JP2592964B2 - Engine valve gear - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve train for an engine including a camshaft dedicated to intake and a camshaft dedicated to exhaust.

(Prior Art) Conventionally, as a multi-valve engine, for example, Japanese Patent Application Laid-Open No. 62-7845
As disclosed in Japanese Unexamined Patent Publication No. 3 (1999) -2003, there is known a device in which three intake valves and two exhaust valves are provided for each cylinder to obtain high intake / exhaust efficiency. In this engine, three intake valves are provided so as to be inclined to one side of the cylinder bore toward the valve shaft end and the valve shafts are parallel to each other, and two exhaust valves are provided toward the valve shaft end. The bottom of the valve head of the intake / exhaust valve is disposed in an inclined shape on the other side of the cylinder bore so as to form a pent roof type combustion chamber with high combustion efficiency. In this engine, an intake valve is driven via a rocker arm by a camshaft dedicated to intake, and an exhaust valve is driven via a rocker arm by a camshaft dedicated to exhaust.

(Problems to be Solved by the Invention) When a camshaft is driven in such a multi-valve engine, a transmission member such as a timing belt or a timing chain is provided between the camshaft and the engine output shaft. Then, the output torque of the engine output shaft is transmitted to the camshaft via the transmission member to drive the camshaft.

However, in an engine equipped with two camshafts dedicated to intake and exhaust, if both of these two camshafts are driven via a transmission member by an engine output shaft, the two camshafts Since the driven pulley or sprocket having a diameter about twice as large as that of the driven pulley or sprocket mounted on the engine output shaft is mounted, the size of the engine is increased.

Accordingly, one of the two camshafts is driven by an engine output shaft via a transmission member, and both camshafts are provided with gears meshing with each other, and the other camshaft is connected to one camshaft. It is conceivable that the driven side pulley or the sprocket is driven by a shaft through gears to make the engine compact.

By the way, in the multi-valve engine as described above, as shown in FIG. 7, as the number of valves that open in the same stroke (intake or exhaust stroke) increases, one cam shaft is The driving reaction force of the valve acts intensively at the same time, and the torque fluctuation applied to the camshaft (that is, the fluctuation of the driving reaction force received by the camshaft from the corresponding valve) increases accordingly. Therefore, when one camshaft is driven by the other camshaft via a gear as described above, the gear has a backlash, and the torque fluctuation causes a rotational fluctuation on the driven camshaft. The gear life is shortened due to torque fluctuation. For this reason, if the tooth width is increased in order to increase the strength of the gear, compactness of the engine will be hindered.

The present invention has been made in view of such a point, and an object thereof is to provide two camshafts dedicated to intake and exhaust only, and to provide either an intake valve or an exhaust valve for each cylinder. In a multi-valve engine in which the number of one valve is larger than the number of the other valve, the driving member and the gear are used in combination to stably drive the camshaft and increase the reliability of the gear. The aim is to reduce the size of the engine by driving the camshaft.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a camshaft having a larger torque variation among the intake-only and exhaust-only camshafts is driven by an engine output shaft via a transmission member. The camshaft with the smaller torque fluctuation is driven via the gear by the camshaft with the larger torque fluctuation.

Specifically, the solution taken by the present invention comprises a dedicated camshaft for driving the intake valve and a dedicated camshaft for driving the exhaust valve, and each cylinder driven by the dedicated camshaft for intake. The number of intake valves for each cylinder is different from the number of exhaust valves for each cylinder driven by the exhaust-dedicated camshaft, and the number of intake valves and exhaust valves for each cylinder is the other valve. It is assumed that the valve train of the engine is provided in a number larger than the number. Then, a transmission member is wound between the engine output shaft and a camshaft having a larger number of drive valves and having a larger maximum value of the drive reaction force received from the corresponding valve by the intake-only and exhaust-only camshafts. It is assumed that gears that mesh with each other are provided on the two camshafts.

(Operation) According to the above configuration, in the present invention, the camshaft having the largest value of the fluctuation of the driving reaction force received from the valve and having the larger number of driving valves is driven by the engine output shaft via the transmission member. Further, the camshaft having a smaller number of drive valves having a smaller maximum value of the fluctuation of the drive reaction force received from the valve is driven via a gear by the camshaft having a larger number of drive valves.
Therefore, the driven pulley or sprocket becomes one and the engine becomes compact.

In this case, the larger the maximum value of the fluctuation of the driving reaction force received from the valve and the larger the torque fluctuation (the larger the number of valves to be driven)
Is directly driven by the engine output shaft via the transmission member instead of the gear drive, so that the rotation of the camshaft is stabilized.

Also, since the camshaft driven via the gear is the one with the smaller maximum value of the driving reaction force received from the valve and the smaller the torque fluctuation (the smaller the number of valves to be driven), the backlash of the gear, etc. It is easy to suppress the fluctuation of the rotation of the camshaft within the allowable range. In addition, since the torque fluctuation is small, the reliability of the gear can be improved without taking measures such as increasing the tooth width, and the engine can be made more compact.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

1 to 5 show a V-type six-cylinder engine having three intake valves and two exhaust valves according to an embodiment of the present invention. These figures show only one cylinder as a representative, but the other cylinders have the same configuration. In these figures, 1 is a cylinder block, 2 is a cylinder head disposed on the cylinder block 1, and 3 is a cam housing disposed on the cylinder head 2.

A cylinder 5 is formed in the cylinder block 1,
A piston 6 is slidably fitted into the cylinder 5. The lower surface of the cylinder head 2 has two inclined walls.
A pent roof combustion chamber 7 having 7a, 7b is formed.

On the left side of the cylinder bore of the cylinder head 2, three independent intake ports 11, 12, and 13 for guiding fresh air to the cylinder 5 are provided. The independent intake ports 11 to 13 are provided so that one end opens to the left inclined wall 7 a of the combustion chamber 7 and the other end opens to the left side wall of the cylinder head 2. The openings on the combustion chamber side of the independent intake ports 11 and 13 on both sides are arranged in the front-rear direction of the engine (the vertical direction in FIG. 5), and are provided closer to the center of the cylinder bore than the central independent intake port 12 is. These three independent intake ports 11 to 13 are gathered into one intake port 10 on the left side wall of the cylinder head 2.

Two independent exhaust ports 21 and 2 for guiding the exhaust of the cylinder 5 to the outside are provided on the right side of the cylinder bore of the cylinder head 2.
Two are provided. The independent exhaust ports 21 and 22 are provided so that one end opens to the right inclined wall 7b of the combustion chamber 7 and the other end opens to the right side wall of the cylinder head 2. The combustion chamber openings of the two independent exhaust ports 21 and 22 are arranged in the front-rear direction of the engine. Also, two exhaust ports
Reference numerals 21 and 22 are arranged in one exhaust port 20 on the right side of the cylinder head 2.

The cylinder head 2 has three intake valves 31, 32, 33 for opening and closing the combustion chamber side openings of the independent intake ports 11 to 13, respectively.
Is provided. Each of the intake valves 31 to 33 has an umbrella-shaped valve head disposed in the opening and a valve shaft extending upward from the valve head.
And is slidably fitted in the housing so that it can move up and down. Disc-shaped spring seats 51, 52, 53 are attached to the valve shaft ends of the intake valves 31 to 33, respectively, and valve springs 61, 62, 63 are provided between the spring seats 51 to 53 and the cylinder head 2. Each of the intake valves 31 to 33 is urged upward, that is, in the valve closing direction by its spring force.

These three intake valves 31 to 33 are provided so that they are inclined to the left side of the cylinder bore toward the valve shaft end, and the valve shafts are parallel to each other.

The cylinder head 2 has independent exhaust ports 21 and 22.
Exhaust valves 41 and 42 that open and close the combustion chamber side openings of the
Is provided. These exhaust valves 41, 42 are also the above-mentioned intake valves 31.
33 are provided so as to be able to move up and down, and spring seats 54 and 55 and valve springs 64 and 65 are provided and urged in the valve closing direction.

