JP2809437B2 - Multi-valve 4-cycle engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multi-valve four-cycle engine in which a plurality of intake valves are opened and closed by two intake camshafts.

(Background of the Invention) In a four-stroke engine, in order to increase output in a high-speed rotation range, it is widely practiced to increase the overlap (valve overlap) of intake and exhaust valves.
It is also known to increase the number of intake / exhaust valves (to increase the number of valves) in order to increase the engine output by reducing the suction resistance and increasing the volumetric efficiency. Since the use of a plurality of intake / exhaust valves in this manner substantially increases the valve overlap, the operation during idling is unstable in an engine having such an increased valve overlap or multiple valves. become. Further, because of the blow-by of fresh air or the blow-back of fresh air during the middle / low speed operation, the output is reduced and the fuel efficiency is deteriorated.

(Object of the Invention) The present invention has been made in view of such circumstances,
When multiple intake valves are provided for one cylinder, idling is stabilized while increasing output during high-speed rotation,
It is another object of the present invention to provide a multi-valve four-stroke engine capable of improving performance in a middle / low speed range.

According to the present invention, there is provided a multi-valve four-cycle engine including a plurality of intake valves for one cylinder.
Two intake camshafts disposed in parallel with each other above the combustion chamber to open and close different intake valves, and a clutch for intermittently controlling the rotation of at least one of the intake camshafts;
A main throttle valve provided in the collecting portion of the intake passage in which the downstream side is a branch path corresponding to each intake valve and the upstream side is a collecting portion, and intake air opened and closed by an intake camshaft whose rotation is interrupted by the clutch. A throttle valve provided in a branch passage of the intake passage communicating with the valve, and connecting the clutch during high-speed operation and disengaging during low-medium-speed operation,
A multi-valve four-stroke engine is characterized in that the throttle valve is opened during high-load operation and closed during low-load operation.

(Embodiment) FIG. 1 is a side sectional view of an in-line four-cylinder engine according to an embodiment of the present invention, FIG.
FIG. 3 is a plan view showing a valve arrangement, and FIG. 4 is a plan view of FIG.
FIG. 4 is a sectional view taken along line IV-IV. FIG. 1 is a cross-sectional view of I in FIG.
-Corresponds to a section taken along line I.

In FIG. 1, reference numeral 10 denotes a cylinder head, 12 denotes a cam case, and 14 (14a, 14b) denotes a cam cover. Although there is a cylinder body below the cylinder head 10, only the cylinder inner wall surface 16 is shown in the figure. As shown in FIGS. 1 and 2, one ignition plug 20 which is substantially perpendicular to the center of the combustion chamber 18 is attached to the cylinder head 10, and the ignition plug 20 is provided with an ignition plug mounting hole 22 provided in the cam case 12. (FIG. 2), it is detachable upward.

24 (24a-d) is four intake valves, and 26 (26a-b) is two exhaust valves. These intake and exhaust valves 24 and 26 are ignition plugs
They are arranged at approximately equal intervals so as to surround 20. Intake valve 24
As shown in FIG. 1, ad is located on the left side and inclined to the left with respect to the spark plug 20, and the exhaust valves 26 are located on the right side and inclined to the right with respect to the spark plug 20. As shown in FIG. 1, two adjacent inner intake valves 24b and 24c that are inclined to the left so as to be far from the ignition plug 20 when viewed from the side,
The two outer intake valves 24a, d sandwiching these intake valves 24b, c
More strongly to the left.

A camshaft chamber 28 is provided between the cam case 12 and the two cam covers 14.
(28a, 28b) are formed, and three cam shafts 30 (30a, 30b, 30c) are provided between the mating surfaces of the cam case 12 and the cam cover 14.
Are arranged in parallel. That is, the camshaft 30 on the intake side
a and 30b are held between the cam case 12 and a cam cap 32 (only 32a and 32b are shown, FIG. 2) mounted at a predetermined position in the intake side camshaft chamber 28a. Exhaust camshaft
30c is a cam case 12 and a cam cap 34 (only 34a and 34b are shown) mounted at a predetermined position in the exhaust side camshaft chamber 28b.
And is held between. Two camshafts 30a, 3 on the intake side
0b, the camshaft 30a on the side of the ignition plug 20 is the outer intake valve 24a,
24d is opened and closed via valve lifters 36a and 36d. Spark plug 2
The camshaft 30b farther from 0 opens and closes two intake valves 24b and 24c adjacent to each other via valve lifters 36b and 36c. The exhaust-side camshaft 30c opens and closes the two exhaust valves 26 via valve lifters 38a and 38b.

A gear 40a is rotatably held at the shaft end of the cam shaft 30a on the intake side, and the gear 40b is fixed at the shaft end of the cam shaft 30b. These gears 40a, 40b mesh with each other. gear
40a can be connected to and disconnected from the camshaft 30a by a clutch 46 described later. Therefore, in the connected state of the clutch 46, the camshafts 30a and 30b rotate in the opposite directions at the same speed in synchronization with each other. The camshaft 30a on the intake side is divided into left and right,
Sprockets 42b and 42c are provided at the center of the other camshaft 30b and the center of the exhaust-side camshaft 30c.
A timing chain 44 (FIG. 3) is wound around 42b, 42c and a crankshaft (not shown), and each camshaft 30 is rotated at half the speed of the crankshaft.

Reference numeral 46 denotes a clutch, which connects and disconnects the camshaft 30a and the gear 40a. That is, a slider 48 is spline-coupled to the end of the camshaft 30a and held movably in the axial direction, and a known dog clutch is formed by the slider 48 and the gear 40a. Reference numeral 50 denotes a shift fork which is slidably held on the cam cover 14 by a support shaft 52.
One end of 50 is engaged with the slider 48, while the other end is engaged with the electromagnetic solenoid 54. As a result, the slider 48 is separated from the gear 40a by the excitation of the
When the excitation stops, the return spring of the shift fork 50
Returning by 56, the slider 48 engages the gear 40a.

