JP2001221076A - Controller of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent delay in the rising of supercharging pressure in acceleration of peddaling an accelerator in a breath form a low load condition. SOLUTION: A supercharger 51 pressurizes air taken into an engine at an upstream side of a throttle valve 50. A by-pas valve 53 capable of adjusting the flow rate of air flowing in a by-pass path 52 is mounted in the by-pass path 52 for by-passing the supercharger 51. Whether in a supercharging zone or in a non-supercharging zone is determined by a determining means 55, and a control means 56 controls the by-pass valve 53 to allow the upstream pressure of the throttle valve 50 to corresponds to the atmospheric pressure in the non- supercharging zone, and the upstream pressure of the throttle valve 50 to agree with a target supercharging pressure above the atmospheric pressure in the supercharging zone.

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, and more particularly to a control device having a supercharger.

[0002]

2. Description of the Related Art A passage for bypassing a turbine of a turbocharger and a bypass valve capable of controlling the passage area are provided. In a supercharging region, the bypass valve is controlled so that a target supercharging pressure is obtained. There is one in which the charging pressure is adjusted, and the supercharging work is reduced by controlling the bypass valve so that the charging pressure becomes substantially equal to the atmospheric pressure when the pressure is in the non-supercharging region (Japanese Patent Laid-Open No. 7-1995). No. 150990).

[0003]

When the accelerator pedal is depressed at once from a low load state, it is necessary to increase the supercharging pressure quickly.

However, in the conventional apparatus, since the rotation speed of the turbine (compressor) is reduced in the non-supercharged region, when the operating region is shifted from the non-supercharged region to the supercharged region by the above-described acceleration operation, the turbine ( Until the rotation speed of the compressor increases to the rotation speed at which the target boost pressure can be obtained, the increase of the boost pressure is delayed.

Therefore, according to the present invention, a bypass valve is provided in a passage which bypasses a supercharger which pressurizes air taken into an engine upstream of a throttle valve, and a bypass valve capable of adjusting an air flow rate flowing through the bypass passage is provided. By controlling the bypass valve so that the upstream pressure of the throttle valve becomes equivalent to the atmospheric pressure in the pressure range and the upstream pressure of the throttle valve 50 becomes the target boost pressure equal to or higher than the atmospheric pressure in the supercharging region, the low load is reduced. It is an object of the present invention to prevent a delay in boosting the boost pressure during acceleration in which the accelerator pedal is depressed at once from a state.

[0006]

According to a first aspect of the present invention, as shown in FIG. 27, a supercharger 51 for pressurizing air taken into an engine upstream of a throttle valve 50, and a bypass for the supercharger 51 are provided. Passage 52, a bypass valve 53 capable of adjusting the flow rate of air flowing through the bypass passage 52, means 55 for determining whether the region is a supercharged region or a non-supercharged region, and a non-supercharged region So that the upstream pressure of the throttle valve 50 becomes equivalent to the atmospheric pressure.
Means 56 for controlling the bypass valve 53 so that the upstream pressure of the air-fuel ratio becomes a target supercharging pressure equal to or higher than the atmospheric pressure.

According to a second aspect, in the first aspect, the supercharger is a turbocharger or a mechanically driven mechanical supercharger.

According to a third aspect of the present invention, in the first or second aspect, the bypass valve control means 56 sets a target supercharging pressure in accordance with operating conditions, and a bypass valve in accordance with the target supercharging pressure. It comprises means for calculating the control amount, and means for controlling the bypass valve 53 so as to achieve the bypass valve control amount.

According to a fourth aspect of the present invention, in the third aspect, there is provided means for detecting the upstream pressure of the throttle valve as an actual supercharging pressure. To correct the boost pressure.

According to a fifth aspect of the present invention, in the third aspect, there is provided means for detecting an upstream pressure of the throttle valve as an actual supercharging pressure. To correct the boost pressure.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the supercharger is a mechanical supercharger capable of being driven and stopped. Stop the turbocharger.

According to a seventh aspect of the present invention, in the sixth aspect, a region (a supercharging transition region) for driving a mechanical supercharger is provided adjacent to the supercharging region in the non-supercharging region.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the throttle valve can be electrically driven.

[0014]

According to the first, second and third aspects of the present invention, a bypass valve is provided in a passage which bypasses the supercharger upstream of the throttle valve, and the bypass pressure is controlled by the bypass valve. It is possible to minimize the decrease in the turbocharger rotation speed in the charging region, and this allows the turbocharger rotation speed to rise due to a delay in switching from the non-supercharging region to the supercharging region, such as during acceleration. The boost pressure response delay can be eliminated. For example, when the turbocharger is a turbocharger having a structure in which a turbine is rotated by the flow rate and pressure of exhaust gas, it is better to bypass the intake side and maintain the upstream pressure of the throttle valve at atmospheric pressure, as in the conventional example. According to the first, second and third aspects of the present invention, the turbocharger rotation speed in the non-supercharging region becomes higher than when the throttle valve upstream pressure is maintained at atmospheric pressure or equivalent by bypassing the engine side. At the time of switching from the supply region to the supercharge region, the rise of the supercharging pressure is accelerated by the higher turbocharger rotation speed at the initial stage of the switching, and a good supercharging pressure response, that is, a torque response can be secured.

