JPH04129859U - Rotational speed control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the occurrence of a control dead zone in a rotation speed control device for an internal combustion engine. [Structure] By controlling the integrating circuit 9 with the output of the comparator 8 that compares the speed detection signal Vn and the target speed setting signal Vno, when the speed detection signal is larger than the target speed setting signal, the signal falls and the speed is detected. An integrated voltage Vi' that increases when the signal is smaller than the target speed setting signal is obtained. By comparing this integrated voltage with the sawtooth signal voltage Vc, a pulse width modulated pulse signal Va is obtained. This pulse signal is applied to the actuator drive circuit 12 to turn on and off the drive current of the actuator 3. Voltage limiting circuits 13 and 14 are connected to the integrating circuit, thereby limiting the range of change in the integrated voltage to within the amplitude range of the sawtooth signal voltage Vc, thereby eliminating a control dead zone.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is an internal combustion engine that controls the rotational speed of the internal combustion engine to match the target speed. The present invention relates to a rotation speed control device.

0002

[Conventional technology]

A rotation speed control device that controls the rotation speed of an internal combustion engine to match the target speed. As shown in Japanese Patent Publication No. 55-15623, the actual rotational speed of the engine and A pulse signal whose pulse width is modulated according to the magnitude relationship with the target speed is obtained, and this pulse This signal turns on the drive current of the actuator that adjusts the amount of fuel supplied to the engine. There is one that turns it on and off.

0003 Figure 4 schematically shows the configuration of a conventional rotation speed control device. 1 is an internal combustion engine, and 2 is a fuel supply amount adjusting means for adjusting the amount of fuel supplied to the internal combustion engine. This adjustment means is, for example, a throttle valve or an injection amount adjustment lamp of a fuel injection pump. It is a lock. 3 is an actuator that operates the fuel injection amount adjusting means 2 according to the drive current. This actuator is driven by a DC power source 4 such as a battery.

0004 5 is a speed proportional to the actual rotational speed N [rpm] of the internal combustion engine, as shown in Fig. 3(A). This is a speed detection circuit that outputs a speed detection signal Vn. Input a signal with a frequency proportional to (for example, the primary voltage of the ignition coil or the speed generator) It consists of a frequency-voltage conversion circuit that converts the frequency of the signal into a voltage signal. Ru.

[0005] 6 is a target speed setting circuit, and this circuit is a target speed setting circuit that provides the target rotational speed of the engine. Outputs setting signal Vno.

[0006] 7 is an arithmetic circuit, and this arithmetic circuit consists of a comparator 8 and an integrating circuit 9. ratio The comparator 8 compares the speed detection signal Vn and the target speed setting signal Vno to determine the speed detection signal. When the signal exceeds the target speed setting signal, the output stage is turned on and the low level (ground level) output. In addition, the comparator 8 determines that the speed detection signal is the target speed. When the signal is below the set level, the output stage turns off and outputs a high level. occurs. The integrating circuit 9 consists of a resistor R1 and an integrating capacitor C1, and has a ratio of During the period when the comparator 8 is producing a high level output, the integrating capacitor C is connected through the resistor R1. 1 at a constant time constant. This creates a velocity voltage across the integrating capacitor C1. When the detection signal is lower than the target speed setting signal, it rises at a predetermined slope, and the speed detection signal The integral voltage Vi that decreases at a predetermined slope when the signal exceeds the target speed setting signal is can get.

[0007] 10 is an operational amplifier OP1, a capacitor C2, a resistor R2 to R5, and a diode. This oscillator (known astable multivibrator) consists of A sawtooth wave signal Vc is generated.

[0008] 11 is a pulse modulation circuit consisting of a comparator CP1, and the non-inverting input terminal of the comparator CP1 The integral voltage V obtained across the integrating capacitor C1 at the output and inverting input terminals, respectively. i and sawtooth signal voltage Vc are input. The comparator CP1 has an integrated voltage Vi Generates a pulse signal Va that is at a high level while exceeding the sawtooth signal voltage Vc. do. This pulse signal Va is input to the actuator drive circuit 12.

[0009] The actuator drive circuit 12 is a transistor that is turned on and off by a pulse signal Va. The period when the pulse signal Va is at a high level is equipped with a switching element such as a star. A drive current is supplied to the actuator 3 during the period.

0010 In the above control device, the output of the comparator CP1 of the pulse width modulation circuit 11 is integrated. Since the voltage Vi is at a high level only during the period when it exceeds the sawtooth signal voltage Vc, the ratio The output side of the comparator CP1 receives a pulse signal Va whose pulse width is modulated by the integral voltage Vi. is obtained. The actuator drive circuit 12 receives the pulse signal Va at a high level. The drive current I is applied to the actuator 3 during the period Ton. Actuator 3 is While the dynamic current I is applied, the fuel supply amount adjustment means is operated to increase the amount of fuel to the engine. increase the amount of fuel supplied. The fuel supply amount is determined by the drive current I( The average value increases or decreases as shown in FIG. 3(B).

[0011] In the above control device, the engine rotational speed is lower than the target speed (Vn <Vno ), since the integrated voltage Vi obtained from the integrator 9 increases, the comparator C The pulse width of the pulse obtained from P1 becomes wider. This allows the actuator to The drive current supplied to the engine 3 increases, and the amount of fuel supplied to the engine increases. to this The rotational speed of the engine approaches the target speed.

0012 Since the engine rotation speed fluctuates, the engine rotation speed may be around the target rotation speed. When the output stage of the comparator 8 is repeatedly turned on and off, its output level becomes low level. It moves up and down between low and high level states. At this time, both ends of the integrating capacitor C1 The obtained integrated voltage Vi becomes approximately constant.

[0013] Also, when the engine speed is higher than the target speed, the integral obtained from the integrator 9 As the divided voltage Vi decreases, the pulse width of the pulse obtained from the comparator CP1 becomes It's getting narrower. This reduces the amount of fuel supplied to the engine and reduces the rotational speed to the target speed. It is returned to the degree side.

[0014] The signal waveforms shown in FIGS. 2(A) to 2(C) are calculated by the above control device. The circuit 7 and the oscillator 10 are powered by a single power supply (only the + side or - side with respect to the earth level). The horizontal axis in the figure is time and the vertical axis is voltage. . FIG. 2(A) shows the speed detection signal Vn input to the calculation circuit 7 and the target speed setting signal. This shows the relationship with Vno. In this example, the target speed setting signal Vno is at a constant level. Consists of DC voltage. Figure 2(B) shows the waveform of the integrated voltage Vi and the sawtooth wave signal. The waveform of the voltage Vc is shown, and the sawtooth signal voltage Vc is connected to the ground level GND. varies between the lowest level VcL, which is higher than the supply voltage, and the highest level VcH, which is lower than the power supply voltage. Ru.

[0015] Here, if the resistance values of resistors R2 to R4 are expressed by the symbols indicating their respective resistances, The maximum amplitude value VcH of the sawtooth signal voltage Vc is: VcH = Vcc {R3 / (R2 + R3)} ... (1) Also, if the voltage drop across the diode D1 is ignored, the amplitude of the sawtooth signal voltage Vc is The minimum value VcL of VcL=(A/B)Vcc...(2) however, A=(R3 R4)/(R3 +R4)...(3) B=R2 +(R3 R4)/(R3 +R4)...(4) Generally, the input signal of operational amplifier OP1 is set within the driving voltage of the operational element. , the oscillation condition is 0<VcL<VcH<Vcc. Therefore, the sawtooth signal voltage Vc is The waveform oscillates between VcL and VcH.

[0016] On the other hand, when Vn > Vno, the integrated voltage Vi decreases at a constant slope, and Vn > If the state of Vno continues for a long time, Vi approaches 0. Also, when Vn < Vno, the integral When the voltage Vi increases at a predetermined slope and the state of Vn < Vno continues for a long time, the voltage Vi increases. approaches the source voltage Vcc. Therefore, the integrated voltage Vi is the difference between the power supply voltage Vcc and the ground potential 0V. change between

[0017] Figure 2(C) shows the pulse signal obtained from the comparator CP1 that constitutes the pulse width modulation circuit. This shows the waveform of No. Va when the speed detection signal Vn is higher than the target speed setting signal Vno. When the speed is low, the pulse width of the pulse signal Va becomes wide, and the speed detection signal Vn reaches the target speed. When the pulse width is higher than the temperature setting signal Vno, the pulse width of the pulse signal Va becomes narrower.

