JPH0116964B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an engine intake/exhaust valve control device for controlling the opening/closing timing of an intake valve and an exhaust valve of a four-stroke engine having an intake valve and an exhaust valve.

Conventionally, a four-stroke engine has been constructed as shown in FIG. 1, and numeral 1 in FIG. 1 is an intake valve. This intake valve 1 is for sucking a mixture of fuel and air into the cylinder 9. This suction valve 1 is operated by a cam 3, which rotates in conjunction with a crankshaft 6.
This causes the intake valve 1 to operate.

Further, the exhaust valve 2 is for discharging gas after combustion from the cylinder 9 to the outside, and the exhaust valve 2 is operated by a cam 4. Like the cam 3, the cam 4 operates the exhaust valve 2 by rotating in conjunction with the crankshaft 6.

The crankshaft 6 is connected to the piston 5,
The piston 5 reciprocates within the cylinder 9. An air-fuel mixture is introduced into the cylinder 9 through an intake pipe 7, and exhaust gas within the cylinder 9 is introduced to the outside through an exhaust pipe 8.

In the conventional four-stroke engine configured as described above, the intake valve 1 and the exhaust valve 2 open and close in conjunction with the reciprocating movement of the piston 5, and the intake, compression, and
The explosion-exhaust process is repeated, but the crankshaft 6 rotates at 1/2 the rotation speed, and the intake valve 1 and exhaust valve 2
The shape of cams 3 and 4 that actuate (i.e.
The opening/closing timings of the intake valve 1 and the exhaust valve 2) are determined so as not to significantly impede the combustion of the engine under all operating conditions.

That is, as shown in FIG. 2, the intake valve 1 opens before the top dead center (θ _SB ) where the intake stroke begins, and closes at a position past the bottom dead center (θ _SA ) where the intake stroke ends.

On the other hand, the exhaust valve 2 opens before the bottom dead center (θ _EB ) where the exhaust process begins, and closes at a position past the top dead center (θ _EA ) where the exhaust process ends.

The reason why the intake valve 1 is opened earlier and closed later is to compensate for the decrease in intake efficiency due to the action of air inertia when the engine is operating at high speeds. Furthermore, the opening and closing timing of the exhaust valve 2 is determined in consideration of pumping loss and blowdown loss.

It is the closing timing of the intake valve 1 that greatly controls the suction efficiency, and it is better to delay the valve closing timing θ _SA on the high rotation side, but if the valve closing timing θ _SA is late on the low rotation side, the compression process will be delayed. A problem occurs in which the air-fuel mixture in the air flows back into the intake pipe 7.

Therefore, the valve closing timing θ _SA must be set as a compromise to allow the engine to operate without any trouble from low to high speeds, so as shown by the solid line in Figure 3, On the other hand, the intake efficiency inevitably decreases, and the output torque of the engine decreases.

Further, regarding the opening and closing timing of the exhaust valve 2, the opening and closing angle is set so that the sum of pumping loss and blowdown loss is small in a frequently used region of the engine operating state. Therefore, as shown in FIG. 4, there is a drawback in that as the engine speed increases, torque loss, mainly due to pumping loss, increases.

This invention was made to eliminate the above-mentioned conventional drawbacks, and the cam that operates the intake valve and exhaust valve is driven by a stepping motor without being mechanically connected to the crankshaft. By controlling the stepping pulse given to the ping motor by various parameters such as engine speed,
It is an object of the present invention to provide an intake and exhaust valve control device for an engine that can arbitrarily vary the rotation angle of a cam relative to the rotation angle of a crankshaft so that the opening and closing timing of the intake and exhaust valves can always be set to an optimum value.

Embodiments of the engine intake and exhaust valve control device of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram showing the configuration of one embodiment.
In FIG. 5, 20 is a rotating body, and this rotating body 20 is connected to the crankshaft 6. As shown in FIG. This crankshaft 6 is the same as the crankshaft shown in FIG.

A crank angle sensor 21 is disposed facing the outer peripheral surface of the rotating body 20. Crank angle sensor 21
outputs a pulse signal at a predetermined degree of rotation of the rotating body 20 (for example, in units of 1 degree).

As shown in FIG. 7b, the output signal of the crank angle sensor 21 outputs a pulse signal at every predetermined rotation angle of the crankshaft 6, and also outputs a signal for identifying the positions of top dead center TDC and bottom dead center BDC. Output.

For example, when the rotating body 20 is provided with a notch and the crank angle sensor 21 is of a magnetic detection type or an optical type, this identification signal can be transmitted to the rotating body 20 as shown in FIG.
Teeth 20a in minute angular units provided in the circumferential direction of
In addition, this can be achieved by providing wide teeth 20b every 180 degrees, or by using a crank angle sensor dedicated to detecting top dead center and bottom dead center.

Although the case where the rotating body 20 is directly connected to the crankshaft 6 has been described here, it goes without saying that the rotating body 20 may be connected to a shaft other than the crankshaft 6, for example, a shaft for driving a power distribution device. .