These two exhaust valves 41 and 42 are provided so that they incline to the right side of the cylinder bore toward the valve shaft end, and that the valve shafts are parallel to each other.

Next, the drive mechanism of the intake / exhaust valves 31 to 33, 41, 42 will be described. On the left and right sides of the cam housing 3, there are provided camshafts 91 and 92 dedicated to intake and exhaust, respectively, which extend in the front-rear direction of the engine. These two camshafts 91 and 92 are driven by an engine output shaft (not shown), and the intake-only camshaft 91 is clockwise in FIG. 2 and the exhaust-only camshaft 92 is counterclockwise in FIG. Rotate. In addition, three intake cams 93 are integrally formed on the intake-dedicated camshaft 91 corresponding to the respective intake valves 31 to 33, and two exhaust cams are formed on the exhaust-dedicated camshaft 92 corresponding to the respective exhaust valves 41 and 42. 94 are integrally formed.

The intake valves 31 to 33 are driven by swing cams 91, 82, and 83 by a camshaft 91 dedicated to intake. That is, the cylinder head 2 is provided with the known hydraulic lash adjusters 71, 72, 73. The hydraulic lash adjusters 71 to 73 are provided with support portions. One end of each of the swing arms 81 to 83 rides on the support of the hydraulic lash adjusters 71 to 73, and the other end thereof is an intake valve.
31 to 33 are provided so as to ride on the valve shaft ends. Further, a roller having a rotation shaft extending in the front-rear direction of the engine is provided in a middle part of the swing arms 81 to 83, and the roller is in contact with the intake cam 93. Accordingly, when the intake-only camshaft 91 rotates, the intake cam 93
The roller moves up and down in accordance with the amount of lift, whereby the swing arms 81 to 83 swing up and down about the end on the hydraulic lash adjuster side. Therefore, the end of the swing arm 81 to 83 on the valve shaft end side swings up and down according to the arm ratio, and the intake valve 31 according to the up and down movement of this end.
~ 33 open and close.

Further, the exhaust valves 41 and 42 are also driven by the exhaust-dedicated camshaft 92 via the swing arms 84 and 85. This drive mechanism is similar to the swing arm
Hydraulic lash adjusters 74,75 supporting one end of 84,85
When the exhaust camshaft 92 rotates, the rollers of the swing arms 84 and 85 move up and down in accordance with the lift amount of the exhaust cam 94, so that the swing arms 84 and 85 are hydraulically operated. It swings up and down around the end on the lash adjuster side, and the end on the valve shaft end side of the swing arms 84 and 85 swings up and down according to the arm ratio, and according to the up and down movement of this end The exhaust valves 41, 42 open and close.

Here, the structure of the hydraulic lash adjusters 71 to 75 will be described with reference to FIG. In the figure, reference numeral 111 denotes a bottomed cylindrical casing, and 112 denotes an inner sleeve that is swingably inserted into the casing 111.
A hydraulic chamber 114 is formed between 1 and the inner sleeve 112. At the upper end of the inner sleeve 112, a pivot 113 is provided as a support for supporting one ends of the swing arms 81 to 85. The casing 111 and the inner sleeve 112 are provided with an oil passage 115 having one end communicating with the hydraulic chamber 114 and the other end communicating with an oil introduction port 116 provided on a peripheral wall of the casing 111. A check valve 118 for maintaining the hydraulic pressure in the hydraulic chamber 114 at a high pressure is provided at an end of the oil passage 115 on the hydraulic chamber side. Also,
The inner sleeve 112 is provided with an oil discharge passage 117 having one end communicating with the oil passage 115 and the other end opening at the center of the pivot 113 to relieve oil. The operation of the hydraulic lash adjusters 71 to 75 will be described. When a lash is present in the valve train and the pivot 113 receives a low supporting force from the swing arms 81 to 85, the hydraulic pressure in the hydraulic chamber 114 is low. Opens. For this purpose, oil flows from the oil inlet 116 through the oil passage 115 to the hydraulic chamber 11.
4 and the inner sleeve 112 comes out of the casing 111 due to the volume expansion of the hydraulic chamber 114. Due to this, the clearance between the swing arms 81 to 85 and the camshafts 91 and 92 and the swing arms 81 to 85 and the intake / exhaust valves 31 to 3
The clearance between 3,41,42 becomes zero. Then, the supporting force received by the pivot 113 from the swing arms 81 to 85 increases, and the hydraulic pressure in the hydraulic chamber 114 increases, so that the check valve 118 closes. As a result, the position of the inner sleeve 112 with respect to the casing 111 is fixed, and the swing arms 81 to 85 are received by the pivot 113.

