JPH0323725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine intake device that changes the strength of intake air swirl in accordance with the temperature of an exhaust gas purification device.

2. Description of the Related Art Conventionally, engine intake devices have been known that are equipped with engine operating state detection means and swirl control means for controlling the strength of intake air swirl based on detection signals from the engine. for example,
Examples include those described in JP-A-54-74021.

The above-mentioned intake device has the effect of increasing the intake air flow velocity in a low-load operation range where the amount of intake air is small, thereby forming a swirl in the combustion chamber, increasing the combustion speed of the air-fuel mixture, and improving combustion efficiency. However, the exhaust gas temperature is low in the low-load operation range, so if the combustion efficiency of the mixture is improved in the low-load operation range as described in the above publication, the exhaust gas temperature will further decrease, and the exhaust gas temperature installed in the exhaust system will decrease. There is a drawback that the catalyst of the gas purification device does not reach the reaction temperature and exhaust gas purification is not performed.

This invention was made in order to eliminate the above-mentioned drawbacks, and includes a temperature sensor that detects the temperature of an exhaust gas purification device installed in an exhaust system, and a temperature of the exhaust gas purification device detected by the temperature sensor. An intake system for an engine capable of effectively causing a catalyst of an exhaust gas purification device to react even in a low load operating range by providing a correction means for correcting the swirl in a direction of weakening the swirl controlled by the swirl control means when the value is below the value. is intended to provide.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of an engine according to an embodiment of the present invention. In this figure, 1 is a cylinder block into which a piston 12 is inserted, 3 is a cylinder head in which a combustion chamber 4 is formed below, and 5 is an intake passage that communicates with the combustion chamber 4. Part 6, nozzle 7, throttle valve 8
The primary side intake passage 5a has a carburetor 9 equipped with a carburetor 9, and has a relatively small passage area by a partition wall 10 in the vicinity of the combustion chamber 4 of the intake passage 5.
and a secondary intake passage 5b having a relatively large passage area.

11 is an intake valve that opens and closes the intake port 5c of the intake passage 5; 12 is an exhaust passage from the combustion chamber 4; 13 is an exhaust valve that opens and closes the exhaust port 12a of the exhaust passage 12; 14 is the intake valve 11 and the exhaust valve 13; A valve operating mechanism that opens and closes at predetermined timings in synchronization with the rotation of the engine, 15 an exhaust gas purification device provided in the exhaust passage 12, 16 an exhaust gas purification device 1
This is a temperature sensor that detects the temperature of No. 5.

Reference numeral 17 denotes an operating state detection means for detecting the operating state of the engine, and is composed of a negative pressure sensor for detecting the intake negative pressure immediately downstream of the throttle valve 8. 1
8 is based on the signal from the operating state detection means 17.
It is a swirl control means for controlling the strength of the swirl (Fig. 2) S formed in the combustion chamber 4, and is composed of a control unit 19, a servo motor 20, and the above-mentioned 2.
Sub-throttle valve 21 that opens and closes the next intake passage 5b
A rotating shaft 20a of a servo motor 20 is rotatably connected to a rotating shaft 21a of the sub-throttle valve 21 via a gear mechanism 22. 23 is a correction means of the control unit 19.

Figure 2 shows the above-mentioned primary side and secondary side intake passages 5.
FIG. 5 is an explanatory plan view of a and 5b. Primary side intake passage 5
a has a relatively flat passage cross section as shown in Fig. 1, and furthermore, as shown in Fig. 2, the passage width is gradually narrowed toward the intake port 5c, and the combustion chamber is Directed in the circumferential direction of 4,
It is starting to form a strong swirl S.

FIG. 3 shows a block diagram of the control unit 19 and its correction means 23 shown in FIG.
In this figure, the control unit 19 controls the servo motor 20 based on the detection signal P of the operating state detection means 17, that is, the intake negative pressure, and is configured to control the servo motor 20 based on the detection signal P of the operating state detection means 17, that is, the intake negative pressure. It's summery. Also, the correction means 23
operates based on the output signal of the temperature sensor 16, and consists of a comparison path 27 and an auxiliary opening degree signal generation circuit 28.

FIG. 4 shows control characteristics based on the main opening signal A output from the main opening signal generating circuit 24 shown in FIG. In FIG. 4, the horizontal axis shows the intake negative pressure corresponding to the engine load, and the vertical axis shows the sub-throttle valve opening. According to the control shown in FIG. 4, the sub-throttle valve 21 shown in FIG. 1 is maintained fully closed (0°) during extremely low load operation of the engine, including idling operation where the intake negative pressure is -520 mmHg or higher. The intake air is transferred to the primary side intake passage 5a.
In contrast, during low and medium load operation of the engine in the range of -520 to 150 mmHg, which is the most frequently used intake negative pressure range, the secondary throttle valve 21
By keeping the opening constant at a relatively low opening of about 20°, the fuel consumption rate in this operating range can be minimized.

FIG. 5 shows control characteristics based on the sub-opening signal B output from the sub-opening signal generating circuit 28 shown in FIG. In this figure, the horizontal axis shows time, and the vertical axis shows the additional amount of the auxiliary throttle valve opening, and the output signal from the comparator 27 shown in FIG. From the time of input, the additional amount of auxiliary throttle valve opening increases in stages as time passes.

In the above configuration, the main opening signal generation circuit 24 of the control unit 19 shown in FIG.
Detection signal P of engine operating state detection means 17,
In other words, based on the intake negative pressure, the adder 25 generates a main opening signal A having a magnitude corresponding to the intake negative pressure at that time.
It is output to the converter 26 through. Then, the converter 26 supplies the main opening signal A to the servo motor 20 as a sub-throttle valve opening signal, and drives the servo motor 20 to rotate in a predetermined direction at a predetermined angle. As a result, the sub-throttle valve 21 is rotated at a predetermined angle via the gear mechanism 22 shown in FIG.
By changing the flow rate ratio between the next side and the secondary side intake passages 5a, 5b, the strength of the swirl S (FIG. 2) is changed as appropriate to improve combustion efficiency.

In this way, in the engine's low load operating range, the fourth
As described in the figure, by keeping the sub-throttle valve 21 fully closed or at an opening of about 20 degrees, a strong swirl S is formed in the combustion chamber 4 as shown in FIG. As a result, the combustion speed is increased and the exhaust gas temperature is lowered to a predetermined value or lower, that is, lower than the catalytic reaction temperature of the exhaust gas purification device 15 shown in FIG. 1. At this time,
In FIG. 3, the temperature sensor 16 inputs an output signal corresponding to the temperature of the catalyst to the comparator 27, so when the level of the output signal does not reach the reference voltage value corresponding to the reaction temperature of the catalyst, The sub-opening signal generation circuit 28 generates a sub-opening signal B that increases stepwise. This sub-opening signal B is input to an adder 25 and added to the main opening signal A. As a result, the servo motor 20 is driven in the valve opening direction in accordance with the increase in the sub-opening signal B, the strength of the swirl (Fig. 2) S is corrected in the direction of weakening, and the combustion speed of the air-fuel mixture is increased. suppressed. As a result, the exhaust gas temperature is ensured to be higher than the catalytic reaction temperature of the exhaust gas purifying device 15 shown in FIG. 1, and the exhaust gas purifying catalyst reacts effectively.

Once the reaction temperature of the catalyst is secured as above,
In FIG. 3, the level of the output signal of the temperature sensor 16 increases and reaches the reference voltage value of the comparator 27;
The transmission of the sub-opening signal B stops. Therefore, thereafter, the strength of the swirl is controlled only by the above-mentioned intake negative pressure.

The reason why the opening addition amount based on the sub-opening signal B is increased in stages as shown in FIG. 5 is to avoid sudden changes in the strength of the swirl.

Further, in the above embodiment, the engine operating state detecting means (FIG. 1) 17 uses only the intake negative pressure, but it may detect the engine rotational speed in addition to the intake negative pressure. Furthermore, various types of swirl control means 18 can be considered. For example, the primary side intake passage 5a and the secondary side intake passage 5b are eliminated, that is, they are combined into one passage, and the combustion in the intake passage is It is also possible to provide a deflection plate (not shown) near the chamber side end and change the strength of the swirl by adjusting the angle of this deflection plate.

As explained above, the engine intake system of the present invention includes a temperature sensor that detects the temperature of the exhaust gas purification device disposed in the exhaust system, and a temperature of the exhaust gas purification device detected by the temperature sensor. is below a predetermined value, by providing a correction means that corrects the swirl in the direction of weakening the swirl controlled by the swirl control means, while increasing the combustion efficiency as much as possible.
Even in a low load operating range, the catalyst of the exhaust gas purification device can react effectively.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an engine according to an embodiment of the present invention, FIG. 2 is a plan sectional view showing an intake passage,
FIG. 3 is a system diagram showing the control unit and its correction means, FIG. 4 is a characteristic diagram showing control using the main opening signal, and FIG. 5 is a characteristic diagram showing control using the sub-opening signal. 12... Exhaust passage, 15... Exhaust gas purification device, 16... Temperature sensor, 17... Operating state detection means, 18... Swirl control means, A... Main opening signal, B... Sub-opening signal , S...Swirl.

Claims (1)

[Claims] 1 Equipped with an operating state detection means for detecting the operating state of the engine, and a swirl control means for receiving a detection signal from the operating state detection means and controlling the strength of the swirl of intake air supplied to the engine according to the operating state. In the intake system of the engine, there is a temperature sensor that detects the temperature of the exhaust gas purification device disposed in the exhaust system, and when the temperature of the exhaust gas purification device detected by the temperature sensor is below a predetermined value, the swirl control is performed. An intake system for an engine, comprising a correction means for correcting a swirl controlled by the means in a direction of weakening the swirl.