JPS5815607B2 - 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. This 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, since all of the intake air taken into the engine is adiabatically compressed and heated to high temperature by the supercharger, there is a problem that the density of the intake air becomes circular and the charging efficiency is not sufficiently improved. In order to avoid this problem, the supercharger must be made larger.

Therefore, in addition to the main intake port of a conventional engine, which sucks in the air-fuel mixture using the intake negative pressure, we installed a supercharging port that supplies air or air-fuel mixture pressurized by the turbocharger, allowing natural intake due to the negative pressure and the turbocharger. A system has been proposed in which intake air is carried out by supercharging and charging efficiency is improved using a relatively small capacity supercharger.

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, Therefore, the intake ability of the air-fuel mixture is inhibited, and the supply ratio of high-temperature pressurized air increases, and blowback from the supercharging port to the intake port occurs, making it impossible to obtain a sufficient supercharging effect.

In this regard, the applicant has proposed that the timing valve, which opens and closes the supercharging port at a predetermined timing, is opened and closed at the end of the intake stroke, when the intake from the intake port is almost completed, by opening the supercharging passage and supplying pressurized air or air-fuel mixture. We have already proposed an engine supercharging device configured to supply

In a device equipped with such a timing valve, since supercharging is performed only at the end of the intake stroke, blowback from the supercharging port to the intake port can be practically eliminated, and even a small-capacity supercharger can be used reliably. 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 is difficult to achieve. This is no longer done, and there is a problem in that the original purpose of improving engine output cannot be achieved.

This lack of supercharging when the engine is running at high speeds can be solved by setting the effective area of the supercharging port large and reducing the passage resistance of the supercharging port. Since blowback to the supercharging port occurs, it is necessary to advance the closing timing of the supercharging port, which shortens the supercharging period, and simply increasing the area of the supercharging port may not be an effective solution. do not have.

Therefore, the present invention can perform effective supercharging even when the engine is rotating at high speed, and conversely, when the engine is rotating at low speed, it can perform proper supercharging without causing blowback to the supercharging port. The basic objective is to provide a supercharging device for a reciprocating engine that can improve power performance over the entire rotational range of the engine.

More specifically, the present invention reduces the effective minimum area of the supercharging port depending on the engine speed, and reduces it at low speeds.
A control device is installed to increase the amount of fuel at high speeds, and at low speeds the amount of supercharging is optimized to avoid blowback to the supercharging port. It is an object of the present invention to provide a supercharging device for a reciprocating engine that can perform effective supercharging by compensating for an increase in the effective minimum area.

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 drives a crankshaft 4 through a connecting rod 3 through one rotation by the reciprocating motion of the engine. A supercharging port 7 and exhaust ports 1-8 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 is provided with an air pump 15 as a supercharger that sucks atmospheric air through an air cleaner 14, pressurizes it, and discharges it.
The supercharging valve 1γ opens and closes the supercharging valve 1γ.

This supercharging valve 17 (1) sets the effective minimum area of the supercharging port 1-7 according to the stroke amount when the valve is opened, and the timing cam 18, which will be explained in detail below.
When the timing cam 18 operates to open the supercharging valve 17 and the supercharging ports 1-7 are opened, air pressurized by the air pump 15 is introduced into the combustion chamber 5 through the supercharging passage 16. In addition, in Figure 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 downstream of the air pump 15 in the supercharging passage 16. Like the throttle valve lla of the carburetor 11, the control valve j21 adjusts the passage area of the supercharging passage 16 according to the load of the engine E to adjust the supercharging amount.

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, as shown in FIGS. 2 and 31-1. It is something that

The cam surface 1.8, a or 18b is provided with a valve shaft end of the supercharging valve 1γ 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. 17a is biased so as to be in constant contact.

As shown in FIG. 2, the timing cam 18 is connected to a rotating shaft 24
Fixed.

This rotation! 111124 is a spline shaft 27 provided at one end on the free end side of the rotating shaft 26 of the pulley 25.
The cam storage case 28 is slidably fitted in the axial direction, while the other end is slidably supported in the axial direction by a rotary bearing 29 supported on the inner wall of the cam storage case 28.

The rotation shaft 26 of the pulley 25 is supported by a bearing 30 supported on a 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, this centrifugal governor 34 stands up in the radial direction in a plane including the axis when the centrifugal force of rotation becomes greater than a set value. A centrifugal weight 35 that pushes the end surface 24a of the rotating shaft 24 of the cam 18 on the side of the spline shaft 27 in the direction indicated by arrow P in the figure is hinge-supported on an arm 37 supported by a collar 36 fixed to the spline shaft 27, When the centrifugal weight 35 stands up, the rotating shaft 24 is pushed a certain distance in the P direction against the spring force of the spring 33, and the supercharging valve 17
The valve shaft 17a is switched so as to come into contact with the high-speed cam surface 18b.

As shown in FIG. 3, the low-speed cam surface 18a and high-speed cam surface 18b of the timing cam 18 are
8A and 18B (lifting head section), respectively, and a high-speed cam surface 18
The peak portion 18B of b has a height that is similar to that of the low-speed cam surface 18.
Preferably, the rising phase is set higher than the peak 18A of the low-speed cam surface 18a.
The rotation direction of the timing cam 18 is set to be earlier than the rising phase 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,
Immediately before the main intake port 6 is fully opened at intake top dead centers T, D, and C, and fully opened after intake bottom dead centers B, D, and C, the height is lower than the peak 18B of the high-speed cam surface 18b, and The supercharging valve 17 is opened by the peak 18A of the low-speed cam surface 18a whose rising phase is set to be late, and the supercharging port 7 is opened with a smaller opening area to allow the pressurized air supplied by the air pump 15 to be opened. It is supplied into the combustion chamber 5.

This supercharging port 7 is closed by a supercharging valve 17 controlled by a low-speed cam surface 18a at a certain timing after the main intake port 6 is fully closed, and burns pressurized air until it is closed. Supercharge chamber 5.

On the other hand, when the engine E rotates at high speed, the centrifugal weight 35 of the centrifugal governor 34 stands up due to the increase in centrifugal force, displacing the rotating shaft 24 of the timing cam 18 in the axial direction, as described above, and Change the cam surface to low speed cam surface 18
Switch from a to the high speed cam surface 18b.

As described above, the peak portion 18B of the high-speed cam surface 18b is higher in height and has an earlier rising phase than the peak portion 18A of the low-speed cam surface 18a. The opening timing of the valve 17 is advanced, and at the same time, the valve opening stroke becomes larger.The supercharging port 7, which is opened and closed by the supercharging valve 17, is opened just before the main intake port 6 is closed, and the supercharging port 7 is opened just before the main intake port 6 is closed. A sufficient amount of pressurized air is supplied to the combustion chamber 5.

In this case, during high-speed rotation, the opening time of supercharging port 7 is extremely shortened compared to when rotating at low speed, so there is no blowback to supercharging port 7, and the intake inertia of main intake port 6 also increases, so there is no overflow. Blowing back from the supply port 7 to the main intake port 6 also does not occur.

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 for the supercharger.
The setting is made within a range in which blowback to the supercharging port 7 does not occur.

In the above embodiment, the cam surface 18a or 18b of the timing cam 18 is switched by the centrifugal governor 34, but the rotation speed of the engine is detected by a rotation speed detection switch (not shown) by excitation. When the engine speed reaches a set speed or higher, an electric signal from the speed detection switch activates an appropriate electromagnetic means to switch from the low-speed cam surface 18a to the high-speed cam surface 18b. You can also do this.

Further, in the above embodiment, the peak portion 18 of the high-speed cam surface 18b
Not only the height of B is set high, but the rising phase is also advanced, but the height of the peak 18B is set sufficiently high, and the minimum effective area of the supercharging port γ when the valve is opened is sufficiently large. If this is done, it is not necessarily necessary to advance the valve opening timing.

As is clear from the above explanation, in the supercharging device for a reciprocating engine according to the present invention, the effective minimum area of the supercharging port that is opened and closed by the on-off valve is small when the engine is running at substitute speed, and large when the engine is running at high speed. A control device has been installed to allow proper supercharging without blowback to the supercharging port when the engine is running at low speeds, and also to reduce the supercharging time when the engine is running at high speeds by reducing the effective minimum area of the supercharging port. By compensating by the expansion of
Effective supercharging becomes possible, and therefore, appropriate and effective supercharging can be performed over the entire operating range of the engine, and the original purpose of improving engine output performance through supercharging can be effectively achieved. I can do it.

[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 essential parts showing an embodiment of a timing control device according to the present invention, and FIG. 3 is an 8-A diagram in FIG. The linear cross-sectional view, FIG. 4 a+b, is a diagram showing the timing of opening and closing of the main intake port and the supercharging port when the engine is rotating at low speed and when the engine is rotating at high speed, respectively. 1...Cylinder, 2...Piston, 4
... Crankshaft, 5 ... Combustion chamber, 6.
...Main intake port, 7...Supercharging port,
15...Air pump, 16...Supercharging passage, 17...Timing valve, 18...
...Timing cam, 34...Centrifugal governor.

Claims (1)

[Scope of Claims] 1. In a reciprocating engine in which a main intake port and a supercharging port are formed in a combustion chamber, and on-off valves are provided for each of the main intake port and the supercharging port, an on-off valve that opens and closes the supercharging port. is opened at the end of the intake stroke,
The main intake port is configured to close with a set value delay from the opening/closing valve that opens and closes the main intake port, and a control device is provided that reduces the effective minimum area of the supercharging port when the engine speed is low and increases it when the engine speed is high. A supercharging device for reciprocating engines that features: