JPH0415948Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a supercharging control device for an internal combustion engine that performs two-stage supercharging using two superchargers: a turbocharger and a supercharger.

[Conventional technology]

Conventionally, internal combustion engines in which a turbocharger and a supercharger are arranged in series are already known.
(For example, Japanese Patent Publication No. 41-8081 or Utility Model Application Publication No. 1983-8081)
(See Publication No. 26235). This is a combination of a supercharger that can highly supercharge the intake air in the low-speed range and a turbocharger that can highly supercharge the intake air in the high-speed range. In addition to preventing deterioration in responsiveness when charging, the aim is to obtain high supercharging over a wide range from low speeds to high speeds, and it is also possible to perform supercharging only by turbocharger at high speeds. In the case of a turbocharger, the supercharging pressure is controlled by opening a wastegate valve, and in the case of a supercharger, it is controlled by opening a bypass passage connecting the front and rear parts.

Now, as shown in Figure 2, the fuel efficiency of an internal combustion engine is better when supercharging is performed using a turbocharger (indicated by a solid line in the figure), and when it is supercharging using a supercharger (indicated by a broken line in the figure). ) better than This is because the output generated by the internal combustion engine is used to drive the supercharger. on the other hand,
Even in the case of an internal combustion engine that is equipped with both a turbocharger and a supercharger, fuel efficiency deteriorates in the operating range where the supercharger is driven. For this reason, during two-stage supercharging using both a supercharger and a turbocharger, when the supercharging pressure of the turbocharger increases, the variable transmission reduces the speed change of the transmission that drives the supercharger, and the supercharger This is an attempt to reduce the load (Special Public Interest Publication Act, 1977).
(See Publication No. 14165).

[The problem that the idea attempts to solve]

In conventional two-stage supercharging systems, the supercharger is shut off at high speeds, and at the same time a bypass valve opens the supercharger bypass passage to switch to single-stage supercharging using only the turbocharger. During this switching, the engine load and boost pressure fluctuated considerably, resulting in the feeling of torque shock in some cases. Furthermore, when accelerating again after deceleration, there was a problem in that high responsiveness could not be obtained due to a delay in the response of the electromagnetic clutch that continuously drives the supercharger and a delay in the rise of supercharging pressure of the supercharger.

However, if the supercharger is driven by a transmission device with a variable gear ratio, the device becomes complicated and its control is not easy. The present invention attempts to solve these problems of the prior art.

[Means to solve the problem]

As a means for solving the above problems, the present invention includes: a turbocharger provided on an intake passage; a supercharger provided in series on the downstream side of the turbocharger on the intake passage;
A waste gate valve provided in a bypass passage of a turbine of the turbocharger, a relief passage that communicates between an upstream side and a downstream side of the supercharger of the intake passage, and a relief valve that opens and closes the relief passage. ,
Both the waste gate valve and the relief valve are configured to be opened and closed by the intake pressure in the intake passage downstream of the supercharger, and the supercharger is driven when the engine speed is below a predetermined engine speed. The waste gate valve opening pressure at which the waste gate valve starts opening in the supercharge drive region is set to a higher pressure side than the relief valve opening pressure at which the relief valve starts opening. ,
Further, the valve opening timings of the relief valve and the waste gate valve are both placed within the driving range of the supercharger, and the relief valve and the wastegate are in a state where the supercharger is being driven. An internal combustion engine supercharging control device characterized in that a valve is set to start opening.

[Effect]

Since the supercharging control device for an internal combustion engine according to the present invention has the above-described configuration, the turbocharger does not perform an effective supercharging action while the engine speed is low, so the supercharging action is almost exclusively performed by the supercharger. However, as the rotational speed increases, the supercharging effect of the turbocharger increases, resulting in a substantial two-stage supercharging state. When the total supercharging pressure of both exceeds a predetermined value, the relief valve begins to open, and the pressurized intake air starts to be relieved from the downstream side to the upstream side of the supercharger. Therefore, the contribution of the supercharger to the boost pressure decreases accordingly, and the main force of supercharging shifts to the turbocharger.

When the rotational speed further increases and the boost pressure exceeds the next predetermined value, the waste gate valve also begins to open, and its opening degree is adjusted so that the total boost pressure does not exceed the maximum boost pressure. Then, in the high rotation speed and high load range, the relief valve becomes fully open, resulting in a state of first-stage supercharging using only the waste gate valve. Thereafter, the drive of the supercharger is cut off at a predetermined engine speed. In this state, the relief passage and the relief valve serve to send supercharged intake air from the turbocharger directly to the engine by using the intake passage as a bypass passage for the supercharger from the upstream side to the downstream side.

On the other hand, when the load on the engine increases and the engine speed begins to drop, the supercharger starts driving even though the engine is idling. Furthermore, the wastegate valve begins to close, reducing the amount of exhaust gas that bypasses the turbocharger, thereby increasing the supercharging pressure by the turbocharger. However, if the supercharging pressure still does not reach the predetermined value, the relief valve also begins to close, increasing the effective supercharging action of the supercharger. As aforementioned,
In this state, the supercharger has already been activated and is rotating at a sufficiently high rotational speed, so when the relief valve begins to close, the amount of intake air that is relieved decreases and immediately contributes to an increase in supercharging pressure. In this way, the boost pressure can be kept as constant as possible over a wide engine speed range. Furthermore, when the waste gate valve and the relief valve are closed, the supercharger has already started driving, so the torque shock caused by switching is small and the responsiveness is high.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

The figure shows an internal combustion engine to which an embodiment of the present invention is applied. In the figure, a piston 12 is slidably supported in a cylinder bore 11 formed in an engine body 10, and a combustion chamber 13 is formed above the piston 12. The combustion chamber 13 has an intake passage 14
The exhaust passage 15 communicates with the exhaust passage 15.

The air cleaner 16 is provided at the most upstream side of the intake passage 14, and the air flow meter 17 is provided at the downstream side thereof. Further downstream, a compressor 19 of the turbocharger 18 is provided, and a supercharger 2 is provided downstream of this compressor 19.
0 is set. The throttle valve 21 is provided between the compressor 19 of the turbocharger 18 and the supercharger 20, and changes the flow area in the intake passage 14 in conjunction with an accelerator pedal (not shown). Supercharger 2 of intake passage 14
A surge tank 23 is formed downstream of 0.

On the other hand, a turbine 25 of the turbocharger 18 is provided in the middle of the exhaust passage 15, and a bypass passage 26 that bypasses the turbine 25 is formed. In the turbocharger 18 , a turbine 25 is rotationally driven by exhaust gas passing through the exhaust passage 15 , which rotates a compressor 19 to increase the pressure of air taken in from the intake passage 14 . The wastegate valve 27 opens and closes the bypass passage 26 to adjust the amount of exhaust gas supplied to the turbine 25 and the turbocharger 18.
control the rotation of The actuator 28 that opens and closes the waste gate valve 27 has a conventionally known configuration, and the diaphragm 3 is connected to the inside of the shell 29.
0 to form a pressure chamber 31, and a surge tank 23 is connected to the pressure chamber 31 via a passage 32.
The internal pressure is transmitted. The surge tank 23 is provided on the intake passage 14 on the downstream side of the supercharger 20. Therefore,
When the pressure in the pressure chamber 31, that is, the supercharging pressure on the downstream side of the supercharger 20 overcomes the elastic force of the spring 33, the waste gate valve 27 opens the bypass passage 26, and the exhaust gas passing through the turbine 25 is released. The outlet pressure of the compressor 19 of the turbocharger 18 is made constant by reducing the amount.

The air pressurized by the compressor 19 of the turbocharger 18 is regulated by the throttle valve 21 and flows into the supercharger 20 . The drive shaft of the supercharger 20 is connected to a pulley 35 having an electromagnetic clutch.
is connected to a crank pulley 36 provided on the engine body 10 by an endless belt 37.
The supercharger 20 is therefore driven via the crank pulley 36 when the electromagnetic clutch is in the engaged state. The upstream and downstream sides of the supercharger 20 in the intake passage 14 are the relief passage 3.
8, and a relief valve 39 is provided in the middle of the relief passage 38 to open and close it. An actuator 40 that opens and closes the relief valve 39 is configured by partitioning the inside of a shell 41 with a diaphragm 42 to form a pressure chamber 43, and the diaphragm 42 is connected to the relief valve 39. The actuator 2 is located in the pressure chamber 43.
Similarly to the pressure chamber 31 of No. 8, the pressure inside the surge tank 23 is transmitted through the passage 45, and this pressure, that is, the supercharger 2
When the boost pressure on the downstream side of 0 overcomes the elastic force of the spring 44 provided in the chamber on the opposite side of the pressure chamber 43, the relief valve 39 opens the relief passage 38.

Note that the relief valve 39 in the illustrated embodiment has a relief passage 38 parallel to the supercharger 20.
As shown in the figure, it has a structure that opens from the upstream side to the downstream side of the intake passage 14, so if something happens, such as when the supercharger 20 breaks down and stops rotating, If for some reason the pressure on the upstream side of the supercharger 20 becomes higher than the pressure on the downstream side by more than a predetermined value determined by the strength of the spring 44, the actuator 4
It also has the effect of maintaining the intake air flow by automatically opening the valve without depending on the operation of zero and forming an intake passage that bypasses the supercharger 20.

The electromagnetic clutch of the supercharger 20 is switched and controlled by an electronic control section 50 equipped with a microcomputer. The electronic control unit 50 outputs an ON command to the pulley 35 to connect the electromagnetic clutch based on a signal indicating the engine load input from a load sensor (not shown) during high-load operation when the throttle valve 21 is opened. Therefore, the rotors 20a and 20b of the supercharger 20 are rotationally driven by the rotation of the crank pulley 36, and start supercharging. Further, when the flow rate of exhaust gas increases due to high-load operation of the internal combustion engine, the turbocharger 18 also starts a supercharging action accordingly, and two-stage supercharging is performed.

Now, during supercharging by the turbocharger 18 and the supercharger 20, the wastegate valve 28 and the relief valve 39 set the supercharging pressure on the downstream side of the supercharger 20, that is, the pressure in the surge tank 23, to the set supercharging pressure. Open and close as shown. Here, the supercharging pressure when the waste gate valve 27 starts opening, that is, the waste gate valve opening pressure, is higher than the supercharging pressure when the relief valve 39 starts opening, that is, the relief valve opening pressure. springs 33 and 44 so that they are higher than
The spring constant is determined. Therefore, when the pressure inside the surge tank 23 reaches a predetermined value, the relief valve 39 begins to open, and as a result, some of the air downstream of the supercharger 20 passes through the relief passage 38 and flows upstream. The fuel starts to circulate, and supercharging by the supercharger 20 is controlled. However, at this time, the electromagnetic clutch remains connected, and the supercharger 20 is still in the driving state. On the other hand, the waste gate valve 27 of the turbo charger 18 is connected to the relief valve 3.
After the pressure in the surge tank 23 increases further and reaches a predetermined value after the valve 9 is opened, the valve opens and supercharging by the turbocharger 18 is restricted. That is, after the relief valve 39 is fully opened, the waste gate valve 27 opens when the supercharging pressure further increases to suppress a further increase in the supercharging pressure.

When the internal combustion engine enters a high-speed, high-load operating state, in order to perform supercharging only by the turbocharger 18, the electronic control unit 50 activates the supercharger 2 based on a signal from a rotational speed sensor (not shown).
Disconnect the electromagnetic clutch of 0. As a result, the supercharger 20 substantially stops, but since the pressure inside the surge tank 23 is higher than the opening pressure of the relief valve 39, the relief valve 39 remains open, and most of the intake air is released into the relief valve. aisle 3
8 and flows into the surge tank 23. At this time, the relief passage 38 is connected to the super charger 20.
This will serve as a bypass passage.

Figures 3a and 3b show the relationship between engine speed and supercharging pressure, and Figure 3a shows that the opening pressure _PW of the waste gate valve 27 is higher than the opening pressure _PB of the relief valve 39.
3b, the relief valve 39
The case where the valve opening pressure P _B of is higher than the valve opening pressure P _W of the waste gate valve 27 is shown. As can be seen by comparing Fig. 3 a and b at a specific engine speed N, the higher the valve opening pressure P _W is than the valve opening pressure P _B , the more the supercharging pressure S due to the supercharger 20
is smaller than the supercharging pressure T caused by the turbocharger 18, thus making it possible to improve fuel efficiency. Further, in the low rotation range, the turbocharger 18 hardly acts, but the supercharger 20 operates, so the supercharging pressure increases quickly.

