JP2969296B2 - Engine control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device.

[0002]

2. Description of the Related Art Conventionally, there has been a concept of so-called slip control for temporarily reducing engine torque when a wheel slips to eliminate a slip state. For example, as disclosed in Japanese Patent Application Laid-Open No. 61-157728, a main throttle valve interlocked with an accelerator pedal and a sub-throttle valve opened and closed independently of the main throttle valve are provided in an intake passage of an engine. There has been proposed an arrangement in which the sub-throttle valve is closed in the event of a slip to reduce the intake pressure, thereby reducing the engine torque when a slip occurs.

On the other hand, in an engine provided with an exhaust turbocharger, it is necessary to set a supercharging pressure (ie, intake pressure) to an optimum value corresponding to an operating state of the engine. As one of the means, for example, Japanese Patent Publication No. 62-972
No. 3 discloses a valve mechanism capable of adjusting a turbine pre-pressure of an exhaust turbocharger, and converges a supercharging pressure to a target supercharging pressure set according to an operating state of an engine in advance. In order to provide feedback control of the valve mechanism, a proposal has been made.

In an engine with an exhaust turbocharger, if the supercharging pressure exceeds a predetermined value and abnormally rises, for example, when the supercharging pressure feedback control system fails, the reliability of the engine itself is reduced. It is also known that, when the supercharging pressure is abnormally increased, for example, the fuel pressure is temporarily reduced and the intake pressure is urgently reduced due to the possibility of damage.

[0005]

In an engine in which the supercharging pressure is feedback-controlled, a main throttle valve and a sub-throttle valve are arranged in series in an intake passage of the engine. When the engine torque is temporarily reduced by closing the valve, there is a concern that driving performance may be impaired due to occurrence of an acceleration shock as described below.

That is, for example, a high-speed high-load operation state (ie,
(Main throttle valve is almost fully open)
Consider the case where a slip has occurred. In this case,
If the accelerator pedal continues to be depressed as it is (that is, if the main throttle valve is kept fully open), the supercharging pressure control system determines that a high load request is still being issued. No pressure reducing action is taken. When the sub-throttle valve closes in this state, the intake pressure decreases, the output torque of the engine decreases, and the slip state is gradually eliminated. So far,
Even though the driver depresses the accelerator pedal, the driver does not feel much discomfort because the driver recognizes the occurrence of slip because the acceleration is poor.

[0007] However, when the slip condition is eliminated due to a decrease in engine torque, the sub-throttle valve is opened again. Then, with the opening of the sub-throttle valve, a large amount of intake air is sent to the engine side through the main throttle valve which is almost fully opened, so that the amount of exhaust gas increases sharply and the supercharging action of the turbine is further enhanced. You. Also, at this time,
(That is, the exhaust pressure on the upstream side of the turbine) decreases significantly even when the intake air amount is reduced temporarily by the sub-throttle valve due to the relatively large volume on the upstream side of the turbine. And maintained at a fairly high pressure. As a result of these synergistic effects, the supercharging pressure temporarily exceeds the set value and excessively increases. In response to this, for example, a temporary fuel cut is performed to secure the reliability of the engine. The torque tends to decrease.

[0008] In this case, immediately after the driver feels that the slip state has been eliminated by the initial decrease in engine torque and the acceleration has been restored, the engine torque is reduced again by the fuel cut and the acceleration is deteriorated. This is recognized as an acceleration shock, and as a result, the driver has an unfavorable impression on drivability.

Accordingly, the present invention relates to an engine with an exhaust turbocharger provided with a sub-throttle valve in addition to a main throttle valve, a temporary operation associated with a series of operations of opening, closing, and opening the sub-throttle valve. Recognizing that an excessive increase in the intake pressure does not have any effect on ensuring the reliability of the engine, it limits the execution of the intake pressure limiting action by means such as fuel cut in such a case, thereby accelerating It is an object of the present invention to provide an engine control device capable of preventing both the occurrence of a shock and ensuring the reliability of the engine during normal operation.

