JP2625794B2 - Control device for movable valve provided in engine air flow path - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a movable valve control device provided in an air passage such as an engine intake passage or an exhaust passage to improve engine output characteristics.

[Prior Art] Particularly in a two-stroke engine or the like, a movable valve is provided in an exhaust passage near an exhaust port of the engine so that the valve is continuously opened according to the engine speed, thereby improving engine exhaust efficiency and increasing engine output. It has been proposed to improve the properties.

For example, Japanese Patent Laying-Open No. 54-158514 discloses a system in which a movable valve is feedback-controlled so as to follow a target opening that increases in accordance with the engine speed.

In such feedback control, the driving speed of the movable valve is suppressed or the dead zone is increased in order to prevent hunting. However, these cause deterioration of transient response and control accuracy.

Therefore, for example, Japanese Patent Application Laid-Open Nos. 62-622 and 62-609
In Japanese Patent Publication No. 22, a control device is proposed in which a DC motor for driving the movable valve is chopper-controlled to realize excellent transient response and high control accuracy.

[Problems to be Solved by the Invention] However, in each of the proposed control devices, when the movable valve is close to the target opening and the deviation is small, the ON duty of the chopper motor drive signal is also small, and the valve drive is performed. Power drops.

Here, exhaust deposits and the like tend to accumulate on the movable valve, and the conventional control device has a problem in that the valve driving force is insufficient for a relatively slight change in the target opening and the followability is poor.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a control device for a movable valve that has excellent transient response without causing hunting and the like and also has good followability to a target value.

[Means for Solving the Problems] The configuration of the present invention will be described with reference to FIG. 1. A movable valve is provided in an air flow passage communicating with an engine cylinder, and the movable valve is operated in accordance with an input drive signal. The control device of the movable valve of the engine provided with the driving means includes a means for detecting an engine speed, a means for setting a target opening of the movable valve according to the engine speed, and a current valve opening. Detecting means, calculating a difference between the target opening degree and the detected valve opening degree, and continuously outputting a driving signal to the driving means when the difference exceeds a first reference value. When the difference is between the first reference value and the second reference value smaller than the reference value, the drive signal is pulsed so that the output duty thereof gradually increases with time. And the difference is greater than the second reference value. Control means for canceling the driving signal when the driving signal is smaller than the driving signal.

[Operation] In the control device having the above configuration, when the detected valve opening is greatly different from the target opening, the difference exceeds the first reference value, and the driving signal is transmitted to the driving means. And the movable valve is quickly operated toward the target opening.

When the valve opening approaches the target opening and the difference is smaller than the first reference value and larger than the second reference value, the drive signal is given to the drive means in a pulse form. In addition, the output duty is given so as to gradually increase with the passage of time.

That is, the output duty of the drive signal is small when the value exceeds the first reference value, and the movable valve operating at high speed is rapidly decelerated.

Further, when the valve opening approaches the target opening and the difference becomes smaller than the second reference value, the drive signal is cancelled, and the movable valve is stopped almost without overshooting near the target opening.

In this state, when the target opening changes relatively small and the difference again becomes a magnitude between the first reference value and the second reference value, the output duty of the drive signal gradually increases with time. Given to be. Thus, even when the exhaust valve deposits and the like and the movement of the movable valve becomes heavy, the movable valve can be operated satisfactorily by the valve driving force of the drive means which is gradually increased.

[Effects] As described above, according to the control device of the present invention, the movable valve can be controlled with good transient response, and the movable valve can accurately follow the target opening regardless of the accumulation of the exhaust deposit and the like. it can.

Embodiment FIG. 2 shows the overall configuration of the control device. The figure shows a two-stroke engine. An intake passage 52 and an exhaust passage 51 are opened in the engine cylinder 5, and these openings are opened and closed by a piston 53 that moves up and down in the cylinder 5.

A semi-circular movable valve 6 is provided on the upper wall near the opening of the exhaust passage 51, and is provided with a DC motor 3 via a known driving mechanism.
And is rotated between an open state and a closed state in the figure. The opening cross-sectional area of the exhaust path 51 changes by opening and closing the movable valve 6.

The rotational position of the DC motor 3 is detected by a potentiometer 2 provided on the DC motor 3, whereby the opening of the movable valve 6 is known.

The control circuit 1 includes a computer 11, an A / D converter 12,
The computer 11 includes a drive circuit 13 and a waveform shaping circuit 14. The computer 11 sets the target valve opening set via the A / D converter 12 to a target opening set according to the engine speed obtained from the speed sensor 4. The driving signals Vop and VcL, which will be described later, are generated based on the comparison result.

The drive signals Vop and VcL are supplied to the DC motor 3 via the drive circuit 13, and operate the movable valve 6 following the target opening.

FIG. 3 shows an example of a setting pattern of the target opening degree θV of the movable valve. In the figure, when the engine is started, the movable valve is fully opened to facilitate starting, and in the low-speed rotation range after the start, the movable valve is fully closed to reduce the exhaust path cross-sectional area. Thereafter, the movable valve is gradually opened to the fully opened state in proportion to the increase in the engine speed.

The setting of the target opening degree θV is performed by a computer by performing an interpolation calculation with reference to an opening degree map stored in advance.

The drive signals Vop and VcL output from the control device are given to the DC motor as a continuous signal or as a chopper pulse signal depending on the difference between the detected valve opening θP and the target opening θV. Can be Details of the fourth
Shown in the figure.

In FIG. 4A, upper and lower openings θUP and θLO, which are second reference values, are set with a predetermined difference above and below the target opening θV. A first reference value (θV + θcH) having a difference θcH above and below the degree,
(ΘV−θcH) is set.

The figure shows a case where the movable valve 6 is closer to the target opening degree θV than the closing side, and in a region where the valve opening degree θP is lower than the reference value (θV-θcH), the drive signal VOP is at the “H” level, The signal VCL becomes "L" level, and all of them are continuously output (FIGS. 4 (2) and (3)).

When the valve opening .theta.P exceeds the reference value (.theta.V-.theta.cH) and reaches the lower limit opening .theta.LO, the drive signal VCL is output intermittently as a "H" level pulse signal.

Further, when the valve opening θP approaches the target opening θV beyond the lower limit opening θLO, the drive signal VCL becomes a continuous signal of “H” level.

The DC motor 3 operates as shown in the table below according to the level changes of the drive signals VOP and VCL.

When the valve opening θP is below the reference value (θV−θcH), the DC motor 3 receives the continuous forward rotation signal.
Is rotated forward at high speed, and the movable valve 6 is quickly operated in the opening direction.

When the value exceeds the reference value (θV−θcH), the forward rotation signal and the brake signal appear alternately. When the value exceeds the reference value (θV−θcH), the duty of the forward rotation signal is small and gradually increases with time. As a result, the DC motor 3 that has been operated at a high speed is greatly decelerated, and the movable valve 6 exceeds the lower limit opening θLO at a speed that does not cause hunting.

When the lower limit opening θLO is exceeded, only the brake signal is output and the operation of the movable valve 6 is stopped.

When the movable valve 6 approaches the target opening degree θV from the open side, the operation is the same as above except that the forward and reverse directions are different.

FIG. 5 shows a processing flow of a computer which enables such control.

In step 101, the target opening θV is calculated by the opening map and the interpolation calculation as described, and the target opening θV is calculated.
, The upper and lower opening degrees θUP and θLO are calculated. In step 102, the current valve opening θP is detected. If the difference from the target opening θV exceeds θcH, the continuous control mode is set (steps 103 and 104). If not, the chopper mode is set (step 105). ).

In steps 106 and 107, it is determined whether the valve opening θP is equal to or less than the lower limit opening θLO or equal to or greater than the upper limit opening θUP, and the valve opening mode (step 108) or the valve closing mode (step 109) is set. If the valve opening θP is between the lower limit opening θLO and the opening θUP, a valve brake mode is set (step 110).

In step 111, when there is a change from the valve open, valve close, and valve brake modes to other valve open and valve close modes, the valve lock prevention timer and the chopper timer are started (steps 112 and 113). When there is a change from the continuous mode to the chopper mode, only the chopper timer is started (steps 114 and 115).

For example, the valve lock prevention timer is turned on for 3 seconds and then turned off for 2 seconds.
When the valve does not operate even if the duty of the valve drive signals Vop and VcL reaches 100% due to exhaust deposit, to prevent burning of the DC motor 3 and to prompt the operation of the valve periodically. It is provided in.

The chopper timer determines the duty of the valve drive signals Vop and VcL, and as shown in FIG.
The N state gradually increases with time ((1) in the figure), the ON time is constant, and the OFF time gradually decreases with time ((2) in the figure), and within a certain period T
It is possible to use those whose ON time rate gradually increases with time ((3) in the figure). These (1),
In each of the cases (2) and (3), the time change of the ON duty can be as shown by the lines a, b, and c in FIG.

Each of the ON and OFF times is in units of m seconds, and which chopper timer is used is appropriately selected depending on conditions.

In steps 116 and 117, it is determined whether the mode is the valve open mode or the valve close mode.
The process proceeds to the following, and if the mode is the valve closing mode, the process proceeds to step 125 and subsequent steps. If it is not in either mode, a valve brake signal is output (step 124).

In step 118, the setting of the continuous mode is confirmed. If the valve lock prevention timer is running in the continuous mode, a valve open signal or a brake signal is issued according to ON / OFF of the timer (steps 121, 122, 123, 124). . Step 118 above
When the chopper mode is set, a valve open signal or a valve brake signal is issued according to the ON / OFF of the chopper timer (steps 119 and 120).

The processing of step 125 and subsequent steps is the same as the processing of step 118 and subsequent steps except that the opening and closing are different.

By the processing in the computer as described above, a good transient response of the movable valve without hunting as described above can be obtained.

Further, according to the present embodiment, for example, the target opening degree θV changes gradually, and the current valve opening degree θP becomes relatively small.
If it deviates from the target opening degree θV within cH,
The chopper timer is started by the determination in step 1, and valve drive signals Vop and VcL whose duty gradually increases with time are supplied to the DC motor 3.

Therefore, even when the movement of the movable valve is heavy due to the accumulation of the exhaust deposit, the movable valve can be operated quickly, and good target following performance can be realized.

In step 115 in FIG. 5 of the above embodiment, if the chopper timer is set to emit a valve brake signal for a certain period of time at the time of activation, and then to issue each signal of a valve opening or valve closing whose duty gradually increases, The movable valve deceleration at the time of mode switching from continuous to chopper can be increased, and good transient response without overshoot can be obtained even if a small θup and θLo are set for a valve with a high drive speed.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention, FIG. 2 is a block diagram of the overall configuration of a control device of the present invention, FIG. FIG. 5 shows the transient response of the valve and the waveform of the drive signal, FIG. 5 is a processing flowchart of the computer, FIG. It is a graph which shows a time change. DESCRIPTION OF SYMBOLS 1 ... Control circuit 11 ... Computer 2 ... Potentiometer (valve opening detection means) 3 ... DC motor (drive means) 4 ... Rotation speed sensor (engine rotation speed detection means) 5 ... Engine cylinder 51 ... Exhaust passage (air passage) 6 Movable valve

Claims (2)

(57) [Claims] 1. A control device for an engine, comprising: a movable valve provided in an air flow passage communicating with an engine cylinder; and drive means for operating the movable valve in response to an input drive signal. Means for detecting the engine speed, means for setting the target opening of the movable valve according to the engine speed, means for detecting the current valve opening, and a valve for detecting the target opening. Means for calculating the difference in opening,
When the difference exceeds the first reference value, a drive signal is continuously supplied to the driving means, and the difference is equal to the first reference value and the second reference value smaller than the reference value. If the difference is smaller than the second reference value, the drive signal is canceled when the difference is smaller than the second reference value. A control device for a movable valve provided in an engine air flow path, comprising: a control unit. 2. The control device according to claim 1, wherein the control signal is periodically canceled when the valve opening does not change even when the output duty of the drive signal reaches 100%. 3. The control device for a movable valve according to claim 1, wherein: