JP3378052B2 - Control device for engine with mechanical supercharger - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an engine with a mechanical supercharger, in which an intake valve is set to be late-closed so that an effective compression ratio becomes smaller than an effective expansion ratio at least in a low load operation range of the engine. The present invention relates to a control device for an engine with a mechanical supercharger.

[0002]

2. Description of the Related Art Conventionally, a mechanical supercharger driven by a driving force of an output shaft of an engine is provided in an intake passage, and a bypass passage bypassing the upstream and downstream sides of the mechanical supercharger is provided. A bypass passage that is opened by a bypass valve in a low-load operating range of an engine and closed in a high-load operating range is known, for example, from Japanese Patent Application Laid-Open No. 2-283816.

[0003]

On the other hand, in such an engine with a mechanical supercharger, the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine, that is, (effective compression ratio / effective It is known that the intake valve is set so as to be delayed so that the expansion ratio) <1 and the intake valve is closed when the intake valve rises from the bottom dead center. In such an engine with a mechanical supercharger, the air-fuel mixture sucked into the cylinder is blown back to the intake passage side outside the cylinder due to the late closing of the intake valve, and the pressure in the intake passage increases accordingly. Therefore, the differential pressure (intake pressure) between the upstream and downstream sides of the throttle valve is reduced, and the intake air amount is reduced accordingly. Further, when the vehicle travels at a high altitude of, for example, 2000 m or more, the density of air becomes small, so that the amount of intake air decreases accordingly. Therefore, when a vehicle having an engine with a mechanical supercharger that performs late closing as described above travels at high altitudes, the intake air amount becomes smaller than in a normal traveling state, and therefore, in a low load operating range, particularly At the time of idling, the amount of air required to secure the idling speed of the engine cannot be taken in, and as a result, the engine rotation becomes unstable.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art, and lowers the intake valve so that the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine. A control device for an engine with a mechanical supercharger that enables stable engine rotation in a low load operating range in an engine with a mechanical supercharger that is set to close the intake valve slowly when rising from a point It is intended to be provided. Another object of the present invention is to provide a control device for an engine with a mechanical supercharger that prevents damage to the mechanical supercharger in a low load operation range.

[0005]

In order to achieve the above object, the present invention sets the intake valve to be late-closed so that the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine. In a control device for an engine with a mechanical supercharger in which a mechanical supercharger is provided in an intake passage downstream of a throttle valve, a bypass passage that connects the upstream and downstream sides of the mechanical supercharger and this bypass passage An air bypass valve that operates to open in a low load operation range and close in a high load operation range, a differential pressure detection unit that detects the differential pressure between the upstream and downstream sides of the throttle valve, and an idle time and a differential pressure detection unit that detects the differential pressure. When the differential pressure is smaller than a predetermined value, the air bypass valve is forcibly closed even in a low load operation range. According to the present invention having such a configuration, the intake valve is set to be late-closed so that the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine, and the mechanical supercharger is provided downstream of the throttle valve. It is applied to the engine with a mechanical supercharger installed in the intake passage, and normally the bypass passage that connects the upstream and downstream sides of the mechanical supercharger is opened by the air bypass valve in the low load operating range of the engine and the high load operating range. It is working to close with. On the other hand, when the vehicle is traveling in a high altitude where the air density is low, the pressure difference between the upstream and downstream sides of the throttle valve may become smaller than a predetermined value at the time of idling. The air bypass valve is forcibly closed even in the low load operation range. As a result, the mechanical supercharger supercharges the intake pressure, so that stable engine rotation is possible even during idling, which is a low load operation range.

Further, in the present invention, the control means preferably closes the air bypass valve so that it is fully closed. Further, in the present invention, it is preferable that the mechanical supercharger is directly connected to the engine and is constantly driven. Further, in the present invention, it is preferable that the control means closes the air bypass valve only when the vehicle speed is equal to or lower than a predetermined value. In this case, since the control means does not close the air bypass valve in this way, the mechanical supercharger is not damaged by heating. Further, in the present invention, it is preferable that the control means partially close the air bypass valve so that the differential pressure detected by the differential pressure detecting means becomes equal to or higher than a predetermined value.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram showing a control device for an engine with a mechanical supercharger of the present invention. In the engine 1 to which the present invention is applied, the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine.
That is, it is a type in which the intake valve is set to be closed (late closing) when the intake valve is raised from the bottom dead center so that (effective compression ratio / effective expansion ratio) <1. As shown in FIG. 1, an intake passage 2 that supplies intake air to a cylinder 1a of an engine 1 is provided with an air cleaner 3, an intake air amount sensor 4, and a throttle valve 5 from the upstream side, and a downstream side of the throttle valve 5 is provided. A mechanical supercharger 6 is provided. This mechanical supercharger 6 has two screw-shaped rotors 6a.
Rotate in opposite directions when the convex portions and the concave portions are engaged with each other and rotate in the opposite direction. The space between the concave portion of the rotor 6a and the inner wall of the casing moves axially while the volume of the space gradually decreases, and An internal compression type supercharger of the screw type (Rishorum type) that compresses and pumps internally is used.

