JPH03202636A - Engine with turbo-supercharger - Google Patents

Abstract

PURPOSE:To enhance the rate of fuel consumption by introducing such a control that a waste gate valve opens when the engine operating condition is at least with high revolving speed and with low/medium load, and relieving rise of the supercharge pressure caused by increase in the engine load. CONSTITUTION:An engine concerned is equipped with a turbo-supercharger, in which pressurization is made for the suction air by a compressor 4B directly coupled with a turbine 4A driven by the exhaust gas. The exhaust passage 11 of this engine is provided with a waste gate passage 12 as a bypass to the turbine 4A, and a waste gate valve 13 opened and closed by an actuator 14 is installed at the upstream end of this waste gate passage 12. The actuator 14 is of diaphragm type, and leads the supercharge pressure to No.1 working chamber 14e and also introduces the suction neg. pressure to No.2 working chamber 14f via a communication path 16 on which a three-way solenoid valve 17 to be duty controlled is installed. Thereby such control shall take place that the waste gate valve 13 opens when the engine operating condition is at least with high revolving speed and with low/medium load.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a turbocharged engine, and in particular, to a method for mitigating the increase in supercharging pressure at least at low and medium loads in the high rotation range. This invention relates to a waste gate valve that opens and controls its opening degree.

[Prior art]

Conventionally, as described in, for example, Japanese Utility Model Application No. 60-178329, supercharging has been developed in which a turbocharger turbine and a compressor are interposed in the exhaust system and intake system of an automobile engine, respectively. Mechanical engines have been put into practical use.

The above-mentioned turbo supercharger is provided with a waste gate valve that bypasses a part of the exhaust gas to the turbine, and an actuator that adjusts the opening degree of this waste gate valve. The actuator is configured to be biased to close by a compression coil spring and to open by supercharging intake pressure (this is referred to as supercharging pressure), and when the supercharging pressure reaches a predetermined pressure, exhaust gas is released from the waste gate valve. A part of the pressure is relieved to prevent the boost pressure from rising above a predetermined pressure.

On the other hand, in a supercharged engine, in order to prevent the turbine from melting due to the heat of the exhaust gas in the high rotation range, the amount of fuel supplied is increased so that the mixture becomes overrich, and the latent heat of vaporization of the fuel is used. It is designed to reduce exhaust gas temperature.

[Problems to be Solved by the Invention] Fig. 10 shows the relationship between throttle opening, supercharging pressure, and throttle downstream intake pressure in a high rotation range in a conventional turbocharged engine, and Fig. 11 shows the relationship between the throttle opening degree, supercharging pressure, and throttle downstream intake pressure in a conventional turbocharged engine. This shows the characteristics of boost pressure over the entire operating range of a conventional engine.Since the exhaust gas flow rate is large in the high rotation range, the boost pressure increases almost linearly as the throttle opening increases. When the boost pressure increases and reaches the set maximum boost pressure, the actuator opens the waste gate valve and a portion of the exhaust gas is leaked into the bypass passage, so that the boost pressure is maintained at the maximum boost pressure from then on. On the other hand, as shown in the figure, the throttle downstream intake pressure is much lower than the supercharging pressure, and increases substantially linearly as the throttle opening increases.

Considering that the necessary and sufficient intake air can be supplied if the boost pressure is higher than the throttle downstream intake pressure, there is a large differential pressure between the boost pressure and the throttle downstream intake pressure in low and medium load conditions. ΔP is completely extra pressure, and the load on the turbocharger increases by this differential pressure ΔP.
In response to the high load on the compressor, the exhaust gas pressure on the upstream side of the turbine increases, resulting in a large exhaust loss.As the exhaust gas pressure is high and the flow rate of exhaust gas passing through the turbine also increases, the heat load on the turbine increases. Since the air-fuel mixture is controlled to be overrich in order to suppress the rise in exhaust gas salt, there are problems such as worsening fuel efficiency. As described above, in conventional turbocharged engines, no measures have been taken to reduce fuel consumption in the high rotation range.

The above description has been made for a typical case in a high rotation range, but the same problem as above occurs in a medium rotation range as well, although the degree is different.

