JPH0725246U - Supercharged engine - Google Patents

Abstract

(57) [Summary] [Purpose] To speed up the closing speed of the downstream flapper type exhaust control valve to effectively reduce chattering noise when closing. [Configuration] A primary turbocharger 40 and a secondary turbocharger 50 are arranged in parallel in an intake / exhaust system of an engine body 1, and a flapper type exhaust opening downstream of a turbine upstream side of the secondary turbocharger 50. A control valve 53 is provided, and the exhaust control valve 53 is attached to the diaphragm actuator 54.
The positive pressure chamber 54a and the negative pressure chamber 54b are connected to be fully closed by opening to the atmosphere, and are fully opened by the positive pressure of the positive pressure chamber 54a and the negative pressure of the negative pressure chamber 54b. And a large capacity switching solenoid valve SO
L. 3, SOL. 4 and these switching solenoid valves S
OL. 3, SOL. 4 is a control pressure passage 73a having a large diameter,
The positive pressure chamber 54a and the negative pressure chamber 54b of the actuator 54 are communicated with each other via 74a so as to increase the valve closing speed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is an intake control valve in which a brimary turbocharger and a secondary turbocharger are arranged in parallel in the intake and exhaust systems of an engine, and the intake and exhaust systems on the secondary turbocharger side are arranged. , A supercharged engine that controls the supercharging operation of the secondary turbocharger by opening and closing the exhaust control valve, and more specifically, measures for reducing chattering noise of the exhaust control valve configured in the downstream open flapper type. .

[0002]

[Prior art]

 A Brimari turbocharger and a secondary turbocharger are arranged in parallel in the intake and exhaust systems of the engine, and an intake control valve and an exhaust control valve are respectively provided in the intake and exhaust systems connected to the secondary turbocharger. When the engine operating range is in the low speed range, both control valves are closed to stop the supercharging operation of the secondary turbocharger and only the primary turbocharger is operated in the high speed range. In the case of, a turbocharged engine is known that can improve output performance from a low speed range to a high speed range by fully opening both control valves to supercharge both turbochargers. . Here, it has been proposed by the applicant that the exhaust control valve be configured as a flapper type that opens downstream, with an emphasis on responsiveness at the time of opening.

The exhaust control valve, as disclosed in Japanese Utility Model Laid-Open No. 22622/1990, absorbs thermal expansion of the valve body and changes over time when the valve is fully closed to ensure sealing performance. It is necessary to provide play between and.

[0004]

[Problems to be solved by the device]

 However, in the flapper type exhaust control valve that opens downstream, it is directly affected by the exhaust pulsation, so when the valve opening is small and the pressure receiving area of the valve body is large, there is play between the arm and the valve body. Exhaust pulsation causes the valve element to dance, and in particular, the valve element may vibrate and collide with the valve seat immediately before the closing of the valve element, resulting in chattering noise (striking sound).

In view of the above circumstances, an object of the present invention is to provide an engine with a supercharger capable of effectively reducing chattering noise of an exhaust control valve that is a downstream open type flapper type. To do.

[0006]

[Means for Solving the Problems]

 In order to achieve the above object, the engine with a supercharger according to the present invention has a primary turbocharger and a secondary turbocharger arranged in parallel in the intake and exhaust systems of the engine, and when both are fully opened, the secondary turbocharger is installed. An intake control valve that supercharges the supercharger and stops the supercharger operation of the secondary turbocharger when both are fully closed, and a flapper-type exhaust control valve that opens downstream are installed in the secondary turbocharger. A diaphragm type actuator that has a positive pressure chamber and a negative pressure chamber and operates the above exhaust control valve is provided in each of the intake and exhaust systems connected to the positive pressure chamber and the negative pressure chamber. A switching solenoid valve that switches the control pressure that acts on the exhaust valve is closed by opening both chambers of the actuator to the atmosphere with the switching solenoid valve, closing the exhaust control valve and applying negative pressure to the negative pressure chamber and positive pressure chamber. Supply positive pressure to Therefore, in an engine with a supercharger that exhausts an exhaust control valve, set the capacity of the above switching solenoid valve to a large value, and connect this switching solenoid valve to each chamber of the above actuator through a passage with a large diameter. Is characterized by.

[0007]

[Action]

 With the above configuration, when the exhaust control valve is closed, the capacity of the switching solenoid valve and the diameter of the passage are large, so that both chambers of the actuator are quickly opened to the atmosphere, and the closing speed of the exhaust control valve is increased. Therefore, even if a large exhaust pulsation acts on the valve body as the pressure receiving area increases when the exhaust control valve is closed, the speed at which the exhaust control valve closes reduces the time for chattering noise to occur. As a result, chattering noise when the exhaust control valve is closed is substantially reduced.

[0008]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. Referring to FIG. 4, the overall structure of the engine with a supercharger to which the present invention is applied will be described. Reference numeral 1 denotes an engine body of a horizontally opposed engine (a four-cylinder engine in this embodiment). The left and right banks 3 and 4 of the crankcase 2 have combustion chambers 5, intake ports 6, exhaust ports 7, and spark plugs 8. A valve mechanism 9 and the like are provided. The left bank 3 side is provided with # 2 and # 4 cylinders, and the right bank 4 side is provided with # 1 and # 3 cylinders. Further, due to this engine shortening shape, the primary turbocharger 40 and the secondary turbocharger 50 are arranged immediately after the left and right banks 3 and 4, respectively. As an exhaust system, the common exhaust pipes 10 from the left and right banks 3 and 4 are connected to the turbines 40a and 50a of both turbochargers 40 and 50, and the exhaust pipe 11 from the turbines 40a and 50a is one exhaust pipe 12. To the catalytic converter 13 and the muffler 14.

The primary turbocharger 40 is a small-capacity low-speed type that has a large supercharging capacity in the low and middle speed range, while the secondary turbocharger 50 has a large supercharging capacity in the middle and high speed range. It is a high-speed type with a large volume. Therefore, the primary turbocharger 40 has a smaller capacity, so that the exhaust resistance becomes larger.

As an intake system, intake pipes 17a and 17b branched from an intake pipe 16 connected to the air cleaner 15 are connected to blowers 40b and 50b of the turbochargers 40 and 50, respectively. The intake pipes 18 and 19 from 50b are connected to the intercooler 20. The intercooler 20 communicates with a chamber 22 via a throttle body 27 having a throttle valve 21, and the chamber 22 communicates with each cylinder of the left and right banks 3 and 4 via an intake manifold 23. Further, as an idle control system, an idle control valve (ISCV) 25 and a check valve 26 that opens with negative pressure are provided in a bypass passage 24 between the intake pipe 16 and the intake manifold 23 immediately downstream of the air cleaner 15 at idle or during deceleration. It is sometimes installed to control the amount of intake air.

As a fuel system, an injector 30 is arranged near the port of the intake manifold 23, and a fuel passage 33 from a fuel tank 32 having a fuel pump 31 is provided with a filter 34 and a fuel pressure regulator 35 to communicate with the injector 30. To be done. The fuel pressure regulator 35 adjusts according to the intake pressure, whereby the fuel pressure supplied to the injector 30 is always kept at a constant height with respect to the intake pressure, and the fuel injection is performed by the pulse width of the injection signal. It is possible to control. As an ignition system, an ignition signal from an igniter 36 is connected to an ignition coil 8a that is continuously provided for each ignition plug 8 of each cylinder.

An operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 operates to rotate the blower 40b by the exhaust energy introduced into the turbine 40a to suck and pressurize air to constantly supercharge. A primary wastegate valve 41 equipped with a diaphragm-type actuator 42 is provided on the turbine side. A control pressure passage 44 directly downstream of the blower 40b communicates with the pressure chamber of the actuator 42 through an orifice 48 so that the wastegate valve 41 can be opened responsively when the supercharging pressure rises above a set value. To be done. Further, the control pressure passage 44 communicates the supercharging pressure with a duty solenoid valve 43 which leaks to the upstream side of the blower 40b, and a predetermined control pressure is generated by the duty solenoid valve 43 to act on the actuator 42 and the wastegate. The supercharging pressure is controlled by changing the opening degree of the valve 41. Here, the duty solenoid valve 43 is operated by a duty signal from the electronic control unit 100 described later, and when the duty ratio of the duty signal is small, the opening degree of the waste gate valve 41 is increased by a high control pressure to increase the supercharging pressure. As the duty ratio decreases, the control pressure decreases due to the increase in the leak amount as the duty ratio increases, and the opening degree of the wastegate valve 41 decreases to increase the boost pressure.

On the other hand, in order to prevent lowering of blower rotation and occurrence of intake noise when the throttle valve is suddenly closed, there are an outlet side of the intercooler 20 near the throttle valve 21 downstream of the blower 40b and an upstream side of the blower 40b. The bypass passage 46 is communicated between the two. An air bypass valve 45 is provided in the bypass passage 46 so that the negative pressure of the manifold is introduced and opened by the passage 47 when the throttle valve is rapidly closed, and the pressurized air trapped downstream of the blower is quickly leaked.

The operation system of the secondary turbocharger 50 will be described. Similarly, in the secondary turbocharger 50, the turbine 50a and the blower 50b are rotationally driven by exhaust gas to supercharge, and a secondary waste gate valve 51 having an actuator 52 is provided on the turbine side. The exhaust pipe 10 upstream of the turbine 50a is provided with a downstream open type exhaust control valve 53 having a diaphragm type actuator 54, and the butterfly type intake control valve having a similar actuator 56 is provided downstream of the blower 50b. 55, and a supercharging pressure relief valve 57 is provided in a relief passage 58 between the upper side and the lower side of the blower 50b.

The pressure operation system of each of these valves will be described. First, the surge tank 60 of the negative pressure source communicates with the intake manifold 23 through the passage 61 having the check valve 62 to store the negative pressure and buffer the pulsating pressure when the throttle valve is fully closed. Further, a switching solenoid valve SOL. For supercharging pressure relief valve that opens and closes the supercharging pressure relief valve 57. 1. Intake control valve switching solenoid valve SOL. 2. First and second exhaust control valve switching solenoid valves SOL. 3, SOL. 4, a duty solenoid valve 75 for controlling the exhaust control valve 53 to open slightly, and a secondary waste gate switching solenoid valve 70 for opening and closing the secondary waste gate valve 51. Each switching solenoid valve 70, SOL. 1 to 4 are negative pressures in the negative pressure passage 63 from the surge tank 60 by the ON / OFF signal from the electronic control unit 100, positive pressures from the positive pressure passages 64a and 64b communicating downstream of the intake control valve, and atmospheric pressure. Etc. are selected and guided to the actuator side by the respective control pressure passages 70a to 74a to operate the secondary waste gate valve 51, the boost pressure relief valve 57, and both control valves 55, 53. The duty solenoid valve 75 variably controls the positive pressure acting on the positive pressure chamber 54a of the actuator 54 according to the duty signal from the electronic control unit 100, and controls the exhaust control valve 53 to be small open.

The switching solenoid valve SOL. When the energization is turned off, the first type closes the positive pressure passage 64a side and opens the negative pressure passage 63 side, and the negative pressure is applied to the pressure chamber in which the spring of the supercharging pressure relief valve 57 is installed via the control pressure passage 71a. Is introduced to open the boost pressure relief valve 57 against the urging force of the spring. When turned on, the negative pressure passage 63 side is closed, the positive pressure passage 64a side is opened, and positive pressure is introduced into the pressure chamber of the supercharging pressure relief valve 57 to close the supercharging pressure relief valve 57.

Intake control valve switching solenoid valve SOL. When the switch 2 is turned off, the atmospheric port is closed to open the negative pressure passage 63 side, and the negative pressure is introduced to the pressure chamber in which the spring of the actuator 56 is installed via the control pressure passage 72a, so that the spring is urged. When the intake control valve 55 is closed and turned on, the negative pressure passage 63 side is closed to open the atmospheric port, and atmospheric pressure is introduced into the pressure chamber of the actuator 56, so that the intake force is increased by the spring urging force in the pressure chamber. The control valve 55 is opened.

The secondary wastegate switching solenoid valve 70 is turned off only when it is determined by the electronic control unit 100 that high-octane gasoline is used based on the ignition advance amount and the like, and is turned on when it is determined that regular gasoline is used. When the secondary waste gate switching solenoid valve 70 is turned off, the passage 65 communicating with the upstream of the intake control valve 55 is closed to open the atmospheric port, and atmospheric pressure is introduced into the actuator 52 via the control pressure passage 70a. As a result, the secondary wastegate valve 51 is closed by the biasing force of the spring arranged in the actuator 52. Further, when it is ON, the atmospheric port is closed and the passage 65 side is opened, and the supercharging pressure downstream of the secondary turbocharger 50 when both turbochargers 40, 50 are operating is guided to the actuator 52, and this supercharging pressure is increased. Accordingly, the secondary waste gate valve 51 is opened, and the supercharging pressure is relatively reduced when using regular gasoline as compared to when using high-octane gasoline.

Further, the first exhaust control valve switching solenoid valve SOL. 3 from the control pressure passage 73a to the positive pressure chamber 54a of the actuator 54 that operates the exhaust control valve 53, the second exhaust control valve switching solenoid valve SOL. The control pressure passages 74a from 4 communicate with the negative pressure chambers 54b in which the springs of the actuator 54 are installed. Both switching solenoid valves SOL. When both 3 and 4 are OFF, the first switching solenoid valve for the exhaust control valve SOL. In the third exhaust control valve switching solenoid valve SOL.3, the positive pressure passage 64b is closed to open the atmospheric port. In No. 4, by closing the negative pressure passage 63 side and opening the atmospheric port, both chambers 54a and 54b of the actuator 54 are opened to the atmosphere, and the exhaust control valve 53 is completely opened by the biasing force of the spring installed in the negative pressure chamber 54b. Close. Further, both switching solenoid valves SOL. When both 3 and 4 are ON, the atmosphere port is closed and the first exhaust control valve switching solenoid valve SOL. 3 opens the positive pressure passage 64b side, and the second exhaust control valve switching solenoid valve SOL. By opening the negative pressure passage 63 side, 4 guides positive pressure to the positive pressure chamber 54a of the actuator 54 and negative pressure to the negative pressure chamber 54b, and fully opens the exhaust control valve 53 against the biasing force of the spring. .

The first exhaust control valve switching solenoid valve SOL. An orifice 67 is provided in the control pressure passage 73a from the No. 3, a leak passage 66 is connected to the downstream side of the orifice 67 and the intake pipe 17a, and the leak passage 66 is operated by a duty signal from the electronic control unit 100. A duty solenoid valve 75 for exhaust control valve small opening control is provided. The first exhaust control valve switching solenoid valve SOL. When only 3 is ON and positive pressure is supplied to the positive pressure chamber 54a of the actuator 54 and the negative pressure chamber 54b is opened to the atmosphere, the positive pressure is leaked by the duty solenoid valve 75 and the exhaust control valve 53 is opened slightly. To do. When the duty ratio in the duty signal is large, the duty solenoid valve 75 reduces the positive pressure acting on the positive pressure chamber 54a due to the increase in the leak amount, reduces the opening degree of the exhaust control valve 53, and reduces the duty ratio. The positive pressure is increased to increase the opening degree of the exhaust control valve 53. When the engine operating condition is within the predetermined exhaust control valve small opening control region under the single turbo condition in which only the primary turbocharger 40 is supercharged, the duty solenoid valve 75 controls the exhaust control valve 53. The supercharging pressure is feedback-controlled by the opening degree, and the exhaust control valve 53 is opened slightly in accordance with the supercharging pressure control.