[0010]

In the present invention, FIGS. 1A and 1B show specific means for solving such a problem.
According to the first aspect of the present invention, the main throttle valve 7 mechanically connected to the accelerator pedal and the traveling state determination means 45 are provided in the intake passage 2 of the engine 1.
A sub-throttle valve 8, which is electrically controlled to open and close by a sub-throttle valve drive circuit 46 in accordance with the traveling state of the vehicle output from the vehicle, is arranged in series, while an upstream side of the main throttle valve 7 and the sub-throttle valve 8 is arranged. The exhaust turbocharger 4 is provided at the position, and the intake pressure is controlled by the engine speed and the main throttle valve 7.
Pressure feedback control circuit 4 for causing the target intake pressure map 44 to converge to the target intake pressure read out by the target intake pressure setting means 41 based on the opening degree of the intake pressure.
In an engine control apparatus having an intake pressure control means (specifically, a wastegate valve) 11 whose operation is feedback-controlled by a control signal from the control signal from the intake pressure limiting means 40 for limiting a rise change of the intake pressure. The operation of the intake pressure limiting means 40 is limited for a predetermined time when the sub-throttle valve 8 is opened from the closed state.

According to a second aspect of the present invention, in the engine control device of the first aspect, the intake pressure limiting means 4 is provided.
0 based on a signal output from the intake pressure determination means 47 when the intake pressure becomes equal to or higher than the set value 41.
A fuel supply restricting means 48 for restricting fuel supply to the sub-throttle valve drive circuit 46 outputs an opening operation of the sub-throttle valve 8 from a closed state in which the main throttle valve 7 has a predetermined opening degree or more and the sub-throttle valve 8 is in a closed state. And a control means 51 for limiting the operation of the fuel supply limiting means 48 for a predetermined time.

According to a third aspect of the present invention, in the engine control device according to the first aspect, the intake pressure limiting means 4 is provided.
0 is set to the target value for a predetermined time when the main throttle valve 7 is not less than a predetermined opening degree and an opening operation is detected from a closed state of the sub throttle valve 8 by an output signal from the sub throttle valve driving circuit 46. 44 is characterized by comprising a correcting means 50 for correcting in the decreasing direction.

[0013]

In each invention of the present application, the following effects can be obtained by adopting such a configuration.

According to the first and second aspects of the present invention, the opening of the main throttle valve 7 (ie, the opening of the main throttle valve 7 during normal operation)
By performing feedback control of the intake pressure control means 11 according to the engine load, the supercharging pressure (ie, intake pressure) is controlled so as to always converge to the target value. In this case, the sub-throttle valve 8 is always kept fully open.

On the other hand, when the running state of the vehicle becomes a specific state, that is, a slip state, this is detected and the sub-throttle valve 8 is closed to lower the intake pressure to lower the engine output torque. The slip condition is eliminated smoothly. Then, the closing operation of the sub-throttle valve 8 is continued until the slip state is eliminated, and when the slip state is eliminated, the valve is opened again.

In this case, when the main throttle valve 7 is not less than the predetermined opening and the opening operation is detected from the closed state of the sub-throttle valve 8 (ie, immediately after the slip state is eliminated and the intake air is temporarily stopped). In a state where the pressure may increase), the control unit 51 limits the operation of the fuel supply limiting unit 48 for a predetermined time.
(In other words, the execution of the fuel cut is restricted even for the predetermined time even in the execution area of the fuel cut). Therefore, there is no decrease in the engine torque due to the temporary fuel cut immediately after the sub-throttle valve 8 is opened. Therefore, the occurrence of an acceleration shock is also prevented. Specifically, FIG.
As shown in FIG. 5, when the sub-throttle valve 8 is opened from the closed state, the normal overcharging pressure determination pressure (Pm
ax2) is increased by a predetermined value for a predetermined time (T) by a predetermined value (Pmax
By changing the setting to 1), the fuel cut is not executed even in the state where the pressure value has reached the value at which the fuel cut is normally executed (see the range a in FIG. 2). .