SUMMARY OF THE INVENTION An object of the present invention is to provide a turbocharged engine that can improve fuel efficiency by reducing the increase in supercharging pressure at least in low load and medium load conditions in a high rotation range.

[Means to solve the problem]

A turbocharged engine according to a first aspect of the present invention is an engine equipped with a turbocharger and a wastegate valve provided in a passage bypassing a turbine of the turbocharger. a valve opening adjustment means for adjusting the opening; and a wastegate valve that opens the wastegate valve via the valve opening adjustment means to adjust the opening when the engine is in a low load and medium load state at least in a high rotation range. The valve opening degree control means is provided to control the increase in supercharging pressure due to an increase in engine load.

A turbocharged engine according to a second aspect of the present invention is an engine equipped with a turbocharger and a wastegate valve provided in a passage bypassing a turbine of the turbocharger. A valve opening adjusting means for adjusting the opening, an operating state detecting means for detecting the engine speed and load, and receiving the output of the operating state detecting means, detects the operating state of the engine as a parameter in a high rotation range. Valve opening control means for controlling the opening of the wastegate valve via the valve opening adjustment means so that the supercharging pressure increases in accordance with an increase in engine load according to a predetermined characteristic of the supercharging pressure set in advance; It has been established.

[Effect]

In the turbocharged engine according to the first claim,
The valve opening control means opens the wastegate valve via the valve opening adjustment means to control the opening of the wastegate valve, at least in low load and medium load states in a high rotation range, thereby alleviating an increase in supercharging pressure.

During low and medium load conditions in the high rotation range, the wastegate valve is opened to alleviate the increase in supercharging pressure associated with the increase in load, reducing the load on the turbocharger and reducing engine exhaust gas. The pressure decreases, reducing exhaust loss and improving fuel efficiency. Moreover, as the gas pressure of the exhaust gas passing through the turbine decreases and the flow rate also decreases, the thermal load on the turbine is significantly reduced, making it possible to improve fuel efficiency by omitting mixture overrich control for exhaust gas cooling. . In addition, by reducing the load and heat load on the turbocharger, it is possible to downsize the turbocharger.

In the turbocharged engine according to the second claim,
The valve opening control means receives the output of the operating state detection means, and adjusts the boost pressure in response to an increase in engine load in a high rotation range according to a predetermined characteristic of the boost pressure set in advance using the engine operating state as a parameter. The opening degree of the wastegate valve is controlled via the valve opening degree adjusting means so that the opening degree increases.

By setting in advance the characteristics of the boost pressure that prevent the boost pressure from becoming unnecessarily high relative to the throttle downstream intake pressure, it is possible to prevent the boost pressure from becoming unnecessarily high in relation to the throttle downstream intake pressure. The load on the turbo supercharger is reduced, exhaust loss is reduced and fuel efficiency is improved as in the first aspect, and fuel efficiency can be improved by omitting air-fuel mixture overrich control for exhaust gas cooling.

Since the supercharging pressure is controlled in a predetermined manner in association with the detected operating state, the supercharging pressure can be controlled more precisely, so that the fuel efficiency is further improved than in the first aspect, and the turbo It is possible to downsize the supercharger.

〔Effect of the invention〕

According to the turbocharged engine according to the first claim, as explained in the above [Operation] section, by providing the valve opening adjustment means and the valve opening control means, the It is possible to reduce the load on the turbocharger during load and medium load states, lower the exhaust gas pressure on the upstream side of the turbine, and reduce the thermal load on the turbine.

Therefore, it is possible to improve fuel efficiency by reducing engine exhaust loss, and at the same time, it is possible to omit mixture overrich control for exhaust gas cooling, improving fuel efficiency, and making it possible to downsize the turbo supercharger. .

According to the turbocharged engine according to the second aspect of the invention, as explained in the above [Operation] section, by providing the valve opening adjustment means and the valve opening control means, the turbocharger in the high rotation range is It is possible to reduce the load on the supercharger and the heat load on the turbine.

Therefore, fuel efficiency in the high rotation range can be further improved, and the turbocharger can be further downsized.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is an example in which the present invention is applied to a four-cylinder turbocharged engine for an automobile.

