JP3084136B2 - Exhaust control device for supercharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for a turbocharged engine which operates a plurality of turbochargers in a sequential turbo system as a vehicle engine, and more particularly, to an exhaust control device attached to a secondary turbocharger. To prevent chattering of exhaust control valves.

[0002]

2. Description of the Related Art In recent years, as a supercharged engine for a vehicle, a multi-cylinder exhaust system is equipped with a primary and secondary turbocharger in parallel, and the turbocharger is operated in a sequential turbo system. Things have been suggested. In this sequential turbo system, the primary turbocharger is configured to be able to constantly supercharge, and an exhaust control valve, an intake control valve, a supercharging pressure relief valve, and the like are provided on the secondary turbocharger side. And, for example, operating only the primary turbocharger in single turbo mode in the low speed range,
In the twin-turbo mode in the high-speed range, the secondary turbocharger is first preliminarily rotated, and then both turbochargers are operated to obtain an optimum engine output characteristic according to the traveling state. Here, the actuator of each control valve described above operates using negative pressure, positive pressure and atmospheric pressure of the intake system in consideration of safety and durability against high heat of the supercharger.

[0003] The exhaust control valve of the secondary turbocharger is operated to be fully closed or fully opened under the influence of exhaust gas, and there are two types, an upstream opening and a downstream opening. In the upstream opening method, since the exhaust pressure acts in the closing direction, the controllability and responsiveness when operating the secondary turbocharger by opening the exhaust control valve are poor. This is advantageous because the exhaust pressure acts in the opening direction. Therefore, it is desirable to adopt a downstream opening method.However, in this method, it is important to keep the valve fully closed against the exhaust pressure.In the structure using the spring force, the spring pulsation and turbo vibration cause The force may also fluctuate and chatter may occur. Therefore, the exhaust control valve and its actuator are required to be configured so as to improve the operability when closing and to prevent chattering when fully closed.

Conventionally, the above-mentioned sequential turbo type engine with a supercharger is disclosed in, for example,
There is a prior art in Japanese Patent Publication No. Here, an actuator having a pressure chamber with a spring is connected to the exhaust cut valve of the secondary turbocharger, a negative pressure is introduced into the pressure chamber, the pressure chamber is closed, and the pressure chamber is opened to the atmosphere and opened. It is shown to be.

[0005]

In the above prior art, the exhaust cut valve is maintained in the fully closed state only by the negative pressure against the spring force of the actuator. May cause chattering due to lack of data. On the other hand, when the negative pressure is increased, there is a problem in that the actuator is enlarged and the outfitting is restricted.

SUMMARY OF THE INVENTION The present invention has been made in view of this point, and is compact and compact when an exhaust control valve of a secondary turbocharger is configured to be a downstream opening type in a sequential turbocharged engine with a turbocharger. An object of the present invention is to provide a reliable opening / closing operation in which chattering or the like is prevented.

[0007]

In order to achieve the above object, the present invention provides a primary turbocharger in which a primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine. The turbocharger is configured to operate at all times, the secondary turbocharger having a downstream-opening exhaust control valve at least on the turbine side, and in a supercharged engine configured to operate only in the twin turbo mode. An exhaust control valve is provided on the turbine housing side of the secondary turbocharger, and an actuator is mounted in the vicinity by a bracket, and the actuator supplies atmospheric pressure to one chamber and negative pressure to the other chamber to control exhaust. The valve is configured to be closed and open by supplying a negative pressure to one chamber and a positive pressure to the other chamber.

[0008]

According to the above construction, in the single turbo mode during the operation of the engine, the exhaust control valve is closed by the negative pressure of the actuator or the like, and is kept in a tightly closed state so as to prevent chattering or the like. In the twin turbo mode, the exhaust control valve is opened in the downstream direction by the negative pressure and the positive pressure of the actuator, and is reliably maintained in the open state.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2, the overall configuration in the case where primary and secondary turbochargers are mounted on a horizontally opposed engine as a supercharged engine will be described. Reference numeral 1 denotes an engine body of a horizontally opposed engine, in which a combustion chamber 5, an intake port 6, an exhaust port 7, a spark plug 8, a valve mechanism 9, and the like are provided in left and right banks 3, 4 of a crankcase 2. I have. In addition, primary and secondary turbochargers 40 and 50 are disposed near the left and right banks 3 and 4 by this engine structure, respectively. As an exhaust system, a common exhaust pipe 10 from the left and right banks 3, 4 is communicated with turbines 40a, 50a of both turbochargers 40, 50, and an exhaust pipe 11 from the turbines 40a, 50a is connected to one exhaust pipe 12. Merge into catalytic converter 13 and muffler 14
Is communicated to.

As an intake system, intake pipes 16 and 17 branched from the air cleaner 15 into two pipes are connected to blowers 40b and 50b of both turbochargers 40 and 50, respectively, and the intake pipes 18 and 17 from the blowers 40b and 50b are connected. 19 is communicated with the intercooler 20. And intercooler 20
From the chamber 22 via a throttle valve 21, and from the chamber 22 via an intake manifold 23 to each cylinder of the left and right banks 3, 4. Further, as an idle control system, an idle control valve 25 and a check valve 26 that opens with a negative pressure are provided in a bypass passage 24 directly downstream of the air cleaner 15 and the intake manifold 23, and the throttle valve is fully closed when idling and when decelerating. Sometimes the amount of intake air is controlled.

As a fuel system, an injector 30 is provided near a port of the intake manifold 23, and a fuel pump 3
A fuel passage 33 from a fuel tank 32 having a filter 1 and a fuel pressure regulator 35 communicates with the injector 30. The fuel pressure regulator 35 regulates the fuel pressure supplied to the injector 30 at a constant level with respect to the intake pressure, and controls the fuel injection by the pulse width of the injection signal. It is possible to do. The ignition system is connected so that an ignition signal from the igniter 36 is input to the ignition plug 8 as an ignition system.

Next, the control system of the primary turbocharger 40 will be described. Exhaust gas is always introduced into the turbine 40a to operate it, and during load operation when the throttle valve 21 is open, pressurized air is supplied from the blower 40b. It has become. Diaphragm type actuator 4 on turbine side
2 is provided. A control pressure passage 44 having a duty solenoid valve 43 is provided in the pressure chamber of the actuator 42 from above and downstream of the blower 40b.
The control pressure is generated by leaking the supercharging pressure in 3 and acts on the actuator 42 to control the supercharging pressure by increasing or decreasing the opening of the waste gate valve 41. Here, for example, when the duty ratio is large, the control pressure decreases due to the increase in the leak amount, the opening degree of the waste gate valve 41 is reduced, and the supercharging pressure is increased. Conversely, when the duty ratio decreases, the opening degree is increased at a high control pressure, and the supercharging pressure is reduced.

On the other hand, since the supercharging is always possible, if the throttle valve 21 is suddenly closed during deceleration, the blower 40
The pressurized air is confined on the downstream side of b, and a high load in this case is applied to the turbocharger 40, and a sigh-like noise is generated. For this reason, a leak passage 46 having a relief valve 45 is provided between the upstream and downstream of the blower 40b. The relief valve 45 is configured to be closed by a spring and opened by a negative pressure. At the time of the above-described deceleration, the relief valve 45 is opened by the manifold negative pressure to leak the enclosed pressurized air, thereby preventing the generation of the abnormal noise.

The control system of the secondary turbocharger 50 will be described. The waste gate valve 51 similar to that on the primary side controls the supercharging pressure separately by a control pressure passage 54 having an actuator 52 and a duty solenoid valve 53. Is provided. An exhaust control valve 55 having a diaphragm actuator 56 is provided in the exhaust pipe 10 upstream of the turbine 50a, and an intake control valve 58 having a similar actuator 57 is provided downstream of the blower 50b. A relief passage 59 provided with a supercharging pressure relief valve 60 is communicated between the upper and lower portions.

The operation control system of each of these valves will be described. A passage 61 from the intake manifold 23 has a check valve 62 and is connected to a surge tank 63 to store a negative pressure when the throttle valve is fully closed and to generate a pulsating pressure. It is designed to buffer. In one spring chamber of the supercharging pressure relief valve 60, a negative pressure passage 64 from the surge tank 63 and a positive pressure passage 65 by the supercharging pressure downstream of the intake control valve 58 are connected to the switching solenoid valve 70 and the passage 66. And is opened by applying a negative pressure by an electric signal and closed by applying a positive pressure.

The actuator 57 of the intake control valve 58 is
A positive pressure is always applied to one of the chambers by the positive pressure passage 67, and the positive pressure passage 65 and the negative pressure passage 64 are connected to the spring chamber via a switching solenoid valve 71 and a passage 68. Then, a negative pressure is applied to the spring chamber by an electric signal to close the intake control valve 58, and the intake control valve 58 is opened by a spring force when both chambers are set to a positive pressure. The actuator 56 of the exhaust control valve 55 has a second chamber for switching between atmospheric pressure and negative pressure in one chamber.
The switching solenoid valve 74 is communicated via a passage 69, and a first switching solenoid valve 73 for switching between positive pressure and negative pressure is communicated via a passage 75 with the other chamber. The exhaust control valve 55 is closed by applying atmospheric pressure to one chamber and negative pressure to the other chamber by an electric signal to close the exhaust control valve 55, and applying negative pressure to one chamber and positive pressure to the other chamber. Open 55.

A description will be given of various sensors. A differential pressure sensor 80 is provided to detect a differential pressure between upstream and downstream of the intake control valve 58, and an absolute pressure sensor 81 is controlled by a switching solenoid valve 76 to detect the intake pipe pressure. It is provided to select and detect the atmospheric pressure. Further, a crank angle sensor 82, a knock sensor 83, and a water temperature sensor 84 are provided on the engine body 1, and a cam angle sensor 85 is provided opposite to a cam rotor (not shown) connected to a cam shaft of the valve mechanism 9; 10 is provided with an O2 sensor 86 and the throttle valve 21 is provided.
A throttle opening sensor 87 is provided in the air cleaner 15, and an intake air amount sensor 88 is provided immediately downstream of the air cleaner 15.

Referring to FIG. 3, the overall configuration of the electronic control system will be described. First, the control unit 100 controls the I / O
101, CPU 102, RAM 103, backup R
It has an AM 104, a ROM 105, and a constant voltage circuit 106, and processes signals. Also, the ignition switch 9
0, the relay 91 is turned on to supply power from the battery 92 to the constant voltage circuit 106, and the driving circuit 107
3 is turned on to drive the fuel pump 31 by energization. I
/ O101 receives signals from various sensors 80 to 88,
From the drive circuit 107, various switching solenoid valves 70, 7
1, 73, 74, 76, the duty signal to the duty solenoid valves 43, 53, the injector 3
It is configured to output an injection signal to 0, a control signal to the idle control valve 25, and an ignition signal to the igniter 36.

Here, as shown in FIG. 4 (a), the CPU 102 determines the low-load, low-load condition based on the relationship between the secondary turbocharger operation start set values Nb, Nc and the basic fuel injection amount set value Tps at high and low loads. In the case of medium speed and high load low speed, the single turbo mode is determined. And the switching solenoid valve 7
An open signal is output to 0 to open the supercharging pressure relief valve 60 to leak the supercharging pressure downstream of the blower on the secondary side. At the same time, a closing signal is output to the first and second switching solenoid valves 73 and 74 to close the exhaust control valve 55, shut off exhaust gas from being introduced into the secondary turbocharger 50, and change the solenoid valve 71 for switching. , The intake control valve 58 is closed, the secondary turbocharger 50 is deactivated, and the primary turbocharger 40 is brought into an independent operation state.

If the above conditions are not satisfied, the twin turbo mode is determined, and the preliminary rotation mode is determined at the beginning of this mode. In the preliminary rotation mode, first, a closing signal is output to the switching solenoid valve 70 to close the boost pressure relief valve 60, and then the first and second switching solenoid valves 73, 7
4 to open the exhaust control valve 55, and further output an open signal to the switching solenoid valve 71 to output the intake control valve 58.
Are opened and closed sequentially with delay. As a result, the exhaust gas is introduced into the secondary turbocharger 50 and preliminarily rotated, and thereafter substantially shifts to the twin turbo mode.

In each mode, the target supercharging pressure Pt is set to an appropriate height in the single turbo range and to the proper boost pressure in the twin turbo range as shown in FIG. 3B, for example, by the engine speed N and the basic fuel injection amount Tp. Determine a higher appropriate height. Then, a deviation Δp between the target supercharging pressure Pt and the actual supercharging pressure Pb of the absolute pressure sensor 81 is calculated, and a correction amount according to the deviation Δp is determined. Therefore, in the single turbo mode, a duty signal corresponding to the correction amount is output to the primary-side duty solenoid valve 43, and the primary turbocharger 40 is controlled by the opening degree of the waste gate valve 41.
Variable the supercharging pressure. In the twin turbo mode, a duty signal based on the operation distribution of both turbochargers 40 and 50 is output to primary and secondary duty solenoid valves 43 and 53, and both turbochargers are operated by opening the waste gate valves 41 and 51. The supercharging pressures 40 and 50 are respectively varied, and thus the feedback control is performed so that the actual supercharging pressure Pb always follows the target supercharging pressure Pt.

Referring to FIG. 1, the exhaust control valve 55 will be described in detail. First, the secondary turbocharger 50
A turbine housing 50d and a blower housing 50e are connected to both sides of the center housing 50c,
Immediately after the right bank of engine body 1, blower housing 5
0e is mounted substantially horizontally in the front-rear direction of the vehicle body facing forward. The valve body 55a of the exhaust control valve 55 is fastened to the lower part of the turbine housing 50d by bolts 110, and the brackets 110 including the actuators 56 are fastened together by the bolts 110. In this way, the actuator 56 is installed obliquely from the lower rear valve body 55a to the front blower housing side in a state of being close to the secondary turbocharger 50.

The exhaust control valve 55 is configured to open downstream, and a wide valve chamber 55d is formed downstream of the valve port 55b of the valve body 55a via a valve seat 55c.
A valve shaft 55e is provided horizontally at the lower portion inside the valve body 55d, and a valve body 55f having a larger diameter than the valve port 55b comes into contact with and separates from the valve seat 55c on an arm 55g integral with the valve shaft 55e.
5b is opened and closed.

In the actuator 56, the inside of a case 56a is divided into two chambers 56c and 56d by a diaphragm 56b.
The diaphragm 56b is connected to a valve shaft 55e via a rod 56e and a lever 56f, and a spring 56g is urged in the valve closing direction of the diaphragm 56b. One of the chambers 56c communicates with a second switching solenoid valve 74 via a passage 69, and the other chamber 56d communicates with a first switching solenoid valve 73 via a passage 75.

Next, the operation of this embodiment will be described. First, when the engine is operated, for example, in a single turbo mode with a low load and a medium speed, the atmospheric pressure A is applied to one chamber 56c of the actuator 56 by the second switching solenoid valve 74 by the electric signal from the control unit 100, and the first switching is performed. A negative pressure (-P) is supplied to the other chamber 56d by the solenoid valve 73 for use. Then, the rod 56e moves upward in the figure by the force obtained by adding the negative pressure of the diaphragm 56b and the spring force, and the arm 55g of the exhaust control valve 55 swings downward in the figure by the lever 56f. The valve port 55b is closed by contacting the valve port 55c. In this case, the valve body 55f is firmly brought into contact with the valve seat 55c due to the negative pressure or the like, so that the valve body 55f is securely held in a closed state. At this time, even if exhaust pulsation or vibration acts on the valve body 55f, chattering is prevented from occurring.

Next, in the twin turbo mode at a high speed, a negative pressure (-P) is applied to one chamber 56c of the actuator 56 by the second switching solenoid valve 74 by an electric signal from the control unit 100 in the preliminary rotation mode. Positive pressure (+ P) is applied to the other chamber 56d by the first switching solenoid valve 73.
Are supplied respectively. Then, the rod 56e is moved downward in the drawing by the force obtained by adding the negative pressure and the positive pressure of the diaphragm 56b, and the arm 55g of the exhaust control valve 55 is swung about 90 degrees upward in the opposite drawing by the lever 56f. Therefore, the valve element 55f moves away from the valve seat 55c in the downstream direction, and the valve chamber 5
The valve port 55b is opened and reliably held in the open state by retreating from the flow of exhaust gas inside 5d. For this reason, the exhaust E flows from the valve port 55b to the valve chamber 55.
The secondary turbocharger 50 is introduced into the turbine housing 50d of the secondary turbocharger 50 through d, and is preliminarily rotated. Thereafter, the secondary turbocharger 50 is substantially operated.

Although the embodiment of the present invention has been described above, the link mechanism of the exhaust control valve 55 is not limited to this.

[0028]

As described above, according to the present invention,
In the engine with the sequential turbocharger, since the actuator of the exhaust control valve of the downstream opening type provided on the turbine side of the secondary turbocharger is configured to close with a force obtained by adding the negative pressure and the spring force, It is firmly held in the closed state, and chattering due to exhaust pulsation or the like can be completely avoided. This causes noise,
Damage to the exhaust control valve, exhaust leakage, and the like can be reduced. Further, since the exhaust control valve is configured to be opened by the sum of the negative pressure and the positive pressure of the actuator, the open state can be reliably maintained.

Since the exhaust control valve is fixed to the turbine housing and the actuator is mounted in the vicinity thereof, the structure becomes compact. Since the actuator is connected to the valve body of the exhaust control valve by a link mechanism, the operability is good and the actuator is compact.

[Brief description of the drawings]

FIG. 1 is a partially sectional side view showing an embodiment of an exhaust control device for a supercharged engine according to the present invention.

FIG. 2 is a configuration diagram showing the entire supercharged engine.

FIG. 3 is an overall circuit diagram of a control system.

FIG. 4 is a diagram showing a map of each turbo mode and a target supercharging pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 10, 11, 12 Exhaust pipe 16, 17, 18, 19 Intake pipe 40 Primary turbocharger 50 Secondary turbocharger 55 Exhaust control valve 56 Actuator 73, 74 Switching solenoid valve

Claims (3)

(57) [Claims] 1. A primary turbocharger and a secondary turbocharger are arranged in parallel in an intake and exhaust system of an engine, and the primary turbocharger is configured to operate constantly, and a secondary turbocharger is provided. In a turbocharged engine having at least a downstream-opening exhaust control valve on the turbine side and configured to operate only in the twin turbo mode, the exhaust control valve is disposed on the turbine housing side of the secondary turbocharger. An actuator is mounted in the vicinity by a bracket, the actuator supplies atmospheric pressure to one chamber and negative pressure to the other chamber, closes the exhaust control valve, and applies negative pressure to one chamber to the other chamber. An exhaust control device for a supercharged engine, wherein the exhaust control device is configured to supply and open a positive pressure. 2. An actuator of the exhaust control valve, wherein one of the chambers has a second switching solenoid valve for switching between atmospheric pressure and negative pressure, and the other chamber has a first switching solenoid valve for switching between negative pressure and positive pressure. 2. The exhaust control device for a supercharged engine according to claim 1, wherein the exhaust control device is connected to each of the valves. 3. The exhaust control valve is configured to open and close a valve body by moving an arm integrally with a valve shaft in a valve chamber downstream of a valve port so that the valve body contacts and separates from the valve port. The exhaust control device for a supercharged engine according to claim 1, wherein a rod from an actuator is connected to the valve shaft via a lever.