JP5173864B2 - Proportional valve drive - Google Patents

Description

  The present invention relates to a proportional valve drive device that controls the amount of current supplied to a proportional valve by PWM (Pulse Width Modulation) control.

  2. Description of the Related Art Conventionally, for example, a proportional valve drive device that is provided in a fuel gas supply pipe and adjusts the gas supply flow rate has a function of detecting an abnormality of the proportional valve (for example, Patent Document 1). reference).

  In the proportional valve driving device described in Patent Document 1, a proportional valve, a transistor, and a current detection resistor are connected in series between output terminals of a power source, and the voltage across the terminals of the current detection resistor is reduced. Based on this, the current flowing through the proportional valve is detected. The base current of the transistor is controlled so that the detected current value matches the target current value set corresponding to the opening of the proportional valve.

  Then, when the difference between the target current value and the detected current value is out of the range from the preset lower limit value to the upper limit value, it is determined that the proportional valve or the transistor has failed, and the gas supply The safety valve of the pipe is closed.

JP 2000-65348 A

  In the conventional proportional valve driving device described above, if the resistance of the proportional valve decreases due to deterioration over time or the like, an excessive pulse current flows through the current detection resistor when the transistor is turned on, and the current detection resistor generates heat. Increase. In this way, when the heat generation of the current detection resistor increases, potting melting or the like occurs, and the circuit board on which the current detection resistor is mounted may break down.

  Therefore, the present invention provides a proportional valve that prevents the heat generation of the current detection resistor from becoming excessive due to an increase in the amount of current supplied to the current detection resistor when the resistance of the proportional valve becomes low due to deterioration over time or the like. An object of the present invention is to provide a driving apparatus.

  The present invention has been made to achieve the above object, and is based on a switching element and a current detection resistor connected in series with a proportional valve between output terminals of a power supply, and a voltage drop in the current detection resistor. The current detection means for detecting the current flowing through the proportional valve, the current value detected by the current detection means, and the target current value set according to the target opening of the proportional valve are matched. Further, the present invention relates to a proportional valve drive device comprising energization control means for controlling the energization amount of the proportional valve by turning on and off the switching element by PWM control.

  In the first aspect of the present invention, the applied voltage detection means detects the voltage applied to the current detection resistor and the applied voltage detection when the switching element is turned on by the energization control means. The voltage detected by the means is higher than a first determination voltage that is a voltage applied to the current detection resistor when the resistance value of the proportional valve is at a predetermined abnormality determination level and the switching element is ON. And a proportional valve energization shut-off means for interrupting energization from the power source to the proportional valve.

  According to the present invention, when the resistance value of the proportional valve falls below the abnormality determination level due to the failure of the proportional valve, the voltage applied to the current detection resistor increases when the switching element is turned on. Higher than the first determination voltage. Therefore, the proportional valve energization cutoff means is configured such that when the switching element is ON, the applied voltage to the current detection resistor detected by the applied voltage detection means is higher than the first determination voltage. When the power is lost, the power supply from the power source to the proportional valve is cut off. As a result, when the resistance value of the proportional valve becomes low due to a failure or the like and the amount of current supplied to the current detection resistor increases, the current detection resistance is immediately stopped and the current detection is stopped. It is possible to prevent the heat generated by the resistor from becoming excessive.

  Next, according to a second aspect of the present invention, the voltage applied to the current detection resistor is the current when the resistance value of the proportional valve is a predetermined abnormality determination level and the switching element is ON. When the voltage is higher than the first determination voltage that is a voltage applied to the detection resistor, the first voltage is output. When the voltage applied to the current detection resistor is equal to or lower than the first determination voltage, the first voltage is output. When the PWM control is performed by the comparison circuit that outputs the second voltage of a level different from the voltage, the smoothing circuit that smoothes and outputs the output voltage of the comparison circuit, and the smoothing circuit that performs the PWM control, When the output voltage of the circuit falls within the range from the second determination voltage set between the first voltage and the second voltage to the first voltage, the energization from the power source to the proportional valve is cut off. Proportional valve energization shut-off means And said that there were pictures.

