JPH0759892B2 - Engine exhaust control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust control device that opens and closes an exhaust control valve provided in an exhaust pipe of a four-cycle engine according to an engine operating state.

(Background of the Invention) In a 4-cycle engine, a 2-cycle engine, etc., it is known that exhaust gas is intermittently guided to an exhaust pipe by opening and closing an exhaust valve, and an inertial effect and a pulsating effect of the exhaust gas are generated in the exhaust pipe. . These effects (called dynamic effects) change depending on the engine speed. Therefore, if the dynamic effect is maximized to increase the volumetric efficiency at a certain rotation speed, the dynamic effect is adversely affected at other rotation speeds, and the volumetric efficiency is significantly reduced. Therefore, if the specifications of the exhaust system (exhaust pipe length, exhaust pipe diameter, etc.) are set so that this dynamic effect is optimal in the high speed region, a marked decrease in torque in the medium speed region (torque valley) ) Occurred.

Therefore, an exhaust control valve that changes the exhaust flow passage area is installed near the opening end of the exhaust pipe to the expansion chamber, and the flow passage area is reduced in the rotational speed range where the volume efficiency decreases, canceling the influence of the dynamic effect and outputting. It has been proposed to improve the characteristics (Japanese Patent Application No. 60-
No. 263752).

Further, in a multi-cylinder engine, if the downstream side of each exhaust pipe is joined in the expansion chamber, the volume efficiency and the torque may be reduced due to exhaust interference between the cylinders. Therefore, it has been proposed to provide an exhaust control valve for each exhaust pipe and close the control valve in the rotational speed range where adverse effects due to exhaust interference occur to reduce the exhaust flow passage area (Japanese Patent Application No. 60-263753).
issue).

It has also been proposed to improve combustion by controlling the back pressure of the exhaust pipe.

In this way, when improving the output characteristics etc. by the exhaust control valve, it is possible to control the opening degree by the engine speed, but in reality, the intake pipe negative pressure is large or small, that is, the engine load or intake air temperature. However, there is a problem that it is very difficult to determine the optimum opening degree and the apparatus becomes complicated because it is affected by many conditions such as air-fuel mixture concentration. In addition, there is also a problem that it cannot respond to changes over time in engine characteristics and environmental changes.

(Object of the invention) The present invention has been made in view of the above circumstances, and always obtains the optimum engine output by always accurately obtaining the optimum opening degree of the exhaust control valve with respect to the change of the operating state of the engine. It is also an object of the present invention to provide an exhaust control device for an engine that does not have the possibility of being affected by the secular change of the engine or environmental changes.

(Structure of the Invention) According to the present invention, an object of the present invention is to detect an overlap between intake and exhaust valves of a four-cycle engine including an exhaust control valve that changes an exhaust passage area according to an operating state of the engine. Overlap detection means, internal pressure detection means for detecting the intake pipe internal pressure near the intake valve at the time of the overlap, internal pressure increase / decrease determination means for detecting an increase / decrease in the intake pipe internal pressure, and exhaust control for reducing the intake internal pressure An exhaust control device for an engine, comprising: a rotation direction determining means for determining a rotation direction of the valve and rotating the exhaust control valve in the direction.

(Operation) In the case of overlap where the intake / exhaust valve opening periods overlap,
Since the intake pipe and the exhaust pipe sandwich the combustion chamber and communicate with each other,
The exhaust pipe internal pressure becomes substantially equal to the intake pipe internal pressure. Since the opening of the exhaust control valve is controlled so that the intake pipe internal pressure near the intake pipe during this overlap is always minimized,
At this time, the internal pressure of the combustion chamber and the internal pressure of the exhaust pipe near the exhaust valve are also minimized. Therefore, the amount of combustion gas in the combustion chamber blown back into the intake pipe is minimized, the intake of fresh air is promoted, and the exhaust pipe internal pressure is minimized at the end of the exhaust stroke, so that exhaust is promoted. As a result, volume efficiency is improved. The above effects can always be obtained regardless of changes in various conditions such as the engine rotation speed and the load.