Various sensors will be described. The differential pressure sensor 80 is provided so as to detect the differential pressure between the upper and lower flows of the intake control valve 55, and the absolute pressure sensor 81 selectively detects the intake pipe pressure and the atmospheric pressure by the switching solenoid valve 76. It is provided. A knock sensor 82 is attached to the engine body 1, a water temperature sensor 83 is exposed to a cooling water passage connecting the left and right banks 3 and 4, and an O ₂ sensor 84 is exposed to the exhaust pipe 10. Further, a throttle sensor 85 having a throttle opening sensor and an idle switch for detecting the throttle fully closed is connected to the throttle valve 21 in series, and an intake air amount sensor 86 is arranged immediately downstream of the air cleaner 15.

A crank rotor 90 is rotatably mounted on a crank shaft 1 a supported by the engine body 1, and a crank angle sensor 87 including an electromagnetic pickup is provided on the outer periphery of the crank rotor 90. Further, a cam rotor 91 connected to a cam shaft of the valve mechanism 9 is provided with a cam angle sensor 88 for discriminating a cylinder composed of an electromagnetic pickup or the like.

The crank angle sensor 87 and the cam angle sensor 88 detect protrusions (or slits) formed at predetermined intervals on the crank rotor 90 and the cam rotor 91, respectively, as the engine runs, and detect crank pulses and cam pulses. It is output to the electronic control unit 100. Then, in the electronic control unit 100, the engine speed is calculated from the interval time of the crank pulse (detected protuberance), the ignition timing and the fuel injection start timing are calculated, and further, from the input pattern of the crank pulse and the cam pulse. Cylinder discrimination is performed.

Next, the configuration of the electronic control system will be described with reference to FIG. The electronic control unit (ECU) 100 is mainly composed of a microcomputer in which a CPU 101, a ROM 102, a RAM 103, a backup RAM 104, and an I / O interface 105 are connected via a bus line, and a predetermined stabilizing power source is provided in each part. A constant voltage circuit 106 and a drive circuit 107 for supplying the voltage are incorporated.

The constant voltage circuit 106 is connected to a battery 96 via a relay contact of an ECU relay 95, and a relay coil of the ECU relay 95 is connected to the battery 96 via an ignition switch 97. There is. Further, the constant voltage circuit 106 is directly connected to the battery 96, and further, the fuel pump 31 is connected through a relay contact of a fuel pump relay 98. That is, the constant voltage circuit 106 supplies control power to each part when the ignition switch 97 is turned on and the relay contact of the ECU relay 95 is closed, and when the ignition switch 97 is turned off. , Backup power is supplied to the backup RAM 104.

Various sensors 80 to 88, a vehicle speed sensor 89, and a battery 96 are connected to the input port of the I / O interface 105. An igniter 36 is connected to the output port of the I / O interface 105, and further, an ISCV 25, an injector 30, each switching solenoid valve 70, 76, SOL. 1 to 4, the duty solenoid valves 43 and 75, and the relay coil of the fuel pump relay 98 are connected.

Then, when the ignition switch 97 is turned on, the ECU relay 95 is turned on, a constant voltage is supplied to each unit via the constant voltage circuit 106, and the ECU 100 executes various controls. That is, in the ECU 100, the CPU 101 inputs the detection signals from the various sensors 80 to 89, the battery voltage and the like via the I / O interface 105 based on the program stored in the ROM 102, and the RAM 103 and the backup RAM 104. Various control amounts are calculated based on various data stored in the memory and fixed data stored in the ROM 102. Then, the drive circuit 107 turns on the fuel pump relay 98 to energize and drive the fuel pump 31, and at the same time, the switching solenoid valves 70, 76, SOL. The ON / OFF signals are output to 1 to 4 and the duty signal is output to the duty solenoid valves 43 and 75 to perform the turbocharger operation number switching control and the supercharging pressure control, which correspond to the calculated fuel injection pulse width. The drive pulse width signal is output to the injector 30 of the corresponding cylinder at a predetermined timing for fuel injection control, and the ignition signal is output to the igniter 36 at a timing corresponding to the calculated ignition time to perform ignition timing control. Then, a control signal is output to the ISCV 25 to execute idle speed control and the like.

Next, the exhaust control valve 53 will be described in detail with reference to FIGS. 1 and 2. First, the exhaust control valve 53 has a tubular valve body 130 that also serves as an exhaust pipe, and this valve body 130 is connected to the lower portion of the turbine housing 50c of the secondary turbocharger 50 by a bolt 145. A valve seat 132 having a valve port 131 having a predetermined diameter is formed in the middle of the valve body 130 in an inclined manner, and a valve shaft 133 is rotatably horizontally installed on a side immediately downstream of the valve seat 132. Then, the disc-shaped valve body 135 is attached to the arm 134 integrated with the valve shaft 133 by the mounting plate 136 so as not to be pulled out. By rotating the valve shaft 133 in the clockwise direction, the valve body 135 is attached to the valve seat 132. The valve body 131 is configured so as to close the valve port 131 and rotate counterclockwise so that the valve body 135 separates from the valve seat 132 and opens downstream in the exhaust flow direction. Here, a predetermined clearance is provided between the arm 134, the valve body 135 and the mounting plate 136, and when the flapper type valve body 135 is fully closed, the entire circumference thereof is in close contact with the valve seat 132 to ensure sealing performance. To be done.

Further, the exhaust control valve actuating actuator 54 is installed so as to be inclined above the exhaust control valve 53 by means of a step 146 that is fastened together with a bolt 145. A rod 141 extending downwardly of the actuator 54 and a lever 141 integral with the valve shaft 133 are connected by a pin 142. When the rod 140 retracts, the valve shaft 133 rotates clockwise, and when the rod 140 projects, the valve shaft 133 extends. Rotate counterclockwise. Further, a stopper 143 is provided on the valve body 130 so as to be engaged with the lever 141 so as to restrict the fully open position.

Next, a chattering sound reduction measure will be described. First, in the pressure operating system of the exhaust control valve 53, as described above, the first exhaust control valve switching solenoid valve SO L. 3 and the second exhaust control valve switching solenoid valve SOL. Have 4. The first exhaust control valve switching solenoid valve SOL. 3 from the control pressure passage 73a to the positive pressure chamber 54a of the actuator 54, the second exhaust control valve switching solenoid valve SOL. The control pressure passages 74a from 4 communicate with the negative pressure chamber 54b, respectively, and when the exhaust control valve 53 is closed, the positive pressure in the positive pressure chamber 54a of the actuator 54 and the negative pressure in the negative pressure chamber 54b are leaked. The chambers 54a and 54b are opened to the atmosphere, and the exhaust control valve 53 is closed by the biasing force of the spring 54c.

Here, regarding the generation of chattering noise when the exhaust control valve 53 is closed, the relationship as shown in FIG. 3 is established. That is, the chattering sound generation time is a decreasing function of the valve closing speed as shown in (c), and the chattering sound generation time is shortened and the chattering sound is reduced by increasing the valve closing speed. The valve closing speed is an increasing function of the nipple diameter at the inlet and outlet of the actuator 54 as shown in (a) and the capacity of the switching solenoid valve as shown in (b). By increasing the nipple diameter and the capacity of the switching solenoid valve, The valve closing speed can be increased. Therefore, the diameters of the control pressure passages 73a and 74a including the nipple are increased from 4 mm to 6.35 mm, and the switching solenoid valve SOL. 3, SOL. The capacity of 4 is increased from 8 l / min to 20 l / min, for example, and the valve closing speed is increased.

Next, the supercharger operating number switching control by the ECU 100 will be described with reference to the flowcharts shown in the turbo switching control routines of FIGS. 6 to 9. This turbo switching control routine is executed every set time (for example, 10 msec) after turning on the ignition switch 97.

When the ECU 100 is powered on by turning on the ignition switch 97, the system is initialized (clearing each flag and each count value), and first, in step S1, the value of the twin turbo mode determination flag F1 is referred to. If the twin turbo mode discrimination flag F1 is cleared, the process proceeds to step S2, and if it is set, the process proceeds to step S60. This twin turbo mode determination flag F1 is cleared when the current control state is the single turbo mode in which only the primary turbocharger 40 is supercharged, and in the twin turbo mode in which both turbochargers 40 and 50 are supercharged. Sometimes set.

In the following description, the single turbo mode will be described first, then the single → twin switching control, and finally the twin turbo mode. Immediately after turning on the ignition switch 97 and when the current control state is the single turbo mode, since F1 = 0, the process proceeds to step S2.

In step S2, a single-to-twin switching determination value Tp2 is set by referring to the turbo switching determination value table based on the engine speed N with compensation calculation. As shown in FIG. 11, in the turbo switching determination value table, from the relationship between the engine speed N and the engine load (in this embodiment, the basic fuel injection pulse width) Tp, the single turbo mode is switched to the twin turbo mode. The single → twin switching judgment line L2 for switching and conversely the twin → single switching judgment line L1 for switching from the twin turbo mode to the single turbo mode are previously obtained by experiments and the single turbo region and the twin turbo region are set. There is. Then, the single → twin switching determination value Tp2 and the twin → single switching determination value Tp1 are stored in advance in a series of addresses in the ROM 102 as a table with the engine speed N as a parameter, corresponding to each line L2, L1. . The single-to-twin switching determination line L2 is set at the point C where the torque curve TQ1 for single turbo and the torque curve TQ2 for twin turbo of the output characteristics of FIG. 16 coincide with each other in order to prevent torque fluctuation during switching. Therefore, as shown in FIG. 11, the load is set to a low load side from a high load in the low and medium speed range to an increase in the engine speed N. In addition, as shown in the figure, in order to prevent control hunting when switching the turbocharger operating number, the twin → single switching determination line L1 is compared to the single → twin switching determination line L2 on the low speed side. The hysteresis H is set to have a relatively wide width.

Then, in step S3, the single-to-twin switching determination value Tp2 is compared with the current basic fuel injection pulse width (hereinafter, engine load) Tp. If Tp <Tp2, the process proceeds to step S4, and the single turbo mode is selected. Take control. If Tp ≧ Tp2, the process proceeds to step S30 to perform single → twin switching control.

When the process proceeds from step S3 to step S4, the value of the supercharging pressure control mode determination flag F2 is referred to. This supercharging pressure control mode determination flag F2 indicates that the present operating region is within the exhaust control valve small opening control mode region in which the supercharging pressure control is performed by the small opening of the exhaust control valve 53 and the secondary turbocharger 50 is preliminarily rotated. When set, cleared when out of range. Therefore, immediately after the ignition switch 97 is turned on, the initial setting is performed, and when the operating region is outside the exhaust control valve small open control mode region during the execution of the previous routine, F2 = 0, so the process proceeds to step S5, and steps S5 and step S5. It is determined whether or not the current operating region has moved into the exhaust control valve small open control mode region by the condition determination in S7.

As shown in FIG. 12, the determination of the shift to the exhaust control valve small open control mode region is made based on the relationship between the engine speed N and the intake pipe pressure (supercharging pressure) P. On the low rotation and low load side of the constant line L2, that is, in the single turbo mode, in a region surrounded by the set values N1 (for example, 2650 rpm) and P1 (for example, 1120 mmHg), and the throttle opening TH is set value TH1 (for example, 30 deg). ) In the following cases, it is judged that the area has moved into the area.

That is, the engine speed N and the set value N1 are compared in step S5, the intake pipe pressure P and the set value P1 are compared in step S6, and the throttle opening TH and the set value TH1 are compared in step S7. To compare. If N <N1, or P <P1, or TH <TH1, the process proceeds to step S8, and it is determined that the current operating region is outside the exhaust control valve small open control mode region, and the boost pressure control mode determination is made. If the flag F2 is cleared, and if N ≧ N1 and P ≧ P1 and TH ≧ TH1, the process proceeds to step S9, and it is determined that the current operation region has shifted to the exhaust control valve small opening control mode region and supercharging. The pressure control mode determination flag F2 is set.

Then, the process proceeds to step S10, and the switching solenoid valves SOL. 1 is turned off, and in step S11, the intake control valve switching solenoid valve SOL. Turn OFF 2. Next, in step S12, the value of the supercharging pressure control mode determination flag F2 is referred to. If F2 = 0, the process proceeds to step S13, in which the first exhaust control valve switching solenoid valve SOL. 3 is turned off, and in step S14, the second exhaust control valve switching solenoid valve SOL. Turn off 4. Then, in steps S15 to S17, the twin turbo mode determination flag F1, the differential pressure search flag F3, which will be described later, and the control valve switching time count value C1 are respectively cleared, and then the routine exits.

Therefore, in the single turbo mode and in the low rotation and low load operation region outside the exhaust control valve small open control mode region, each switching solenoid valve SOL. All of 1 to 4 are turned off. Therefore, the boost pressure relief valve 57 is a switching solenoid valve for the boost pressure relief valve SOL. When the negative pressure from the surge tank 60 is introduced into the pressure chamber by turning OFF the valve 1, the valve is opened against the biasing force of the spring, and the intake control valve 55 changes the intake control valve switching solenoid valve SOL. When 2 is turned off, a negative pressure is introduced into the pressure chamber of the actuator 56, so that the valve is closed against the biasing force of the spring. The exhaust control valve 53 is a switching solenoid valve SOL. When 3 and 4 are turned off, atmospheric pressure is introduced into both chambers 54a and 54b of the actuator 54 to close the valve by the urging force of the spring.

Then, by closing the exhaust control valve 53, the introduction of exhaust gas to the secondary turbocharger 50 is shut off, the secondary turbocharger 50 is deactivated, and only the primary turbocharger 40 is operated. It will be in turbo mode. Further, by closing the intake control valve 55, leakage of supercharging pressure from the primary turbocharger 40 to the secondary turbocharger 50 side via the intake control valve 55 is prevented, and the supercharging pressure is reduced. It is prevented. Note that when in the single turbo mode and outside the exhaust control valve small open control mode range, or in the twin turbo mode, the boost pressure feedback control will not be described in detail here, but the primary waste gate valve 41 Done using only.

On the other hand, if it is determined in step S9 that the current operation region is within the exhaust control valve small open control mode region and the supercharging pressure control mode determination flag F2 is set, steps S10 to S12 are performed. The process proceeds to step S18, where the first exhaust control valve switching solenoid valve SOL. Turn on only 3. Therefore, the first exhaust control valve switching solenoid valve SOL. When 3 is turned on, positive pressure is introduced into the positive pressure chamber 54a of the actuator 54, and the exhaust control valve 53 is opened. In this exhaust control valve small open control mode, the exhaust control valve small open control routine shown in FIG. 10 is executed every set time (for example, 480 msec), so that the exhaust control valve 53 is used to boost pressure. Feedback control is performed, and the exhaust control valve 53 is opened slightly accordingly. That is, referring to the value of the supercharging pressure control mode determination flag F2 in step S100 in FIG. 10, the routine is exited when F2 = 0, and when the exhaust control valve small open control mode is set when F2 = 1, S101, the boost pressure relief valve switching solenoid valve SOL. 1 is determined and the SOL. When 1 = ON, the routine is exited and SOL. When 1 = OFF, the routine proceeds to step S102, where the target supercharging pressure and the actual supercharging pressure detected by the absolute pressure sensor 81 are compared, and according to the comparison result, for example, PI control is used for exhaust control valve small opening control. The ON duty (duty ratio) for the duty solenoid valve 75 is calculated, the duty signal of this ON duty is output to the duty solenoid valve 75, and the boost pressure feedback control is executed. Therefore, the duty solenoid valve 75 regulates the positive pressure acting on the positive pressure chamber 54a of the actuator 54, and as shown in FIG. 14, the exhaust control valve 53 is opened slightly and only the exhaust control valve 53 is used. The supercharging pressure feedback control is performed. Then, a small opening of the exhaust control valve 53 supplies a part of the exhaust gas to the turbine 50a of the secondary turbocharger 50, preliminarily rotates the secondary turbocharger 50, and prepares for a twin turbo transition.

In this state, since the intake control valve 55 is closed, the supercharging pressure is contained between the intake control valve 55 and the blower 50b downstream of the secondary turbocharger 50. The supercharging pressure is leaked by opening the supply pressure relief valve 57 to smooth the preliminary rotation.

When the boost pressure control mode determination flag F2 is set (F2 = 1) in the exhaust control valve small open control mode region under the single turbo mode, the process proceeds from step S4 to step S19, It is determined whether the current operating region has moved out of the exhaust control valve small open control mode region by the condition determination in S19 to S21.

In order to prevent the control hunting at the time of switching the supercharging pressure control mode, the determination of the shift to the outside of this area is performed as shown in FIG. 12, so that the set value N2 lower than the set values N1, P1 and TH1 is set. (For example, 2600 rpm), P2 (for example, 1070 mmHg), and TH 2 (for example, 25 deg). Then, in step S19, the engine speed N and the set value N2 are compared, in step S20, the intake pipe pressure (supercharging pressure) P and the set value P2 are compared, and in step S21, the throttle opening TH and the set value TH2. When N <N2, P <P2, or TH <TH2, it is determined that the current operating region has moved out of the exhaust control valve small open control mode region, and the process proceeds to step S8, where The pressure control mode determination flag F2 is cleared. As a result, the exhaust control valve small opening control is released. If N ≧ N2 and P ≧ P2 and TH ≧ TH2, it is determined that the current operating region is still within the region, and the routine proceeds to step S9, where the supercharging pressure control mode determination flag F2 is set to F2 = 1. The exhaust control valve small open control is continued.

As described above, in the single turbo mode, most of the exhaust gas from the engine body 1 is introduced into the primary turbocharger 40, and the turbine 40a rotationally drives the blower 40b. Therefore, the blower 40b sucks and compresses the air, the compressed air is cooled by the intercooler 20, the flow rate is adjusted by the opening degree of the throttle valve 21, and the high efficiency of charging each cylinder through the chamber 22 and the intake manifold 23. Supplied and supercharged. In the single turbo state in which only the primary turbocharger 40 operates in the single turbo mode, as shown in the output characteristic of FIG. 16, the torque curve TQ1 during single turbo with high axial torque in the low and medium rotation speed regions is shown. Is obtained.

Next, single-to-twin switching control will be described. If it is determined in step S3 that Tp ≧ Tp2, that is, the current operating region has shifted from the single turbo region to the twin turbo region (see FIG. 11), the process branches to step S30 and only the primary turbocharger 40 operates. The single-to-twin switching control for switching from the single turbo state to the twin turbo state in which both turbochargers 40 and 50 are operating is executed.

Then, first, in step S30, the switching solenoid valves SOL. 1 is determined, and in step S32, the first exhaust control valve switching solenoid valve SOL. 3 is determined and the switching solenoid valves SOL. If both 1 and 3 are ON, the process directly proceeds to step S34. Further, each switching solenoid valve SOL. When 1 and 3 are OFF, they are turned ON in steps S31 and S33, respectively, and then the process proceeds to step S34.

Therefore, the supercharging pressure relief valve 57 includes the supercharging pressure relief valve switching solenoid valve SOL. When 1 is turned on, the positive pressure from the positive pressure passage 64a is introduced into the pressure chamber, and the valve is immediately closed by the positive pressure and the biasing force of the spring. Further, the exhaust control valve 53 includes the first exhaust control valve switching solenoid valve SOL. When 3 is turned on, positive pressure is introduced into the positive pressure chamber 54a of the actuator 54 to open the valve. When the exhaust control valve small open control mode under the single turbo mode is switched to the single → twin switching control, the boost pressure relief valve switching solenoid valve SOL. When the exhaust control valve small open control routine of FIG. 10 is turned on by exiting the routine through step S101 without performing the boost pressure feedback control, the exhaust control valve 53 stops the boost pressure feedback control. The duty solenoid valve 75 for exhaust control valve small opening control is fully closed, and the positive pressure through the positive pressure passage 64b is directly leaked to the positive pressure chamber 54a of the actuator 54 without being leaked by the duty solenoid valve 75. Since it is introduced, the opening degree of the exhaust control valve 53 is increased.

The supercharging pressure relief valve 57 is closed to shut off the relief passage 58, and the exhaust control valve 53 is opened and its opening is increased to increase the rotational speed of the secondary turbocharger 50. At the same time, the supercharging pressure between the downstream of the blower 50b of the secondary turbocharger 50 and the intake control valve 55 is gradually increased to prepare for the shift to the twin turbo mode. In step S34, the value of the differential pressure search flag F3 is referred to. If F3 = 0, the process proceeds to step S35, and if F3 = 1, the process jumps to step S39.

At the time of the first routine execution after shifting to the single-to-twin switching control, since F3 = 0, the process proceeds to step S35, and first, the exhaust control valve open delay time setting table is referenced with interpolation calculation based on the vehicle speed V. Then, the exhaust control valve opening delay time that determines the fully open control of the exhaust control valve 53 after switching from the single to twin switching control (turning the second exhaust control valve switching solenoid valve SOL.4 from OFF to ON) T1 is set, and the intake control valve opening delay time setting table is referred to with interpolation calculation based on the vehicle speed V in step S36, and after the exhaust control valve 53 is fully opened, the intake control valve 55 is opened. (Switch control valve switching solenoid valve SOL.2 is turned from OFF to ON) Set the intake control valve opening delay time T2 for determining the condition of the start timing. Further, in step S37, the intake control valve 55 is opened based on the differential pressure between the upstream pressure PU and the downstream pressure PD of the intake control valve 55 (read value of the differential pressure sensor 80) DPS (= PU-PD). The intake control valve opening differential pressure DPSST for setting the control start timing is set.

FIG. 13A shows a conceptual diagram of the exhaust control valve opening delay time setting table, and FIG. 13B shows a conceptual diagram of the intake control valve opening delay time setting table. As shown in the figure, as the vehicle speed V is higher, the exhaust control valve open delay time T1 and the intake control valve open delay time T2 are shortened to fully open the exhaust control valve 53 and open the intake control valve 55. The timing of switching to the twin turbo mode is accelerated, the acceleration response is made uniform regardless of the vehicle speed, and the drivability is improved.

Further, FIG. 13C shows a conceptual diagram of the intake control valve opening differential pressure setting table. As shown in the figure, the difference immediately after the engine operating state shifts from the single turbo region to the twin turbo region (see FIG. 11) with the single → twin switching determination line L2 (single → twin switching determination value Tp2) as a boundary. As the pressure DPS is on the negative side, that is, the downstream pressure PD is higher than the upstream pressure PU of the intake control valve 55, and the intake control valve opening differential pressure DPSST is on the negative side as the supercharging state is higher, The timing of opening the intake control valve 55 is advanced to improve the acceleration response.

After setting the delay times T1 and T2 and the intake control valve opening differential pressure DPSST, the process proceeds to step S38, the differential pressure search flag F3 is set, and the process proceeds to step S39. In step S39, the second exhaust control valve switching solenoid valve SOL. No. 4, the exhaust control valve 53 has already started to be fully opened, and the SOL. 4 = ON and the exhaust control valve full-open control has already been started, the routine jumps to step S47, and the second exhaust control valve switching solenoid valve SOL. 4 is kept ON, and SOL. If 4 = OFF, it means that the exhaust control valve full-open control has not yet been executed, so the routine proceeds to step S40, where the control valve switching time count value C1 is compared with the exhaust control valve opening delay time T1 to shift to single-to-twin switching control. Then, it is determined whether the exhaust control valve opening delay time T1 has elapsed.

If C1 ≧ T1, the process jumps to step S45 and the second exhaust control valve switching solenoid valve SOL. 4 is turned on and the exhaust control valve 53 is fully opened. When the delay time C1 <T1 has not yet elapsed, the routine proceeds to step S41, where the engine load Tp is compared with the value obtained by subtracting the set value WGS from the single-to-twin switching determination value Tp2 set in step S2, and Tp < In the case of Tp2-WGS, the process returns to step S8 to stop the single-twin switching control and immediately switch to the single turbo mode. This is because when the engine load Tp drops, the engine returns to the single turbo mode, so that the driver does not feel uncomfortable.

More specifically, as shown in FIG. 11, once the engine operating state exceeds the single → twin switching determination line L2 (Tp2) from the single turbo region to the twin turbo region side, the twin → single switching determination line is reached. As long as L1 (Tp1) is not exceeded in the single turbo range, the exhaust control valve 53 will be fully opened after the delay time T1 has elapsed (step S45), and the differential pressure DPS will change after the delay time T2 has elapsed. When the pressure reaches DPSST, the intake control valve 55 opens (step S49), and the twin turbo state is switched to. Therefore, if the operating state remains in the area surrounded by the single → twin switching determination line L1 and the single → twin switching determination line L2 after the single → twin switching determination line L2 is exceeded, after the delay time elapses. It will be switched to the twin turbo state. However, in this region, as shown in FIG. 16, the axial torque of the twin turbo torque curve TQ 2 by the operation of the secondary turbocharger 50 is smaller than the axial torque of the single turbo given by the torque curve TQ1. On the contrary, when it becomes low and the turbo mode is switched from the single turbo state to the twin turbo state, a sudden decrease in torque causes a torque shock and gives the driver a feeling of discomfort.

In order to deal with this, it is sufficient to bring the twin → single switching determination line L1 closer to the single → twine switching determination line L2 to narrow the width (hysteresis) of both switching lines. However, between the switching lines L1 and L2. If the width of the surge tank 60 is narrowed, the switching frequency between the single turbo and the twin turbo increases, and the negative pressure capacity of the surge tank 60 as a negative pressure source that operates each control valve becomes insufficient. If the operating condition remains near the single-to-twin switching determination line L2 if the above width is narrowed too much, due to fluctuations in the engine load Tp, which is a parameter for switching the turbocharger operating number, There is an inconvenience that the boost pressure relief valve 57 without setting the switching delay time causes chattering.

In order to prevent these, after the operating state exceeds the single → twin switching determination line L2 to the twin turbo region side, and before the delay time T1 elapses, the interval is narrower than the single → twin switching determination line L2 and the single turbo region. When the single-twin switching determination stop line L3 (= Tp2-WGS) shown by the broken line in FIG. 11 in which only the set value WGS is subtracted to the single turbo region side is crossed to the single turbo region side, single-twin switching control is performed. By discontinuing the operation and immediately shifting to the single turbo mode, and maintaining the single turbo state in which only the primary turbocharger 40 operates, the operation in the low torque region in the twin turbo state is eliminated and the drivability is improved. It

On the other hand, if Tp ≧ Tp2-WGS in step S41, the process proceeds to step S42, and after the transition from the single to twin switching control, is the engine operating state transitioned to the high load high rotational speed range before the delay time T1 has elapsed? The high load determination value TpH for determining the above is set by referring to the high load determination value table with interpolation calculation based on the engine speed N.

FIG. 11D shows a conceptual diagram of the high load judgment value table. The fuel injection pulse width (engine load) Tp is calculated by Tp = K × Q / N K: constant, Q: intake air amount, and when the intake air amount Q is constant at high load, the fuel injection pulse width (Engine load) Tp is inversely proportional to the engine speed N. Therefore, as shown in the figure, the high load determination value TpH is set to a lower value as the engine speed N is higher.

Next, in step S43, the engine load Tp is compared with the high load determination value TpH, and if Tp ≦ TpH, the process proceeds to step S44, the control valve switching time count value C1 is incremented, and the routine is executed. Get out. On the other hand, when Tp> TpH and it is judged that the engine operating state has shifted to the high load and high speed region before the delay time T1 elapses (for example, in the case of sudden acceleration, racing, etc.), In step S45, the second exhaust control valve switching solenoid valve SOL. 4 is immediately turned on, the exhaust control valve 53 is fully opened, and the exhaust gas is also flown to the secondary turbocharger 50 side. Prevent damage.

When the exhaust control valve opening delay time T1 elapses after the shift to the single-to-twin switching control and the process proceeds from step S40 or from step S43 to step S45, the second exhaust control valve switching solenoid valve SOL. 4 is turned on, the exhaust control valve 53 is fully opened, the rotation speed of the secondary turbocharger 50 is further increased, and the compressor pressure (supercharger) between the blower 50b and the intake control valve 55 by the secondary turbocharger 50 is increased. The supply pressure also rises, and as shown in FIG. 14, the differential pressure DPS between the upstream side and the downstream side of the intake control valve 55 rises. Then, the process proceeds to step S46, the control valve switching time count value C1 is cleared to measure the time after the exhaust control valve fully open control, and the process proceeds to step S47.

When the process proceeds from step S39 or step S46 to step S47, the count value C1 representing the time after the exhaust control valve fully open control (SOL.4 OFF → ON) is compared with the intake control valve open delay time T2. , C1 <T2, it is determined that the intake control valve 55 valve opening condition is not satisfied, and the count value C1 is incremented in step S44 to exit the routine. If C1 ≧ T2, it is determined that the valve opening condition is satisfied and the routine proceeds to step S48, where the current differential pressure DPS is compared with the intake control valve opening differential pressure DPSST, and the intake control valve 55 opening timing is determined. Determine if it has been reached.

When DPS <DPSST, it is judged that the valve opening start timing has not been reached, and the routine is exited. When DPS ≧ DPSST, the upstream pressure PU of the intake control valve 55 and the downstream pressure PD become substantially equal, That is, the supercharging pressure by the secondary turbocharger 50 between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 rises and becomes substantially equal to the supercharging pressure by the primary turbocharger 40. It is judged that the intake control valve opening start time has been reached, and the routine proceeds to step S49, where the intake control valve switching solenoid valve SOL. 2 is turned on and the intake control valve 55 is opened.

As a result, supercharging from the secondary turbocharger 50 is started and the twin turbo state is established. Then, the process proceeds to step S50, and when the single-to-twin switching control is completed, the twin turbo mode determination flag F1 is set next time to shift to the twin turbo mode, and the routine is exited. The time chart in Fig. 14 shows the switching state from the single turbo mode to the twin turbo mode by the above single → twin switching control.

As described above, in the single-to-twin switching control, first, the boost pressure relief valve 57 is closed, the exhaust control valve 53 is opened, and the preliminary rotation speed of the secondary turbocharger 50 is increased. The exhaust control valve opening delay time T1 gives the time required to increase the preliminary rotational speed of the secondary turbocharger 50, and after this delay time T1, the exhaust control valve 53 is fully opened. Then, the boost pressure between the blower 50b of the secondary turbocharger 50 and the intake control valve 55 is increased by the secondary turbocharger 50 to increase the differential pressure DPS, and after the exhaust control valve is fully opened, the intake control valve is opened. The delay time T2 compensates for the operation delay time until the exhaust control valve 53 is fully opened, and after the delay time T2 elapses, the differential pressure DPS between the upstream side and the downstream side of the intake control valve 55 becomes the intake control valve opening differential pressure DPSST. The intake control valve 55 is opened when it reaches. As a result, the switching from the single turbo state in which only the primary turbocharger 40 is operating to the twin turbo state in which both turbochargers 40 and 50 are operating is performed smoothly, and the upstream pressure of the intake control valve 55 is further increased. When PU and the downstream pressure PD become substantially equal, the intake control valve 55 is opened to start supercharging from the secondary turbocharger 50. Therefore, the supercharging pressure generated at the time of switching to the twin turbo state. The occurrence of torque shock due to the temporary decrease of the torque is effectively and surely prevented.

Next, the twin turbo mode will be described. If the twin turbo mode determination flag F1 is set by the end of the single-to-twin switching control, or if the twin turbo mode was executed at the previous routine execution, when the routine is executed this time, the routine proceeds from step S1 to step S60 due to F1 = 1. Branch off.

Then, at step S60, the twin-to-single switching determination value Tp1 is set by referring to the turbo switching determination value table with interpolation calculation based on the engine speed N (see FIG. 11), and the routine proceeds to step S61, The engine load Tp is compared with the twin-to-single switching determination value Tp1. If Tp ≧ Tp1, the current operating state is in theinter-region, so the determination value search flag F4 is cleared in step S62, and in step S63. After clearing the single-turbo region duration time count value C2 for counting the single-turbo region duration time after shifting to the single-turbo region, jump to step S72, and switch the boost pressure relief valve for step S72 to step S75. Solenoid valve SOL. 1, intake control valve switching solenoid valve SOL. 2, first and second exhaust control valve switching solenoid valves SOL. 3, 4 are turned on, the supercharging pressure relief valve 57 is closed, the intake control valve 55 and the exhaust control valve 53 are both fully opened, and the twin turbo mode determination flag F1 is set in step S76. After returning to step S17 and clearing the control valve switching time count value C1, the routine is exited.

In the twin turbo mode, by closing the supercharging pressure relief valve 57, opening the intake control valve 55, and fully opening the exhaust control valve 53, in addition to the primary turbocharger 40, the secondary turbocharger 40 The machine 50 starts full-scale operation, becomes a twin-turbo state due to supercharging operation of both turbochargers 40 and 50, and compressed air is supplied to the intake system due to supercharging of both turbochargers 40 and 50. As shown in the output characteristics, the torque curve TQ2 at the time of twin turbo with high shaft torque in the high rotation speed range is obtained.

On the other hand, if Tp <Tp1 is determined in step S61, that is, if it is determined that the current operating state has shifted to the single turbo region (see FIG. 11), the process proceeds to step S64, and the value of the determination value search flag F4 is referred to. , F4 = 0, the process proceeds to step S65, and if F4 = 1, the process jumps to step S67.

The judgment value search flag F4 is cleared in the twin turbo mode and when the engine load Tp is in the twin turbo region when the engine operating condition is within the twin → single switching judgment line L1 (Tp1) (step S62). ). Therefore, after Tp <Tp1, in executing the routine for the first time, the process proceeds to step S65, and the single turbo region continuation time determination value table is referenced with interpolation calculation based on the engine load Tp to set the single turbo region continuation time determination value T4. The set value T4 is a reference value for switching to the single turbo mode in which only the primary turbocharger 40 operates after a predetermined time has elapsed after the engine operating state has changed from the twin turbo region to the single turbo region.

FIG. 13E shows a conceptual diagram of a single turbo region duration determination value table. The single turbo region continuation time determination value T4 set according to the engine load Tp is set to, for example, maximum 2.3 sec and minimum 0.6 sec, and set to a smaller value as the engine load Tp is larger and the load is higher. To be done. As a result, the time it takes for the engine operating state to switch from the twin-turbo region to the single-turbo region and then to switch from the twin-turbo mode to the single-turbo mode becomes faster as the engine load increases, and the part with low axial torque in the twin-turbo condition Driving is prevented and re-acceleration is improved.

Next, after the judgment value search flag F4 is set in step S66, the process proceeds to step S67. Then, in step S67, after counting up the single turbo region duration time count value C2, the determination value T4 is compared with the count value C2 in step S68. If C2 ≧ T4, the process proceeds to step S71 and the count value C2 After clearing, returns to step S8 to switch from twin turbo mode to single turbo mode. As a result, each switching solenoid valve SOL. 1 to 4 are turned off, the supercharging pressure relief valve 57 is opened, and both the intake control valve 55 and the exhaust control valve 53 are closed, so that both turbochargers 40, 50 operate from the twin turbo state. Only the primary turbo supercharger 40 is switched to the single turbo state in which it is operating.

The switching state at this time is shown in a time chart as shown by the solid line in FIG. As described above, the switching from the twin turbo mode to the single turbo mode is performed when the engine operating range is changed from the twin turbo range to the single turbo range (Tp <Tp1) and then the state continues for a set time (C2 ≧ T4). As a result, unnecessary switching of the supercharger due to a temporary decrease in engine speed N due to a shift change or the like is prevented.

On the other hand, if C2 <T4, the process proceeds to step S69, the throttle opening TH is compared with the set value TH3 (for example, 30 deg), and if TH> TH3, the process returns to step S8 through the above step S71, Even after the operating region has shifted to the single turbo region and before that state continues for the set time, the turbocharger relief valve 57 is opened immediately after switching to the single turbo mode as shown by the broken line in FIG. At the same time, the exhaust control valve 53 and the intake control valve 55 are both closed, the supercharging operation of the secondary turbocharger 50 is stopped, and only the primary turbocharger 40 is switched to the single turbo state of supercharging operation. .

The set value TH3 is for determining the acceleration request. That is, in the single turbo region (Tp <Tp1), as shown in the output characteristic of FIG. 16, it is on the low rotation side of the twin → single switching determination line L1, and the region of low axial torque of the torque curve TQ2 during twin turbo. Therefore, if the twin turbo mode is maintained and the twin turbo state is maintained in this state, sufficient acceleration performance cannot be obtained even when the accelerator pedal is depressed. Therefore, when operating in this region, if it is judged that the acceleration is required (TH> TH3), the system immediately shifts to the single turbo mode to enter the single turbo state, and the torque curve of the high shaft torque during the single turbo is obtained. By obtaining TQ1, the acceleration response is improved.

If TH ≦ TH3 in step S69, the process proceeds to step S70, the vehicle speed V is compared with a set value (for example, 2 km / h), and if V> V2, it is determined that the vehicle is running. In step S72, the twin turbo mode is maintained, and if V 2 ≤V2, it is determined that the vehicle is in a stopped state. Then, as in the above, step S71 is performed and the process returns to step S8 to immediately shift to the single turbo mode. .

The above-mentioned set value V2 is for judging the stopped state of the vehicle, and when the vehicle is stopped, for example, in the state of the idling speed, when the accelerator is stepped on and the engine is idle, the engine load Tp increases. At the same time, the engine speed N rises, the engine operating range shifts from the single turbo range to the twin turbo range, the twin turbo state is entered, and the engine load Tp and the engine speed N immediately decrease after the accelerator is released. However, if the engine operating region shifts to the single turbo region again with the twin-to-single switching determination line L1 (see FIG. 11) as a boundary, the set time must not elapse after shifting to the single turbo region (C2 ≧ T4). During this period, as shown in FIG. 15, the engine speed N decreases and the engine speed near the idle speed Ni (example: (For example, around 700 rpm), each switching solenoid valve SOL. The switching of 1 to 4 is performed, and the boost pressure relief valve 57 and the control valves 53 and 55 are switched. At this time, since the engine speed N is low, the background noise due to the engine rotation is low, and the driver hears the noise generated when each valve is switched, which gives the driver discomfort. Therefore, when it is judged that the vehicle is in a stopped state (V ≦ V2), even if the set time has not elapsed after shifting to the single turbo region (C2 <T4), the engine can be immediately switched to the single turbo mode. The switching of each valve is completed before the number of rotations decreases and the background noise decreases, and the discomfort caused by the noise of valve operation is eliminated. The switching state from the twin turbo mode to the single turbo mode at this time is shown by the alternate long and short dash line in FIG.

