JPH1077870A - Engine with supercharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten combustibility at the cold time by providing a control means for making the operating angle of an intake valve small to heat intake air at the cold time. SOLUTION: Each cylinder is provided with two intake valves 22. A valve system 29 is provided as an operating angle adjusting means for adjusting the operating angle of each intake valve 22. A control unit 14 controls the cam changeover of the valve system 29 at the cold time when the engine cooling water temperature detected by a water temperature sensor 12 is the specified value or less in a low load area with the opening of a throttle valve 9 being the specified value or less. At the cold time, the operating angle of each intake valve 22 is thus made small, and the lift quantity is made small so as to considerably reduce the intake quantity flowing into the cylinder. With the decrease of the intake quantity, the opening of an auxiliary air regulating valve 17 is enlarged to heighten intake pressure upstream of a supercharger 4 and to build up boost pressure downstream of the supercharger 4, thus heightening the temperature of intake air flowing into the cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercharged engine in which intake air is heated by a supercharger when the engine is cold to improve the combustibility.

[0002]

2. Description of the Related Art Conventionally, as an engine with a supercharger of this type, for example, disclosed in Japanese Patent Application Laid-Open No. 5-263669, the intake air is heated by the supercharger when the engine is cold and the closing timing of the intake valve is reduced. Is delayed to reduce the amount of intake air, thereby increasing the effect of heating the intake air.

[0003]

However, in such a conventional engine with a supercharger, the closing timing of the intake valve is delayed in a cold state, and the intake air once taken into the cylinder during the intake stroke is compressed. The pressure at the compression top dead center cannot be sufficiently increased at the time of idling, etc., and the turbulent energy of the intake air at the compression top dead center cannot be maintained, so that the combustion in the cold period There is a problem that the property cannot be sufficiently improved.

[0004] The present invention has been made in view of the above problems, and has as its object to enhance the combustibility of a supercharged engine with a cold engine.

[0005]

According to a first aspect of the present invention, there is provided an engine with a supercharger, comprising: a supercharger for supercharging intake air taken into the engine; and an operating angle adjusting means for adjusting an operating angle of an intake valve. Control means for heating the intake air by reducing the operating angle of the intake valve during cold operation.

An engine with a supercharger according to claim 2 is
According to the first aspect of the present invention, the closing timing of the intake valve at the time of cold is set near the bottom dead center.

An engine with a supercharger according to claim 3 is
The invention according to claim 1 or 2, further comprising air-fuel ratio control means for making the air-fuel ratio during cold operation leaner than the stoichiometric air-fuel ratio.

An engine with a supercharger according to claim 4 is
In the invention according to any one of claims 1 to 3,
One cylinder is provided with a first intake valve and a second intake valve, and the lift amounts of the first intake valve and the second intake valve in a cold state are made different.

[0009]

According to the engine with the turbocharger according to the first aspect of the present invention, the amount of intake air flowing into the cylinder is sufficiently reduced by reducing the operating angle of the intake valve at the time of cooling, so that the intake air flowing into the cylinder is reduced. In addition to being able to raise the temperature, it is possible to prevent intake backflow from the cylinder to the intake passage and to increase the pressure of the cylinder in the compression stroke, thereby increasing the flammability during cold operation and reducing the emission of unburned HC. Can be.

According to the engine with the supercharger according to the second aspect, the closing timing of the intake valve at the time of cold is set near the bottom dead center, so that the intake back flow from the cylinder to the intake passage is prevented. In addition to increasing the pressure of the cylinder in the compression stroke, it is possible to maintain the power of the intake air flow near the compression top dead center where the ignition timing is reached, thereby increasing the flammability during cold operation and reducing the amount of unburned HC emissions. be able to.

According to the third aspect of the present invention, since the air-fuel ratio control for making the air-fuel ratio leaner than the stoichiometric air-fuel ratio when the engine is cold is performed, the emission amount of unburned HC can be further reduced. it can. Even if the air-fuel ratio is reduced, the intake air temperature is increased by supercharging, so that the combustibility at the time of cooling can be ensured.

According to the engine with the turbocharger according to the fourth aspect of the present invention, the swirl swirling into the cylinder during the intake stroke is generated by making the lift amount of each intake valve different at the time of cold operation, and the flammability at the time of cold operation And the emission of unburned HC can be further reduced.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, a throttle valve 9 for restricting intake air is interposed in the middle of an intake passage 2 provided in the engine 1, and a supercharger 4 for supercharging intake air downstream of the throttle valve 9. Is interposed. In the figure, 21 is a piston, 22 is an intake valve, and 23 is an exhaust valve.

The throttle valve 9 opens when the accelerator pedal (not shown) is depressed, and the throttle valve 9 opens.
The amount of intake air taken into the engine 1 through the engine is adjusted.

An injector (not shown) is interposed in the intake passage 2. Injector opening time is 0 ~
The duty is controlled between 100%. The valve is opened by a pulse signal sent from the control unit 14, and fuel is injected into the intake passage 2.

The control unit 14 includes a rotation speed sensor 18 for detecting an engine rotation speed N,
Each of the detection signals from the air flow meter 10 for detecting the intake air amount Q is input, and the basic fuel injection amount Tp () that brings the air-fuel ratio closer to the stoichiometric air-fuel ratio based on the detected intake air amount Q and the engine rotation speed N. = K × Q / N; K is a constant).

An intake air passage 2 is provided with an auxiliary air passage 15 that bypasses the throttle valve 9 and guides intake air. An auxiliary air amount adjusting valve 17 is provided in the middle of the auxiliary air passage 15. The opening time of the auxiliary air amount adjusting valve 17 is 0 to 100.
The duty is controlled between% and is opened by a pulse signal sent from the control unit 14.

The control unit 14 receives detection signals from a rotation speed sensor 18 for detecting the engine rotation speed and a throttle opening sensor 8 for detecting the opening T of the throttle valve 9, and the throttle valve 9 is fully closed. During the idling operation at the position, the auxiliary air amount adjusting valve 17 is controlled so that the engine speed approaches a preset target speed.
Control the opening degree.

The rotation of the crankshaft of the engine 1 is transmitted to the mechanical drive type supercharger 4 via a belt 25, a pulley 24 and the like.

The intake passage 2 is provided with a bypass passage 5 for leading the intake air around the supercharger 4. A bypass flow control valve 7 is interposed in the bypass passage 5. The bypass flow control valve 7 is driven to open and close via a step motor 6.

The control unit 14 includes the intake passage 2
Pressure sensor 1 for detecting pressure P downstream of supercharger 4
Each of the detection signals from 1 is input, and the opening of the bypass flow control valve 7 is controlled such that the supercharging pressure P approaches a preset target value.

Each cylinder is provided with two intake valves 22. As operating angle adjusting means for adjusting the operating angle (valve opening angle) of each intake valve 22, a valve operating device 29 shown in FIG. 2 is provided.

The valve gear 29 includes a pair of rocker arms 30 and 31 each having a swinging tip abutting on the stem top of each intake valve 22, and a follower 32 having no contact portion with each intake valve 22. Swingably supported through the Each rocker arm 30, 31 has a small cam 33, 34
Are slid in contact with each other. Each follower 32 has a small cam 3
A large cam 35 having a profile in which the operating angle and the lift amount are larger than those of the cams 3 and 34 are brought into sliding contact with each other.

Each rocker arm 30, 31 and follower 32
Are connected to each other via a pin (not shown) responsive to the hydraulic pressure guided through the hydraulic control valve 28, and this connection is released.

Each rocker arm 30, 31 and follower 32
In the state where the connection of the small cams 3 is released, each intake valve 22
It opens and closes following 3, 34.

Each rocker arm 30, 31 and follower 32
Are connected to each other, each intake valve 22 opens and closes following the large cam 35.

As shown in FIG. 3, the operating angles and the lift amounts of the small cams 33, 34 are set smaller than those of the large cam 35. The large cam 35 opens before the top dead center of the intake stroke in which the piston 21 descends, and closes after the bottom dead center of the intake stroke. The small cams 33 and 34 open after passing the top dead center of the intake stroke, and close near the bottom dead center of the intake stroke.
The operating angles of the small cams 33 and 34 are set, for example, in the range of 30 ° to 40 ° (120 ° to 160 ° in crank angle).

The control unit 14 controls the engine cooling water temperature Tw detected by the water temperature sensor 12 in a low load region where the opening of the throttle valve 9 is equal to or less than a predetermined value.
When the temperature is lower than the predetermined value T ₁ , the bypass flow control valve 7 is closed, the small cams 33 and 34 engage in the opening and closing operations of the intake valves 22, and the engine cooling water temperature Tw rises above the predetermined value T _1. The cam switching of the valve gear 29 is controlled so that the large cam 35 is involved in the opening and closing operation of each intake valve 22 after the warm-up.

In this way, by reducing the operating angle of each intake valve 22 and reducing the lift during cold operation, the amount of intake air flowing into the cylinder is greatly reduced. By reducing the intake air amount, the opening degree of the auxiliary air amount adjusting valve 17 is increased to increase the intake air pressure upstream of the supercharger 4 and increase the supercharge pressure P downstream of the supercharger 4. Thus, the temperature of the intake air flowing into the cylinder can be increased.

Since the closing timing of each intake valve 22 is set near the bottom dead center, the stroke in which the piston 21 rises in the state where the intake valve 22 is closed is long, and the compression stroke at which the ignition timing is reached is increased. Both the intake pressure and the intake temperature in the cylinder near the dead center can be increased.

FIG. 6 is a characteristic diagram showing the relationship between cylinder volume and pressure from when the intake valve closes until the exhaust valve opens. As indicated by the broken line, the characteristics of the engine according to the present invention can increase the pressure in the compression stroke as compared with the characteristics of the conventional device indicated by the solid line. As a result, the atomization and mixing of the fuel with the air taken into the cylinder is promoted, and the combustibility at the time of cooling is enhanced.

Further, since the closing timing of each intake valve 22 is set in the vicinity of the bottom dead center, the pressure difference between the cylinder and the intake passage 2 immediately before each intake valve 22 closes increases. As the generated intake air flow increases,
By shortening the time to reach compression top dead center, maintaining the power of intake air flow near compression top dead center at the ignition timing,
Combustibility at the time of cooling can be improved.

As a result, under the condition that the air-fuel ratio is controlled to the stoichiometric air-fuel ratio, the cams involved in the opening and closing operations of the intake valves 22
When switching from 5 to the small cams 33 and 34, the discharge amount of unburned HC can be reduced from the point A to the point B as shown in FIG.

The control unit 14 controls the fuel injection amount from the injector so that the small cams 33 and 34 make the air-fuel ratio leaner than the stoichiometric ratio (stoichiometric air-fuel ratio) when the engine is cold for opening and closing the intake valves 22. I do.

By performing the control to make the air-fuel ratio leaner than the stoichiometric value at the time of cooling, the discharge amount of unburned HC can be greatly reduced from the point A to the point C as shown in FIG. Even if the air-fuel ratio is made lean, the intake air temperature is raised, so that the combustibility at the time of cooling can be ensured.

The cams involved in opening and closing the intake valves 22 while maintaining the supercharging pressure P constant are small cams 33 and 34.
Is switched to the large cam 35, the engine 1
The generated torque greatly increases, and a problem that the torque step at the time of switching becomes large can be considered.

In response to this, before switching from the small cams 33, 34 to the large cam 35, the opening degree of the bypass flow rate control valve 7 is gradually reduced to increase the supercharging pressure P, and the small cams 33, 34 At the same time as switching to the large cam 35, the opening degree of the bypass flow rate regulating valve 7 is gradually increased to perform control to lower the supercharging pressure P, so that the engine generated when the small cam 33, 34 is switched to the large cam 35. 1 to suppress the generated torque fluctuation to a small value.

Next, as another embodiment, as shown in FIG. 7, the lift amounts of the small cams 33 and 34 may be different. Also in this case, similarly to the above embodiment, the small cams 33,
The operating angle and the lift amount of 34 are set smaller than the large cam 35.

By making the lift amount of each intake valve 22 different at the time of cooling, the amount of intake air flowing into the cylinder via each intake valve 22 in the intake stroke differs, and as shown by an arrow in FIG. The power of the intake air flowing into the cylinder via the intake valve 22 becomes larger than the other, and a swirl swirling into the cylinder is generated.

By setting the closing timing of each intake valve 22 near the bottom dead center, the pressure difference between the cylinder and the intake passage 2 immediately before each intake valve 22 closes increases, and the pressure difference is generated in the cylinder. As the intake air flow increases, the time required to reach the compression top dead center is shortened, the swirl power near the compression top dead center at the ignition timing is maintained, the flammability during cold operation is increased, and unburned HC emission can be further reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view of the valve gear.

FIG. 3 is a lift characteristic diagram of the intake valve.

FIG. 4 Similarly, intake air temperature, air-fuel ratio, and unburned HC
FIG. 4 is a characteristic diagram showing a relationship between discharge amounts.

FIG. 5 is a characteristic diagram showing a relationship between an engine speed, a supercharging pressure, and a shaft torque.

FIG. 6 is a characteristic diagram showing a relationship between a cylinder volume and a pressure.

FIG. 7 is a view showing a lift characteristic of an intake valve according to another embodiment.

FIG. 8 is a perspective view showing a state of an intake air flowing into a cylinder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 4 Supercharger 5 Bypass passage 6 Step motor 7 Bypass flow control valve 8 Throttle valve opening sensor 9 Throttle valve 10 Air flow meter 11 Intake pressure sensor 12 Water temperature sensor 14 Control unit 22 Intake valve 29 Valve train 33 Small cam 34 Small cam 35 Large cam

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location F02D 41/06 305 F02D 41/06 305 320 320

Claims (4)

[Claims] 1. A supercharger for supercharging intake air taken into an engine, an operating angle adjusting means for adjusting an operating angle of an intake valve, and a control for heating the intake air by reducing the operating angle of the intake valve when the engine is cold. Means, and an engine with a turbocharger. 2. The supercharged engine according to claim 1, wherein the closing timing of the intake valve in a cold state is set near a bottom dead center. 3. The engine with a supercharger according to claim 1, further comprising air-fuel ratio control means for making the air-fuel ratio in a cold state leaner than the stoichiometric air-fuel ratio. 4. A cylinder according to claim 1, wherein a first intake valve and a second intake valve are provided in one cylinder, and lift amounts of the first intake valve and the second intake valve in a cold state are made different. An engine with a supercharger according to any one of the above.