JPH0299723A - Supercharging control device for two-stage turbo engine - Google Patents

Abstract

PURPOSE:To perform smoothly and securely the switching from the two-stage supercharging condition to the one-stage supercharging condition while maintaining the high supercharging efficiency by providing a valve for switching to various stages in response to the supercharging pressure, in an exhaust bypass passage for deturning an exhaust turbine of a high-pressure stage turbo charger. CONSTITUTION:An exhaust bypass valve 24 switchable to various stages in response to the respective outlet side supercharging pressure of a high-pressure stage compressor 6 and a low-pressure stage compressor 5 is provide din an exhaust bypass passage 14 for deturning a high-pressure stage turbine 4. The exhaust bypass valve 24 is controlled by an exhaust bypass valve driving device 34 so as to open in response to only the outlet side supercharging pressure of the high-pressure stage compressor 6 when the outlet side supercharging pressure of the low-pressure stage compressor 5 is less than the predetermined, and so as to fully open immediately when the outlet side supercharging pressure of the low-pressure stage compressor 5 attains to the predetermined value. Thereby, since the exhausted gas flows through the exhaust bypass passage 14 and deturns the high-pressure stage turbine 4, a high-pressure stage turbo charger becomes the non-supercharging condition and is switched to the one-stage supercharging condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a supercharging control device for a two-stage turbo engine that is equipped with two turbochargers and performs supercharging over two stages.

[Conventional technology]

For vehicle engines that are increasingly required to improve output and fuel efficiency, installing a turbocharger can improve combustion conditions and is extremely effective, so even higher supercharging is required from low speed ranges to high speed ranges. In order to obtain a wide range of power, two-stage turbo engines have been put into practical use, in which two turbochargers are connected in series for supercharging.

However, simply combining turbochargers may have an adverse effect on each other due to changes in operating conditions, so in low speed ranges, a small-capacity high-pressure turbocharger and a large-capacity low-pressure turbocharger must be operated together. In order to operate only the large-capacity, low-pressure stage turbocharger in the high-speed range, this inconvenience is improved by considering the characteristics of each turbocharger and using them appropriately (Japanese Patent Application Laid-open No. 129815/1983, (Refer to Japanese Patent Application No. 1982-82526).

By the way, switching from two-stage supercharging to one-stage supercharging is
This is generally done by installing an exhaust bypass valve that responds to the boost pressure on the compressor outlet side of the high-pressure turbocharger in the bypass passage that bypasses the exhaust turbine of the small-capacity high-pressure turbocharger, and opening this valve fully. It is. In addition, due to various requirements for mounting on vehicles, such as excellent responsiveness, low cost, and simplicity, the exhaust bypass valve is generally driven to open and close by a pressure-operated actuator with a built-in spring. Therefore, it has a linear valve opening characteristic that is centrally determined by the spring constant of this drive system.

[Problem to be solved by the invention]

However, in the conventional two-stage turbo engine mentioned above,
It has the above-mentioned linear valve opening characteristic so that when the boost pressure on the outlet side of the low-pressure compressor reaches the target boost pressure, it switches from two-stage supercharging to single-stage supercharging, that is, the exhaust bypass valve is fully open. When the drive actuator is set to a predetermined value, there is a problem that due to this linear characteristic, the ink set point (A') is lowered as shown by the broken line in FIG. 7, and the supercharging pressure is lowered overall.

On the other hand, if the ink set point is set higher than this, it is possible to increase the overall supercharging pressure in the low speed range before switching to supercharging, but when switching to supercharging in the middle and high speed ranges (point B) Since the bypass valve is not reliably fully opened, the high-pressure turbocharger continues to rotate beyond its effective operating range, resulting in a situation in which supercharging is then switched. This is undesirable from the viewpoint of the service life of the high-pressure stage turbocharger, and from the viewpoint of giving an unnecessary load to the low-pressure stage turbocharger due to an increase in back pressure caused by the extra rotation of the high-pressure stage turbocharger.

In view of the above points, in the present invention, the ink set point can be set to a high level, so that overall high supercharging efficiency can be maintained even in the low speed range, and the switching from the two-stage supercharging state to the single-stage supercharging state is smooth. It is an object of the present invention to provide a supercharging control device for a two-stage turbo engine that can perform supercharging reliably and do not impose unnecessary loads on each other, thereby improving output performance, fuel efficiency, etc.

[Means to solve the problem]

In order to solve the above problems, the present invention provides a low-pressure turbocharger that supercharges intake air, and a high-pressure turbocharger that further supercharges the air supercharged by the low-pressure turbocharger and sends it to the engine. In the two-stage turbo engine, an exhaust bypass passage that bypasses the exhaust turbine of the high-pressure turbocharger can be opened and closed in multiple stages in response to respective supercharging pressures on the compressor outlet side of the high-pressure stage and low-pressure stage turbochargers. An exhaust bypass valve is provided, and the exhaust bypass valve opens only in response to the boost pressure on the compressor outlet side of the high pressure turbocharger when the boost pressure on the compressor outlet side of the low pressure turbocharger is below a predetermined value. There is provided a supercharging control device for a two-stage turbo engine, characterized in that the valve is fully opened as soon as the supercharging pressure on the compressor outlet side of the low-pressure turbocharger reaches a predetermined pressure.

[For production]

When the supercharging pressure on the compressor outlet side of the low-pressure turbocharger reaches a predetermined pressure, an exhaust bypass valve provided in an exhaust bypass passage that bypasses the exhaust turbine of the high-pressure turbocharger immediately opens fully. As a result, the exhaust gas flows through this exhaust bypass passage and bypasses the high-pressure stage exhaust turbine, so the high-pressure stage turbocharger becomes non-supercharged. In other words, the transition from the two-stage supercharging state to the single-stage supercharging state is smooth and reliable. It will be held on.

〔Example〕 The present invention will be explained below based on illustrated embodiments.

FIG. 1 is an overall schematic configuration diagram of an embodiment of a supercharging control device for a two-stage turbo engine according to the present invention, in which an exhaust passage 2 of an engine 1 is connected in series with a large-capacity turbine 3 of a low-pressure stage and a high-pressure stage of a high-capacity turbine 3. Small capacity turbines 4 are provided, these turbines 3
．． A large capacity compressor 5 at a low pressure stage and a small capacity compressor 6 at a high pressure stage are interposed in the intake passage 7, respectively driven by the compressors 4 and 4. Reference numeral 8 is an interthaler for cooling the heated supercharged air. In addition, the turbine 3 of the low pressure stage and high pressure stage
．． Exhaust bypass passages 13 and 14 are provided to bypass the exhaust gases 4 and 4, respectively. A so-called waste gate valve 23 is driven by an actuator 33 in which a first pressure working chamber 33a is open to the atmosphere and a second pressure working chamber 33b is communicated with the outlet side of the low pressure stage compressor 5 in the exhaust bypass passage 13 on the high pressure stage side. will be placed. High pressure stage side exhaust bypass passage 1
4 is an exhaust bypass valve driving device 34 which is a main part of the present invention.
An exhaust bypass valve 24 is provided which is driven by.

The details of this drive device 34 will be described later.

On the other hand, an intake bypass passage 16 that bypasses the high-pressure compressor 6 is provided on the compressor side, and an intake bypass valve 26 is disposed in this bypass passage 16. The intake bypass valve 26 includes a truncated conical plug 26a and this plug 2.
Partition part 26 in which a hole 26b that engages with the slope of 6a is formed.
c, and this plug 26a is reciprocally movable in the bypass flow direction by an actuator 36. The actuator 36 has first and second pressure working chambers 36a, 36b.