(Embodiment) FIG. 1 is an overall view showing an embodiment of the present invention for a motorcycle, FIG. 2 is a functional block diagram thereof, FIG. 3 is an operation explanatory view, and FIG. 4 is a flow chart of the operation.

In this figure, reference numeral 10 is a crankcase, 12 is a cylinder, 14 is a crankshaft, 16 is a piston, 18 is a connecting rod,
20 is an intake valve and 22 is an exhaust valve. The intake valve 20 and the exhaust valve 22 are opened and closed by a valve mechanism (not shown). The end of the valve opening period 22A of the exhaust valve 22 overlaps with the beginning of the valve opening period 20B of the intake valve 20, and an overlap period shown by T in FIG. 3 (A) is formed.

24 is an intake pipe connected to the intake valve 20.
The upstream side of is connected to the intake cleaner 26. Reference numeral 28 is an intake filter housed in the intake cleaner 26.

Reference numeral 30 is a load-responsive carburetor, which is attached in the middle of the intake pipe 24 to control the intake flow rate. That is, this vaporizer 30 is
A throttle valve 32 and a piston valve 34 located upstream of the throttle valve 32 and responsive to negative pressure are provided.
Moves up and down to keep the negative pressure below the piston valve 34 substantially constant. A jet needle 36 is suspended on the piston valve 34,
As the piston valve 34 moves up and down, the jet needle 36 moves back and forth in the main nozzle 38, and the fuel supply amount is controlled according to the intake flow rate.

40 is an exhaust pipe, the upstream end of which is connected to the exhaust valve 22,
Its downstream end is connected to the expansion chamber 42. This exhaust pipe 40
In the vicinity of the open end on the downstream side, that is, the open end to the expansion chamber 42,
A butterfly type exhaust control valve 44 is mounted. This exhaust control valve
44 is the fully closed position, and reduces the exhaust dew area to about 1/2. The exhaust control valve 44 is opened and closed by a servo motor 46 via a wire. The opening θ of the exhaust control valve 44 is the valve opening detection means 48A.
Is detected by the potentiometer 48.

Reference numeral 50 is a pressure sensor that detects the internal pressure P in the intake pipe 24 near the intake valve 20, and forms an intake pipe internal pressure detection means 50A. Further, 52 is a crank angle detecting means 52A for detecting the crank angle Θ.
As an angle sensor.

These intake pipe internal pressure P, crank angle Θ and exhaust control valve 44
The angle θ is input to an arithmetic unit (hereinafter referred to as CPU) 56 via an A / D converter (not shown) and the interface 54. The CPU 56 obtains the rotational direction of the exhaust control valve 44 in which the internal pressure P near the intake valve 20 in the intake pipe 24 decreases, and the servo is performed via the output interface 58, the D / A converter (not shown) and the driver 60. The motor 46 is rotated in that direction (the direction in which the internal pressure P is reduced).

Next, the operation of this embodiment will be described. From the viewpoint of its function, the CPU 56 sucks from the crank angle Θ as shown in FIG.
Overlap detection means 62 for detecting the overlap T of the exhaust valves 20 and 22, and an internal pressure for determining whether the internal pressure P increases or decreases when the exhaust control valve 44 is rotated in a certain direction within the overlap T. An increase / decrease determination unit 64 and a rotation direction determination unit 66 that determines the direction in which the internal pressure P decreases and rotates the exhaust control valve 44 in this direction are provided.

The CPU 56 enters a subroutine shown in FIG. 4 in the middle of a series of continuous operations, and first determines whether the operating state has changed (step 100). This is determined based on operating conditions such as a change in the engine speed obtained from the crank angle Θ or a change in the opening of the throttle valve 32. Flag n = 1 when the operating state changes
As a result (step 102), the opening degree θ obtained from the angle sensor 48 is slightly increased to θ + Δθ (step 104). The CPU 56 stores the overlap time T stored in advance based on the crank angle Θ.
Wait until this crank angle Θ enters (step 106),
Once inside the overlap T, it is then determined how the internal pressure P changes with respect to the time t, that is, whether the internal pressure P increases or decreases (step 108). The internal pressure P ₀ obtained by the previous arithmetic operation of this subroutine and the internal pressure P obtained by the present arithmetic operation are compared, and if P> P _0, that is, when the internal pressure is increasing, the flag n = -1 ( Step 110). At this time, if there is no change in operating conditions in the next operation (step 100),
The opening is rotated to θ = θ−Δθ (step 104). That is, the exhaust control valve 44 is rotated in the opposite direction. If P = P ₀ , the flag n = 0 is set (step 112), the opening θ is not changed (step 104), and the motor 46 is stopped. Further, if P <P _0, that is, the internal pressure P is decreasing, the flag n =
The value is set to 1 (step 114) and the motor 46 is rotated in the same direction by Δθ (step 104).

