JPH05141251A - Internal combustion engine with mechanical supercharger - Google Patents

Abstract

PURPOSE:To improve a combustion condition in the case of low speed and low load operation at the time of cold operation of a engine. CONSTITUTION:A throttle valve 12 is provided in an intake passage 2 in the downstream of a supercharger 5, and the intake passage 2 between the supercharger 5 and the throttle valve 12 is connected to a jet stream hole 8, provided in an internal wall surface of an intake port 7 of an engine 1, by a communication path 9. By throttling the throttle valve 12 by actuating the supercharger 5 at an engine cold time, a delivery pressure of the supercharger and its temperature at low speed time are increased. In this way, an intake air temperature of the engine is increased and supercharger delivery air of high temperature and high pressure from the jet stream hole 8 is also injected, and since large disturbance is generated in a mixture in a combustion chamber 1a, combustion in the case of low speed and low load operation is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine with a mechanical supercharger used for a vehicle engine or the like, and more particularly to an internal combustion engine which operates a supercharger to cool intake air by compression when the engine is cold.

[0002]

2. Description of the Related Art In cold engine operation, the temperature of the combustion chamber wall is low, and the air-fuel mixture after compression may be cooled on the wall surface of the combustion chamber and the temperature may not rise sufficiently. The speed tends to decrease and the combustion state tends to deteriorate. Conventionally, in order to compensate for this deterioration of the combustion state, stable combustion is performed by increasing the amount of fuel during cold to form a rich mixture.

However, in addition to the deterioration of engine fuel efficiency due to an increase in fuel, there are cases in which smoldering of the spark plug occurs during cold conditions and the amount of HC and CO generated due to combustion of a rich air-fuel mixture. Further, since the exhaust gas temperature is low due to the deterioration of combustion, the exhaust gas purification device using a catalyst does not sufficiently purify the exhaust gas in the cold state because the catalyst temperature delays reaching the active region, and the above-mentioned HC and CO generation amounts With the increase, the exhaust emission during cold tends to be deteriorated.

In order to solve this problem, there is known an engine in which a mechanical supercharger is operated to heat intake air by compression when the engine is cold. This is because by raising the intake air temperature in advance, even if the combustion chamber temperature is low, the mixture temperature after compression is maintained at a sufficiently high temperature so that good combustion can be obtained. An example of this type of engine is disclosed in Japanese Patent Laid-Open No. 61-19933.

The engine disclosed in the above publication is provided with a supercharger mechanically driven from the engine through a clutch. Under normal operating conditions, the clutch is connected in the medium and high load operating range of the engine to perform supercharging. At the same time, when the engine is cold, the clutch is engaged even in the low rotation and low load region to expand the supercharging operation region. By performing supercharging operation even during low load operation, intake air that has become hot due to supercharging is supplied to the engine to improve the combustion state and promote warm-up.

However, when the intake air is heated only by using the supercharger as in the above-mentioned Japanese Patent Laid-Open No. 61-19933, when the engine is operated at low load and low speed after starting, Since the compression ratio does not rise, a sufficiently high intake air temperature cannot be obtained when the outside air temperature is low. To solve this problem, the applicant of the present application has filed a prior application (Japanese Patent Application No. 3-76374).
No.), a throttle valve is provided in the intake passage on the downstream side of the supercharger,
We have proposed a supercharging control device that throttles the intake passage on the downstream side of the supercharger when heating the intake air. If throttle resistance is applied to the intake passage on the downstream side of the supercharger, the compression ratio of the supercharger will increase and the discharge temperature will also rise. It becomes possible to do.

[0007]

As described above, by performing intake air heating using the supercharger when the engine is cold,
It is possible to prevent deterioration of the combustion state due to cooling of the air-fuel mixture in the combustion chamber. However, even if the intake air is heated when the engine is cold, the combustion state may still be insufficient during low speed and low load operation as compared to high speed and high load operation.

During normal operation, turbulence of the air-fuel mixture is generated in the combustion chamber by the fresh air flowing from the intake port, and this turbulence accelerates the air-fuel mixture combustion speed and promotes combustion. In high-speed high-load operation, the turbulence of the air-fuel mixture is sufficiently large and the combustion state is good, but in low-speed low-load operation the turbulence of the air-fuel mixture in the combustion chamber decreases because the flow velocity of the intake air flowing into the combustion chamber decreases. There is a problem that it is small and a sufficient burning rate cannot be obtained.

In low-speed low-load operation when the engine is cold, the deterioration of the combustion state is large because the decrease in combustion speed due to the reduction in turbulence is accompanied by the decrease in combustion speed due to the decrease in mixture temperature. If intake air heating is performed as described above, combustion deterioration due to a decrease in air-fuel mixture temperature can be prevented, but combustion deterioration due to reduced turbulence during low speed low load operation still exists, so intake air heating is performed during low speed low load operation. The improvement of the combustion state is not sufficient by itself.

As means for preventing deterioration of combustion due to reduction of turbulence during low speed and low load operation, an intake jet hole is provided on the inner wall of the intake port near the intake valve, and air is jetted from this jet hole toward the intake valve. There is a known device (see Japanese Patent Publication No. 56-50102). This is to improve the combustion state by causing a large turbulence in the combustion chamber when the intake valve is opened by the air flow from the jet hole.

However, in these devices, the air jetted from the jet holes is introduced from the upstream side of the throttle valve or from another intake port, and due to the pressure difference between the intake port and the atmospheric pressure or the pressure difference caused by the pressure fluctuation of the intake port. It is ejected from the indignation hole. However, since the pressure difference is limited and the jet velocity generated thereby is small, the turbulence generated in the combustion chamber is relatively small. It is also possible to provide an air pump or the like in order to increase the jet velocity and inject the pressurized air from the jet holes, but this is not preferable because it complicates the configuration and causes a cost increase.

Further, in low-speed low-load operation when the engine is cold, combustion is deteriorated due to a decrease in turbulence and combustion is deteriorated due to a decrease in mixture temperature. Therefore, the turbulence is increased simply by increasing the jet speed. The combustion condition is not sufficiently improved by itself. Therefore, in order to obtain a sufficient combustion improvement effect, it is necessary to separately provide a heating device to preheat the air jetted from the indignation hole, which further complicates the configuration and raises the cost.

In view of the above problems, the present invention is provided with a means capable of improving the combustion state by heating the air-fuel mixture and increasing turbulence in a low-speed low-load operation while the engine is cold, with a simple structure. An object is to provide an internal combustion engine with a mechanical supercharger.

[0014]

According to the present invention, there is provided a mechanical supercharged air and a throttle valve in the mechanical downstream intake passage,
In an internal combustion engine in which the turbocharger is operated while the engine is cold and the intake passage is throttled by the throttle valve to perform intake compression heating by the supercharger, a jet hole that directs the engine intake valve to the inner wall surface of the engine intake port, An internal combustion engine with a mechanical supercharger is provided, which is provided with a communication passage for guiding intake air in an intake passage between the supply air and the throttle valve to the jet hole.

[0015]

When the engine is cold, the throttle valve restricts the intake passage on the downstream side of the supercharger, so that the compression ratio of the supercharger increases and the discharge temperature of the supercharger rises. The intake air is depressurized to the normal supercharging pressure by passing through the throttle valve, but the friction loss and eddy loss at the throttle valve are large, so there is almost no temperature drop due to expansion, and the intake air of high temperature is supplied to the engine. To be done.

Further, the jet hole of the intake port communicates with the intake passage between the supercharger and the throttle valve, and high temperature and high pressure supercharger discharge air is ejected from the jet hole, so that an air pump and a heating device are installed. The jet velocity and temperature can be increased without using. Therefore, the mixture temperature can be kept high even during low-speed low-load operation during cold engine operation, and a large turbulence can be generated in the combustion chamber.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. In the figure, 1 is an engine, 2 is an intake passage of the engine, 3 is a throttle valve that continuously changes an intake flow rate in accordance with an operation of an accelerator pedal (not shown) by a driver, and 5 is intake air on the downstream side of the throttle valve 3. It is a supercharger installed in the passage.

In this embodiment, the supercharger 5 is a positive displacement compressor, and the pulley 4 provided on the crankshaft 4 of the engine 1 is used.
It is mechanically driven by a belt or the like from a through the electromagnetic clutch 6. Indicated at 15 in the drawing is an intake bypass passage that bypasses the supercharger 5 and connects the intake passage downstream of the throttle valve 3 and the intake passage on the outlet side of the supercharger. The intake bypass passage 15 is provided with a bypass control valve 16 so that the air flow rate through the intake bypass passage 15 can be continuously adjusted. Reference numeral 17 denotes an actuator such as a step motor that opens and closes the bypass control valve 16.

The bypass control valve 16 is used for adjusting the engine supercharging pressure during normal operation of the engine.
That is, if the opening degree of the bypass control valve 16 is increased, the amount of air that recirculates from the discharge side of the supercharger 5 to the inlet side through the intake bypass passage 15 increases, so the differential pressure before and after the supercharger decreases, and The feeder discharge pressure also drops. On the contrary, if the opening degree of the bypass control valve 16 is reduced, the discharge pressure of the supercharger rises.
As will be described later, the bypass control valve 16 is used during engine warm-up operation.
Is held fully closed.

Further, in this embodiment, a throttle valve 12 in the shape of a butterfly valve is provided in the intake passage on the discharge side of the supercharger downstream of the confluence of the bypass passage 15. As will be described later, the throttle valve 12 is controlled in opening degree according to the engine intake air temperature when the engine is cold. When the opening degree of the throttle valve 12 decreases, the throttle resistance of the intake passage on the downstream side of the supercharger increases, so that the supercharger discharge pressure rises even at the same rotational speed. Therefore, the discharge temperature of the supercharger rises due to the increase of the compression ratio, and the engine intake air temperature can be kept high even when the outside air temperature is low. The throttle valve 12 is held fully open during high-speed, high-load operation after the engine has been warmed up. Since the throttle valve 12 is in the shape of a butterfly valve, its resistance is small when it is fully opened, and intake resistance does not occur during high-speed and high-load operation. The temperature drop when passing through 12 can be reduced. Indicated at 13 in the drawing is an actuator such as a stepper motor for driving the throttle valve 12.

In this embodiment, a jet hole 8 is provided on the inner wall surface 7 of the intake port of the engine 1 and is connected to the intake passage 2 between the supercharger 5 and the throttle valve 12 via a communication passage 9. There is. The jet hole 8 is opened tangentially to the cross section of the combustion chamber 1a, and is directed to the interval formed between the intake valve 10 and the valve seat when the intake valve 10 is opened. Therefore, the air ejected from the jet holes 8 enters the combustion chamber 1a through this interval when the intake valve 10 is opened, and produces the swirling flow shown by the arrow S in the figure. As a result, the air-fuel mixture in the combustion chamber 1a is greatly disturbed, and the combustion state is improved.

In this embodiment, in order to detect the warm-up state of the engine, a cooling water temperature sensor 21 for detecting the cooling water temperature in the engine cooling water passage, and an intake air for detecting the engine intake air temperature in the vicinity of the engine inlet of the intake passage 2 are provided. In addition to the temperature sensor 18, the throttle valve 3 has a throttle sensor 22 for detecting the throttle valve opening, the crankshaft 4 has a rotational speed 23 for detecting the engine speed, and the throttle valve of the intake passage 2 An air flow meter 25 for detecting the intake air flow rate is provided on the upstream side of the valve 3.

Reference numeral 31 in the drawing denotes an electronic control unit (ECU) for controlling the engine. In this embodiment, the ECU
31 is a central processing unit (CPU) 33, a random access memory (RAM) 34, a read only memory (ROM)
A digital computer having a configuration in which the bidirectional bus 38 connects the 35, the input port 36, and the output port 37 to each other is used.

The input port 36 of the ECU 31 has a cooling water temperature sensor 21 and an intake air temperature sensor 1 for main supercharging control.
8, a rotation speed sensor 23, an air flow meter 25, and a throttle sensor 22 are connected, and a cooling water temperature, an engine intake air temperature, an engine rotation speed, an intake air flow rate, and a throttle opening are input respectively. Also, the output port 3 of the ECU 31
7 is an actuator 17 of the bypass control valve 16 and an actuator 13 of the throttle valve 12 via a drive circuit (not shown).
Connected to the bypass control valve 16 and the throttle valve 12 to change the opening, and also connected to the electromagnetic clutch 6 to connect the clutch O.
N / OFF is controlled.

The supercharger 5 operates according to the engine load during normal operation (after completion of engine warm-up). The solid line A in FIG. 2 shows the ON / OFF region of the clutch 6 during normal operation. In the figure, the horizontal axis represents the engine speed N and the vertical axis represents the intake air amount Q / N per engine revolution as a parameter representing the engine load. As can be seen from the figure, the supercharger 5 is controlled so as to operate (the clutch 6 is turned on) only in the medium and high load range during the normal operation.

FIG. 3 is a diagram showing the relationship between the opening degree of the bypass control valve 9 and the load condition during normal operation. The vertical axis represents the opening degree θb of the bypass control valve 16 and the horizontal axis represents the throttle opening degree θ.
indicates t. As you can see, bypass control valve 1
No. 6 is fully opened in the low load region where the throttle valve opening is small during normal operation to reduce the supercharger drive load, but in the middle and high load regions the opening decreases with increasing load and the supercharging pressure is reduced. I am trying to increase the output by raising it. Further, in the high load region, the bypass control valve 16 is fully closed and controlled so as to obtain the maximum boost pressure.

Next, the intake air heating operation when the engine temperature is low according to this embodiment will be described. In the present embodiment, when it is determined from the output of the cooling water temperature sensor 21 that the engine is in the low temperature state, the clutch 6 is connected and the supercharger 5 is operated even in the light load state. This is because the intake air is compressed by the supercharger 5 and the intake air temperature is raised by the compression work.

Dotted line B in FIG. 2 shows the operation control line of the supercharger during cold operation. In this embodiment, when the temperature of the cooling water is below a predetermined value (for example, 50 ° C.), it is determined that the engine is in the cold state, and the electromagnetic clutch 6 is operated by the operation line indicated by the dotted line B instead of the operation line in the normal state. ON / OFF of. As shown in the figure, during cold conditions, all except for the case where the engine is operating at extremely low load and low rotation speed (that is, when the turbocharger is operated, the engine may stop due to drive loss) The turbocharger operates in the area.

When the supercharger 5 is operated when the engine is cold, the bypass control valve 16 is held in the fully closed position,
The engine intake air temperature control is performed by changing the opening degree of the throttle valve 12. In the present embodiment, the opening degree of the throttle valve 12 is feedback-controlled based on the engine intake air temperature detected by the intake air temperature sensor 18 so that the engine intake air temperature reaches a preset target value.

FIG. 4 shows the target value of the engine intake air temperature (the intake air temperature on the downstream side of the throttle valve). As can be seen from FIG. 4, the target value of the intake air temperature is set according to the value of the cooling water temperature TW, and the lower the cooling water temperature TW, the higher the
The cooling water temperature TW is set to be lower as it is higher.
The lower the cooling water temperature TW, the higher the intake air temperature target value is set because the intake pipe and intake port temperatures are lower when the cooling water temperature is lower and the intake air passes through these parts. This is because it takes into consideration the fact that the temperature drop when performing is large.

In order to protect the supercharger 5, the intake air temperature when the cooling water temperature TW is extremely low should be as high as possible within the range where the supercharger outlet temperature does not become excessive (for example, around 100 ° C. at maximum). ) Is set. By performing feedback control of the throttle valve 12 based on the engine intake air temperature in this manner, the engine intake temperature can always be maintained at the set value without being affected by the atmospheric temperature and the engine operating conditions.

When the opening degree of the throttle valve 12 is adjusted while the engine is cold, the discharge pressure and temperature of the supercharger rise as the opening degree of the throttle valve 12 decreases. As mentioned above, the intake port inner wall surface 7
Since the jet hole 8 is connected to the intake passage 2 between the supercharger 5 and the throttle valve 12 via the communication passage 9, the high temperature and high pressure from the jet hole 8 is generated during the above-mentioned intake heating operation. The dispenser discharge air is injected. The higher the discharge pressure of the supercharger, the higher the flow velocity of the air injected from the jet holes 8, and the greater the turbulence due to the swirling flow generated in the combustion chamber 1a.

Accordingly, when the engine is cold, the smaller the degree of opening of the throttle valve 12, that is, the lower the temperature of the engine, the larger the turbulence of the air-fuel mixture produced in the combustion chamber, and the greater the effect of improving combustion. Moreover, since the air injected from the jet holes 8 is also at a high temperature like the intake air supplied to the engine through the throttle valve 12, the air-fuel mixture in the combustion chamber 1a is not cooled by the injection air.

Therefore, by injecting a part of the supercharged air from the jet holes 8 as in the present embodiment, a larger combustion improving effect is obtained as the engine temperature is lower, and combustion deterioration at low temperature does not occur. .. FIG. 5 shows a flowchart of the intake air heating control operation of this embodiment. This routine is executed by the ECU 3 described above.
1 is executed at regular time intervals (for example, every 16 milliseconds). Note that, for this control, the ECU 31 controls the ECUs shown in FIGS.
Is stored in the ROM 35, and the following control is performed based on these.

When the routine starts in FIG. 5, the engine speed N, the intake air flow rate Q, the throttle opening θt, the cooling water temperature TW, and the engine intake temperature TS are read from the above-mentioned sensors at step 100, and at step 105, the load parameter Q. / N is calculated. Next, at step 110, it is judged if the engine is in a low temperature state. In the present embodiment, the engine cooling water temperature TW is used, and if TW <50 ° C., it is determined that the engine is in a low temperature state and step 11
The intake air heating operation of steps 5 to 160 is performed.

That is, at step 115, it is judged from the engine speed N and the load parameter Q / N based on the relationship of the dotted line B of FIG. If the supercharger 5 is operable, intake air heating by the supercharger is performed, and a valve closing signal is output to the actuator 17 of the bypass control valve 16 in step 120 to fully close the bypass control valve 16. Next, at step 125, the target value of the engine intake air temperature is set from the cooling water temperature TW based on FIG. 4, and at step 130, the opening degree of the throttle valve 12 is set based on the difference between this target temperature and the actual intake air temperature TS. Feedback control is performed, and in step 135, the clutch 6 is turned on to operate the supercharger 5. As a result, when the engine intake air temperature is lower than the target value, the opening degree of the throttle valve 12 decreases, and conversely, when the engine intake air temperature is higher than the target value, the opening degree increases, and the engine intake air temperature TS is always appropriate according to the cooling water temperature TW. Maintained at the value. Further, from the jet hole 8 provided in the intake port, the higher the temperature of the engine is, the higher the temperature and the pressure of the air are jetted, and the air-fuel mixture in the combustion chamber 1a is greatly disturbed.

If it is determined in step 115 that the supercharger cannot be operated, intake air heating is not performed. That is, in step 150, the bypass control valve 16 is fully opened to supply intake air to the engine through the bypass passage 15, and in step 155, the throttle valve 12 is fully opened to reduce intake resistance, and in step 160, the clutch is held in the OFF state. Do not operate the turbocharger.

When TW ≧ 50 ° C., that is, when it is determined in step 110 that the warm-up is completed, the routine proceeds to step 170, where supercharging pressure control during normal operation is performed. That is, in step 170, it is judged from the supercharger operation line (solid line A in FIG. 2) after the completion of warm-up whether or not the supercharger operation is necessary. Step 17
5, the opening setting value θb of the bypass control valve is determined from the throttle valve opening θt based on FIG. 3, and the actuator 17 is driven to set the bypass control valve opening to θb.
Next, in step 180, the throttle valve 12 is fully opened, and then in step 185, the clutch 6 is turned on to operate the supercharger.

As a result, after the completion of warming up, the supercharging pressure is controlled to an appropriate value according to the engine load condition. If it is determined in step 170 that the supercharger operation is not necessary, step 150 and subsequent steps are executed to operate the bypass control valve fully open (step 150), the throttle valve fully open (step 155), and the clutch off (step 160). I do.

Next, FIG. 6 shows a second embodiment of the present invention.
6, the same reference numerals as those in FIG. 1 denote the same elements as those in FIG. In this embodiment, the injection hole 8 is selectively switched between an intake passage on the discharge side of the supercharger (upstream side of the throttle valve 12) and an intake passage on the upstream side of the throttle valve 3 by an electromagnetic three-way switching valve 11a which is switched by the ECU 31. A check valve 11b for preventing intake air from flowing backward from the electromagnetic three-way switching valve 11a side to the throttle valve 3 upstream side is provided in the communication passage 9b communicating with the throttle valve 3 upstream side. Has been.

As can be seen from FIG. 5, in the above-described embodiment, the throttle valve 12 is held fully open when the supercharger 5 is not operating in order to reduce the intake resistance. Therefore, there is no differential pressure before and after the throttle valve 12, and air is no longer ejected from the jet holes 8. Since the supercharger 5 is prohibited from operating at the time of extremely low load low speed operation when the engine is cold, in the above-described embodiment, neither intake air heating nor air injection is performed at the time of extremely low load low speed operation, and improvement of the combustion state cannot be obtained. It will be.

In this embodiment, in order to prevent this, the ECU
When the operation of the supercharger 5 is stopped (the clutch 6 is OFF), the numeral 31 switches the electromagnetic three-way switching valve 11a so that the jet hole 8 and the upstream side of the throttle valve 3 are communicated with each other. When the supercharger is not operating, a negative pressure is generated in the vicinity of the intake port. Therefore, by performing the switching operation in this manner, the jet port 8 is operated according to the pressure difference between the intake port and the atmospheric pressure on the upstream side of the throttle valve 3. Air is injected and turbulence can be generated in the combustion chamber 1a. The check valve 11b is provided to prevent the supercharger discharge air from flowing back to the upstream side of the throttle valve through the communication passage 9b when the electromagnetic switching valve 11a fails.

In the above embodiment, when the intake air is heated when the engine is cold, the bypass control valve 16 is fully closed and the throttle valve 12 is used to control the engine intake air temperature. Conversely, it is also possible to perform feedback control of the bypass control valve 16 based on the engine intake air temperature while maintaining the throttle valve 12 at a constant opening during intake air heating.

[0044]

According to the present invention, the intake air is heated by using the supercharger and the throttle valve when the engine is cold, and at the same time, a part of the high temperature and high pressure supercharger discharge air is discharged from the jet holes provided in the intake port. By injecting the air-fuel mixture to generate turbulence of the air-fuel mixture in the combustion chamber, it is possible to increase the temperature of the air-fuel mixture and increase the turbulence, and to significantly improve combustion in low-speed low-load operation when the engine is cold. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of an internal combustion engine with a mechanical supercharger of the present invention.

FIG. 2 is a diagram showing a supercharger operation region of the embodiment.

FIG. 3 is a diagram showing a bypass control valve opening setting according to the embodiment.

FIG. 4 is a diagram showing a relationship between an engine intake air temperature target value and a cooling water temperature in the above embodiment.

FIG. 5 is a flowchart showing an intake air heating control operation of the above embodiment.

FIG. 6 is a schematic view showing the configuration of an embodiment of the internal combustion engine with a mechanical supercharger of the present invention, which is different from FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Intake passage 3 ... Throttle valve 5 ... Supercharger 8 ... Jet hole 9 ... Communication passage 12 ... Throttle valve 15 ... Intake bypass passage 16 ... Bypass control valve 31 ... Electronic control unit (ECU)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 45/00 Q 8109-3G F02M 23/14 7114-3G 31/04 B 8923-3G

Claims (1)

[Claims] 1. A mechanical supercharger and a throttle valve in the mechanical downstream side intake passage, wherein the supercharger is operated when the engine is cold and the intake passage is throttled by the throttle valve. In an internal combustion engine that performs intake compression heating, a jet hole that points the engine intake valve on the inner wall surface of the engine intake port, and a communication passage that guides the intake air in the intake passage between the supercharger and the throttle valve to the jet hole. An internal combustion engine with a mechanical supercharger characterized by being provided with.