JPH0744736Y2 - Supercharging pressure controller for 2-stage turbocharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a supercharging pressure control device in a two-stage turbocharged engine in which two turbochargers of a high pressure stage and a low pressure stage are connected in series.

[Conventional technology]

As described in Japanese Utility Model Laid-Open No. 62-119435, the bypass valve of the exhaust bypass passage that bypasses the high pressure turbocharger is opened when the engine is not accelerated,
It is known that pumping loss is reduced by suppressing an increase in exhaust pressure to prevent deterioration of fuel efficiency of an engine.

[Problems to be solved by the device]

Generally, it is not necessary to raise the supercharging pressure to the normal target value in the partial load region other than during acceleration. From the viewpoint of fuel consumption rate, the exhaust bypass valve is opened to reduce exhaust resistance (pumping loss). It can be said that it is better to reduce it.
However, in this case, considering the accelerating property, it takes a considerable amount of time to accelerate the high-pressure stage turbocharger from a stopped state to a high rotation speed at which sufficient supercharging can be achieved. In the bypassed condition, the acceleration response of the engine becomes very poor.
The present invention aims to satisfy both contradictory requirements of improvement of fuel efficiency and acceleration, that is, improvement of fuel efficiency at light load without impairing acceleration performance.

[Means for Solving the Problems]

The supercharging pressure control device of the two-stage turbocharging engine of the present invention is
In a two-stage turbocharged engine having a low-pressure turbocharger that pressurizes intake air and a high-pressure turbocharger that further pressurizes the air pressurized in the low-pressure turbocharger and sends it to the engine, in a high-pressure turbine, Two pressure chambers for introducing control pressure are provided in the actuator for operating the exhaust bypass valve that opens and closes the exhaust bypass passage provided in the first pressure chamber, and the first pressure chamber is provided with an excess pressure until the engine load reaches the set value. Supply pressure is relatively low first
In order to maintain the target value of, the pressure downstream of the high-pressure compressor is introduced as the control pressure, and when the load exceeds the set value, the boost pressure is maintained until the pressure downstream of the low-pressure compressor reaches the predetermined target value. Is maintained at a relatively high second target value, switching means for introducing a low pressure such as atmospheric pressure as a control pressure is provided, and a pressure downstream of the high pressure stage compressor is introduced into the second pressure chamber. It is characterized by

[Action]

According to the present invention, the actuator for operating the exhaust bypass valve that opens and closes the exhaust bypass passage of the high-pressure turbine is provided with two pressure chambers, and the first pressure chamber first has a high-pressure stage at a light load. Pressure downstream of the compressor is introduced. At low engine speeds, the pressure in the high-pressure stage compressor rises mainly due to the operation of the high-pressure stage turbocharger, but when the supercharging pressure exceeds the relatively low first target value, the actuator operates and the exhaust bypass valve opens. Since the degree of rotation increases and the rotation speed of the high-pressure stage turbocharger does not increase, the supercharging pressure is maintained substantially at the first target value. As a result, the exhaust pressure is reduced and the pumping loss is reduced, but since the high-pressure stage turbocharger is rotating while maintaining an appropriate speed, it can respond immediately when it starts to accelerate.

Next, when the load becomes a high load exceeding the set value even at low and medium speeds, the control pressure introduced into the first pressure chamber of the actuator is switched to a low pressure such as atmospheric pressure by the switching means. As a result, the exhaust bypass valve moves in the closing direction, and the amount of exhaust gas passing through the high-pressure stage turbine increases, so that the high-pressure stage turbocharger already in the run-up state suddenly accelerates and the boost pressure immediately rises. When the supercharging pressure reaches the relatively high second target value, the actuator increases the opening degree of the exhaust bypass valve due to the pressure downstream of the high-pressure turbine introduced into the second pressure chamber of the actuator. The rotation speed of the high-pressure turbocharger does not increase, and the boost pressure is maintained at the second target value. This allows the engine to be highly supercharged to produce high torque and adequately accommodate the increased load.

At medium and high speeds of the engine, the rotation speed of the low-pressure stage turbocharger becomes high, and the pressure downstream of the low-pressure stage compressor reaches a predetermined target value (corresponding to the second target value of boost pressure).
Then, the switching means is activated again to introduce the pressure downstream of the high pressure stage compressor into the first pressure chamber of the actuator. In this state, the pressure downstream of the low-pressure stage compressor has reached a height corresponding to the second target value of the boost pressure as described above, so the actuator moves the exhaust bypass valve to the fully open position all at once. , The high-pressure stage turbocharger is set to the bypass state, and the low-pressure stage turbocharger is used alone to shift to the first-stage supercharging.

〔Example〕

In FIG. 1 showing an embodiment of the present invention, 1 is an engine that is supercharged, 2 is its exhaust passage, 3 is a small capacity exhaust turbine of a high pressure stage, 4 is its exhaust passage, and 5 is a large capacity of a low pressure stage. An exhaust turbine 6 is a low-pressure stage large-capacity compressor, which is connected to the exhaust turbine 5 by a rotary shaft to form a low-pressure stage turbocharger L. Reference numeral 7 is an air supply passage for the air pressurized by the low-pressure stage compressor 6, and 8 is a high-pressure stage small-capacity compressor, which is connected to the exhaust turbine 3 by a rotary shaft to form a high-pressure stage turbocharger H. Reference numeral 9 is an air supply passage for air compressed by a high-pressure compressor, and 10 is an electronic control unit (ECU) that controls the supercharging pressure of a two-stage turbocharged engine having the above-mentioned structure. The details will be described later.

In the exhaust passage 2 through which the exhaust gas of the engine 1 flows, an exhaust bypass passage 21 for the high-pressure turbine 3 is provided in a branched manner, and an exhaust bypass valve 22 for controlling the opening and closing of the exhaust bypass passage 21 is arranged. The first actuator 23 provided for operating the valve includes a rod 23c penetrating the front wall of the first actuator 23 and a diaphragm (or bellows) 23d attached to the right end of the rod 23c.
The diaphragm has a first chamber 23a communicating with the atmosphere in the actuator 23 and a second chamber 23b supplied with a control pressure.
It is divided into (first pressure chamber), and the compression spring 23e is inserted in the first chamber 23a to urge the bypass valve 22 in the valve closing direction. A second actuator 25 is attached in series behind the first actuator 23, and a left end of a rod 25c penetrating a front wall of the second actuator 25 is in contact with a right end of the rod 23c of the first actuator 23. . At the right end of the rod 25c, a diaphragm (or bellows) 25d that divides the inside of the actuator 25 into a first chamber 25a communicating with the atmosphere and a second chamber 25b (second pressure chamber) to which a control pressure is supplied is attached. A compression spring 25e is inserted in the one chamber 25a.
In this case, the strength of the compression spring 25e is made larger than that of the compression wire 23e.

In the exhaust passage 4, an exhaust bypass passage 41 for the low-pressure turbine 5 is provided in a branched manner, and a waste gate valve 42 for controlling the opening / closing of the exhaust bypass passage 41 is arranged. The actuator 43 provided for operating the valve has a rod 43c penetrating the front wall thereof and a diaphragm (or bellows) 43d attached to the right end of the rod, the diaphragm communicating the inside of the actuator 43 with the atmosphere. It divides into the 1st chamber 43a which exists and the 2nd chamber 43b to which control pressure is supplied, and the compression spring 43e is inserted in the 1st chamber 43a. 51 is the low-pressure stage turbine 5
Reference numeral 61 denotes an exhaust pipe for discharging the exhaust gas from the air supply pipe, and 61 is an air supply pipe for supplying fresh air to the low-pressure stage compressor 6 via an air cleaner (not shown).

In the air supply passage 7 for discharging the air pressurized by the low-pressure stage compressor 6, a supply air bypass passage 71 for the high-pressure stage compressor 8 is provided in a branched manner, and an air supply bypass valve 72 for controlling opening / closing of the air supply bypass passage 72 is arranged. . An actuator 73 provided to operate the valve has a rod 73c penetrating a lower end wall thereof and a diaphragm (or bellows) 73d attached to an upper end of the rod, and the diaphragm controls a pressure inside the actuator 73. Is supplied to the first chamber 73a and a second chamber 73b to which another control pressure is supplied.
A compression strip 73e is inserted in 3b.

A pipe 96 is connected to the air supply passage 9, and its pressure P ₃ is supplied as a control pressure to the second chamber 25b of the actuator 25 described above, and a pipe 92 is connected to the air supply passage 9 and its pressure is increased. P ₉
Is supplied to the electromagnetic three-way valve 93 described above. Electromagnetic three-way valve 93
Supplies either the pressure P ₃ or the atmospheric pressure to the second chamber 23b of the actuator 23 as a control pressure.

Further, the pressure P ₇ in the air supply passage 7 is taken out by a pipe 74 and supplied to an electromagnetic three-way valve 75, which controls either the pressure P ₇ or the atmospheric pressure (or a negative pressure by a vacuum pump or the like). The pressure is supplied to the first chamber 73a of the actuator 73 as a pressure, and the pressure P _{9 in} the air supply passage 9 is taken out by the pipe 98 and supplied to the electromagnetic three-way valve 97, which in turn supplies the pressure P ₉ Alternatively, either the atmospheric pressure or the atmospheric pressure is supplied to the second chamber 73b of the actuator 73 as a control pressure.

Second chamber 43b of actuator 43 of wastegate valve 42
Is connected to the electromagnetic three-way valve 14 by a pipe 15, and the charge air cooler
The pressure P ₁ or the atmospheric pressure of the air supply passage 12 such as the air supply manifold after 91 is received as a control pressure. In this case, in order to further secure the effect, a negative pressure can be used instead of the atmospheric pressure.

The control output signal of the ECU 10 is output from the output port 102 to the drive circuit D.
Is transmitted to the electromagnetic three-way valves 14, 75, 93, 97, etc. via. Needless to say, these electromagnetic three-way valves, which are switching means for the control system, can be replaced with pneumatic three-way valves or the like that perform similar operations.

11 is the engine speed sensor, 13 is the same load sensor, 76
Is a pressure sensor for detecting the pressure P ₇ in the air supply passage 7,
If necessary, these inputs the detection value to the input port 101 of the ECU 10 via the A / D converter.

Next, the operation of the embodiment shown in FIG. 1 will be described.

First, when the load is light, based on the value detected by the load sensor 13,
The ECU 10 operates the solenoid valve 93 to introduce the outlet side pressure P ₉ of the high-pressure compressor 8 into the second chamber 23b which is the pressure chamber of the actuator 23 through the pipe 92. In the low speed range of the engine 1, the flow rate of the exhaust gas flowing through the exhaust passage 2 is small, the low pressure stage turbocharger L is almost inactive, and the high pressure stage turbocharger H has a small capacity, but the supply pressure P ₉ is also generally at a low level. is there. Therefore, in actuator 23,
In the actuator 25, the spring 25e pushes the diaphragms 23d and 25d to the right, and the rods 23c and 25c move to the right, so the exhaust bypass valve 22 is fully closed and the exhaust passage 2 All the exhaust gas of the engine 1 flowing in flows into the high-pressure stage turbine 3, mainly operates the high-pressure stage turbocharger H, and pressurizes the supply air by the high-pressure stage compressor 8.

Also in the air supply bypass valve 72, the atmospheric pressure (or negative pressure) is introduced into the first chamber 73a of the actuator 73 and the air supply passage 9 is introduced into the second chamber 73b due to the positions of the three-way valves 75 and 97. Since the pressure P ₉ is introduced, the diaphragm 73d
The rod 73c is lowered by receiving the bias of the spring 73e, the air supply bypass valve 72 is closed, and all the air supply is pressurized by the high pressure stage compressor 8.

As the rotation speed of the engine 1 increases, the rotation speed of the high-pressure turbocharger H increases, and the value of the pressure P _{9 in} the air supply passage 9 also rises (between 0 and A in FIG. 2). Since the pressure P ₉ is introduced into the second chamber 23b of the actuator 23, and the spring 23e that opposes this pressure is relatively weak,
When the load increases to about R ₁ and the engine speed also rises a little, the pressure P _{9 in} the second chamber 23b overcomes the spring 23e and begins to open the exhaust bypass valve 22 to release the exhaust gas to the bypass passage 21 of the turbine 3. Therefore, the rotation speed of the high-pressure stage turbocharger H has reached a ceiling, the outlet side pressure P ₉ of the high-pressure stage compressor is also suppressed to a relatively low value, and the final supercharging pressure P ₁ is the first target value P _1a. Is held (between FIG. 2A and C).

In a high load state in a low / medium speed range in which the detection value of the load sensor 13 exceeds the set value R ₂ , the ECU 10 switches the three-way valve 93 to introduce atmospheric pressure into the second chamber 23b of the actuator 23. As a result, the exhaust bypass valve 22 moves in the closing direction, and this time, the pressure P _{9 in} the second chamber 25b of the actuator 25 and the spring 25e.
The open / close position will be determined by the balance with 23e. Therefore, the exhaust bypass valve 22 operates so that the boost pressure P ₁ is maintained at the higher second target value P _1b (FIG. 2, C-B-D). First target value P _1a of boost pressure
Is suitable to be about one half of the second target value P _1b .

When the engine 1 is accelerated and the amount of exhaust increases, the low-pressure turbocharger L also begins to operate effectively, so the supply pressure P ₇ of the supply passage 7 gradually rises, and the center of supercharging action is Moving from the high pressure turbocharger H to the low pressure turbocharger L. The pressure P _{7 in the} air supply passage 7 is increased by the low-pressure compressor 6 and is maintained at a constant pressure P ₉
From the pressure sensor 76 that detects the pressure
In response to the input signal entering the input support 101 through the A / D converter, the ECU 10 outputs a control output signal from the output port 102, and the drive circuit D switches the passage of the three-way valve 93 to the second chamber 23b of the actuator 23. Since the supply pressure P ₉ is introduced, the diaphragm 23d resists the urging force of the spring 23e and the rod 23
c is moved to the left, the exhaust bypass valve 22 is fully opened at once, and the high-pressure turbine 3 is disabled.

