JPH0144742Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a boost pressure control device for an internal combustion engine equipped with a mechanically driven supercharger.

BACKGROUND ART A mechanically driven supercharger, generally called a supercharger, is equipped with a positive displacement pump, such as a Roots type or a vane type, in the intake passage of an internal combustion engine. These pumps have a rotor inside them, and these rotors are connected to the output shaft of the internal combustion engine via a pulley and a belt, and when the rotor is rotated by the engine driving force, the intake air introduced into the engine is is supercharged. This type of mechanically driven supercharger rotates at a speed that corresponds to the engine speed, so boost pressure is not affected by exhaust pressure like an exhaust turbine supercharger, and therefore the engine speed There is an advantage that a boost pressure corresponding to the number can be obtained.

However, for engines equipped with such mechanically driven superchargers, although the boost pressure corresponds to the engine speed, the boost pressure is almost determined by the supercharger capacity and pulley ratio. Therefore, if you set the boost pressure high in an attempt to improve the engine's torque in the low and medium speed range, the boost pressure will be too high in the high speed range, and while the suction efficiency will improve, the actual compression ratio will also be high. Therefore, there is a problem in that it is virtually impossible to expect an increase in output due to the influence of knocking.

Therefore, in order to prevent such overcharging,
A passage that bypasses the supercharger is provided in the engine intake passage, and a bypass valve that opens and closes depending on the engine load is installed in this bypass passage to control the boost pressure according to the engine operating conditions. Control devices have been proposed (for example, Japanese Patent Publication No. 41-8081
issue). However, this type of boost pressure control device
Since the adiabatic compressed high-temperature intake air is bypassed to the intake side and supercharged again, the temperature of the intake air increases significantly, making knocking more likely to occur, which may lead to a reduction in output. There is also a method of releasing the supercharging pressure (intake air) to the atmosphere or exhaust gas, but this poses a problem in that the air-fuel ratio of the air-fuel mixture taken into the combustion chamber cannot be sufficiently accurate.

Problems that the invention aims to solve This invention uses a simple structure to appropriately control the boost pressure in mechanically driven turbochargers, and when the boost pressure becomes excessive, the intake air is directed to the upstream side. When bypassing, the purpose is to prevent the temperature of intake air from rising, thereby preventing knocking and increasing engine output.

Means for Solving the Problems In order to solve the above problems, the present invention provides a supercharging pump in the intake passage of an internal combustion engine, one end of which opens into the housing of the pump, and the other end of which is connected to the supercharging pump. A bypass passage is provided that communicates with the intake passage upstream of the pump, and during a certain period of rotation of the supercharging pump rotor,
The bypass passage communicates with the supercharging pump outlet via a pump chamber in the pump housing,
A supercharging pressure control device for an internal combustion engine is provided, characterized in that a control valve that opens when the supercharging pressure in the intake passage downstream of the supercharging pump reaches a certain value or more is disposed in the bypass passage.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In Figure 1, 1 is the engine body, 2 is an air cleaner, 3 is an air flow meter, 4 is a throttle valve, 5 is a supercharger consisting of a Roots pump, 6 is a fuel injector, and 7 is a pulley attached to the engine crankshaft. , 8 is a pulley attached to the supercharger, and 9 is a belt.

Intake air flows in from an air cleaner 2, is calculated by an air flow meter 3, the amount of air is adjusted by a throttle valve 4, supercharged by a supercharger 5, and then injected from a fuel injector 6 according to the amount of intake air. It is mixed with fuel and flows into the engine 1. The mechanically driven supercharger 5 for supercharging intake air is a Roots pump supercharger, as shown in detail in FIGS.
A pair of roots-type rotors 20 rotate within the pump and perform a pumping action to supercharge the intake air. The supercharger 5 is connected to the crankshaft of the engine 1 via its pulley 8, belt 9, and crankshaft pulley 7, and is rotated at a rotation speed corresponding to the engine rotation speed. However, a suitable clutch (not shown) may be provided on the pulley 8 of the supercharger 5 to intermittent the driving force from the engine 1 to the supercharger 5 as appropriate.

In the present invention, a bypass passage 11 is provided, and one end of the bypass passage 11 is connected from the housing 21 of the supercharger 5 to the pump chamber 23.
The other end is connected to an intake passage portion 30a between the supercharger 5 and a throttle valve upstream thereof. As will be described in detail later, the bypass passage 11 is communicated with the pump discharge port 25 via the pump chamber 23 of the pump housing 21 during a certain period of rotation of the rotor 20 of the supercharger 5. (Second c.
figure).

As shown in FIGS. 1 and 2a, the bypass passage 11 is provided with an on-off valve 19 that is opened and closed by a diaphragm control valve 10. As shown in FIGS. The diaphragm control valve 10 has a diaphragm chamber 14 partitioned by a diaphragm 15, which diaphragm chamber 14 is connected via a passage 13 and a port 12 to a downstream intake passage section 30b of the supercharger 5. . Therefore, the supercharging pressure in the intake passage portion 30b is transmitted to the diaphragm 14, and only when the supercharging pressure reaches a certain value or more does it overcome the tension of the spring 16, causing the diaphragm 15 and the link 17 connected thereto to move as shown in the figure. Push to the bottom left. A lever 18 and an on-off valve 1 connected to this link 17 are connected to each other.
9 is rotated counterclockwise to open the bypass passage 11.

Figures 2a to 2a show the operation when the supercharging pressure in the intake passage portion 30b downstream of the supercharger 5 is above a certain value and the on-off valve 19 of the bypass passage 11 is open.
This will be explained with reference to FIG. 2d. In these figures, the rotor 20 on the upstream side of the supercharger 5 rotates clockwise as shown, and sequentially rotates in Figures 2a, 2b, and 2b.
The position will be as shown in Figures 2c and 2d. When the rotor 20 is in the position shown in FIG. 2a, the intake air flows through the rotor 20.
and the housing 21 in the direction of the arrow in the figure. The rotor 20 then rotates clockwise to the position shown in Figure 2b. Therefore, FIG. 2b shows the stroke immediately before the rotor 20 discharges the intake air to the discharge port 25 side. The intake air here has not yet undergone adiabatic compression, so its intake air temperature (Tin) is low. The rotor 20 then advances to the position of FIG. 2c. FIG. 2c shows the position of the rotor 20 just before the intake air begins to be discharged to the discharge port 25 side. Since the pressure on the discharge port 25 side (Pout) is higher than the suction air pressure (Pin) in the pump chamber 23 between the rotor 20 and the housing 21, until the rotor 20 passes through the housing opening 11a of the bypass passage 11. A part of the intake air that is about to be discharged is pushed back through the bypass passage 11 to the intake passage 30a upstream of the supercharger 5. Next, FIG. 2d shows the position immediately after the rotor 20 passes through the housing opening 11a of the bypass passage 11, and the discharge side and the suction side of the rotor 20 and the housing 21 are blocked. As a result, the intake air is no longer pushed back to the intake side (upstream side), so it is discharged to the discharge port 25 side and supercharged. That is, in this invention,
By opening and closing the bypass passage 11, the supercharging pump 5
This increases or decreases the actual discharge volume of the pump, and can achieve the same effect as a variable displacement pump or a variable speed increase (pulley) ratio pump. In addition, in Figures 2a to 2d, the shaded area in the diagram where the pressure on the suction side (Pin) acts indicates the area of the intake air before adiabatic compression, and the intake air temperature (Tin) is low. . On the other hand, the area indicated by the many points in the figure where the boost pressure (Pout) on the discharge side is acting is an area where adiabatic compression has taken place, and the temperature (Tout) there is relatively high. Therefore, in FIG. 2c, the bypass passage 1
As shown in the figure, the temperature of the intake air returned from the intake air passage 1 to the intake passage 30a is relatively low.