An electromagnetic three-way valve 17 is interposed in the first passage 9 that communicates the first pressure working chamber 36a of the actuator 36 with the outlet side of the low-pressure compressor 5. When the three-way valve 17 is not energized, it can be set, for example, to assume the white boat position, in which case the first pressure-operating chamber 36a is either open to the atmosphere or connected to a negative pressure source (for example, an intake manifold or intake pipe). (intake negative pressure area or vacuum pump)
On the other hand, when it is energized, it assumes the black boat position and the first pressure working chamber 36a is communicated with the outlet side of the low pressure stage compressor 5.

Further, the second pressure operating chamber 36b of the actuator 36 is communicated with the outlet side of the high-pressure stage compressor 6 via a second passage 10, and an electromagnetic three-way valve 18 is interposed in this passage 10. When the three-way valve 18 is not energized, it can be set to take, for example, a white boat position, at which time the second pressure operating chamber 36b is open to the atmosphere, and on the other hand, when it is energized, it takes a black boat position. The two-pressure working chamber 36b is communicated with the outlet side of the high-pressure compressor 6.

Further, in order to detect the magnitude of the pressure between the supercharging pressure P5 on the outlet side of the low-pressure stage compressor 5 and the supercharging pressure P on the outlet side of the high-pressure stage compressor 6, for example, a pressure balanced differential pressure gauge 41 is provided, A signal S from the differential pressure gauge 41 indicates whether the supercharging pressures P and P6 match or which one is larger (or smaller)!
fi is output, and this signal St. is control computer 5
It is input to I. Here, in place of the differential pressure gauge 41, separate, for example, piezoelectric pressure gauges (not shown) for measuring the absolute values of supercharging pressure P and P are provided, and based on the analog signals from these pressure gauges, the A/D There is no problem in a format in which comparison and arithmetic processing are performed within the control computer 51 via a converter (not shown). Note that the aforementioned three-way valves 17 and 18 receive output control signals S and S8 from the control computer 51.
Each is controlled separately.

Exhaust bypass valve 2, which forms the main part of the present invention mentioned earlier
4 will be described in detail. FIG. 21 is a longitudinal sectional view of a first embodiment of this exhaust bypass valve driving device 34. The first pressure working chamber 61 is communicated with the outlet side of the high-pressure compressor 6 via the passage 11, and therefore, the flange 62 and the rod 63 connected to the flange 62 are compressed in response to the boost pressure P. It is displaced to the left in the figure while overcoming the biasing force of the spring 64.

At this time, a heat-resistant diaphragm 65 made of, for example, metal
Most of the air in the diaphragm chamber 66, which is airtightly isolated from the first pressure operating chamber 61 by the rod 63, is
and the hole in the body 67 through which it passes, and the body 6
It is opened to the atmosphere through an inner circumferential groove 68 formed in this hole of No. 7 and a passage 69 extending outside from this inner circumferential groove.

In addition to such a first drive structure, the present drive device 34 further has the following second drive structure. That is, a second pressure working chamber 71 is provided, and this second pressure working chamber 71 is communicated with the outlet side of the low pressure stage compressor 5 via the passage 12. Inside this passage 12 is an electromagnetic three-way valve 1.
For example, when the three-way valve 19 is de-energized, the second pressure working chamber 71 is opened to the atmosphere, and when it is energized, the second pressure working chamber 71 is supplied with supercharging pressure on the outlet side of the low-pressure compressor 5. P, can act.