1 and 3, 58 is an intake passage, and 60 is an exhaust passage. The intake passage 58 branches for each of the intake valves 24a to 24d, and the outside intake valve 2
A throttle valve 62 (62a, 62d) is provided in the branch passages 58a, 58d of 4a, 24d. A main throttle valve (not shown) is provided in the upstream gathering portion in the intake passage. The throttle valve 62 is closed at a low load (low opening) in conjunction with a main throttle valve (not shown) for controlling the total flow rate of the intake air to increase the speed of intake air into the combustion chamber, thereby enhancing swirl. Promotes combustion.

The clutch 46 is intermittently controlled, for example, as follows. During high-speed operation, the solenoid 54 is de-energized and the clutch 46 is connected. As a result, the cam shaft 30a rotates,
One of the intake valves 24a to 24d opens and closes. During middle / low speed operation at a predetermined speed or less, the solenoid 54 is excited and the clutch 46 is disengaged. Therefore, the intake valves 24a and 24d remain closed, and only the intake valves 24b and 24c open and close. As a result, valve overlap is substantially reduced, idling is stabilized, and performance in a middle / low speed range and fuel economy can be improved. During high-speed low-load operation, the throttle valve 62 is also closed to strengthen the swirl and improve fuel efficiency.

In this embodiment, the clutch 46 is provided on the camshaft 30a for opening and closing the outer intake valves 24a, 24d, but the inner intake valve 24b,
A clutch may be provided on the cam shaft 30b that opens and closes c. In this case, since only the small-diameter intake valves 24a and 24d are operated at a low speed, a strong swirl effect is obtained, and there is a great effect particularly in improving fuel efficiency. The present invention is applicable if the number of intake valves 24 is not two but two or more.

5 and 6 are cross-sectional views of other embodiments of the clutch.

The clutch 46A in FIG. 5 uses a known ball-lock type clutch. That is, the cam body 70 is moved forward and backward within the camshaft 30Aa by the electromagnetic solenoid 72 and the return spring 74, and the balls 76, 76 are protruded by the cam body 70 in the outer diameter direction of the camshaft 30Aa, so that the inner peripheral surface of the gear 40a is formed. The ball 76 is engaged with the engagement hole formed in the above.

The clutch 46B shown in FIG. 6 moves the cam 70B by hydraulic pressure. That is, the hydraulic pressure intermittently driven by the solenoid valve (not shown) is guided from the crankcase 78 to the oil chamber 80 in the camshaft 30B, and the cam body 70B is moved to the right in FIG. Gears 76 with ball 76 by
0a. 74B is a return spring.

The reason why the ball 76 is displaced in the axial direction in FIGS. 5 and 6 is that the camshafts 30Aa and 30Ba and the gear 40a always engage in the same phase. That is, only one set of the ball 76 and the engagement hole into which it is engaged is provided on a plane orthogonal to the cam shaft.

In each of the above embodiments, the present invention is applied to a direct-acting type valve operating mechanism in which a supply / exhaust valve is directly opened / closed by a valve lifter. However, the present invention is also applicable to an apparatus which is opened / closed by a rocker arm.

Further, the intake valves 24a to 24d are not only configured to open and close in the same phase, but may be changed in phase. For example, the valve opening / closing timing by one camshaft is advanced or delayed with respect to the other valve opening / closing timing,
The valve opening angle range may be changed.

(Effect of the Invention) As described above, the present invention has two intake-side camshafts, and connects the clutch for intermittently rotating one of the camshafts at the time of high-speed operation and disconnects it at the time of low-medium-speed operation. At the time of high speed, the output can be increased by substantially increasing the valve overlap, while the operation performance at the time of idling or at low / medium speed operation can be improved. Also, a throttle valve is provided for an intake valve that is opened and closed by an intake camshaft whose rotation is interrupted by a clutch. That is, a throttle valve is provided in a branch passage on the downstream side of the intake passage that guides intake air to these intake valves. This throttle valve is provided separately from the main throttle valve provided in the gathering portion on the upstream side of the intake passage, and the main throttle valve is opened when the load is large and closed when the load is low. It is possible to enhance the swirl by increasing the flow rate of the intake air into the air, thereby promoting the combustion. For this reason, it is possible to obtain preferable performance according to the operating state.

[Brief description of the drawings]

1 is a side sectional view of one embodiment of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a plan view showing a valve arrangement, and FIG. 4 is a sectional view taken along line IV-IV in FIG. . 5 and 6 are sectional views showing another embodiment of the clutch. 24 ... intake valve, 26 ... exhaust valve, 30 ... camshaft, 46, 46A, 46B ... clutch, 58 ... intake passage, 58a, 58d ... branch passage 62 ... throttle valve.

Claims (1)

(57) [Claims] 1. A multi-valve four-stroke engine having a plurality of intake valves for one cylinder, comprising two intake camshafts arranged in parallel with each other above a combustion chamber to open and close different intake valves. A clutch for intermittently controlling the rotation of at least one of the intake camshafts;
A main throttle valve provided in the collecting portion of the intake passage in which the downstream side is a branch path corresponding to each intake valve and the upstream side is a collecting portion, and intake air opened and closed by an intake camshaft whose rotation is interrupted by the clutch. A throttle valve provided in a branch passage of the intake passage communicating with the valve, and connecting the clutch during high-speed operation and disengaging during low-medium-speed operation,
A multi-valve four-stroke engine wherein the throttle valve is opened during high load operation and closed during low load operation.