JPH0396621A - Control device for engine with turbo-supercharger - Google Patents

Abstract

PURPOSE:To enhance the reliability of a primary turbo-supercharger by controlling a target supercharging pressure to be low when an exhaust cut valve is judged to have been closed in an operating range where a secondary turbo-supercharger shall be in operation, and thereby accelerating to release exhaust gas by a relief means. CONSTITUTION:exhaust passages 202 and 203 to which the turbines 205 and 207 of a primary and a secondary turb-superchargers 204 and 206 are interposed respectively, are communicated with each other by a communicating passage 222 at the upstream sides of the respective superchargers 204 and 206, and an exhaust gas cut valve 223 is provided for the exhaust passage 203 at a position adjacent to the downstream of the open position of the communicating passage 222. In addition, a waste gate passage 225 which communicates the middle of the communicating passage 222 with a joint exhaust passage 224 and an exhaust sniffing passage 228 which communicates the passage 225 with the passages 203 are provided so that relief valves 227 are 230 provided for the middle of the respective passage 225 and 228 are controlled in such a way that the supercharging pressure is controlled to be low when the exhaust cut valve 223 is closed in an operating range where the supercharger 204 shall be in operation.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention includes a primary and a secondary exhaust turbo supercharger, and activates or deactivates the secondary turbo supercharger depending on the amount of intake air. The present invention relates to a control device for a turbocharged engine.

(Prior Art) Conventionally, as this type of turbocharged engine, for example, as disclosed in Japanese Utility Model Application Publication No. 178329/1983,
The turbines of the primary and secondary exhaust turbo superchargers are installed in parallel in the exhaust passage, and the blowers of these two exhaust turbo superchargers are connected to the intake passage of the engine, and the turbines of the secondary turbo supercharger are connected to the upstream side of the turbine of the secondary turbo supercharger. An exhaust cut valve is installed in the exhaust passage, and in the low intake air amount range where the intake air amount is less than the set value, the exhaust cut valve is closed to deactivate the secondary turbo supercharger, and the exhaust gas from the exhaust passage is diverted to the primary turbo supercharger. While ensuring high boost pressure by intensively supplying air to the feeder turbine, in high intake air flow ranges where the intake air flow is higher than the set value, the exhaust cut valve is opened to operate the secondary turbo supercharger. A so-called sequential turbo engine is known, which supplies exhaust gas from the exhaust passage to the turbines of two exhaust turbo superchargers to obtain an appropriate boost pressure while ensuring the amount of intake air. .

(Problem to be Solved by the Invention) However, if the exhaust cut valve has a delay when opening or is left closed due to a failure, even if the intake air amount increases and exceeds the set value. Since the exhaust gas is supplied to the primary turbocharger in a concentrated manner, the exhaust pressure upstream of the primary turbocharger becomes excessive, which impairs the reliability of the primary turbocharger.

By the way, in such an engine with a turbo supercharger, when controlling the supercharging pressure, a waste gate passage that bypasses the exhaust turbo supercharger is provided in the exhaust passage, and a waste gate valve is provided in this waste gate passage. , the opening degree of the wastegate valve is adjusted so that the boost pressure of the engine becomes the target boost pressure.

The present invention has been made with attention to these points,
The purpose of this is to reduce the amount of exhaust gas cut off, such as by using a wastegate valve, when the exhaust cut valve is delayed in its opening operation or remains closed due to a malfunction in a sequential turbo engine such as the one described above. The object of the present invention is to reduce the exhaust pressure applied to a brimarita single-bore supercharger by using a supercharging pressure control device equipped with a relief means.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, when the exhaust cut valve has a delay in opening operation or is left closed due to a failure, the exhaust cut valve, such as a waste gate valve, etc. The relief means is forced to open.

Specifically, the solution taken by the present invention, as shown in FIG. 1, includes primary and secondary exhaust turbo superchargers each having a turbine in an exhaust passage provided in parallel with the engine. , an engine equipped with a turbo supercharger that has an exhaust cut valve installed in the exhaust passage exclusively for the secondary turbo supercharger, and opens the exhaust cut valve only in the high intake air flow range of the engine to operate the secondary turbo supercharger. Assumed. On the other hand, there is a supercharging pressure detection means 257 that detects the supercharging pressure of the engine, and an exhaust relief means 227 that is provided in the exhaust passage upstream of the hybrid turbo supercharger and relieves exhaust gas. 230, a supercharging pressure control means 301 that receives the output of the supercharging pressure detection means 257 and controls the exhaust relief means 227, 230 so that the engine supercharging pressure reaches the target supercharging pressure, and the exhaust cut valve. valve operation detection means 258 for detecting the operating state of the engine; intake air amount detection means 302 for detecting the intake air amount of the engine;
The valve operation detection means 258 and the intake air amount detection means 3
Target value changing means 302 is provided which receives the output of 02 and changes the target supercharging pressure in the supercharging pressure control means 301 to a lower level when the exhaust cut valve is closed in the operating region where the secondary turbo supercharger should operate. It is structured as follows.

(Function) With the above structure, in the present invention, the supercharging pressure detection means 257
Based on the detection, the exhaust relief means 227 and 230 are controlled by the boost pressure control means 301, and the boost pressure of the engine becomes the target boost pressure.

In that case, if the exhaust cut valve is delayed in its opening operation or remains closed due to a failure, the secondary turbo supercharger is activated based on the detection by the valve operation detection means 258 and the intake air amount detection means 302. It is determined that the exhaust cut valve is closed in the desired operating range, and the target value changing means 30
2, the target supercharging pressure is changed to a lower value, the exhaust relief means 227, 230 promotes exhaust relief by the exhaust relief means 227, 230 to lower the supercharging pressure, and the exhaust pressure applied to the brimary turbo supercharger is prevented from becoming excessive. This improves the reliability of the primary turbocharger.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a two-rotor type turbocharged rotary piston engine equipped with a boost pressure control device according to an embodiment of the present invention. In FIG. 2, 201 is an engine, and exhaust passages 202 and 203 are provided independently of each other. And these two exhaust passages 202
．． A turbine 205 of a primary turbocharger 204 is disposed on one side of the turbocharger 203, and a turbine 207 of a secondary turbocharger 206 is disposed on the other side.

That is, in this engine 201, the exhaust passages 202 and 203 of each cylinder are independently connected to the turbines 205 of both the primary and secondary exhaust turbo superchargers 204 and 206.
, 207, both exhaust turbo superchargers 204
, 206, the exhaust dynamic pressure is effectively applied to both turbines 205 and 207 in the region where supercharging is performed, thereby improving supercharging efficiency. Two exhaust passages 202, 203
are joined downstream of both turbines 205 and 207 to form a single exhaust passage 224.

Further, the intake passage 209 is divided into two downstream of an air cleaner (not shown), and the blower 211 of the primary turbo supercharger 204 is in the middle of the first branch passage 210, and the blower 211 of the primary turbo supercharger 204 is in the middle of the second branch passage 212. The blower 213 of the secondary turbo supercharger 206 is installed. These branch passages 210 and 212 are formed so as to face each other at the branch part and extend substantially in a straight line on both sides. Also,
The two branch passages 210 and 212 are connected to each blower 211 and 21.
It rejoins downstream of 3. Then, an intercooler 214 is disposed in the intake passage 209, which has become one again, and a surge tank 215 is disposed downstream of the intercooler 214, and a throttle valve 216 is disposed between the intercooler 214 and the surge tank 215. It is set up. Further, the downstream end of the intake passage 209 branches into two independent intake passages 217 and 218 corresponding to each section of the engine 201, and is connected to each intake boat (not shown). Each of these independent intake passages 217 and 218 has a fuel injection valve 219,
220 are arranged.

On the upstream side of the intake passage 209, an air flow meter 221 is provided upstream of the branch of the first and second branch passages 210 and 212 to detect the amount of intake air. The surge tank 215 also includes a supercharging pressure sensor 257 as supercharging pressure detection means for detecting the supercharging pressure of the engine.
is provided. 253 is a rotation speed sensor that detects the engine rotation speed. The air flow meter 221 and rotational speed sensor 253 function as an intake air amount detection means for detecting the intake air amount of the engine.

The two exhaust passages 202, 203 are communicated with each other by a relatively small diameter communication passage 222 upstream of both the primary and secondary turbo superchargers 204, 206. In the exhaust passage 203 in which the secondary turbine 207 is disposed, an exhaust cut valve 223 is provided immediately downstream of the opening position of the communication passage 222.

In addition, an evening bottle 20 extending from the middle of the communication path 222 is provided.
A waste gate passage 225 is formed which communicates with the combined exhaust passage 224 downstream of 5, 207, and a waste gate valve 227 to which a diaphragm type actuator 226 is linked is disposed in the waste gate passage 225.

A leakage passage 228 is provided that communicates the wastegate valve upstream part of the wastegate passage 225 with the exhaust cut valve downstream part of the exhaust passage 203 connected to the secondary turbine 207. The exhaust leak passage 22
8 is provided with an exhaust leak valve 230 linked to a diaphragm type actuator 229.

The exhaust cut valve 223 is linked to a diaphragm type actuator 231. This actuator 2
31 is provided with a position sensor 258 that detects the opening degree of the exhaust cut valve 223. This position sensor 258 functions as a valve operation detection means for detecting the operating state of the exhaust cut valve 223.