Therefore, when a predetermined supercharging pressure P acts in the first pressure working chamber 61, the rod 63 is displaced, and the protrusion 63a provided on the rod 63 is moved, for example, to the position A shown in the broken line.
The three-way valve 19 switches and the supercharging pressure P is applied to the second pressure working chamber 71.
5, the flange 72, which together with a heat-resistant, e.g. metallic diaphragm 75, hermetically isolates the diaphragm chamber 76 from the second pressure working chamber 71 slides on the rod 63. And the protrusion 63 of the rod 63 located at the broken line position A
a and the protrusion 63a is further moved to the broken line position iB in the figure, that is, the rod 63 is moved. At this time, the air inside the diaphragm chamber 76 is
It is exposed to the atmosphere through a gap between the cap 77 and the hole in the cap 77 through which it passes. Note that a small portion of the positive pressure air in the second pressure operating chamber 71 leaks from the gap between the rod 63 and the hole in the body 67 through which it passes, but this leaks out from the diaphragm that acts on the rod 63 in the return direction. Since the air is exposed to the atmosphere through the inner circumferential groove 68 and the passage 69 before flowing into the chamber 66, no particular inconvenience occurs.

As described above, according to the drive structure of this embodiment, the high pressure stage compressor 6 outlet side supercharging pressure P,
By applying this pressure, the rod 63
can be moved linearly, so this rod 6
3, the opening degree of the exhaust bypass valve 24 is centrally controlled via a link mechanism (not shown). And three-way valve 19
The opening degree of the exhaust bypass valve 24 can be controlled dually by applying a positive pressure, for example, the supercharging pressure P5 on the outlet side of the low pressure stage compressor 5, to the second pressure working chamber 71 via the second pressure operating chamber 71. That is, until the supercharging pressure P on the outlet side of the low pressure stage compressor 5 reaches the predetermined pressure, the supercharging pressure P on the outlet side of the high pressure stage compressor 6
6, and when the supercharging pressure P reaches a predetermined pressure, the exhaust bypass valve 24 is immediately fully opened. becomes possible.

Next, a second embodiment of the device for driving the exhaust bypass valve 24 will be described. Referring to FIG. 3, the first pressure working chamber 81 and the second pressure working chamber 91 are connected to passages 11 and 1.
2 to the outlet side of the high-pressure stage compressor 6 and the outlet side of the low-pressure stage compressor 5, respectively, and a three-way valve 19 is interposed in the passage 12, as in the first embodiment (see Fig. 1). ).

The first pressure working chamber 8 is formed by heat-resistant bellows 85 and 95.
Compression springs 84 and 94 are installed in bellows chambers 86 and 96, which are airtightly isolated from the first and second pressure working chambers 91, respectively.
are respectively arranged to urge the bellows 85 and 95 to the right in the figure. The bellows 85 is integrally movably connected to the piston rod 83 together with the flange 82 etc. Similarly, the bellows 95 is integrally movably connected to the rod 93 together with the flange 92 etc.

This rod 93 is connected to the exhaust bypass valve 24 via a link mechanism (not shown).

Therefore, a predetermined supercharging pressure P on the outlet side of the high pressure stage compressor 6 acts in the first pressure working chamber 81, and the piston rod 83
When the piston rod 83 moves, the tip of the piston rod 83 moves to the second position.
The rod 93 also moves in the same way to come into contact with and press the flange 92 in the pressure working chamber 91. At this time, in order to compress both springs 84 and 94 (spring 84
, 94 spring constants are each +1 kg, then
If both are compressed, a considerable boost pressure P6 is required to open and close the exhaust bypass valve 24 (equivalent to compressing a spring with a spring constant of kI + 2). Also, at this time, the air in the bellows chamber 86 is removed from the piston rod 8.
3 and the hole in the base 87 through which it passes, the second pressure working chamber 91 is opened to the atmosphere.

Similarly, the air in the bellows chamber 96 is released to the atmosphere through the gap between the rod 93 and the hole in the support portion 97 through which it passes.