Here, the explanation returns to FIG. 5 again. A pulse signal generated by the crank angle sensor 21 is sent to a pulse drive control circuit 22 and a rotation speed detection circuit 23. The pulse drive control circuit 22 generates an output signal based on data stored in the memory 24 in synchronization with the pulse signal generated by the crank angle sensor 21, and drives the stepping motors 25 and 26.

Further, the rotation speed detection circuit 23 detects the rotation speed of the engine by measuring the cycle of the pulse signal output from the crank angle sensor 21 or by counting the number of pulses within a predetermined time.

The opening/closing timing of the intake valve 1 and exhaust valve 2 with respect to the engine rotation speed is stored in advance in the memory 24, and the stored contents of this memory 24 are sent to the pulse drive control circuit 22 as described above, and the pulse drive control circuit 22 drives stepping motors 25 and 26 based on the contents stored in the memory 24.

By the stepping motor 25, the shaft 2
7 is adapted to be driven, and the cam 3 is mechanically connected to this shaft 27. cam 3
The cam 3 is similar to the cam 3 shown in FIG. 1, and the cam 3 operates the intake valve 1.

Similarly, a shaft 28 is driven by the stepping motor 26, and the cam 4 is mechanically connected to the shaft 28. The cam 4 is also the same as the cam 4 shown in FIG. The exhaust valve 2 is operated by this cam 4.

Next, the operation of the engine intake/exhaust valve control device of the present invention constructed as described above will be described with reference to FIGS. 7 and 8. First, Figure 7a shows the engine's explosion, exhaust, intake, and compression processes.As shown in Figure 7a, when the engine rotates by repeating the intake-compression-explosion-exhaust process, , as shown in FIG. 7b, the crank angle sensor 21 generates a crank position signal (pulse signal).

This crank position signal is transmitted to the pulse drive control circuit 2.
2 and the rotation speed detection circuit 23. At a certain rotation speed of the engine, the pulse drive control circuit 2
The drive pulse of the stepping motor 25 for the intake valve (Fig. 7e), which is one of the outputs of the memory 24
Since the rotation angle of the stepping motor 25, that is, the rotation angle of the intake valve shaft 27, is generated at a ratio of 1 pulse to 2 pulses of the crank position signal based on the data of FIG. When the opening angle α1 of the intake valve 1 determined by the predetermined shape of the cam 3 is reached, the intake valve 1 opens as shown in FIG. 7c.

When the stepping motor 25 further advances and the rotation angle of the shaft 27 reaches the rotation angle α2 as shown in FIG. 7f, the intake valve 1 closes as shown in FIG. 7c.

FIG. 8 shows the operation when the engine speed is higher than that in FIG. 7, and is synchronized with the crank position according to the opening/closing timing data of the intake valve 1 for the engine speed stored in advance in the memory 24. The driving pulse of the stepping motor 25 is such that the intake valve 1 opens at the position _θSB2 (Fig. 8b) before the top dead center TDC1 shown in Fig. 8b (that is, the rotation angle of the shaft 27 is α1 as shown in Figure 8f
) is thinned out and output.

That is, in FIG. 7, the stepping motor 25 is driven with a pulse number that is half the number of pulses of the crank position signal, whereas in FIG. 8, after the crankshaft passes the bottom dead center BDC1, The number of pulses equal to or more than half of the number of pulses of the position signal is applied to the stepping motor 25 to accelerate the rotation angle of the shaft 27 with respect to the crankshaft 6. Therefore, the opening timing (position) θ _SB2 of intake valve 1 is the seventh
The opening/closing timing _θSB1 shown in the figure is greater than that.

On the other hand, regarding the closing of the intake valve 1, the rate of thinning of the pulse signal synchronized with the crank position signal is increased according to the data stored in advance in the memory 24, and the timing when the shaft 27 reaches the rotation angle α2 is delayed. The valve closing timing θ _SA2 is controlled to be later than the valve closing timing θ _SA1 in FIG.

The driving pulses of the stepping motor 26 for the exhaust valve (not shown in FIGS. 7 and 8) are also controlled in the same manner as those for the intake valve. With this configuration, the rotation angle of the shafts 27, 28 with respect to the crankshaft 6 can be arbitrarily varied by controlling the timing of the drive pulse train applied to the stepping motors 25, 26. 1. Exhaust valve 2
The timing of opening and closing can be freely controlled according to the operating condition of the engine.

In general, the intake efficiency of an engine is determined by the closing timing of intake valve 1 (after bottom dead center) at high engine speeds, as shown in Figure 9.
As shown in FIG. 10, the optimal value of the closing timing of the intake valve 1 relative to the engine speed is stored in the memory 24, and this memory By controlling the stepping motor 25 according to the content, high suction efficiency can be obtained even at high rotation speeds, as shown by the broken line in FIG. 3, and the decrease in engine output torque at high rotation speeds can be prevented. It can be suppressed.

Furthermore, as shown in Fig. 11, the optimum value for the opening timing of the intake valve 1 is determined from the point where the sum of pumping loss and blowdown loss is minimized, and the opening timing can be advanced as the engine speed increases. is desirable. The opening timing of the exhaust valve 2 can also be easily controlled by the same method as in the case of the exhaust valve 2.

In addition, the overlap between the opening timing of intake valve 1 and the closing timing of exhaust valve 2, that is, the overlap, should be larger on the high rotation side from the viewpoint of improving intake efficiency, but on the low rotation side, the overlap between the air-fuel mixture and the exhaust valve 2 is better. The atrium,
In order to suppress unstable combustion due to backflow of exhaust gas into the cylinder, the smaller the value, the better, and there is an optimal value for the engine speed.

By storing these optimal values in the memory 24 in advance, the intake valve 1 and the exhaust valve 2 can be controlled so as to achieve both intake efficiency and combustion stability.

In the case of the intake valve 1, the reference position of the drive pulse train for stepping the stepping motors 25 and 26 is the bottom dead center where the exhaust stroke begins (BDC1 in Figure 8b) or the top dead center where the explosion stroke begins (Figure 8). b TDC2)
In the case of an exhaust valve, the appropriate position is top dead center (TDC2 in FIG. 8) where the explosion process begins or bottom dead center (BDC2 in FIG. 8b) where the compression process begins.

In the above description, the engine speed is calculated from the output signal of the crank angle sensor 21, but it goes without saying that other signals corresponding to the engine speed, such as an ignition signal, may be used.

As described above, according to the engine intake/exhaust valve control device of the present invention, the optimum values of the opening/closing timing of the intake valve and exhaust valve of the engine are stored in advance in the memory, and the shaft is driven according to the stored contents. Since the opening and closing timing of the intake and exhaust valves is controlled by controlling the rotation angle of the stepping motor relative to the crankshaft, the opening and closing timing of the intake and exhaust valves can be adjusted not only linearly but also non-linearly relative to the engine speed. can also be controlled arbitrarily.

Therefore, it is possible to improve the intake efficiency over the entire operating range of the engine speed, and reduce loss during exhaust, resulting in a significant increase in engine output and efficiency, which is a remarkable effect. be.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an engine for explaining the structure of a conventional engine intake and exhaust valve control device of the present invention, FIG. 2 is an operation explanatory diagram of the conventional engine intake and exhaust valve control device, and FIG. FIG. 4 is a characteristic diagram showing the engine rotation speed versus intake efficiency of the conventional engine intake and exhaust valve control device of the present invention and FIG. FIG. 5 is a block diagram showing the overall configuration of one embodiment of the engine intake and exhaust valve control device of the present invention, FIG. 6 is a configuration diagram of a crank angle sensor used in the engine intake and exhaust valve control device of the present invention, and FIG. 7a to 7f and 8a to 8f are waveform diagrams for explaining the operation of the intake and exhaust valve control device for the engine of this invention, respectively, and FIG. FIG. 10 is a characteristic diagram showing the intake valve closing timing versus intake efficiency ratio in the exhaust valve control device; FIG. The figure is a characteristic diagram showing the optimum value of the engine rotation speed versus the exhaust valve opening timing in the intake and exhaust valve control device of the same engine. 1... Intake valve, 2... Exhaust valve, 3, 4... Cam, 6... Crankshaft, 20... Rotating body, 21...
... Crank angle sensor, 22 ... Pulse drive control circuit, 23 ... Rotation speed detection circuit, 24 ... Memory,
25, 26...Stepping motor, 27, 28
...shaft. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An intake valve that takes air into the engine, a first shaft that operates the intake valve, an exhaust valve that discharges exhaust gas from the engine after combustion, and a second shaft that operates the exhaust valve, the engine. a crank angle sensor that generates a pulsed crank position signal every predetermined rotation angle of the crankshaft;
at least one stepping motor driving the shaft and/or the second shaft;
A memory that stores rotation angle data of the stepping motor relative to the crankshaft that is predetermined for the operating state of the engine, and the rotation that is stored in the memory in synchronization with a crank position signal from the crank angle sensor. An engine intake/exhaust valve control device comprising a pulse drive control circuit that outputs step pulses in accordance with angle data to drive the stepping motor. 2 The number of driving pulses of the stepping motor in one cycle of the engine is constant regardless of the engine speed, and this driving pulse is thinned out by a predetermined number of pulses generated by the crank angle sensor according to the contents of the memory. 2. The engine intake and exhaust valve control device according to claim 1, wherein the engine intake and exhaust valve control device is a number. 3. A patent claim characterized in that the reference position of the drive pulse train of the stepping motor that drives the first shaft is the bottom dead center, which is the starting point of the engine's exhaust stroke, or the top dead center, which is the starting point of the explosion stroke. The intake and exhaust valve control device for an engine according to item 1. 4. A patent characterized in that the reference position of the drive pulse train of the stepping motor that drives the second shaft is the top dead center, which is the starting point of the engine's explosion process, or the bottom dead center, which is the starting point of the compression process. An intake and exhaust valve control device for an engine according to claim 1.