  According to the present invention, if the resistance value of the proportional valve is higher than the abnormality determination level, the voltage applied to the current detection resistor when the switching element is turned on is equal to or lower than the first determination voltage. Therefore, the output of the comparison circuit is maintained at the second voltage. Therefore, the output of the smoothing circuit is the second voltage.

  On the other hand, when the resistance value of the proportional valve falls below the abnormality determination level, the voltage applied to the current detection resistor when the switching element is turned on becomes higher than the first determination voltage, and the comparison circuit Is switched from the second voltage to the first voltage. In this case, when the PWM control is performed by the energization control unit, the output of the comparison circuit is switched between the first voltage and the second voltage according to ON / OFF of the switching element. It becomes a state. Therefore, the output of the smoothing circuit is between the first voltage and the second voltage (when the first voltage is higher than the second voltage, it is higher than the second voltage and lower than the first voltage). Range, or when the first voltage is lower than the second voltage, from the second determination voltage set to a range higher than the first voltage and lower than the second voltage) to the first voltage Within the range.

  Therefore, the proportional valve energization cutoff means has an output voltage of the smoothing circuit within a range from the second determination voltage to the first voltage when the PWM control is performed by the energization control means. When the power is lost, the power supply from the power source to the proportional valve is cut off. As a result, when the resistance value of the proportional valve becomes low due to a failure or the like and the amount of current supplied to the current detection resistor increases, the current detection resistance is immediately stopped and the current detection is stopped. It is possible to prevent the heat generated by the resistor from becoming excessive.

The block diagram of the proportional valve drive device of this invention. The timing chart for demonstrating the action | operation of the proportional valve drive device shown in FIG. Explanatory drawing which showed the difference in the applied voltage of the resistance for electric current detection when the proportional valve is normal, and abnormal, and the difference of the output of a comparison circuit and a smoothing circuit.

  Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a proportional valve driving device that is connected to the proportional valve 20 and controls the opening degree of the proportional valve 20. The proportional valve 20 is provided, for example, in a gas supply pipe that supplies fuel gas to a gas burner, and its opening degree is determined in proportion to the magnitude of a current to be energized.

  The proportional valve drive device is an output of a microcomputer 10 (hereinafter referred to as the microcomputer 10) that controls the overall operation of the proportional valve drive device, and a DC 35V power source (corresponding to the power source of the present invention) that is the power source of the proportional valve 20. A transistor 30 (corresponding to a switching element of the present invention) and a current detection resistor 31 connected in series with the proportional valve 20 and a transistor 30, a resistor 33, and a resistor 34 are connected between the terminals V 35 and GND. And an operational amplifier 40 whose output terminal is connected to the transistor 35 via a resistor 36 and a resistor 37.

  A rectangular waveform of a predetermined frequency (for example, 500 Hz) output from the output port PO of the microcomputer 10 is input to the positive input terminal of the operational amplifier 40 after being shaped into a triangular wave by the resistor 42 and the capacitor 43. The output port PO is pulled up to 5 VDC by a resistor 41.

  Further, the DA output (digital / analog conversion output) port DA of the microcomputer 10 outputs a voltage at a level set in accordance with a target current value corresponding to the target opening of the proportional valve 20, and this voltage is resistance. The voltage Vc divided by 52 and 53 is input to the positive input terminal of the operational amplifier 50.

  The negative input terminal of the operational amplifier 50 is connected to the terminal on the proportional valve 20 side of the current detection resistor 31, and the output terminal of the operational amplifier 50 is connected to the negative input terminal of the operational amplifier 40. Further, a capacitor 51 is connected between the output terminal and the negative input terminal of the operational amplifier 50, and the output terminal of the operational amplifier 50 is connected to GND via a resistor 44.

