JPH0830415B2 - Exhaust timing control method for 2-cycle engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust timing control method for a two-cycle engine.

BACKGROUND ART It is well known that the braking force by engine braking of a two-cycle engine is smaller than that of a four-cycle engine.

Further, there is an exhaust timing control device that adjusts the upper end position of the exhaust port of a two-cycle engine to control the opening timing of the exhaust port to control the engine output.
It is known from Japanese Patent 60-20622.

SUMMARY OF THE INVENTION The present invention provides an exhaust timing control method for increasing the engine braking force of a two-cycle engine by utilizing an exhaust timing control device of the two-cycle engine in view of the small engine braking force of the two-cycle engine as described above. It is an object.

In the exhaust timing control method for a two-cycle engine according to the present invention, the opening area of the exhaust port is changed by adjusting the upper end position of the exhaust port, and the timing at which the exhaust gas exits the exhaust port is controlled to control the engine output. An exhaust timing control method for a two-cycle engine, characterized in that, during deceleration, the upper end position of the exhaust port is set to a position lower than the set position other than during deceleration.

Therefore, at the time of deceleration, the upper end position of the exhaust port can be set to a position lower than the set position other than at the time of deceleration. When the vehicle decelerates due to the lowering of the exhaust port upper end position, the exhaust port fully close timing is accelerated, the compression stroke distance of the intake air-fuel mixture by the piston is increased, and the compression pressure is increased. Therefore, heat generation due to compression also increases. By the way, since the engine cylinder head is configured to dissipate the heat, the loss of thermal energy is increased by the increase of the compression heat, and the braking force of the engine brake is increased.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment apparatus in which the exhaust timing control method according to the present invention is applied to a two-cycle engine mounted on a motorcycle.

The two-cycle engine 1 has an exhaust port 4 that opens in a cylinder 2 and is opened and closed by a piston 3. An exhaust pipe 6 in which an expansion chamber 5 is formed is connected to the exhaust port 4 to form an exhaust passage. The expansion chamber 5 is formed in a shape in which the central portion thereof swells in the exhaust gas flow direction and both end portions thereof are narrowed, so that the so-called exhaust reflected wave action (Kadenashi effect) can be utilized.

A flap plate 8 is pivotally provided on the upper edge of the exhaust port 4 so as to be coupled to a rotary shaft 9. The rotating shaft 9 is an output shaft of the speed reducer 12 that reduces the rotational output of the pulse motor 10, and the flap plate 8 is pivoted according to the rotational output of the pulse motor 10 to be positioned at a desired angular position. The free end of the flap plate 8 is located at the upper edge of the exhaust port 4 and forms the upper edge of the exhaust port 4. Therefore, the pivoting of the flap plate 8 causes the upper edge position of the exhaust port 4 to move up and down, and the exhaust timing can be changed. That is, the flap plate 8, the speed reducer 12 and the pulse motor 10 constitute an exhaust timing adjusting mechanism. The pulse motor 10 is provided with an encoder 13 for detecting its operating state. An output signal of the encoder 13 is input to the address detection circuit 14 to drive the flap plate 8.
An address signal indicating the operating position of is input from the address detection circuit 14 to the control circuit 16.

On the other hand, the synchronizing pulse generating means 23 outputs a rotation angle position signal (hereinafter referred to as "B") synchronized with the rotation of the crankshaft 24 of the engine.
Pulse). Specifically, a rotor that rotates in synchronism with the rotation of the crankshaft 24, which has a large number of claws 23a, is combined with a magnetic pickup 23b, and is applied as an output signal of the magnetic pickup 23b.
Means for obtaining pulses are known.

The control circuit 16 is composed of, for example, a microcomputer including a CPU, a ROM, and a RAM, and performs an arithmetic operation according to a main routine or an interrupt subroutine described later.

Further, a throttle signal corresponding to the rotational position is input to the control circuit 16 from a throttle sensor 32 that detects the rotational position of the throttle grip 31 as a parameter indicating the throttle valve opening of the engine 1.

Based on the engine speed Ne and the throttle signal calculated based on the above-mentioned B pulse, the control circuit 16 determines the target rotational angle position of the flap plate 8 corresponding to the target exhaust timing at which the exhaust port 4 should start to open on the crank angle ( Hereinafter, the target exhaust angle will be calculated) θ _AT , and the pulse motor 10 will be driven based on the calculated result to adjust the exhaust timing.

2 and 3 control the setting operation of the target exhaust angle θ _AT of the control circuit 16 and the command operation for making the rotational angle position (exhaust angle) θ _V of the flap plate 8 match the target exhaust angle θ _AT. It is a flow chart which shows a returning main routine and a subroutine.

As shown in FIG. 2, when the power is turned on, the main routine is sequentially executed in each step in the control circuit 16 in accordance with the fixed cycle clock pulse. First, in the first step S ₁ , the initialization operation is executed. Next, a comparison is made between the current exhaust angle θ _V calculated by the address signal output from the address detection circuit 14 and the target exhaust angle θ _AT obtained by executing a subroutine described later (steps S ₂ and S ₃ ). If the difference between the current exhaust angle θ _V and the target exhaust angle θ _AT is larger than the predetermined value ε _{1, the} drive circuit 36 is driven by that amount to drive the pulse motor 10 (steps S ₄ and S ₅ ).

In the description of the present embodiment, for convenience, the exhaust angle on the most advanced side, that is, the exhaust angle corresponding to the rotation upper end position of the flap plate 8 is zero, and the exhaust timing on the most retarded side, that is, the flap plate rotation. The exhaust angle corresponding to the lower end position is set to the maximum value.

FIG. 3 shows a flowchart of a fixed cycle interrupt subroutine which is executed by interrupting the main routine at regular time intervals. In this subroutine, when the main routine is interrupted, first, the engine speed Ne and the throttle opening θ _TH are fetched (step S ₆ ), and the engine speed Ne and the throttle opening θ _TH are calculated based on the map stored in advance. The base exhaust angle θ _T corresponding to is retrieved (step S ₇ ). Next, by subtracting the previous throttle opening θ _TH (n-1) from the current throttle opening θ _TH (n), the throttle opening change Δθ _TH per unit time is calculated (step S ₈ ), and Δθ
_TH is whether the discrimination positive value or a negative value (step S _9). By this discrimination, it is possible to discriminate whether the driver of the motorcycle desires acceleration / deceleration or traveling at a constant vehicle speed. If it is determined in step S ₉ that Δθ _TH is a positive value, the absolute value of Δθ _TH is further determined to be the predetermined value a ₁
Greater whether discriminating (Step S _10). When the absolute value of Δθ _TH is larger than the predetermined value a ₁ in step S _10, it is determined that the driver is requesting relatively rapid acceleration, and the predetermined value n ₃ is set as the correction coefficient N ( Step S ₁₁ ). If the absolute value of Δθ _TH is smaller than the predetermined value a ₁ in step S ₁₀ , it is determined that the driver is requesting relatively gentle acceleration, and the predetermined value n ₂ is set as the correction coefficient N. set (step S _12). If [Delta] [theta] _TH is as a negative value in step S _9, further, the absolute value of [Delta] [theta] _TH is subjected to determination of whether larger than the predetermined value a ₀ (Step S _13), absolute [Delta] [theta] _TH If the value is greater than the predetermined value a ₀ , it is determined that the driver is requesting relatively rapid deceleration, and in this case, the base value is set regardless of other engine parameters (Ne, θ _TH ). Exhaust angle θ _T
Sets the maximum value corresponding to the rotational end position of the flap plate as (step S _14), it sets a predetermined value n ₁ as the correction coefficient N (step S _15). Further, towards the absolute value of [Delta] [theta] _TH in step S ₁₃ is the case that it is determined that the predetermined value a ₀ is less than, it is determined that when the driver is requesting a relatively moderate deceleration correction factor Predetermined value as N
Set n ₀ (step S ₁₆ ). Then, in step S ₁₁ ,
The target exhaust angle θ _AT is obtained by dividing the base exhaust angle θ _T set in step S ₇ or S ₁₄ using the correction coefficient N set in S ₁₂ , S ₁₅ or S ₁₆ (step S
₁₇ ). As can be understood from this, the predetermined values n ₀ to n ₃
Determines the responsiveness of the exhaust timing control to the driver's throttle operation. For example, n ₀ = 0.9, n ₁ = 1, n ₂ =
It is conceivable to set the value to 1.1, n ₃ = 1.2.

In the above-mentioned embodiment, the exhaust angle corresponding to the pivoting lower end position of the flap plate 8 is set to its maximum value,
Since the target exhaust angle θ _AT is obtained by dividing the base exhaust angle θ _T obtained in step S ₇ or S _{14 of the} fixed cycle interrupt subroutine by the correction coefficient N, as described above, the predetermined value n ₀ To n ₃ are set, the exhaust port upper end position set at the time of deceleration becomes a position lower than the exhaust port upper end position set at the time other than during deceleration.

It is also possible to make the maximum value of the exhaust angle correspond to the upper rotational end position of the flap plate 8. In this case, the target exhaust angle θ _AT is obtained by multiplying the base exhaust angle θ _T by the correction coefficient N. Alternatively, another value may be set to the predetermined values n ₀ to n ₃ .

EFFECTS OF THE INVENTION As described above, in the exhaust timing control method for a two-cycle engine according to the present invention, the upper end position of the exhaust port is at a position lower during deceleration than at the set position other than during deceleration. Therefore, the output performance of the engine can be sufficiently brought out except during deceleration, while the engine brake with sufficient braking force can be obtained during deceleration, which is preferable.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment apparatus when the present invention is applied to a two-cycle engine mounted on a motorcycle, and FIG.
FIG. 3 and FIG. 3 are flowcharts showing the operation of the embodiment apparatus of FIG. Description of main part code 1 …… 2-cycle engine 4 …… Exhaust port 8 …… Flap plate 10 …… Pulse motor 31 …… Throttle grip 32 …… Throttle sensor

Claims (1)

[Claims] 1. An exhaust timing control method for a two-cycle engine, wherein the opening area of the exhaust port is changed by adjusting the upper end position of the exhaust port to control the timing of the exhaust gas from the exhaust port to control the engine output. A method for controlling exhaust timing of a two-cycle engine, characterized in that, during deceleration, the upper end position of the exhaust port is set to a position lower than the set position other than during deceleration.