JPH02146223A - Control device for engine with super-charger - Google Patents

Abstract

PURPOSE:To enhance running stability by permitting change-over to be freely made between a first super-charging condition which enhances super-charging efficiency in a low flow rate operating range and a second super-charging condition which enhances super-charging efficiency in a high flow rate operating range, and thereby changing the switch-over condition for super-charging when a stable operating condition is required. CONSTITUTION:In an engine E equipped with No.1 turbo super-charger 1 for a low flow rate range and No.2 turbo super-charger 2 exclusively for a high flow rate range, the operating condition of the super-chargers is made to be capable of being switched between a first super-charging condition which enhances super-charging efficiency in a low flow rate operating range only with No.1 super-charger 1 operated and a second super-charging condition which enhances super-charging efficiency in a high flow rate operating range with both of No.1 and No.2 super-charger 1 and 2 operated. A control unit 50 controlling the aforesaid switch-over is provided with a detecting means 52 which detects a vehicle condition requiring a stable operation with the output signal of a steering sensor 55 inputted. When the condition requiring the stable condition is detected, a switch-over condition between the first and second super-charging conditions is made to be changed by a switch-over condition changing means 53.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a first supercharging state in which the operating state of a supercharger increases supercharging efficiency in a low-flow operating region and a high-flow operating region. The present invention relates to a control device for a supercharged engine that can be switched to a second supercharging state that increases supercharging efficiency.

[Conventional technology]

Conventionally, various supercharged engines are known in which the operating state of a supercharger is switched between a low flow rate operation region and a high flow rate operation fnIti to increase supercharging efficiency in each region. For example, in the engine shown in Japanese Patent Application Laid-open No. 59-160022, a plurality of turbo superchargers are provided, and some of the turbo superchargers are designated as high-speed range dedicated turbo superchargers that supercharge only in the engine high-speed range. On the other hand, the other turbocharger is a low-speed operating turbocharger that operates at least in the low engine speed range, and an exhaust cut valve is installed in the exhaust passage connected to the high-speed range turbocharger. By opening and closing according to the operating conditions, in the low speed range, the exhaust gas supply to the high speed range turbocharger is cut off and the exhaust is concentratedly sent to other turbochargers, and in the high speed range, this turbo The exhaust gas is supplied to the supercharger.

Also, in the engine disclosed in Japanese Utility Model Application Publication No. 60-178329, depending on the operating condition, there are two modes: a state in which exhaust gas is concentratedly sent to one turbo supercharger, and a state in which exhaust gas is distributed in a distributed manner to each turbo supercharger. The exhaust system is now switched to

According to these devices, the operating region with a low flow gap (low speed region)
In this case, supercharging efficiency can be increased by operating only a turbo supercharger whose capacity etc. are set to suit this region. In a high-flow operation region (high-speed region), the supercharging efficiency is increased by the operation of another turbo supercharger, so that the supercharging efficiency can be increased over a wide operating region.

(Problems to be Solved by the Invention) In this type of supercharged engine, a first supercharging state that increases supercharging efficiency in a low flow rate operating region (for example, only a turbo supercharger for a low speed region is operated) The second supercharging state (for example, a state in which each turbocharger is operated individually) that increases supercharging efficiency in the high-flow operation region is adjusted according to the operating state so that it is advantageous for supercharging efficiency. It is possible to switch at a specific switching point (for example, a predetermined intake amount or a predetermined rotational speed).

By the way, depending on the driving condition of the vehicle, stable driving conditions may be required rather than improving engine output. For example, when driving on slippery roads such as snowy roads, stable driving conditions with moderately suppressed engine output may be required. The driving conditions are desirable, and it is also desirable to avoid sudden changes in engine torque during cornering. When in such a stability request state, simply switching the supercharging state at the above-mentioned specific switching point in the same way as when the output is required is insufficient, for example, when driving on a slippery road surface. Problems remained in that the engine torque was increased unnecessarily or the supercharging state was switched during cornering and the engine torque suddenly changed.

In view of the above-mentioned circumstances, the present invention has been developed to adjust engine output and torque fluctuations to meet the demands of the vehicle by adjusting the operating state of the supercharger accordingly when the vehicle is in a stable driving state. The present invention provides a control device for a supercharged engine that can be adjusted.

[Means to solve the problem]

In order to achieve the above-mentioned objects, the present invention has two operating states: a first supercharging state that increases supercharging efficiency in the low-flow operation region where the intake air amount is small, and a high-flow operation region where the intake air amount is large. In a supercharged engine that can be switched to a second supercharging state that increases supercharging efficiency in an operating region, the supercharger operating state is set to the first supercharging state in the low-flow operating region. A supercharging opening control means for switching at a predetermined switching point so as to enter the second supercharging state in the island flow m side operating region, a detecting means for detecting a stable required state of the vehicle operating state, and a detecting means for detecting a stable state of the vehicle operating state; Based on the detection by the means, when the stability required state is reached, the switching conditions between the first supercharging state and the second supercharging state are changed (for example, prohibiting or limiting switching or changing the switching point). (for changing the switching conditions, etc.).

[Effect]

According to the above configuration, when the vehicle is in a state where stability is required such as when driving on a slippery road surface or when cornering, effects such as suppressing engine output or suppressing sudden changes in engine torque can be obtained.

(Example) An example of the present invention will be described based on the drawings. FIG. 1 shows the overall structure of a supercharged engine according to an embodiment of the present invention. This supercharged engine is equipped with a first turbo supercharger 11.1 for the low flow region and a second turbo supercharger 2 exclusively for the island flow M region, with respect to the engine E. It is possible to switch between a first supercharging state in which only the first turbo supercharger 1 is operated and a second supercharging state in which at least the second turbo supercharger 2 is operated, and in the example shown in the figure, the first turbo supercharger 1 It is possible to switch between a state in which only one turbocharger is operated and a state in which both turbochargers 1 and 2 are operated. Each of the turbochargers 1.2 has a turbine 1a, 2a driven by exhaust gas,
It includes compressors Ib and 2b that supercharge intake air by rotating in conjunction with the turbines 1a and 2a.

The capacity of the first turbocharger 1 is set so that the supercharging efficiency is high in an operating region on the relatively low flow rate side.

In addition, the second turbo supercharging 812 is set in a conventional manner so as to compensate for a decrease in supercharging efficiency due to insufficient capacity of the first turbo supercharger 1 in the BR amount side operating region. Therefore, in the first supercharging state in which only the first turbo supercharging iron 1 is operated, the supercharging efficiency in the low flow rate side operation region is increased, and both turbo supercharging e
In the second supercharging state where both the 111°2 and 111°2 are operated, the supercharging efficiency in the high flow rate operation region is enhanced.

The exhaust passage 3 of the engine E is the first. It is divided into two second exhaust passages 3a and 3b, respectively for each turbine 1a and 2.
a, and both exhaust passages 3a, 3b join together on the downstream side of each turbine 1a, 2a. Further, both the exhaust passages 3a are provided on the upstream side of each turbine 1a, 2a.
, 3b are communicated through a communication path 4.

A second exhaust passage 3b that guides exhaust gas to the turbine 2a of the second turbocharger 2 includes a second exhaust passage 3b on the downstream side of the communication passage 4.
An exhaust cut valve 5 is provided that opens and closes the exhaust passage 3b to cut off and allow exhaust gas to flow to and from the turbine 2a. Therefore, when the exhaust cut valve 5 is closed, the first
In addition to the exhaust gas discharged to the exhaust passage 3a, the second exhaust passage 3
The exhaust gas discharged to b is also connected to the turbine 1 of the first turbocharger 1.
When only the first turbocharging R1 is operated and the exhaust cut valve 5 is opened, the exhaust gas discharged into both exhaust passages 3a and 3b is guided to each turbine and engine 1.
a, 2a, both turbochargers 1.2
is now activated. The exhaust cut valve 5 is opened and closed by an actuator 6.

Also, before the exhaust cut valve 5 is opened, a small amount of exhaust is
In order to pre-rotate the second turbocharger 2 by sending it to the turbine 2a of the turbocharger 2, the communication path 4 and the turbine 2a
A small-diameter exhaust leak passage 7 that bypasses the exhaust cut valve 5 is provided between the exhaust gas and the inlet side. This exhaust leak passage 7 is provided with an exhaust leak valve 8 that opens and closes this passage 7 depending on the operating state.
are opened and closed by actuator 9.

Further, a waste gate passage 10 that bypasses each turbine 1 a, 2 a is provided between the upstream part and the downstream part of each turbine 1 a, 2 a. A wastegate valve 11 that is opened and closed is interposed. The waste gate passage 10 is provided, for example, as shown in the figure, between the middle of the communication passage 4 and the downstream exhaust passage collecting section.

On the other hand, the intake passage 15 of engine E has the first turbo supercharger? ! ! A first intake passage 15a in which the first compressor 1b is disposed, and a second intake passage 15b in which the compressor 2b of the second turbocharger 2 is disposed. The first intake passage 15a and the second intake passage 15b diverge from each other from the intake passage 15 on the upstream side, pass through the compressors 1b and 2b, respectively, and merge downstream from the respective compressors 1b and 2b. An air flow meter 16 for detecting the amount of intake air is provided in the intake passage 15 on the upstream side. Also, 1st. An intercooler 17, a throttle valve 18, a surge tank 19, a fuel injection valve 20, and the like are disposed in the intake passage 15 downstream of the confluence of the second intake passages 15a and 15b.

The second intake passage 15b has a second intake passage located downstream of the compressor 2b and near the point where it joins the first intake passage 15a.
An intake cut valve 21 is provided that blocks the intake passage 15b.
It is opened and closed by.

Furthermore, upstream of the intake cut valve 21, the compressor 2b
An intake relief passage 23 is provided that communicates the second intake passage 15b on the downstream side with the intake passage 15 on the upstream side, and this intake relief passage 23 is provided with a relief valve 24 that is opened and closed by an actuator 25.

Each of the actuators 6.9.12.22.25 of the exhaust cut valve 5, exhaust leak valve 8, waste gate valve 11, intake cut valve 21 and relief valve 24 is constituted by a diaphragm device, and the drive and control system for these is constituted by a diaphragm device. is as follows.

The actuator 6 of the exhaust cut valve 5 is connected to a three-way 'Fi magnetic valve 32 via a passage 31. The three-way solenoid valve 32 switches between communicating the actuator 6 with the atmosphere and communicating with the negative pressure passage 33 in response to a signal from the control unit 50. The actuator 6 responds to this switching of the communication state.
As a result of this operation, the exhaust cut valve 5 is switched between a closed state and an open state. The negative pressure passage 33 communicates with a vacuum tank 34, and the vacuum tank 34 stores negative pressure introduced from the intake passage 15 downstream of the throttle valve 18 via a check valve 35.

The actuator 9 of the exhaust leak valve 8 is connected to the compressor 1
A supercharging pressure passage 36 communicating with the first intake passage 15a downstream of b
It is connected to the. Then, when the supercharging pressure introduced from the passage 36 to the actuator 9 exceeds a predetermined value, the exhaust leak valve 8 is closed.

The actuator 12 of the waste gate valve 11 is also connected to the boost pressure passage 36. Then, when the supercharging pressure introduced into the actuator 12 reaches a predetermined maximum allowable supercharging pressure, the waste gate valve 11 is closed.

The actuator 22 of the intake cut valve 21 is connected to a switching valve 38 via a passage 37. This switching valve 38 operates according to the pressure balance of each pressure introduced from the first intake passage 15a and the second intake passage 15b through passages 39 and 40 in the vicinity of the intake cut valve 21. When the differential pressure between the two pressures is greater than a predetermined value, the actuator 22 is communicated with the atmosphere to close the intake cut valve 21, and when the differential pressure is smaller than the predetermined value, the actuator 22 is communicated with the negative pressure passage 41. The intake cut valve 21 is opened by communicating with the intake cut valve 21. Therefore, when the exhaust cut valve 5 is opened and the second turbo supercharging 2 is operated, the pressure inside the second intake passage 15b is reduced to the first intake passage 15a.
When the pressure rises sufficiently close to the internal pressure, the intake cut valve 21 is opened and the supercharged air from the second intake passage 15b is sent to the engine E. The negative pressure passage 41 communicates with the vacuum tank 34.

The actuator 25 of the relief valve 24 is connected to a three-way solenoid valve 43 via a passage 42 .

The three-way solenoid valve 43 connects the actuator 25 to the negative pressure passage 44 in response to a signal from the control unit 50.
It switches between a state in which it communicates with the atmosphere and a state in which it communicates with the atmosphere.

Then, the relief valve 24 is switched between the open state and the closed state by operating the actuator 25 in response to the switching of the communication state. The negative pressure passage 44 communicates with the vacuum tank 34.

The control unit 50 is configured to operate only the first turbo supercharger 1 in a low-flow operating state after a predetermined switching point, and to operate both turbo superchargers 1.2 in a high-flow operating state. control means 51 for controlling the supercharger operating state;
and detection means 52 for detecting the stability required state in both operating states.
and a switching condition changing means 53 for changing the switching condition between the first supercharging state and the second supercharging state when the stability request state is reached based on the detection by the detecting means 52. Contains. The control means 51 controls the exhaust cutoff valve at a line L4 or L3 shown in FIG. The three-way ff11m valve 32.4 is configured to open and close the relief valve 24 in a certain relationship with the relief valve 32.4.
It controls 3. Further, in this embodiment, the detection means 52 checks whether the steering wheel angle is large during cornering based on the steering wheel angle detection signal from the steering angle sensor 55, and also uses a changeover switch 56 for switching between normal mode and snow mode. Based on the signal from the vehicle, it is detected whether the road surface the vehicle is traveling on is a low-μ road that is prone to slipping, such as a snowy road. The changing means 53 limits the supercharging state switching or changes the switching point based on the detection by the detecting means 52. The changeover switch 56 is provided at the driver's seat and is operated at the driver's discretion. However, even if such a changeover switch 56 is not provided,
As described later, it is possible to detect whether the road is a low μ road or not.

Figure 2 shows the switching characteristics of the exhaust cut valve 5, the exhaust leak valve 8, the waste gate valve 11, and the relief valve 24, with the engine speed on the horizontal axis and the engine load on the vertical axis. . Ll in the diagram is the first set intake air amount Q1
and the first setting rotation speed R1, L2 is the relief valve opening line specified by the second setting intake IQ2 and the second setting rotation speed R2, and L3 is the third intake setting Q3. The exhaust cut valve close line is specified by the third set rotation speed R3, and L4 is the exhaust cut valve open line specified by the fourth set intake air amount Q4 and the fourth set rotation speed R4.

Based on this figure, the operation settings of the above multi-valve are explained as follows.
When the operating state shifts from the low flow rate (low rotation) side to the high flow rate (high rotation) side, the exhaust cut valve 5 is closed until it reaches the exhaust cut valve opening line L4, and is opened when it crosses this line L4. When switching from the high outflow side to the low outflow side, the open state is switched to the closed state at the exhaust cut valve closing line L3, which has an appropriate hysteresis with respect to the exhaust cut valve inter-valve line L4. . Therefore, the area on the low flow/low rotation side of the line L4 or L3 is the area of the first supercharging state where only the first turbo supercharging 111 is operated (hereinafter referred to as the P area); Alternatively, the region on the high flow rate and high rotation side of L3 is substantially the second supercharging state region where both turbo superchargers 1.2 are operated (hereinafter referred to as
(referred to as the P+S region).

The exhaust leak valve 8 is set by a spring (4i) of the actuator 9 so that the opening/closing switching line is set by the spring (4i) of the actuator 9 so that the exhaust leak valve 8 switches from the open state to the open state at a certain level 1ffi lower than the exhaust cut valve open line L4 and the exhaust cut valve open line L3. This is done by exhaust cut valve 5.
By sending the middle exhaust gas to the turbine 2a of the second turbo supercharger 2 to pre-rotate the second turbo supercharger 2 before the switch is switched to the open state, the second turbo when the transition to the P+8 region This is to improve the responsiveness of the operation of the supercharger 2.

When the operating state shifts from the low flow rate (low rotation) side to the high flow rate (high rotation) side, the relief valve 24 opens the exhaust cut valve line on the high flow rate side than the exhaust leak valve opening/closing line, and opens the exhaust cut valve line on the high flow side than the exhaust leak valve opening/closing line. The relief valve is set on the low rotation side, with the closing line L2 as the border, it is open until it reaches this line 2, and when it crosses this line L2, it is switched to the closed state, and from the high flow side to the low flow side. At the time of transition, the relief valve close line L
The closed state is switched to the open state at the relief valve open line L1, which has an appropriate hysteresis with respect to 2. The reason why this is done is that during the pre-rotation of the second turbocharger 2 until it approaches the P+S region to some extent, the air in the second intake passage 15b is relieved, thereby reducing the pressure increase in the passage. To avoid a temperature rise, and on the other hand, when the temperature approaches the P+S region to some extent, relief is stopped to increase the pressure in the second intake passage 15b and to promote an increase in the rotational speed of the second turbocharger 2. It is. That is, when the relief valve 24 is closed during pre-rotation and the intake cut valve 21 is also closed, the second intake passage 15b is in a dead end state, and the compressor 2
Even if b rotates, air is not fed, so the load on the second turbo supercharger 2 decreases, and this causes the second turbo supercharging! j
The effect of promoting the increase in the rotation speed of the engine 12 can be obtained. In addition, P
After one line of transition to the +8 region, the differential pressure between the first intake passage 15a and the second intake passage 15b becomes smaller, and the intake cut valve 21 is opened, so that the second intake passage 15b is opened.
The supercharging air from the relief valve 24 is also sent to the engine.
is kept closed.

Further, the wastegate valve 11 has an opening/closing switching line set by a spring load of the actuator 12 so as to be opened as soon as the maximum allowable supercharging pressure is reached.

The first to fourth intake settings fiQ1 to Q4 and the first to fourth set rotational speeds R1 that define the lines 1 to L4 in FIG.
~R4, each basic IQ1o -Q
4o and Rlo-R4o are stored in a memory (not shown) within the control unit 50. According to the basic values, the exhaust cut valve line L4 is set so as to obtain the switching point of the supercharger operating state that is most advantageous for supercharging efficiency, such as during acceleration when the intake air amount (rotation speed) gradually increases. The exhaust cut valve closing line L3 is set to have an appropriate hysteresis with respect to the line L4. In addition, in order to effectively exhibit the function of the relief valve 24 as described above, the relief valve close line L2 and the relief valve open line 1 are set to have an appropriate intake air amount difference and rotational speed difference with respect to the lines L4 and L3. It is set with. These lines 1 to L4 are set with the intake port related to the engine speed and load as the main parameters, but in this embodiment, it is not preferable for the exhaust cut valve 5 etc. to switch at too high a speed. Therefore, engine speed is also used as a parameter.

FIG. 3 is a flowchart showing the control of the exhaust cut valve 5 and the relief valve 24 by the control unit 50. In this flow, when starting, the system is first initialized in step S1, and then air intake is performed in step S2! The detected values of IQ and engine speed R are sent to the air flow meter 16 and the engine speed sensor 54.
Enter each from Subsequently, in step S3, the opening/closing points of the exhaust cut valve 5 and the relief valve 24 are set at the first to fourth set intake air basic values Q1o to Q4o, which are lines 1 to 4) in FIG. The basic values R1o to R4o of the first to fourth set rotational speeds are read from the memory.

Next, in step S4, the steering angle α is detected based on the signal from the steering angle sensor 55, and in step S5, the steering angle α is set to a predetermined value α.
Check whether it is greater than 0. Then, in the case of the stability request state where the determination in step S5 is YES, the exhaust gas cut valve 5 and the relief valve 24 are basically maintained in the previous state. However, in the example shown in the figure, in order to avoid a situation where the relief valve 24 remains closed in the P region and the temperature inside the second intake passage 15b becomes excessively high, the flag F (described later) is set to 2 or 3. Sometimes, this flag F is set to 4 and the exhaust cut valve 5 is opened (steps 86 to 89).
), the process returns to step $2; otherwise, the process directly returns to step S2.

If the determination in step S5 is NO, further step S5
A slip condition is detected based on the signal from the changeover switch 56 at η, and it is checked in step S11 whether the road surface condition is prone to slip. If the changeover switch 56 is not provided, the slip state may be determined by checking the vehicle speed and engine rotational speed, for example, as shown in FIG. In other words, if the line in FIG. 4 which shows the correspondence between vehicle speed and engine rotational speed when non-slip is used as a reference, if the engine rotational speed is higher than the above line, it means that the vehicle is in a slipping state.

If the determination in step S11 is No, the basic value Qlo
-Q4o, Rlo to R4o are set as the final first to fourth set intake air ff1Q1 to Q4 and first to fourth set rotational speeds N1 to N4 (step 512). on the other hand,
When this determination is YES in the stability request state, the above basic (IIIQl) is performed in step S13.

- Q4o, R1o to R4o are increased or decreased to obtain the final first to fourth set intake air ff1Q1 to Q4 and first to fourth set rotational speeds R1 to R4. At this time, it is desirable that the set intake air amount and the set rotational speed be increased or decreased as shown in FIG. 5 in accordance with the vehicle speed detected by a vehicle speed sensor (not shown). That is, the set intake air amount Qn (01 to Q4)
Correction value ΔQ and set rotation speed Rn (R1-R
The correction value ΔR for 4) is determined according to the vehicle speed V, and the basic Q
f! Qno (Qlo”Q4o >, Rno (R
lo-R4o) by the correction amount ΔQ, ΔR (
Qno + ΔQ, Rno + ΔR) are set intake width Qn and set rotation speed Rn, and on the vehicle speed side higher than the predetermined vehicle speed Va, set values (Qno - ΔQ, RnQ - ΔR) smaller than the basic value Qno and Rno by the correction amounts ΔQ and ΔR. Setting intake ff
Let 1Qn and the set rotational speed be Rn.

After the setting in step S12 or step S13, processing as the control means 51 in FIG. 1 is performed in steps S14 and thereafter. In this process, first, it is determined whether the flag F is 1 (step 514), and if the determination is No.
Determination of whether the flag F is 2m (m is an integer) in the case of (step 515), and flag F if the determination is YES
By determining whether or not is 2 (step 516), the value of the flag F is checked.

The above flag F distinguishes to what region in Fig. 2 the operating state specified by the intake IQ and engine speed R belongs, and is set to any value from 1 to 4. Take. If it is F-1, the relief valve open area where the relief valve 24 is opened in the Pa range where the exhaust cut valve 5 is quiet, that is, the line 2 (during acceleration) or the inline Ll (during deceleration)
This indicates that the engine is in a lower flow rate and lower rotation range. F=2
Or if F=3, the exhaust cut valve 5 is closed Pf!
This indicates that the relief valve 24 is in the relief valve closed region where it is quiet among the four regions, and when the relief valve shifts from the relief valve open region to this region, it becomes F-2, and the transition from the P+S region to this region. If so, it becomes F-3. This Pa
The boundary between the relief valve closed area and the relief valve open area within the area is the intrusion L2 in the case of transition from the relief valve open area.
, in the case of transition to the relief valve open region, line L1 becomes line L1, and the boundary between the relief valve closed region in this P region and the P+S region is line L1 in the case of transition from the p+5fti region.
31. In the case of transition to the P+8 area, the line becomes line L4.

Further, F-4 indicates that the exhaust cut valve 5 is in the open P+S region, that is, in the region on the higher flow rate and higher rotation side than line L4 (during acceleration) or line L3 (during deceleration).

If the determination in step S14 is YES (F-1), it means that the previous operating state was in the intake relief valve open region of the P region.

In this case, based on the determination of whether the intake air ff1Q is larger than the second set intake air ff1Q2 (step Sv) and the determination of whether the engine rotation speed R is larger than the second set rotation speed R2 (step 518), the following steps are performed. Perform processing like this. That is, if the determinations in steps Sv and S1a are both NO,
Since the operating state is maintained in the relief valve open region, the process returns to step S2 to open the exhaust cut valve 5.
is closed, and the relief valve 24 is kept open. Step Sv
, S18, the operating state has exceeded line 2 in FIG. After closing the valve 24, the process returns to step S2.

If the determination in step 5111 is YES (F-2), it means that the previous operating state was in the relief valve closed region within the P region and after the transition from the relief valve inter-region. . In this case, it is determined whether the intake air 1iQ is higher than the fourth set intake speed Q4 (step 521), and if the determination is NO, it is determined whether the engine speed R is higher than the fourth set speed R4. (Step 522), and if the determination is NO, it is determined whether or not the intake air pressure Q is smaller than the first set intake air 11Q1 (Step 523), and if the determination is Y.
Based on the determination of whether or not the engine rotation speed R in the case of ES is smaller than the first set rotation speed R1 (step 524), the following processing is performed. That is, step S21.82
Both determinations in step S23.2 are NO, and step S23.
If any of the judgments in 324 is No, the operating state is 9.
4211.14, the process returns to step S2 to keep the exhaust cut valve 5 in the locked state and the relief valve 24 in the closed state. Step 821
, 822, the operating state has crossed line L4 in FIG. 5 and then returns to step S2. If the determinations in step S23.824 are both YES, the operating state has shifted to the region between the relief valves on the low flow rate and low rotation side from line 1 in FIG. Step S28
After opening the relief valve 24, the process returns to step S2.

If the determination in step S 1s is No, the result is F-3, which means that the previous operating state was in the relief valve closed region within the P region and after the transition from the P+S region. . In this case, the intake air amount Q is the first set intake air ff1
Determination of whether the engine speed R is smaller than Q1 (step 529), determination of whether the engine rotation speed R is smaller than the first set rotation speed R1 if the determination is YES (step S30), and steps 829 and 330. If either of the determinations is No, it is determined whether the intake air fitQ is larger than the fourth setting intake air ff1Q4 (step 531), and if the judgment is No, the engine rotation speed R is larger than the fourth setting rotation mR4. Based on the determination (step 532), the following processing is performed. That is, if any of the determinations in step S29.830 is No and the determinations in steps S3t and S32 are both No, the operating state is on line L1, L4.
Since it is maintained in the area between
By returning to
Keep 4 closed. If the determinations in steps S29 and 830 are both YES, the operating state is on line L in FIG.
Since the flow has shifted to the area between the relief valves on the low rotation side with a lower flow rate than 1, the process is set to F-1 in step S33, and the relief valve 24 is opened in step 834, and then the process returns to step S2. If the determination is YES in either step S3t or S32, the operating state has exceeded line 4 in FIG.
-4, and in step S3a, the exhaust cut valve 5
After opening, the process returns to step S2.

If the determination in step S+a is No, F=4, which means that the previous operating state was at the above P+5ffi[. In this case, based on the determination of whether the intake IQ is smaller than the ``ff13 setting intake fiQ3 (step 537) and the determination of whether the engine speed R is smaller than the third set rotation speed R3 (step 538), the following steps are performed. In other words, if the determination in either step 837 or 838 is No, the operating state is maintained in the P+S region, and the process returns to step S2 to open the exhaust cut valve 5. , the relief valve 24 is kept closed. If the determinations in steps S37 and S3a are both YES, the operating state has shifted to the Pffi region on the low flow rate and low rotation side from line L3 in FIG. In F
-3, and in step S40, the exhaust cut valve 5
After closing, return to step $2.

According to the control device of this embodiment as described above, step 8
14 to S40 as the control means 51, the exhaust cut valve 5 is closed in the low flow rate and low rotation side region, and substantially only the first turbocharger 1 is operated, and the The supercharging efficiency in the flow m region is increased. When the operating state shifts from the low flow rate side to the high flow rate side, first, when the exhaust leak valve opening/closing line is crossed, the exhaust leak valve 8 is switched from closed to between, and when the line L2 is crossed, the relief valve 24 is switched from closed to closed. When the line L4, which is the switching point of the supercharger operating state, is crossed after the exhaust gas cut valve 5 is switched from open to closed, the exhaust cut valve 5 is switched from open to open. When this state is reached, exhaust gas is sufficiently supplied to the turbine 2a of the second turbocharger 12, so that the second turbocharger 2 is substantially operated in addition to the first turbocharger 1. The supercharging efficiency in the flow area is increased.

When the state is other than the stability request state, such switching of the supercharging state is performed by setting the basic values Q1o - Q4o, R1° to R40, and setting the intake air ff1Q1 to Q4 and the set rotational speed R1 to R4.
By doing this, the supercharging state is switched so that the overall supercharging efficiency is maximized.

On the other hand, in the stability required state where the running road surface is prone to slip, the above-mentioned Q1o to
After setting the set intake air amounts Q1 to Q4 and the set rotation speeds R1 to R4 to values that are increased or decreased by the correction values ΔQ and ΔR than Q4o and Rlo to R4o, steps 814 to 8 are performed.
By performing the 4G processing, the switching point of the supercharging state is shifted to the low flow rate (low rotation) side or the high flow rate (high rotation) side from the switching point that maximizes supercharging efficiency. As a result, the supercharging efficiency is lowered compared to when the stability is not required, and an increase in engine output is suppressed to be advantageous for reducing slip. In this case, if the set intake temperature and set rotational speed are increased or decreased according to the vehicle speed as shown in Figure 5, the P region will be expanded on the low vehicle speed side, and the P + S region will be expanded on the high vehicle speed side. The effect of suppressing the engine output υ1 can be obtained while improving the running performance in the vehicle speed range of .

In addition, when cornering (when the steering angle α becomes larger than the predetermined value αG, where stability is required), regardless of changes in the driving state, except when the relief valve 24 is closed in the PI region, The previous supercharging state is maintained as it is,
Switching of supercharging state is restricted. In other words, during cornering, if the operating state is in the Plft region, only the first turbocharger 1 will remain in operation even if the operating state changes to the high flow rate side, and if the operating state is in the P+S region For example, even if the operating state changes to the low flow rate side, both turbochargers 1 and 2 remain in operation. This reduces the occurrence of torque fluctuations due to switching of the supercharging state during cornering, and improves driving stability.

Note that the # control in response to the determination of the required stable state is not limited to the above embodiment; for example, as a control when the steering angle α is larger than the predetermined value α0, at this time, the supercharging state is unconditionally maintained until then. Control when the vehicle is in a slip-prone state is to set the switching point of the supercharging state to either the low flow rate side or the high flow rate side, regardless of whether the vehicle speed is low or high. Alternatively, it may be possible to switch to one or the other. Further, the determination of the required stable state and the corresponding control may be performed for either the steering angle or the slip state. In addition to this, in vehicles equipped with a constant speed driving device that controls constant speed driving in response to a constant speed driving designation operation, when the vehicle is in a constant speed driving state that requires stability, For example, switching of the supercharging state may be restricted by processing similar to steps 86 to S9 described above.

In addition, the supercharged engine to which the control device of the present invention is applied is not limited to one equipped with a first turbocharger 1 and a second turbocharger 2 as shown in FIG. For example, one that uses an engine-driven supercharger (supercharger) linked to the engine output shaft and a turbo supercharger, and operates only the supercharger in the low flow range and operates the turbo supercharger in the high flow range. But that's fine. Alternatively, for one turbo supercharger, the passage leading to the exhaust gas may be divided into two parts, and the passage can be switched between leading the exhaust from one side and leading the exhaust from both sides. Any device may be used as long as it can be switched between a supercharging state that increases supercharging efficiency in the side operation region and a supercharging state that increases supercharging efficiency in the high flow rate side operation region.

〔Effect of the invention〕

As described above, the present invention changes the operating state of the supercharger into a first supercharging state that increases supercharging efficiency in a low flow rate operating region and a second supercharging state that increases supercharging efficiency in a high flow rate operating region. In supercharging state,
In addition to switching at a predetermined switching point, the switching conditions for the supercharging state are changed as soon as the vehicle operating state reaches a stable state, so basically supercharging efficiency can be increased. While ensuring that the supercharging state is switched properly, the engine output and the like are appropriately adjusted when the above-mentioned stability required state is reached, thereby improving running stability.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the overall structure of a supercharged engine showing one embodiment of the present invention, Fig. 2 is a characteristic diagram showing the operating characteristics of eight valves arranged in the exhaust system and intake system, and Fig. 3 is a flowchart of control by the control unit, Fig. 4 is an explanatory diagram of the relationship when determining a slip state according to the relationship between vehicle speed and engine speed, and Figs. It is a figure which shows the example of a change of rotation speed. E... Engine, 1... First turbo supercharger, 2...
・Second turbo supercharger, 5...Exhaust cut valve, 50...
- Control unit, 51... Control means, 52.
. . . detection means, 53 . . . switching condition changing means. To H',

Claims (1)

[Claims] 1. The operating state of the supercharger is a first supercharging state that increases supercharging efficiency in the low flow rate operating region where the intake air amount is small, and a second supercharging state that increases supercharging efficiency in the high flow rate operating region where the intake air amount is large. In a supercharged engine that can be switched between a supercharging state and a supercharging state, the supercharger operating state is set to the first supercharging state in the low-flow operating region and to the second supercharging state in the high-flow operating region. A supercharger control means that switches to a supercharged state at a predetermined switching point, a detection means that detects a stabilization required state of the vehicle operating state, and based on the detection by this detection means, the stabilization required state is reached. 1. A control device for a supercharged engine, comprising: switching condition changing means for changing switching conditions between the first supercharging state and the second supercharging state when the supercharging state changes.