According to the first and third aspects of the present invention, the intake pressure control during normal operation and the control for eliminating the slip when a slip condition occurs are the same as those described above, but the sub-throttle valve after the cancellation of the slip. 8
The control mode of the intake pressure at the time of the opening operation from the valve closed state is different. That is, when the opening of the main throttle valve 7 is detected from the closed state of the sub-throttle valve 8 while the opening degree of the main throttle valve 7 is equal to or more than the predetermined opening degree, the correcting means 50 performs the predetermined time (T) as shown in FIG. Target value of intake pressure
(Ie, the target boost pressure) is set lower by a predetermined pressure. By doing so, the feedback control by the intake pressure control means 11 of the intake pressure (indicated as the intake manifold pressure) which rises with the opening of the sub-throttle valve 8 is performed, for example, by setting the target supercharging pressure to a constant value on the high pressure side as in the past. Value, the control constant is smaller by an amount corresponding to a smaller deviation between the actual pressure value and the target supercharging pressure than in the case where the target pressure is maintained. Overshoot exceeding the supercharging pressure and reaching the overcharging pressure judgment pressure or more, smoothly converges to the target value (corrected value) without overshoot as shown by the real curve, Exceeding the boost pressure determination pressure is prevented beforehand.

As a result, unnecessary torque-down operation is prevented from being performed due to a temporary increase in intake pressure caused by the opening operation of the sub-throttle valve 8 from the closed state.

[0019]

Therefore, according to the engine control apparatus of the present invention, the operation of the intake pressure limiting means 40 is limited for a predetermined time when the sub-throttle valve 8 is opened from the closed state. Therefore, the occurrence of an acceleration shock due to the operation of lowering the engine torque unnecessary for securing the reliability of the engine is prevented beforehand, and the operability of the engine is improved. The operation of the intake pressure limiting means 40 reliably protects the engine when abnormal intake pressure is generated, and improves its reliability.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an engine control apparatus according to an embodiment of the present invention.

First Embodiment FIG. 1A shows a system diagram of an automobile engine 1 provided with a control device according to an embodiment of the present invention described in claims 1 and 2 of the present application. An intake passage 3 of the engine 1 is an exhaust passage, and an exhaust turbocharger 4 including a turbine 5 and a blower 6 is disposed between the intake passage 2 and the exhaust passage 3. Also, this exhaust tar
At the position near the turbine 5 of the turbocharger 4, the turbine 5
A bypass 16 is provided for bypassing the air and connecting the upstream side and the downstream side thereof.
The waist which opens and closes and adjusts the supercharging effect of the blower 6 by adjusting the turbine pre-pressure so as to increase or decrease the intake pressure (ie, supercharging pressure) on the downstream side of the blower 6. A gate valve 11 (corresponding to intake pressure control means in the claims; see FIG. 1B) is provided.

The wastegate valve 11
Is driven to open and close by a pressure-responsive actuator 12 that operates according to the supercharging pressure on the downstream side of the blower 6 introduced through the negative pressure introducing pipe 15. Further, the opening degree of the waste gate valve 11 itself is controlled by adjusting the amount of atmospheric pressure introduced from the upstream side of the blower 6 through the atmospheric pressure introducing pipe 15 by the control valve 13. still,
The control valve 13 operates based on a control signal output from an engine control unit 20 to be described later according to an opening degree of a main throttle valve 7 to be described later. It works so as to generate a supercharging pressure corresponding to the opening (that is, the engine load).

On the other hand, a surge tank 10 is formed at a position downstream of the blower 6 in the intake passage 2,
On the downstream side of the surge tank 10, an injector 9 is provided.
Between the surge tank 10 and the blower 6, a main throttle valve 7 and a sub-throttle valve 8 are arranged in series one after another. Of the main throttle valve 7 and the sub-throttle valve 8, the main throttle valve 7 is mechanically connected to an accelerator pedal to produce an opening corresponding to the amount of depression of the accelerator pedal. Is the throttle opening sensor 2
1 is input to an engine control unit 20 described later. On the other hand, the sub-throttle valve 8 has a configuration independent of the main throttle valve 7 and is opened and closed by an electric actuator 22 that operates based on a control signal from an engine control unit 20 described later. It has become. The surge tank 10 is provided with a boost sensor 23, and the intake pressure detected by the boost sensor 23 is input to an engine control unit 20, which will be described later.