A fourth aspect of the present invention considers a delay in the rise of the turbocharger rotation speed during acceleration switching from a non-supercharged region to a supercharged region and a response delay in supercharging pressure due to filling of a volume upstream of a throttle valve. In addition, according to the fifth aspect, a quicker boost pressure response can be obtained during acceleration when switching from the non-supercharging region to the supercharging region.

According to a fifth aspect of the present invention, a delay in the fall of the turbocharger rotation speed and a delay in the supercharging pressure response due to the presence of a volume upstream of the throttle valve during deceleration when switching from the supercharging region to the non-supercharging region are considered. According to the sixth aspect of the invention, a quicker boost pressure response can be obtained at the time of deceleration when switching from the supercharging region to the non-supercharging region.

According to the sixth aspect of the present invention, the supercharging work can be stopped.

According to the seventh aspect of the present invention, the supercharger rotates in a region adjacent to the supercharged region in the non-supercharged region. The boost pressure response delay due to the delay in the rise of the rotation speed can be eliminated.

According to the eighth aspect, the throttle valve can be freely operated with respect to the accelerator pedal, so that, for example, the accelerator operation amount is about 50% and the throttle valve operation amount is the maximum 100%. Can be set, thereby increasing the non-supercharging area and reducing the loss due to the throttle throttle at the time of supercharging, so that an efficient engine can be realized.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an engine body. A throttle valve 4 mechanically interlocked with an accelerator pedal 3 is interposed in the intake passage 2 of the engine. The amount of air taken into the engine is adjusted by the opening degree of the throttle valve 4 determined at this time. The shaft torque is controlled.

A control unit 11 mainly composed of a microcomputer includes an engine rotation speed from a crank angle sensor 13, an intake air amount from an air flow meter 14 upstream of the throttle valve 4, a cooling water temperature from a water temperature sensor 15, an exhaust passage. 7, the control unit 11 calculates the fuel injection pulse width Ti based on these signals so that a mixture of the stoichiometric air-fuel ratio (target air-fuel ratio) is obtained. Then, the fuel injection from the fuel injection valve 8 is performed according to the calculated value. 9 is a spark plug.

A mechanical supercharger 21 for supercharging the air taken into the engine is provided upstream of the throttle valve 4. The rotation of the engine 1 is constantly transmitted to the supercharger 21 via a belt and a pulley (not shown), and the supercharger 21 is driven.

A bypass passage 22 is provided which bypasses the supercharger 21 and merges upstream of the throttle valve 4. A bypass valve 23 driven by a step motor (not shown) is provided in the bypass passage 22.

The control unit 11 also controls the opening of the bypass valve 23. That is, the control unit 11 determines whether or not the engine is in the supercharging region based on the throttle valve opening and the signal of the engine rotation speed detected by the throttle sensor 12. The opening degree of the bypass valve 23 is controlled so that the upstream pressure of the throttle valve 4 becomes equivalent to the atmospheric pressure and the upstream pressure of the throttle valve 4 becomes the target supercharging pressure equal to or higher than the atmospheric pressure in the supercharging region. Further, based on a signal of the actual supercharging pressure from the supercharging pressure sensor 17 provided immediately upstream of the throttle valve 4, at the time of acceleration when the actual supercharging pressure becomes lower than the target supercharging pressure, the bypass valve opening at the steady state is reduced. On the other hand, the boost pressure is corrected to increase, and conversely, during deceleration when the actual boost pressure becomes higher than the target boost pressure, the boost pressure decreases toward the steady state bypass valve opening. Is corrected.

The control content of the opening degree of the bypass valve executed by the control unit 11 will be further described with reference to the flowchart of FIG.

FIG. 2 is for calculating the target bypass valve opening tBPV, and is calculated at regular intervals (for example, 10 msec).
Every).

In step 1, the throttle valve opening TVO,
The engine speed NE and the actual supercharging pressure rPc are read, and among these, the throttle valve opening TVO and the engine speed NE are read.
In step 2, the target boost pressure tPc is calculated based on This calculation method includes target boost pressure data (FIG. 3) using the throttle valve opening and the engine speed as parameters.
Is created in advance in a map, and the map is searched for to obtain the map. Here, as shown in FIG. 3, the atmospheric pressure is equivalent to the atmospheric pressure when the throttle valve opening is about 50%, and the atmospheric pressure is proportional to the required load (throttle valve opening) when the throttle valve opening is about 50% or more. The above values are set as the target supercharging point.

In step 3, a basic bypass valve opening area tABPV1 is calculated by searching a map having the contents shown in FIG. 4 from the target supercharging pressure tPc and the engine speed NE. The basic bypass valve opening area tABPV1 is a bypass valve opening area in which a target boost pressure can be obtained in a steady state, and has a value that decreases as the target boost pressure tPc increases when the engine speed is constant as shown in FIG. is there. The actual values in FIG. 4 are obtained in advance from experiments according to the engine and the supercharger. The characteristics shown in FIG. 4 differ depending on the characteristics of the engine and the supercharger.

In step 4, the differential pressure .DELTA.Pc between the target supercharging pressure value tPc and the actual supercharging pressure rPc is calculated, and in step 5, a table having the contents shown in FIG. Correction value of valve opening area tKABP
V is calculated, and the target bypass valve opening area tABPV2 is calculated by multiplying the basic bypass valve opening area tABPV1 by the correction value tKABPV in step 6.

The correction value tKABPV is intended to cope with a response delay of the actual supercharging pressure rPc with respect to the target supercharging pressure value tPc during a transition such as acceleration.
For example, at the time of acceleration, the actual supercharging pressure rPc is increased due to a delay in the rise of the turbocharger rotation speed or the filling of the volume upstream of the throttle valve.
Rises later than the target supercharging pressure value tPc, and the output corresponding to the differential pressure ΔPc becomes insufficient. Similarly, at the time of deceleration, the actual supercharging pressure rPc falls later than the target supercharging pressure value tPc due to the falling delay of the turbocharger rotation speed or the presence of the volume upstream of the throttle valve, and the differential pressure ΔP
The output corresponding to c becomes excessive. In order to eliminate the output shortage during acceleration, the bypass valve opening area is corrected to the side where the boost pressure becomes higher in anticipation of the shortage of the actual boost pressure from the target boost pressure. T is the area
The ABPV 1 is reduced and corrected, and the bypass valve opening area is corrected to the side where the supercharging pressure is reduced in anticipation of the excess from the target value of the actual supercharging pressure in order to eliminate excessive output during deceleration. TABPV which is the bypass valve opening area
1 may be increased and corrected.

Therefore, at the time of acceleration when the actual supercharging pressure becomes smaller than the target supercharging pressure, the correction value tKABPV is given a value smaller than 1.0 to reduce the basic value tABPV1 so as to reduce the basic supercharging pressure. When the deceleration becomes larger, the correction value tK
By giving a value greater than 1.0 to ABPV, the basic value tABP
V1 is increased and corrected. As a result, at the time of acceleration in which the target bypass valve opening area tABPV1 in the steady state decreases stepwise, the target bypass valve opening area tABPV2 undershoots while the actual supercharging pressure deviates from the target value. At the time of deceleration in which the target bypass valve opening area tABPV1 increases stepwise, the target bypass valve opening area tABPV2 overshoots while the actual supercharging pressure deviates from the target value.

In step 7, the target bypass valve opening tB is searched by searching the table containing the contents of FIG. 6 from the target bypass valve opening area tABPV2 obtained in this manner.
Calculate PV.

The target bypass valve opening tBPV calculated in this manner is converted into a control amount to be applied to an actuator for driving the bypass valve in a flow (not shown), and this control amount is output to the bypass valve driving device.

Here, the operation according to the present embodiment will be described separately for a steady state and a transient state.

First, FIG. 7 shows a model of the target supercharging pressure, the collector internal pressure (pressure in the collector), the supercharger rotation speed, and the operation amount of the bypass valve in a steady state at a constant engine rotation speed. The “bypass valve operation amount” refers to a bypass valve opening or a bypass valve opening area.
Similarly, the “throttle valve operation amount” on the horizontal axis indicates the throttle valve opening or the throttle valve opening area.

In the region where the throttle valve operation amount is up to about 50%, the bypass valve 23 is opened so that the actual supercharging pressure is equivalent to the atmospheric pressure since the target supercharging pressure is equivalent to the atmospheric pressure. Since the supercharger 21 is constantly driven by the engine crankshaft, the air discharged by the supercharger 21 is supplied to the bypass passage 2.
2 again recirculates upstream of the supercharger 21. The amount of air taken into the cylinder is controlled by the throttle valve 4, and as a result, the pressure in the collector increases as the throttle valve operation amount increases. Since the supercharging pressure is controlled to the atmospheric pressure, the supercharging work is theoretically zero in this region. Actually, only the friction of the supercharger driven by the engine is lost, but the conventional example (Japanese Unexamined Patent Publication No.
No. 90, it is possible to reduce supercharged work.

When the throttle valve operation amount is in the region of about 50% or more, the target supercharging pressure becomes a value equal to or higher than the atmospheric pressure according to the required load (throttle valve operation amount). And the bypass valve 23 is gradually closed,
Only air not required for supercharging is returned to the upstream of the supercharger 21 via the bypass passage 22 again. Since the pressure in the collector is slightly reduced by the throttle valve 4, the pressure is slightly lower than the target boost pressure.

In the state where the throttle valve operation amount is 100% of the maximum, the throttle by the throttle valve 4 disappears, and the target supercharging pressure and the pressure in the collector match. Note that the bypass valve operation amount at this time is not necessarily zero. This may exceed the allowable supercharging pressure depending on the engine speed, depending on the combination of the size of the turbocharger and the engine, the setting of the rotation ratio of the gear and pulley connecting the turbocharger and the engine, etc. At this time, it is necessary to open the bypass valve.

Next, FIG. 8 schematically shows the operation of the throttle valve operation amount, the supercharger rotation speed, the bypass valve operation amount, and the supercharging pressure during acceleration under the constant engine speed condition. The target supercharging pressure increases in a stepwise manner with a stepwise change in the throttle valve operation amount, and the bypass valve 23 moves in the closing direction according to the increase in the target supercharging pressure. At this time, since the actual supercharging pressure rises with a delay, a difference between the actual supercharging pressure and the target supercharging pressure is generated (ΔPc> 0), and the correction value tKABPV of the bypass valve opening area is a positive value smaller than 1.0. Is calculated by The correction value tKABPV acts to undershoot the steady-state target value of the bypass valve opening area during acceleration (the correction value tKAPPV moves the bypass valve further in the closing direction), and the bypass valve operation amount becomes substantially the minimum value. It is zero. Therefore, all of the intake air is used to fill the volume upstream of the throttle valve, and the actual boost pressure rises quickly. Thereafter, as the actual boost pressure approaches the target boost pressure, the correction value tKABPV becomes 1.0
And the amount of operation of the bypass valve eventually converges to the steady target value.

As described above, according to the present embodiment, the correction value tKABP of the throttle valve opening area according to the differential pressure between the actual supercharging pressure and the target supercharging pressure is introduced. Since the undershoot is performed for tABPV1, the actual supercharging pressure can be raised more quickly than when the correction value tKABP is not introduced.

In this embodiment, the case where the supercharger is the mechanical supercharger 21 which is constantly driven by the engine crankshaft has been described. However, the turbocharger can be replaced with the mechanical supercharger 21. It is. If this is the second embodiment, the second embodiment is different from the conventional example,
A bypass valve is provided in the passage that bypasses the intake compressor of the turbocharger so that the upstream pressure of the throttle valve is equivalent to the atmospheric pressure in the non-supercharging region, and the upstream pressure of the throttle valve is higher than the atmospheric pressure in the supercharging region. The bypass valve is controlled so that the boost pressure is obtained. FIG. 9 shows the operation of the second embodiment overlapped with that of the conventional example. In the conventional example (see the broken line), the turbocharger rotation speed in the non-supercharged region is lower than in the second embodiment (see the solid line). This is because the turbocharger
Since the turbine is rotated by the flow rate and pressure of the exhaust gas, the exhaust side is bypassed as in the conventional example.
This is because the flow rate passing through the turbine is smaller than in the second embodiment in which the intake side is bypassed. Therefore, according to the second embodiment, the turbocharger rotation speed in the non-supercharged region is larger than that of the conventional example, and the correction value tKABP, which is not provided in the conventional example, is introduced to set the bypass valve to the steady-state target value during acceleration. As a result, the supercharging pressure response at the time of acceleration can be obtained more quickly than in the conventional example.

The control system diagram of FIG. 10 is a third embodiment, which replaces FIG. 1 of the first embodiment.

The supercharger 21 according to the first embodiment always transmits the engine rotation, whereas the third embodiment has a mechanical supercharger 31 which can be driven and stopped. Things. That is, the rotation of the engine 1 (or the rotation of the electric motor) is transmitted to the mechanical supercharger 31 via the belt, the pulley (not shown), and the electromagnetic clutch 32.

Now, as shown in FIG. 7, the supercharging is really required in the region where the throttle valve operation amount is about 50% or more. If the supercharger is driven even in a region less than this, a driving loss occurs. Therefore, it is conceivable to stop the operation of the supercharger 31 by disconnecting the electromagnetic clutch 32 in a region where the throttle valve operation amount is less than about 50%. On the other hand, there is a response delay between the time when the electromagnetic clutch 32 is connected and the time when the supercharging pressure actually rises.
If the supercharging is started by connecting the electromagnetic clutch 32 at the timing of 0%, the supercharging pressure does not rise quickly, and a desired feeling of acceleration cannot be obtained. Therefore, in the third embodiment, the supercharger 31 is rotated in advance by connecting the electromagnetic clutch 32 even when the throttle valve operation amount is less than a predetermined value (for example, about 40%) smaller than about 50% to about 50%. In this way, the electromagnetic clutch 32 is not connected in the region below the predetermined value so that no drive loss occurs (see FIG. 14). In addition, about 4
Although the numerical value of 0% is mentioned, the present invention is not limited to this.
Ultimately, the matching may be determined so that the driving loss of the supercharger is reduced as much as possible while obtaining good acceleration.

The control performed by the control unit 11 will be described with reference to FIG. 11. First, the flowchart of FIG. 11 is for connecting and disconnecting the electromagnetic clutch 32. In step 11, the throttle valve opening TVO
And the engine rotational speed NE are read, and in step 12 it is determined whether the electromagnetic clutch is to be connected or disconnected. Connection area of electromagnetic clutch,
As shown in FIG. 12, the cutting region is determined in advance by using the throttle valve opening and the engine speed as parameters. When the operating point determined from the throttle valve opening and the engine speed is above the boundary (oblique line) shown in the drawing. Flag FCLCH
ON is set to FCLCHON = 1, and when it is below the boundary shown in the figure, the flag FCLCHON is set to FCLCHON = 0. From this, FCLCHON = 1 indicates that the electromagnetic clutch is in the connection area, and FCLCHON = 0 indicates that the electromagnetic clutch is in the disconnection area.

The reason why the boundary value is increased in proportion to the engine speed in FIG. 12 is as follows. It is necessary to start driving the supercharger near the saturation region of the intake air amount. In this case, the relationship between the throttle valve opening TVO and the amount of intake air is generally such that as the engine speed NE increases, the saturation region of the intake air increases as the engine rotation speed NE increases, as shown in FIG. Accordingly, the opening degree of the throttle valve at the start of driving the supercharger by connecting the electromagnetic clutch in accordance with this is increased as the engine speed increases.

Returning to FIG. 11, in step 13, the flag FC is set.
Look at LCHON. When FCLCHON = 1 (when it is in the connection area of the electromagnetic clutch), the process proceeds to step 14,
Connect the electromagnetic clutch to drive the supercharger, FCLCHO
When N = 0 (when the electromagnetic clutch is in the disconnection region), the routine proceeds to step 15, where the electromagnetic clutch is disconnected to stop the supercharger.

In a region where the throttle valve operation amount is up to about 40%, the supercharger 31 does not operate (the electromagnetic clutch 32 is not connected), and the intake air is throttled by bypassing the turbocharger 31 in the stopped state. Since it will flow upstream of valve 4,
In the control unit 11, the pressure drop does not occur between the bypass valve 23 upstream and the throttle valve 4 upstream (so that the throttle valve 4 upstream is equivalent to the atmospheric pressure).
The bypass valve opening is controlled, and when the region becomes other than that, the bypass valve opening is controlled in the same manner as in the first embodiment. However, since the flow for calculating the target bypass valve opening is not changed, FIG. 2 of the first embodiment can be used.

Also in the third embodiment, the steady-state pressure, the supercharger rotation speed, and the operation amount of the bypass valve in the steady state at the constant engine speed are shown in FIG.
FIG. 15 schematically shows the changes in the turbocharger rotation speed, the bypass valve operation amount, the throttle valve operation amount, and the supercharging pressure during the acceleration in the connected state and under the constant engine speed condition.

First, referring to FIG. 14, FIG.
The difference from the above is mainly in a region where the throttle valve operation amount is up to about 40% (in the figure, indicated by a “supercharging transition region”). That is,
In the region where the throttle valve operation amount is up to about 40%, the turbocharger 3
1 is stopped, and the intake air is caused to flow to the upstream of the throttle valve 4 by bypassing the turbocharger 31 in the stopped state, so that a pressure drop does not occur between the upstream of the bypass valve 23 and the upstream of the throttle valve 4. The bypass valve operation amount is controlled (so that the upstream of the throttle valve is equivalent to the atmospheric pressure).

Next, in the region where the throttle valve operation amount is from about 40% to about 50%, the electromagnetic clutch 32 is connected and the engine rotation is transmitted to the supercharger 31, so that the supercharger rotation speed becomes a predetermined value. Although the step changes (see the solid line in the middle part of FIG. 14), the bypass valve operation amount is controlled so that the target supercharging pressure becomes equivalent to the atmospheric pressure (at this time, the air discharged by the supercharger 31 is passed through the bypass passage 22). Circulates again upstream of the supercharger 31).

As described above, according to the third embodiment, as much as possible in the turbocharger stop region (the region where the throttle valve operation amount is from 0% to about 40%, in the drawing, the non-supercharge region), the first embodiment Supercharged work can be further reduced.

In the third embodiment, since the supercharger is turned in advance in a region (supercharging transition region) adjacent to the supercharging region in the non-supercharging region, the non-supercharging region is switched to the supercharging region. The discharge flow rate of the supercharger at the initial stage of the replacement is increased, whereby the same operation and effect as in the first embodiment are produced (see FIG. 15).

The control system diagram of FIG. 16 is a fourth embodiment, which replaces FIG. 10 of the third embodiment.

In the third embodiment, the throttle valve is mechanically linked with the accelerator pedal 3, whereas
In the fourth embodiment, an electronic control throttle device is provided. That is, a so-called electronic control throttle device 41 that drives the opening and closing of the throttle valve 4 by an actuator (such as a motor) 42 is interposed in the intake passage 2, and the actual opening detected by the throttle sensor 43 is transmitted from the control unit 11. The throttle valve 4 is driven via the actuator 42 or the like so as to match the target opening command.