Next, the arrangement of the hydraulic lash adjusters 71 to 75 will be described. First, in the case of the intake side, the central intake valve 32
The hydraulic lash adjuster 72 is provided on the side near the center of the cylinder bore with respect to the intake valves 31 to 33. The hydraulic lash adjuster 72 is provided at a predetermined angle to the left toward the pivot 113. That is, the hydraulic lash adjuster 72 is provided such that the center axis thereof coincides with the direction of the supporting force received from the swing arm 82. The hydraulic lash adjusters 71, 73 of the intake valves 31, 33 on both sides are provided farther from the center of the cylinder bore with respect to the intake valves 31 to 33. That is, the hydraulic lash adjusters 71 to 73 on the intake side are arranged in a staggered manner across the intake valves 31 to 33 in the front-rear direction of the engine.
The cylinder head 2 has an oil supply passage 121 communicating with an oil inlet 116 of a hydraulic lash adjuster 72 of a central intake valve 32, and an oil inlet 116 of hydraulic lash adjusters 71, 73 of both intake valves 31, 33. Oil supply passage communicating with
122 are provided.

In the case of the exhaust side, the hydraulic lash adjusters 74 and 75 of the two exhaust valves 41 and 42 are both provided farther from the center of the cylinder bore with respect to the exhaust valves 41 and 42. And
The cylinder head 2 has an oil supply passage 12 communicating with the oil inlet 116 of the two hydraulic lash adjusters 74 and 75.
Three are provided.

Next, a structure for driving the camshafts 91 and 92 by an engine output shaft will be described with reference to FIG. In the figure, reference numeral 131 denotes a gear case provided on the front side of the cylinder head 2 and the cam housing 3. The front side of the intake-only camshaft 91 is the gear case 131.
And extends to the front. A timing pulley 151 is attached to a front end of the intake-specific camshaft 91. On the other hand, a timing pulley (not shown) is also attached to the engine output shaft. A timing belt 152 as a transmission member is wound around the two timing pulleys, and the intake-only camshaft 9 is driven by the engine output shaft via the timing belt 152.
1 is driven to rotate at a predetermined rotation ratio. A gear cover 132 that covers the timing pulley 151 is attached to the gear case 131.

Further, inside the gear case 131, the first gear 141 is provided on the intake-only camshaft 91, and the exhaust-only camshaft 9 is provided.
The second gear 142 is attached to the second gear 142 so as to mesh with each other.
The exhaust-dedicated camshaft 92 is driven synchronously via the first and second gears 142. In the exhaust-only camshaft 92, a friction gear 143 is mounted on the front side of the second gear 142, and the conical pressing member 1 is mounted on the front side.
44 is attached, and a nut 1
45 is attached, the force of the cam shaft axial direction is stored in the holding member 144 by the tightening force of the nut 145,
The friction gear 143 is pressed against the second gear 142 by this force. Due to the phase shift in the rotation direction appropriately generated between the second gear 142 and the friction gear 143, the rotation fluctuation of the second gear 142 due to the backlash existing between the first gear 141 and the second gear 142 is reduced. Like that.

Further, a plug hole 101 is provided through the cylinder head 2 and the cam housing 3 above the combustion chamber 7, and a spark plug 102 is mounted in the plug hole with its ignition point 102 a desired in the combustion chamber 7. Have been. The plug holes 101 and the spark plugs 102 are arranged such that the ignition point 102a is located at the center of the cylinder bore of the combustion chamber 7 and the exhaust valves 41, 4
It is provided substantially parallel to the second valve shaft.

The cylinder head 2 above the intake port is provided with an injector 103 that injects fuel into fresh air.

The three swing arms 81 to 83 for the intake valve are the same member, and the parts are shared. In that case,
Three swing arms 81 to 83 with the engine assembled
It is conceivable to match the centers of the rollers, but it is possible to prevent the swing arms 81 to 83 from being enlarged without intentionally doing so.

Therefore, in the above embodiment, the intake dedicated camshaft 91 is connected to the timing belt 152 by the engine output shaft.
, And the exhaust-dedicated camshaft 92 is driven by the intake-dedicated camshaft 91 via the gears 141 and 142, so that the driven timing pulley 151 becomes one and the engine becomes compact.

In this case, the intake-only camshaft 91 having a large number of valves driven at the same timing and having large torque fluctuations is directly driven by the engine output shaft via the timing belt 152 instead of the gear drive. 91
Rotation becomes stable.

Further, since the exhaust-only camshaft 92 driven through the gears 141 and 142 has a small number of valves driven at the same timing and has a small torque fluctuation, rotation fluctuation of the camshaft 92 due to backlash of the gears 141 and 142 is allowed. It is easy to keep it within the range. In addition, since the torque fluctuation is small, the reliability of the gears 141 and 142 can be ensured without taking a strengthening measure such as increasing the tooth width, and the engine can be made more compact.

Although three intake valves and two exhaust valves are provided in the above embodiment, the number of exhaust valves may be increased. In short, the present invention is applicable to a multi-valve engine in which one of the intake valve and the exhaust valve is provided more than the other valve.

Further, although the camshaft 91 having a larger number of valves to be driven is driven by the belt transmission mechanism using the timing belt 152, it may be driven by a chain transmission mechanism using a timing chain.

(Effect of the Invention) As described above, according to the valve train for an engine of the present invention, a camshaft dedicated to intake that drives an intake valve,
A dedicated exhaust camshaft for driving the exhaust valve, and providing one or more of the intake valve and the exhaust valve for each cylinder more than the other valve. A transmission member is provided between the camshaft having the larger number of drive valves and the engine output shaft, which has a larger maximum value of the fluctuation of the driving reaction force received from the valve, and meshes with the two camshafts. Since each gear is provided, the driven pulley or sprocket becomes one and the engine can be made compact, and the number of valves driven at the same timing and the rotation of the camshaft with large torque fluctuation can be stabilized. And the reliability can be improved without strengthening the gear.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention. FIG. 1 is a cross-sectional view at the front of the engine, FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 5, and FIG. Fig. 4 is IV in Fig. 5.
FIG. 5 is a cross-sectional view taken along the line IV, FIG. 5 is a perspective plan view around the cylinder, FIG. 6 is an enlarged vertical sectional side view of the hydraulic lash adjuster, and FIG. 7 is an explanatory diagram showing torque fluctuation applied to the camshaft. 31, 32, 33 Inlet valves 41, 42 Exhaust valves 91 Inlet-only camshaft 92 Exhaust-only camshaft 141 First gear 142 Second gear 151 Timing pulley 152 Timing belt

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Hashimoto 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. -120704 (JP, U)

Claims (1)

(57) [Claims] An intake camshaft for driving an intake valve; and an exhaust camshaft for driving an exhaust valve. The number of intake valves for each cylinder driven by the intake-only camshaft; The number of exhaust valves for each cylinder driven by the exhaust-only camshaft was different, and the number of one of the intake valves and the number of exhaust valves for each cylinder was greater than the number of the other valves. In the valve operating device of the engine, the maximum value of the fluctuation of the driving reaction force received by the intake-only and exhaust-only camshafts from the corresponding valves is large. And a transmission member wound around the camshaft, and gears meshing with each other are provided on the two camshafts, respectively.