As shown in FIG. 1, the turbocharged engine has four cylinders, and the intake passage 1 of the engine E includes an air cleaner 2, an air flow meter 3, a compressor 4B of the turbocharger 4, and An intercooler 5 and a throttle valve 6 are provided, each branch intake pipe 7a of the intake manifold 7 is connected to a corresponding intake port 8, and each branch intake pipe 7a is provided with an injector for injecting fuel toward the intake boat 8. 9 is provided. Exhaust manifold 10
A turbine 4A of the turbocharger 4 is interposed in an exhaust passage 11 extending from the exhaust passage 11, and the turbine 4A and the compressor 4B are interlocked and connected by a common support shaft. 12 is provided, a waste gate valve 13 is provided for opening and closing the upstream end of the waste gate passage 12, and an actuator 1 is provided for driving the waste gate valve 3 to adjust its opening degree.
4 is provided.

The inside of the casing of the actuator 14 includes a first diaphragm 14a, a partition plate 14b, a second diaphragm 14c, a spring chamber 14d, a first working chamber 14e, and a second working chamber 14f.
and an atmospheric chamber 14g, a compression coil spring 14h for biasing valve closing is attached to the spring chamber 14d, and the first working chamber 14
Supercharging pressure is introduced into e from the intake passage 1 on the downstream side of the compressor 14B via the first communication passage 15, and the second working chamber 1
4f has a second intake passage from the intake passage 1 on the downstream side of the throttle valve 6.
Throttle downstream intake pressure (hereinafter referred to as intake pressure) is introduced through the communication passage 16 . A duty-controlled three-way solenoid valve 7 is interposed in the second communication passage 16.

Control unit 2 for controlling the engine E above
Signals from the air flow meter 3, throttle opening sensor 6a, crank angle sensor 18 and reference crank angle sensor 19 provided on the distributor, and other sensors and switches are input to the control unit 20. Drive signals are output from 20 to four injectors 9, an igniter (path shown), and a three-way solenoid valve 17.

The control unit 20 is mainly composed of a microcomputer, and further includes a plurality of A/D converters for AD converting detection signals from the air flow meter 3 and the throttle opening sensor 6a, and a plurality of A/D converters for the injector 9 and igniter. It is equipped with a drive circuit.

The ROM of the microcomputer 20 stores a control program for supercharging pressure control and associated maps, which will be described later.
A control program for fuel injection control, a control program for ignition control, and various other control programs are input and stored in advance. Note that the fuel injection control and ignition control are the same as those already known, so their explanation will be omitted, but in the fuel injection control, in the operating range where the boost pressure is high, mixture overrich control is executed to cool the exhaust gas. However, due to the boost pressure control described later, exhaust gas salts are alleviated at high speeds in the medium speed range and in low to medium load states in the high speed range, so the air-fuel mixture is reduced only in high load states in the above speed range. Overrich control is executed.

Next, supercharging pressure control unique to the present application will be explained.

First, to explain the outline of this boost pressure control, Fig. 2 shows the case where the engine speed is in a high speed range, and shows the magnitude of the set maximum boost pressure (Pl, P2, P3). The supercharging pressure increases as the throttle opening increases, and when it reaches the set maximum supercharging pressure, it is maintained at that pressure. In the conventional technology, the 10th problem is explained in the [Problem] section.
As shown in Figure 11, for example, the maximum boost pressure is set as shown by curve A, so the boost pressure is significantly higher than the intake pressure during low and medium load conditions. This increases the load and heat load on the turbocharger.

The boost pressure control of the present application gradually increases the set maximum boost pressure in accordance with the increase in throttle opening.
The opening degree of the waste gate valve 13 is controlled via the actuator 14 so as to achieve a target boost pressure of a necessary and sufficient magnitude.6 According to this boost pressure control, the operation of the engine E is controlled. When the state is at least on the high speed side of the medium speed range and the low load and medium load states of the high speed range, the wastegate valve 13 is controlled to be open to a predetermined opening degree or more in order to suppress the rate of increase in boost pressure to a low level, The opening degree of the throttle is controlled in accordance with the increase in the throttle opening degree.

The characteristics of the above target boost pressure are shown in Figures 3 and 4 (a) to (
C) is shown together with the conventional example.

