JPS6148622B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an internal combustion engine with a supercharger, in particular, a carburetor equipped with a main throttle valve from the upstream side of the intake passage of the engine, and a supercharger that is linked to the output shaft of the engine. The present invention relates to a control device for stabilizing idling operation of a connected internal combustion engine without reducing charging efficiency during load operation.

The above supercharged internal combustion engine has the disadvantage that idling is difficult to stabilize. This is due to the inherent characteristic of a supercharger that the volumetric efficiency of the supercharger decreases at low rotation speeds and increases at high rotation speeds. In other words, when the idling speed of the engine is set to a certain value by setting the idle opening degree of the main throttle valve, if the engine speed falls below the set speed due to disturbances such as combustion fluctuations, the above-mentioned speed of the supercharger Due to the characteristics, the air-fuel mixture filling efficiency of the engine decreases, resulting in a decrease in engine output, and the engine stalls without being able to increase its rotational speed. Conversely, if the engine speed rises above the set speed, the charging efficiency of the engine increases due to the above-mentioned characteristics of the supercharger, resulting in an increase in output, so the engine speed continues to rise. When the engine output and the frictional resistance force of each moving part, which increases as the engine speed increases, are balanced, the engine speed will stop increasing, and in either case, the idle opening setting of the main throttle valve will not change. The idling speed of the engine cannot be returned to the set speed.

Therefore, in order to stabilize the idling operation of the engine, it is necessary to increase the air-fuel mixture filling efficiency of the engine when the engine speed decreases and to decrease it when the engine speed increases.

For this purpose, the applicant has already proposed a control device in which an auxiliary throttle valve is provided in the intake path upstream of the supercharger and is closed only when the main throttle valve is closed to the idle opening. are doing. however,
The control device has an expensive idle opening position sensing valve interlocked with the main throttle valve interposed in the boost pipe that connects the negative pressure actuator that operates the auxiliary throttle valve and the intake passage that is the source of negative pressure. There are many components and the structure is complicated, making it difficult to provide the product at a low price.

In view of the above, the present invention stabilizes idling operation without reducing the air-fuel mixture filling efficiency during engine load operation without using an expensive sensing valve or an interlocking mechanism between the sensing valve and the main throttle valve. The purpose of this invention is to provide a simple and effective control device that can perform the following functions.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 denotes an internal combustion engine, which includes a combustion chamber 2 and intake and exhaust passages 3 and 4 opening therein, as in the conventional case.
and the combustion chamber 2.
It consists of a cylinder 7 that accommodates a piston 6 whose top surface is exposed to the cylinder 7, and a crankcase 9 that supports a crankshaft 8 that is interlocked with the piston 6.
The suction and exhaust passages 3 and 4 are opened and closed by suction and exhaust valves 10 and 11 which are synchronously operated by a valve mechanism (not shown) that is interlocked with the crankshaft 8.

An air cleaner 12, a carburetor 13, a supercharger 14, and a reservoir 15 are sequentially connected to the intake passage 3 from the upstream side, and the intake passage of the carburetor 13 is connected to an accelerator operating member (not shown) as usual. ) is provided with a butterfly-type main throttle valve 16 that is interlocked with the main throttle valve 16.

In the illustrated example, a known screw pump consisting of a male screw rotor 17 and a female screw rotor 18 that mesh with each other is used as the supercharger 14, and the driven pulley 19 of the male screw rotor 17 is connected to the crankshaft. Drive pulley 20 fixed to 8
The screw pump, that is, the supercharger 14 is driven by the crankshaft 8 at a constant rotation ratio.

A butterfly-type auxiliary throttle valve 22 is provided in the intake passage 3 downstream of the supercharger 14, preferably downstream of the reservoir 15. It has two operating positions. The auxiliary throttle valve 22 is equipped with a valve opening spring 23 that always urges it to the fully open position, and a negative pressure actuator 24 that can operate the auxiliary throttle valve 22 to the idle opening position against the force of the valve opening spring 23. Link.

The negative pressure actuator 24 is composed of a housing 25 fixed to the outer wall of the intake passage 3 and a diaphragm 28 that partitions the inside of the housing into an atmospheric chamber 26 and a negative pressure chamber 27, and is connected to the center of the diaphragm 28. The operating rod 29 is connected to an operating lever 30 fixed to the outer end of the valve shaft of the auxiliary throttle valve 22. In the illustrated example, the valve opening spring 23 is compressed into the negative pressure chamber 27 so as to operate the auxiliary throttle valve 22 via the diaphragm 28.

The negative pressure chamber 27 of the negative pressure actuator 24 is communicated via a boost pipe 32 with a negative pressure detection hole 31 that opens into the intake path 3 of the carburetor 13 . The opening position of the negative pressure detection hole 31 to the intake passage 3 is such that when the main throttle valve 16 is in the idle opening position, it faces the main throttle valve 16 with a bottleneck 3a therebetween, and the main throttle valve 16 It is especially set at a position where it moves upstream when opened.

In the figure, 33 is a lubricating oil pump, and 34 is an oil passage connected to the lubricating oil pump and transporting lubricating oil to each part of the engine 1 and the supercharger 14.

Next, to explain the operation of this embodiment, when the engine 1 is operating, the flow rate of the air-fuel mixture generated in the carburetor 13 is controlled by the main throttle valve 16, and the flow rate is controlled by the main throttle valve 16.
4 is pressurized and stored in a reservoir 15, and then supplied into the cylinder 7 during the intake stroke of the engine 1 when the intake valve 10 is opened.

Therefore, if the main throttle valve 16 is now closed to the idle opening position shown by the solid line, the peripheral surface of the valve will be exposed to the negative pressure detection hole 3.
1 and forms a bottleneck 3a between them,
As air passes there at high speed, a high negative pressure is detected in the negative pressure detection hole 31, which is transmitted to the negative pressure chamber 27 of the negative pressure actuator 24 via the boost pipe 32, and is transmitted to the diaphragm 28 in a downward direction. In order to apply suction force, the actuating rod 29 is lowered and the auxiliary throttle valve 22 is held in the idle position shown by the solid line via the actuating lever 30, thereby creating a certain throttling effect on the intake passage 3 downstream from the supercharger 14. give. As a result, the air-fuel mixture filling efficiency of the engine 1 exhibits the expected characteristic of decreasing as the engine speed increases, almost regardless of the operation of the supercharger 14. Therefore, if the idling speed of the engine 1 deviates from a certain set value due to disturbance, the air-fuel mixture filling efficiency of the engine 1, and therefore the engine output, will immediately change to correct the deviation. When the idling speed falls below the set value, the air-fuel mixture filling efficiency decreases, and conversely, when it rises above the set value, the efficiency increases, so the idling speed returns to the set value and becomes stable.

Next, when the engine 1 is operated under load, if the main throttle valve 16 is opened, the negative pressure detection hole 31 immediately moves to the upstream side of the main throttle valve 16, so the detected pressure of the negative pressure detection hole 31 becomes approximately atmospheric pressure. , as soon as the previous negative pressure in the negative pressure chamber 27 is replaced with the above pressure, the valve opening spring 23
However, due to the elastic force, the diaphragm 28 and the operating rod 29
etc. to fully open the auxiliary throttle valve 22. Therefore, the throttling effect of the auxiliary throttle valve 22 on the intake passage 3 is removed, and the air-fuel mixture measured by the main throttle valve 16 can be reliably supercharged into the cylinder 7 from the supercharger 14, resulting in a good performance. Load operating status can be obtained.

FIG. 5 shows the negative pressure detection hole 31 and the first,
It shows the detected negative pressure characteristics of the detection holes 31', 31'' of the second comparative example with respect to the main throttle valve opening.The detection holes 31', 31'' of the first and second comparative examples are 4, that is, when the main throttle valve 16 is in the idle opening position, the detection hole 31' is downstream of and close to the main throttle valve 16, and the detection hole 31'' is located close to the main throttle valve 16. It is provided on the upstream side of the throttle valve 16 and close thereto.

Now, as is clear from FIG. 5, the negative pressure detected by the negative pressure detection hole 31' of the first comparative example shows a peak value at a position where the main throttle valve 16 slightly exceeds the idle opening. It is not suitable for sensing the idle opening position of the throttle valve 16, and the detection hole 31' of the second comparative example is
The detected negative pressure reaches its peak at the idle opening position of the main throttle valve 16, but its value is so low that it is difficult to use it as the operating negative pressure of the negative pressure actuator 24. In contrast, the negative pressure detected by the negative pressure detection hole 31 of the present invention shows a high peak value at the idle opening position of the main throttle valve 16, so the negative pressure actuator 24 is reliably operated only at that point. Main throttle valve 16
It can be seen that the auxiliary throttle valve 22 is quickly fully opened by the force of the valve opening spring 23 when the valve is opened.

As described above, according to the present invention, by simply specifying the opening position of the negative pressure detection hole to the intake passage, the negative pressure detection hole is directly communicated with the negative pressure chamber of the negative pressure actuator, thereby providing an auxiliary throttle. The valve can be precisely controlled according to the required characteristics, and therefore the idle opening position detection valve of the main throttle valve and its attached devices, such as the previously proposed control device, are not required, and the control is reliable and has fewer failures. This has the effect that the device can be provided at low cost.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal overall side view showing one embodiment of the device of the present invention, Fig. 2 is an enlarged sectional view of the vicinity of the negative pressure detection hole, and Figs. 3 and 4 are negative pressure of the first and second comparative examples. FIG. 5 is an enlarged sectional view showing the position of the detection hole, and is a negative pressure characteristic line diagram detected by each negative pressure detection hole of the present invention and the first and second comparative examples. 1... Internal combustion engine, 3... Intake path, 3a... bottleneck, 8... Crankshaft as output shaft, 13...
Carburetor, 14...Supercharger, 16...Main throttle valve, 22
... Auxiliary throttle valve, 23 ... Valve opening spring, 24 ... Negative pressure actuator, 27 ... Negative pressure chamber, 31 ... Negative pressure detection hole.

Claims (1)

[Claims] 1. A carburetor equipped with a main throttle valve and a supercharger linked to the output shaft of the internal combustion engine are sequentially connected to the intake passage of an internal combustion engine from the upstream side, and an auxiliary throttle valve is connected to the intake passage downstream of the supercharger. In the internal combustion engine with a supercharger installed,
Connecting the auxiliary throttle valve to a valve opening spring that urges it to a fully open position and a negative pressure actuator that can operate the auxiliary throttle valve to an idle opening position against the force of the valve opening spring,
The negative pressure chamber of the negative pressure actuator is connected to the intake passage so that it faces the main throttle valve with a bottleneck in between when the main throttle valve is in the idle opening position, and moves to the upstream side of the main throttle valve when the main throttle valve is opened. A control device for an internal combustion engine with a supercharger, which communicates with a negative pressure detection hole opened in the