JPH0745831B2 - Supercharged engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a supercharged engine in which supercharging is performed by an exhaust turbo type supercharger.

(Prior Art) In an engine that performs supercharging by an exhaust turbocharger, the compressor of the supercharger is arranged in the intake passage, while the turbine of the supercharger connected to this compressor is installed in the exhaust passage. The compressor is rotated by rotating the turbine by the energy of the exhaust gas.
The intake air is compressed, that is, supercharged. When an exhaust turbo type is used as the supercharger in this way, generally, a bypass passage for bypassing the exhaust gas is provided to the turbine, and a waste gate valve is provided in this bypass passage to prevent the turbocharger. When the boost pressure exceeds a predetermined maximum boost pressure, the waste gate valve is opened to prevent the boost pressure from exceeding the maximum boost pressure.

As described above, in the engine provided with the exhaust turbo type turbocharger, when the exhaust energy is small, for example, at the time of low load during steady running, the drive loss of the supercharger becomes large and the fuel consumption is improved. It is not desirable. For this reason,
As shown in JP-A-60-127428, in an engine equipped with an exhaust turbocharger, when the load is low, both the intake air and the exhaust gas bypass the supercharger to reduce the supercharge ability of the supercharger. Therefore, there are also proposals for improving fuel efficiency.

By the way, in an Otto type engine represented by a gasoline engine, its load control is performed by adjusting the intake air amount by adjusting the opening degree of the throttle valve provided in the intake passage over the entire operating range. Done by The throttle valve is arranged in the intake passage in series with (the compressor of) the supercharger. Of course, in the case of supercharging with an exhaust turbo supercharger in contrast to the engine load control with a throttle valve arranged in the intake passage, the opening degree of this throttle valve increases The supercharging pressure will be increased, but if the supercharging pressure becomes too large, it will lead to engine damage, etc., so the maximum supercharging pressure will be regulated using the waste gate valve described above. .

(Problems to be Solved by the Invention) As described above, in the engine load control using the throttle valve provided in the intake passage, the throttle valve is always higher than the pressure downstream of the throttle valve in the partial load region. The upstream pressure becomes large, and throttling loss, that is, so-called pumping loss exists. In the case where the exhaust turbo type supercharger is provided, the supercharger performs extra work by the amount of the throttle loss, in other words, the fuel consumption deteriorates due to the exhaust pressure increase.

Incidentally, as in the article of the above publication, in the case of only bypassing both the intake air and the exhaust gas at the time of low load to the supercharger, it is impossible to prevent deterioration of fuel consumption due to throttle loss of the throttle valve at high load. Is.

The present invention has been made in consideration of the above circumstances,
An object of the present invention is to provide a supercharged engine capable of improving fuel consumption by reducing throttle loss of a throttle valve in a wide range from low load to high load while controlling engine load. It is in.

(Means and Actions for Solving Problems) In order to achieve the above-mentioned object, according to the present invention, an exhaust turbo-type supercharger for supercharging using exhaust energy, and the supercharger With a supercharger having a bypass passage for bypassing exhaust gas, a wastegate valve provided in the bypass passage for opening and closing according to a supercharging pressure, and a throttle valve opened in response to an accelerator In an engine, load detection means for detecting an engine load, and a wastegate valve opening correction for opening the wastegate valve regardless of supercharging pressure when the engine load detected by the load detection means is less than a predetermined load And the engine load detected by the load detection means is equal to or more than the predetermined load, the throttle valve is forcibly opened regardless of the accelerator position. A throttle valve opening correction means, and a control means for controlling the engine load by the wastegate valve when the engine load detected by the load detection means is equal to or higher than the predetermined load. There is.

With such a configuration, when the engine load is less than the predetermined load, the engine load control is performed by the throttle control, while the exhaust gas is bypassed with respect to the supercharger to reduce the supercharging functional force and reduce the throttle loss. It is prevented that the driving loss of the supercharger is reduced and becomes large.

On the other hand, when the engine load is equal to or higher than the predetermined load, the throttle valve is forcibly opened so that throttle loss does not occur, while the engine load control is performed by the wastegate valve, and the turbocharger is used for the throttle loss. Doing unnecessary work will be prevented. Therefore, the throttle loss of the throttle valve can be reduced in a wide range from low load to high load while controlling the load on the engine.

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

In FIG. 1, the engine body 1 is a reciprocating in-line four cylinder having four cylinders (combustion chambers) 2, and an intake port 3 and an exhaust port 4 opening to each cylinder 2 are
The intake valve and the exhaust valve (not shown) are opened and closed at known timings in synchronization with the engine output shaft.

The intake passage 5 connected to the intake port 3 has a surge tank 6 in the middle thereof. The surge tank 6 and each intake port 3 are connected by an independent intake passage 7 which is independent of each other, and each independent intake passage 7 is provided with a fuel injection valve 8. Further, in the common intake passage 9 that supplies intake air to the surge tank 6 in the intake passage 5, an air cleaner 10, an air flow meter 11, a compressor 12a of the supercharger 12, and a throttle valve 13 are sequentially arranged from the upstream side to the downstream side. It is arranged.

On the other hand, the turbine 12b of the supercharger 12 is disposed in the exhaust passage 14 connected to the exhaust port 4, and when the turbine 12b is rotated by receiving exhaust energy, the compressor 12a is rotated via the shaft 12c. Will be supercharged. A bypass passage 15 that bypasses the turbine 12b is formed in the exhaust passage 14, and this bypass passage is opened and closed by a waste gate valve 16. When the boost pressure exceeds a predetermined value, the waste gate valve 16 is opened by the actuator 17 so that the boost pressure does not exceed a predetermined maximum boost pressure.

In FIG. 1, reference numeral 18 is a control unit composed of, for example, a microcomputer. The control unit 18 receives signals from the sensors 19, 20, 21 and outputs them to the actuator 17. The sensor 19 detects the engine speed, the sensor 20 detects the displacement position of the accelerator pedal 22 linked to the throttle valve 13, that is, the accelerator opening (throttle opening), and the sensor 21 detects the surge. The pressure in the tank 6, that is, the intake pressure is detected. It should be noted that the control unit 18 also has a function of injecting an amount of fuel determined based on the engine speed and the intake air amount measured by the air flow meter 11 from the fuel injection valve 8 at a predetermined timing. Is well known, and the description thereof is omitted.

Next, the load control portion of the engine by the control unit 18 will be described. Basically, as shown in FIG. 2, a predetermined engine load (intake pressure P in the surge tank 6
Is almost atmospheric pressure Po- (under the broken line in FIG. 2), the wastegate valve 16 (all abbreviated as W / B in the drawing) is fully opened and the engine load control is performed at low load. Is performed by the throttle valve 1 as in the conventional case. When the load is high, the throttle valve 13
Increase the opening of at least to the extent that throttling loss does not occur (it may be fully open), and the wastegate valve 16
The load of the engine is controlled by adjusting the opening degree of. That is, in the region where supercharging is performed by the supercharger (in the embodiment, as described above, this supercharging region is set as a region where the intake pressure P is substantially equal to or higher than the atmospheric pressure Po), the intake pressure P Before reaching the maximum boost pressure,
The smaller the wastegate valve 16 opening, the supercharger 12
The amount of exhaust gas provided to (the turbine 12b) increases, and the intake pressure, that is, the amount of intake air, increases, and the output increases. Therefore, even if the throttle valve 13 is opened wide enough to prevent throttling resistance, the output of the engine can be arbitrarily changed by adjusting the opening degree of the waste gate valve 16. More specifically, when the load is high, the wastegate valve 16 may be operated in the closing direction as the load increases.

By performing the engine load control in the manner shown in FIG. 2 described above, the pressures on the upstream side and the downstream side of the throttle valve 13 become as shown in FIG. That is, the third
In the figure, α1 shows how the pressure downstream of the throttle valve 13 changes, and α2 and α3 show how the pressure upstream of the throttle valve 13 changes. Of these α2 and α3, α2 is the conventional one (throttle valve 13 The load control is performed over the entire operating range by only 13), and α3 is the case of the present invention. In FIG. 3, α3 is the same as α1 when the intake pressure P is equal to or higher than Po, but in the drawing, α3 is drawn so as not to overlap with α1 in order to clearly show it. As is clear from FIG. 3, in the case of securing a certain engine torque, the amount corresponding to the pressure difference ΔP between α2 and α1 has conventionally been a throttle loss, resulting in deterioration of fuel consumption. It is possible to substantially eliminate ΔP, and the fuel economy is improved by the amount that ΔP is eliminated.

By the way, in the exhaust turbo-type supercharger 12, the responsiveness due to so-called turbo lag becomes a problem, but this responsiveness point and a smooth transition from load control by the throttle valve 13 to load control by the wastegate valve 16 This is taken into consideration in FIG. That is, FIG. 4 shows that the load control area by the wastegate valve 16 is limited to the basic load control switching shown in FIG. 2, and the engine speed N is N ₂ or more. The load control by the waste gate valve 16 is performed only in the high rotation region and the intake pressure P is Po or higher, and the load control by the throttle valve 13 is performed in the other regions. Further, in the low engine speed range where the engine speed N is N ₁ (N ₁ <N ₂ ) or less, the wastegate valve 16 is fully closed in order to eliminate the turbo lag as much as possible, and the engine speed N is N ₁
Between N ₂ and N ₂ , there is a switching region where a smooth transition from load control by the throttle valve 13 to load control by the wastegate valve 16 is performed.

FIG. 5 shows a specific control example in the switching area. In the FIG. 5 (a), is shown how a change in the relationship between the intake pressure P and the accelerator opening based on the engine rotational speed N, when the engine rotational speed N is high rotation (N ₂ -X _2-wire ) Indicates that the accelerator opening degree when the intake pressure P becomes the atmospheric pressure Po is larger than that in the low rotation (N ₁ -X ₁ line). Then, in FIG. 5 (b), in consideration of the relationship as shown in FIG. 5 (a), as the engine speed N becomes smaller, the wastegate valve becomes smaller in the switching region even when the accelerator opening is the same. 16 is set to the closing direction and the lower the engine speed, the more wastegate valve 16
It is set so that the accelerator opening at the time of shifting to load control by is small (the _one corresponding to X ₁ is the Y ₁ line,
Also, the one corresponding to X ₂ is shown by the Y ₂ line). The opening of the throttle valve 13 is set to be proportional to the accelerator opening, but the opening of the throttle valve 13 at the time when the load control by the wastegate valve 16 is performed has a sufficiently small throttle loss. Have been associated with.

Based on the above, the control unit 18 causes the fourth
Regarding the case of performing the control shown in FIG. 5 and FIG.
This will be described with reference to the flowchart shown in the figure. In addition,
In the following description, S indicates a step.

First, after the current engine speed N is read in S1, it is determined in S2 whether the engine speed N is N ₁ or less. When it is determined that N ≦ N ₁ , the process proceeds to S3, the wastegate valve 16 is fully closed, and the load control by the throttle valve 13 is performed in this state (the throttle valve 13 at the time of low rotation). Load control).

If it is determined in S2 that N ≦ N ₁ is not established, then the flow shifts to S4, where it is determined whether N ≧ N ₂ or not. And N
When it is determined that ≧ N ₂ , the current intake pressure P is read in S5, and then it is determined in S6 whether P> Po. When it is determined that P> Po is not established in this determination in S6, the waste gate valve 16 is fully opened in S7, and the load control by the throttle valve 13 is performed (load control by the throttle valve 13 at high rotation and low load). .

When it is determined that P> Po in S6, it means that the load control is performed by the wastegate valve 16. In this case, first, the current accelerator opening degree θA is read in S8. Next, at S9, a wastegate valve capable of obtaining an intake pressure P (intake air amount) corresponding to the accelerator opening θA from a map created in advance using the current engine speed N and the accelerator opening θA as parameters. The opening θWB of 13 is read. Then, finally in S10, the opening of the waste gate valve 16 is controlled so as to reach the opening θWB set in S9.

On the other hand, when it is determined in S4 that N ≧ N ₂ is not satisfied,
It is a switching region where N ₁ <N <N ₂ , and at this time, the above S
By the processing of S11, S12, S13 corresponding to 8, S9, S10,
The wastegate valve 16 is controlled to have a predetermined opening θWB. Note that θWB output in S13, that is, θWB set in S12 is, as is apparent from FIG. Is smaller, the opening of the waste gate valve 16 is smaller. That is, in this switching region, the opening of the wastegate valve 16 is gradually changed from fully closed to fully opened in accordance with the increase of the engine speed N in preparation for when the engine speed N becomes N _2. In other words, the load control by the throttle valve 13 is performed while adding the load control by the waste gate valve 16.