[0018]

[Problem that the idea aims to solve]

In the control device shown in FIG. 4, the integral voltage Vi is the maximum of the sawtooth signal voltage Vc. When the integrated voltage Vi is between the large value VcH and the power supply voltage Vcc, and the sawtooth signal voltage The output of comparator CP1 does not change when the voltage Vc is between the minimum value VcL and 0V. As a result, a dead band occurs in the control, slowing down the control response and increasing overshoot. There was a problem that

[0019] The purpose of this invention is to prevent dead zones from occurring in control and improve control characteristics. An object of the present invention is to provide a rotational speed control device for an internal combustion engine that is capable of controlling the rotational speed of an internal combustion engine.

[0020]

[Means to solve the problem]

The present invention provides a fuel supply amount adjusting means for adjusting the amount of fuel supplied to an internal combustion engine, and a fuel supply amount adjusting means for adjusting the amount of fuel supplied to an internal combustion engine. An actuator that operates the supply amount adjustment means and an actuator that detects the rotational speed of the internal combustion engine and controls the speed. A rotation speed detection circuit that outputs a speed detection signal and a speed setting circuit that provides a target speed of the internal combustion engine. A target speed setting circuit that outputs a constant signal and compares the speed detection signal and target speed setting signal. Outputs an integral command signal when the speed detection signal exceeds the target speed setting signal. When the comparator is outputting an integration command signal, the integration capacitor is An integrator circuit that charges with a constant time constant and a minimum level above ground level and supply voltage an oscillator that generates a sawtooth signal voltage that varies between a maximum level less than Integrate by comparing the integrated voltage obtained across the integrating capacitor with the sawtooth signal voltage. Generates a pulse signal that is at a high level while the voltage exceeds the sawtooth signal voltage A pulse width modulation circuit and a pulse signal obtained from the pulse width modulation circuit are used as input. An actuator that applies drive current to the actuator while the pulse signal is at a high level. The present invention relates to a rotational speed control device for an internal combustion engine, which is equipped with a rotor drive circuit. In the present invention, the highest level and lowest level of the integrated voltage are set to sawtooth waves, respectively. A voltage limiting circuit is installed to limit the signal voltage below the highest level and above the lowest level. .

[0021]

[Effect]

Configured as above, the integrated voltage is always within the amplitude of the sawtooth signal voltage. Since the control can be varied, it is possible to prevent dead zones from occurring in the control. can speed up the response.

[0022]

【Example】

Figure 1 shows the configuration of an embodiment of the present invention, which is equivalent to each part in Figure 4. The same parts are given the same reference numerals. In this invention, the integral voltage Vi The highest level and lowest level of ' are respectively the highest level V of the sawtooth signal voltage Vc. Voltage limiting circuits 13 and 14 are provided to limit the voltage to below chH and above the lowest level VcL. The voltage limiting circuit 13 includes an operational amplifier OP2, a diode D2, and a diode D2. , resistors R6 and R7, and its output terminal (diode The anode of D2 is connected to the non-grounded terminal of the integrating capacitor C1. this In the voltage limiting circuit, the voltage across the integrating capacitor C1 is equal to the voltage across the resistor R7. When the voltage is lower than the voltage, the output stage of the operational amplifier OP2 is in the off state, so the No current flows through the ode D2, and the voltage limiting circuit 13 ´ will not be affected. The voltage across the integrating capacitor C1 is the voltage across the resistor R7. When the voltage exceeds the terminal voltage, the output stage of operational amplifier OP2 turns on, so the capacitor The charging current of sensor C1 is sucked into the output stage of the operational amplifier through diode D2, The voltage across capacitor C1 is prevented from rising. As a result, the integrated voltage Vi' becomes The voltage across the resistor R7 should be less than or equal to [clamp voltage = {R7 / (R6 + R7)}Vcc] limited.

[0023] The voltage limiting circuit 14 includes an operational amplifier OP3, a diode D3, and resistors R8 and R9. The output terminal (cathode of diode D3) is the integrating capacitor C1. connected to the non-grounded terminal of the In this voltage limiting circuit, the integrating capacitor When the voltage across C1 is higher than the voltage across resistor R9, operational amplifier OP3 Since the output stage of is in the on state, the integration capacitor C1 side is Therefore, the voltage limiting circuit 14 does not affect the integrated voltage. stomach. When the voltage across the integrating capacitor becomes lower than the voltage across resistor R9, the Since the output stage of the operational amplifier OP3 is turned off, the power is connected to the power supply through the diode D3. A charging current flows into the integrating capacitor C1, causing the terminal voltage of the capacitor C1 to drop. prevent. As a result, the integrated voltage Vi' becomes the voltage across the resistor R9 [clamp voltage= {R9 /(R8 +R9)}Vcc].

[0024] The above clamp voltage is {VcH≧R7 /(R6 +R7)}Vcc>{R9 /(R8 +R 9)}Set Vcc≧VcL. R7/(R6 +R7)}Vcc=VcH, {R9/(R 8 +R9)}By setting Vcc=VcL, the integral voltage is Pressure can be varied.

[0025] When the voltage limiting circuits 13 and 14 are provided as described above, as shown by the broken line in FIG. 2(B), As shown above, the integrated voltage Vi' can vary within the amplitude range of the sawtooth signal voltage Vc. It becomes. Therefore, no dead zone occurs in control. Also shown in Figure 2 as a solid line. with an unrestricted integrated voltage Vi and with a limited integrated voltage Vi ′. When compared with the case of Since the integrated voltage V quickly enters the level range compared with the sawtooth signal voltage Vc, It can be seen that the control response is faster in the case of i'.

[0026] As mentioned above, the voltage limiting circuits 13 and 14 are provided to limit the range of change in the integrated voltage. Limiting the amplitude range of the tooth wave signal voltage can eliminate control dead zones. This not only speeds up control response but also reduces overshoot. I can do that.

[0027]

[Effect of the idea]

As described above, according to the present invention, the voltage limiting circuit that limits the variation range of the integrated voltage was set up to vary the integrated voltage within the amplitude range of the sawtooth signal voltage. Therefore, it is possible to eliminate the dead zone of the control, and the response of the control can be made faster. This has the advantage of reducing overshoot.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIGS. 2A to 2C are waveform diagrams showing signal voltage waveforms at various parts in the embodiment of the present invention and the conventional example;

FIG. 3(A) is a diagram showing an example of characteristics of a speed detection circuit used in a rotational speed control device according to the present invention. (B)
1 is a diagram showing an example of the relationship between drive current and fuel supply amount in the rotational speed control device according to the present invention.

FIG. 4 is a circuit diagram showing a conventional rotation speed control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Fuel supply amount adjustment means, 3... Actuator, 5... Speed detection circuit, 6... Target speed setting circuit, 7
... Arithmetic circuit, 8... Comparator, 9... Integrating circuit, 10... Oscillator, 11... Pulse width modulation circuit, 12... Actuator drive circuit.

Claims (1)

[Scope of utility model registration request] 1. Fuel supply amount adjusting means for adjusting the amount of fuel supplied to the internal combustion engine, an actuator for operating the fuel supply amount adjusting means, and detecting the rotational speed of the internal combustion engine and outputting a speed detection signal. a rotational speed detection circuit; a target speed setting circuit that outputs a speed setting signal giving a target speed of the internal combustion engine; and a target speed setting circuit that compares the speed detection signal and the target speed setting signal and determines that the speed detection signal exceeds the target speed setting signal. a comparator that outputs an integration command signal when the comparator is outputting an integration command signal, an integration circuit that charges an integration capacitor with a constant time constant when the comparator is outputting an integration command signal, and a minimum level higher than the ground level and a power supply. an oscillator that generates a sawtooth signal voltage that varies between a maximum level lower than the voltage; and a comparison between the integrated voltage obtained across the integrating capacitor and the sawtooth signal voltage to determine whether the integrated voltage is a sawtooth waveform. a pulse width modulation circuit that generates a pulse signal that is at a high level while exceeding the signal voltage; and a pulse width modulation circuit that receives the pulse signal obtained from the pulse width modulation circuit and drives the actuator during a period when the pulse signal is at a high level. A rotation speed control device for an internal combustion engine, comprising an actuator drive circuit that allows current to flow, and a voltage limiting circuit that limits the maximum level and minimum level of the integrated voltage to below the maximum level and above the minimum level of the sawtooth signal voltage, respectively. A rotation speed control device for an internal combustion engine, characterized in that it is provided with: