JP3581718B2 - Engine speed control device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an engine speed control device that controls a fuel supply amount according to the engine speed.
[0002]
[Prior art]
2. Description of the Related Art As an engine speed control device of this type, a so-called PID calculation of proportional, integral, and differential is conventionally performed on a voltage corresponding to a difference between a target speed and an engine speed, and a fuel injection device and a throttle are operated in accordance with the calculated result. 2. Description of the Related Art A technique for controlling a fuel supply amount such as a control device is known.
[0003]
The relationship between the fuel supply amount and the change in the engine speed is not constant and has the following characteristics. That is, when the engine speed is low, the change range of the engine speed is large with respect to the increase and decrease of the fuel supply amount, and the time delay of the change is large. Therefore, in order to secure control stability, it is desirable to set the differential amplification and the proportional amplification low. On the other hand, when the engine speed is high, the change width of the engine speed is small with respect to the increase and decrease of the fuel supply amount, and the time delay of the change is small. Therefore, it is desirable to improve the transient characteristics (instantaneous fluctuation rate, settling time) by increasing each of the proportional, integral, and differential amplification factors.
[0004]
As such a remedy, the present applicant has already proposed a technique in which some or all of the coefficients of the PID calculation are made variable according to the engine speed as shown in Japanese Patent Application Laid-Open No. 03-11141. I have. According to this method, when the engine is running at a low speed, the coefficients of the proportional, integral, and differential calculations are reduced to perform highly stable control, and when the engine is running at a high speed, the coefficients are increased to perform control with excellent transient characteristics. However, if the operation speed of the actuator that controls the fuel supply rate is too fast or too slow compared to the response speed of the engine, the control at low speed rotation becomes unstable or the control at high speed rotation follows. It was considered that the property was reduced.
[0005]
In order to improve the response of the actuator to this point, as disclosed in Japanese Patent Application Laid-Open No. H04-60141, the present applicant feedback-amplifies a signal indicating the operation speed of the actuator and controls the rotation speed in accordance with the response speed of the engine. Has been proposed, in which the feedback amount is continuously varied in accordance with the engine speed when performing the control. As described above, by continuously varying the feedback amount of the signal indicating the operation speed of the actuator according to the engine speed, when the engine speed is low, the followability of the actuator is delayed, and the engine speed is high. Occasionally, they have achieved certain results by increasing their ability to follow.
[0006]
[Problems to be solved by the invention]
However, if it is attempted to extend the engine control speed range to a wider range, it has been considered that transient performance must be sacrificed in order to ensure stability.
[0007]
Therefore, according to the present invention, even if the engine control speed range is extended to a wider range, it is possible to perform engine control with excellent stability at low engine speed according to the performance of the actuator, and to perform high speed engine control. It is an object of the present invention to provide an engine speed control device capable of performing engine control with excellent transient performance at times.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an engine speed control device of the present invention includes target speed setting means for setting a target speed of the engine as a voltage signal, and detecting the speed of the engine as a pulse train signal. Rotation frequency detection means for converting a frequency into a voltage signal and detecting the voltage as a voltage signal; an actuator for supplying fuel to the engine according to an operation position; an operation position detection means for detecting the operation position of the actuator; Superimposing means for superimposing a speed signal indicating a change in the operating position detected by the means on a voltage signal indicating the target rotational speed set by the target rotational speed setting means; and Fuel control means for controlling the operating position of the actuator based on a voltage signal indicating the number of revolutions. Superposition degree setting means for setting, as a superposition degree, a degree of superposition of a speed signal indicating a change in the operating position by the superposition means on a voltage signal indicating the target rotation number; A time constant setting means for setting a time constant for determining a conversion speed in the frequency-voltage conversion of the detection means; and a signal to the superimposition degree setting means when the engine speed exceeds a predetermined value. The superimposition degree setting unit outputs a signal to the time constant setting unit so that the superposition degree set by the setting unit is small, and the superimposition degree setting unit is configured to reduce the time constant set by the time constant setting unit. And setting change means for changing the setting by the time constant setting means .
[0009]
[Action]
The engine speed control device of the present invention sets the target engine speed as a voltage signal by the target speed setting means, detects the engine speed as a pulse train signal by the speed detection means, and converts the frequency signal into a frequency voltage signal. Converted and detected as a voltage signal, an actuator supplies fuel corresponding to the operation position to the engine, the operation position detection means detects the operation position of the actuator, and the operation detected by the operation position detection means A speed signal indicating a change in position is superimposed on a voltage signal indicating the target speed set by the target speed setting device by a superposition device, and the superimposed signal and the engine speed by the fuel control device are calculated. When controlling the operating position of the actuator based on the voltage signal indicated by the The degree at which the speed signal indicating the change in the operating position is superimposed on the voltage signal indicating the target rotational speed is set as a superimposition degree by the superimposition degree setting means, and the time constant setting means determines the degree of superimposition in the frequency-voltage conversion of the rotation number detecting means. A time constant for determining the conversion speed is set, and when the engine speed exceeds a predetermined value, a signal is output to the superimposition degree setting means, and the superimposition degree set by the superimposition degree setting means is reduced. And outputting a signal to the time constant setting means , and changing the setting by the superimposition degree setting means and the time constant setting means so that the time constant set by the time constant setting means is reduced. To change.
[0010]
【Example】
An embodiment of an engine speed control device of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are circuit diagrams showing the electrical configuration of the engine speed control device 10 of the present embodiment. The rotation speed control device 10 outputs a target rotation speed of the engine 20 as a voltage signal ec, and a frequency / voltage conversion circuit (hereinafter, referred to as an FV conversion circuit) for converting the engine rotation speed into a voltage signal en. 40, a rotation speed discriminator 49 that generates a switching signal cn when the engine rotation speed exceeds a predetermined rotation speed, and a proportional, integral, and integral control based on the voltage signal ec of the target rotation speed and the voltage signal en of the engine rotation speed. A PID circuit 50 for executing each operation of differentiation is provided. The engine 20 is provided with a speed detector 23 for detecting the engine speed, and outputs a pulse signal Pn having a period proportional to the engine speed. When the pulse signal Pn is input to the above-described FV conversion circuit 40, it is converted into a voltage signal en corresponding to the cycle of the pulse signal Pn. The throttle control device 27 includes a solenoid actuator 27a for driving a throttle valve 25 provided in an intake pipe 26 of the engine 20, and an actuator position detector 28 for detecting an operation position of the actuator 27a. Have been. When the operation position of the actuator 27a is detected by the actuator position detector 28, the detection signal 28a is input to the target rotation speed setting unit 30.
[0011]
The target rotation speed setting unit 30 includes a detection circuit 31, a target rotation speed setting device 32, a differentiating circuit 34, and a superimposing circuit 36. The detection signal 28a detected by the actuator position detector 28 is converted by the detection circuit 31 into a DC voltage signal ea. When the voltage signal ea is differentiated by a differentiating circuit 34 composed of a capacitor 32a and a resistor 32b, it is input to a superimposing circuit 36 via a voltage follower constituted by an operational amplifier 33. Further, a voltage signal es corresponding to the target rotation speed set by the target rotation speed setting device 32 is also input to the superimposing circuit 36.
[0012]
The superimposing circuit 36 comprises an operational amplifier 38. A resistor 44 is connected between the output terminal 38b and the inverting input terminal 38c of the operational amplifier 38, and a resistor 45 is connected to both ends of the resistor 44. And an analog switch 46 are connected in series. The analog switch 46 is turned on / off by the switching signal cn from the rotation speed discriminating unit 49 to change the feedback resistance value of the operational amplifier 38.
[0013]
A resistor 44 is provided between the inverting input terminal 38c and the output terminal 38b of the operational amplifier 38. The voltage signal es of the target rotation speed setter 32 is input to the non-inverting input terminal 38d of the operational amplifier 38. Therefore, when the differentiated voltage signal ea is not input to the inverting input terminal 38c, the voltage of the voltage signal ec of the superposition circuit 36 corresponds to the voltage of the voltage signal es. When the operation position of the actuator 27a moves to the fuel increasing side, when the voltage signal ea differentiated by the differentiating circuit 34 is processed by the superimposing circuit 36, the voltage signal ec of the superimposing circuit 36 is lower than the voltage signal es. It is configured to become a voltage, and to become a high voltage when the fuel moves to the fuel reduction side.
[0014]
The PID circuit 50 includes an operational amplifier 54, an integrating circuit 60 provided between the output terminal 54d of the operational amplifier 54 and the inverting input terminal 54e, an input resistor 61 having one end connected to the inverting input terminal 54e, It comprises an arithmetic circuit comprising a differentiating circuit 62 connected in parallel with the device 61. The integrating circuit 60 includes a capacitor 60a, and a series circuit of a capacitor 60b and a resistor 60c connected in parallel to the capacitor 60a. The differentiating circuit 62 is configured by a series circuit of a capacitor 62a and a resistor 62b.
[0015]
The F / V conversion circuit 40 outputs a fixed-width pulse signal each time a pulse signal Pn having a period proportional to the engine speed is input from the above-described rotation speed detector 23, and the fixed-width pulse signal. Is provided with a low-pass filter 44 for smoothing. The low-pass filter 44 includes a time constant circuit including resistors 47a and 47b and a capacitor 47c, an analog switch 59 for changing the time constant, and an operational amplifier 48 forming a voltage follower circuit. The rotational speed determination unit 49 forms a comparator from an operational amplifier 79 having hysteresis characteristics using the resistors 73 and 74. The output signal of the operational amplifier 48 is input to the non-inverting input terminal 79a of the operational amplifier 79, and the reference voltage set by the resistors 71 and 72 is input to the inverting input terminal 79b. This reference voltage is set to a voltage value corresponding to the engine speed during high-speed rotation.
[0016]
The output terminal 79c of the operational amplifier 79 is connected to the above-described analog switches 46 and 59, and the analog switches 46 and 59 are turned on and off by the output signals.
[0017]
Upon receiving the output signal eo of the above-described PID circuit 50, the PWM (pulse width modulation) conversion circuit 76 outputs a drive signal having a pulse width corresponding to the output signal eo to the power transistor Tr in the next stage. The base B of the power transistor Tr is connected to the output terminal of the PWM conversion circuit 76, the collector C is connected to one end of a parallel circuit of the actuator 27a and the diode D, and the emitter E is grounded.
[0018]
The operation of the rotation speed control device 10 having the configuration described above will be described. When a detection signal 28a indicating the position of the actuator is input from the actuator position detector 28 to the detection circuit 31, the detection circuit 31 converts the detection signal 28 into a direct current to generate a voltage signal ea. When the voltage signal ea is differentiated by the differentiating circuit 34, the voltage signal ea becomes a voltage signal corresponding to a change in the operating position (operating speed) of the actuator 27a and is input to the inverting input terminal 38c of the operational amplifier 38. The voltage signal es output from the target speed setting device 32 is input to the non-inverting input terminal 38d. The differentiated voltage signal ea is amplified by the operational amplifier 38 at a predetermined gain G and is superimposed on the voltage signal es. A voltage signal ec including a voltage signal corresponding to a change in the operation position of the actuator 27a is output from the output terminal 38b. At this time, the feedback amount of the superimposing circuit 36 is determined by the value of the feedback resistor Rf, and this value is switched between two stages by the on / off operation of the analog switch 46. That is, when the rotation speed of the engine 20 described later is low, the rotation speed determination unit 49 outputs an off signal to the analog switch 46. When the analog switch 46 is turned off, one end of the resistor 45 is cut off, so that the value of the feedback resistor becomes the value of the resistor 44. When the rotation speed of the engine 20 is high, when the rotation speed determination unit 49 outputs an ON signal to the analog switch 46, the value of the feedback resistance becomes a value obtained by connecting the resistors 44 and 45 in parallel. Therefore, when the rotation speed of the engine 20 is low, the feedback amount is large, so that a stable voltage signal ec having a relatively large braking force with respect to a change in the operating position of the throttle 27a is output. Since the amount of feedback is small, a voltage signal ec that follows the change in the operating position of the throttle 27a with a relatively small braking force is output.
[0019]
In the F / V conversion circuit 40 that outputs the rotation speed of the engine 20, the pulse conversion unit 42 fixes the pulse signal Pn having a cycle proportional to the engine rotation speed from the rotation speed detector 23 each time it is input to the pulse conversion unit 42. A pulse signal having a width is output. When this fixed-width pulse signal is input to the low-pass filter 44 in the next stage, it is smoothed by the low-pass filter 44, and the voltage signal en is input to the PID circuit 50 via the operational amplifier 48 as described above. In the low-pass filter 44, the time constant of the time constant circuit is switched in two stages by the analog switch 59, and when the resistors 47a, 47b and the capacitor 47c are R6, R5, and C1, respectively, the time determined by turning on the analog switch 59 It is switched to one of the constant C1 · (R5 + R6) / R5 · R6 and the time constant C1R5 determined by turning off the analog switch 59. The switching signal of the analog switch 59 is compared with the reference voltage divided by the resistor 71 and the resistor 72 and the output voltage of the engine speed outputted from the low-pass filter 44 by the comparator 79 to make the H level or the L level. Become. When the rotation speed of the engine 20 is low, the output voltage of the engine rotation speed falls below the reference voltage, the analog switch 59 is turned off, and the time constant increases to C1R5. When the rotation speed of the engine 20 is high, the output voltage of the engine rotation speed exceeds the reference voltage, the analog switch 59 is turned on, and the time constant becomes small as C1Ｃ (R5 + R6) / R5 ・ R6.
[0020]
As described above, when the rotation speed of the engine 20 is lower than a preset value, the time constant of the low-pass filter is set large to reduce the residual ripple of the pulse, increase the superimposition degree of the superimposition circuit 36, and increase the actuator 27a. By increasing the braking force, the movement of the actuator 27a is slowed to achieve stability. On the other hand, when the rotation speed of the engine 20 is higher than a preset value and the response of the rotation speed control is fast, the time constant of the low-pass filter is set to be small and the F / V conversion speed is increased to increase the F / V conversion speed. The detection delay is reduced, the degree of superimposition of the superimposition circuit 36 is reduced, and the braking of the actuator 27a is weakened, thereby speeding up the movement of the actuator 27a and improving the followability.
[0021]
Note that the above embodiment can be variously modified without departing from the present invention. For example, in the above embodiment, the feedback amount and the time constant of the low-pass filter are switched in two stages, but may be switched in three or more stages. In setting the feedback amount, instead of cutting off the resistor 45 between the inverting input terminal and the output terminal of the operational amplifier by the analog switch 46, the resistance value of the resistor 37 connected to the inverting input terminal is varied. Is also good. Further, instead of the resistor 47a (R6) for determining the time constant of the low-pass filter 44 being cut off by the analog switch 59, the capacitance of the capacitor 47c may be varied by the analog switch. Further, the low-pass filter is not limited to a capacitor and a resistor, and may be configured by combining a coil. Further, the present invention is not limited to a gasoline engine, and can be applied to various engines such as a diesel engine. Further, the switching of the feedback amount of the present embodiment and the switching of the low-pass filter 44 are applied to a superimposing circuit (described in Japanese Patent Application Laid-Open No. 04-60141) that continuously varies the feedback amount according to the engine speed. Is also good. Further, although the throttle control device is used as the fuel supply amount adjusting mechanism, the present invention may be applied to a fuel injection device having a structure in which the upper limit of operation of the actuator is mechanically restricted.
[0022]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the engine control apparatus of this invention, even if it expands the rotation speed area | region of engine control to a wide range, it does not sacrifice any performance at the time of low-speed rotation and high-speed rotation of an engine, Accordingly, the engine control with excellent stability can always be performed when the engine is running at a low speed, and the engine control with excellent transient performance can be always performed when the engine is running at a high speed.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an electrical configuration of an engine speed control device 10 according to an embodiment.
FIG. 2 is a circuit diagram showing an electrical configuration of the engine speed control device 10 continued from FIG. 1;
[Explanation of symbols]
10 Rotational speed control device 20 Engine 30 Target rotational speed generation circuit 30
40 ... frequency voltage conversion circuit

Claims (2)

Target speed setting means for setting the target speed of the engine as a voltage signal;
After detecting the number of rotations of the engine as a pulse train signal, the number of rotations detecting means for converting the frequency to voltage and detecting it as a voltage signal,
An actuator for supplying fuel to the engine according to an operation position;
Operating position detecting means for detecting the operating position of the actuator,
Superimposing means for superimposing a speed signal indicating a change in the operating position detected by the operating position detecting means on a voltage signal indicating the target rotational speed set by the target rotational speed setting means;
Fuel control means for controlling the operating position of the actuator based on the superimposed signal and a voltage signal indicating the engine speed,
In the engine speed control device provided with
Superimposition degree setting means for setting the degree of superimposition of the speed signal indicating the change in the operating position on the voltage signal indicating the target rotation speed as the superimposition degree by the superimposing means;
Time constant setting means for setting a time constant for determining the conversion speed in the frequency voltage conversion of the rotation speed detection means,
When the number of revolutions of the engine exceeds a predetermined value, a signal is output to the superimposition degree setting means, and the superimposition degree set by the superimposition degree setting means is reduced, and a signal is transmitted to the time constant setting means . And setting change means for changing the setting by the superposition degree setting means and the time constant setting means so that the time constant set by the time constant setting means is reduced. Engine speed control device. The superimposing means superimposes the negative feedback amplification by differentiating the change amount of the operating position, and adds the negative feedback amplified change amount of the operating position to a voltage signal indicating the target rotation speed.
2. The engine speed control device according to claim 1, wherein the superimposition degree setting means sets the negative feedback amount as a superimposition degree.

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