Note that in a region where the boost pressure in the intake passage 30b downstream of the supercharger 5 is low, the spring 16 of the diaphragm type control valve 10 in FIG.
Since the first on-off valve 19 is closed, all the intake air in the pump chamber 23 between the rotor 20 and the housing 21 of the supercharger 5 is discharged to the discharge port 25 side, and supercharging is performed.

FIGS. 3 and 4 are graphs comparing the supercharging pressure and torque between a conventional supercharging device (one that does not perform pressure control using supercharging pressure) and the supercharging pressure control device of the present invention. In FIGS. 3 and 4, A is a conventional device that is set to obtain the optimum boost pressure on the high speed side. In this case, the boost pressure on the low speed side is low (Figure 3), and therefore the output (torque) is low due to the lack of boost pressure on the low speed side (Figure 4).
figure). In addition, in Figures 3 and 4, B is a conventional device that is set to obtain the optimum boost pressure on the low speed side, and in this case, the boost pressure is reached in the high speed range (Figure 3), This results in a state in which knotting is likely to occur. In order to prevent such knocking from occurring, it is necessary to retard the ignition timing, which results in a decrease in output at high speeds (Figure 4).

In FIGS. 3 and 4, C shows the case where the boost pressure is controlled as in the present invention, and the desired optimum boost pressure is obtained in the low speed range, and on the high speed side, the bypass passage 11 (first
Overcharging is prevented by opening (Fig. 2) (Fig. 3). Therefore, in the case of the present invention, an improvement in output (torque) can be expected in all operating ranges (Fig. 4). In addition, in Fig. 4, D indicates the characteristics of a conventional device (for example, Japanese Patent Application Laid-open No. 167817/1983) in which a bypass passage with a bypass valve is provided between the suction side and the discharge side of the supercharger. Although it is a thing,
In this case, since the high-temperature intake air after adiabatic compression is supercharged again on the high-speed side, the intake air temperature on the discharge side increases, making knocking more likely to occur, resulting in a decrease in output (torque).

Effects of the invention According to the invention, when the boost pressure exceeds the set value, the intake air before adiabatic compression (discharge) is bypassed from the pump housing to the upstream side of the intake port.
There is no rise in intake air temperature due to the bypass, making knocking less likely to occur. Furthermore, since the intake air is not released to the atmosphere, the accuracy of the air-heat ratio of the air-fuel mixture can be maintained well. Therefore, improvements in output and fuel efficiency can be expected in all driving ranges.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the supercharging pressure control device of the present invention, Figs. 2a to 2d are diagrams explaining the action of the supercharging pump, and Figs. 3 and 4 are the conventional device and the device of the present invention. 3 is a graph showing a comparison of boost pressure and output of the two. 1...Engine body, 5...Supercharging pump, 1
0...Diaphragm type control valve, 11...Bypass passage, 19...Opening/closing valve, 20...Rotor, 21...
...Housing, 23...Pump chamber, 25...Discharge port, 30a, 30b...Intake passage.

Claims (1)

[Scope of utility model registration request] A mechanically driven supercharging pump 5 is provided in the intake passages 30a and 30b of the internal combustion engine, and a bypass passage 11 is provided, one end of which opens into the housing 21 of the pump, and the other end of which communicates with the intake passage 30a upstream of the supercharging pump. A certain period of rotation of the rotor 20 of the supercharging pump,
The bypass passage 11 is communicated with the supercharging pump discharge port 25 via the pump chamber 23 in the pump housing, and the bypass passage 11 is connected to the supercharging pump so that the supercharging pressure in the intake passage 30b downstream of the supercharging pump reaches a certain value or more. A supercharging pressure control device for an internal combustion engine, characterized in that control valves 10 and 19 that open when the internal combustion engine runs out are arranged.