Next, when the rotational speed decreases due to an increase in load from the supercharging state using only the turbocharger 18 at high rotational speeds, the electromagnetic clutch is connected by the operation of the electronic control section 50, and the supercharger 2
Driving of 0 is resumed. At this time, the relief valve 39 and wastegate valve are still at least partially open, so no shock will occur due to the operation of the supercharger 20. Furthermore, if the rotation speed decreases due to an increase in load, the shock will occur first. The waste gate valve 27 is fully opened, but the relief valve 39 is fully closed only when the turbocharger 18 alone causes the supercharging pressure in the surge tank 23 to fall below a predetermined value, and the relief passage 38
Since the flow through the supercharger 20 is blocked, the supercharger 20 performs full supercharging and prevents a drop in supercharging pressure.

In this way, when the relief valve 39 opens and closes again, the electromagnetic clutch is not simultaneously disconnected and connected as in the conventional case, but the opening and closing of the relief valve 39 is performed at high rotation speeds. This sometimes occurs when the supercharger 20 is in operation, and since the electromagnetic clutch is engaged and engaged while the relief valve 39 is open, the load and boost pressure may fluctuate greatly when the supercharger 20 shuts off or restarts the supercharging action. Therefore, there is no risk of shock occurring due to fluctuations in engine torque. Also, Super Charger 2
Supercharger 20 also restarts the supercharging action of 0.
Since this is done by closing the relief valve 39 when the engine is already driven and its rotational speed is sufficiently high, there is also a drop in acceleration response due to a delay in the response of the electromagnetic clutch or a delay in the increase in the rotational speed of the supercharger 20. It doesn't happen.

Furthermore, according to this embodiment, it is possible to reduce the supercharging pressure S by the supercharger 20 without using any special equipment, thereby improving fuel efficiency and increasing the speed over a wide range from low speeds to high speeds. high output can be obtained. Furthermore, when the supercharger 20 is stopped at high rotation speed, the relief passage 38 is open and serves as a bypass passage for the supercharger 20, so the rotational resistance for making the rotors 20a and 20b idle is reduced. Engine output can be improved.

Note that the pressure for opening the waste gate valve 27 and the relief valve 39 may be introduced from a portion other than the surge tank 23 as long as the intake passage 14 is downstream of the supercharger 20.

[Effect of idea]

As described above, according to the present invention, in a two-stage supercharged internal combustion engine equipped with a turbocharger and a supercharger that is driven intermittently, the shock caused by the intermittent supercharging by the supercharger can be avoided with a simple configuration. This has the effect of preventing delays in response and response, as well as improving fuel efficiency.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is a graph showing the fuel efficiency of an internal combustion engine in each case where a supercharger and a turbocharger are installed. Figure 3a shows the supercharging pressure when the opening pressure of the waste gate valve is set higher than the opening pressure of the relief valve. FIG. 3b is a graph showing the supercharging pressure when the opening pressure of the relief valve is set higher than the opening pressure of the waste gate valve. 14...Intake passage, 15...Exhaust passage, 18...
...Turbocharger, 20...Supercharger, 25...Turbine, 27...Wastegate valve, 38...Relief passage, 39...Relief valve.

Claims (1)

[Scope of utility model registration request] A turbocharger installed on the intake passage,
a supercharger provided in series on the downstream side of the turbocharger on the intake passage; a wastegate valve provided in the bypass passage of the turbine of the turbocharger; and a wastegate valve provided in the intake passage upstream and downstream of the supercharger. and a relief valve that opens and closes the relief passage, and both the waste gate valve and the relief valve are opened and closed by the intake pressure in the intake passage downstream of the supercharger. The supercharger is driven in a supercharge drive range below a predetermined engine speed, and the wastegate valve opening pressure at which the wastegate valve starts opening is:
The relief valve is set to a higher pressure side than the relief valve opening pressure at which the relief valve starts opening, and the opening timings of the relief valve and the waste gate valve are both within the driving range of the supercharger. A supercharging control device for an internal combustion engine, wherein the relief valve and the waste gate valve are set to start opening when the supercharger is driven.