The engine control unit 20
Receives the engine pressure signal and a slip signal from a slip control unit 25, which will be described later, in addition to the intake pressure signal and the opening signal of the main throttle valve 7, and performs fuel control and intake pressure control (ie, supercharging). Pressure control) and slip control. As shown in FIG. 1B, a target intake pressure corresponding to the current operating state is obtained from a target intake pressure map 44 based on the engine speed and the main throttle valve opening. Target intake pressure setting means 41 to be set
Based on the output signal from the target intake pressure setting means 41, the opening degree of the wastegate valve 11 (strictly, the duty ratio of the control valve 13) is feedback-controlled so that the intake pressure converges to a target value. An intake pressure feedback control circuit 42 and a sub-throttle valve driving circuit 46 that receives a control signal from a slip control unit 25 described later and causes the actuator 22 to drive the sub-throttle valve 8.
Is compared with an actual intake pressure and a preset set value (specifically, an overcharging pressure determination pressure described later) 49. If the actual intake pressure exceeds this set value, the engine protection operation is performed. And a fuel cut-off signal to output a fuel cut signal to the injector 9 for urgently reducing the intake pressure based on a signal from the intake pressure judgment means 47. Supply limiting means 4
8, when the main throttle valve opening degree is a predetermined abnormality and a signal indicating the opening and closing operation of the sub-throttle valve 8 is inputted from the sub-throttle valve driving circuit 46, the operation of the fuel supply restricting means 48 for a predetermined time. (Specifically, as shown in FIG. 2, a control means 51 for setting the overcharging pressure determination pressure higher for a predetermined time).

The engine control unit 20 in a second embodiment described later replaces the control means 51 with a signal indicating that the opening degree of the main throttle valve is greater than a predetermined value and that the sub-throttle valve 8 is closed → opened. As shown in FIG. 6, a correction means 50 is provided for correcting the target supercharging pressure to a lower value by a predetermined value when it is input.

The slip control unit 25
Calculates the slip ratio between the rotational speeds of the front and rear wheels of the vehicle to determine whether a slip has occurred, and outputs a slip signal to the engine control unit 20 when a slip occurs. (See FIG. 8).

Next, the basic concept of engine control by the control device constructed as described above will be described with reference to the intake passage 2. First, the target boost pressure is the target boost pressure, which is the opening degree of the main throttle valve 7. Is fixedly set in advance corresponding to. Further, the overcharging pressure determination pressure (Pmax), which is a reference for executing the fuel cut, is determined in a normal operation state (that is, a predetermined time after the sub-throttle valve 8 is opened from the closed state.
(Operating states other than (T)), the target boost pressure (Pma
x) is set to a value (Pmax2) higher than the normal value (Pmax2) only for a predetermined time after the sub-throttle valve 8 is opened from the closed state. (Pmax1). It should be noted that the change of the overcharging pressure determination pressure is performed by the control means 51 as described above.

First, during normal operation, the control valve 13 is operated by a control signal output from the engine control unit 20 based on the opening degree of the main throttle valve, and the intake pressure is adjusted to the target supercharging corresponding to the operating state of the engine. Controlled by pressure.

On the other hand, when a slip occurs and a slip signal is input from the slip control unit 25 to the engine control unit 20, the sub-throttle valve 8 is closed by the actuator 22 in response thereto, and the sub-throttle valve 8 is closed. Downstream intake pressure,
That is, the pressure in the intake manifold is reduced, whereby the engine torque is suppressed, and the slip canceling operation is started. The relative relationship between the intake pressure, the exhaust pressure, and the opening degree of the main throttle valve 7 and the sub throttle valve 8 during the slip control is shown in a portion before time (t) in FIG.

That is, during the slip control, the main throttle valve 7 is fully opened and the sub throttle valve 8 is fully closed. Further, since the intake air amount is reduced by the sub-throttle valve 8, the pressure in the intake manifold is low. However, the intake pressure on the upstream side of the sub-throttle valve has a relatively large volume on the upstream side of the blower 6. Since the pre-pressure is maintained at a certain value, it is set to a pressure slightly higher than the atmospheric pressure.
The opening of the sub-throttle valve 8 in this case varies depending on the magnitude of the slip (that is, the slip ratio) and is not constant.

When the elimination of the slip state is detected by a signal from the slip control unit 25,
From this time (time t), the sub-throttle valve 8 is opened from the closed state to the fully closed position. At this time, the overcharging pressure determination pressure (Pmax) is simultaneously changed from the normal value (Pmax2) to the changed value (Pmax1), and this is continued for a predetermined time.

At this time, the turbine pre-pressure rises and changes with the opening operation of the sub-throttle valve 8. On the contrary,
As the intake air amount increases with the opening of the sub-throttle valve 8, the intake pressure increases gradually, and the pressure upstream of the sub-throttle valve gradually decreases, and the pressure in the intake manifold also gradually increases. And
Thereafter, it rises and changes with the rise of the turbine front pressure. In this case, the intake pressure should gradually converge to the target boost pressure by controlling the opening degree of the waste gate valve 11, but the deviation between the intake pressure and the target boost pressure when the sub-throttle valve 8 is fully opened is relatively small. Since the control constant of the feedback control is large, the intake pressure overshoots and the overcharging pressure determination pressure (Pm
ax) may exceed the normal value (Pmax2).

Here, the intake pressure should normally be the normal value (Pm
ax2), the fuel cut should be executed to reduce the intake pressure urgently.In this embodiment, the overcharging pressure determination pressure is set to (Pm
Since ax2) has been changed to (Pmax1), fuel cut is not executed unless the intake pressure exceeds this changed value (Pmax1). Thus, the sub throttle valve 8 is opened → closed →
When the intake air pressure is temporarily increased abnormally in the case of opening and operating, by not intentionally performing the fuel cut, the acceleration shock due to the torque reduction again after the elimination of the slip state is prevented, thereby improving the Drivability is ensured. It should be noted that such an excessive increase in the intake pressure is a temporary phenomenon, and there is no problem in protecting the engine as described above.

After the elapse of the predetermined time, the overcharging pressure determination pressure is set again from (Pmax1) to (Pmax2), and the engine is controlled in the normal operation state. Therefore, in this state, when the intake pressure exceeds the normal value (Pmax2), the engine protection action by the fuel cut is immediately executed, and the reliability of the engine is reliably ensured. .

The basic concept of the engine control in this embodiment has been described above. Further, the flow charts shown in FIGS.
This control will be described in detail with reference to FIG.

First, for the sake of convenience, the slip control will be described with reference to FIG.
After the control is started, a slip ratio (RR / RF) is obtained from the rear wheel speed RR and the front wheel speed RF of the vehicle, and the slip ratio (RR / RF) is compared with an allowable value, for example, 1.2 to determine whether or not a slip has occurred (step S1). S61). If (RR / RF) ≧ 1.2, it is determined that a slip has occurred, a slip control flag is set (step S62), and the opening (TVOn) of the sub-throttle valve 8 is changed to the previous opening (TVOn− closes the subsidiary throttle valve 8 gradually by reducing by one) predetermined value than (K _1), aim to eliminate the slip by reduction of the engine torque (step S63).

On the other hand, as a result of the determination in step S61,
If (RR / RF) <1.2, it is determined that slip has not occurred, or even if it has occurred, it has been already resolved. In this case, the slip control flag is cleared (step S64). The sub-throttle valve 8 is fully opened to increase the intake pressure (step S6).
5).

Next, with reference to FIGS. 3 and 4, control on the engine side related to slip control will be described. After the control is started, first, in step S1, the target supercharging pressure corresponding to the current operating state is determined. (Pa) and the current actual boost pressure (P
b) (steps S1 and S
2).

Next, it is determined flag F ₁ indicating that the slip control (Step S3). It should be noted that when the flag F ₁ is ₁ , it indicates that the slip control is being performed, and when it is 0, it indicates that the non-slip control is being performed. Accordingly, since the slip control is not performed at first and the flag F ₁ = 0, it is determined in step S10 whether the slip control is being performed. If the slip control is started, the flag F ₁ = 1.
Is set (step S11), and if the slip control is not yet performed, the supercharging pressure determination pressure (Pmax) is set to the normal value in step S12.
(Pmax2), and then proceeds to the boost pressure feedback control shown in FIG.

That is, first, in step S21, the target supercharging pressure (Pa) is compared with the actual supercharging pressure (Pb), and the actual supercharging pressure (P
If b) is high, the current feedback control value (DFB) is reduced by a constant value (K) to reduce the supercharging pressure, and this is set as a new feedback control value (step S2).
3) Conversely, when the actual supercharging pressure (Pb) is low, a constant value (K) is added to the current feedback control value (DFB) to increase the supercharging pressure, and this is set as a new feedback control value. (Step S22). Next, in step S24, the duty ratio (Dut) of the control valve 13 is set.
y) to the base value (Db) and the feedback control value (DF
B) is added to make the final duty ratio. As a result, the intake pressure is constantly controlled to converge to the target boost pressure.

Further, in step S25, the actual supercharging pressure (Pb) is compared with the overcharging pressure judgment pressure (Pmax).
If (Pb ≧ Pmax), the fuel cut is executed to protect the engine, and the intake pressure is reduced urgently (step S26). Thereby, the reliability of the engine is ensured.

On the other hand, it is started slip control, if it is determined that the flag F ₁ = 1 at step S3, a determination is made as to flag F ₃ showing the opening state of the sub-throttle valve 8 in step S4. This flag F
₃ indicates a fully open state when it is 1, and indicates a state other than fully open when it is 0. Here, in the state where the slip control is being performed, the sub-throttle valve 8 is set to the closed state, that is, the flag F ₃ = 0. It is determined whether the difference between the current opening (TVOn) and the fully opened opening (TVOn-1) is equal to or greater than a predetermined value α.

Immediately after the start of the slip control, the sub-throttle valve 8 is in the closed state and will not be opened. Therefore, the flow directly goes to the step S21 to perform the feedback control of the supercharging pressure and the current control. The control for preventing abnormal increase in the intake pressure based on the overcharging pressure determination pressure (Pmax = Pmax2) is continued until the sub-throttle valve 8 is opened.

On the other hand, when the slip control is completed and the sub-throttle valve 8 starts to open from its closed state (that is, in step S5, (TVOn)-(TVOn-1) ≧
If it is determined that the alpha), first determines a flag F ₂ in step S6. Incidentally, the flag F ₂ is a view illustrating the opening operation of the sub-throttle valve 8, the flag F ₂ = 1
Indicates the start of the opening operation, and the flag F ₂ = 0 indicates other states. Accordingly, since the flag F ₂ = 0 at the beginning of the opening operation, the flag F ₂ = 1 is first set in step S7, and the overcharging pressure determination pressure (Pmax) is changed from the above-described normal value (Pmax2) to the changed value (Pmax2). Pmax1), and at the same time, a timer (T) is set in step S9,
Fuel cut control is performed based on the changed value (Pmax1) (steps S25 and S26).

The fuel cut control based on the changed value (Pmax1) is continued until the above-mentioned predetermined time has elapsed even after the sub-throttle valve 8 is fully opened (step S).
13-15) is, once the flag F ₃ at the time when the sub-throttle valve 8 is fully opened is set to 1 (step S16), and thereafter is avoided determination in step S5. Then, the predetermined time T has elapsed (T = 0) Then (step S13), and the flags F _1, F _2, F ₃ and to reset each (step S17～19), again over boost pressure determined pressure (Pmax) Is set to return to the normal value (Pmax2), and thereafter, the fuel cut control based on this normal value (Pmax2) is performed.

As described above, after the slip control is completed,
By setting the overcharging pressure determination pressure (Pmax) higher than the normal value for a predetermined period of time, unnecessary execution of the fuel cut during this period is prevented, and the occurrence of an excessive acceleration shock is prevented. At the same time, during normal operation, the protection of the engine by the fuel cut is properly executed and its reliability is ensured.

Second Embodiment Next, a description will be given of an engine control apparatus according to an embodiment of the present invention as set forth in claims 1 and 3 of the present application. When the sub-throttle valve 8 is opened from the closed state immediately after the end of the operation, the overcharging pressure determination pressure is changed to be set higher than usual for a predetermined time to execute the emergency reduction action of the engine torque due to the fuel cut. In contrast to the above, the occurrence of an unnecessarily high acceleration shock is prevented, as shown in FIG.
ax) keeps this constant, and instead converts it to the target boost pressure (P
a) is changed and set to (Pa−K ₂ ) which is lower by a predetermined value (K ₂ ) than the normal target supercharging pressure (Pa) for the predetermined time.

By doing so, as described above, the feedback control constant of the intake manifold pressure immediately after the opening operation of the sub-throttle valve 8 becomes smaller than when the target supercharging pressure is set to the normal value (Pa). That is, since the overshoot is suppressed, even if the overcharging pressure determination pressure (Pmax) is set to be the same as the normal time, the pressure in the intake manifold exceeds the overcharging pressure determination pressure (Pmax). Therefore, the occurrence of an acceleration shock due to unnecessary fuel cut can be avoided beforehand.

Here, as can be seen by referring to the flowcharts of FIGS. 7 and 8, the basic flow of engine control immediately after the end of the slip control in this embodiment is the first flow described above.
This is the same as that of the embodiment, except that the target boost pressure is changed from (Pa) to (Pa−K ₂ ) for a predetermined time after the slip control ends and the sub-throttle valve 8 is opened.
(Step S38), and in other states, the target boost pressure is always set to the normal value (Pa) (Steps S42 and S50). The rest is the case of the first embodiment. The description is omitted because it is the same as. Therefore, also in this embodiment, it is possible to avoid the occurrence of the acceleration shock due to the unnecessary fuel cut, thereby improving the operability, and to ensure the appropriate protection of the engine during the normal operation. It is.

[Brief description of the drawings]

FIG. 1A is a system diagram of an engine including a control device according to a first embodiment of the present invention.

FIG. 1B is a functional block diagram of the engine control device of the present invention.

FIG. 2 is a time chart showing a control characteristic of intake pressure in an engine control device shown in FIG. 1A.

FIG. 3 is a flowchart for controlling intake pressure in the engine control device shown in FIG. 1A.

FIG. 4 is a flowchart for controlling intake pressure in the engine control device shown in FIG. 1A.

FIG. 5 is a flowchart for slip control in the engine control device shown in FIG. 1A.

FIG. 6 is a time chart showing a control characteristic of intake pressure in an engine control device according to a second embodiment of the present invention.

FIG. 7 is a flowchart for controlling intake pressure in an engine control device according to a second embodiment of the present invention.

FIG. 8 is a flowchart for controlling intake pressure in an engine control apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

1 is an engine, 2 is an intake passage, 3 is an exhaust passage, 4 is an exhaust turbocharger, 5 is a turbine, 6 is a blower, 7 is a main throttle valve, 8 is a sub throttle valve, 9 is an injector, and 10 is an injector. Surge tank, 11 is a waste gate valve, 12 is an actuator, 13 is a control valve, 14 is a supercharging pressure introducing pipe, 15 is an atmospheric pressure introducing pipe,
Reference numeral 20 denotes an engine control unit, 21 denotes a throttle opening sensor, 22 denotes an actuator, 23 denotes a boost sensor, and 25 denotes a slip control unit.

Continuation of the front page (56) References JP-A-61-157728 (JP, A) JP-A-2-125936 (JP, A) JP-A-1-104945 (JP, A) Jpn. , U) JP 62-9723 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/10 315 F02D 9/02 361 F02D 41/02 301

Claims (3)

(57) [Claims] A main throttle valve mechanically connected to an accelerator pedal and a sub-throttle valve electrically controlled to open and close according to a running state of a vehicle are arranged in series in an intake passage of the engine. An intake turbocharger upstream of the main throttle valve and the subthrottle valve, and an intake pressure control means for feedback controlling the intake pressure to a target value corresponding to the opening of the main throttle valve; A control device for the engine, comprising: intake pressure limiting means for limiting a rise change of the intake pressure, wherein the operation of the intake pressure limiting means is performed for a predetermined time when the sub-throttle valve is opened from a closed state. An engine control device characterized by limiting. 2. The fuel supply system according to claim 1, wherein the intake pressure limiting means limits fuel supply to the engine when the intake pressure becomes equal to or higher than a predetermined value, and the main throttle valve has a predetermined opening degree or more. And a control means for restricting the operation of the fuel supply restricting means for a predetermined time when the opening operation is detected from the closed state of the sub-throttle valve. 3. The intake pressure limiting means according to claim 1, wherein the intake pressure limiting means sets the target value for a predetermined time when the main throttle valve is at a predetermined opening degree or more and an opening operation is detected from a closed state of the sub throttle valve. An engine control device comprising a correction means for correcting the pressure in a decreasing direction.