While the above operation is repeated, the motor 46 is rotated in the direction in which the internal pressure P is minimized, and the operating state changes (step 10
0) Repeat the operations from step 102 onward.

The above operation will be described below with reference to FIG. For example, when the exhaust control valve 44 is located at the position indicated by the solid line a in FIG. 7B, the internal pressure P increases within the overlap T as indicated by the solid line a in FIG. Control valve 44 to b, c, d
If the positive pressure wave propagating from the exhaust valve 22 in the exhaust pipe 40 toward the control valve 44 is gradually closed, the negative pressure wave x generated by the expansion at the open end of the expansion chamber 42 and returning will be returned.
, The positive pressure wave y reflected back by the control valve 44
The intensity ratio y / x of gradually increases. Then, when the exhaust flow passage area is reduced to 1/2, it is y = x when fully closed, and the positive and negative pressure waves cancel each other out in the vicinity of the exhaust valve 22. Therefore, at this time, the internal pressure P on the intake side, which is substantially equal to the internal pressure on the exhaust side, becomes the minimum.

Thus, the internal pressure P is minimized in the overlap time T, so that the outflow of exhaust gas from the combustion chamber to the exhaust pipe 40 is promoted,
Moreover, the blowback to the intake pipe 24 becomes the weakest. Therefore, volume efficiency is improved and output characteristics are improved. Further, since the pressure sensor for obtaining the internal pressure of the intake pipe is less likely to be contaminated by carbon or the like in the exhaust gas as compared with the case where it is provided in the exhaust pipe, there is no risk of malfunction such as malfunction in long-term use.

In the above embodiment, the exhaust control valve is provided near the downstream open end of the exhaust pipe, but the present invention is not limited to this, and when it is provided at another place of the exhaust system, such as in the middle of the exhaust pipe. Is also effective and the present invention includes this. The motor that drives the exhaust control valve is not limited to the servo motor, and may be, for example, a stepping motor.

(Advantages of the Invention) As described above, the present invention monitors the intake pipe internal pressure and controls the exhaust control valve so that the internal pressure is minimized. Therefore, the present invention is not affected by operating conditions such as engine operating speed. The exhaust control valve can be rotated to an opening degree most suitable for obtaining the maximum output characteristic. In addition, it is not affected by changes in engine characteristics over time or environmental changes.

[Brief description of drawings]

FIG. 1 is an overall view showing an embodiment for a motorcycle of the present invention, FIG. 2 is a functional block diagram thereof, FIG. 3 is an operation explanatory view, and FIG. 4 is an operation flow chart. 20 …… Intake valve, 22 …… Exhaust valve, 40 …… Exhaust pipe, 44 …… Exhaust control valve, 50A …… Internal pressure detection means 62A …… Overlap detection means, 64A …… Internal pressure increase / decrease determination means, 66A …… Rotation direction discrimination means.

Claims (1)

[Claims] 1. A four-cycle engine including an exhaust control valve that changes an exhaust flow passage area according to an operating state of the engine, and an overlap detecting means for detecting an overlap between intake and exhaust valves of the engine, and the overlap detecting means. Internal pressure detection means for detecting the internal pressure of the intake pipe near the intake valve, internal pressure increase / decrease determination means for detecting an increase / decrease in the internal pressure of the intake pipe, and a direction in which the rotational direction of the exhaust control valve at which the internal pressure of the intake air is reduced An exhaust control device for an engine, comprising: a rotation direction determination unit that rotates the exhaust control valve.