JPH0247570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for a four-stroke engine.

(Prior Art) In a four-stroke engine, the amount of intake air taken into the cylinder is normally adjusted by a throttle valve of a carburetor provided in the intake system.

However, the throttle valve is almost fully closed or has an extremely low opening in a low-load operating range including engine idling.

For this reason, the resistance when the intake air passes through the throttle valve becomes large, increasing the resistance to the intake air into the cylinder, and the amount of intake air drawn into the cylinder tends to be insufficient. The intake valve, which opens and closes the passage, closes relatively late.

However, when this is done, there is a problem in that the loss of the amount of intake air into the cylinder, that is, the pumping loss increases, and the fuel consumption rate of the engine decreases.

(Problems to be Solved by the Invention) The present invention was made in view of the above circumstances, and an object of the present invention is to reduce pumping loss in the low-load operation range including engine idling, and improve fuel consumption rate. do.

(Means for Solving the Problems) In order to solve the above problems, the intake system of the present application is provided in an intake passage between a throttle valve and an intake valve of a carburetor provided in the intake system of a 4-cycle engine. , an on-off valve is provided that is fully closed in a low-load operating range including engine idling, and is fully open in other operating ranges, and the intake passages on the upstream and downstream sides of this on-off valve are bypassed. A sub-intake passage is provided which communicates with the intake passage, and the sub-intake passage runs along the side of the intake passage and faces the combustion chamber deflected from the center. An intake valve is provided, and this sub-intake valve is constructed of a poppet valve similar to the intake valve and the exhaust valve, and is mounted and supported on the cylinder head, and the sub-intake valve is connected to a camshaft that drives the intake valve. .

(Example) An example of carrying out the present invention will be explained with reference to the drawings regarding an intake system for a four-stroke engine for a motorcycle. Head c is a cylinder head cover.

A liner 1 is cast into the inner periphery of the cylinder a, and a piston d is slidably fitted into the liner 1.

2 is a combustion chamber formed between the lower surface of the cylinder head b and the upper end of the piston d located at the top dead center, and this combustion chamber 2 includes an intake passage 3 and an exhaust passage 4.
and are facing each other and opening.

5 is an intake valve that opens and closes the intake passage 3; 6 is an exhaust valve that opens and closes the exhaust passage 4; these intake and exhaust valves 5 and 6 are poppet valves; camshaft 9
The camshaft 9 is connected to the camshaft 9 and driven as the camshaft 9 rotates. 9a is a cam provided on the camshaft 9 for driving the intake valve 5, and 9b is a cam for driving the exhaust valve 6.

Reference numeral 10 denotes a carburetor provided upstream of the intake passage 3, and is connected to the intake passage 3 on the engine A side via a rubber joint 11.

Reference numeral 12 denotes a throttle valve provided in the intake passage 3 of the carburetor 10, and by adjusting the opening degree of the throttle valve 12, the amount of intake air sucked into the cylinder a is adjusted. There is.

The throttle valve 12 is connected to an accelerator grip 13 provided on a steering handle (not shown),
It is designed to be opened and closed by rotating the grip 13.

An operating rod 14 is connected to the support shaft 12a of the throttle valve 12, and is connected to an operating member 16 via a wire 15.

The actuating member 16 is connected to the accelerator grip 13 via a wire 29 so as to rotate together therewith, and the wire 16 from the actuating rod 14 is connected to the accelerator grip 13 via a wire 29.
5 are connected to each other and includes a locking portion 16a for winding up the wire 15.

The locking portion 16a protrudes near the connecting portion of the wire 15 toward the front in the rotating direction of the actuating member 16;
The portion remote from the connecting portion is retracted rearward in the rotational direction of the actuating member 16.

Therefore, when the amount of rotation of the accelerator grip 13 is small, the amount of winding of the wire 15 is small, so the opening degree of the throttle valve 12 increases gradually. Then, when the amount of rotational operation of the accelerator grip 13 exceeds a predetermined value, the wire 15 is pulled significantly, so that the opening degree of the throttle valve 12 increases rapidly in proportion to the amount of rotational operation of the accelerator grip 13.

The change in opening degree of the throttle valve 12 with respect to the amount of rotational operation of the accelerator grip 13 is shown in a graph in FIG.