In this way, the supercharging pressure P on the outlet side of the high pressure stage compressor is
6 acts on the first pressure working chamber 81, and the piston rod 83
Furthermore, when the rod 93 has moved by a predetermined amount, when the three-way valve 19 is switched and supercharging pressure P is applied to the second pressure working chamber 91, the flange 92, bellows 95, and rod 93 will move further. At this time, only the spring 94 with a spring constant of 2 is substantially compressed. Also,
At this time, the flange 82, bellows 85, and piston rod 83 move forward following the movement of the rod 93, but the positive pressure air in the second pressure working chamber 91 flows through the piston rod 83 and the hole in the base 87 through which it passes. It flows into the bellows chamber 86 through the gap between the piston rod 83 and acts in the return direction of the piston rod 83, causing the piston rod 83 to retreat. However, this movement does not affect the operation of the rod 93 or the exhaust bypass valve 24, and there is no particular disadvantage.

As described above, according to the drive structure of this embodiment, by applying the supercharging pressure P on the outlet side of the high pressure stage compressor 6 in the first pressure working chamber 81, the piston rod 83 and the rod 93 can be moved linearly (the spring constant of the drive system at this time is (kl + kz)
), therefore, the opening degree of the exhaust bypass valve 24 is centrally controlled.

By applying positive pressure, for example, the supercharging pressure P on the outlet side of the low-pressure compressor 5, to the second pressure working chamber 91 via the three-way valve 19, the rod 93 can be moved further without being affected by the movement of the piston rod 83. It can be moved quickly (the spring constant of the drive system at this time is ). That is, for example, by setting the spring constant of the spring 94 to 2 in advance to be relatively smaller than that of the spring 84, the high-pressure compressor 6 outlet is closed until the outlet-side supercharging pressure P5 of the low-pressure compressor 5 reaches a predetermined value. The opening degree of the exhaust bypass 24 is controlled in response to the side boost pressure P6, and when the boost pressure P reaches a predetermined pressure, the exhaust bypass valve 24 is rapidly fully opened.
In this way, two-stage valve control similar to the drive structure of the first embodiment is possible.

Next, a third embodiment of a device for driving the exhaust bypass valve 24 will be described. Referring to FIG. 4, in this embodiment, unlike the double-acting structure of the first and second embodiments, a general single-acting actuator is used and this is subjected to so-called duty control. Similarly, the opening of the exhaust bypass valve 24 is controlled in multiple stages. That is, the first pressure operating chamber 44a of the actuator 44 is communicated with the outlet side of the high-pressure compressor 6 through the passage 21, and the three-way valve 29 is interposed in the passage 21.
Set the boat position to be outlined in white when de-energized, and the port position to be indicated in black when energized. Actuator 44
The second pressure working chamber 44b is opened to the atmosphere, and a compression spring 44e is disposed therein. Therefore, when the three-way valve 29 is not energized, the actuator 4 is activated by the biasing force of the spring 44e.
The exhaust bypass valve 24 is fully closed via the rod 4 and a linkage mechanism not shown, while when energized this spring 4
The biasing force of 4e and the first pressure operating chamber 4 of the actuator 44
The supercharging pressure P on the outlet side of the high pressure stage compressor 6 acting on 4a
, the exhaust bypass valve 24 according to the driving force based on the magnitude of
is opened. Controlling the valve opening by performing this excitation intermittently is generally called duty control, and the three-way valve 2
9 is supplied with a rectangular drive pulse t4 shown in FIG. These driving pulses t and i have a constant period. Hereinafter, t and t/lo will be referred to as the duty ratio of the drive pulse. When the drive pulse Ld is generated, the switching action of the three-way valve 29 causes the first pressure operating chamber 4 of the actuator 44 to
4a is connected to the outlet side of the high-pressure compressor 6, and is opened to the atmosphere when the generation of the drive pulse L4 stops.

Therefore, the longer the driving pulse L4 is generated, that is, the greater the duty ratio, the longer the first pressure working chamber 44a is connected to the outlet side of the high pressure compressor 6. The positive pressure (supercharging pressure P6) that acts inside the exhaust gas increases, and therefore the opening degree of the exhaust pipe bus valve 24 increases. On the other hand, when the duty ratio becomes smaller, the time during which the first pressure working chamber 44a is open to the atmosphere becomes longer, so the positive pressure inside the first pressure working chamber 44a becomes smaller, and therefore the opening degree of the exhaust bypass valve 24 becomes smaller. becomes smaller. In addition, since it is necessary to fully open the exhaust bypass valve rapidly, the spring 44e is set to be weak (having a small spring constant).