  A connection point 71 between the proportional valve 20 and the current detection resistor 31 is connected to an AD input (analog / digital conversion input) port AD1 of the microcomputer 10 through an integration circuit including a resistor 54 and a capacitor 55. The input to the AD port AD1 is for detecting an open (disconnection) failure of the proportional valve 20.

  The proportional valve drive device further includes a comparison circuit 90 and a smoothing circuit 91. In the comparison circuit 90, the connection point 71 between the proportional valve 20 and the current detection resistor 31 is connected to GND via the resistor 60 and the resistor 61, and the connection point between the resistor 60 and the resistor 61 functions as a comparator. It is connected to the negative input terminal of the operational amplifier 65. The positive input terminal of the operational amplifier 65 is connected to a connection point of resistors 63 and 64 connected between 5V and GND, and the output terminal of the operational amplifier 65 is connected to the inverting element 66.

  In the smoothing circuit 91, a resistor 80 and a resistor 83 are connected in series between the output terminal of the inverting element 66 and the AD input (analog / digital conversion input) port AD3 of the microcomputer 10, and the connection point between the resistors 80 and 83 and the GND A resistor 81 and a capacitor 82 are connected in parallel.

  The memory 13 of the microcomputer 10 holds data for a control program for the proportional valve 20. When the microcomputer 10 executes the control program, the microcomputer 10 controls the proportional valve control means 11 that controls the energization amount to the proportional valve 20 by PWM (Pulse Width Modulation) control, and the proportional valve control means 11 controls the proportional valve. When the energization amount control for PWM 20 is performed and the voltage input to the AD input port AD3 becomes equal to or higher than the second determination voltage (for example, 1 V), the proportional valve that cuts off the energization to the proportional valve 20 It functions as the applied voltage detecting means 14 for detecting the voltage applied to the power cut-off means 12 and the current detecting resistor 31. The applied voltage detection means 14 is used in a second embodiment to be described later.

  Next, the operation of the proportional valve driving device shown in FIG. 1 will be described according to the timing chart shown in FIG.

  2 shows, in order from the top, (a) voltage Va at the output port PO of the microcomputer 10, (b) voltage Vb at the positive input terminal of the operational amplifier 40, (c) voltage Vc at the positive input terminal of the operational amplifier 50, (d). It shows changes in the voltage Vd at the negative input terminal of the operational amplifier 50, (e) the voltage Vf at the negative input terminal of the operational amplifier 40, and (f) the voltage Ve at the output terminal of the operational amplifier 40.

  The proportional valve control means 11 outputs a rectangular wave voltage Va having a frequency of 500 Hz from the output port PO of the microcomputer 10 as shown in FIG. Then, the rectangular wave voltage Va is shaped into a triangular wave voltage Vb by an integrating circuit made up of a resistor 42 and a capacitor 43 and input to the positive input terminal of the operational amplifier 40 as shown in FIG.

  The proportional valve control means 11 sets the target opening of the proportional valve 20 according to the target combustion amount of the burner connected to the fuel gas supply pipe provided with the proportional valve 20, for example. And the proportional valve control means 11 sets the level of the voltage output from DA output port DA so that the energization amount corresponding to the target opening degree can be obtained.

  The voltage output from the DA conversion port DA is divided by the voltage dividing resistors 52 and 53 and is set to the target voltage Vc and input to the positive input terminal of the operational amplifier 50 as shown in FIG. .

  A voltage (monitor voltage) applied to the current detection resistor 31 is input to the negative input terminal of the operational amplifier 50 via the resistor 56. Here, the voltage applied to the current detection resistor 31 increases or decreases in proportion to the magnitude of the current flowing through the transistor 30, the proportional valve 20, and the current detection resistor 31. Then, as shown in FIG. 2E, the operational amplifier 50 converts the voltage Vf obtained by amplifying the difference between the target voltage Vc inputted to the positive input terminal and the monitor voltage Vd inputted to the negative input terminal to the operational amplifier. Output to 40 negative input terminals.

  The operational amplifier 40 functions as a comparator. As shown in FIG. 2F, the operational amplifier 40 has a high level (12) during which the triangular wave voltage Vb input to the positive input terminal exceeds the voltage Vf input to the negative input terminal. .6V), a rectangular wave voltage Ve having a low level (0V) during which the triangular wave signal Vb is equal to or lower than the voltage Vf input to the negative input terminal is output to the base of the transistor 35. As a result, PWM control is executed to change the duty of the rectangular wave voltage Ve output to the base of the transistor 35 so as to reduce the difference between the target voltage Vc and the monitor voltage Vd.

  When the rectangular wave voltage Ve output from the operational amplifier 40 to the base of the transistor 35 is at a high level, the transistor 35 and the transistor 30 are turned on. When the rectangular wave voltage Ve is at a low level, the transistor 35 and The transistor 30 is turned off.

  In this way, the configuration in which the proportional valve control means 11 uses the operational amplifiers 40 and 50 to turn on / off the transistor 35 by PWM control so as to reduce the difference between the target voltage Vc and the monitor voltage Vd. This corresponds to the energization control means of the present invention.

  The applied voltage detecting means 14 detects the voltage Vi applied to the current detection resistor 31 from the digital conversion value of the voltage Vi input to the AD (analog / digital conversion) input port AD2.

  Next, the first embodiment and the second embodiment of the process of cutting off the power supply to the proportional valve 20 by the proportional valve power supply cutoff means 12 will be described with reference to FIG.

  [First Embodiment] FIG. 3 shows the voltage Vi applied to the current detection resistor 31 and the comparison circuit 90 when the proportional valve control means 11 controls the energization amount of the proportional valve by the PWM control described above. The change in the output voltage Vj and the output voltage Vk of the smoothing circuit 91 input to the input port PI of the microcomputer 10 is shown with the vertical axis set to voltage (V) and the horizontal axis set to time (t). It is a thing.

  Then, in order from the top, (g) when the resistance value of the proportional valve 20 is 80Ω (normal), the voltage Vi applied to the current detection resistor 31, and (h) the resistance value of the proportional valve 20 is 80Ω ( The output voltage Vj of the comparison circuit 90 and the output voltage Vk of the smoothing circuit 91 at the time of normal) are shown.

  Further, (i) the voltage Vi applied to the current detection resistor 31 when the resistance value of the proportional valve 20 is 40Ω (when abnormal), (j) the resistance value of the proportional valve 20 is 40Ω (when abnormal). The output voltage Vj of the comparison circuit 90 and the output voltage Vk of the smoothing circuit 91 at a certain time are shown.

  First, when the resistance value of the proportional valve 20 is 80Ω (normal), the peak value of the voltage Vi applied to the current detection resistor 31 is about 4V as shown in (g). The voltage Vm input to the positive input terminal of the operational amplifier 65 is the voltage Vn input to the negative input terminal of the operational amplifier 65 when Vi is 5 V or higher (corresponding to the first determination voltage of the present invention). It is set to be higher than Vm.

  Therefore, when the voltage Vi applied to the current detection resistor 31 is 5 V or more, the output voltage of the operational amplifier 65 is 0 V, and the output voltage Vj of the comparison circuit 90 is 5 V (corresponding to the first voltage of the present invention). ) When the voltage Vi applied to the current detection resistor 31 is lower than 5V, the output voltage of the operational amplifier 65 is 5V and the output voltage Vj of the comparison circuit 90 is 0V (corresponding to the second voltage of the present invention). .

  In this case, as shown in (h), since the output voltage Vj of the comparison circuit 90 is maintained at 0V, the output voltage Vk of the smoothing circuit 91 is also 0V. Therefore, the voltage input to the AD input port AD3 of the microcomputer 10 is 0V.