In other words, on the low speed side of the low and medium rotation range, the wastegate valve 1 is
3 is held in the closed state and set to the same target supercharging pressure as in the conventional example. On the high speed side of the medium speed range and in the low to medium load state of the high speed range, the target supercharging pressure is set to approximately atmospheric pressure or a low pressure close to atmospheric pressure, and the load and heat load on the turbocharger 4 are significantly reduced. It is being

In relation to the characteristics of the target boost pressure set as described above, the dimensions of the first diaphragm 14a of the actuator 14 and the spring constant of the compression coil spring 14h are set, and the A duty ratio map is set, and the duty ratio map is input and stored in the ROM of the control unit 20 in advance.

As shown in Fig. 5, the above duty ratio map divides the operating region whose parameters are engine speed and load (throttle opening) into a number of small regions, and calculates the duty ratio dij for each of the small regions. This is the setting. Regarding the approximate value of the duty ratio, in the region shown in FIG.
The duty ratio is set to 100 to maintain the atmospheric pressure without introducing negative intake pressure into the second working chamber 14, and to maintain the waste gate valve 3 in a substantially fully open state in the region H of FIG.
A negative intake pressure is introduced into f.

Next, the boost pressure control routine executed by the microcomputer of the control unit 20 will be explained based on the flowchart of FIG. 6. In the figure, Si (i=
1.2.3,...) indicate each step.

When control starts after engine E is started, necessary initial settings such as clearing the RAM memory are executed (Sl).
Next, the detection signals are read from the throttle opening sensor 6a and the crank angle sensor 18 (S2), and then the engine speed is calculated from the crank angle signal and the throttle opening is calculated from the throttle opening signal (S3). The duty ratio corresponding to the engine speed and throttle opening obtained above is read out from the map (S4), and then the duty control signal corresponding to the duty ratio is sent to the three-way solenoid valve 1.
7, and the three-way solenoid valve 17 is controlled to the opening degree set by the above duty ratio (S5).
, S5 moves to 32, and S2 to S5 are repeated at minute intervals during engine operation.

Next, the operation of the turbocharged engine will be explained.

As described above, the target supercharging pressure is set to a predetermined characteristic in relation to the operating state of the engine E, and the three-way solenoid valve 17 is duty-controlled so that the target supercharging pressure has the predetermined characteristics, and the waste gate valve is activated. 13, the target supercharging pressure as shown in FIGS. 3 and 4 (a) to (C) can be maintained over the entire operating state of the engine E.

According to the characteristics of this target boost pressure, the wastegate valve 13 is maintained in a fully closed state in the low speed side of the low speed range and the middle speed range as in the conventional example, so the acceleration response when accelerating from low speed is improved. (This can also be called supercharging responsiveness) does not decrease.

On the other hand, at the high speed side of the medium speed range and the low load and medium load states of the high speed range, the wastegate valve 13 is opened by an appropriate opening degree, and a part of the exhaust gas is leaked to the wastegate passage 12. , the turbocharger 4 is controlled so that the supercharging pressure is atmospheric pressure or low pressure close to atmospheric pressure.
load is significantly reduced. As a result, the exhaust gas pressure (exhaust pressure) on the upstream side of the turbine is lowered, and the exhaust loss of the engine E is significantly improved. At the same time, due to the reduction in exhaust pressure and the reduction in the exhaust flow rate passing through the turbine 4A,
Since the heat load on the exhaust gas is significantly reduced, mixture overrich control for exhaust gas cooling can be omitted. Therefore, it is possible to significantly improve fuel efficiency under low and medium load conditions in the above rotation range (see FIG. 2). Furthermore, by reducing the heat load on the turbocharger 4, it is possible to downsize the cooling system of the turbocharger 4. It is also possible that a duty-controlled three-way solenoid valve is provided in the first communication passage 15, and that both this three-way solenoid valve and the three-way solenoid valve 17 are duty-controlled.

<First Alternative Embodiment> The above embodiment may be partially modified to be configured as shown in FIG. 7. However, the same reference numerals are given to the same parts as in the above embodiment, and the explanation thereof will be omitted.

