JPH11117816A - 4-cycle engine intake system - Google Patents

Abstract

(57) [Problem] To provide an intake device for a four-stroke engine which does not deteriorate the engine operation feeling even when the throttle valve is widely opened and the vehicle runs continuously at a relatively low speed. SOLUTION: An intake passage 17d communicating with a combustion chamber, and a throttle valve 2 provided in the middle of the intake passage 17d.
0 and a four-stroke engine intake system,
A fuel injection valve 25 is disposed upstream of the throttle valve 20 in the intake passage 17d. An intake passage 17d is provided upstream of the fuel injection valve 25 in the intake passage 17d and on a side facing the fuel injection valve 25. And a buffer valve 34 that changes the area of the intake air flow according to the state of the intake air flowing through the intake passage and makes the increase speed of the intake air flow slower than the increase speed of the intake air flow according to the opening speed of the throttle valve 20. Then, a heat retaining passage 72 for introducing engine cooling water was formed in the outer wall of the air supply passage 17d near the injection nozzle 25a of the fuel injection valve 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an intake system for a four-stroke engine.

[0002]

2. Description of the Related Art As an intake device for a four-cycle engine,
By arranging the throttle valve as close to the intake valve opening as possible, the applicant of the present application has determined the ratio (volume) of the volume (port volume) from the intake valve opening to the throttle valve of the intake passage to the stroke volume (displacement amount of each cylinder). Ratio) is set as small as possible, and a 4-cycle engine capable of purifying exhaust gas at low cost without lowering output performance has been developed and proposed earlier.

In the case where the throttle valve is arranged close to the intake valve opening, when no-load racing (idling) is performed, the amount of intake air rapidly increases without response delay in response to the throttle valve opening. On the other hand, since the specific gravity of the fuel is larger than that of the air, the fuel is increased with a delay with respect to the increase of the intake air amount. However, there is a concern that the driving feeling is reduced.

Therefore, in the engine according to the above proposal, the area of the intake passage is changed upstream of the throttle valve in the intake passage in accordance with the state of intake air flowing through the intake passage, and the increasing speed of the intake flow rate is controlled by the throttle valve. A buffer valve for slowing down the rate of increase of the intake flow rate according to the opening speed of the engine is provided.

[0005]

In the intake system for an engine according to the above proposal, when the throttle valve is widely opened and the vehicle is continuously driven at a relatively low speed, such as when traveling on a long uphill road, the engine is temporarily stopped. The problem that the driving feeling of the engine might be deteriorated was found.

[0006] The deterioration of the driving feeling is considered to be due to the following reasons. That is, a large amount of fuel is injected by continuously opening the throttle valve widely, and the temperature in the vicinity of the injection nozzle of the fuel injection valve is greatly reduced by vaporization of the large amount of fuel. Of the fuel freezes in the vicinity of the injection nozzle, thereby deteriorating the fuel injection state or adhering to the inner wall of the intake passage without vaporizing the fuel. As a result, it is considered that the above-described driving feeling is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an intake system for a four-stroke engine which does not deteriorate the driving feeling of the engine even when the throttle valve is widely opened and the vehicle runs continuously at a relatively low speed. The task is to provide.

[0008]

According to a first aspect of the present invention, there is provided an intake system for a four-cycle engine including an intake passage communicating with a combustion chamber, and a throttle valve provided in the middle of the intake passage. A fuel injection valve is disposed upstream of the throttle valve of the intake passage, and the area of the intake passage is set to be larger than the fuel injection valve of the intake passage and to be opposed to the fuel injection valve. A buffer valve that changes the intake air flow rate in accordance with the state of the flowing intake air and makes the increase rate of the intake flow rate slower than the increase rate of the intake flow rate in accordance with the opening speed of the throttle valve; A heat retaining passage for introducing engine cooling water is formed near the injection nozzle of the injection valve.

According to a second aspect of the present invention, in the first aspect, an idle passage is formed on the fuel injection valve side of the intake passage so as to bypass the throttle valve in the fully closed state, and the idle passage is provided in the idle passage. An idle control valve for changing the area is provided, and the heat retaining passage is provided in a portion of the outer wall of the intake passage between the injection nozzle and the idle control valve.

[0010]

According to the first aspect of the present invention, the buffer valve for changing the area of the intake passage in accordance with the state of the intake air is provided. As the negative pressure in the passage becomes larger than the urging force of the buffer valve in the closing direction, the passage opens, and the resistance of the intake passage decreases, thereby reducing the increasing speed of the intake air amount due to the rapid opening of the throttle valve. Therefore, even in the case of the above-mentioned no-load racing, the increase speed of the air amount is suppressed from being excessive,
As a result, the delay in fuel responsiveness is alleviated, whereby the occurrence of misfire can be suppressed, and there is an effect that a decrease in the engine operation feeling can be avoided.

Further, since a heat retaining passage for introducing engine cooling water is provided in the vicinity of the injection nozzle of the fuel injection valve, the vicinity of the injection nozzle in the intake passage is always warmed by the heat of the engine cooling water. Even when the fuel is injected, an extreme decrease in temperature can be avoided, and there is an effect that icing and adhesion of fuel to a wall surface can be prevented, and deterioration of an engine operation feeling can be prevented.

According to the second aspect of the present invention, the heat retaining passage is disposed between the injection nozzle of the fuel injection valve and the idle regulating valve disposed in the idle passage. It is also possible to prevent the temperature from dropping, to prevent the idle passage from being clogged due to icing or the like, and to stabilize the idling rotation.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 5 are views for explaining an intake system of a four-stroke engine according to an embodiment of the present invention. FIG. 1 is an overall configuration diagram of the engine, and FIG. 2 is a cylinder block and a throttle body of the engine. FIG. 3 is a plan view schematically showing the shape of the intake port of the engine, FIG. 4 is a right side view of the cross section of the engine, and FIG. 5 is a motorcycle equipped with the engine. FIG.

In FIG. 1, reference numeral 1 denotes a water-cooled four-stroke parallel four-cylinder five-valve engine for a motorcycle. The engine 1 has a crankshaft 3 directed horizontally to a vehicle body frame 2 in a vehicle width direction and a cylinder. It is mounted with a forward tilt so that the axis tilts forward from the vertical. In the engine 1, a cylinder head 6 and a head cover 7 are stacked and fastened on a cylinder body 5 located at a front portion of a crankcase 4 having a built-in transmission, and a piston 8 is slidably inserted into a cylinder bore 5a of the cylinder body 5. Insert the piston 8
Is connected to the crankshaft 3 by a connecting rod 9.

On the mating surface of the cylinder head 6 on the side of the cylinder body 5, four combustion recesses 6a are provided, and a spark plug 10 is provided at the center of the inner surface of each combustion recess 6a.
Electrodes are facing.

The combustion recess 6a has three cylinders per cylinder.
Two intake valve openings 6b and two exhaust valve openings 6c are arranged and open along the periphery of the combustion recess 6a.
Each intake valve opening 6b is provided with an intake valve 11 and each exhaust valve opening 6b.
c, exhaust valves 12 are arranged to be urged in the closing direction, and the intake valve 11 is driven by an exhaust cam 12 by an intake camshaft.
Are driven to open and close by an exhaust cam shaft.

The valve mechanism of the engine 1 of this embodiment is of a side chain type (see FIG. 2), and the intake camshaft and the exhaust camshaft are formed so as to protrude from the right side wall of the engine, and the cylinder shaft is formed. It is rotationally driven by the crankshaft 3 via a timing chain arranged to pass through a chain chamber 6d extending in the direction.

The intake system of the engine 1 includes an intake port 15 for leading the intake valve opening 6b of each cylinder to the rear wall of the cylinder head 6, and an external connection port 15 for the intake port 15.
a, a throttle body 17 connected to the throttle body a via a joint 16, and an intake duct 19 connected to the throttle body 17 and opening into an air cleaner box 18. Above intake port 15, throttle body 1
The intake passage composed of the intake duct 7 and the intake duct 19 is formed so as to be substantially linear as a whole, and is disposed substantially in the vertical direction, thus minimizing the intake resistance as much as possible. The angle of the intake passage with respect to the cylinder axis is appropriately set within a range of approximately 30 to 60 degrees.

The air cleaner box 18 comprises a pair of left and right tank rails 2a, 2a constituting the body frame 2.
The fuel tank T is mounted on the rear side of the air cleaner box 18, and the fuel tank T and the air cleaner box 18 are covered with a tank cover C.

A traveling wind pressure introducing duct 60 for introducing traveling wind together with wind pressure (ram air pressure) is connected to the primary chamber upstream of the element of the air cleaner box 18. The duct 60 is made of resin and is a cylindrical body having a circular cross-section and extending forward of the vehicle body, and has a tapered shape having a slightly smaller diameter toward the upstream opening 60a. The upstream opening 60a
Is opened in the vicinity of the head pipe 2c of the vehicle body frame 2 toward the front of the vehicle body.

The intake port 15 is connected to the external connection port 1.
5a and three branch port portions 15c branching from the intake valve openings 6b. The external connection port 15a is connected to the cylinder head 6
The downstream connection boss portion 17a of the throttle body 17 is connected to the connection port 15a via the rubber ring-shaped joint 16 so that the connection port 15a is connected to the connection port 15a. 17 is supported by the cylinder head 6. The four throttle bodies 17 provided one for each cylinder are unitized via an ECU case 23 extending in the vehicle width direction.

The throttle body 17 has a built-in throttle valve 20, a buffer valve 34 and a fuel injection valve 2.
5 is held. The throttle valve 20 is disposed in a portion of each throttle body 17 near the downstream connection boss 17a, and has a circular valve plate 20.
a is bolted and fixed to the valve shaft 20b. The respective valve shafts 20b of the respective cylinder throttle valves 20 extend in the vehicle width direction and protrude outward from the throttle body 17, and the protruding portions are connected via a connecting mechanism 21. The coupling mechanism 21 has a structure capable of finely adjusting the idling opening of each throttle valve.

As shown in FIG. 2, each throttle body 17 for each cylinder has a dimension from the vehicle body center line L to a right outer end of a throttle sensor 22 described later attached to the throttle body 17 at the right end. W1 and the dimension W2 from the vehicle body center line L to the left end of the throttle valve 20 arranged on the throttle body 17 at the left end are arranged to be the same.

Straight lines X1 and X2 passing through the center of the intake passage of the first and second throttle bodies 17 and 17 from the right and parallel to the vehicle body center line L are the first and second straight lines from the right.
From straight lines Y1 and Y2 that pass through the axis of the second cylinder and are parallel to the vehicle center line L, slightly D1,
It is offset by D2 (specifically, about 2 mm). On the other hand, axes X3 and X4 passing through the intake passage centers of the third and fourth throttle bodies from the right and parallel to the vehicle body center line L pass through the axes of the third and fourth cylinders from the right. From the axis lines Y3 and Y4 parallel to the vehicle body center line L, D3 and D4 (specifically, 7 m
m, about 14 mm). In other words, the left throttle body is more offset to the right from the cylinder center toward the right side, thereby avoiding the problem that the left end throttle body projects to the left from the left wall of the cylinder block 6 to increase the width of the body frame. ing.

A throttle sensor 22 for detecting the opening of the throttle valve 20 and an ECU case 23 containing an ECU for controlling the operating state of the engine are integrated with the throttle body 17 disposed at the right end. The control unit 24 is detachably mounted by bolting.

The throttle sensor 22 constituting the control unit 24 is connected to the outwardly projecting end of the valve shaft 20b of the throttle valve 20 at the right end, and detects the rotation angle (throttle angle) of the valve shaft 20b. I do. The throttle sensor 22 is located on the side of the chain arrangement chamber 6d of the cylinder head 6, that is, in the dead space on the rear side of the rightward projecting portion of the chain arrangement chamber 6d.

The first throttle body 17
Mechanism 2 between the throttle body and the second throttle body 17
A throttle pulley 41 is mounted on 1, and the throttle pulley 41 is connected to a throttle grip (not shown) of a steering handle via a throttle cable 42. Each of the throttle valves 20 opens and closes in synchronization with the rotation of the throttle grip.

The fuel injection valve 25 is located on the bottom wall 17g of the throttle body 17 immediately upstream of the throttle valve 20, and its injection nozzle 25a is located upstream of the throttle valve and downstream of the buffer valve in the intake passage. It is attached to be. The fuel injected from the injection nozzle 25a of the fuel injection valve 25 is supplied via the injection port 17j to the throttle valve 20 at the fully closed (minimum opening) position.
Of the throttle valve 20 in the fully open (maximum opening) position, mainly colliding with the bottom wall side portion of the upstream surface (upper surface) c of the throttle valve 20.
Collides mainly with the downstream portion of the lower surface of the. Such a collision state of the injected fuel is realized by appropriately selecting the arrangement position of the injection nozzle 25a and the shape of the injection hole.
The arrow d indicates the opening rotation direction of the throttle valve 20.

The fuel injection hole 25 of the fuel injection valve 25
A fuel supply rail 26 is mounted on the portion b. The fuel supply rail 26 has a flange 26c attached to a boss 17i of the throttle body 17 by a bolt 26d.
It is tightened and fixed. The fuel supply rail 2
Reference numeral 6 denotes a cylinder having a length extending over the fuel injection valves of all cylinders. A fuel pump 28 and a fuel tank 29 are connected to the fuel supply rail 26 via a fuel supply pipe 27.

Here, reference numeral 30 in FIG. 1 denotes a fuel pressure adjusting valve which is connected to the fuel pump 28 discharge side of the fuel supply pipe 27 and adjusts the pressure of the fuel supplied to the fuel injection valve 25. The fuel pressure regulating valve 30 is connected to the fuel pump 28
This is a variable fuel pressure system that adjusts the pressure of the fuel supplied from the controller to a pressure corresponding to the control pressure. As the above-mentioned control pressure, an intake negative pressure obtained by sampling from the downstream side of the throttle valve in each intake passage and merging them is adopted.

When the throttle valve 20 is at the idling opening degree (minimum opening degree), the fuel pressure regulating valve 30 has the fuel supply rail 26 because the control pressure (intake negative pressure) is much lower than the atmospheric pressure. Adjust the fuel pressure in the lower. As a result, the pressure difference between the fuel pressure in the fuel supply rail 26 and the pressure at the fuel injection position (approximately atmospheric pressure at the upstream side of the throttle valve 20) decreases, and the fuel injection amount decreases. As a result, the ratio (dynamic range) between the minimum injection amount and the maximum injection amount of the fuel injection valve 25 can be substantially increased.

The buffer valve 34 is for alleviating a sudden change in the amount of intake air when the throttle valve 20 is suddenly opened, and has a structure of an automatic variable venturi system. This buffer valve 34 is connected to the throttle body 17.
A free piston 35 that obliquely moves into and out of the venturi passage 17d and changes its passage area is slidably inserted into the top wall 17e of the valve body 17c, and the upper end of the piston 35 is attached to the top of the valve body 17c. The working chamber 37 is located in a working chamber 37 formed by the wall 17e and the cover 36. The working chamber 37 is divided into a negative pressure chamber a and an atmospheric pressure chamber b by a diaphragm 38 airtightly connected to an upper end of the free piston 35. The pressure between the bottom wall 17g of the venturi passage 17d and the bottom surface of the free piston 35 is introduced into the negative pressure chamber a. Reference numeral 35a is a groove formed in the bottom surface of the free piston 35 in the direction of the intake passage, and forms a suction passage when the free piston 35 is fully closed. Reference numeral 39 denotes a spring for urging the piston 35 toward the minimum opening.

The bottom wall 17 of the throttle body 17
An idle passage 70 that bypasses the throttle valve 20 at the fully closed position is formed on the g side. The upstream opening 70a of the idle passage 70 opens into the injection port 17j where the injection nozzle 25a of the fuel injection valve 25 is located,
The downstream opening 70b opens slightly downstream of the throttle valve 20 at the fully closed position of the venturi passage 17d.