Further, an intercooler 8 and a surge tank 7 are provided in the intake passage 2 on the downstream side of the mechanical supercharger 6. Further, an independent intake passage 2a connected to each cylinder 1a is formed on the downstream side of the surge tank 7, and an injector 9 for injecting and supplying fuel to the independent intake passage 2a is arranged. A bypass passage 11 that bypasses the mechanical supercharger 6 is connected to the intake passage 2. One end of this bypass passage 11 is connected to the upstream side of the supercharger 6 and downstream of the throttle valve 5, and the other end is connected to the upstream side of the intercooler 8. The bypass passage 11 is provided with an air bypass valve 12 for adjusting the flow passage area of the bypass passage 11. The air bypass valve 12 is provided with a duty controllable solenoid valve 14. That is, as will be described later, the bypass passage 11 is basically configured to open the air bypass valve 12 in the low load operation range and close the air bypass valve 12 in the high load operation range by the solenoid valve 14. Control is made. This mechanical supercharger 6 is indicated by reference numeral 16 for convenience.
, It is directly connected to the pulley 20 of the engine output shaft 18, and is always driven and rotated with the rotation of the engine.

A throttle bypass passage 22 is provided which bypasses the throttle valve 5 and communicates with the intake passage 2 on the upstream and downstream sides thereof, and further, the intake air amount is adjusted in the throttle bypass passage 22. A throttle bypass valve 24 is provided. The throttle bypass valve 24 controls the engine speed during idling. On the other hand, in the bypass passage 11 between the throttle valve 5 and the air bypass valve 12, a pressure sensor 2 for detecting the intake pressure on the downstream side of the throttle valve 5 is provided.
6 is provided, and an atmospheric pressure sensor 28 for detecting atmospheric pressure is provided in the intake passage 2 upstream of the throttle valve 5. Further, a rotation sensor 30 for detecting the engine speed, a vehicle speed sensor 32 for detecting the vehicle speed, a water temperature sensor 34 for detecting the temperature of the engine cooling water, a throttle sensor 36 for detecting the opening of the throttle valve 5, and the like are provided. . 40 is a control unit, and this control unit 40 is
Various information is input. That is, the intake amount signal from the intake amount sensor 4, the throttle opening signal from the throttle sensor 36, the throttle downstream pressure signal from the pressure sensor 26,
An atmospheric pressure signal is input from the atmospheric pressure sensor 28, an engine rotation signal is input from the rotation sensor 30, a vehicle speed signal is input from the vehicle speed sensor 32, a water temperature signal is input from the water temperature sensor 34, and the like.

The control unit 40 outputs a control signal to the throttle valve 5, the air bypass valve 12 and the throttle bypass valve 24 based on these input signals, and adjusts the opening degree of these valves. Next, the control content of the control unit 40 will be described with reference to FIGS. 2 and 3. FIG. 2 is a flowchart showing the contents of control by the control unit 40, and FIG. 3 is a map showing the contents of normal control of the air bypass valve. In FIG. 2, S indicates each step. First, in S1, the required conditions are read. Specifically, an intake air amount signal, a throttle opening signal (θ), a throttle downstream pressure signal (P ₂ ), an atmospheric pressure signal (P ₁ ), an engine rotation signal (r), a vehicle speed signal (V), a water temperature signal, etc. Is read. Next, in S2, it is determined whether or not the atmospheric pressure (P ₁ ) is less than a predetermined value (P ₀ ), that is, the vehicle is, for example, 2000 m.
It is determined whether or not the vehicle is traveling above the high altitude. In the normal case where the vehicle is not traveling at high altitude, the routine proceeds to S3, where the air bypass valve 12 uses the map of FIG. 3 and normally controls with the throttle opening (θ) and the engine speed (r) as parameters. Is done. That is, the air bypass valve 12 is controlled in the closing direction as the throttle opening (θ) is larger, that is, the operating load is larger, and is controlled in the opening direction when the throttle opening (θ) is smaller, that is, the operating load is smaller. To be done. Further, in this normal control, the air bypass valve 12 is controlled to be fully closed and the throttle bypass valve 24 is opened to ensure a predetermined engine speed at the time of idling which is a low load operation range. Adjust the intake air volume.