Therefore, according to the drive type of this embodiment, the first and second
Similar to the drive structure of the embodiment, the exhaust bypass valve 2 is activated in response to the outlet side supercharging pressure P6 of the high pressure compressor 6 until the low pressure stage compressor 5 outlet side supercharging pressure P reaches a predetermined value.
Multi-stage valve control is possible, such as controlling the opening degree of the exhaust bypass valve 24 and immediately fully opening the exhaust bypass valve 24 when the supercharging pressure P5 reaches a predetermined value. Furthermore, according to this embodiment, the actuator can also be downsized.

The operation of the supercharging control device for a two-stage turbo engine according to the present invention, which can use the three embodiments of the device for driving the exhaust bypass valve 24 which constitutes the essential part of the present invention described above, will be explained with reference to FIG. do.

First, in the low-speed range of the engine 1, the amount of exhaust gas is generally small, and therefore, in order to effectively utilize the energy of this small amount of exhaust gas, the high-pressure stage turbine 4, which has a small capacity, is rotated, and the high-pressure stage is rotated integrally with the high-pressure stage turbine 4. It is most effective to perform supercharging using the compressor 6. For this supercharging, the exhaust bypass valve 24
This is achieved by a series of movements in which the valve is in the closing direction in response to this pressure being low, and therefore the entire amount of exhaust gas is supplied to the high-pressure turbine 4. At this time, the large-capacity turbine 3 and compressor 5 in the low-pressure stage are operating, but sufficient supercharging has not yet been performed because the speed is in a low speed range and the amount of exhaust gas is small.

Next, from low speed to medium/high speed range, the amount of exhaust gas increases, and the large-capacity low-pressure turbine 3 and compressor 5 gradually begin to perform the original supercharging. Therefore, as mentioned above, the problem is when to deactivate the high-pressure stage turbocharger, that is, when to change from the two-stage supercharging state to the first-stage supercharging state. By using the driving device, the exhaust bypass valve 24 can be fully opened at once when the supercharging pressure P on the outlet side of the low-pressure compressor 5 reaches the target supercharging pressure. As a result, the exhaust gas discharged from the engine 1 bypasses the high-pressure turbine 4 and flows through the exhaust bypass passage 14, so that the high-pressure turbine 4 is substantially inactive. At this time, the intake bypass valve 26 in the intake bypass passage 16 is similarly fully opened. As a result, the high-pressure stage turbocharger is completely in a non-supercharging state, meaning that the switch from two-stage supercharging to single-stage supercharging has been completed perfectly. By switching in this manner, the intercept point can be set high without sacrificing the supercharging efficiency of the high-pressure compressor 6 in the low speed range. In addition, the exhaust bypass valve 24 can be fully opened when the low-pressure stage compressor 5 outlet side supercharging pressure P5 is at the predetermined supercharging pressure, and therefore the high-pressure stage turbocharger can be brought into the non-supercharging state quickly and reliably. Since this can be done all at once, it is possible to eliminate a series of inconveniences such as a decrease in supercharging efficiency due to an increase in back pressure caused by operation beyond the effective operating range of the high-pressure stage turbocharger, and a deterioration in fuel efficiency.

Also, from another perspective, the fact that the high-pressure turbocharger can be placed in a non-supercharging state at an appropriate timing during supercharging switching means that overspeeding of the high-pressure turbocharger is prevented, and therefore The service life of the high pressure stage turbocharger can be improved.

Note that the intake bypass valve 2 provided in the intake bypass passage 16
The exhaust bypass valve 6 is controlled to be fully opened substantially at the same time as the exhaust bypass valve 24, but before the exhaust bypass valve 24 is fully opened, it is necessary to keep it fully open so that there is no leakage. This is done as follows. That is, in the low speed range, the first pressure horn operating chamber 36a of the actuator 36 that opens and closes the intake bypass valve 26
is opened to the atmosphere (or communicated with a negative pressure source) via the three-way valve 17, and the second pressure working chamber 36b is communicated with the outlet side of the high-pressure stage compressor 6 via the three-way valve 18, so that the supercharging pressure P is maintained inside. , acts. Therefore, the closing pressure (pressure that prevents the bypass flow of supercharged air) of the intake bypass valve 26 can be maintained extremely high, and therefore leakage of supercharged air from the intake bypass valve 26 can be almost eliminated. At this time, from the viewpoint of increasing the shutoff pressure, it is preferable that the first pressure working chamber 36a be communicated with a negative pressure source via the three-way valve 17.

When the intake bypass valve 26 is fully opened in the medium/high speed range, the aforementioned three-way valves 17 and 18 are switched substantially simultaneously. The first pressure operating chamber 3 (ia
is communicated with the outlet side of the low-pressure stage compressor 5, and supercharging pressure P acts therein, and the second pressure working chamber 36b is opened to the atmosphere. Therefore, the pressure in the first pressure working chamber 36a of the actuator 36 is reduced by the spring 3 inside the second pressure working chamber 36b.
6e, the supercharging pressure P and spring 36
By setting the relationship between e and the force in advance, it is possible to switch the opening and closing of the intake bypass valve 26 extremely quickly and smoothly, and moreover, it is possible to switch the opening and closing of the intake bypass valve 26 at once while maintaining a high closing pressure until just before the intake bypass valve 26 opens. It is possible to control the opening and closing of the intake bypass valve 26, which can be opened and has excellent responsiveness that prevents leakage. Note that the second pressure working chamber 36b is the three-way valve 1.
8, the exhaust passage 2 downstream of the engine I and having a predetermined positive pressure may be communicated with the exhaust passage 2.

In addition, by adding the configuration briefly explained below to the configuration of the embodiment of the supercharging control device according to the present invention described above, it is possible to substantially improve the performance at startup when no supercharging is being performed or from a light load state to a high load state. Improvements in output performance and fuel efficiency can be achieved over all engine operating conditions.

That is, referring to FIG. 6, an intake bypass passage 15 bypassing the low-pressure stage and high-pressure stage compressors 5 and 6, and an intake bypass valve 25 interposed in the intake bypass passage 15.
and. The intake bypass valve 25 has a first valve connected to the outlet side of the high-pressure compressor 6 via a passage (not shown).
It has a pressure working chamber 25a and a second pressure working chamber 25b which is equipped with a compression spring 25e and is open to the atmosphere.
.

Opening/closing is controlled by the magnitude of the force generated by the spring 25e (approximately equal to ) and the biasing force of the spring 25e.

With the above configuration, when the engine operating state is, for example, light load, and therefore, when neither of the two turbochargers is substantially supercharging, the high pressure stage compressor 6
Since the supercharging pressure P6 is low, the intake bypass valve 25 remains open due to the biasing force of the spring 25e in the second pressure working chamber 25b. Therefore, in addition to the flow of supply air through the low-pressure stage and high-pressure stage compressors 5 and 6, a sufficient amount of air flows through the intake bypass passage 15, which has extremely low flow path resistance, and is supplied to the engine 1. The engine starts up extremely smoothly. In other words, conventionally, when the load is light, the amount of exhaust gas is absolutely small, so the compressors 5 and 6 provide little or no supercharging. Although air supply tends to be blocked, by providing the intake bypass passage 15, a sufficient amount of air supply is easily supplied to the engine 1.

When the engine operating condition gradually becomes active and the supercharging progresses and the supercharging pressure P6 at the outlet of the high-pressure stage compressor 6 exceeds a predetermined value, it acts on the first pressure operating chamber 25a of the intake bypass valve 25, causing the spring 25e to As a result of overcoming the force, the intake bypass valve 25 closes. Thereafter, when the supercharging pressure P6 exceeds the predetermined value,
If the supercharging control device is in the above-mentioned state, the intake bypass valve 25 remains closed, and the supercharging control device according to the present invention has substantially the same effect as the above-described embodiment.

As described above, when the load is light, so-called natural air supply can be performed through the intake bypass passage 15, and when the load is higher than a predetermined value, the intake bypass passage 15 is closed, similar to the above embodiment of the supercharging control device according to the present invention. Since the supercharging balance can be maintained in harmony, output performance and fuel efficiency can be extremely effectively improved in all engine operating conditions from light loads to high loads.

Note that 3 is used as the device 34 for driving the exhaust bypass valve 24.
Although the present invention has been described with reference to two illustrated embodiments, the idea of the present invention is not limited to the drive formats of these embodiments, and may widely adopt other drive formats such as a negative pressure operating type, a stepping motor, etc. It goes without saying that you can. Similarly, the exhaust bypass valve 24 is not limited to the butterfly valve shown, but may be of many other types, such as a poppet type or a spool type.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to maintain high supercharging efficiency in the low speed range, and also to smoothly and reliably bring the high pressure stage turbocharging to a non-supercharging state when switching supercharging. Therefore, it is possible to improve the output performance and fuel efficiency over the entire supercharged operation state of the engine from the low speed range to the medium/high speed range.

[Brief explanation of the drawing]

FIG. 1 is a general schematic diagram of an embodiment of a supercharging control device for a two-stage turbo engine according to the present invention, and FIG. 2 is a first embodiment of a device for driving an exhaust bypass valve, which is a main part of the present invention. FIG. 3 is a vertical cross-sectional view showing a second embodiment of a device for driving an exhaust bypass valve, which is a main part of the present invention, and FIG. 4 is a vertical cross-sectional view showing an exhaust bypass valve, which is a main part of the present invention. A schematic configuration diagram showing a third embodiment of the device that drives the valve, FIG. 5 is a diagram for explaining duty control, and FIG. 6 is a two-stage configuration with an intake bypass passage that bypasses two turbochargers. FIG. 7 is a schematic configuration diagram of the main parts of the supercharging control device for a turbo engine, and is a diagram showing the relationship between the supercharging pressures Ps and P- on the outlet side of the low-pressure stage and high-pressure stage compressors. 1...Engine, 2...Exhaust passage, 3...
・Low pressure stage turbine, 4...High pressure stage turbine, 5...
・Low pressure stage compressor, 6... High pressure stage compressor, 7... Intake passage, 13, 14... Exhaust bypass passage, 16... Intake bypass passage, 23... Waste gate valve, 24... Exhaust bypass valve, 26... Intake bypass valve, 34... Exhaust bypass valve drive device.

Claims (1)

[Claims] A two-stage turbocharger having a low-pressure turbocharger that supercharges intake air, and a high-pressure turbocharger that further supercharges the air supercharged by the low-pressure turbocharger and sends it to the engine, wherein the high-pressure turbocharger An exhaust bypass valve that can be opened and closed in multiple stages in response to the respective supercharging pressures on the compressor outlet side of the high-pressure stage and low-pressure stage turbochargers is provided in the exhaust bypass passage that bypasses the exhaust turbine, and the exhaust bypass valve is configured to When the boost pressure on the compressor outlet side of the stage turbocharger is below a predetermined value, the valve opens in response only to the boost pressure on the compressor outlet side of the high pressure stage turbocharger, and the valve opens on the compressor outlet side of the low pressure stage turbocharger. A supercharging control device for a two-stage turbo engine, characterized in that the supercharging control device fully opens the engine immediately when supercharging pressure reaches a predetermined pressure.