JPH01104922A - Engine with supercharger - Google Patents

Abstract

PURPOSE:To secure an excellent scavenging effect owing to supercharging pressure of a supercharge by setting up a throttle valve in each independent suction passage so as to make suction side pressure higher than exhaust pressure at a partial load area and idle low speed maintainable at the time of idle running. CONSTITUTION:In an engine 1, a compressor 10a of a turbosupercharger 10 is set up in a main suction passage 7. In this case, each of intakes valves 3 and exhaust valves 4 installed in multiple cylinders 2 is set so as to cause an overlap value at the valve opening time to become -10 deg.C at a crank angle when each valve lift value of these intake and exhaust valves 3, 4 is 1mm. On the other hand, each of throttle valves 15 is set up in and around each intake port in a lot of auxiliary suction passages 14 branched off from a surge tank. In each throttle valve 15, pressure at the downstream side of these throttle valves becomes higher than exhaust pressure during the overlap period of these intake and exhaust valves 3, 4, and each throttle valves is set up in a position where idle low speed is maintainable at the time of idle running.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a supercharged engine in which a supercharger is provided in an intake passage.

(Prior Art) In general, in order to improve output, it is widely known that a supercharger is provided in the intake passage.

By the way, in a supercharged engine, the compression ratio is set low to prevent knocking, and combustibility deteriorates in the non-supercharged medium and low load range, but the compression ratio cannot be increased. .

In addition, as a method to prevent knocking, the residual exhaust gas in the combustion chamber, which causes knocking, is removed by using intake pressure (supercharging pressure) from the time the intake valve begins to open until the exhaust valve closes. It is known to scavenge during a so-called overlap period (see, for example, Japanese Patent Laid-Open No. 185628/1983).

(Problem to be solved by the invention) However, in such a device, a sufficient scavenging effect can be obtained in a high load range where the boost pressure is high, but in a medium to low load range where the boost pressure is low, the intake pressure is not higher than the exhaust pressure, and a sufficient scavenging effect cannot be obtained.

The present invention has been made in view of the above points, and an object of the present invention is to provide a supercharged engine that can obtain a scavenging effect by the supercharging pressure of the supercharger and suppress knocking at least in a medium load range. purpose.

(Means for Solving the Problems) The present invention is based on an engine in which a supercharger is interposed in the intake passage.

In order to achieve the above object, the present invention is configured such that the amount of overlap between the opening timings of the intake valve and the exhaust valve is 110 degrees or more in terms of crank angle when the lift amount of the intake and exhaust valves is 1 m. A throttle valve is provided in the independent intake passage to each cylinder, and the throttle valve is configured such that the pressure on the downstream side of the throttle valve at partial load is lower than the exhaust pressure during the overlap period of the intake and exhaust valves. It is characterized by being located at a position where the engine speed is high and a low idle speed can be maintained during idling operation.

(Function) In the partial load region, the supercharging pressure from the supercharger causes the intake side pressure (pressure on the downstream side of the throttle valve) to be higher than the exhaust pressure during periods other than the intake period, so the pressure difference causes the so-called During the overlap period, residual exhaust gases in the combustion chamber are scavenged.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In Figures 1 and 2 showing the overall configuration of a supercharged engine, 1 is the engine body, and four cylinders 2, 2, 2
．． 2, an intake port 3 and an exhaust port 4 are opened in the combustion chamber of each cylinder 2, and each intake port 3 and exhaust port 4 are opened and closed by an intake valve and an exhaust valve.

The amount of overlap between the opening timings of the intake and exhaust valves is set so that when the valve lift amount of the intake and exhaust valves is 1lTIIfi, the crank angle is 110@ or more (see Figure 3). . Furthermore, if we consider the case when the valve lift amount is 1- as a reference, the intake valve will open about 20 degrees later than the point when it actually starts to open, and it will close about 20 degrees earlier than the point when the exhaust valve actually closes. When the openings of the intake and exhaust valves overlap, the overlap is at least about 30''.Furthermore, if the overlap amount is 110°, sufficient scavenging effect cannot be obtained. Confirmed by experiment.

7 is a main intake passage, from the upstream side, an air cleaner 8, an air flow meter 9, a compressor 10 of a turbo supercharger 10.
a, an intercooler 11, and a surge tank 13 are arranged in this order, and the surge tank 13 branches into four independent sub-intake passages 14, 14, 14, 14, and the downstream end of each side intake passage 14 is It communicates with the combustion chamber of each cylinder through the intake port 3.

In each of the sub-intake passages 14, a throttle valve 15 is provided in the vicinity of the intake port 3 so as to be openable and closable, and a fuel injection nozzle 16 is provided downstream of the throttle valve 15.

On the other hand, each sub-exhaust passage 18 whose downstream portions merge to form the main exhaust passage 17 also communicates with the combustion chamber of each cylinder through the exhaust port 4. A turbine 10b of the turbocharger 10 is disposed in this main exhaust passage 17, and the upstream and downstream sides of the turbine 10b are connected through a bypass passage 19, and a waist that limits the maximum value of supercharging pressure is connected to the bypass passage 19. A gate valve 20 is provided.

By the way, regarding the position of the throttle valve 15, in order to maintain a low idle rotation state, the volume of the sub-intake passage 14 downstream of the throttle valve 15 is such that the filling efficiency during idle operation is at most 20% or less. It is set as follows. That is, if the volume of the auxiliary intake passage 14 from the throttle valve 15 to the intake valve is V O + the single-chamber stroke volume is vh, it is necessary to satisfy Vo<0.2X VA.

With the above configuration, as shown in FIG. 2, as the engine load increases, the opening degree of the throttle valve 15 gradually increases, and accordingly, the pressure P1 downstream of the throttle valve 15 also gradually increases. .

The pressure P2 in the surge tank 13 downstream of the compressor loa of the turbocharger 10 is increased by the supercharging action of the compressor 10a, and reaches approximately the maximum pressure in the medium load region. This pressure increase is caused by the wastegate valve 2
o is suppressed by gradually opening.

By the way, the exhaust pressure P3 gradually increases as the engine load increases, but the pressure P3 in the surge tank 13
2 is much larger than the pressure P1 downstream of the throttle valve 15. Since the upstream and downstream sides of the throttle valve 15 communicate through the valve clearance, the pressure P1 becomes relatively large under the influence of the pressure P2, and the amount of intake air is throttled. Therefore, even if the opening degree of the throttle valve 15 is small, the region where the pressure P is larger than the exhaust pressure P3 is expanded not only to the high load region but also to the medium load region.

Therefore, while the intake valve is closed, the throttle valve 1
5.The downstream pressure P1 is increased and becomes higher than the exhaust pressure P3, so when the intake valve opens, the intake side pressure P□ is higher than the exhaust pressure P3, and this pressure difference causes the exhaust valve to open. Scavenging is performed during the overlap period until closing.

When the load is low, the throttle valve 15 is
5 is small, and negative pressure is generated downstream of the throttle valve 15, but this negative pressure also has the function of preventing backflow from occurring due to the large overlap amount and from malfunctioning. In other words, an increase in residual exhaust gas during low load is prevented.

Note that in an independent throttle engine as in the present invention, seals, valves,
High processing precision is required for passages, etc., and the amount of leakage must be suppressed as much as possible during periods other than the intake period.
Since it is not possible to maintain a low-speed idle state, it is necessary to suppress the clearance as much as possible, but by providing the auxiliary valve 31 in the main intake passage 7, the two valves 15° 31
Since the amount of intake air can be controlled by this, high machining accuracy is no longer necessary.

(Effects of the Invention) As described above, the present invention has a throttle valve arranged so that the intake side pressure becomes higher than the exhaust pressure in the partial load range and maintains a low idle speed during idling operation. It is possible to effectively scavenge residual exhaust gas without damaging the engine, and it is also possible to suppress knocking.

Therefore, high compression is also possible.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is a schematic plan view showing the overall configuration of a supercharged engine, Fig. 2 is a diagram showing the relationship between pressure and load, and Fig. 3 is a diagram showing the relationship between intake and exhaust. It is an explanatory view of the amount of overlap of valve opening timings. 1...Engine body, 2...Cylinder, 3
...Intake valve, 4...Exhaust valve, 7...
... Main intake passage, 10 ... Turbo supercharger, 1
4...Sub-intake passage, 15...Throttle valve, 17...Main exhaust passage, 18...
Sub-exhaust passage.

Claims (1)

[Claims] (1) In an engine with a supercharger installed in the intake passage, the amount of overlap between the opening timings of the intake and exhaust valves is -10 in crank angle when the lift amount of the intake and exhaust valves is 1 mm. ° or more, a throttle valve is provided in the independent intake passage to each cylinder, and the throttle valve is set so that the pressure at the downstream side of the throttle valve at partial load is set such that the pressure at the downstream side of the throttle valve is set to be equal to or higher than the overlap period of the intake and exhaust valves. A supercharged engine characterized in that the inside of the engine is located at a position where the pressure is higher than the exhaust pressure and a low idle speed can be maintained during idling operation.