshaft 6, the intake camshaft 6 is set in the cylinder head 3. The above phase matching is
Drive wheel 12 between exhaust side cams and drive wheel 13 between intake side cams
This is done by aligning the punch marks formed on the .

Subsequently, the end bearing portions 21a, 21 of the cylinder block 3
At the same time, a cam cap 19 is attached to the intermediate bearing portion 22, and each of the camshafts 5.6 is fixed to the cylinder head 3. At this time, the lock nut 14 and the exhaust-side inter-cam drive wheel 12 are located at the rear of the bearing cap 18, but the assembled bearing cap 18 and the end bearing portion 21a of the cylinder block 3 allow the bearing cap 18 to A cylindrical portion G is formed on the rear side, and the tip of the boss portion 12a of the exhaust-side inter-cam drive wheel 12 is inserted into this cylindrical portion G, and is concentrically arranged with a gap around the outer periphery of the camshaft 5. I will support you.

At this time, a certain amount of clearance is set between the cylindrical portion G and the outer periphery of the boss portion 12a, and the inter-cam drive wheel 1
2 is slightly movable and is provided so as to absorb errors when inserting the mechanism main body 15, which will be described later.

Similarly, a ring-shaped recess F is formed on the front side of the bearing cap 18 by the bearing cap 18 and the end bearing part 21a of the cylinder block 3, and a ring-shaped seal member 24 is inserted into the ring-shaped recess F from the front. (Oil seal) is press-fitted.

Thereafter, the mechanism body 15 of the variable valve timing mechanism 16 is inserted into the tip of the camshaft 5 and into the inner circumferential side of the bearing cap 18. Since the exhaust side inter-cam drive wheel 12 is concentrically supported at the tip of the mechanism main body 15,
It can also be easily inserted inside. At that time, the mechanism body 15
While rotating the mechanism body 15, that is, the variable valve timing mechanism 16, so that the positioning pin 23 at the tip of the exhaust side cam drive wheel 12 is engaged with the groove 12b of the exhaust side cam drive wheel 12, the phase alignment with the exhaust side cam drive wheel 12 is performed. When the lock nut 14 can be screwed into the screw of the threaded portion 15b at the tip by inserting the mechanism body 15, the lock nut 14 is temporarily tightened.

Further, after the mechanism main body 15 is inserted and the phase is aligned with the exhaust side inter-cam drive wheel 12, the knock pin 32 at the tip of the exhaust camshaft 5 comes into contact with the spacer 27, and the hexagonal part 5C of the camshaft 5 is brought into contact with the tool. While rotating the exhaust camshaft 5 and the variable valve timing mechanism 16, the exhaust camshaft 5 and the variable valve timing mechanism 16 are brought into phase by engaging the knock pin 32 with the filler 27a of the spacer 27. At that time, the lid member 38, mounting bolt 29, and stopper member 28 of the variable valve timing mechanism 16 are removed, and the knock pin 32 and groove 27a are removed.
This is to visually check the engagement from the front, and after confirming the engagement between the two, tighten the mounting bolt 29 via the stopper member 28.
Tighten.

Then, a jig is set on the lock nut 14 to fix the rotation of the lock nut 14. Thereafter, the mounting bolts 29 are fully tightened to a predetermined torque using a torque wrench, thereby attaching the variable valve timing mechanism 16 to the camshaft 5, and the lock nut 14 is also fully tightened to tighten the drive wheel 12 between the exhaust side cams. is fastened to the mechanism body 15. Subsequently, the lid member 38 is attached to complete the assembly.

The hydraulic pressure is introduced under the control of a controller that operates a valve mechanism (not shown), and the hydraulic pressure is introduced into the variable valve timing mechanism 16 in a high rotation and high load region based on the engine load (for example, throttle opening) and engine speed. When this hydraulic pressure is introduced, the opening/closing timing of the exhaust valve is delayed to increase the overlap period during which both the exhaust valve and the intake valve are open. In addition, the introduction of hydraulic pressure to the variable valve timing mechanism 16 is stopped in the low-load, low-speed region, and the opening/closing timing of the exhaust valve is advanced to shorten the overlap period in which both the exhaust valve and the intake valve are open at the same time.

In the above embodiment, the variable valve timing mechanism 16 is installed on the exhaust camshaft 5 to change the opening and closing timing of the exhaust valve, but this variable valve timing mechanism is installed on the intake camshaft 6. The opening/closing timing of the intake valve may also be changed.

[Brief explanation of the drawing]

FIG. 1 is a schematic front view of a V-type engine equipped with a valve train to which an assembly method according to an embodiment of the present invention is applied; FIG. 2 is a cross-sectional side view of essential parts of a first bank valve train; FIG. 3 is a sectional plan view of the main part thereof. 1... Engine, 3, 4... Cylinder head, 5゜6... Camshaft, 9... Drive power transmission wheel, 12゜13...・Drive wheel between cams, 1
4... Lock nut, 15... Mechanism body, Yu 6... Variable valve timing mechanism, 21a
... Bearing part, 18 ... Bearing cap, 24
... Seal member, F ... Ring-shaped recess, G ... Cylindrical portion. Figure 2 Figure 3 j

Claims (2)

[Claims] (1) In a valve train for a DOHC engine, in which one camshaft is provided with an inter-cam drive wheel that transmits power to the other camshaft, and a variable valve timing mechanism capable of changing valve timing is provided. ,
Place the camshaft on the cylinder head with the inter-cam drive wheel and the lock nut fixing the inter-cam drive wheel inserted into one of the camshafts, and attach the bearing cap to the bearing section of the cylinder head. The inter-cam drive wheel is supported in a cylinder formed by the bearing cap and the cylinder head, and then the mechanism body of the variable valve timing mechanism is inserted between the camshaft and the bearing cap, and the cam-to-cam drive wheel is supported in the mechanism body. A method of assembling a valve train for an engine, characterized in that a drive wheel is attached by tightening the lock nut, and a variable valve timing mechanism is attached to an end of a camshaft. (2) Before inserting the mechanism body of the variable valve timing mechanism into the camshaft, a ring-shaped seal member is installed in the ring-shaped recess formed by the bearing cap and the cylinder head to seal between the mechanism body and the mechanism body. 2. The method of assembling a valve train for an engine according to claim 1, further comprising the step of fitting the two parts.