At about the same time, the ECU 10 also issues a control output signal from the output port 102 to the three-way valves 75 and 97, switching their passages, and increasing the supply pressure P ₇ to the first chamber 73a of the actuator 73.
Is introduced and the second chamber 73b is communicated with the atmosphere and the rod 7
Since 3c is raised and the charge air bypass valve 72 is fully opened, the high pressure stage compressor 8 is also bypassed, the high pressure stage turbocharger H is separated from the flow of exhaust gas and supply air, and only the low pressure stage turbocharger L is used. It becomes a one-stage supercharged state.

Even if only the low pressure turbocharger L is supercharged,
When the pressure P _{7 in the} air supply passage 7 becomes too high due to the high rotation of the engine 1, the ECU 10 switches the three-way valve 14 to supply the air to the pipe 15 that has introduced the atmospheric pressure (or negative pressure) to the air supply of the engine 1. The pressure P _{1 in the} passage 12 is introduced. As a result, the actuator 43 partially opens the waste gate valve 42 according to the pressure P ₁ to reduce the rotation speed of the low-pressure stage turbine 5, and the pressure P ₁
To maintain the second target value P _1b .

As described above, since the charge pressure P ₉ is applied to the second chamber 23b of the actuator 23 by the three-way valve 93 until the load of the engine 1 exceeds the set value R ₂ , the target boost pressure P ₁ is low. The value P _1a is suppressed and does not rise as between A and B in FIG. 2, so that the high pressure stage turbocharger H is mainly prevented from performing unnecessary supercharging work. Thereby maintained exhaust pressure P ₂ is low in the exhaust passage 2, the pumping loss is also reduced, the fuel consumption rate of the engine 1 is also improved.

[Effect of device]

According to the present invention, the high pressure turbocharger is partially bypassed at the time of a light load that does not require high supercharging to reduce the rotation speed thereof by the structure and operation of the above means, so that the supercharging pressure is relatively low. The exhaust resistance (pumping loss) is reduced and the fuel efficiency is improved to maintain the target value of.

On the other hand, on the other hand, the high-pressure turbocharger is rotated at a low speed without being placed in a bypass state at all, so if the target value of the boost pressure is switched to the second target value at the same time when the load increases, the turbocharger becomes overloaded in a relatively short time. Since the supply pressure can be increased, the acceleration does not decrease.

In this way, the average number of revolutions of the high-pressure turbocharger can be lowered, so that its durability is increased and noise is reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing a supercharging pressure characteristic. 1 ... Engine, 2,4 ... Exhaust passage, 3 ... High pressure stage turbine,
5 ... Low-pressure stage turbine, 7, 9, 12 ... Air supply passage, 8 ... High-pressure stage compressor, 10 ... Electronic control device, 11 ... Rotation speed sensor,
13 ... Load sensor, 21 ... Exhaust bypass passage, 22 ... Exhaust bypass valve, 23, 25 ... Actuator, 23b ... First pressure chamber,
25b ... second pressure chamber, 42 ... wastegate valve 76 ... pressure sensor, 14,93 ... electromagnetic three-way valves, H ... high-pressure stage turbocharger, L ... low-pressure stage turbocharger, P ₁ ... boost pressure,
P _1a ... 1st target value, P _1b ... 2nd target value, R ₂ ... Load setting value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Taichi Mori, Toyota City, Toyota City, Aichi Prefecture, Toyota Toyota Motor Co., Ltd. (72) Inventor, Kazuyoshi Ishizaka, Toyota City, Toyota City, Aichi Prefecture, Toyota Motor Corporation, Toyota (72) Inventor Shinobu Ishiyama 1 Toyota-cho, Toyota-shi, Aichi Prefecture Toyota Motor Corporation (56) Reference JP-A-60-50229 (JP, A) JP-A-63-16130 (JP, A) JP Sho 60-184930 (JP, A) Actual opening 62-108536 (JP, U) Actual opening 62-119435 (JP, U) Actual opening Flat 2-131033 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A two-stage turbocharged engine having a low-pressure turbocharger for pressurizing intake air, and a high-pressure turbocharger for further pressurizing the air pressurized in the low-pressure turbocharger and sending it to the engine. Two pressure chambers for introducing control pressure are provided in an actuator for operating an exhaust bypass valve that opens and closes an exhaust bypass passage provided for the high-pressure turbine, and a load of the engine is set to a set value in the first pressure chamber. In order to maintain the supercharging pressure at a relatively low first target value until reaching, the pressure downstream of the high-pressure compressor is introduced as the control pressure, and when the load exceeds the set value, The boost pressure is relatively high until the pressure reaches a predetermined target value.
In order to maintain the target value of 1., a switching means for introducing a low pressure such as atmospheric pressure as a control pressure is provided, and a pressure downstream of the high pressure stage compressor is introduced into the second pressure chamber. Supercharging pressure controller for 2-stage turbocharged engine.