JPH0216035Y2 - - 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, a supercharging system was developed in which a passage was provided in the engine intake passage that bypassed the supercharger, and a bypass valve that opened and closed according to the engine load was installed in this bypass passage to control the supercharging pressure according to the engine load. A pressure control device has been proposed (Japanese Patent Application Laid-Open No. 167817
issue). However, in this supercharging pressure control device, the throttle valve is located downstream of the supercharging pump, so the intake air after supercharging is throttled by the throttle valve, resulting in poor supercharging response and ignoring the problem of noise. I can't do it.

Problems to be solved by the invention This invention uses a simple structure to appropriately control the boost pressure in mechanically driven turbochargers, prevents knocking due to excessive boost pressure, and improves boost response. The purpose is to reduce noise.

Means for Solving the Problems In order to solve the above problems, the present invention provides a mechanical supercharging pump in the intake passage of an internal combustion engine, and arranges a throttle valve upstream of the supercharging pump. A bypass passage is provided from the intake passage between the throttle valve and the supercharging pump to the downstream of the supercharging pump, and the bypass passage is opened when the positive pressure downstream of the supercharging pump increases, and the bypass passage is opened when the positive pressure downstream of the supercharging pump becomes large. A supercharging pressure control device for an internal combustion engine is provided, which includes a control valve that opens when the absolute value of negative pressure downstream of the valve and upstream of a supercharging pump becomes large.

The control valve has a valve body that can be pushed open by positive pressure downstream of the supercharging pump, and a diaphragm connected to the valve body has a negative pressure downstream of the throttle valve and upstream of the supercharging pump. It can be a diaphragm type control valve adapted to be applied in the opening direction.

The control valve is composed of two diaphragm control valves installed in parallel in the bypass passage, one valve opens when the positive pressure downstream of the supercharging pump exceeds a predetermined value, and the other valve opens when the positive pressure downstream of the supercharging pump exceeds a predetermined value. It is also possible to open the valve when the absolute value of the negative pressure downstream of the valve and upstream of the supercharging pump exceeds a predetermined value.

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 measured by an air flow meter 3, the amount of air is adjusted by a throttle valve 4, is 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 that supercharges intake air is, for example, a Roots pump type supercharger, in which a pair of Roots-type rotors rotate within a housing and perform a pumping action to supercharge intake air. It is something to do. Of course, a supercharger consisting of a vane pump may be used instead of the roots pump. The supercharger 5 is
It is connected to the crankshaft of the engine 1 via the pulley 8, belt 9, and crankshaft pulley 7, and is rotated at a rotation speed corresponding to the engine rotation speed. However, by providing a suitable clutch (not shown) on the pulley 8 of the supercharger 5,
The driving force from the engine 1 to the supercharger 5 may be interrupted as appropriate.

As shown in FIG. 1, the throttle valve 4 is provided upstream of the supercharger 5, and the intake passage portion 20a between the throttle valve 4 and the supercharger 5 is connected to the supercharger 5.
Bypass passages 10, 10a,
Connect at 10b. That is, bypass passage 1
One end 10a of 0 is open to the upstream 20a of the supercharger 5, and the other end 10b is open to the downstream 20b of the supercharger 5. A diaphragm control valve 30 is provided in the middle of this bypass passage 10.

This diaphragm type control valve 30 has a valve body 11 that opens and closes an opening 17 on the other end 10b side of the bypass passage 10, and this valve body 11 is connected to a diaphragm 12 and is moved by a spring 13 in a direction in which the opening 17 is closed. is under pressure. The diaphragm chamber 14 is connected to an intake passage portion 20a between the throttle valve 4 and the supercharger 5 by a negative pressure passage 15.

When the engine is lightly loaded, especially when the engine speed is relatively high, the opening degree of the throttle valve 4 is small and the rotation of the supercharger 5 is high, so the negative pressure (absolute value) in the intake passage portion 20a is The negative pressure in the diaphragm chamber 14 of the control valve 30 overcomes the spring 13 and pulls the diaphragm 12 and the valve body 11 upward, and the bypass passage 10
(Opening 17) is opened. Yotsute supercharger 5 downstream 2
The positive pressure of 0b flows into the upstream portion 20a of the supercharger 5, and as a result, the absolute value of the negative pressure in the intake passage portion 20a upstream of the supercharger 5 is prevented from becoming too high and is maintained within a certain range. Ru. That is, when the negative pressure in the passage 20a increases, the air density becomes thinner and the cooling effect decreases, causing the supercharger to overheat, but the present invention prevents this. Further, in such an operating state, supercharging is not necessary, and by suppressing supercharging, the supercharger driving torque can be reduced and fuel efficiency can be improved.

On the other hand, when the engine is under high load, positive pressure supercharged by the supercharger 5 is applied from the intake passage section 20b to the passage section 10b of the bypass passage 10, and the control valve 3
The valve body 11 is pushed upward by overcoming the spring 13 of 0, and the bypass passage 10 (opening 17) is opened. This prevents the positive pressure downstream 20b of the supercharger 5 from becoming too high and maintains it within a certain range.

Figure 2 shows the turbocharger upstream 2 relative to the engine speed.
This diagram shows the relationship between 0a (negative pressure) and downstream 20b (positive pressure), where the negative pressure upstream of the supercharger is maintained almost constant regardless of the engine speed, and the positive pressure downstream of the supercharger is high. It is controlled to a constant value within the rotation range, and the supercharging pressure is prevented from becoming too high. The set pressure when the diaphragm control valve 30 opens due to the negative pressure is determined by the diameter of the diaphragm 12 and the spring 1.
3, and the set pressure for opening the valve with the positive pressure can be determined by the diameters of the diaphragm 12 and the seat of the valve body 11, and the strength of the spring 13.

FIG. 3 shows another embodiment of the boost pressure control device of the present invention. The difference from the embodiment of FIG. 1 is that the bypass passage 10 is branched into parallel passages 21 and 22 in the middle. diaphragm control valve 40,
50 was set. Each control valve 40, 50 has an opening 41,
It has valve bodies 42, 52 for opening and closing 51, diaphragms 43, 53 connected to these valve bodies, springs 44, 54, and the like. The negative pressure chamber 45 of one control valve 40 is connected to the intake passage 20a downstream of the throttle valve 4 and upstream of the supercharger 5 via a negative pressure passage 46, and the absolute value of the negative pressure in the intake passage 20a is constant. When this happens, the diaphragm 43 is pulled up against the spring 44, and the valve body 42 opens the opening 41.
The positive pressure chamber 55 of the other control valve 50 is connected to the intake passage 20b downstream of the supercharger 5 via a positive pressure passage 56, and the intake passage 20b supercharged by the supercharger 5.
When the positive pressure of 0b exceeds a certain level, spring 5
4 and push up the diaphragm 53 against the valve body 5.
2 opens the opening 51. Therefore, when the supercharging pressure becomes excessive, excess air is relieved into the intake passage 20a upstream of the supercharger 5, and the supercharging pressure is prevented from becoming too high.

Effects of the invention According to the invention, prevention of supercharger overheating and improvement of fuel efficiency when the engine is running at high speeds and under light load, and prevention of overcharging at high engine speeds, are achieved using a simple boost pressure control device. be done. Moreover, this also achieves prevention of knocking, improvement of overheating response, reduction of noise, etc.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the boost pressure control device of the present invention, FIG. 2 is a diagram showing the characteristics of pressure control by the control device of the present invention, and FIG. 3 is a schematic diagram of a second embodiment of the present invention.
It is. 1...Engine body, 4...Throttle valve, 5
...supercharger (pump), 10...bypass passage,
11...Valve body, 12...Diaphragm, 20a,
20b...Intake passage, 30, 40, 50...Diaphragm type control valve.

Claims (1)

[Claims for Utility Model Registration] 1. A mechanically driven supercharging pump 5 is provided in the intake passage of an internal combustion engine, a throttle valve 4 is disposed upstream of the supercharging pump 5, and the throttle valve 4 and the supercharging pump 5 A bypass passage 10 extending from an intake passage portion 20a between the
a control valve 30 which opens the bypass passage 10 when the positive pressure downstream of the supercharging pump 20b becomes large, and opens when the absolute value of the negative pressure downstream of the throttle valve and the upstream supercharging pump 20a becomes large;
40, 50. A supercharging pressure control device for an internal combustion engine. 2. The control valve 30 has a valve body 11 that can be pushed open by positive pressure at the downstream side of the supercharging pump 20b, and a diaphragm 12 connected to the valve body 11 has a valve body 12 connected to the valve body 11 downstream of the throttle valve and connected to the upstream side of the supercharging pump 20a. The device according to claim 1, which is a registered utility model, and comprises a diaphragm type control valve in which negative pressure is applied in a direction to open the valve body 11. 3 the control valves are two diaphragm control valves 40 provided in parallel in the bypass passage 10;
50, one valve 50 opens when the positive pressure at the downstream side of the supercharging pump 20b exceeds a predetermined value, and the other valve 40 opens when the absolute value of the negative pressure at the upstream side of the supercharging pump 20a exceeds a predetermined value downstream of the throttle valve. The device according to claim 1 of the utility model registration, which opens when the device is crossed.