JPH0415955Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a supercharging control device for an internal combustion engine that performs two-stage supercharging using two superchargers: a turbocharger and a supercharger.

[Conventional technology]

Conventionally, an internal combustion engine in which a turbocharger and a supercharger are arranged in series is already known (for example, Japanese Patent Publication No. 41-8081). This is a combination of a supercharger that can highly supercharge the intake air in the low-speed range and a turbocharger that can highly supercharge the intake air in the high-speed range. In addition to preventing deterioration in responsiveness when charging, the aim is to obtain high supercharging from low speed ranges to high speed ranges. In the case of a turbocharger, the supercharging pressure is controlled by opening a wastegate valve, and in the case of a supercharger, it is controlled by opening a bypass passage connecting the front and rear parts.

[Problem that the invention attempts to solve]

When the internal combustion engine is running at a high speed, it is also possible to suspend the supercharge and supercharge the intake air only by using the turbocharger, which has little drive loss and does not cause deterioration in the fuel efficiency of the internal combustion engine. However, in this case, stopping the supercharger lowers the supercharging pressure in a stepwise manner, resulting in a problem of lowering the engine output.

[Means for Solving the Problems] In order to solve the above problems, the supercharging control device according to the present invention is a supercharging control device for an internal combustion engine in which a turbocharger and a supercharger are provided in series in the intake passage. A waste gate valve is disposed in the exhaust passage connected to the upstream side of the turbine of the turbocharger for causing the exhaust gas in the exhaust passage to flow around the turbine. A first valve that further corrects and controls the opening amount of the waste gate valve, which increases or decreases depending on the level of pressure on the downstream side.
In addition, a second control means capable of stopping the drive of the supercharger is provided, and when the internal combustion engine is at high rotation speed, the second control means is provided.
The control means operates to stop the supercharger, and the first control means operates to reduce the opening amount of the waste gate valve.

[Effect]

In the low rotational speed range of an internal combustion engine, the turbocharger and supercharger connected in series perform a supercharging action by compressing the intake air in two stages, so even when the discharge pressure of the turbocharger is not high, the supercharger The necessary boost pressure is obtained by operating the gear. The boost pressure of the turbocharger is
The opening amount of the waste gate valve that bypasses the turbocharger turbine is controlled to increase or decrease in accordance with the boost pressure, but when the internal combustion engine is in a high rotation speed range above a predetermined rotation speed, , second
The supercharger is stopped by the operation of the control means, and the supercharger is switched to one-stage supercharging using only the turbocharger to avoid waste of output. In the present invention, at the time of this switching, the first control means that further corrects and controls the opening amount of the wastegate valve is activated to reduce the opening amount of the wastegate valve, so that the supercharging pressure of the turbocharger is reduced. The boost pressure increases rapidly to compensate for the drop in boost pressure caused by switching, increasing the engine's output and facilitating the switching.

〔Example〕

The present invention will be explained below with reference to the illustrated embodiments.

The figure shows an internal combustion engine to which an embodiment of the present invention is applied. In the figure, a piston 12 is slidably supported in a cylinder bore 11 formed in an engine body 10, and a combustion chamber 13 is formed above the piston 12. The combustion chamber 13 has an intake passage 14
The exhaust passage 15 communicates with the exhaust passage 15.

The air cleaner 16 is provided at the most upstream side of the intake passage 14, and the air flow meter 17 is provided at the downstream side thereof. Further downstream, a compressor 19 of the turbocharger 18 is provided, and a supercharger 2 is provided downstream of this compressor 19.
0 is set. The throttle valve 21 is provided between the compressor 19 and the supercharger 20, and changes the flow area in the intake passage 14 in conjunction with an accelerator pedal (not shown). Intake passage 14
A surge tank 23 is formed downstream of the supercharger 20 .