  On the other hand, when the resistance value of the proportional valve 20 is 40Ω (at the time of abnormality), as shown in (i), when the PWM control is performed, the peak value of the voltage Vi applied to the current detection resistor 31 is It becomes about 7V and becomes 5V or more. Therefore, when the transistor 30 is turned on, the voltage Vn input to the negative input terminal of the operational amplifier 65 becomes higher than the voltage Vm input to the positive input terminal, and the output voltage Vj of the comparison circuit 90 becomes 5V.

  In this case, as shown in (j), the output voltage Vj of the comparison circuit 90 is switched between 5V and 0V according to ON / OFF of the transistor 30 by PWM control. Therefore, the output voltage Vk of the smoothing circuit 91 is about 4V as shown in (k), and the voltage input to the AD input port AD3 of the microcomputer 10 is about 4V.

  As described above, when the resistance value of the proportional valve 20 is 80Ω (normal), the voltage Vk input to the AD input port AD3 of the microcomputer 20 is 0V. Further, when the resistance value of the proportional valve 20 is 40Ω (at the time of abnormality), the voltage input to the AD input port AD3 of the microcomputer 20 is about 4V.

  Accordingly, the proportional valve energization cutoff means 12 monitors the level of the voltage Vk input to the AD input port AD3 when the energization amount of the proportional valve 20 is controlled by PWM control, and is input to the AD input port AD3. Output voltage PO when the output voltage Vk is equal to or higher than 1 V (corresponding to the second determination voltage of the present invention) (corresponding to the range from the second determination voltage of the present invention to the first voltage). The output of the rectangular wave voltage from is stopped.

  When the output of the rectangular wave voltage from the output port PO is stopped, the output from the operational amplifier 40 to the base of the transistor 35 becomes 0 V, the transistors 35 and 30 are turned off, and the proportional valve 20 and the current detection resistor are turned off from the DC 35 V power source. The energization to 31 is cut off.

  In the case of the first embodiment, the proportional valve energization interrupting means 12 may determine whether or not the voltage Vk input to the AD input port AD3 is 1V or higher. Therefore, the voltage applied to the current detection resistor 31 by the applied voltage detection means 14 after confirming that the energization amount of the proportional valve 20 is controlled by PWM control as in the second embodiment described later. There is no need to perform a process of detecting Vi and determining whether or not the peak value of Vi is equal to or greater than a threshold value. Therefore, the processing in the proportional valve energization cutoff means 12 is simpler than in the case of the second embodiment, and the calculation load of the microcomputer 10 can be reduced.

  [Second Embodiment] Referring to FIG. 3, when the resistance value of proportional valve 20 is 80Ω (normal), when the energization amount of proportional valve 20 is controlled by PWM control, As shown, the peak value of the voltage Vi applied to the current detection resistor 31 is about 4V. On the other hand, when the resistance value of the proportional valve 20 is 40Ω (at the time of abnormality), when the energization amount of the proportional valve 20 is controlled by PWM control, it is applied to the current detection resistor 31 as shown in (i). The peak value of the voltage Vi is about 7V.

  Therefore, the voltage Vi applied to the current detection resistor 31 is input to the AD conversion port AD2 of the microcomputer 20, Vi is detected by the applied voltage detection means 14, and the energization amount of the proportional valve 20 is controlled by PWM control. When detected, Vi detected by the applied voltage detection means 14 is monitored by the proportional valve energization cutoff means 12.

  Then, the proportional valve energization shut-off means 12 detects the rectangular wave signal from the output port PO when Vi detected by the applied voltage detection means 14 becomes 5 V (corresponding to the first determination voltage of the present invention) or more. Stop output.

  When the output of the rectangular wave signal from the output port PO is stopped, the output from the operational amplifier 40 to the base of the transistor 35 becomes 0 V, the transistors 35 and 30 are turned off, and the proportional valve 20 and the current detection resistor are supplied from the DC 35 V power source. The energization to 31 is cut off. In the case of the second embodiment, the comparison circuit 90 and the smoothing circuit 91 are not necessary.

  According to the first embodiment or the second embodiment described above, when the resistance value of the proportional valve 20 is reduced by the proportional valve energization cutoff means 12, the transistor 30 is turned off, and the proportional valve 20 and the current detection By shutting off the power supply to the resistor 31, it is possible to prevent the substrate from being damaged due to excessive heat generation in the current detection resistor 31 due to an increase in the peak current flowing through the current detection resistor 31.

  In this embodiment, in the second embodiment, when the voltage applied to the current detection resistor 31 is higher than 5 V (the first determination voltage of the present invention), the output voltage Vj of the comparison circuit 90 is When the voltage applied to the current detection resistor 31 is 5 V or less, the output voltage Vj of the comparison circuit 90 is set to 0 V (second voltage of the present invention).

  Note that when the voltage applied to the current detection resistor 31 is higher than 5 V (first determination voltage of the present invention), the output voltage Vj of the comparison circuit 90 is 0 V (first of the present invention). When the voltage applied to the current detection resistor 31 is 5 V or less, the setting is such that the output voltage Vj of the comparison circuit 90 is 5 V (second voltage of the present invention) (first voltage <second voltage). Also good. In this case, when the output voltage Vk of the smoothing circuit 91 becomes, for example, 4 V (corresponding to the second determination voltage of the present invention) or less, the proportional valve energization cutoff means 12 receives the rectangular wave signal from the output port PO. The output may be stopped and the transistors 35 and 30 may be turned off.

  DESCRIPTION OF SYMBOLS 10 ... Microcomputer, 11 ... Proportional valve control means, 12 ... Proportional valve electricity interruption means, 13 ... Memory, 14 ... Applied voltage detection means, 20 ... Proportional valve, 30 ... Transistor (switching element of this invention), 31 ... Current Detection resistor, 90 ... comparison circuit, 91 ... smoothing circuit

Claims (2)

Between the output terminals of the power source, a switching element and a current detection resistor connected in series with the proportional valve,
Current detection means for detecting a current flowing through the proportional valve based on a voltage drop in the current detection resistor;
The switching element is turned on / off by PWM control so that the current value detected by the current detection means matches the target current value set according to the target opening of the proportional valve, and the proportional In a proportional valve drive device comprising an energization control means for controlling the energization amount of the valve,
Applied voltage detecting means for detecting a voltage applied to the current detecting resistor;
When the switching element is turned on by the energization control means, the detected voltage by the applied voltage detection means is when the resistance value of the proportional valve is a predetermined abnormality determination level and the switching element is ON. Proportional valve energization cutoff means for interrupting energization from the power source to the proportional valve when the voltage becomes higher than a first determination voltage that is a voltage applied to the current detection resistor. Valve drive device. Between the output terminals of the power source, a switching element and a current detection resistor connected in series with the proportional valve,
Current detection means for detecting a current flowing through the proportional valve based on a voltage drop in the current detection resistor;
The switching element is turned on / off by PWM control so that the current value detected by the current detection means matches the target current value set according to the target opening of the proportional valve, and the proportional In a proportional valve drive device comprising an energization control means for controlling the energization amount of the valve,
The voltage applied to the current detection resistor is a voltage applied to the current detection resistor when the resistance value of the proportional valve is at a predetermined abnormality determination level and the switching element is ON. When the voltage is higher than the determination voltage, the first voltage is output. When the voltage applied to the current detection resistor is equal to or lower than the first determination voltage, the second voltage having a level different from the first voltage is output. A comparison circuit;
A smoothing circuit that smoothes and outputs the output voltage of the comparison circuit;
When the PWM control is performed by the energization control means, the output voltage of the smoothing circuit is from a second determination voltage set between the first voltage and the second voltage to the first voltage. A proportional valve drive device comprising: a proportional valve energization shut-off means for interrupting energization from the power source to the proportional valve when within the range.

Images