The accelerator pedal 3 is provided with an accelerator sensor 44 for detecting the accelerator opening. The control unit 11 calculates a target intake air amount (per cycle) based on the accelerator opening and the engine speed signal from the accelerator sensor 44, and calculates a target supercharging pressure from the target intake air amount and the engine speed. Is calculated. In an engine having the electronic control throttle device 41, the target intake air amount and the target supercharging pressure are two main parameters for controlling the throttle valve 4, the bypass valve 23, and the electromagnetic clutch 32. That is, the target throttle valve opening is calculated from these two, and the throttle valve opening (output) of the engine is controlled in accordance with the calculated value (command).

The basic bypass valve opening area is calculated from these two values. Based on the calculated value, the upstream pressure of the throttle valve 4 is equivalent to the atmospheric pressure in the non-supercharging region, and the throttle pressure is calculated in the supercharging region. The control of the opening degree of the bypass valve is performed so that the upstream pressure of the valve 4 becomes the target supercharging pressure equal to or higher than the atmospheric pressure, and it is determined from these two whether or not the supercharging region is present. When determined, the electromagnetic clutch 32 is disconnected, and when determined to be in the supercharging region, the electromagnetic clutch 32 is connected. Further, based on the signal of the actual supercharging pressure, at the time of acceleration in which the actual supercharging pressure becomes lower than the target supercharging pressure, the opening degree of the bypass valve in the steady state is corrected to the side where the supercharging pressure increases, At the time of deceleration when the actual supercharging pressure becomes higher than the target supercharging pressure, the opening degree of the bypass valve in the steady state is corrected to the side where the supercharging pressure decreases.

The control unit 11 also sets a stoichiometric air-fuel ratio or an air-fuel ratio leaner than the stoichiometric air-fuel ratio as a target air-fuel ratio in accordance with operating conditions, and performs fuel injection so as to obtain an air-fuel mixture having the set target air-fuel ratio. The pulse width Ti is calculated, and fuel is injected from the fuel injection valve 8 according to the calculated value.

The control of the throttle valve 4 and the bypass valve 23 will be further described with reference to the flowchart of FIG. This figure is for calculating the target throttle valve opening and the target bypass valve opening. The same steps as those in FIG. 2 are denoted by the same step numbers.

The main differences from the third embodiment will be described. In step 21, the accelerator opening APO, engine speed NE, and actual supercharging pressure rPc are read.
In steps 2 and 23, a target intake air amount and a target supercharging pressure are calculated.

First, at step 22, the accelerator opening APO
In step 22, the target intake air amount (per cycle) tQa is calculated based on the engine speed NE and the engine speed NE. As a calculation method, data of a target basic intake air amount (a value in a stoichiometric air-fuel ratio range, not shown) using the accelerator opening and the engine rotation speed as parameters is prepared in a map in advance, and the map is searched. The target intake air amount tQa (= tQa0 / TFBY) is obtained by dividing the target basic intake air amount tQa0 obtained by the above by the target equivalent ratio TFBYA.
A) There is a method of obtaining it. Since the target equivalent ratio TFBYA is smaller than 1.0 in the lean air-fuel ratio range, the target intake air amount is larger in the lean air-fuel ratio range even if APO and NE are the same.

In step 23, a target supercharging pressure tPc is calculated by searching a map having the contents shown in FIG. 18 from the target intake air amount tQa and the engine speed NE.
The target supercharging pressure also differs between the stoichiometric air-fuel ratio range and the lean air-fuel ratio range.However, it is complicated to describe the difference in the air-fuel ratio range. State.

In step 24, the target throttle valve opening tTVO is calculated by searching a map having the contents shown in FIG. 19 from the target supercharging pressure tPc and the target intake air amount tQa thus obtained.

Similarly, a basic bypass valve opening area tA is retrieved from the target supercharging pressure tPc and the target intake air amount tQa by searching a map having the contents shown in FIG.
Calculate BPV1. As shown in FIG. 20, the value of tABPV is equal to the target supercharging pressure t when the target intake air amount tQa is constant.
The higher the value of Pc, the smaller the value, and the target boost pressure tPc
Is constant, the value decreases as the target intake air amount tQa increases. The actual values in FIG. 20 are obtained in advance by adaptation or the like. The characteristics in FIG. 20 differ depending on the characteristics of the engine and the supercharger.

In the following steps 4 to 7, the target bypass valve opening is calculated in the same manner as in the third embodiment.

The target bypass valve opening and the target throttle valve opening tTVO calculated in this manner are controlled by a control amount given to the bypass valve driving actuator and a control amount given to the throttle valve driving actuator 42 in a flow (not shown). The control amount given to the bypass valve driving actuator is output to the bypass valve driving device, and the control amount given to the actuator 42 is output to the actuator 42.

FIG. 21 is a flowchart for connecting and disconnecting the electromagnetic clutch 32 of the fourth embodiment.
It replaces FIG. 11 of the embodiment. FIG.
The same steps as in FIG. 1 have the same step numbers.

FIG. 11 of the third embodiment is different from FIG.
The only difference is that the parameters used to determine whether the region is a region to connect 2 or a region to be disconnected are different. That is, in step 31, the target supercharging pressure tPc and the target intake air amount tQa are read, and
It is determined whether the region is a region for connecting or disconnecting the electromagnetic clutch. The connection region and the disconnection region of the electromagnetic clutch have the target boost pressure t as shown in FIG.
Pc and the target intake air amount tQa are predetermined as parameters, and the flag FCLCHON is set to FCLCHON = 1 when the operating point determined from the target supercharging pressure tPc and the target intake air amount tQa is on the right side of the illustrated boundary (see the broken line). When the flag is on the left side of the illustrated boundary, the flag FCLCHO
Let N be FCLCHON = 0. From this FCLCHO
N = 1 indicates that the electromagnetic clutch is in the ON region,
CHON = 0 indicates that the electromagnetic clutch is in the OFF region. Note that FIG. 22 shows a setting example of the target supercharging pressure (see the solid line) in an overlapped manner. FIG. 22 shows the timing at which the electromagnetic clutch is connected to operate the supercharger and the point where the target supercharging pressure> atmospheric pressure. It can be seen that is different.

The model of the pressure, supercharger rotation speed, and bypass valve operation amount in steady state at a constant engine speed in the fourth embodiment is shown in FIG. 23. As in the embodiment, it is possible to reduce the supercharging work by the turbocharger stop region (the non-supercharged region in the figure).

In order to clarify the difference from the third embodiment, when the target intake air amount is A, the accelerator operation amount is about 40%, and when the target intake air amount is B, the accelerator operation amount is about 50%. Suppose there is. Now, in the fourth embodiment, the throttle valve 4 can be operated freely with respect to the accelerator pedal 3, so that the accelerator operation amount is about 50% and the throttle valve operation amount is the maximum as shown in the lowermost part of FIG. Is set to be 100%. As a result, the maximum intake air amount in the natural intake (NA) can be obtained when the accelerator operation amount is about 50%. As a result, the accelerator operation amount is about 50%
In the above range, the throttle valve operation amount is fixed at 100%, and the intake air amount is controlled only by the upstream pressure of the throttle valve 4. In this region, the intake air is not throttled by the throttle valve 4, so that the pressure in the collector is almost equal to the target boost pressure. Of course, the combination of the target supercharging pressure and the throttle valve operation amount at the equal intake air amount is not limited to the one shown in FIG. 23, and the combination that is the most efficient for the engine and does not affect the drivability is used. It can be arbitrarily selected (for example, FIG. 24 shows another embodiment (fifth embodiment)). The effect of the electronically controlled throttle device allows the non-supercharged area to be widened and the loss due to the throttle throttle at the time of supercharging to be reduced, so that the engine is more efficient than the third embodiment.

In the fourth embodiment, the accelerator operation amount, the turbocharger rotation speed, the bypass valve operation amount, the throttle valve operation amount, and the operation of the supercharging pressure in the transient state under the condition of the constant engine speed are modeled. FIG. 25 is the same as FIG. 15 of the third embodiment.

In the first and second embodiments, the case where the target supercharging pressure is set only from the engine state without considering the vehicle state has been described. Can be considered. For example, FIG.
As shown in (Sixth Embodiment), the target driving force is calculated from the vehicle speed VSP and the throttle valve opening TVO, and the target driving force is divided by the gear ratio to calculate the target engine torque.
The required air amount is calculated by searching a predetermined map from the target engine torque and the engine rotation speed, and a map having the same characteristics as in FIG. 3 is searched from the required air amount and the engine rotation speed to determine the target supercharging point. What is necessary is just to comprise so that calculation may be performed.

In the third and fourth embodiments, the case where the supercharging transition region is provided has been described. However, the present invention is not limited to this.
The supercharging transition area may not be provided (see the dashed line in the middle part of FIG. 14 and the middle part of FIG. 23). However, when the supercharging transition region is provided, it is needless to say that the supercharging pressure rising responsiveness is improved at the time of acceleration switching from the non-supercharging region to the supercharging region as compared with the case where there is no supercharging transition region. . In FIG. 14, the bypass valve operation amount becomes zero at the point where the throttle valve operation amount becomes maximum, and in FIGS. 23 and 24, the bypass valve operation amount becomes zero at the point where the target intake air amount becomes maximum. Although the case is shown, the operation amount of the bypass valve is not necessarily zero at the point where the throttle valve operation amount and the target intake air amount become maximum, as in the first embodiment.

In the embodiment, the fuel injection valve 8 is configured to inject fuel directly into the cylinder, but may be configured to inject fuel into the intake port.

[Brief description of the drawings]

FIG. 1 is a control system diagram of one embodiment (first embodiment).

FIG. 2 is a flowchart for explaining a calculation of a target bypass valve opening.

FIG. 3 is a characteristic diagram of a target supercharging pressure.

FIG. 4 is a characteristic diagram of an opening area of a basic bypass valve.

FIG. 5 is a characteristic diagram of a correction value of a bypass valve opening area.

FIG. 6 is a characteristic diagram of a target bypass valve opening degree.

FIG. 7 is an explanatory diagram of an operation in a steady state at a constant engine rotation speed.

FIG. 8 is an operation explanatory diagram at the time of acceleration at a constant engine rotation speed.

FIG. 9 is an operation explanatory diagram of the second embodiment during acceleration at a constant engine speed.

FIG. 10 is a control system diagram of a third embodiment.

FIG. 11 is a flowchart for explaining connection / disconnection control of an electromagnetic clutch according to a third embodiment.

FIG. 12 is a connection / disconnection area diagram of an electromagnetic clutch.

FIG. 13 is a characteristic diagram of an intake air amount with respect to a throttle valve opening.

FIG. 14 is a diagram illustrating an operation of the third embodiment in a steady state at a constant engine speed.

FIG. 15 is an operation explanatory diagram of the third embodiment during acceleration at a constant engine speed.

FIG. 16 is a control system diagram of a fourth embodiment.

FIG. 17 is a flowchart illustrating a calculation of a target throttle valve and a target bypass valve opening according to the fourth embodiment;

FIG. 18 is a characteristic diagram of a target boost pressure according to a fourth embodiment.

FIG. 19 is a characteristic diagram of a target throttle valve opening degree of the fourth embodiment.

FIG. 20 is a characteristic diagram of a basic bypass valve opening area according to the fourth embodiment.

FIG. 21 is a flowchart for explaining connection / disconnection control of an electromagnetic clutch according to a fourth embodiment;

FIG. 22 is a connection / disconnection area diagram of an electromagnetic clutch according to a fourth embodiment.

FIG. 23 is an explanatory diagram of the operation of the fourth embodiment in a steady state at a constant engine rotation speed.

FIG. 24 is a diagram illustrating the operation of the fifth embodiment in a steady state at a constant engine speed.

FIG. 25 is a diagram illustrating the operation of the fourth embodiment during acceleration at a constant engine speed.

FIG. 26 is a block diagram for explaining calculation of a target supercharging pressure according to the sixth embodiment.

FIG. 27 is a diagram corresponding to claims of the first invention.

[Explanation of symbols]

 Reference Signs List 4 throttle valve 8 fuel injection valve 11 control unit 17 supercharging pressure sensor 21 mechanical supercharger 22 bypass passage 23 bypass valve 31 mechanical supercharger 32 electromagnetic clutch 41 electronic control throttle device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Taku Oba Nissan Motor Co., Ltd. F-term (reference) 3G005 EA04 EA16 EA19 FA04 GA12 GB18 GB48 GC07 GD02 GD03 GD05 JA06 JA12 JA24 JA39 JA45 JA51 JB02 3G092 AA01 AA09 AA18 BA01 BA04 BB01 DB02 DB03 DC01 DC02 DC03 DC04 EA14 EA26 EA27 EC01 EC09 FA03 FA10 FA25 GA12 GA13 HA01X HA01Z HA06Z HA10X HA16X HA16Z HB01X HD05Z HE01Z HE03Z HE08Z11 HA01Z01Z01Z01Z0108 PB03A PD02A PD02Z PE01Z PE03Z PE08Z PF03Z PF06Z

Claims (8)

[Claims] 1. A supercharger for pressurizing air taken into an engine upstream of a throttle valve, a passage for bypassing the supercharger, a bypass valve for adjusting an air flow rate flowing through the bypass passage, Means for judging whether the engine is in a supercharged area or a non-supercharged area, and based on the result of the judgment, the upstream pressure of the throttle valve is equivalent to the atmospheric pressure in the non-supercharged area, and the upstream of the throttle valve in the supercharged area. Means for controlling the bypass valve so that the pressure becomes a target supercharging pressure equal to or higher than the atmospheric pressure. 2. The engine control device according to claim 1, wherein the supercharger is a turbocharger or a mechanically driven mechanical supercharger. 3. The bypass valve control means includes means for setting a target boost pressure in accordance with operating conditions, means for calculating a bypass valve control amount in accordance with the target boost pressure, and a bypass valve control amount. 3. The control device for an engine according to claim 1, further comprising means for controlling the bypass valve so as to satisfy the following condition. 4. A means for detecting the upstream pressure of the throttle valve as an actual supercharging pressure, wherein when the actual supercharging pressure is lower than the target supercharging pressure, the supercharging pressure increases with respect to the bypass valve control amount. 4. The engine control device according to claim 3, wherein the correction is performed. 5. A means for detecting an upstream pressure of a throttle valve as an actual supercharging pressure, wherein when the actual supercharging pressure is higher than a target supercharging pressure, the supercharging pressure decreases with respect to the bypass valve control amount. 4. The engine control device according to claim 3, wherein the correction is performed. 6. The supercharger according to claim 1, wherein the supercharger is a mechanical supercharger capable of being driven and stopped, and the mechanical supercharger is stopped in a non-supercharge region. An engine control device according to any one of the preceding claims. 7. A region for driving a mechanical supercharger adjacent to the supercharging region in the non-supercharging region.
An engine control device according to claim 1. 8. The engine control device according to claim 1, wherein the throttle valve is electrically drivable.