On the other hand, a turbine 25 of the turbocharger 18 is provided in the middle of the exhaust passage 15, and a bypass passage 26 that bypasses the turbine 25 is formed. In the turbocharger 18 , a turbine 25 is rotationally driven by exhaust gas passing through the exhaust passage 15 , which rotates a compressor 19 to increase the pressure of air taken in from the intake passage 14 . The wastegate valve 27 opens and closes the bypass passage 26 to adjust the amount of exhaust gas supplied to the turbine 25 and the turbocharger 18.
control the rotation of The actuator 28 that opens and closes the waste gate valve 27 has a conventionally known configuration, and the diaphragm 3 is connected to the inside of the shell 29.
0 to form a pressure chamber 31, into which the pressure immediately downstream of the compressor 19 in the intake passage 14 is transmitted via a passage 32. When the pressure within the pressure chamber 31 overcomes the elastic force of the spring 33, the waste gate valve 27 opens the bypass passage 26, controls the exhaust gas passing through the turbine 25, and controls the exhaust gas passing through the turbine 25 to exit the compressor 19 of the turbocharger 18. Keep the pressure constant.

A passage 51 that branches off from the middle of the passage 32 is
It is connected to the upstream portion of the compressor 19 in the intake passage 14 . The switching valve 52 provided in the middle of the passage 51 constitutes a main part of the first control means for correcting the opening degree of the waste gate valve 27, and is switched and controlled by the electronic control section 50. to open and close the passage 51. The switching valve 52 is the passage 5
1 is released, the pressure chamber 3 of the actuator 28
1 communicates with the upstream intake passage 14 of the compressor 19 as well as the passage 32, and the switching valve 52 communicates with the passage 5.
1 is closed, the pressure chamber 31 communicates only with the passage 32. Switching valve 52 of passage 51 Pressure chamber 31
A throttle 53 is provided on the side in order to control the flow rate of air bled to the intake passage 14 side through the passage 51 when the switching valve 52 is opened. Aperture 53
The magnitude of is the intake pressure in the surge tank 23 when supercharging is performed by both the turbocharger 18 and the supercharger 20 at high rotation and high load, and the intake air pressure on the outlet side of the compressor 19 when the supercharger 20 is stopped. The pressure is determined to be approximately equal to the pressure.

The air supercharged by the turbocharger 18 is regulated by the throttle valve 21 and flows into the supercharger 20. The drive shaft of the supercharger 20 is connected to a pulley 35 having an electromagnetic clutch (not shown) constituting a main part of the second control means, and this pulley 35 is connected to the engine body 10.
It is connected by an endless belt 37 to a crank pulley 36 provided therein. The supercharger 20 is therefore driven via the crank pulley 36 when the electromagnetic clutch is in the engaged state. The upstream and downstream sides of the supercharger 20 in the intake passage 14 are connected by a bypass passage 38, and a bypass valve 39 is provided in the middle of the bypass passage 38 to open and close it. Bypass valve 39
The actuator 40 that opens and closes is configured by partitioning the inside of a shell 41 with a diaphragm 42 to form a pressure chamber 43.
is connected to a bypass valve 39. Pressure chamber 43
The pressure inside the surge tank 23 is transmitted through a passage 45 to the pressure chamber 43, and when this pressure overcomes the elastic force of a spring 44 provided in a chamber on the opposite side of the pressure chamber 43, a bypass valve is activated. 39 opens the inside of the bypass passage 38.

The electromagnetic clutch of the supercharger 20 is switched and controlled by an electronic control section 50 equipped with a microcomputer. During high-load operation when the throttle valve 21 is opened, the electronic control unit 50 calculates the engine load Q/N from the intake air amount Q input from the air flow meter 17 and the engine rotation speed N input from the rotation speed sensor 54. , when this Q/N value exceeds a certain value, an ON command is output to the pulley 35 to connect the electromagnetic clutch. The rotors 20a, 20b of the supercharger 20 are rotated by the rotation of the crank pulley 36, and start supercharging. Further, when the flow rate of exhaust gas increases due to high-load operation of the internal combustion engine, the turbocharger 18 also starts supercharging, thereby performing two-stage supercharging by the turbocharger 18 and the supercharger 20.

