JP2522802Y2 - Supercharging pressure control device for two-stage turbocharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a supercharging pressure control device that emphasizes efficiency in a two-stage turbocharged engine in which two exhaust turbochargers are connected in series.

[Conventional technology]

For example, as described in JP-A-59-82526 and JP-A-61-57135, most of the conventional control devices for a two-stage turbocharged engine have a configuration as schematically shown in FIG. And has operating characteristics as shown in FIG.

That is, in FIG. 5, 1 is an engine, 2 is an exhaust passage, 3 is a high-pressure stage turbine, 4 is its exhaust passage, 5 is a low-pressure stage turbine, 6 is a low-pressure stage compressor, and 7 is a supply passage after one-stage compression. , 8 is a high-pressure stage compressor, 9 is an air supply passage, 91 is an air supply cooler, and 12 is an air supply passage downstream thereof. Reference numeral 21 denotes a bypass passage of the high-pressure stage turbine 3, reference numeral 22 denotes a bypass valve for opening and closing the passage, reference numeral 24 denotes a first chamber 24a for accommodating a compression sprung by an actuator of the valve 22, and a second chamber separated from the first chamber 24a by a diaphragm. 24b. 41 is a bypass passage of the low pressure stage turbine 5, 42 is a waste gate valve for opening and closing the passage, 43 is an actuator of the valve 42,
It has a first chamber 43a for accommodating the compression ridge and a second chamber 43b separated by a diaphragm. Also, 7
1 is a bypass passage of the high-pressure stage compressor 8, 72 is an air supply bypass valve for opening and closing the passage, 73 is an actuator of the valve 72, and is a first chamber 73a and a first chamber 73a which is partitioned by a diaphragm and accommodates a compression spring. And two chambers 73b. A high-pressure stage compressor 8 is provided in the second chamber 24b of the actuator 24.
The outlet pressure P ₉ is supplied, the second chamber 43b of the actuator 43
And the first chamber 73a of the actuator 73 the outlet pressure P ₇ of the low-pressure stage compressor 6 is supplied, and controls the valves 22,42,72.

Figure 6 is shows the operation characteristics at full load for the prior art, P _A is the target value of the supercharging pressure, P _2, P ₄ is the exhaust pressure in the exhaust passage 2 and 4, P _7, P ₉ is The supply pressures (supercharging pressures) in the supply passages 7 and 9 are respectively shown, the horizontal axis represents the rotation speed (rpm) of the engine 1, and the vertical axis represents the pressure. The points A, B, C, D, and E correspond to the same points in FIG. 4 described later. For example, A is a point having a rotation speed of 0, B is 2,
000 rpm, C represents 2,800 rpm, D represents 3,200 rpm, and E represents the maximum rotational speed at 4,400 rpm.

From the low rotation range of the engine 1 to the middle rotation range,
Since the exhaust gas flow rate is small, the high-pressure stage turbine 3 mainly having a small capacity recovers the energy of the exhaust gas and drives the high-pressure stage compressor 8 to compress the supply air. As a result, the boost pressure P ₉ becomes the target value
Rise rapidly until it reaches the P _A, initially open the exhaust bypass valve 22 by the operation of the actuator 24 to the pressure P ₉ is added where it reaches the target value, bypassing a portion of the exhaust gas flowing into the high pressure turbine The number of revolutions of the high pressure turbine 3 is reduced. As a result, the supercharging pressure P ₉ becomes the target value P _A
Is kept substantially constant.従Gai the rotational speed of the engine 1 increases, including low pressure turbine 5 also work, since driving the low-pressure stage compressor 6, the outlet pressure P ₇ increases gradually as shown in FIG. 6, eventually target it reaches the value P _A. During this time the exhaust bypass quantity of the bypass valve 22 of the high pressure turbine is increased, and further, increases the opening with increasing pressure P ₇ air supply bypass valve 72 is also supplied to the actuator 73, the rotational speed of the engine Drpm when it, the pressure P ₇ reaches the target value P _a, wherein the maximum opening degree of each bypass valve 22 and 72 of the high pressure turbine 3 the compressor 8, a substantially low pressure turbine 5 the A high-efficiency one-stage supercharging state by the compressor 6 is set. When the rotation speed of the engine 1 further increases, the outlet pressure of the low-pressure stage compressor 6 increases.
Since P ₇ further rises, at that time, the waste gate valve 42 is opened by the actuator 43 receiving P ₇ ,
Controlling the rotational speed of the low pressure turbine 5 as supercharging pressure P ₇ is maintained at the target value P _A.

[Problems to be solved by the invention]

In the prior art, the rotational speed D of the engine 1 to the exit pressure P ₇ of the low-pressure stage compressor 6 reaches the target value, the outlet pressure P ₉ to the target value P _A high pressure compressor of a small capacity and high speed keeping. The high-pressure stage turbine 3 also has a small capacity such that a supercharging effect occurs from the time of low rotation of the engine 1, and when the point D is approached, the high-speed stage turbine 3 and the compressor 8 exceed the efficient rotational speed range. for that, the exhaust pressure P ₂ in the exhaust passage 2 pumping loss increases very higher as shown in Figure 6. Therefore, also in the engine 1, the gas exchange in the combustion chamber is not completely performed due to the increase in the exhaust resistance, the volume efficiency is reduced, and the overall efficiency of the entire engine is reduced even if the supercharging pressure is maintained. And the fuel efficiency deteriorates.

If the capacity of the high-pressure stage turbine 3 or the compressor 8 is increased, such a decrease in efficiency can be mitigated. However, since the boost pressure cannot be increased when the engine 1 is rotating at a low speed, the low-speed torque Engine. Accordingly, in general, the scroll area of the high-pressure stage turbine is reduced to improve the low-speed torque, and the scroll area of the low-pressure stage turbine is increased to improve the high-speed performance. Since there is a tendency to increase the size ratio of the low-pressure stage turbine 5, in the middle speed range from the point B to the vicinity of the point D in FIG. 6 before the intercept point where the two-stage supercharging is switched to the one-stage supercharging, Deterioration of the rate is inevitable, and the torque may decrease with efficiency.

The present invention has been made to solve this problem in the prior art.

[Means for solving the problem]

According to the present invention, when shifting from the two-stage supercharging state to the one-stage supercharging state, the exhaust gas bypass valve of the bypass passage of the high-pressure turbine is opened so that the supercharging pressure simply matches the target value as in the related art. Just by experiment, the fact that the back pressure of the engine did not actually fall sufficiently and the fuel efficiency and driving performance could not be improved was confirmed by experiments,
The supercharging pressure control device of the two-stage turbocharged engine of the present invention is:
A low-pressure stage turbocharger for pressurizing air supply, a high-pressure stage turbocharger for further pressurizing the supply air pressurized in the low-pressure stage turbocharger and sending it to an engine, and an exhaust bypass for bypassing an exhaust turbine of the high-pressure stage turbocharger A passage, an exhaust bypass valve provided in the bypass passage, and an appropriate bypass set in accordance with the detected supercharging pressure and the engine speed at the transition from the two-stage supercharging state to the one-stage supercharging state. An exhaust bypass valve driving device that operates to reduce the supercharging pressure by an appropriate amount from the target supercharging pressure by opening the exhaust bypass valve in accordance with a difference from the supercharging pressure. I have.

[Operation] Since the two-stage turbocharged engine according to the present invention has the above-described configuration, when the engine is rotating at low speed, two-stage supercharging by the high-pressure stage and the low-pressure stage turbocharger is performed.
During high-speed rotation, one-stage supercharging is performed only by the low-pressure stage turbocharger. Switching between two-stage supercharging and one-stage supercharging is performed by increasing the opening degree of the exhaust bypass valve by an exhaust bypass valve driving device that drives an exhaust bypass valve provided in an exhaust bypass passage of the high-pressure turbine. Then, the supercharging pressure is reduced below the target value, thereby flattening the exhaust pressure.

〔Example〕

In FIG. 1 showing one embodiment of the present invention, 1 is an engine to be supercharged, 2 is an exhaust passage thereof, 3 is a small-capacity exhaust turbine of a high pressure stage, 4 is an exhaust passage thereof, 5 is a large capacity of a low pressure stage. Exhaust turbine, 6 is a low-pressure stage large capacity compressor,
The low-pressure stage turbocharger L is connected to the exhaust turbine 5 by a rotating shaft. 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 constitutes a high-pressure stage turbocharger H connected to the exhaust turbine 3 by a rotating shaft. Reference numeral 9 denotes an air supply passage for the air pressurized by the high-pressure stage compressor, and reference numeral 10 denotes an electronic control unit (ECU) for controlling the supercharging pressure of a two-stage turbocharged engine having a configuration more than essential. The details will be described later.

An exhaust bypass passage 21 for the high-pressure turbine 3 is provided in the exhaust passage 2 through which the exhaust gas of the engine 1 flows, and an exhaust bypass valve 22 for controlling the opening and closing of the exhaust bypass passage 21 is provided. As shown in an enlarged manner in FIG. 2, a first actuator 23 provided on the front stage side for operating the valve is provided.
Has a rod 23c penetrating the front wall and a diaphragm (or bellows) 23d attached to the right end of the rod,
The diaphragm divides the inside of the actuator 23 into a first chamber 23a and a second chamber 23b. A relatively weak compression ridge 23e is inserted into the first chamber 23a, and the bypass valve 22 is attached in the valve closing direction. I'm going. A second actuator 25 is serially attached to the rear side of the first actuator 23, and the left end of a rod 25c penetrating the front wall thereof is in contact with the right end of the rod 23c of the first actuator 23. I have. Rod 25c
A diaphragm (or bellows) 25d for partitioning the inside of the actuator 25 into a first chamber 25a and a second chamber 25b is attached to the right end, and the first chamber 25a has a compression stronger than the compression ridge 23e of the first actuator. Spawn 25e is inserted. In FIG. 2, 23d ', 23d ", 25d' and 25d" are:
Each of them is a spacer that regulates and protects the amount of deformation of the diaphragm, 23g and 25g are guides for the rod, and 23f is a connecting pipe to the three-way valve 93.

An exhaust bypass passage 41 for the low-pressure stage turbine 5 is provided in the exhaust passage 4 in a branched manner, and a waste gate valve 42 for controlling opening and closing of the exhaust bypass passage 41 is disposed. An actuator 43 provided to operate 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. And a second chamber 43b, in which a compression spring 43e is inserted. 51
61 is an exhaust pipe for discharging exhaust gas from the low-pressure stage turbine 5;
Denotes an air supply pipe for supplying fresh air to the low-pressure stage compressor 6 via an air cleaner or the like (not shown).

An air supply passage 7 for discharging the air pressurized by the low-pressure stage compressor 6 is branched and provided with an air-supply bypass passage 71 for the high-pressure stage compressor 8, and an air supply bypass valve 72 for opening and closing the branch is provided. . An actuator 73 provided for operating the valve has a rod 73c penetrating the lower end wall thereof, and a diaphragm (or bellows) 73d attached to the upper end of the rod. A compression chamber 73e is inserted into the second chamber 73b.

Tube 96 is connected to the supply passage 9, with which supplies the pressure P ₉ into the second chamber 25b of the aforementioned actuators 25,
A pipe 93 ′ is connected to the air supply passage 9, and supplies the pressure P ₉ to the aforementioned electromagnetic three-way valve 93. The electromagnetic three-way valve 93 is operated by the ECU 10 as a switching valve, and selectively switches between the high pressure P ₉ of the air supply passage ₉ and the low pressure atmospheric pressure.
The second chamber receives the duty control by another ECU 10, which can be supplied to 23b, the second chamber of any pressure above the actuator 23 between the atmospheric pressure in this pressure P ₉ and low pressure
23b.

Further, the pressure P ₇ of the supply passage 7 is taken out by the tube 74 is supplied to the electromagnetic three-way valve 75, the actuator any of the three-way valve is the pressure P ₇ or atmospheric (or negative pressure due to the vacuum pump) with and supplies to the first chamber 73a of 73, the pressure P ₉ of the supply passage 9 is taken out by the pipe 96 'is supplied to the electromagnetic three-way valve 97, the three-way valve is the pressure P ₉ or large One of the air pressures is supplied to the second chamber 73b of the actuator 73.

In this embodiment, the second chamber 43b of the actuator 43 of the waste gate valve 42 is connected to the supply passage 7 by a pipe 98.
It is adapted to receive the pressure P ₇ of.

The control output signal of the ECU 10 is transmitted from the output port 102 via the drive circuit D to the electromagnetic three-way valves 93, 97, 75 and the like. Needless to say, these electromagnetic three-way valves, which are switching means of the control system, can be replaced by pneumatic or other three-way valves that operate in a similar manner.

Reference numeral 11 denotes a rotational speed sensor of the engine 1, 13 denotes a load sensor such as a throttle opening sensor, and 14 detects a pressure P ₉ ′ of an air supply passage 12 such as an air supply manifold downstream of the air supply cooler 91. Pressure sensors, which input detection values to an input port 101 of the ECU 10 via an A / D converter if necessary.

Next, the operation of the embodiment shown in FIG. 1 and FIG.
The control program of U10 will be described with reference to the flowchart of FIG.

The control program in the ECU 10 is repeatedly executed every fixed short time or every time such as one revolution of the crankshaft. In FIG. 3, when the program starts, first, in step 201, the rotational speed sensor 11
And the detected value of the throttle opening sensor 13 is read, the rotation speed of the detection value N _e of the engine at step 202 is compared with the rotational speed of the set value N _eB and N _eC. Rotational speed N _eB is equivalent to point B in FIG. 6 described prior art for a engine speed that the exhaust pressure P ₂ in the exhaust passage 2 starts to surge, also N _eC peak is P ₂ Is the number of rotations of the point C which reaches.

In step 202, when it is determined to be between N _eB and N _eC of N _e is a problem, the process proceeds to step 203, turn the throttle opening detection value T _i is fully opened or set value T _iF close to Is compared to If the throttle valve is not yet fully opened, the check is repeated. If it is determined that the throttle valve is fully open, the routine proceeds to step 204, where the supply pressure (supercharging pressure) P in the supply manifold 12 of the engine 1 detected by the pressure sensor 14 is detected. ₉ ′ is read, and then in step 205, the appropriate supercharging pressure P ₉ ″ is read from the map stored in the ROM.
, And the difference between P ₉ ′ and P ₉ ″ is calculated in step 206, and the absolute value is compared with the set value α of the allowable range.
If the difference is smaller than α, there is no problem, but if it is determined that the difference is larger than α, the electromagnetic three-way valve 9 is determined in step 207.
The duty ratio for driving 3 is calculated, and a control pulse is sent from the output port 102 to the three-way valve 93 via the drive circuit D in step 208.

As a result, in the second chamber 23b of the actuator 23, the pressure P9 of the air supply passage ₉ causes the air to flow at a predetermined rate (duty ratio).
And the rod 23c is pushed to the left by a controlled amount in FIGS. 1 and 2 against the compression ridge 23e, and the exhaust gas is bypassed.
22 is further partially opened from the original opening. Original opening is determined by the boost pressure P ₉ acting on the second chamber 25b of the actuator 25. Thereby, the high-pressure stage turbine 3 is decelerated, and the outlet pressure P ₉ of the compressor 8 or the pressure P ₉ ′ of the air supply passage 12 is obtained.
Decreases by a predetermined amount and exhibits a dip as shown between B and C in FIG. 4. The value of P ₉ ′ is monitored by the pressure sensor 14. This feedback control returns to step 201 and is repeated to approach a predetermined pressure value as shown in FIG.