Next, in S4, the engine speed (r)
Is determined to be less than the predetermined value (r ₀ ), and in S5,
It is determined whether the throttle opening (θ) is less than a predetermined value (θ ₀ ). That is, by these steps S4 and S5,
Determine if the engine is idle. If the vehicle is not running at high altitude and is not idle, the routine proceeds to S3, where the air bypass valve 12 is normally controlled based on the map of FIG. When it is determined that the vehicle is traveling at high altitude and is in the idle state, the process proceeds to S6, where the vehicle speed (V) is a predetermined value (V ₀ ).
Determine if less than. This state means a driving state in which the driver is releasing the accelerator pedal and traveling downhill. If the vehicle speed (V) is equal to or higher than the predetermined value (V ₀ ), the routine proceeds to S3, where the air bypass valve 12 is normally controlled based on the map of FIG. Next, the process proceeds to S7, the differential pressure between the atmospheric pressure (P ₁₎ and the throttle downstream pressure signal _{(P 2) (P 1 -P} 2), i.e., the intake pressure is determined whether less than a predetermined value ([Delta] P) . The predetermined value (ΔP) is an intake pressure for ensuring the required engine idle speed when the throttle bypass valve 24 is fully opened. If this differential pressure (P ₁ -P ₂ ) is a sufficient value that is equal to or greater than a predetermined value,
Since the amount of intake air required to maintain the required idle speed is secured, the routine proceeds to S3, where the air bypass valve 12 is normally controlled based on the map of FIG.

If the vehicle speed is lower than a predetermined value and the intake pressure (P ₁ -P ₂ ) is lower than the predetermined value while the vehicle is traveling at high altitude and is in an idle state, the process proceeds to step S8.
2 is forcibly closed. This closing operation may be a closing operation in which the air bypass valve 12 is fully closed, or a partial closing operation by a predetermined value so that the intake pressure (ΔP) required to secure the idle speed is obtained. May be Here, at least in the low load operating range of the engine, the intake air is taken in at a place where the intake valve is raised from the bottom dead center so that the effective compression ratio becomes smaller than the effective expansion ratio, that is, (effective compression ratio / effective expansion ratio) <1. When a vehicle with an engine of the type set to close the valve (late closing) runs at high altitude,
Since the density of air is low, it may be difficult to obtain the intake pressure required to secure the idle speed. In the embodiment of the present invention, since the air bypass valve 12 is forcibly closed in such a case, the suction of the intake passage 2 is performed by the mechanical supercharger 6 rotating with the rotation of the engine 1. The atmospheric pressure is supercharged, which makes it possible to secure the intake air amount necessary to maintain the idle speed. Further, in the embodiment of the present invention, the vehicle speed (V) is set to the predetermined value (V ₀ ) under such a low load operation state.
In the above case, the forced closing operation of the air bypass valve 12 indicated by S8 is not performed. When the air bypass valve 12 is forcibly closed when the vehicle speed (V) is equal to or higher than the predetermined value (V ₀ ), the mechanical supercharger 6 is rotated by itself even in the low load operation range. In some cases, the air bypass valve 12 is returned to the normal control in such a case, so that such a problem does not occur and the mechanical type The damage of the supercharger 6 can be prevented.

The above embodiment has been described with respect to the case where the engine is in the idling state, but the present invention is not limited to this, and can be applied even during the partial load which is a low load operating range.

[0014]

As described above, according to the present invention, the intake valve is installed at a position elevated from the bottom dead center so that the effective compression ratio becomes smaller than the effective expansion ratio at least in the low load operation range of the engine. It is possible to enable stable engine rotation in a low load operation range in an engine with a mechanical supercharger that is set to be closed late.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a control device for an engine with a mechanical supercharger according to the present invention.

FIG. 2 is a flowchart showing control contents according to an embodiment of the present invention.

FIG. 3 is a map showing the contents of normal control of an air bypass valve according to an embodiment of the present invention.

[Explanation of symbols]

1 engine 2 Intake passage 5 Throttle valve 6 Mechanical supercharger 11 Bypass passage 12 Air bypass valve 14 Solenoid valve 18 engine output shaft 22 Throttle bypass passage 24 Throttle bypass valve 26 Pressure sensor 28 atmospheric pressure sensor 30 speed sensor 32 vehicle speed sensor 36 Throttle sensor 40 control unit

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Claims (5)

(57) [Claims] 1. An intake valve is set to be late-closed so that an effective compression ratio becomes smaller than an effective expansion ratio at least in a low load operation range of an engine, and a mechanical supercharger is provided in an intake passage downstream of a throttle valve. In a control device for an engine with a mechanical supercharger, a bypass passage that connects the upstream and downstream sides of the mechanical supercharger and this bypass passage are operated to open in the low load operating range of the engine and close in the high load operating range. The air bypass valve, the differential pressure detecting means for detecting the differential pressure between the upstream and downstream sides of the throttle valve , and the low pressure operating range even when the engine is idle and the differential pressure detected by the differential pressure detecting means is smaller than a predetermined value. A control device for forcibly closing the air bypass valve, and a control device for an engine with a mechanical supercharger, comprising: Wherein said control means is a control device of the mechanical supercharger with the engine according to claim 1, wherein Ru is closing so that the fully closed the air bypass valve. 3. The control device for an engine with a mechanical supercharger according to claim 1, wherein the mechanical supercharger is directly connected to the engine and is constantly driven. 4. The control means closes the air bypass valve only when the vehicle speed is equal to or lower than a predetermined value.
1. A control device for an engine with a mechanical supercharger according to 1 . 5. The control means is based on the differential pressure detection means.
If the differential pressure detected by the
2. The partial bypass operation of the bypass valve.
Control device for engine with mechanical supercharger.