JPS5815606B2 - Reciprocating engine supercharging device - Google Patents

Description

Detailed Description of the Invention The present invention opens an intake port and a supercharging port in a combustion chamber, and in addition to the air-fuel mixture taken in from the intake port by negative intake pressure, pressurized air or the air-fuel mixture is transferred to the supercharging port. The present invention relates to an improvement in a supercharging device for a reciprocating engine that is supplied from a reciprocating engine.

Generally, the technical concept of increasing the charging efficiency and improving the output performance of the engine by pressurizing all of the intake air during the intake stroke of the engine using a supercharger is well known.

However, in this case, all the intake air drawn into the engine passes through the supercharger, which causes problems such as the supercharger itself creating ventilation resistance, which in turn reduces charging efficiency and results in a decrease in output performance. On the other hand, all of the intake air taken into the engine is adiabatically compressed and heated to high temperature by the supercharger, so there is a problem that the density of the intake air becomes low and the charging efficiency is not sufficiently improved. In order to avoid this problem, the supercharger must be made larger.

Therefore, conventionally, in addition to the intake port that sucks in the air-fuel mixture using the engine's intake negative pressure, a supercharging port that supplies air or air-fuel mixture pressurized by the turbocharger has been installed, allowing natural intake due to the negative pressure and Intake is performed with supercharging,
A turbocharger with a relatively small capacity that aims to improve charging efficiency has been proposed.

However, even with this conventional system, there are several problems that must be solved in order to perform more effective supercharging.

In other words, the pressurized air supplied from the supercharging port is heated to a high temperature due to adiabatic compression by the supercharger, so if pressurized air is supplied from the supercharging port when there is sufficient suction capacity by the intake port, This results in a problem in that the suction ability of the air-fuel mixture is inhibited, the supply ratio of high-temperature pressurized air increases, and blowback occurs from the supercharging port to the intake port, making it impossible to obtain a sufficient supercharging effect.

Regarding this point, the applicant has determined that the opening and closing timing of the timing valve that opens and closes the supercharging port at a predetermined timing is
We have already proposed an engine supercharging system that opens the supercharging passage and supplies pressurized air or air-fuel mixture at the end of the intake stroke, when intake from the intake port ends.

In a device equipped with such a timing valve, since supercharging is performed for a predetermined period from the end of the intake stroke, blowback from the supercharging port to the intake port can be virtually eliminated, and even a small-capacity supercharger can provide reliable performance. It has the advantage of being able to perform supercharging.

However, on the other hand, since the supercharging timing is limited to a certain period from the end of the intake stroke, the supercharging time per cycle becomes extremely short, especially when the engine is running at high speed, and as a result, effective supercharging becomes difficult in practice. However, there is a problem in that the original purpose of improving engine output cannot be achieved.

In other words, the inertia of the intake air flowing through the intake port increases as the engine speed increases, and on the other hand,
Since blowback from the supercharging port to the intake port is largely controlled by this intake inertia, the timing at which supercharging starts is determined by the engine speed (on the other hand, if the engine speed remains unchanged, the timing between the intake port and the supercharging port) By reducing the overlap between the In addition, if the overlap described above is increased, air flow back to the main intake port can be prevented in situations where there is a large pressure difference between the supercharging port and the working chamber at high rotation speeds where the intake inertia of the intake port is large. Although it is possible to start supercharging without causing a problem and obtain sufficient supercharging efficiency, there is a problem in that at low rotation speeds, air blows back from the supercharging port to the intake port, making it impossible to obtain sufficient supercharging efficiency.

In other words, in the conventional system described above, the timing valve opens and closes at fixed timings, so
Effective supercharging could only be performed on either the low rotation side or the high rotation side.

Therefore, the basic objective of the present invention is to provide a supercharging device for a reciprocating engine that can perform proper supercharging over the entire rotation range of the engine without causing blowback from the supercharging port to the intake port. The purpose is

For this reason, in the supercharging device for a reciprocating engine according to the present invention, the on-off valve that opens at the end of the intake stroke in synchronization with the output shaft in the supercharging passage including the supercharging port opens and closes the intake port with a delay of a set value. While providing a timing valve to close,
A timing control device is provided that advances the opening timing of the timing valve when the engine is running at high speeds compared to when the engine is running at low speeds, reducing the valve opening time when the engine is running at high speeds and where the intake inertia of the intake port is large. The feature is that compensation is provided by speeding up the process.

The present invention will be specifically described below with reference to the illustrated embodiments.

In FIG. 1, E is the piston 2 in the cylinder 1.
This is a reciprocating engine that rotates a crankshaft 4 via a connecting rod 3 by the reciprocating motion of the engine. , a supercharging port 7 and an exhaust port 8 are respectively opened.

The main intake port 6 and the exhaust port 8 are connected to a well-known timing cam (not shown) in synchronization with the rotation of the output shaft of the engine E.

) are opened and closed at predetermined timings by the main intake valve 9 and the exhaust valve 10, the opening and closing timings of which are controlled by the main intake valve 9 and the exhaust valve 10, respectively.

The main intake port 6 is opened by the main intake valve 9 during the intake stroke of the engine E, and allows the air-fuel mixture supplied by the carburetor 11 to be naturally sucked into the combustion chamber 5 via the main intake passage 12.

Further, when the exhaust port 8 is opened by the exhaust valve 10, exhaust gas generated by combustion is discharged to the outside through the exhaust passage 13.

On the other hand, the supercharging port 7 is driven by the engine E, and a supercharging passage 16 has an air pump 15 interposed therebetween, which takes in atmospheric air through an air cleaner 14, pressurizes it, and discharges it.
The supercharging valve 17 is opened and closed by the supercharging valve 17.

The operation of this supercharging valve 17 is controlled by a timing cam 18, which will be explained in detail below, and when the timing cam 18 operates to open the supercharging valve 17 and the supercharging port 7 is opened, the supercharging valve 17 is pressurized by the air pump 15. The air is supplied into the combustion chamber 5 via the supercharging passage 16.

In FIG. 1, 19 is a return passage that bypasses the air pump 15 and communicates its discharge side with the suction side, 20 is a check ball type relief valve interposed in the middle of the return passage 19, and 21 is a supercharging passage. 16 air pumps 1
The control valve 7'21 is a control valve provided downstream of the throttle valve lla of the carburetor 11.
Similarly, the passage area of the supercharging passage 16 is adjusted according to the load of the engine E to adjust the supercharging amount.

As shown in FIGS. 2 and 3, the timing cam 18 that controls the operation of the supercharging valve 17 has a low-speed cam surface 18a and a high-speed cam surface 18b continuous in the axial direction on its outer periphery. It is something.

This cam surface 18a or 18b is attached to the valve shaft end 17a of the supercharging valve 17 by the spring force of a spring 23 received in a spring receiver 22 attached to the valve shaft end of the supercharging valve 17.
As shown in FIG. 2, the timing cam 18 is biased so that the
Fixed.

The rotating shaft 24 is fitted at one end to a spline shaft 27 provided on the free end side of the rotating shaft 26 of the pulley 25 so as to be slidable in the axial direction, and at the other end to the inner wall of the cam storage case 28. The rotary bearing 29 is slidably supported in the axial direction.

The rotating shaft 26 of the pulley 25 is supported by a bearing 30 supported on one wall of the cam storage case 28.
A timing belt 31 wound around the crankshaft 4 allows the pulley 25 to rotate (1/2
) is driven in synchronization with the crankshaft 4 to rotate.

The rotation shaft 24 of the timing cam 18 is normally rotated by a spring 33 compressed in a shaft hole 32 provided in the cam storage case 28 at the other end.
The valve shaft end 17 of the supercharging valve 17 is attached to the low speed cam surface 18a of 8.
The axial position of the cam surface 18b is maintained such that the cam surface 18a abuts against the cam surface 18a, and the centrifugal governor 34 mounted on the spline shaft 27 performs switching to the high speed cam surface 18b.

As is well known, when the centrifugal force of rotation becomes greater than a set value, the centrifugal governor 34 stands up in a simple direction in a plane that includes the axis, and at that time, the pusher J'f35 provided at the tip
a, a centrifugal weight 35 that pushes the end surface 24a of the rotation shaft 24 of the timing cam 18 on the spline shaft 27 side in the direction indicated by arrow P in the figure is attached to the collar 3 fixed to the spline shaft 27.
When the centrifugal weight 35 stands up, it pushes the rotating shaft 24 a certain distance in the direction P against the spring force of the spring 33, and the valve shaft of the supercharging valve 17 The end 17a is switched so as to come into contact with the high-speed cam surface 18b.

Low speed cam surface 18a of timing cam 18=! =The high-speed cam surface 18b has two peaks 18A and 18B, respectively, as shown in FIG. 18A, it has an earlier rising phase with respect to the rotational direction of the timing cam 18.

As shown in the figure, the peaks 18A and 18B of the low-speed cam surface 18a and the high-speed cam surface 18b both have the same falling phase.

4a and 4b show the supercharging port 7 formed by the low-speed cam surface 18a and the high-speed cam surface 18b of the timing cam 18.
In other words, the opening/closing timing of the supercharging valve 17 is shown based on the rotation angle of the crankshaft 4.

As shown in Figure 4a, when the engine E rotates at low speed,
The main intake port 6 is fully opened at intake top dead centers T, D, C, and just before it is fully closed after intake bottom dead center B, D, C, the supercharging port 7 is opened, and the main intake port 6 is fully closed. It is closed at a certain timing, and during that time, pressurized air supplied by the air pump 15 is supplied from the supercharging port 7 into the combustion chamber 5.

On the other hand, when the engine E rotates at high speed, the timing cam 18 is switched from the low speed cam surface 18a to the high speed cam surface 18b by the function of the centrifugal governor 34, as described above.
The opening and closing of the supercharging valve 17 is controlled by a high-speed cam surface 18b.

As described above, the peak portion 18B of the high-speed cam surface 18b has a faster rising phase than the peak portion 18A of the low-speed cam surface 18a.
The valve opening timing is advanced, and the supercharging port 7 becomes the main intake port 6.
starts to open just before it starts to close.

In this case, the intake inertia of the main intake port 6 is relatively larger during high speed rotation than during low speed rotation, so even if the overlap between the main intake port 6 and the supercharging port is increased, the supercharging port 7 There is no blowback from the main intake port 6 to the main intake port 6, and during this overlap period, intake air is supplied from both the main intake port 6 and the supercharging port γ, and after the main intake port 6 closes, the supercharging port 7 is supplied for a certain period of time. Supercharging air is supplied from

Note that the closing timing of the supercharging valve 17 and therefore the supercharging port 7 is set to be the same as when the engine is rotating at a low speed, as is clear from a comparison with FIG. 4a.

The timing of closing the supercharging port 7 is determined by the capacity of the air pump 15 used as a supercharger, and
It is set within a range that does not cause blowback to the supercharging port 7.

In the above embodiment, the cam surface '18a or 18b of the timing cam 18 is controlled by the ζ'' centrifugal governor 34.
However, the engine rotation speed is detected by a rotation speed detection switch (not shown), and when the engine rotation speed reaches the set rotation speed, an electrical signal from the rotation speed detection switch is used to switch the engine rotation speed. , actuating suitable electromagnetic means;
The low speed cam surface 18a may be switched to the high speed cam surface 18b.

As is clear from the above explanation, in the supercharging device for a reciprocating T-engine according to the present invention, the timing control device controls the opening and closing timing of the timing valve that opens and closes the supercharging port, so that the engine can operate at high speeds. During engine rotation, supercharging ports 1 to 1 are opened earlier than when the engine is rotating at low speeds, so that effective and appropriate supercharging can be performed over the entire operating range of the engine, especially when the engine is rotating at high speeds. Even in this case, since the necessary and sufficient supercharging can be performed, the output performance of the engine can be improved, and the original purpose of the supercharging device can be effectively achieved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of the present invention, FIG. 2 is a front view of main parts showing an embodiment of a timing control device according to the present invention, and FIG. The cross-sectional view along the A' line, Figures 4a and 4b, are diagrams showing the timing of opening and closing of the main intake port and supercharging port during low-speed rotation and high-speed rotation of the engine, respectively. 1... ... Cylinder, 2... Screw 1 Hen,
4...Crankshaft, 5...Combustion chamber, 6
...Main intake port, 7...Supercharging port, 15...Air pump, 16...Supercharging passage, 17...Evening f ng valve, 18...
...Timing cam, 34...Centrifugal governor.

Claims (1)

[Scope of Claims] 1. A reciprocating engine in which a supercharging port is formed in addition to a main intake port in a combustion chamber formed between a cylinder and a piston that reciprocates within the cylinder. A timing valve is provided in the supercharging passage including the supply port, which opens at the end of the intake stroke in synchronization with the engine's output shaft and closes a set value later than the on-off valve that opens and closes the main intake port. A supercharging device for a reciprocating engine, comprising a timing control device that opens a timing valve earlier than when the engine speed is low.