On the other hand, an intake cut valve 232 is provided downstream of the blower 213 in the branch passage 212 in which the blower 213 of the secondary turbocharger 206 is provided. This intake cut valve 232 is constituted by a butterfly valve, and is also linked to a diaphragm type actuator 233. In addition, a blower 21 is installed in the branch passage 212 on the secondary side.
A relief passage 234 is formed so as to bypass 3, and a diaphragm type intake relief valve 235 is disposed in the relief passage 234.

The actuator 22 that operates the exhaust leak valve 230
The pressure chamber 9 is connected via a conduit 236 to a branch passage 21 in which a blower 211 of a brimary turbo supercharger 204 is disposed.
It is connected downstream of the blower 211 of No. 0.

The conduit 236 includes a duty solenoid.
A valve 256 is provided, and by adjusting its duty ratio, the pressure introduced from downstream of the blower 7211 is adjusted as appropriate. Through this adjustment, the pressure in the pressure chamber of the actuator 229 is adjusted, and the opening degree of the exhaust leak valve 230 is changed. By opening the exhaust leak valve 230, a small amount of exhaust gas flows through the exhaust leak passage 228 and is supplied to the secondary turbine 207 when the exhaust cut valve 223 is closed. therefore,
The secondary turbo supercharger 206 is connected to the exhaust cut valve 2
Rotation is started in advance before 23 opens.

The actuator 23 that operates the intake cut valve 232
The pressure chamber No. 3 is connected to an output port of an electromagnetic solenoid type three-way valve 238 through a guide tube 237. Further, the actuator 231 that operates the exhaust cut valve 223 is
Another three-way valve 240 of the electromagnetic solenoid type is connected to the conduit 239.
connected to the output port of the Furthermore, the pressure chamber of the actuator 241 that operates the intake relief valve 235 is
Another three-way valve 243 of electromagnetic solenoid type is connected to the conduit 242.
connected to the output boat. Intake relief valve 235
is a predetermined time before the exhaust cut valve 223 and the intake cut valve 232 open. The relief passage 234 is kept open until the end of the period. Thereby, when the secondary turbo supercharger 206 rotates 1,000 revolutions due to the exhaust gas flowing through the exhaust leak passage 228, air is circulated through the blower 213 of the secondary turbo supercharger 206, and the temperature of the blower 213 is prevented from increasing. This prevents the pressure upstream of the intake cut valve 232 from rising and entering the surging region.

The actuator 226, which operates the wastegate valve 227, is connected to the conduit 236 by a conduit 244. The conduit 244 is provided with a duty solenoid valve 245, and by adjusting its duty ratio, the pressure introduced from downstream of the floor 211 is adjusted as appropriate. Through this adjustment, the pressure in the pressure chamber of the actuator 226 is adjusted, and the opening degree of the waste gate valve 227 is changed.

The above three electromagnetic solenoid type three-way valves 238, 240
, 243, Duty Solenoid Valve 256
245 and the two fuel injection valves 219 and 220 are controlled by a control unit 246 configured using a microcomputer. The control unit 246 includes an output signal of the engine rotation speed sensor 253,
Output signal of air flow meter 221, supercharging pressure sensor 25
In addition to the output signal of the position sensor 258 and the output signal of the position sensor 258, the throttle opening, the supercharging pressure P1 downstream of the blower 211, and the like are input manually.

One manual port of the electromagnetic solenoid type three-way valve 238 for controlling the intake cut valve 232 is connected to a negative pressure tank 248 via a conduit 247, and the other manual port is connected to a negative pressure tank 248 via a conduit 247.
49 to the output boat 27 of the differential pressure detection valve 250, which will be described later.
Connected to 0.

Intake negative pressure downstream of the throttle valve 216 is introduced into the negative pressure tank 248 via a check valve 251 . Furthermore, one manual port of the three-way valve 240 for controlling the exhaust cut valve is open to the atmosphere, and the other input port is
It is connected via a conduit 252 to the conduit 247 which is connected to the negative pressure tank 248 . On the other hand, one manual boat of the three-way valve 243 for controlling the intake relief valve 235 is connected to the negative pressure tank 248, and the other input boat is open to the atmosphere. The waste gate valve 227 and the exhaust leak valve 230 are connected to the brimary turbo supercharger 2.
It is provided in the exhaust passage upstream of 04 and functions as an exhaust relief means for relieving exhaust gas.

As shown in FIG. 3, the differential pressure detection valve 250 has three chambers 264, 265, 2 formed by two first and second diaphragms 262, 26B in its casing 261.
It is divided into 66 sections. A first human-powered boat 267 is opened in the first chamber 264 at one end, and the inner surface of the end of the casing 261 and the first diaphragm 26
A compression spring 268 is disposed between the two. In addition, a second input port 269 is provided in the second chamber 265 in the middle.
In the third chamber 266 on the other end side, an output boat 270 is opened at the center of the end wall of the casing 261, and an atmosphere release boat 271 is opened at the side wall. The first diaphragm 262 includes a second diaphragm 26.
A valve body 272 is fixedly provided, passing through the third chamber 266 and extending toward the output port 270 of the third chamber 266.

The first input boat 267 is connected by a conduit 273 to the third
As shown in the figure, it is connected to the downstream side of the intake cut valve 232, and introduces the supercharging pressure P1 downstream of the intake blower 7211 into the first chamber 264.

The second input boat 269 is also connected upstream of the intake cut valve 232 by a conduit 274, so that the second input boat 269 is connected upstream of the intake cut valve 232 when the intake cut valve 232 is closed.
The upstream pressure P2 is introduced. This i
Pressure P introduced from I14 person ports 267, 269
When the difference between i and P2 (P2-PL) exceeds a predetermined value, the valve body 272 opens the output boat 270. This output port 2
70 is connected via a conduit 249 to one of the input ports of a three-way valve 238 for controlling the intake cut valve 232. Therefore, when the three-way valve 238 is ON, the intake cut valve 2
With the conduit 237 connected to the pressure chamber of the actuator 233 for 32 operation connected to the conduit 249 connected to the output port of the differential pressure detection valve 250, the pressure upstream of the intake cut valve 232, that is, the supercharging pressure on the P2 approaches the primary side supercharging pressure PI, and the differential pressure PI-P
2 disappears and the differential pressure P2-Pi becomes larger than a predetermined value, the atmosphere is introduced into the actuator 233 and the intake cut valve 232 is opened. Also, three-way valve 238
is turned OFF and the above conduit 2 of the actuator 233 is turned OFF.
37 is connected to a conduit 247 connected to a negative pressure tank 248, negative pressure is supplied to the actuator 233, and the intake cut valve 232 is closed.

On the other hand, the exhaust cut valve 223 is activated when the three-way valve 240 for controlling the exhaust cut valve 223 is OFF and the actuator 231 for operating the exhaust cut valve 223 connects the conduit 239 connected to the pressure chamber to the conduit 252 on the negative pressure tank 248 side. , is closed by supplying negative pressure to the actuator 231.

Further, when the three-way valve 240 is turned on and the conduit 239 on the output side is released to the atmosphere, the exhaust cut valve 223 is opened and supercharging is performed by the secondary turbo supercharger 2o6.

The intake relief valve 235 is operated by the actuator 241 when the three-way valve 243 for controlling the intake relief valve 235 is OFF and the conduit 242 connected to the pressure chamber of the actuator 241 for operating the intake relief valve 235 is communicated with the negative pressure tank 248 side. Opens when negative pressure is supplied, and
When the three-way valve 243 is turned on and the conduit 242 connected to the pressure chamber of the actuator 241 is released to the atmosphere, it is closed.

In this embodiment, hysteresis is provided in the opening and closing operations of the exhaust cut valve 223, the intake cut valve 232, and the intake relief valve 235, as will be described later. In addition, in order to prevent intake air from flowing backward into the secondary blower when the exhaust cut valve 223 closes and the intake cut valve 232 remains open during the transition from the high intake air amount region to the low intake air amount region, The intake cut valve 232 is forcibly closed after a predetermined time (for example, 2 seconds) has elapsed starting from the time when the exhaust cut valve 223 is closed.

FIG. 4 is a control map showing the opening/closing control of the intake cut valve 232, the exhaust cut valve 223, and the intake relief valve 235, together with the basic control of the exhaust leak valve 230. This map is stored in the control unit 246, and the four electromagnetic solenoid type three-way valves 238, 240, 243 are controlled based on this map.

When transitioning from a low intake air amount region to a high intake air amount region, the intake relief valve 235 is open in a region where the engine speed R is low or the intake air QQ is small.
Pre-rotation of the secondary turbocharger 206 is performed by opening the exhaust leakage valve 230. Then, when the engine speed reaches R2 or the intake air amount reaches the line Q2, the solenoid type three-way valve 243 for controlling the intake relief valve 235 is turned on and the intake relief valve 235 is closed.

When the Q4-R4 line is reached, the solenoid type three-way valve 240 for controlling the exhaust cut valve 223 is turned ON and the exhaust cut valve 223 is opened, and then the Q6-R6 line is reached, and the solenoid type three-way valve 240 for controlling the exhaust cut valve 223 is turned on. When the solenoid type three-way valve 238 is turned on and the intake cut valve 232 is opened, supercharging by the secondary turbo supercharger 206 starts.

In other words, the engine enters the supercharging region using both the primary and secondary superchargers at the Q6-R6 line.

Note that the actuator 23 that drives the intake cut valve 232
3 is not only controlled by the operation of the solenoid 238, but also because atmospheric pressure, which is the pressure source that opens the intake cut valve 232, is supplied via the differential pressure detection valve 250, the actual operation of the intake cut valve 232 is The opening operation will be delayed relative to the operation of the solenoid 238. Therefore, the lines Q6 and R6 that turn the intake cut valve 232 control solenoid 238 from OFF to ON are set in consideration of the delay caused by the differential pressure detection valve 250, and as a result, the lines Q6 and R6 are set to Control solenoid 240 is OFF
It is assumed that the line is close to the line of Q4 and R4 which turn on from F. Further, these Q6, R6 and Q4, R4 can also be made to match.

Conversely, when transitioning from a high intake air amount region to a low intake air amount region, each solenoid type three-way valve 238, 240, 243 that controls the intake cut valve 232, the exhaust cut valve 223, and the intake relief valve 235 has hysteresis. Fourth
Q5-R5 and Q3-R3, respectively, as shown by broken lines in the figure.
, Ql-Rl. In other words, when transitioning from a high intake air amount area to a low intake air amount area, when the line Q3, R3 is reached, the exhaust cut valve 2
The intake cut valve 232 is closed when the closing control of 23 is performed, and when the transition to the low intake air amount region reaches the line Q5 and R5, the intake cut valve 232 is closed.
The intake relief valve 23 is closed after a delay.
5 opening control is performed.

In this way, by closing the intake cut valve 232 later than the exhaust cut valve 223, surging is prevented from occurring when transitioning to the low intake air amount region.

In addition, in FIG. 4, the bent portions of each of the above lines are on the so-called no-load line or load-load line.

Therefore, in the above embodiment, when the engine is in a lower intake air amount region than line Q6-R6, the introduction of exhaust gas to the secondary turbo supercharger 206 is stopped, so only the secondary turbo supercharger 204 is operated. When activated, high boost pressure can be obtained quickly. On the other hand, when the engine is in a higher intake air amount region than the above line Q6-R6, both the primary turbo supercharger 204 and the secondary turbo supercharger 206 operate to maintain the appropriate supercharging pressure while ensuring the intake flow rate. will be obtained.

Figure 5 shows the relationship between the solenoid operating state of each valve and the transition of the operating state (the left side of the horizontal axis is the low intake air amount region, and the right side is the high intake air amount region) based on the characteristic diagram in Figure 4 above. This is what I saw. As can be seen from this figure, the hysteresis of the opening/closing operation of the exhaust cut valve 223 is completely included in the hysteresis of the opening/closing operation of the intake cut valve 232. Note that even if the solenoid 238 for controlling the intake cut valve 232 is turned on at 06 and R6, the actual opening operation of the intake cut valve 232 is delayed due to the action of the differential pressure detection valve 250, as shown by the broken line in the figure. Therefore, Q6 and R6 are set close to or on the same line as Q4 and R4 of the exhaust cut valve 223 opening control as described above. On the other hand, the intake cut valve 23
The closing operation of No. 2 does not involve the above-mentioned delay with respect to the operation of the solenoid 238, so the setting line Q
5, R5 must satisfy Q5<Q3, R5<R3.

Next, the control of the duty solenoid valves 256, 245 by the control unit 246 will be explained. First, the control of the exhaust leak valve 230 by the duty solenoid valve 256 will be explained. This control is
This is done based on a map of engine speed and target boost pressure as shown in FIG. In the figure, the two-dot chain line indicates the boost pressure characteristics required by the engine. On the other hand, the solid line indicates the position of the exhaust cut valve 22 due to the position ● sensor 258.
3 indicates the map that is referred to when it is detected that the exhaust cut valve 223 is open, and the broken line indicates the map that is referenced when the position sensor 258 detects that the exhaust cut valve 223 is closed. The characteristics of each map will be explained below.

■When the exhaust cut valve is open (solid line), a target boost pressure higher than the required boost pressure is set over the entire engine speed range. With this setting, the exhaust leakage valve 230 is closed in order to raise the boost pressure to a higher target boost pressure, and the leakage valve 230 is prevented from opening and closing inadvertently, improving its reliability.

■When the exhaust cut valve 223 is closed (dashed line) In the low engine speed range (low intake air amount range), the primary turbo supercharger 2
Since the capacity settings of 04 and the like have been made, a target boost pressure that almost matches the required boost pressure is set.

On the other hand, in the high rotation range of the engine (high intake air amount range), the fact that the exhaust cut valve 223 is closed means that the exhaust cut valve 223 is closed.
3 means that there is a delay in the opening operation or the valve is left closed due to a failure, so a target boost pressure lower than the required boost pressure is set. As a result, the leak valve 230 is opened to lower the supercharging pressure, promoting exhaust relief, preventing the exhaust pressure applied to the brimary turbo supercharger 204 from becoming excessive, and preventing the brimary turbo supercharger 204 reliability is improved. Furthermore, by preventing the exhaust pressure from becoming excessive, it is possible to prevent engine misfires and torque shocks.

Next, control of the wastegate valve 227 by the duty solenoid valve 245 will be explained.

This control is performed based on a map of engine speed and target boost pressure as shown in FIG. In the same figure,
The two-dot chain line indicates the boost pressure characteristics required by the engine. On the other hand, the solid line indicates the map that is referred to when the position sensor 258 detects that the exhaust cut valve 223 is open, and the broken line indicates that the position sensor 258 detects that the exhaust cut valve 223 is closed. Indicates the map to be referenced when The characteristics of each map will be explained below.

■When the exhaust cut valve is open (solid line), a target boost pressure that almost matches the required boost pressure is set over the entire engine speed range. With this setting, the boost pressure is controlled to the target boost pressure.

■When the exhaust cut valve is closed (broken line) In the low engine speed range (low intake air amount range), a target boost pressure higher than the required boost pressure is set.

With this setting, the wastegate valve 227 is closed in order to raise the boost pressure to a higher target boost pressure, and the wastegate valve 227 is prevented from opening/closing inadvertently, improving its reliability.

On the other hand, in the high rotation range of the engine (high intake air amount range), the fact that the exhaust cut valve 223 is closed means that the exhaust cut valve 223 is closed.
3 means that there is a delay in the opening operation or the valve is left closed due to a failure, so a target boost pressure lower than the required boost pressure is set. As a result, the waste gate valve 227 is opened to lower the supercharging pressure, promoting exhaust relief, and the primary turbo supercharger 204
The reliability of the primary turbocharger 204 is improved by preventing the exhaust pressure from becoming excessively high. Furthermore, by preventing the exhaust pressure from becoming excessive, it is possible to prevent engine misfires and torque shocks.

Note that although Figures 6 and 7 only show two types of maps for engine speed and target boost pressure, these are illustrative maps for specific loads; There are two types of maps for each.

Next, control of each valve based on the characteristics shown in FIG. 4 will be explained using a control circuit shown in FIG. 8. The intake relief valve operating solenoid 243 is connected to the first comparison circuit 11 shown at the top of the figure.
1 and the output of the second comparison circuit 112 shown below it are controlled by the output of the first OR circuit 121 which is manually operated. Here, the first comparison circuit 111 compares the intake air mQ, which is the detection signal of the air flow meter 221, and the output value of the first addition circuit 131, which is a reference value. The first adder circuit 131 receives the set value Q1 corresponding to the Q+ line in FIG. 3, and
#L called Q' + for this Q1 (however, Q+
+Q' + -Q) is manually input through the first gate 141, and when the first gate 141 is opened, the first comparison is performed using Q+ +Q'1-Q2 as a reference value. output to the circuit 111 and also the first gate 14
When Q1 is closed, Q1 is output to the first comparison circuit 111 as a reference value. And this first gate 14
1 is opened and closed by the output of the first OR circuit 121.

The second comparison circuit 112 compares the engine rotation speed R detected by the engine rotation speed sensor with the output value of the second addition circuit 132, which is a reference value. The second adder circuit 132 has a set value R1 corresponding to the R1 line in FIG. 142, and when the second gate 142 is opened, it outputs R1+R'1-R2 as a reference value to the second comparator circuit 112, and When 142 is closed, it outputs R1 to the second comparison circuit 112 as a reference value. second gate l
42 is also opened and closed by the output of the first OR circuit 121.

The first and second comparison circuits 111 and 112 convert the detected intake air ffiQ and engine rotation speed R into a first
and the respective reference values, which are the outputs of the second adder circuit, and turn ON when Q or R exceeds the reference value.
A signal is output to the intake relief valve operating solenoid 243 (when turned ON, the intake relief valve 235 is closed). The first and second gates 141 and 142 are connected to the first OR circuit 12.
It is closed when the output signal of No. 1 is ON, and is opened when the OR circuit signal is OFF. Therefore, at the time of transition from the low intake air amount area to the high intake air amount area, the output signal of the first OR circuit 121 is OFF, so each gate 141
, 142 are opened and the first and second comparison circuits 111, 1
12, Q, and R2 are input manually as reference values. Therefore, in FIG. 3, Q2, R. When the line is reached, an ON signal is issued and the intake relief valve 235 is opened. Also, this ON signal causes the first and second gates 141.14
2 is closed, so that the reference values of Q and R become Ql and Rl, respectively. In other words, the line is set with hysteresis corresponding to Q'1 and R'l in preparation for a shift in the opposite direction.

The exhaust cut valve actuation solenoid 240 is also controlled by a similar control circuit. In other words, the intake air ffiQ
A third comparison circuit 113 is provided for the engine rotation speed R, and a fourth comparison circuit 114 is provided for the engine rotation speed R, and the outputs of these comparison circuits 113 and 114 are provided to the second OR circuit 12.
2 to the solenoid 240. Similarly, a third addition circuit 133 is provided for the third comparison circuit 113, and a fourth addition circuit 134 is provided for the fourth comparison circuit 114. Then, the set value Q3 is manually input to the third adder circuit 133, and Q'3 (however, Q3 +Q'3-Q4) is input manually via the third gate 143. Similarly, the fourth addition circuit 134 has a set value R
3 and R′3 (where R
3 +R' 3 =R4) is input. Similarly, the fourth
The adder circuit 134 contains the set value R3 and the fourth gate 1.
R'3 via 44 (where R3 +R' 3 =
R4) is input. This circuit operates in the same manner as the first and second comparison circuits described above, whereby the exhaust cut valve 223 is opened based on the Qa and R4 lines in FIG. 4 when transitioning to the high intake air amount region. , Also, when transitioning to the low intake air amount region, Q3. Valve 22 by R3 line
3 is operated to close.

For the intake cut valve operating solenoid 238, the fifth
and the outputs of the sixth comparator circuits 115 and 116 are connected to the third O
A similar control circuit is provided which feeds through R circuit 123. This control circuit includes each comparison circuit 115
．． 116, the fifth and sixth adder circuits 135, 13
6, and also includes fifth and sixth gates 145, 146 for each adder circuit 135, 136. The basic operation is the same as the circuit for each valve described above. In other words, when transitioning to the high intake air amount region, Q6, R6
The intake cut valve opening control is performed by the lines Qs and Rs, and the intake cut valve closing control is performed by the lines Qs and Rs when transitioning to the low intake air amount region. Here, Q6 and R6 are similarly Qs 1Q' s-Q6, R5 +R' S-R6
It is set in the form of

However, in the case of this intake cut valve control circuit, a seventh gate 147 is connected to the output side of the third OR circuit 123, and a control signal is sent to the solenoid 238 via this gate 147.

and the second OR circuit 12 for operating the exhaust cut valve.
A timer 150 is provided that starts counting up from when the output of 2 changes from ON to OFF.
A seventh comparison circuit 117 is provided that issues an ON signal when the count value of this timer 150 exceeds a set value (for example, a value corresponding to 2 seconds), and the ON signal is output from this seventh comparison circuit 117. At this time, the seventh gate 147 is closed to forcibly close the intake cut valve 232, and at the same time, the reference values of Q and R are changed to Q6 and R6, and the timer 150 is reset. . once the 7th
When the gate 147 of the seventh comparison circuit 117 closes, the seventh comparison circuit 117
The output of is turned OFF, but since the reference value, which is the switching line, has been changed to Q6 and R6 as described above, the intake cut valve operating solenoid 238 is maintained in the closed operating state. This prevents surging from occurring due to the intake cut valve solenoid 240 remaining in the ON state for a long time while the exhaust cut valve solenoid 238 is in the OFF state during the transition to the low intake air amount region.

Next, duty solenoid valves 256, 245
Explain the control of First, in FIG. 9, 161 is a selection circuit, and the selection circuit 161 receives the output signal of the position sensor 258, the throttle opening signal, and the engine rotational speed signal, and determines the basic control amount from the map. Duty ratio D is selected and this pace duty ratio D is output to addition circuit 162. On the other hand, 163 is a selection circuit, which receives the output signal of the position sensor 258, the throttle opening signal, and the engine speed signal, and selects the output signal from a plurality of maps as illustrated in FIG. A map corresponding to the load, the operating state of the exhaust cut valve, etc. is selected, a target boost pressure corresponding to the engine speed is determined from this map, and this target boost pressure is output to the correction amount setting circuit 164. This correction amount setting circuit 164 determines a correction uD+ by comparing the output signal of the boost pressure sensor 257 with the target boost pressure, and adds this correction amount DI to the addition circuit 162.
Output to. Then, the duty solenoid valve 256 is controlled based on this control ffi(D+D+).

Further, the duty solenoid valve 245 is also controlled in the same manner as the duty solenoid valve 256 described above by the circuit shown in FIG. .

In the circuits of FIGS. 9 and 10, the selection circuit 161
, 166, addition circuits 162, 167, correction amount setting circuit 1
64,169, supercharging pressure sensor (supercharging pressure detection means)
257, the waste gate valve 227 and the exhaust leak valve 23 are operated so that the engine boost pressure reaches the target boost pressure.
supercharging pressure control means 30 for controlling o (exhaust relief means)
1. In addition, the selection circuits 163 and 168 receive the outputs of the position sensor (valve operation detection means) 258 and the intake air amount detection means 221 and 253, and the exhaust cut valve 223 is activated in the operating range where the secondary turbocharger should operate. When closed, the boost pressure control means 30
Target value changing means 3 for changing the target boost pressure in 1 to a lower value
It consists of 02.

Incidentally, if the intake cut valve 232 is left closed due to a delay in operation or a failure while the exhaust cut valve 223 is open, surging is likely to occur. Therefore, the intake cut valve 23
2 is also provided with a position sensor, and the exhaust cut valve 223
When the intake air cut valve 232 is open and the intake cut valve 232 is closed, the target supercharging pressure may be lowered by changing the map in the same manner as described above to prevent the occurrence of surging.

Further, although the above embodiments have been described with respect to a rotary piston engine, the invention is not limited to this, and the present invention can also be applied to control devices for other types of turbocharged engines, such as reciprocating engines. I can do it.

(Effects of the Invention) As explained above, according to the control device for a turbocharged engine of the present invention, the primary and secondary exhaust gases each have a turbine in the exhaust passage provided in parallel with the engine. Equipped with a turbo supercharger, an exhaust cut valve is installed in the exhaust passage dedicated to the secondary turbo supercharger,
In addition to opening the exhaust cut valve to operate the secondary turbo supercharger only in the high intake air flow range of the engine, an exhaust relief means is installed in the exhaust passage upstream of the primary turbo supercharger to relieve exhaust gas, thereby reducing the engine boost pressure. The exhaust relief means is controlled so that the target boost pressure becomes the target boost pressure, and the target boost pressure is changed to a lower value when the exhaust cut valve is closed in the operating range where the secondary turbo supercharger should operate. If the exhaust cut valve has a delay in opening, or if it remains closed due to a failure, the exhaust relief means will promote exhaust relief and prevent excessive exhaust pressure from being applied to the primary turbo supercharger. This can improve the reliability of the turbocharger.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of the present invention. Figures 2 to 10 illustrate embodiments of the present invention, with Figure 2 being a general schematic diagram, Figure 3 being a sectional view of the differential pressure detection valve, Figure 4 being a control characteristic diagram, and Figure 5 being a diagram of the control characteristics. An explanatory diagram of the operating state of the device, Figures 6 and 7 are diagrams showing maps of target boost pressure, and Figures 8-
FIG. 10 is a diagram showing the control circuit. 204...Primary turbo supercharger 206...Secondary turbo supercharger 227...Waste gate valve (exhaust relief means) 2
30...Exhaust leak valve (exhaust relief means) 257.
... Boost pressure sensor (boost pressure detection means) 301... Boost pressure control means 302... Target value changing means 221... Air flow meter (intake air amount detection means)
253... Rotation speed sensor (intake air amount detection means) 25
8...Position sensor (valve operation detection means) 204
...Bridging turbo supercharger 206...Secondary turbo supercharger 227...Waste gate valve (exhaust relief means) 2
30...Exhaust leak valve (exhaust relief means) 257...
・Supercharging pressure sensor (supercharging pressure detection means) 301...Supercharging pressure control means 302...Target value changing means 221...Air flow meter (intake air amount detection means)
253... Rotation speed sensor (intake air amount detection means) 25
8...Position sensor (valve operation detection means) 221
, 253 Fig. 5 t777 Nari T/C Fig. 6 Fig. 7 Fig. 9

Claims (1)

[Claims] (1) Equipped with a primary and secondary exhaust turbo supercharger each having a turbine in an exhaust passage provided in parallel with the engine, an exhaust cut valve is provided in the exhaust passage exclusively for the secondary turbo supercharger, and the engine In a turbocharged engine that operates a secondary turbocharger by opening an exhaust cut valve only in a high intake air amount region of Exhaust relief means provided in the exhaust passage upstream of the supercharger to relieve exhaust gas; and receiving the output of the boost pressure detection means, controls the exhaust relief means so that the boost pressure of the engine reaches the target boost pressure. a boost pressure control means for detecting the exhaust cut valve; a valve operation detection means for detecting the operating state of the exhaust cut valve; an intake air amount detection means for detecting the intake air amount of the engine; and the valve operation detection means and the intake air amount detection means. target value changing means for changing the target boost pressure in the boost pressure control means to a lower value when the exhaust cut valve is closed in an operating range where the secondary turbocharger should operate in response to the output of the boost pressure control means. A control device for a turbocharged engine.