JP2002089359A - Dohc type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve supporting rigidity of an air intake camshaft and an exhaust camshaft while restraining increase in weight to the minimum on a DOHC type engine. SOLUTION: A timing chain 17 is wound around sprockets 15, 16 respectively fixed on end parts of the air intake camshaft 12 and the exhaust camshaft 13, and a chain guide 41 to guide this timing chain 17 is fixed on cam cap parts 26a, 26b to support the both camshafts 12, 13. It is possible to improve supporting rigidity of the air intake camshaft 12 and the exhaust camshaft 13 while reducing weight by forming a recessed part 26d in the center by connecting lower parts of the both cam cap parts 26a, 26b to each other by a connecting wall part 26c and connecting upper parts to each other by the chain guide 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timing chain which is wound around sprockets fixed to ends of an intake camshaft and an exhaust camshaft, respectively, and a chain guide for guiding the timing chain is provided on cam cap portions of the two camshafts. To a DOHC engine fixed to the engine.

[0002]

2. Description of the Related Art In a double overhead camshaft type (hereinafter referred to as DOHC type) engine, an intake camshaft and an exhaust camshaft are respectively held on a cylinder head by cam caps, and a timing chain is guided on the upper surfaces of these cam caps. A motor with a chain guide is known from Japanese Patent Application Laid-Open No. 8-177515.

[0003]

However, in the above conventional apparatus, since the cam cap of the intake camshaft and the cam cap of the exhaust camshaft are provided separately, not only the number of parts and the number of assembly steps are increased, but also If the width of the cam cap in the axial direction is not increased, there is a problem that the support rigidity of the intake camshaft and the exhaust camshaft is insufficient.

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to increase the support rigidity of an intake camshaft and an exhaust camshaft while minimizing an increase in weight in a DOHC type engine.

[0005]

According to the first aspect of the present invention, a timing chain is wound around sprockets fixed to ends of an intake camshaft and an exhaust camshaft, respectively. In a DOHC engine in which a chain guide for guiding the timing chain is fixed to the cam caps of the two camshafts, the cam cap of the intake camshaft and the cam cap of the exhaust camshaft are integrally connected by a connecting wall. A DOHC engine is proposed in which a camshaft holder is configured to form a camshaft holder and a concave portion is formed on a surface of the connecting wall portion facing the chain guide.

According to the above construction, the cam cap portion of the intake camshaft and the cam cap portion of the exhaust camshaft are integrally connected by the connecting wall to form a camshaft holder. Since the chain guide is fixed so as to bridge the recess formed in the intake camshaft and the camshaft holder, the camshaft holder is reduced in weight by the recess, and the rigidity is increased by connecting both cam caps with the connecting wall and the chain guide. The support rigidity of the exhaust camshaft can be improved.

According to the second aspect of the present invention,
In addition to the configuration of claim 1, the camshaft holder is fastened to the cylinder head with an outer bolt disposed outside the intake camshaft and the exhaust camshaft, and an inner bolt disposed inside the intake camshaft and the exhaust camshaft. A DOHC engine is proposed, wherein the camshaft holder and the chain guide are fastened together to the cylinder head, and the seat surface of the outer bolt is formed lower than the seat surface of the inner bolt.

According to the above construction, the camshaft holder and the chain guide are jointly fastened to the cylinder head with the common inner bolt, so that the number of bolts can be reduced. In addition, since the seating surfaces of the outer bolts arranged outside the two camshafts are formed lower than the seating surfaces of the inner bolts arranged inside, the camshaft holder can be downsized, and the engine can be downsized.

According to the third aspect of the present invention,
In addition to the structure of claim 1 or claim 2, a DOHC engine is proposed, wherein a tooth jump prevention plate is formed integrally with a chain guide.

[0010] According to the above configuration, since the tooth jump prevention plate is formed integrally with the chain guide, the rigidity of the chain guide is enhanced by the tooth jump prevention plate.

According to the invention described in claim 4,
In addition to the configuration of any one of claims 1 to 3, a DOHC engine is proposed, wherein the chain guide includes a resin sliding member that slides on the timing chain.

According to the above configuration, since the resin-made sliding member that is in sliding contact with the timing chain is provided on the chain guide, not only the occurrence of wear of the timing chain can be suppressed, but also the sliding between the chain guide and the timing chain. Dynamic resistance can be reduced.

The intake camshaft sprocket 15 and the exhaust camshaft sprocket 16 of the embodiment correspond to the sprocket of the present invention, and the bolts 28, 29 of the embodiment.
Corresponds to the inner bolt of the present invention, and the bolt 27,
30 corresponds to the outer bolt of the present invention.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

1 to 13 show a first embodiment of the present invention. FIG. 1 is a perspective view of an engine, FIG. 2 is an enlarged view in two directions of FIG. 1, and FIG. 3 is three directions of FIG. 4 is a sectional view taken along line 4-4 of FIG. 3, FIG. 5 is an enlarged view of a main part of FIG. 4, FIG. 6 is an operation explanatory view corresponding to FIG. 5, and FIG. 7 is 7-7 of FIG. 8 is an enlarged sectional view taken along line 8-8 of FIG. 3, FIG. 9 is an enlarged sectional view taken along line 10-10 of FIG. 3, FIG. 10 is an enlarged sectional view taken along line 10-10 of FIG. FIG. 12 is a sectional view taken along line 11-11 of FIG.
1 is a sectional view taken along line 12-12 of FIG. 1, and FIG.

As shown in FIG. 1, a DOHC type four-cylinder in-line engine E includes a crankshaft 11, an intake camshaft 12, and an exhaust camshaft 13, and a crank provided at an axial end of the crankshaft 11. A shaft sprocket 14, an intake camshaft sprocket 15 provided at a shaft end of the intake camshaft 12, and an exhaust camshaft sprocket 16 provided at a shaft end of the exhaust camshaft.
At this time, the timing chain 17 is wound. The timing chain 17 is driven by the crankshaft 11 in the direction of arrow a, and the intake camshaft 12 and the exhaust camshaft 13 rotate at half the speed of the crankshaft 11. Each cylinder has two intake valves 18, 18 driven by an intake camshaft 12, and two exhaust valves 19, 18 driven by an exhaust camshaft 13.
19 is provided. The two intake valves 18 and 18 have variable valve lifts and valve opening periods by a first valve operating characteristic variable mechanism V1 provided for each cylinder, and are provided at a shaft end of the intake camshaft 12. The valve timing is variable by the two-valve operating characteristic variable mechanism V2.

As shown in FIGS. 2 to 4, a cylinder head 23 is superimposed on the upper surface of the cylinder block 21 via a gasket 22, and is fastened with a plurality of bolts 24. A lower camshaft holder 25 also serving as a rocker arm shaft holder and an upper camshaft holder 26 are overlapped on the upper surface of the cylinder head 23, and are fastened to the cylinder head 23 together with four bolts 27, 28, 29, 30. Then, the upper portions of the lower camshaft holder 25 and the upper camshaft holder 26 are covered with the head cover 31. An intake rocker arm shaft 32 and an exhaust rocker arm shaft 33 are fixed to the lower cam shaft holder 25.
The intake camshaft 12 and the exhaust camshaft 13 are rotatably supported on the mating surface of the upper camshaft holder 5 and the upper camshaft holder 26.

As is apparent from FIGS. 5 and 7, an oil passage P1 connected to an oil pump (not shown) driven by the crankshaft 11 is formed in the cylinder head 23. The branched oil passage P2 communicates with a first hydraulic control valve 34 attached to a side surface of the cylinder head 23. An oil passage P6 extending from the first hydraulic control valve 34 into the cylinder head 23 extends upward, and is formed on the lower surface (the mating surface with the cylinder head 23) of the bulging portion 25a integral with the lower camshaft holder 25. It communicates with the road P7. An oil drain port 25b is formed at the downstream end of the oil passage P7 so as to face the engagement start portion between the exhaust camshaft sprocket 16 and the timing chain 17. The oil drain port 25b is slightly narrowed compared to the cross-sectional area of the oil passage P7, so that oil can be reliably supplied to the meshing start portion. A blind plug 35 is provided on the upper surface of the bulging portion 25a of the lower camshaft holder 25 located on an extension of the oil passage P6 extending upward in the cylinder head 23.

An oil passage P9 extending from the first hydraulic control valve 34 and extending horizontally in the cylinder head 23 communicates with an oil passage P10 extending upward, and an oil passage P10 opened on the upper surface of the cylinder head 23 is provided with a lower camshaft. It communicates with an oil passage P11 formed on the lower surface of the holder 25. The oil passage P11 of the lower camshaft holder 25 connects the lower camshaft holder 25 and the upper camshaft holder 26 to the cylinder head 2.
The oil passages P12 and P13 formed on the outer periphery of two bolts 28 and 29 of the four bolts 27 to 30 fastened to 3 respectively communicate with each other. An oil passage P12 on the outer periphery of the bolt 28 communicates with an oil passage 33a formed in the exhaust rocker arm shaft 33 in the axial direction, and an oil passage P1 on the outer periphery of the bolt 29.
Numeral 3 communicates with an oil passage 32 a formed in the inside of the intake rocker arm shaft 32 in the axial direction, and communicates with an oil jet 36 provided in the lower camshaft holder 25.

As is apparent from FIG. 8, the oil jet 36 has an oil jet main body 37 having a nozzle hole 37a.
And a mounting bolt 39 for fixing the oil jet main body 37 to the lower camshaft holder 25 via a seal member 38. Inside the mounting bolt 39, a relief valve 40 whose upstream side communicates with the oil passage P12 on the outer periphery of the bolt 28 and whose downstream side communicates with the nozzle hole 37a of the oil jet main body 37 is housed. Oil jet body 37
The nozzle hole 37a is positioned so as to be directed to the engagement start portion between the intake camshaft sprocket 15 and the timing chain 17 by fitting the positioning projection 37b formed on the lower camshaft holder 25 into the positioning hole 25c formed on the lower camshaft holder 25. You.

The oil jet 36 is arranged in a dead space between the lower camshaft holder 25 and the exhaust camshaft sprocket 16 and is arranged so as to fit within the outer diameter of the exhaust camshaft sprocket 16. In addition, the influence of the oil jet 36 on other members can be minimized. In particular, since the oil jet 36 is disposed by effectively utilizing the dead space (space) on the back surface of the exhaust camshaft sprocket 16 in which the second valve operating characteristic variable mechanism V2 is not provided, the engine E is mounted by mounting the oil jet 36. It is possible to minimize an increase in the size and hindrance of attachment of other members. As shown in FIG. 2, a lightening hole 16 a formed in the exhaust camshaft sprocket 16 for reducing the weight faces the oil jet 36. That is, since the oil jet 36 faces the lightening hole 16a formed in the exhaust camshaft sprocket 16, the mounting state of the oil jet 36 and forgetting to attach the oil jet 36 can be easily confirmed through the lightening hole 16a.

If the entire mounting bolt 39 of the oil jet 36 is arranged within the lightening hole 16a of the exhaust camshaft sprocket 16, the mounting bolt 39 can be attached and detached through the lightening hole 16a. Maintainability is improved. The oil jet 36 is located within the thickness of the lightening hole 16a of the exhaust camshaft sprocket 16.
By arranging the whole, the oil jet 36 can be attached and detached through the lightening hole 16a, thereby improving the maintainability.

As is apparent from FIGS. 3, 4 and 8, two bolts 28, 29 (an inner bolt disposed inside the intake camshaft 12 and the exhaust camshaft 13) for fastening the upper camshaft holder 26 are provided. ), The chain guide 41 is fastened together. The two bolts 28, 2 for fastening the upper camshaft holder 26
9 are two bolts 27, 30 arranged outside thereof
(Outer bolts disposed outside the intake camshaft 12 and the exhaust camshaft 13) are offset by a distance δ in a direction away from the oil jet 36. Thereby, the interference with the bolts 28 and 29 can be avoided to secure the mounting space for the oil jet 36, and the rigidity for supporting the oil jet 36 can be increased.

The two offset bolts 28,
One of the bolts 28 of the exhaust camshaft 1
3 overlaps with the oil jet 36 when viewed in the axial direction, so that not only the size of the lower camshaft holder 25 can be reduced, but also the support rigidity of the exhaust camshaft 13 is improved. This is because if the oil jet 36 is arranged at a position closer to the bolt 29 than the bolt 28 (on the side far from the exhaust camshaft 13), the oil jet 36
The size of the lower camshaft holder 25 is increased by the space. Conversely, if the oil jet 36 is disposed closer to the exhaust camshaft 13 than the bolt 28, it is necessary to form a mounting hole for the oil jet 36 near the exhaust camshaft 13 support surface of the lower camshaft holder 25. There is a possibility that the support rigidity of the camshaft 13 is reduced. Further, an oil jet 3 is provided around the bolt 28.
Since the oil passage P12 connected to 6 is formed, the configuration of the oil passage for supplying oil to the oil jet 36 is simplified, and the oil passage can be shortened.

The chain guide 41 has a chain guide main body 42 made of a metal plate, and a sliding member 43 made of synthetic resin provided on the lower surface of the distal end portion slidably contacts the upper surface of the timing chain 17. This sliding member 43
Accordingly, the timing chain 17 can be guided and the run-out can be suppressed, the wear of the timing chain 17 can be suppressed, and the sliding resistance between the chain guide 41 and the timing chain 17 can be reduced. A pair of tooth skipping prevention plates 42a and 42b are integrally formed on both ends in the longitudinal direction of the chain guide body 42. One of the tooth skipping prevention plates 42a covers the upper portion of the engagement start portion between the intake camshaft sprocket 15 and the timing chain 17 to prevent tooth skipping of the timing chain 17, and the other tooth skipping prevention plate 42b is connected to the exhaust camshaft sprocket 16 The timing chain 17 covers the upper end of the meshing end portion of the timing chain 17 to prevent tooth skipping of the timing chain 17. Double-tooth jump prevention plates 42a, 42
Since the rigidity of the chain guide 41 is improved by providing b, the rigidity of supporting the intake camshaft 12 and the exhaust camshaft 13 is further improved.

Since the tooth jump prevention plates 42a and 42b are formed at both ends of the sliding member 43 made of synthetic resin, the durability of the sliding member 43 is improved even though the sliding member 43 is made of synthetic resin. Is improved.

The upper camshaft holder 26 includes a cam cap 26a for holding the intake camshaft 12, a cam cap 26b for holding the exhaust camshaft 13,
Connecting wall 2 connecting both cam caps 26a, 26b
6c, between the two bolts 28 and 29 and the connecting wall 26c, that is, on the surface of the connecting wall 26c facing the chain guide 41, a U-shaped recess 2 for weight reduction.
6d is formed. And both cam cap portions 26a, 2
The lower ends of 6b are connected by a connecting wall portion 26c and the upper ends thereof are connected by a chain guide 41. That is, the two cam cap portions 26a and 26b and the connecting wall portion 2
Since the chain guide 41 is attached so as to bridge the concave portion 26d formed between the upper and lower portions 6c, the cam cap portions 26a and 26b are formed by the connecting wall portion 26c and the chain guide 41 while reducing the weight of the upper camshaft holder 26.
And sufficient rigidity can be secured, and the supporting rigidity of the intake camshaft 12 and the exhaust camshaft 13 can be improved.

As described above, the lower camshaft holder 2
5 and two of the four bolts 27 to 30 for fastening the upper camshaft holder 26 to the cylinder head 23.
Since the chain guide 41 is fastened together using the bolts 28 and 29, the number of components is reduced, and the rigidity of the chain guide 41 is improved. Of the four bolts 27 to 30, the height of the seat surface of the two inner bolts 28 and 29 for fixing the chain guide 41 is restricted by the height of the timing chain 17.
The bearing surfaces of the two outer bolts 27 and 30 that do not contribute to the fixing of the timing chain 17 can be lowered without being restricted by the height of the timing chain 17. Accordingly, both ends of the upper camshaft holder 26 are lower than the bearing surfaces of the bolts 28 and 29, so that the size of the head cover 31 can be reduced.

Returning to FIG. 4, the filter housing 45 is fixed to the side surface of the cylinder head 23 with bolts 44... The oil passage P14 branched from the oil passage P1 of the cylinder head 23 is connected to the first valve operating characteristic variable mechanism V1. It extends in the separating direction and communicates with the oil passage P16 of the cylinder head 23 via the filter 46 in the filter housing 45 and the oil passage P15. The oil passage P16 is inside the cylinder head 23 (the cylinder head 23 on the timing chain 17 side).
The second hydraulic control valve 47 housed in the end wall) communicates with the second
The hydraulic control valve 47 is provided with an oil passage P formed in the cylinder head 23.
It communicates with the outer periphery of the intake camshaft 12 via oil passages P18a and P18b formed in the lower camshaft holder 25 and 17a and 17b. Filter housing 4
Reference numeral 5 is attached using the space on the side surface of the cylinder head 23 opposite to the side surface of the cylinder head 23 to which the first hydraulic control valve 34 is attached.

Next, the first hydraulic control valve 34 will be described with reference to FIG.
The structure of will be described.

The first hydraulic control valve 34 provided on the side surface of the cylinder head 23 has a valve hole 51a formed inside the valve housing 51.
Both ends of an oil passage P3 penetrating the lower part of the oil passage P2 communicate with the oil passages P2 and P4, and both ends of an oil passage P5 penetrating an intermediate portion of the valve hole 51a communicate with the oil passages P9 and P4. A drain port 51b is provided above the valve hole 51a.
Through the oil passage P6. A filter 52 is mounted at the inlet of the oil passage P3. A spool 53 housed inside the valve hole 51a has a pair of lands 53a, 53b.
And a groove 53c sandwiched between the lands 53a and 53b.
And an inner hole 53d extending in the axial direction, an orifice 53e penetrating the upper end of the inner hole 53d, and a groove 53f communicating the inner hole 53d with the drain port 51b.
The spool 53 is urged upward by a spring 54 housed at the lower end of the inner hole 53d, and comes into contact with a cap 55 that closes the upper end of the valve hole 51a. The oil passages P4 and P5 communicate with each other via the orifice 51c. Oil passage P
4 and the oil passage P8 are communicated and blocked by an ON / OFF solenoid 56.

Next, the structure of the first valve operating characteristic variable mechanism V1 will be described with reference to FIG.

A first operating characteristic variable mechanism V1 for driving the intake valves 18, 18 includes an intake rocker arm shaft 32.
The first and second low-speed rocker arms 57 and 58 pivotally supported by the low-speed rocker arm 57 and the high-speed rocker arm 59 sandwiched between the low-speed rocker arms 57 and 58. A sleeve 60, an intermediate portion of each rocker arm 57, 58, 59
A roller 63 rotatably supported by a sleeve 60 abuts against a low-speed intake cam 64 provided on the intake camshaft 12, and a roller 65 rotatably supported by the sleeve 61 is provided by a roller 65. The roller 67 rotatably supported on the sleeve 62 abuts on the high-speed intake cam 66 provided on the intake camshaft 12. The height of the high-speed intake cam 66 is higher than the height of the pair of low-speed intake cams 64 and 68 having the same profile.

A first switching pin 69, a second switching pin 70, and a third switching pin 71 are slidably supported inside the three sleeves 60, 61, 62.
Is biased toward the second switching pin 70 by a spring 73 disposed in a compressed state between the spring seat 72 and the spring seat 72 fixed to the sleeve 60, and stops at a position where it contacts the clip 74 fixed to the sleeve 60. At this time, the contact surfaces of the first switching pin 69 and the second switching pin 70 are located between the first low-speed rocker arm 57 and the high-speed rocker arm 59, and the second switching pin 70 and the third switching pin 7
The first contact surface is located between the high-speed rocker arm 59 and the second low-speed rocker arm 58. An oil chamber 58a formed inside the second low-speed rocker arm 58 is connected to an oil passage 32a formed inside the intake rocker arm shaft 32.
Communicate with

Oil passage 3 of intake rocker arm shaft 32
When the hydraulic pressure is not acting on 2a, the first to third switching pins 69 to 71 are at the positions shown in FIG. 9 and the first and second low-speed rocker arms 57 and 58 and the high-speed rocker arm 59 are provided.
Can swing freely. Therefore, a pair of intake valves 1
8 and 18 are driven with a low valve lift by a first low-speed rocker arm 57 and a second low-speed rocker arm 58, respectively. At this time, the high-speed rocker arm 59 separated from the first low-speed rocker arm 57 and the second low-speed rocker arm 58 idles independently of the pair of intake valves 18.

Oil passage 3 of intake rocker arm shaft 32
When hydraulic pressure acts on the oil chamber 58a from 2a, the first to third switching pins 69 to 71 move against the spring 73, and the first and second low-speed rocker arms 57 and 58 and the high-speed rocker arm 59 are integrated. Is done. As a result, the first and second low-speed rocker arms 5 are moved by the high-speed intake cam 66 having a high cam peak.
7, 58 and the high-speed rocker arm 59 are integrally driven, and a pair of intake valves 18, 18 connected to the first low-speed rocker arm 57 and the second low-speed rocker arm 58.
Are driven with a high valve lift. At this time, the pair of low-speed intake cams 64 and 68 are connected to the first and second low-speed rocker arms 5.
It moves away from 7,58.

Next, the second hydraulic control valve 4 will be described with reference to FIG.
The structure of No. 7 will be described.

Valve hole 2 formed in cylinder head 23
Five ports 82 to 86 are formed in a cylindrical valve housing 81 fitted to 3a, a central port 84 communicates with an oil passage P16, and ports 83 and 85 on both sides thereof are connected to a pair of oil passages P17a. , P17b respectively, and ports 82, 86 on both sides thereof are connected to a pair of drain oil passages P19.
a and P19b. A spool 90 having three grooves 87, 88, 89 formed on its outer periphery is slidably fitted to the valve housing 81, and a linear spring provided at the other end by the elastic force of a spring 91 provided at one end. It is urged toward the solenoid 92.

When the spool 90 is at the illustrated neutral position, the oil passages P16, P17a and P17b are all closed. When the spool 90 moves to the left from the neutral position by the duty controlled linear solenoid 92, the oil passage P16
Communicates with the oil passage P17a via the port 84, the groove 88 and the port 83, and the oil passage P17b communicates with the oil passage P via the port 85, the groove 89 and the port 86.
Communication with 19b. When the spool 90 moves to the right from the neutral position by the duty controlled linear solenoid 92, the oil passage P16 communicates with the oil passage P17b via the port 84, the groove 88 and the port 85, and the oil passage P17a communicates with the port 83 and the groove. 87 and port 8
2 and communicate with the oil passage P19a.

Next, based on FIG. 11 and FIG.
The structure of the variable valve operation characteristic mechanism V2 will be described.

The second valve operating characteristic variable mechanism V2 includes an outer rotor 93, and an inner rotor 96 fixed to the intake camshaft 12 by pins 94 and bolts 95. The outer rotor 93 includes a cup-shaped housing 97 in which the intake camshaft sprocket 15 is integrally formed on the outer periphery, an outer rotor body 98 that fits inside the housing 97, and an annular cover plate 99 that covers an opening of the housing 97. And they are joined together by four bolts 100. At the center of the housing 97, a support hole 97a is formed.
The outer rotor 93 is rotatably supported on the intake camshaft 12 by fitting the outer periphery of the intake camshaft 12 to the outer periphery of the intake camshaft 12.

Four concave portions 98a and four convex portions 98b are formed alternately on the inner periphery of the outer rotor main body 98, and four vanes radially formed on the outer periphery of the inner rotor 96. 96 fit into the four recesses 98a, respectively. Convex part 98b of outer rotor body 98
A seal member 101 provided at the tip of the abutment comes into contact with the inner rotor 96, and a vane 96a of the inner rotor 96 is provided.
The seal members 102 provided at the distal ends of the abutment contact the outer rotor body 98, so that the four advance chambers 10 are provided between the outer rotor body 98 and the inner rotor 96.
3 and four retard chambers 104 are defined.

The pin hole 9 formed in the inner rotor 96
A stopper pin 105 is slidably supported by 6b, and an arc-shaped long groove 97b with which the tip of the stopper pin 105 can engage is formed in the housing 97 of the outer rotor 93. The stopper pin 105 is urged by a spring 106 in a direction to separate from the long groove 97b, and an oil chamber 107 is formed at the back of the stopper pin 105. The stopper pin 105 is moved by the elastic force of the spring 106 to form the long groove 9.
7b, the outer rotor 93
And the inner rotor 96 can rotate relative to each other within a range of an angle α (for example, 30 °) until the vanes 96 a of the inner rotor 96 reach one end of the recess 98 a of the outer rotor 93. When the oil pressure is supplied to the oil chamber 107 and the stopper pin 105 is engaged with the long groove 97b, the angle between the outer rotor 93 and the inner rotor 96 until the stopper pin 105 reaches one end of the long groove 97b from the other end. Relative rotation is possible in the range of β (for example, 20 °).

A pair of oil passages P18a and P18b formed in the lower camshaft holder 25 are connected to the intake camshaft 1
Communicate with the advance chambers 103 and the retard chambers 104 via a pair of oil passages 12a, 12b formed in the inside 2 and oil passages 96c, 96d formed in the inner rotor 96, respectively. Therefore, the advance chamber 10 through the second hydraulic control valve 48
When the hydraulic pressure is supplied to the intake camshafts 12, the low-speed intake cams 64, 68 and the high-speed intake cam 66 advance the intake camshaft 12, and the valve timing of the intake valves 18, 18 is advanced. Further, the retard chamber 10 is controlled via the second hydraulic control valve 48.
Are supplied to the intake camshaft 12, the low-speed intake cams 64, 68 and the high-speed intake cam 66 are retarded, and the valve timing of the intake valves 18, 18 is delayed.

The second lower camshaft holder 25 viewed from the second variable valve operating characteristic mechanism V2 side is provided with an oil passage P1.
3 (see FIG. 4) is formed. The oil passage P20 is formed with an oil passage 12c formed inside the intake camshaft 12, and oil passages 95a and 95b formed inside the bolt 95. Through the oil chamber 107 facing the head of the stopper pin 105.

In this embodiment, no variable valve operating characteristic mechanism is provided on the exhaust camshaft 13 side, and the exhaust valves 19, 19 are driven by a medium valve lift. That is, the valve lift of the exhaust valves 19, 19 is intermediate between the valve lift (small lift) of the intake valves 18, 18 at low speed and the valve lift (large lift) at high speed.

Next, the operation of the embodiment having the above configuration will be described.

When the engine E is rotating at a low speed, the solenoid 56 of the first hydraulic control valve 34 is in the OFF state, and the communication between the oil passages P4 and P8 is interrupted.
With the resilience of 4, the spool 53 is at the raised position shown in FIG. In this state, the oil pump operates the oil passages P1 and P2 of the cylinder head 23 and the oil passages P3 and P2 of the valve housing 51.
4, the first valve via the orifice 53c and the oil passage P5, the oil passages P9 and P10 of the cylinder head 23, the oil passages P11 and P13 of the lower camshaft holder 25, and the oil passage 32a in the intake rocker arm shaft 32. It communicates with the oil chamber 58a of the operation characteristic variable mechanism V1. At this time, the hydraulic pressure transmitted to the oil chamber 58a of the first valve operating characteristic variable mechanism V1 becomes low due to the action of the orifice 53c of the first hydraulic control valve 34, so that the first to third switching pins 69, 70, 71 9 is held at the position shown in FIG. 9, and the pair of intake valves 18, 18 are driven with a low valve lift, and the low pressure oil can lubricate the valve operating system (rocker arm support, camshaft support, etc.). It is.

As described above, when the output hydraulic pressure of the first hydraulic control valve 34 is low, the oil passage P20 of the lower camshaft holder 25 and the intake camshaft 12 shown in FIG.
The second valve operating characteristic variable mechanism V via the oil passage 12c inside
The hydraulic pressure transmitted to the second oil chamber 107 also becomes low, and the stopper pin 105 is resiliently moved by the spring 106 to the long groove 97b.
Break away from The second hydraulic control valve 47 (see FIG. 10) connected to the oil pump via the oil passages P1 and P14 of the cylinder head 23, the oil passage P15 in the filter housing 45, and the oil passage P16 of the cylinder head 23. When the duty ratio is controlled, the advance chamber 103 of the second valve operating characteristic variable mechanism V2 is controlled via the pair of oil passages P17a and P17b.
, And the hydraulic pressures transmitted to the retard chambers 104 are different. As a result, the phase of the inner rotor 96 with respect to the outer rotor 93 can be changed within the range of the angle α (see FIG. 12), and the valve timing of the intake valves 18, 18 can be controlled.

At the time of low-speed rotation of the engine E described above,
The oil (relief oil) whose pressure has decreased after passing through the orifice 53c of the first hydraulic control valve 34 is connected to an oil passage P5,
The groove 53c of the spool 53 and the drain port 51b
Through the oil passage P6 of the cylinder head 23 and the oil passage P7 of the bulging portion 25a of the lower camshaft holder 25, and from the oil drain port 25b to the exhaust camshaft sprocket 1
The lubricating fluid flows out to the engagement start portion (or the engagement portion) of the timing chain 17 and lubricates the timing chain 17 (see FIG. 7). When the engine E rotates at a low speed, the rotation speed of the timing chain 17 is also low, so that the amount of oil adhering to the timing chain 17 scattered by centrifugal force is reduced. Therefore, if oil is supplied to the meshing start portion of the timing chain 17 with the exhaust camshaft sprocket 16 on the delay side of the timing chain 17, the load on the timing chain 17 may be small because the engine E is rotating at a low speed. Thus, the meshing portion between the intake camshaft sprocket 15 and the timing chain 17 on the leading side in the rotation direction can be sufficiently lubricated.

As described above, since the relief oil of the first hydraulic control valve 34 flows out from the oil drain port 25b to lubricate the timing chain 17, an oil jet and its mounting space are not required, and the oil drain port 25b Is formed on the mating surface of the cylinder head 23 and the lower camshaft holder 25,
The configuration of the oil passage P7 is simplified. The first hydraulic control valve 34
Is attached to the side wall of the side cylinder head 23 near the oil drain port 25b, so that the oil drain port 25b
The length of the oil passage P7 for the relief oil can be reduced as compared with the case where the oil passage P7 is mounted on the side wall of the cylinder head 23 farther from the cylinder head 23, and the mounting rigidity of the first hydraulic control valve 34 can be increased.

Further, the oil passage P7 for relief oil formed on the mating surface of the cylinder head 23 and the lower camshaft holder 25 and the first hydraulic control valve 37 are connected to the camshaft 1
Since they are arranged on the same plane orthogonal to 2, 13,
The lengths of the oil passages P6 and P7 from the first hydraulic control valve 37 to the oil drain port 25b can be further reduced.

As shown in FIG. 6, when the engine E rotates at a high speed, the solenoid 56 of the first hydraulic control valve 34 is turned on, the oil passages P4 and P8 communicate with each other, and the land 53b
When the spool 53 moves down due to the hydraulic pressure acting on the oil passage P3,
And the oil passage P5 communicate with each other via the groove 53c. As a result, the high pressure oil pressure is applied to the oil passages P9 and P10 of the cylinder head 23 and the oil passage P of the lower camshaft holder 25.
11, P13 and an oil passage 32a in the intake rocker arm shaft 32, the oil is transmitted to the oil chamber 58a of the first valve operating characteristic variable mechanism V1, and the first to third switching pins 69, 7
The pair of intake valves 18, 18 are driven at a high valve lift by the movement of the valves 0, 71 against the spring 73.

As described above, when the output oil pressure of the first oil pressure control valve 34 is high, the oil passage P20 of the lower camshaft holder 25 and the intake camshaft 12 shown in FIG.
The second valve operating characteristic variable mechanism V via the oil passage 12c inside
The hydraulic pressure transmitted to the second oil chamber 107 also becomes high, and the stopper pin 105 engages with the long groove 97b against the spring 106. Therefore, the cylinder head 23 is attached to the oil pump.
By controlling the duty ratio of the second hydraulic control valve 47 connected via the oil passages P1 and P14, the oil passage P15 in the filter housing 45, and the oil passage P16 of the cylinder head 23, a pair of oil Through the paths P17a and P17b, the advance chambers 103 of the second variable valve operating characteristic mechanism V2 are connected.
A difference is generated in the hydraulic pressure transmitted to the retard chambers 104, and the phase of the inner rotor 96 with respect to the outer rotor 93 is changed within the range of the angle β (see FIG. 12) to control the valve timing of the intake valves 18, 18. can do.

In FIG. 8, when the engine E rotates at a high speed, the high-pressure oil supplied to the oil passage P12 formed on the outer periphery of the bolt 28 pushes and opens the relief valve 40 in the mounting bolt 39 of the oil jet 36. Thus, the oil is jetted from the nozzle hole 37a of the oil jet main body 37 to lubricate the engagement start portion (or the engagement portion) of the intake camshaft sprocket 15 and the timing chain 17. In FIG. 6, the oil supplied to the oil passage P8 of the first hydraulic control valve 34 is supplied to the orifice 53e of the spool 53 and the inner hole 53d.
And a groove 53f, a drain port 51b of the valve housing 51, an oil passage P6 of the cylinder head 23,
Oil passage P7 of bulging portion 25a of lower camshaft holder 25
After that, the oil flows out from the oil drain port 25b to the meshing start portion (or meshing portion) of the exhaust camshaft sprocket 16 and the timing chain 17 to lubricate the timing chain 17 (see FIG. 7).

As described above, at the time of low-speed rotation of the engine E in which the load on the timing chain 17 decreases, only the engagement start portion between the exhaust camshaft sprocket 16 and the timing chain 17 is lubricated with relief oil, and the load on the timing chain 17 is reduced. When the engine E rotates at a high speed, the engagement start portion between the intake camshaft sprocket 15 and the timing chain 17 is intensively lubricated with oil from the oil jet 36, and the engagement between the exhaust camshaft sprocket 16 and the timing chain 17 is increased. Since the start portion is supplementarily lubricated with the relief oil from the oil drain port 25b, the timing chain 17 can be optimally lubricated according to the operation state of the engine E, and the durability can be increased.

That is, the operation of the oil drain port 25b and the oil jet 36, which are a plurality of oil supply means for supplying oil to the timing chain 17, is controlled by the engine E
Therefore, the lubrication according to the operating condition of the engine E can be performed, and the wear of the timing chain 17 can be reduced. In addition, since the number of oil supply means that operates in accordance with an increase in the number of revolutions of the engine E is increased, the number of lubricating points is increased in accordance with an increase in load, so that the wear of the timing chain 17 can be more effectively reduced. .

In particular, the engine E in which the valve lift (medium valve lift) of the exhaust valves 19, 19 is larger than the valve lift (small valve lift) of the intake valves 18, 18
At low speed, the intake camshaft sprocket 15
A relatively large amount of oil is supplied to the side of the exhaust camshaft sprocket 16 having a larger load than that of the intake valve 1.
During high-speed rotation of the engine E in which the valve lifts (large valve lifts) 8 and 18 are larger than the valve lifts (medium valve lifts) of the exhaust valves 19 and 19, the intake cam having a larger load than the exhaust camshaft sprocket 16 A relatively large amount of oil is supplied to the shaft sprocket 15 side,
In addition, by supplying a relatively small amount of oil to the exhaust camshaft sprocket 16 as well, it is possible to secure an optimum amount of oil to be supplied according to the operating state of the engine E.

That is, the lift amount of the intake valves 18 and 18 and the exhaust valves 19 and 1 are changed according to the operating state of the engine E.
9 is provided with a first valve operating characteristic variable means V1 whose magnitude relationship with the lift amount changes, and the amount of oil supplied to the meshing portion between the timing chain 17 and the sprocket that drives the valve on the side with the larger lift amount is lifted. Sprocket and timing chain 17 for driving the valve on the smaller side
Because it was larger than the amount of oil supplied to the meshing part with
More oil can be supplied to the sprocket with the larger valve operating load to extend the life of the timing chain 17. In addition, a first valve for switching between a low-speed valve lift when the engine speed is lower than a predetermined value and a high-speed valve lift when the engine speed is higher than a predetermined value.
A hydraulic control valve 34 is provided, and the first hydraulic control valve 34 establishes a low-speed valve lift during low-speed rotation of the engine E,
A high-speed valve lift is established when the engine E rotates at a high speed, the timing chain 17 is lubricated with low-pressure relief oil from the first hydraulic control valve 34 during a low-speed valve lift, and the first hydraulic control valve is used during a high-speed valve lift. 34
Since the timing chain 17 is lubricated with the high-pressure valve lift control oil from above, the timing chain 17 can be effectively prevented from being worn by supplying an appropriate amount of oil according to the load condition at that time.

The oil passage P6 of the cylinder head 23
The blind plug 35 provided at the bulging portion 25a of the lower camshaft holder 25 facing the downstream end of the lower part is removed, and a measuring instrument 108 is attached instead of the blind plug 35 as shown in FIG. The operating state of the first valve operating characteristic variable mechanism V1 can be easily checked by supplying a fluid pressure such as air from the apparatus. As is clear from FIG. 5, the seating surface of the blind plug 35 formed on the lower camshaft holder 25 is different from the upper camshaft holder 26.
Is provided at a position lower than the coupling surface of the blind plug 3
The length of the lower camshaft holder 25 can be reduced, as well as the length of the lower camshaft holder 25 can be reduced.

By fitting the tip of the measuring instrument 108 to the oil passage P6 in the cylinder head 23 via a sealing member,
The operating state of the first valve operating characteristic variable mechanism V1 can be confirmed without being affected by the oil path P7 of the relief oil (fluid pressure escape).

Next, a second embodiment of the present invention will be described with reference to FIG.

The chain guide 41 of the second embodiment does not include the sliding member 43 made of synthetic resin. Instead, the upstream side of the oil passage 41 a formed inside the chain guide 41 is formed on the outer periphery of the bolt 28. To the oil path P12
The downstream side communicates with an orifice 41c opened on a sliding surface 41b facing the timing chain 17. Therefore, when high-pressure oil is supplied to the oil passage P12 during high-speed rotation of the engine E, the oil is ejected from the oil jet 36 to the inner peripheral surface of the timing chain 17 and the oil formed inside the chain guide 41 is formed. Road 41a
From the timing chain 17 via the orifice 41c
Spouts on the outer peripheral surface of. Thus, the oil spouted from the orifice 41c causes the sliding surface 41 of the chain guide 41 to move.
The sliding portion between the b and the timing chain 17 can be effectively lubricated. Incidentally, the orifice 41c can be opened in the tooth jump prevention plates 42a and 42b (see FIG. 3) of the chain guide 41, so that the intake camshaft sprocket 15, the exhaust camshaft sprocket 16 and the timing chain can be opened. 17 can be effectively lubricated.

Although the embodiments of the present invention have been described in detail, various design changes can be made in the present invention without departing from the gist thereof.

[0065]

As described above, according to the first aspect of the present invention, the cam cap portion of the intake camshaft and the cam cap portion of the exhaust camshaft are integrally connected by the connecting wall to form the camshaft holder. Since the chain guide is fixed so as to bridge the concave portion formed between both cam cap portions and the connecting wall portion, the camshaft holder is reduced in weight by the concave portion, and the two cam cap portions are connected by the connecting wall portion and the chain guide. Can be combined to increase the rigidity and improve the support rigidity of the intake camshaft and the exhaust camshaft.

According to the second aspect of the present invention,
Since the camshaft holder and the chain guide are jointly fastened to the cylinder head with a common inner bolt, the number of bolts can be reduced. In addition, since the seating surfaces of the outer bolts arranged outside the two camshafts are formed lower than the seating surfaces of the inner bolts arranged inside, the camshaft holder can be downsized, and the engine can be downsized.

According to the third aspect of the present invention,
Since the tooth jump prevention plate is formed integrally with the chain guide, the rigidity of the chain guide is increased by the tooth jump prevention plate.

According to the invention described in claim 4,
Since the sliding member made of resin that comes into sliding contact with the timing chain is provided on the chain guide, not only the occurrence of wear of the timing chain can be suppressed, but also the sliding resistance between the chain guide and the timing chain can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of an engine.

FIG. 2 is an enlarged view taken in two directions in FIG. 1;

FIG. 3 is an enlarged view in the three directions of FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is an enlarged view of a main part of FIG. 4;

FIG. 6 is an operation explanatory view corresponding to FIG. 5;

FIG. 7 is a view taken along the line 7-7 in FIG. 3;

FIG. 8 is an enlarged sectional view taken along line 8-8 in FIG. 3;

9 is an enlarged sectional view of a main part of FIG. 3;

FIG. 10 is an enlarged sectional view taken along line 10-10 of FIG. 2;

FIG. 11 is a sectional view taken along line 11-11 of FIG. 3;

FIG. 12 is a sectional view taken along line 12-12 of FIG. 11;

FIG. 13 is an explanatory diagram of a use state of the measuring instrument.

FIG. 14 is a view corresponding to FIG. 8 according to a second embodiment of the present invention.

[Explanation of symbols]

12 intake camshaft 13 exhaust camshaft 15 intake camshaft sprocket (sprocket) 15 exhaust camshaft sprocket (sprocket) 17 timing chain 26 upper camshaft holder (camshaft holder) 26a cam cap portion 26b cam cap portion 26c connecting wall portion 26d Recess 27 bolt (outer bolt) 28 bolt (inner bolt) 29 bolt (inner bolt) 30 bolt (outer bolt) 41 chain guide 42a tooth jump prevention plate 42b tooth jump prevention plate 43 sliding member

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16H 7/18 F16H 7/18 BF Term (Reference) 3G016 AA08 AA19 BA23 BA28 BA30 BB14 BB17 BB26 CA11 CA12 CA13 CA16 CA19 CA21 CA22 CA23 CA24 CA27 CA29 CA33 CA35 CA36 CA38 CA51 DA06 DA22 EA12 FA27 GA00 GA01 3G024 AA05 AA08 DA06 DA10 FA00 FA01 GA26 HA13 3J049 AA08 BE08 BE09 CA02

Claims (4)

[Claims] 1. A timing chain (17) is wound around sprockets (15, 16) fixed to ends of an intake camshaft (12) and an exhaust camshaft (13), respectively, and the timing chain (17) is guided. Chain guide (41) is connected to both camshafts (12, 1).
D fixed to the cam cap part (26a, 26b) of 3)
In an OHC engine, a cam cap portion (26a) of an intake camshaft (12)
And the cam cap (2) of the exhaust camshaft (13)
6b) are integrally connected by a connecting wall (26c) to form a camshaft holder (26), and the connecting wall (26c) is formed.
The concave portion (26) is formed on the surface facing the chain guide (41).
A DOHC-type engine characterized in that d) is formed. 2. An outer bolt (2) disposed outside an intake camshaft (12) and an exhaust camshaft (13).
7, 30), the camshaft holder (26) is fastened to the cylinder head (23), and the camshafts (28, 29) are arranged inside the intake camshaft (12) and the exhaust camshaft (13). The holder (26) and the chain guide (41) are fastened together to the cylinder head (23), and the seat surface of the outer bolt (27, 30) is formed lower than the seat surface of the inner bolt (28, 29). The DOHC engine according to claim 1, wherein: 3. The DOHC engine according to claim 1, wherein said chain guide (41) is integrally formed with tooth skip prevention plates (42a, 42b). 4. The chain guide (41) according to claim 1, further comprising a resin sliding member (43) slidingly contacting the timing chain (17).
The DOHC engine according to the item.