The part indicated by the dotted line in the figure represents the change in the opening degree of the conventional throttle valve, and in comparison with this, the throttle valve 12 of this embodiment initially had a larger opening degree than the conventional one, and from there the accelerator grip 13
The degree of opening increases gradually until the amount of rotational operation exceeds a predetermined value, and thereafter the degree of opening increases in the same manner as in the conventional case.

17 is an on-off valve provided in the intake passage 3 between the throttle valve 12 and the intake valve 5, specifically, in the intake passage 3 on the engine A side.

This on-off valve 17 is fully closed in the low-load operating range of the engine A, closing the intake passage 3 downstream of the throttle valve 12, and 24 is a support shaft 17 of the on-off valve 17.
It is an operating rod connected to a, and is a cylindrical connecting member 2
It is connected to the actuating member 16 by two wires 26 and 27 which are connected via 5.

The tip of the wire 26 on the operating rod 24 side is inserted into the connecting member 25, and a gap is provided between it and the bottom wall 25a of the connecting member 25 that locks it.

On the other hand, one end of the wire 27 on the operating member 16 side is locked to the operating member 16, and the other end is fixed to the spring 28.
It is connected to the connecting member 25 via.

Reference numeral 16b denotes a locking portion provided in the operating member 16 adjacent to the locking portion 16a of the wire 15 connected to the throttle valve 12;
The wire 27 on the 6th side is locked.

As the actuating member 16 rotates in conjunction with the rotating operation of the accelerator grip 13, the wire 27 secured to the member 16 is pulled, and the spring 2
8, the connecting member 25 is displaced upward in FIG. The wire 26 on the rod 24 side is not locked, and the wire 26 is not pulled.

Therefore, the on-off valve 17 is not opened and remains fully closed.

When the amount of rotation of the accelerator grip 13 exceeds a predetermined value, the wire 26 on the operating rod 24 side is engaged with the connecting member 25 and pulled, and the operating rod 24 rotates downward in FIG. will be opened.

Note that after the on-off valve 17 is fully opened, the spring 28 is compressed as the accelerator grip 13 is rotated, so that only the wire 27 on the operating member 16 side is pulled.

FIG. 3 shows changes in the opening degree of the on-off valve 17 with respect to the amount of rotational operation of the accelerator grip 13, which also shows changes in the opening degree of the throttle valve 12.

As is clear from the drawing, the opening/closing valve 17 is initially fully closed, and when the amount of rotational operation of the accelerator grip 13 exceeds a predetermined value, the degree of opening increases rapidly and becomes fully open, and thereafter remains fully open. is maintained.

Reference numeral 18 denotes an auxiliary intake passage which connects the intake passages 3 on the upstream and downstream sides of the on-off valve 17 by bypassing the valve 17. This auxiliary intake passage 18 is the intake passage 3
The opening 18a on the downstream side is smaller in cross-sectional area than the opening 3a of the intake passage 3, and is formed along the side of the passage 3 on the wall surface constituting the intake passage 3.
It faces the combustion chamber 2 with a deviation from its center.

As described above, if the auxiliary intake passage 18 is provided along the side of the intake passage 3, the opening 18a thereof can be easily deflected from the center of the combustion chamber, and the auxiliary intake passage 18 can be easily deflected from the center of the combustion chamber. The intake air flows forcefully into the cylinder a, effectively generating a vortex, and burning the intake air at high speed and stably.

A sub-intake valve 19 opens and closes the sub-intake passage 18, and is provided in a vertical hole 20 intersecting with the sub-intake passage 18 via a guide 21 so as to be vertically slidable.

Like the intake and exhaust valves 5 and 6, this sub-intake valve 19 is a poppet valve with good sealing properties, and is installed so as to be vertically slidable with respect to the cylinder head b. The intake valve 5 is connected to the shaft 9 via the rocker arm 22.
They are now closing earlier than before.

The upper end of the sub-intake valve 19 is connected to the rocker arm 2.
2 and the camshaft 9 are housed in the upper space of the cylinder head b, the lubricating oil splashed into the space is smoothly supplied to the sliding part with the guide 21, thereby lubricating the sub-intake valve 19. is performed without any problem.

In order to satisfy the operating conditions of the sub-intake valve 19, the cam 9 for driving the valve 19 is arranged in parallel with the cam 9a for driving the intake valve 5 on the camshaft 9, and its top portion is placed on the camshaft 9. The cam 9a for the intake valve 5 is shaped so as to be located further forward in the rotational direction than the cam 9a for the intake valve 5.

As described above, by driving the auxiliary intake valve 19 using the camshaft 9 that drives the intake valve 5 and the exhaust valve 6, it is necessary to provide a special camshaft for driving the auxiliary intake valve 19. Since the structure is eliminated, there is an advantage that the structure can be simplified, and the opening/closing timing of the auxiliary intake valve 19 can be accurately matched to the opening/closing of the intake valve 5.

Furthermore, by installing the sub-intake valve 19 against the highly rigid cylinder head b, it is possible to prevent deformation of the sub-intake valve and its surroundings due to engine vibrations and when assembling the cylinder head b to the cylinder a. Thereby, there is no need to worry about the problem of deteriorating the sealing performance and durability of the sub-intake valve.

Note that 23 in the figure is a plug that closes the vertical hole 20.

In such an intake system, the throttle valve 12 of the carburetor 10 is opened more widely than before in the low-load operating range including idling of the engine A, so that the intake air passes through the throttle valve 12 without being subjected to large resistance. Intake passage 3 on the downstream side of the lever
flows to.

Since the intake passage 3 on the downstream side of the throttle valve 12 is closed by the on-off valve 17, the intake air flows from the intake passage 3 into the auxiliary intake passage 18 and from there via the auxiliary intake valve 19 into the cylinder. An appropriate amount is inhaled into a.

On the other hand, in the medium-load and high-load operating ranges of the engine A, the on-off valve 17 is fully opened, and intake air is drawn into the cylinder a through the intake passage 3 and the intake valve 5, as in the conventional case.

(Effects of the Invention) Since the present invention is configured as described above, it produces the effects listed below.

To improve the fuel consumption rate of the engine by increasing the opening degree of the throttle valve of the carburetor in the low-load operating range including idling to reduce the intake resistance of intake air and reduce the loss of intake air amount, that is, pumping loss. Can be done.

Since the auxiliary intake valve is linked to the camshaft that drives the intake valve, there is no need to provide a special camshaft to drive the auxiliary intake valve, which simplifies the structure and allows for easy opening and closing of the intake valve. It is possible to accurately match the opening/closing timing of the sub-intake valve to the timing.

The auxiliary intake valve is a highly airtight poppet valve, similar to the intake and exhaust valves, and is mounted on a highly rigid cylinder head, so when assembling the cylinder head to the cylinder, or when the auxiliary intake valve is damaged due to engine vibration. Deformation around the valve can be prevented, and the above deformation does not reduce the sealing performance and durability of the auxiliary intake valve, effectively reducing pumping losses by maintaining high airtightness of the auxiliary intake valve. can do.

Since the auxiliary intake valve is connected to the camshaft that drives the intake valve, lubricating oil from the intake valve can be naturally supplied to supporting parts, etc., making it easy to lubricate the auxiliary intake valve. Can be done.

Since the auxiliary intake passage is provided along the side of the intake passage, it is easy to form the auxiliary intake passage so that it is deflected by a predetermined amount from the center of the combustion chamber. By deviating from the center of the cylinder, a vortex can be effectively generated within the cylinder, and the intake air can be combusted at high speed and stably.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing the intake device of the present invention, Fig. 2
The figure is a sectional view taken along the line ( )-( ) of FIG. 1, and FIG. 3 is a graph showing changes in the opening degrees of the throttle valve and the on-off valve with respect to the amount of rotational operation of the accelerator grip. In the figure, A...4-cycle engine, a...cylinder, 2...combustion chamber, 3...intake passage, 5...intake valve, 1
0...Carburetor, 12...Throttle valve, 17...Opening/closing valve, 18...Sub-intake passage, 19...Sub-intake valve.

Claims (1)

[Claims] 1 In a 4-cycle engine, the intake passage between the throttle valve of the carburetor installed in the intake system and the intake system is fully closed in the low-load operating range, including engine idling, and fully open in other operating ranges. An on-off valve is provided, and a sub-intake passage is provided that communicates the upstream and downstream intake passages of the on-off valve by bypassing the valve, and the sub-intake passage runs along the side of the intake passage. , a sub-intake valve is provided in the sub-intake passage facing the combustion chamber at a direction deflected from the center thereof, and closes earlier than the intake valve, and the sub-intake valve is constituted by a poppet valve like the intake valve and the exhaust valve. An intake system for a four-cycle engine that is mounted and supported on a cylinder head and that connects the sub-intake valve to a camshaft that drives the intake valve.