As shown in FIG. 7, the second communication passage 16 and the three-way solenoid valve 17 are omitted, the second working chamber 14f, the atmospheric chamber 14g, and the second diaphragm 14c of the actuator 14A are omitted, and the first communication passage 15 is A three-way solenoid valve 21 which is duty-controlled in the same way as the three-way solenoid valve 17 is interposed therein.

The spring constant of the compression coil spring 14h is set to be very small, and the target supercharging pressure is set based on the third
The characteristics are set as shown in Fig. 4 and Fig. 4 (a) to (c),
A map of the duty ratio of the solenoid drive pulse of the three-way solenoid valve 21 is manually stored in advance in the ROM of the control unit 1-20A so as to have the characteristics of the target boost pressure.

Of this map, the regions corresponding to the regions 1 and 2 in FIG. 5 are approximately the same as those in the map shown in FIG. 141-, atmospheric pressure is introduced, the waste gate valve 13 is kept fully closed, and the duty ratio is set to approximately 1.00 in the region corresponding to region H, so that a relatively low supercharging pressure is applied to the first After being introduced into the working chamber 14e, the wastegate valve 13 is kept substantially fully open.

However, in order to maintain the waste gate valve 13 substantially fully open, the target supercharging pressure at this time is set to a value somewhat higher than atmospheric pressure.

When the high speed side of the medium speed range and the high load state in the high speed range, the opening degree of the three-way solenoid valve 21 is throttled, and the supercharging pressure is reduced to a small value according to the opening degree and introduced into the second working chamber 14e. The opening degree of the waste gate valve 13 will be controlled.

Second Alternative Embodiment> The above embodiment may be partially modified to have a configuration as shown in FIG. 8. However, the same reference numerals are given to the same parts as in the above embodiment, and the explanation thereof will be omitted.

As shown in FIG. 8, the actuator 2 is a solenoid type actuator 22 that drives the waste gate valve 13 and is duty-controlled and includes a linear solenoid.
2, and the intake passage 1 is provided with a pressure sensor 23 for detecting supercharging pressure. The actuator 22 can precisely control the opening degree of the wastegate valve 13 from fully closed to fully open according to the duty ratio of the drive pulse. The control unit 20B has an A/D that receives the pressure signal detected by the pressure sensor 23 and performs AD conversion.
A converter is provided.

In the ROM of the control unit 20B, the target boost pressure characteristics as shown in FIGS. 3 and 4 (a) to (c) are manually stored in advance as a map with the engine operating state as a parameter, According to the stored control program for boost pressure control, while the engine E is operating, the boost pressure detected by the pressure sensor 23 and the target boost pressure corresponding to the operating state of the engine E (this is read out from the map) ), the linear solenoid of the actuator 22 is duty-controlled so that the boost pressure becomes the target boost pressure.

However, the pressure sensor 23 is omitted, and a duty ratio map as shown in FIG. 5 is stored in the ROM so that the characteristics of the target boost pressure can be obtained, and the map is stored in the ROM to correspond to the operating state of the engine E. The duty ratio may be read from a map to control the duty of the actuator 22.

Third Alternative Embodiment> The above embodiment may be partially modified to be configured as shown in FIG. 9. However, the same reference numerals are given to the same parts as in the above embodiment, and the explanation thereof will be omitted.

Actuator 1 that drives wastegate valve 3
4B is provided, and the inside of the casing is a diaphragm 14.
A is divided into a spring chamber 14d and an operating chamber 14e, and the waste gate valve 13 is connected to the compression coil spring 1 of the spring chamber 14d.
4h, the valve is energized to close, and the first communication passage 15 is in the working chamber 14e.
The supercharging pressure is introduced into the spring chamber 14d through the second communication passage 16A, and the valve shaft 13a is provided with a stopper that regulates the maximum opening degree within the spring chamber 14h as necessary. 14i, and a throttle valve 24 is provided in the second communication path 16A.
is interposed therein, and a check valve 25 is connected to the spring chamber 14d.

The actuator 14A is connected to the control unit 2
Since it is not configured to be controlled at 0C, the target boost pressure is determined by the spring constant of the coil spring 14h and the diaphragm 14a.
By appropriately setting the pressure-receiving area of , the throttle valve 24, etc., the characteristics of the target supercharging pressure are approximately as shown in Figures 3 and 4 (a) to 4.
The settings are as shown in (c).

When the opening degree of the throttle valve 6 is small, the supercharging pressure is low and negative intake pressure is introduced into the spring chamber 14d, so the wastegate valve 13 is held fully open against the coil spring 14h. However, the full opening degree is regulated by the stopper 14i. In this way, since the wastegate valve 13 is fully opened, the supercharging pressure hardly increases and is kept at a very low pressure, but the supercharging pressure gradually increases as the throttle opening increases. However, in any case in the low, medium, or high rotation range, when the intake pressure is negative, the valve opening force due to the intake pressure and the valve opening force due to the boost pressure act, so the wastegate valve is 3 is kept fully open. However, when the intake pressure becomes positive due to an increase in the throttle opening, an outflow occurs from the check valve 25, resulting in a pressure drop at the throttle valve 24, and the spring chamber 14d has a positive pressure (lower than the intake pressure). This is called the valve-opening intake pressure). When the throttle opening reaches a point where the intake pressure becomes approximately atmospheric pressure, the valve opening force decreases rapidly, so the opening of the wastegate valve 13 becomes very small, and then as the throttle opening increases, the supercharging pressure increases. As the intake pressure increases, the intake pressure approaches the supercharging pressure, but as the pressure drop at the throttle valve 24 gradually increases, the valve opening force gradually increases until the wastegate valve 13 becomes fully open. The maximum boost pressure is set.

Since the actuator 14B of this embodiment has a simple structure, it can be implemented easily and at low cost.

[Brief explanation of drawings]

Of the drawings, Figures 1 to 9 show examples of the present invention. Figure 1 is an overall configuration diagram of an engine with a turbocharger, and Figure 2 is a diagram showing supercharging pressure, exhaust pressure, and fuel efficiency. The characteristic diagram, Figure 3 is a characteristic diagram of the target boost pressure, and Figures 4 (a) to 4 (c) are the target boost pressure, etc. in the low rotation range, medium rotation range, and high rotation range, respectively. Characteristic diagram, Fig. 5 is an explanatory diagram of the duty ratio map, Fig. 6 is a flowchart of the boost pressure control routine, Fig. 7 is a diagram corresponding to Fig. 1 of the alternative embodiment, and Fig. 8 is a diagram corresponding to Fig. 2. FIG. 9 is a diagram corresponding to FIG. 1 of another embodiment, FIG. 9 is a diagram equivalent to FIG. 1 of the third alternate embodiment, FIG. FIG. 3 is a diagram corresponding to FIG. 3 according to the prior art. E...engine with turbo supercharger, 4...turbo supercharger, 4A...turbine, 4B...compressor,
6a... Throttle opening sensor, 12... Waste gate passage, 13... Waste gate valve, 14
・14A・14B・22...Actuator, 15
...First aisle, 16/16A...Second aisle, 18...
Crank angle sensor, 20/2OA/20B...control unit. Fig. 6 Slot error Fig. 3 Fig. 4 (a) [Low rotation range] 11-14 possible Fig. 5 Engine rotation speed Lr pm

Claims (2)

[Claims] (1) In an engine equipped with a turbocharger and a wastegate valve provided in a passage bypassing a turbine of the turbocharger, a valve opening adjustment means for adjusting the opening of the wastegate valve; , when the operating state of the engine is at least a low load or medium load state in a high rotation range, the wastegate valve is opened and its opening is controlled via the valve opening adjustment means, and the opening is controlled as the engine load increases. A turbocharged engine characterized by being provided with a valve opening degree control means for mitigating an increase in supercharging pressure. (2) In an engine equipped with a turbocharger and a wastegate valve provided in a passage bypassing a turbine of the turbocharger, a valve opening adjustment means for adjusting the opening of the wastegate valve; , an operating state detecting means for detecting the engine rotation speed and load; and a predetermined characteristic of the boost pressure that is preset in a high revolution range using the engine operating state as a parameter in response to the output of the operating state detecting means. and a valve opening control means for controlling the opening of the waste gate valve via the valve opening adjustment means so that the supercharging pressure increases in accordance with an increase in engine load. Machine engine.