An idle control valve 71 for adjusting the area of the idle passage 70 is provided in the middle of the idle passage 70. The idle control valve 71 has a tapered valve portion 71a, and is configured to adjust the screw area manually to adjust the passage area.

As shown in FIG. 6, a valve capable of variably controlling the passage area or an on / off valve is employed as the idle control valve 71,
Thus, the passage area, and thus the idle speed, may be automatically controlled in accordance with the operating state. In this case, specifically, according to the engine wall temperature, the cooling water temperature, and the atmospheric temperature, the detected engine speed becomes the target idle speed which is set lower as the engine speed becomes higher. The opening degree or the duty ratio is feedback-controlled.

The bottom wall 1 of the throttle body 17
7g-side idle control valve 71 and injection nozzle 25
A heat retaining passage 72 is formed in a portion between the two. The heat retaining passage 72 extends so as to surround the bottom half of the venturi passage 17d, and engine cooling water that has passed through the water cooling jacket of the cylinder head 6 is introduced into the heat retaining passage 72. Thereby, the injection nozzle 25 of the fuel injection valve 25 is heated by the heat of the engine cooling water.
a, the idle adjustment valve 71, the portion near the throttle valve of the venturi passage 17d, and the like are constantly warmed during engine operation.

The ECU 2 of the control unit 24
Reference numeral 3 denotes an input of a throttle opening signal from the throttle sensor 22, an engine speed signal from an engine rotation sensor 31, and an air-fuel ratio signal from an O ₂ sensor 32 provided in an exhaust system, and the engine operation state. The corresponding ignition timing control signal is output to the ignition circuit 33, and the fuel injection amount and the fuel injection timing control signal are output to the fuel injection valve 25.

Here, in the engine 1 of this embodiment, the above-mentioned volume ratio (port volume / displacement per cylinder) is set to 0.15 to
Since the throttle valve 20 is arranged close to the intake valve opening 6b in order to make it 0.45 smaller than the conventional engine, the intake air flow rate is sensitive to the opening of the throttle valve 20.

On the other hand, in the engine 1 of the present embodiment, the fuel injection valve 25 is arranged on the upstream side of the throttle valve 20, so that the fuel is compared with the conventional engine in which fuel is injected to the back of the head of the intake valve. There is a concern that fuel response may be delayed.

For this reason, particularly, no-load racing in which the throttle valve 20 is rapidly opened in a no-load state (idling).
In this case, the intake air amount sharply increases in response to the opening of the throttle valve 20 in a sensitive manner. As a result, the fuel injection amount lags behind during normal rapid acceleration and adheres to the wall surface. Problems such as fuel being sucked into the combustion chamber by the flow of the intake air become remarkable, and as a result, misfire occurs at the beginning of the throttle operation in the no-load racing,
There is a concern that driving feeling may be reduced.

Therefore, in the engine 1 of the present embodiment, the above-described buffer valve 34 is provided. When the throttle valve 20 is rapidly opened, the air flow rate passing through the lower end of the piston 35 is increased as the intake air amount increases. When the negative pressure of the portion becomes higher than the urging force of the piston 35 in the closing direction, the diaphragm 38 pulls up the piston 35. In this way, the rate of increase of the intake air amount due to the rapid opening of the throttle valve 20 becomes slow, and even in the case of the above-described no-load racing, the delay in fuel response is relatively alleviated, and the occurrence of misfire can be suppressed. A decrease in driving feeling can be avoided.

On the other hand, in the present embodiment, when the fuel injection valve 25 is arranged upstream of the throttle valve 20, the injected fuel collides with the bottom wall side portion of the throttle valve 20 at the minimum throttle opening, and the maximum throttle opening occurs. At the time, the structure is designed to collide with the downstream portion of the throttle valve 20, so that atomization of the fuel is promoted, the combustion state is improved, and the fuel consumption and the exhaust gas properties are improved.

Here, as in the case of climbing a long uphill road,
When the throttle valve is widely opened and the vehicle runs continuously at a relatively low speed, a large amount of fuel is injected into the injection nozzle 25a.
From the injection nozzle 25 due to the heat of vaporization of the fuel.
a, the temperature in the vicinity of the throttle valve 20 and the idle control valve 72 decreases, and in extreme cases, the injection nozzle 2
There is a concern that icing may occur in the portion 5a and the like, and the fuel injection may not be performed smoothly, or the injected fuel may not be vaporized but become liquid and adhere to the inner surface of the Venturi passage, thereby deteriorating the driving feeling.

Therefore, in this embodiment, the cylinder head 6
The cooling water of, for example, 80 ° C. or higher that has passed through the water cooling jacket is introduced into the vicinity of the injection nozzle 25a and the vicinity of the idle control valve 71 through the heat retaining passage 72, so that the portion is always warmed by the heat of the engine cooling water. Things.
As a result, the temperature drop due to the heat of vaporization can be avoided even in the operation range so that a large amount of fuel is continuously injected as described above, and the icing and fuel adhesion can be prevented to prevent deterioration of the operation feeling.

In forming the heat retaining passage 72, the buffer valve 34 is connected to the top wall of the intake passage, that is, the head cover 7
Side, and the fuel injection valve 25 is disposed on the bottom wall side of the intake passage, and is disposed obliquely so that the fuel injection direction is along the direction of the intake air flow. A relatively large arrangement space can be obtained, so that the heat retaining passage 72, the idle passage 70, and the idle adjustment valve 71 can be arranged without any trouble.

Further, in the present embodiment, the periphery of the idle control valve 71 is also kept warm by the heat retaining passage 72, so that the above-mentioned icing and fuel adhesion can be prevented from occurring in the idle passage 70, and idling rotation can be stabilized.

In this embodiment, since the fuel injection valve 25 is disposed immediately upstream of the throttle valve 20, the idle adjustment valve 71 for adjusting the passage area of the idle passage 70 that bypasses the throttle valve 20 and the fuel injection valve 25 are provided. Valve 2
5 can be arranged close to each other, so that one heat insulating passage 7
2, both the injection nozzle 25a and the idle control valve 71 can be kept warm, and the above-described effects can be obtained while avoiding a complicated structure.

[0048]

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram schematically showing an intake device of a four-cycle engine according to one embodiment of the present invention.

FIG. 2 is a plan view showing a state in which a cylinder block and a throttle body of the engine of the embodiment are mounted on a vehicle body.

FIG. 3 is a schematic diagram showing a shape of an intake port of the engine according to the embodiment.

FIG. 4 is a sectional right side view of the engine of the embodiment.

FIG. 5 is a left side view of the motorcycle equipped with the engine of the embodiment.

FIG. 6 is a block diagram showing a case where the idle control valve in the engine according to the embodiment is feedback-controlled.

[Explanation of symbols]

 1 4 cycle engine 17d Venturi passage (intake passage) 20 Throttle valve 25 Fuel injection valve 34 Buffer valve 70 Idle passage 71 Idle adjustment valve 72 Heat insulation passage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 69/00 310 F02M 69/00 310T 310R 350B (72) Inventor Sadahisa Suzuki 2500 Shinkai, Iwata-shi, Shizuoka Yamaha Motor Co., Ltd. Inside

Claims (2)

[Claims] 1. An intake system for a four-stroke engine including an intake passage communicating with a combustion chamber and a throttle valve provided in the middle of the intake passage, wherein fuel is injected upstream of the throttle valve of the intake passage. A valve is provided, and the area of the intake passage is changed on the upstream side of the fuel injection valve of the intake passage and on the side facing the fuel injection valve in accordance with the state of intake air flowing through the intake passage. A buffer valve for reducing the rate of increase of the flow rate more slowly than the rate of increase of the intake flow rate in accordance with the opening speed of the throttle valve; and An intake device for a four-stroke engine, wherein a heat retaining passage for introducing a gas is formed. 2. The idle according to claim 1, wherein an idle passage is formed on the fuel injection valve side of the intake passage so as to bypass the throttle valve when the valve is fully closed, and the idle passage changes a passage area of the idle passage. An intake device for a four-stroke engine, wherein a regulating valve is provided, and the heat retaining passage is provided on a portion of the outer wall of the intake passage between the injection nozzle and the idle regulating valve.