JPH02136515A - Controller for engine with exhaust turbosupercharger - Google Patents

Abstract

PURPOSE:To make improvements in responsiveness at the time of transition to a supercharging operating state by making a second supercharger prerotatable at a driving range where it is set to a dormant state, in an engine which is provided with a first supercharger normally driven and the second supercharger being driven only at a specified driving range. CONSTITUTION:At a low-speed, low rotation range, an exhaust cut valve 5 is closed, and a first supercharger 1 alone is operated. In this case, when a driving state has shifted to the high flow side from the low flow side, first an exhaust shifting valve 8 is selected to open from close, then a relief valve 24 to open from close as well, and also the exhaust cut valve 5 to open from close in order, respectively. With this operation, a second supercharger 2 is operated, thereby enhancing the extent of supercharging efficiency at the high flow range. In brief, at time of the said transition, in advance of open operation of the exhaust cut valve 5, an exhaust shifting valve 11 is opened where by the second supercharger 2 is made into prerotation, and afterward, the relief valve 24 is closed, thus an increase in rotational frequency of the second supercharger 2 during prerotation is accelerated, and the said transition is smoothly performed with no shock.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust gas pump equipped with a turbo supercharger that operates at least in a low-flow operation region and a turbo-supercharger that operates only in a high-flow operation region. The present invention relates to a control device for a turbocharged engine.

[Conventional technology]

Conventionally, exhaust turbo superchargers have been equipped with a turbo supercharger that operates at least in a low-flow operating region and a turbo supercharger that operates only in a high-flow operating region to increase supercharging efficiency in each region. Various feeder engines are known.

For example, in the engine shown in Japanese Patent Application Laid-Open No. 59160022, a plurality of turbo superchargers are provided, and some of the turbo superchargers are dedicated to high-speed range turbo superchargers that perform supercharging only in the engine high-speed range. , the other turbocharger is at least a low-speed operating turbocharger that operates in the low engine speed range, and in the low-speed range, this turbosupercharger is When the turbocharger is stopped, the exhaust gas is sent intensively to other turbochargers, and in the high-speed range, this turbocharger is overpowered by opening the exhaust passage and intake passage of the turbocharger dedicated to the high-speed range. It is set in the supply operation state.

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. It is now possible to switch to .

According to these devices, the operating region on the low flow rate side (low speed 14
), the supercharging efficiency can be increased by operating only the turbo supercharger whose capacity etc. are set to suit this region. Operation area on the high flow rate side (high speed area)
In this case, the supercharging efficiency is increased by operating another turbo supercharger, and the supercharging efficiency can be increased over a wide operating range.

[Problem to be solved by the invention]

In this type of engine with an exhaust turbo supercharger, it is not possible to simply stop the turbo supercharger for the high flow region by cutting off the exhaust supply to the turbo supercharger for the high flow region in the low flow region. Even if the exhaust gas supply to the turbo supercharger for high flow MIA is started in response to the transition of the operating state to the second turbo supercharger, a delay in operation of the second turbo supercharger occurs, resulting in poor responsiveness. For this reason, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 59-160022, the exhaust passage and intake passage on the high flow rate turbocharger side are closed, and the turbocharger is brought into a supercharging stopped state. By sending a small amount of exhaust gas from the exhaust leakage passage to the turbine of the turbo supercharger for high flow range to pre-rotate this turbo supercharger when In the past, attempts have been made to improve the responsiveness when switching to .

By the way, when pre-rotating the turbo supercharger for high flow range by providing an exhaust leak passage in this way, it is necessary to rotate the turbo supercharger for high flow range until the operating state approaches the switching point to a certain extent to put the turbo supercharger for high flow range into the supercharging operation state. It is desirable to relieve the intake air in the intake passage on the high flow rate region turbocharger side in order to suppress the temperature rise due to the pressure rise in the intake passage on the high flow rate turbocharger side. However, when the above-mentioned switching point approaches, it is better to stop the above-mentioned intake relief, as will be explained in detail later, the pre-rotation of the turbo supercharger for the g flow range is promoted, and the turbo supercharger for the high flow range is The responsiveness of the machine can be further improved.

Therefore, a relief passage is provided to relieve the intake air in the intake passage on the side of the turbo supercharging hoe for high flow range, and the relief passage is provided near the switching point in the operating range where the turbo supercharger for high flow range is pre-rotated. One idea would be to close it. However, in this case, if the operating state is maintained near the above switching point and the pre-rotation state where the relief passage is closed continues for a long time, the rotation speed of the high-flow turbocharger will increase more than necessary. . If the rotational speed of the high flow rate turbocharger becomes too high while the intake passage on the high flow rate turbocharger side is closed,
The temperature of the air around the compressor increases significantly,
A problem arises in which the turbocharger becomes overheated.

In view of the above-mentioned circumstances, the present invention promotes pre-rotation before the high flow rate turbocharger is switched to the supercharging operating state to improve responsiveness at the time of transition to the supercharging operating state, and further, The present invention provides a control device for an engine with an exhaust turbocharger that can reliably prevent overheating during pre-rotation of the turbocharger.

[Means to solve the problem]

In order to achieve the above-mentioned objects, the present invention includes a first turbocharger that operates at least in a low-flow operation region and a second turbocharger dedicated to an island-open operation region. In the side operation region, a second turbo supercharger side exhaust passage that guides exhaust gas to the turbine of the second turbo supercharger and a second turbo supercharger side intake passage that guides intake air from the compressor of the second turbo supercharger to the engine side. The second turbocharger is brought to a supercharging stop state by shutting off the In an engine with an exhaust turbo supercharger in which the second turbo supercharger is switched to the supercharging operating state by opening the intake passage on the feeder side, before the second turbo supercharging is set to the supercharging operating state. an exhaust leakage passage that guides a small amount of exhaust gas to the turbine of the second turbocharger so as to pre-rotate the second turbocharger; and a relief that communicates the compressor outlet side of the second turbocharger with the upstream side of the compressor. a passage, a relief valve that opens and closes the relief passage, and a second
and relief control means for opening the relief valve when the turbocharger enters an overspeed state during pre-rotation.

[Effect]

According to the above configuration, when the operating state approaches the switching point, a small amount of exhaust gas is guided from the exhaust gas leakage passage to the turbine of the second turbo supercharger and the relief valve is closed. The pre-rotation of the turbocharger is promoted, and if the rotational speed of the second turbocharger becomes too high in such a state, the relief valve is opened, thereby increasing the rotational speed of the second turbocharger. can be suppressed.

〔Example〕

Embodiments of the present invention will be described based on the drawings. FIG. 1 shows the overall structure of an exhaust turbocharged engine according to an embodiment of the present invention. This engine with an exhaust turbo supercharger has a first turbo supercharger 1 for low flow stratification and a second turbo supercharger for high flow range! fi2, and can be switched between a state in which only the first turbo supercharger 1 is operated and a state in which both turbo superchargers 1.2 are operated. Each of the turbochargers 11.2 includes a turbine 1a, 2a driven by exhaust gas, a turbine Ia,
It includes compressors Ib and 2b that supercharge intake air by rotating in conjunction with compressor 2a.

The capacity of the first turbocharger Akebono 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 turbocharger 2 is in the first
The capacity etc. are set so as to compensate for a decrease in supercharging efficiency due to insufficient capacity of the turbo supercharger 1 or the like.

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 ia, 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 m1 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 1a.
, 2a, both turbochargers 1.2 are operated. 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 is opened and closed by an 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 la, 2 a, and this waste gate passage 10 is provided with an actuator 12. 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, in the intake passage 15 of the engine E, the first intake passage 15 in which the compressor 1b of the first turbo supercharger 1 is arranged.
a, and a second intake passage 15b in which a compressor 2b of a second turbocharger 1am2 is disposed. The first intake passage 15a and the second intake passage 15b branch from the intake passage 15 on the upstream side, pass through the compressors 1b and 2b, respectively, and join downstream of 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, one surge tank, 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 that blocks the intake passage 15b is provided, and the intake cut valve 21 is opened and closed by an actuator 22.

Furthermore, upstream of the intake cut valve 21, the compressor 2b
A 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 the relief passage 23 is provided with a relief valve 24 that is opened and closed by an actuator 25.

Each actuator 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 each constituted by a diaphragm device, and the drive for these, The control system is as follows.

The actuator 6 of the exhaust cut valve 5 is connected to a three-way solenoid valve 32 via a passage 31. This three-way solenoid valve 3
2 switches the actuator 6 between a state in which it communicates with the atmosphere and a state in which it communicates with the negative pressure passage 33 in response to a signal from the control unit 5°. Then, the exhaust cut valve 5 is switched between the closed state and the open state by operating the actuator 6 in response to this switching of the communication state. Note that the negative pressure passage 33 is connected to the vacuum tank 3.
4, and this vacuum tank 34 is connected to a check valve 35 from the intake passage 15 downstream of the throttle valve 18.
Negative pressure led through is stored.

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 opened.

The actuator 22 of the intake cut valve 21 is connected to the 9th passage 37.
It is connected to the switching valve 38 via. This switching valve 38
is the first intake passage 15a near the intake cut valve 21
The actuator 22 is operated in accordance with the pressure balance between the respective pressures introduced through passages 39 and 40 from the second intake passage 15b and the second intake passage 15b, and when the differential pressure of the repressure is above a predetermined value, the actuator 22 is moved to the atmospheric side. The actuator 22 is communicated with the negative pressure passage 41 to open the intake cut valve 21 when the differential pressure becomes smaller than a predetermined value. Therefore,
When the exhaust cut valve 5 is opened and the second turbocharger 2 is operated, the pressure in 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 includes an air flow meter 1
6 and the engine rotation speed detection signal from the rotation speed sensor 52, a predetermined switching point (line L shown in FIG.
4 or 3), only the first turbo supercharger 1 is operated by closing the exhaust cut valve 5 in a low flow rate operating state, and by opening the exhaust cut valve 5 in a high flow rate operating state. A three-way solenoid valve 32 is controlled to operate both turbochargers 1.2. Furthermore, this control unit 50 controls the three-way solenoid valve 43 to close the relief valve in the vicinity of the switching point in the operating region where the second turbocharging R2 is pre-rotated, while
It includes a relief control means 51 that opens the relief valve 24 when the turbocharger 2 becomes over-rotated during pre-rotation.

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 setting intake temperature Q1
and the first set rotation speed R1, and L2 is the second set intake air ff1Q2 and the second set rotation speed R.
2 is the relief valve closing line specified by 2, L3 is the exhaust cut valve closing line specified by the third set intake amount Q3 and the third set rotation speed R3, and L4 is the fourth set intake IQ4 and the fourth set rotation speed. This is the line between the exhaust cut valves specified by R4. Each of the above set intake air amounts 01 to Q4 and each set rotation speed R1
~R4 are stored in advance in a memory (not shown) in the controller 1 roll unit 50.

Based on this figure, the operation settings of the above eight valves will be explained as follows.
The exhaust cut valve 5 opens when the operating state changes from the low flow rate (low rotation) side to the high flow rate (high rotation) side, and is closed until it reaches line 4, and when it crosses this line L4. When switched to the open state and transitioning from the high flow rate side to the low flow rate side, the open state is switched from the open state to the closed state at the exhaust cut valve closing line L3, which has a moderate hysteresis with respect to the exhaust cut valve inter-valve line L4. . Therefore, the area on the low flow rate and low rotation side from the above line L4 or L3 is the area where only the first turbo supercharging unit 1 is operated (hereinafter referred to as the P area), and the high flow rate and high rotation side from the above line L4 or L3. This region is substantially the region in which both turbochargers 1 and 2 are operated (hereinafter referred to as the P+S region).

The opening/closing switching line of the exhaust leak valve 8 is set by the spring load of the actuator 9 so that the exhaust leak valve 8 switches from the closed state to the open state at a certain lower flow rate side than the exhaust cut valve open line L4 and the exhaust cut valve close line L3. ing. The reason for this is that before the exhaust cut valve 5 is switched to the open state, a small amount of exhaust gas is sent to the turbine 2a of the second turbo supercharger 2 for second turbo supercharging! This is to increase the responsiveness of the operation of the second turbo supercharger 2 when shifting to the P+S region by pre-rotating fi2.

When the operating state transitions from the low flow rate (low rotation) side to the high flow rate (high rotation) side, the relief valve 24 has a lower flow rate and lower rotation speed than the exhaust cut valve inter-valve line L4 on the high flow side than the exhaust leak valve opening/closing line. The relief valve set on the side is opened until it reaches this line L2, and is switched to the closed state when it crosses this line L2, and when transitioning from the high flow rate side to the low flow rate side, Relief valve closing 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 for doing this is 1. During the pre-rotation of the second turbo 1 feeder 2 until it approaches the p+sa region to a certain extent, the air in the second intake passage 15b is relieved to prevent the pressure increase in the passage. 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's for a reason. That is, the relief valve 24 is closed during pre-rotation,
When the intake cut valve 21 is also closed, the second intake passage 15b is at a dead end, and no air is fed even if the compressor 2b rotates, so the load on the second turbocharger 2 decreases. As a result, an effect of promoting an increase in the rotational speed of the second turbo supercharging 2 can be obtained. In addition, P+
After the transition to the S region, the intake cut valve 21 is opened as the differential pressure between the first intake passage 15a and the second intake passage 15b becomes smaller, so that supercharging air from the second intake passage 15b is reduced. is also sent to the engine, but the relief valve 24 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 when the maximum allowable supercharging pressure is reached.

The exhaust cut valve opening line 4 in Fig. 2 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. The above line L4゜L3 is set with the intake air amount related to the engine speed and load as the main parameter, but in this embodiment, it is not preferable for the exhaust cut valve 5 etc. to switch at too high a speed. , engine speed is also used as a parameter.

In addition, when the relief valve closes the line 2, during acceleration when the intake air amount increases, etc., the function of the relief valve 24 as described above allows the second turbo supercharger 2 to
In order to obtain the effect of increasing the rotation speed, the intake air amount difference and rotation speed difference are set to be constant with respect to the exhaust cut valve closing line L4, and the relief valve open line L3 is set to be constant with respect to the relief valve closing line L2. is set with a hysteresis of The relief control means 51 in FIG.
Basically, the relief valve 24 is controlled according to such settings, but if the operating state stays in the P region where the relief valve 24 is closed for a long time, the second turbo supercharging When the machine 2 enters an overspeed state, the relief valve 24 is opened.

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 started, the system is first initialized in step S1, and then, in step S2, the detected values of the intake air @Q and the engine rotation speed R are input from the air flow meter 16 and the rotation speed sensor 52, respectively. Subsequently, in step S3, the first to fourth intake settings ff1, which are the opening/closing switching points (lines 1 to L4 in FIG. 2) of the valve 5 and the relief valve 24, are supplied to the exhaust cup 1.
Q1 to Q4 and the first to fourth set rotational speeds R1 to R4 are read from the memory.

Next, it is determined whether or not the flag F for area identification is 1 (step 84), and if the determination is No, the flag F is 2m (
The value of the flag F is checked by determining whether or not m is an integer (step 85), and if the determination is YES, determining whether the flag F is 2 (step 86).

The above flag F is used to distinguish to what region in Fig. 2 the operating state specified by the intake air amount Q and the engine speed R belongs, and is set to any value from 1 to 4. Take. If F=1, the relief valve 24 is in the relief valve open area in the P area where the exhaust valve 5 is leaping, that is, the lowest flow is lower than line 2 (during acceleration) or line Ll (during deceleration). Indicates that it is in the rotation side area. If F=2 or F=3, this indicates that the exhaust cut valve 5 is in the relief valve closed region where the relief valve 24 is closed within the P region where the exhaust cut valve 5 is closed, and this When moving to this area, F=2, and when moving from the P+S area to this area, it becomes F-3. The boundary between the relief valve closed area within this P area and the relief valve open area is line L2 in the case of transition from the relief valve open area, and line L1 in the case of transition to the relief valve open area. The boundary between the relief valve closing area and the P+S area within the area is
In the case of transition from the P+S area, line L3 is used, and in the case of transition to the P+8 area, line L4 is used. Further, if F=4, it indicates that the exhaust cut valve 5 is in the open P+8 region, that is, in the region on the higher flow rate and higher rotation side than line L4 (during acceleration) or line [3 (during deceleration).

If the determination in step S4 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, it is determined whether the intake air ff1iQ is larger than the second set intake air IQ2 (step 87) and the engine rotation speed R
is larger than the second set rotation speed R2 (step S
8), the following processing is performed. That is, if both determinations in step 87.8a are NO, the operating state is maintained in the relief valve open region, so the exhaust cut valve 5 and the relief valve 24 are returned to the previous state (exhaust cut valve 5 is closed, The process returns to step S2 via step S31 while the relief valve 24 remains open. If the determination is YES in either step 87 or Sa, the operating state has crossed line L2 in FIG. After closing the relief valve 24 in S10, the process returns to step S2 via step S31. Note that step 831 is for clearing a timer T, which will be described later, to O.

If the determination in step S6 is YES (F=2),
This means that the previous operating state was in the relief valve closed region within the P region, and is after the state has shifted from the relief valve open region. In this case, the intake air amount Q is the fourth set intake IQ
4 (step 511), and if the determination is NO, the engine rotation speed R is the fourth set rotation speed R4.
(step 512); if the determination is No, determine whether the intake i1Q is smaller than the first set intake IQI (step 513); and if the determination is YES, the engine rotation. Based on the determination of whether the number R is smaller than the first set rotation speed R1 (step 514), the following processing is performed. That is, the determinations in step S11.812 are both No, and the determination in step Sf3. S14
If any of the judgments is NO, the operating state is 5121.
1.14, and in this case, in step S32, an over-speed prevention routine, which will be described in detail later, is executed, and then the process returns to step S2. Step S11. S
If the determination is YES in either f2, the operating state has crossed line L4 in FIG.
16, the exhaust cut valve 5 is opened, and the relief valve 24 is opened.
If it is in the open state, it also closes, and then step S
31, the process returns to step S2. Step S13. S1
If both of the determinations in step 4 are YES, the operating state has shifted to the relief valve open region on the low flow rate and low rotation side from line L1 in FIG. After opening the valve 24,
The process returns to step S2 via step S31.

If the determination in step S5 is No, F=3,
This means that the previous operating state was in the relief valve closed region within the P region, and the state is after the transition from the P+S region. In this case, the intake air amount Q is the first set intake air ff1Q1
(step 519), and if the determination is YES, the engine rotation speed R is the first set rotation speed R.
Determination of whether the value is smaller than 1 (step 520), and step S19. Intake f when any of the S2Q determinations is NO
Determination of whether f1Q is greater than the fourth set intake air amount Q4 (step 521), and if the determination is No, determination of whether the engine rotation speed R is greater than the fourth set rotation speed R4 (step 522) Based on this, the following processing is performed. That is, step St9. If any judgment of S2o is No
and the determinations in steps 821 and 822 are both N
If o, the operating state is line Ll.

Since it is maintained in the region between L4, the exhaust cut valve 5 and the relief valve 24 are kept in the previous state (exhaust cut valve 5
Step 33 with the relief valve 24 closed)
1 and then returns to step S2.

If the determinations in steps Sη and S20 are both YES,
Since the operating state has shifted to the relief valve open region on the low flow rate and low rotation side from line L1 in FIG. 2, F=1 is set in step S23, and relief valve 2 is opened in step S24.
4, then step S31 and step S.
Return to 2. If the determination is YES in any of the steps S21 and 822, the operating state has crossed the line L4 in FIG.
4, the exhaust gas cut valve 5 is opened in step 826, and then the process proceeds to step S31 and then to step S2.
Return to

If the determination in step S6 is No, the result is F-4, which means that the previous operating state was in the above P+Sft range. In this case, based on the determination of whether the intake air i1Q is smaller than the third set intake air IQ3 (step 527) and the determination of whether the engine speed R is smaller than the third set speed R3 (step 528), the following steps are performed. Perform processing like this. That is, if the determination in either step S27 or S2a is NO, the operating state is maintained in the P+sgA range, so the exhaust cut valve 5 and the relief valve 24 are kept in their previous state (exhaust cut valve 5 is opened, The process returns to step S2 via step S31 while keeping the relief valve 24 closed.

Step S27. If the determinations in S2a are both YES, the operating state has shifted to the P region on the low flow rate and low rotation side from line L3 in FIG. After closing the valve 5, the process returns to step S2 via step S31.

FIG. 4 shows an overspeed prevention routine performed in step S32 when flag F is 2 in the control shown in FIG.
If the closed state continues for a long time, the second turbo supercharging 1fi
2 is in an overspeed state, the relief valve 24 is opened and closed based on time measurement.

That is, in this routine, the timer T is counted up in step 833, and the timer T is counted up in step S34.
It is checked whether a predetermined time α that causes an overspeed state of the turbo supercharger 24 has been exceeded, and if the determination is YES,
Furthermore, in step S35, the timer T is set for the predetermined time α.
It is checked whether or not the time exceeds the predetermined overspeed elimination time β. Then, the relief valve 24 is closed in step S36 until the timer T exceeds the predetermined time α, but when the timer T is between α and α+β (the determination in step S33 is YES and the determination in step S35 is Judgment is N
In step 837, the relief valve 24 is closed. Further, when the timer T exceeds the time α+β, the timer T is cleared to 0 in step S3a.

Therefore, when the operating state continues for a long time in the relief valve closed region within the P region where the flag F is 2, the relief valve 24 is initially closed and the predetermined time is reached, as shown in FIG. It is closed when α has elapsed, and then closed again when time β has elapsed, and this operation is repeated.

According to the control device of this embodiment as described above, P on the low flow rate and low rotation side is controlled according to the flowchart in FIG.
In this region, the exhaust cut valve 5 is closed, and substantially only the first turbo supercharger 1 is operated, increasing the supercharging efficiency in the low flow region. In this region P, on the lower flow 1 side further from the exhaust leak valve opening line in FIG. 2, the exhaust leak valve 8
are also closed, and the relief valve 24 is open. and,
When changing the operating state from the low flow rate side to the Shimanagareya side, the exhaust leak valve 8 is first switched from closed to open when the exhaust leak valve opening/closing line is crossed, and then the relief valve 24 is switched from closed to open when the line L2 is crossed. After the exhaust gas cut valve 5 is switched from closed to closed, when the line L4, which is the switching point of the supercharger operating state, is roughly crossed, the exhaust cut valve 5 is switched from closed to open. In this state, exhaust gas is sufficiently supplied to the turbine 2a of the second turbocharger 2, so that the second turbocharger 2 is substantially operated in addition to the first turbocharger 1, and the high temperature is increased. Supercharging efficiency in the flow range is increased.

At the time of transition from such a low flow rate operating region to a high flow rate operating region, the second turbo supercharger 2 is pre-rotated by opening the exhaust leak valve 11 prior to opening the exhaust cut valve 5. In addition, by closing the relief valve 24, the increase in the rotational speed of the second turbocharging 1fi2 during pre-rotation is promoted as described above, so that when the p+sfR region is reached, the second turbocharging is activated with good response. Supercharging 2 is activated. When the operating state shifts to the high flow rate side due to normal acceleration operation, etc., when the rotation speed of the second turbocharger 2 increases appropriately after the relief valve 24 is closed, P
When the +S region is reached, the second turbo supercharger 2 is activated.

However, under special driving conditions or sloped road surfaces, the P
If it takes a long time to reach the +si range, the second
The turbocharger 2 is in an over-speed state where the rotation speed is higher than necessary during pre-rotation, the exhaust cut valve 5 and the intake cut valve 21 are closed, and the intake air is stagnant in the second intake passage 15b. If the condition becomes such an overspeed state,
The temperature of the air around the compressor 2b increases significantly. In such a case, the relief valve 24 is closed when a predetermined time α during which an overspeed state occurs has elapsed, and the intake air in the second intake passage 15b is relieved by the processing in the routine shown in FIG. 4. .

This causes the second turbo supercharging v! 12 rotation speed is suppressed and the over-rotation state is eliminated. Then, when the time β for eliminating the overspeed state has elapsed, the relief valve 24 is closed again, and the rotation speed of the second turbocharger 2 during pre-rotation is appropriately adjusted.

In addition, in the above embodiment, the second turbo supercharger 2 during pre-rotation
Although the overspeed state of the engine is checked by time measurement, the overspeed state may also be checked by detecting the rotational speed of the second turbo supercharger 2 or the like.

Further, in the above embodiment, the state is switched between a state in which only the first turbocharger 1 operates and a state in which both turbochargers 1 and 2 are operated in the low flow rate side operating region and the high flow rate side operating region. However, in addition to using a second turbocharger with a larger capacity than the first turbocharger, in the high-flow operation region where the second turbocharger is in the supercharging operation state, the first turbocharger The control device of the present invention can also be applied to a device that stops the first turbo supercharging by cutting off the exhaust gas supply to the turbine.

〔Effect of the invention〕

As described above, the present invention improves supercharging efficiency by providing at least a first turbocharger that operates in a low-flow operation region and a second turbocharger that is dedicated to a high-flow operation region. In the engine with an exhaust turbo supercharger, the second turbo supercharger side exhaust passage and the second turbo supercharger side intake passage are blocked and the second turbo supercharger is in an operating region where supercharging is stopped. In the meantime, a small amount of exhaust gas is sent from the exhaust leak passage to the turbine of the second turbocharger to pre-rotate the second turbocharger, and the second turbocharger is switched to a supercharging operation state. Since the relief valve of the relief passage for the intake passage on the second turbocharger side is closed near the point, the pre-rotation of the second turbocharger is promoted and the response at the time of transition to the supercharging operation state is You can increase your sexuality. Moreover, when the second turbo supercharger becomes over-speed during pre-rotation, the relief valve is opened, so the second turbo supercharger
It is possible to reliably prevent the turbocharger from becoming overheated during pre-rotation, thereby increasing reliability.

[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 diagram showing the operating characteristics of eight valves arranged in the exhaust system and intake system. FIG. 4 is a flowchart showing the overspeed prevention routine, and FIG. 5 is a time chart showing the relief valve opening/closing operation by the overspeed prevention routine. E... Engine, 1... First turbo supercharger, 2...
・Second turbo supercharger, 5...exhaust cut valve, 10...
・Exhaust leak passage, 21...Intake cut valve, 23...
- Relief passage, 24... Relief valve, 50... Control unit, 51... Relief control means. Patent applicant Mazda Co., Ltd. Agent
People Patent Attorney Etsushi Kotani @';z', \\
Town capture chart chart 1 = 0 ; U T = 0

Claims (1)

[Claims] 1. A first turbocharger that operates at least in a low-flow operation region and a second turbocharger dedicated to a high-flow operation region, where the turbine of the second turbocharger operates in a low-flow operation region The second turbo supercharger side exhaust passage that guides exhaust gas to the second turbo supercharger side and the second turbo supercharger side intake passage that guides intake air from the compressor of the second turbo supercharger to the engine side are shut off. When the supercharging is stopped and the state shifts to a high flow rate operation region after a predetermined switching point, the second turbocharger side exhaust passage and the second turbosupercharger side intake passage are opened. In an engine with an exhaust turbo supercharger in which the supercharger is switched to a supercharging operating state,
Before the second turbocharger is brought into the supercharging operation state, the second
an exhaust leakage passage that guides a small amount of exhaust gas to the turbine of the second turbocharger so as to pre-rotate the turbocharger; a relief passage that communicates the compressor outlet side of the second turbocharger with the upstream side of the compressor; A relief valve that opens and closes this relief passage, and a relief valve that closes the relief valve near the switching point in the operating region where the second turbo supercharger is pre-rotated, while the second turbo supercharger is over-rotated during the pre-rotation. 1. A control device for an engine with an exhaust turbo supercharger, comprising: relief control means that opens the relief valve when the above-mentioned condition is reached.