Further, the operation of the exhaust control valve 53 in the above-described supercharger operating number switching control will be described. First, when the positive pressure chamber 54a and the negative pressure chamber 54b of the actuator 54 are opened to the atmosphere in the single turbo mode and the engine operating region is outside the exhaust control valve small open control mode region, the rod 140 is moved by the spring 54c. The valve shaft 133 is rotated backward by the lever 141 to rotate clockwise. Therefore, the valve body 135 of the exhaust control valve 53 is fully closed due to the clearance of its mounting portion in close contact with the valve seat 132 over the entire circumference and ensuring the sealing property.

In the exhaust control valve small opening control mode, the first exhaust control valve control switching solenoid valve SOL. When positive pressure is introduced into the positive pressure chamber 54a of the actuator 54 by 3, the rod 140 projects a predetermined amount against the biasing force of the spring 54c, and the lever 141 rotates the valve shaft 133 counterclockwise. Therefore, the valve element 135 is separated from the valve seat 132 by the arm 134 and starts to open as shown in FIG. 1. At this time, the positive pressure is regulated by the duty solenoid valve 75, so that the valve element 135 is variably controlled to a small opening. Take a small opening.

Then, when the mode is switched to the twin turbo mode by the single-to-twin switching control, the second exhaust control valve control switching solenoid valve SOL. 4, a negative pressure is introduced into the negative pressure chamber 54b of the actuator 54, the rod 140 is most protruded, the valve shaft 133 is further rotated counterclockwise, and the valve element 135 is separated from the valve seat 132 and fully opened. At this time, the lever 141 comes into contact with the stopper 143 and is restricted to the fully open position.

Further, the twin-turbo mode is changed to the single-turbo mode, and the first and second exhaust control valve control switching solenoid valves SOL. 3, SOL. 4 is switched to the atmosphere port side, the positive pressure in the positive pressure chamber 54a of the actuator 54 and the negative pressure in the negative pressure chamber 54b are both controlled pressure passages 73a and 74a and the switching solenoid valve SOL. 3, SOL. 4, and both chambers 54a and 54b are opened to the atmosphere. Therefore, the rod 54 is retracted again by the spring 54c of the actuator 54, and the exhaust control valve 53 is closed. At this time, immediately before the closing of the exhaust control valve 53, a large exhaust pulsation acts on the valve body 135 as the pressure receiving area increases, so that the valve body 135 vibrates and collides with the valve seat 132 by its clearance. , Chattering sounds are likely to occur.

By the way, the diameters of the control pressure passages 73a and 74a and the switching solenoid valve SOL. 3, SOL. Since the capacity of No. 4 is set large, the positive pressure of the positive pressure chamber 54a of the actuator 54 and the negative pressure of the negative pressure chamber 54b of the actuator 54 rapidly leak, thereby increasing the closing speed of the exhaust control valve 53. Therefore, when the exhaust control valve 53 is closed, the valve element 135 and the valve seat 132 only vibrate and collide for a moment, and the chattering noise generation time becomes extremely short. This makes it impossible for the occupant to recognize this sound, and the chattering sound is substantially reduced.

Although the embodiments of the present invention have been described above, the present invention can also be applied to engines with a supercharger other than the horizontally opposed type.

[0086]

[Effect of device]

 As described above, according to the present invention, the exhaust system to which the secondary turbocharger is connected is provided with a flapper type exhaust control valve that opens downstream, and the positive pressure chamber of the diaphragm type actuator that operates this exhaust control valve. Since the capacity of the switching solenoid valve that switches the control pressure acting on the negative pressure chamber and the control pressure acting on the negative pressure chamber is set to a large value, and it communicates with each chamber of the actuator via the passage with the large diameter of this switching solenoid valve, the exhaust control valve is closed. When the valves are opened, both chambers of the actuator are quickly opened to the atmosphere, the closing speed of the exhaust control valve is increased, and the chattering time is shortened.As a result, the chattering noise when the exhaust control valve is closed is reduced. Becomes difficult to recognize, and the chattering sound can be effectively reduced. Therefore, the occupant's discomfort is eliminated, and the wear of the valve body mounting portion is also reduced. Moreover, the structure is simple because only the diameter of the passage and the capacity of the switching solenoid valve are set large.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a partial cross-section of a main part of an embodiment of an engine with a supercharger according to the present invention.

FIG. 2 is a side view showing an exhaust control valve.

FIG. 3A is a valve closing speed with respect to a nipple diameter, and FIG.
FIG. 4A is an explanatory diagram showing a relationship between a capacity of a switching solenoid valve and a valve closing speed, and FIG.

FIG. 4 is an overall configuration diagram of an engine with a supercharger.

FIG. 5 is a circuit diagram of a control device.

FIG. 6 is a flowchart showing a turbo switching control routine.

FIG. 7 is a flowchart showing a turbo switching control routine.

FIG. 8 is a flowchart showing a turbo switching control routine.

FIG. 9 is a flowchart showing a turbo switching control routine.

FIG. 10 is a flowchart showing an exhaust control valve small opening control routine.

FIG. 11 is an explanatory diagram showing each switching determination value and a relationship between a single turbo region and a twin turbo region.

FIG. 12 is an explanatory diagram of an exhaust control valve small open control mode region.

13A is an exhaust control valve opening delay time setting table, FIG. 13B is an intake control valve opening delay time setting table, FIG. 13C is an intake control valve opening differential pressure setting table, and FIG. A value table, (e) is a conceptual diagram showing a single turbo region duration determination value table, respectively.

FIG. 14 is a time chart showing a switching state from the single turbo mode to the twin turbo mode.

FIG. 15 is a time chart showing a switching state from the twin turbo mode to the single turbo mode.

FIG. 16 is an explanatory diagram showing output characteristics during single turbo and during twin turbo.

[Explanation of symbols]

 1 engine main body 40 primary turbocharger 50 secondary turbocharger 53 exhaust control valve 54 actuator 54a positive pressure chamber 54b negative pressure chamber 73a, 74a control pressure passage SOL. 3 First switching solenoid valve for exhaust control valve SOL. 4 Second exhaust control valve switching solenoid valve

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location 9332-3G F02B 37/12 301 K 9332-3G 301 L

Claims (1)

[Scope of utility model registration request] 1. A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine,
When both are fully open, the secondary turbocharger is supercharged, and when both are fully closed, an intake control valve that stops the supercharger operation of the secondary turbocharger and a flapper-type exhaust control valve that opens downstream are connected to the secondary turbocharger. A diaphragm type actuator, which is provided in each of the intake and exhaust systems connected to the feeder, has a positive pressure chamber and a negative pressure chamber and operates the exhaust control valve, and the positive pressure chamber and the negative pressure chamber of the actuator are provided. A switching solenoid valve for switching the control pressure that acts on is disposed, and the exhaust control valve is closed by opening both chambers of the actuator to the atmosphere by the switching solenoid valve, and negative pressure is applied to the negative pressure chamber.
In a supercharged engine in which an exhaust control valve is valved by supplying positive pressure to a positive pressure chamber, the capacity of the switching solenoid valve is set to a large value, and the switching solenoid valve is connected to the actuator via a passage having a large diameter. An engine with a supercharger, which communicates with each room of.