FIG. 7 is a flow chart showing a control example in consideration of the problem of turbo lag changing according to the gear shift position (gear stage) of the transmission. The sensor for gear shift position detection is shown in FIG. It is shown at 23. That is, the acceleration / deceleration in which the turbo lag is a problem is when the shift position is the low speed position (for example, the first forward speed, the second speed, and the third speed in the fifth forward speed), while the shift position is the high speed position (fourth forward speed is four). Speed, 5
When the speed is high), acceleration / deceleration, especially large acceleration / deceleration is not performed (not required).

Given the above, first, S21 current shift position K is read in in, in S2 after this, whether the lower speed side than the current shift position K, for example, 4-speed (K ₄₎ is determined. Then, K <K ₄ is not satisfied, that is, the shift position is 4
When it is determined that the vehicle is in the 5th or 5th speed position,
The processing after S23 is performed. The processing from S23 to S28 corresponds to the processing from S5 to S10 in FIG. That is, the route S23, S24, S25 is when load control is performed by the throttle valve 13 while the wastegate valve 16 shown in FIG. 2 is fully opened, and also S23, S24, S26, S27, S28.
Is when the wastegate valve 16 performs load control.

On the other hand, if it is determined in S22 that K <K ₄ , the process proceeds to S29, and control is performed so that the intake pressure P does not exceed the maximum supercharging pressure P ₁ . That is, after the current intake pressure P is read in S29, this intake pressure P is read in S30.
Is greater than the maximum supercharging pressure P ₁ , and when P> P ₁ , the wastegate valve 16 is operated in the opening direction by a slight angle in S31 to reduce the intake pressure P, and conversely P> If not P ₁ , wastegate valve 1 at S 32
6 is operated in the closing direction by a small angle.

Although the embodiment has been described above, at the time of acceleration, the throttle valve 13 may be temporarily fully opened and the waste gate valve 16 may be fully closed to speed up the rotation of the supercharger 12. At the time of deceleration, the throttle valve 13 and the waste gate valve 16 may be fully closed to increase pumping loss and enhance the braking action. Further, when the engine is cold, the wastegate valve 16 may be fully closed in all the operating areas as in the conventional case to shorten the warm-up time. Of course, when the control unit 18 is configured by a computer, it may be either a digital type or an analog type.

(Effects of the Invention) As described above, the present invention can improve the fuel consumption by controlling the load of the engine and reducing the throttle loss of the throttle valve in a wide range from low load to high load. .

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention. FIG. 2 is a graph showing a control area according to the present invention. FIG. 3 is a graph showing the effect of the present invention while comparing it with the conventional one. FIG. 4 is a graph showing an example when the control area according to the present invention is limited. FIG. 5 is a graph showing an example of control in the switching region in FIG. FIG. 6 and FIG. 7 are flow charts showing a control example of the present invention. 1: Engine body 5: Intake passage 12: Supercharger 12a: Compressor 12b: Turbine 12c: Shaft 13: Throttle valve 14: Exhaust passage 15: Bypass passage 16: Wastegate valve 17: Actuator 18: Control unit 19: Sensor ( Engine speed) 20: Sensor (accelerator opening) 21: Sensor (intake pressure)

Claims (3)

[Claims] 1. An exhaust turbocharger for supercharging using exhaust energy, a bypass passage for diverting exhaust gas to the supercharger, and a supercharge provided in the bypass passage. In a supercharged engine equipped with a waste gate valve that opens and closes according to pressure, and a throttle valve that opens in response to an accelerator, a load detection unit that detects an engine load, and an engine load detected by the load detection unit. Is less than a predetermined load, wastegate valve opening correction means for opening the wastegate valve regardless of supercharging pressure, and the engine load detected by the load detection means is more than the predetermined load, accelerator, Regardless of the position, the throttle valve opening correction means for forcibly opening the throttle valve, and the engine negative detected by the load detection means. A supercharger engine, wherein the wastegate valve controls the engine load when the load is equal to or more than the predetermined load. 2. The load according to claim 1, wherein the predetermined load is a load when the downstream pressure of the throttle valve becomes equal to the upstream pressure of the throttle valve when the waste gate valve is open. There is an engine with a supercharger. 3. The engine with a supercharger according to claim 1, wherein the forced opening operation of the throttle valve is a full opening operation.