Now, the actuator 40 is the surge tank 23
Since the bypass valve 39 operates in response to the pressure inside the surge tank 23, the bypass valve 39 opens according to the pressure inside the surge tank 23, thereby controlling the supercharging pressure of the supercharger 20. On the other hand, when the engine speed is below the predetermined value No. (see Fig. 2), the actuator 28 receives the pressure on the outlet side of the compressor 19 as it is because the switching valve 52 is closed. Accordingly, the waste gate valve 27 is opened and closed to control the supercharging pressure of the turbocharger 18. However, when the engine speed exceeds the predetermined value No, correction control is performed by operating the first control means. That is, the electronic control section 5
0, the switching valve 52 is opened, and as a result, the air flowing through the passage 32 is bled to the upstream side of the compressor 18 through the passage 51, so the pressure inside the pressure chamber 31 decreases, and the waste gate valve 27 is opened.
becomes difficult to open, the rotational speed of the turbine 25 increases, and the supercharging pressure of the turbocharger 18 suddenly increases.

This will be explained with reference to FIG. 2. In this figure, the symbol T indicates the supercharging pressure by the turbocharger 18, and the symbol S indicates the supercharging pressure by the supercharger 20. When the supercharger 20 is driven and the engine speed is lower than a predetermined value No, two-stage supercharging is performed by the turbocharger 18 and the supercharger 20. in this case,
In the turbocharger 18, when the pressure on the outlet side of the compressor 19 exceeds a certain value, the waste gate valve 27 opens to limit the supercharging pressure.
When the internal pressure exceeds a certain value, the bypass valve 3
9 is opened and its supercharging pressure is limited. However, when the engine speed exceeds a predetermined value No, the supercharger 20 is stopped and the first The control means opens the switching valve 52 and bleeds the air in the passage 32. Therefore, only part of the pressure on the outlet side of the compressor 19 is transmitted to the pressure chamber 31 of the actuator 28, and the force acting to open the wastegate valve 27 is weakened. As a result, the supercharging pressure (based only on the turbocharger 18) when the waste gate valve 27 is opened increases, and a supercharging pressure that is approximately equal to the total supercharging pressure when the supercharger 20 is also operating is obtained. . In other words, the turbocharger 18 is reduced by an amount approximately equal to the decrease in supercharging pressure due to the suspension of the supercharger 20.
The boost pressure increases. In addition, in the figure, broken line B
indicates the supercharging pressure when the passage 51 and the switching valve 52 are not provided.

As described above, according to this embodiment, when switching from two-stage supercharging in which both the turbocharger and supercharger operate to single-stage supercharging in which only the turbocharger operates, the supercharging pressure suddenly drops and the engine There is no longer a temporary drop in output, and the output performance of the engine can be made safer. In addition, when the internal combustion engine operates in a high rotation range and the supercharger 20 is at rest, the bypass valve 39 operates to reduce the pressure in the surge tank 23 (turbocharger 1
8), most of the air does not pass through the supercharger 20 but flows through the bypass passage 38. Therefore, the resistance that the intake air receives from the supercharger 20 is small, and the engine output can be improved as much as possible.

[Effect of idea]

As described above, according to the present invention, when the internal combustion engine is operated at high speed and the supercharger is stopped, the supercharging pressure is prevented from decreasing and the engine output is prevented from decreasing, and the turbocharger and the engine output are prevented from decreasing. The effect of smoothly switching from two-stage supercharging in series to one-stage supercharging using only turbocharger can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a graph showing changes in supercharging pressure with respect to engine speed. 14...Intake passage, 15...Exhaust passage, 18...
...Turbocharger, 20...Supercharger, 25...Turbine, 27...Wastegate valve, 51...Passage, 52...Switching valve.

Claims (1)

[Claims for Utility Model Registration] 1. A supercharging control device for an internal combustion engine in which a turbocharger and a supercharger are provided in series in an intake passage, the exhaust passage being connected to the upstream side of a turbine of the turbocharger, A waste gate valve is provided to cause the exhaust gas in the exhaust passage to flow around the turbine, and the opening of the waste gate valve increases or decreases depending on the level of pressure downstream of the compressor of the turbocharger. A first control means for further correcting and controlling the amount is provided, and a second control means is provided for stopping the drive of the supercharger, and when the internal combustion engine is at high rotation speed, the second control means A supercharging control device for an internal combustion engine, characterized in that the first control means operates to reduce the opening amount of the waste gate valve while stopping the supercharge. 2. The above-mentioned first control means operates to increase the supercharging pressure caused by the turbocharger by an amount substantially equal to the decrease in supercharging pressure due to the suspension of the supercharger. A supercharging control device according to scope 1.