The value of the exhaust pressure P ₂ in the exhaust passage 2 from the high-pressure stage turbocharger H is partially bypassed also reduced, peaks as between B-C of FIG. 6 is a fourth diagram disappeared B-
It becomes flat like between C. This allows the engine 1
Improved fuel efficiency and increased efficiency,
The reduction in torque is not significant.

When it is determined in step 202 of the flowchart of FIG. 3 that the engine speed _Ne is not between B and C in question, the process proceeds to step 211, and if the engine speed _Ne is larger than the point C, In step 212, the ECU 10 controls the electromagnetic three-way valve 93 to control the second chamber 23 of the actuator 23.
b to thereby conduct only boost pressure P _9, blocking the entry of air.
As a result, the exhaust bypass valve 22 takes the full open position at a time at the point C in FIG. 4, and disables the high-pressure stage exhaust turbine 3. At this time, the three-way valve 97
The switching with the second chamber 73b of the actuator 73 to open to the atmosphere, since introducing a boost pressure P ₇ of increased to the first chamber 73a of the actuator 73 by switching the three-way valve 75, also fully opened air supply bypass valve 72 Thus, the high-pressure stage turbocharger H is completely bypassed, and shifts to a highly efficient single-stage supercharging state using only the low-pressure stage turbocharger L. Supply pressure at this time
Changes in P ₉ or supercharge pressure P ₉ 'rises along the line of the boost pressure P ₇ as between FIG. 4 C-D, after reaching the target value P _A is held constant.

If the engine speed N _e in step 211 of FIG. 3 is determined to be smaller than the rotational speed N _eC point C in FIG. 6 and FIG. 4, in conjunction with the condition in step 202, N _e is B Since it is smaller than the rotation speed of the point (N _e <N _eB ), the _routine proceeds to step 213, where the ECU 10 sets the three-way valve 9
3 to release the second chamber 23b of the actuator 23 to the atmosphere. Accordingly, the spring 23c pushes the rod c to the right, closes the exhaust bypass valve 22 and supplies the entire amount of exhaust gas in the exhaust passage 2 to the high-pressure stage turbine. generating a supercharging pressure) P _9.

In the embodiment described above, the supply pressure P ₉ as a high control fluid pressure, the atmospheric pressure as a low control fluid pressure, or an intermediate pressure by mixing them at an appropriate ratio are provided in the second chamber 23b of the actuator 23. Although the case where the pressure is supplied has been described, in addition to the control using only the positive pressure, if any negative pressure source can be used, for example, the actuator 23 is supplied.
In the first chamber 23a, a negative pressure (low pressure), an atmospheric pressure (high pressure), or an intermediate weak negative pressure obtained by duty control of the three-way valve is actuated by an electromagnetic three-way valve, The same operation as described above can be performed.

In any event, embodiments of the present invention, the regulatory regions exhaust pressure P ₂ becomes abnormally high, i.e. in the range of the rotation speed B-C of the engine 1, the pressure of the control fluid to the actuator of the exhaust bypass valve 22 by the exhaust bypass valve 22 partially open (when partially open by the actuator 25 hearing gives additional opening), and the boost pressure P ₉ vacuo than the target value P _a, 4 It is characterized in that the control is performed between B and C in the figure, and the resulting boost pressure P ₉ ′ is detected by the pressure sensor 14 (or the exhaust pressure in the exhaust passage).
P ₄ may be detected by another pressure sensor), and controls them to make the supercharging pressure and exhaust pressure is fed back to the ECU 10, the peak exhaust pressure P ₂ is eliminated, the engine 1 The exhaust resistance is reduced, the efficiency is improved, and the fuel efficiency is also improved.

In short, the height and the pumping loss magnitude of the exhaust pressure P _2, the relationship between the fuel consumption is thus a unique and pumping loss to higher the exhaust gas exhaust pressure P ₂ is less likely to be discharged is increased fuel economy As shown in FIG. 4, there is a demand that the exhaust pressure P ₂ does not become higher than a predetermined value, and in order to respond to the demand, the present invention requires that the detected boost pressure and The bypass valve 22 is opened according to a difference from an appropriate supercharging pressure set according to the engine speed. More specifically, as shown in FIG. 6, the phenomenon that the exhaust pressure P ₂ increases as the engine speed increases is recognized. Therefore, the appropriate supercharging pressure increases as the engine speed increases. By setting it low, it is possible to effectively prevent deterioration of fuel efficiency due to pumping loss.

[Effect of the invention]

According to the present invention, it is possible to suppress an increase in exhaust pressure that tends to occur in a rotation region before switching from two-stage supercharging to one-stage supercharging. In addition to increasing the torque so that the supercharging effect appears in the low engine speed range of the engine, a single stage supercharging was performed in the high engine speed range by using a low pressure stage turbine having a larger scroll area. It is possible to improve the performance in both high and low ranges, for example, by increasing the supercharging rate at the time and obtaining high torque at high speed rotation.

In the medium speed range, the boost pressure will be slightly reduced to solve the problem.However, it is possible to suppress the rise in the exhaust pressure and increase the overall efficiency of each compressor in the low pressure stage and the high pressure stage. In addition, the fuel efficiency and drivability are improved, and the torque does not show a large drop, but rather increases in some cases.

Further, as a result of reducing the supercharging pressure to some extent in the middle speed range, the maximum in-cylinder pressure of the engine is reduced, which is advantageous in terms of strength, vibration, and the like.

[Brief description of the drawings]

1 is an overall configuration diagram of one embodiment of the present invention, FIG. 2 is an enlarged sectional view of a main part thereof, FIG. 3 is a flowchart showing a control program, and FIG. 4 is a diagram showing operating characteristics of the present invention. FIG. 5 is an overall configuration diagram showing a conventional example, and FIG. 6 is a diagram showing operating characteristics of the conventional example. DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Exhaust passage, 3 ... High pressure stage exhaust turbine, 5 ... Low pressure stage exhaust turbine, 6 ... Low pressure stage compressor, 7 ... Air supply passage, 8 ... High pressure stage compressor, 9 ... Air supply passage, 10 ... Electronics Type control unit (ECU), 11: rotation speed sensor, 12: air supply passage (air supply manifold), 13: load sensor (throttle opening sensor), 14: pressure sensor, 21: exhaust bypass passage, 22: exhaust bypass Valves, 23, 24, 25: Actuator, 42: Wastegate valve, 43: Actuator, 72: Exhaust bypass valve, 73: Actuator, 75: Electromagnetic three-way valve, 91: Supply air cooler, 93, 97: Electromagnetic Three-way valve.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuyoshi Ishizaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-62-113829 (JP, A) JP-A-60-40728 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] 1. A low-pressure stage turbocharger for pressurizing an air supply, a high-pressure stage turbocharger for further pressurizing the air supplied in the low-pressure stage turbocharger and sending it to an engine, and an exhaust turbine of the high-pressure stage turbocharger An exhaust bypass passage for bypassing the engine, an exhaust bypass valve provided in the bypass passage, and a switch from the two-stage supercharging state to the one-stage supercharging state. An exhaust bypass valve driving device that operates to reduce the supercharging pressure by an appropriate amount from the target supercharging pressure by opening the exhaust bypass valve in accordance with a difference from an appropriate supercharging pressure set in advance. And a supercharging pressure control device for a two-stage turbocharged engine.