JP6455044B2 - Combustion device - Google Patents

Description

  The present invention relates to combustion devices, and more particularly to control of equipment for regulating fuel supply.

  In a combustion apparatus that generates combustion heat by fuel combustion, it is important to control the fuel supply amount according to the command in order to maintain a good combustion state. Typically, the fuel supply amount is controlled by an adjustment valve (proportional valve) whose opening is adjusted according to the drive current.

  In Japanese Patent No. 3646367 (Patent Document 1), when adjusting the drive current of the regulating valve to an opening degree corresponding to the required amount of heat, the reference value of the drive current that should flow and the detected value of the actual drive current There is described a control for determining an abnormality and stopping combustion when the current difference between is large.

  Japanese Patent Application Laid-Open No. 11-118141 (Patent Document 2) discloses a proportional valve drive current in accordance with a detected value of the secondary pressure in order to suppress a change in fuel supply pressure due to a temperature change of the proportional valve. The control to be adjusted is described.

Japanese Patent No. 3646367 Japanese Patent Laid-Open No. 11-118141

  As described in Patent Documents 1 and 2, a regulating valve (proportional valve), which is a representative example of a device for regulating fuel supply, is controlled by an output from a control device configured by a microcomputer. Since the opening degree of the regulating valve (proportional valve) is controlled by the drive current, there is a concern that if the drive current has an error in response to a command from the microcomputer, the combustion state will deteriorate due to fluctuations in the fuel supply amount. The

  The present invention has been made to solve such problems, and an object of the present invention is to maintain the combustion state of the combustion apparatus satisfactorily by controlling accurately in accordance with instructions from the microcomputer. That is.

  In one aspect of the present invention, a combustion apparatus includes a combustion mechanism, a control device, first and second ground wirings for supplying a common ground voltage, and a drive circuit. The combustion mechanism is configured to generate heat by fuel combustion. The control device is configured to control the fuel supply amount in accordance with the operation amount that changes in accordance with the drive current. The first and second ground wirings are electrically connected via a node connected to the smoothing capacitor. The microcomputer is configured to control the operation amount of the control device. The drive circuit adjusts the drive current of the control device in accordance with a control command voltage from the microcomputer. The microcomputer is grounded by the first ground wiring, and the drive circuit is grounded by the second ground wiring. The drive circuit is configured to control the drive current according to a voltage difference between the control command voltage and the second ground wiring. The microcomputer receives a voltage that varies depending on the voltage difference between the first and second ground wirings and corrects the control command voltage based on the input voltage.

  According to the above combustion apparatus, even if the ground voltage (second ground wiring) of the drive circuit fluctuates, the micro device is based on the voltage that changes depending on the voltage difference between the first and second ground wirings. The control command voltage from the computer to the drive circuit can be corrected. Therefore, by preventing fluctuations in the drive current due to the influence of ground voltage fluctuations, the fuel supply amount in the combustion apparatus can be accurately controlled in accordance with a command from the microcomputer. As a result, the combustion state of the combustion device can be maintained satisfactorily.

  Preferably, the combustion apparatus further includes a voltage detection circuit. The voltage detection circuit is configured to output a voltage obtained by amplifying the voltage difference between the first and second ground wirings. The microcomputer uses the output voltage of the voltage detection circuit as an input voltage and corrects the control command voltage according to the voltage difference between the first and second ground wirings.

In this way, by inputting the voltage obtained by amplifying the voltage difference between the first and second ground wirings to the microcomputer, the voltage difference between the first and second ground wirings due to the voltage fluctuation of the second ground wiring is reduced. Can be detected. Therefore, the control command voltage from the microcomputer to the drive circuit can be corrected according to the voltage difference between the first and second ground wirings. Preferably, the combustion apparatus further includes a voltage detection circuit. The drive circuit has a resistance element through which a drive current passes. The voltage detection circuit is configured to detect a voltage drop amount in the resistance element. The microcomputer uses the output voltage of the voltage detection circuit as an input voltage and sets the control command voltage according to the voltage difference between the voltage drop reference value corresponding to the control command voltage and the voltage drop detected by the voltage detection circuit. to correct.

  In this way, by inputting the voltage drop amount of the resistance element through which the drive current in the drive circuit passes to the microcomputer, the voltage difference between the first and second ground wirings due to the voltage fluctuation of the second ground wiring is obtained. Can be detected. Therefore, the control command voltage from the microcomputer to the drive circuit can be corrected according to the voltage difference between the first and second ground wirings.

Preferably, the control device includes a proportional valve whose opening degree changes according to the drive current.
In this way, the opening degree of the proportional valve for controlling the amount of fuel supplied to the combustion mechanism can be accurately controlled in accordance with a command from the microcomputer, eliminating the influence of fluctuations in ground voltage.

  According to the present invention, the combustion state of the combustion device can be favorably maintained by accurately controlling the device for adjusting the fuel supply in accordance with a command from the microcomputer.

It is a schematic block diagram of the hot-water supply apparatus with which the combustion apparatus according to embodiment of this invention was applied. It is a block diagram for demonstrating the power supply structure of the hot water supply apparatus with which the combustion apparatus which concerns on this Embodiment was applied. It is a circuit diagram explaining the structure for controlling the opening degree of the gas proportional valve shown by FIG. It is a conceptual diagram for demonstrating the fluctuation | variation of the drive current by the drive circuit shown by FIG. It is a block diagram for demonstrating the opening degree control of the gas proportional valve according to Embodiment 1. 5 is a flowchart illustrating opening control of a gas proportional valve according to the first embodiment. FIG. 6 is a block diagram for illustrating opening control of a gas proportional valve according to a second embodiment. 6 is a flowchart for illustrating opening control of a gas proportional valve according to a second embodiment.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a hot water supply apparatus to which a combustion apparatus according to an embodiment of the present invention is applied.

  Referring to FIG. 1, hot water supply apparatus 10 includes a water inlet pipe 20, a hot water outlet pipe 30, a heat exchanger 40, a combustion burner 50, and a microcomputer 100. Furthermore, the hot water supply apparatus 10 includes a gas supply pipe 55, a gas electromagnetic valve 60, and a gas proportional valve 70 for supplying fuel gas to the combustion burner 50.

  The inlet pipe 20 is supplied with non-heated water such as tap water. The heat exchanger 40 heats the non-heated water from the inlet pipe 20 by heat exchange by the combustion heat of the fuel gas by the combustion burner 50. Heated water from the heat exchanger 40 is discharged from the outlet pipe 30.

  A gas solenoid valve 60 and a gas proportional valve 70 are inserted in the gas supply pipe 55 to the combustion burner 50. The fuel gas output from the combustion burner 50 is mixed with combustion air introduced by a combustion fan (not shown) and ignited by an ignition device (not shown). When the air-fuel mixture is ignited, a flame in which the fuel gas is burned is generated. The combustion heat generated by the flame from the combustion burner 50 is given to the heat exchanger 40.

  The gas solenoid valve 60 is opened and closed in accordance with a control command from the microcomputer 100. The gas solenoid valve 60 has a function of turning on / off the supply of fuel gas to the combustion burner 50. The opening degree of the gas proportional valve 70 is controlled according to a control command from the microcomputer 100.

  The supply pressure of fuel gas from the gas supply pipe 55 to the combustion burner 50 (hereinafter also simply referred to as “gas pressure”) is controlled in accordance with the opening of the gas proportional valve 70. Therefore, the fuel gas supply amount from the combustion burner 50 (strictly speaking, the supply amount per unit time, that is, the flow rate) is controlled by the gas proportional valve 70.

  In the configuration shown in FIG. 1, the combustion burner 50, gas supply pipe 55, gas electromagnetic valve 60 and gas proportional valve 70, and microcomputer 100 constitute a combustion apparatus according to the present embodiment. That is, the combustion burner 50 corresponds to one embodiment of the “combustion mechanism”, the gas proportional valve 70 corresponds to one embodiment of the “control device”, and the opening degree of the gas proportional valve 70 is “operation” of the “control device”. Corresponds to “amount”. The configuration for controlling the opening degree of the gas proportional valve 70 will be described in detail later.

  FIG. 2 is a block diagram for explaining a power supply configuration of a hot water supply apparatus to which the combustion apparatus according to the present embodiment is applied.

  Referring to FIG. 2, hot water supply apparatus 10 includes diode bridge 120, smoothing capacitor 130, transistor 140, transformer 150, diode 160, smoothing capacitor 170, power supply wirings 200 and 210, ground wiring 205, 215.

  The diode bridge 120 rectifies the AC voltage from the external power supply 110 electrically connected via an outlet or the like, and outputs the rectified voltage between the power supply wiring 200 and the ground wiring 205. The smoothing capacitor 130 smoothes the voltage rectified by the diode bridge 120. As a result, the smoothing capacitor 130 holds a DC voltage (for example, about 140 V) corresponding to the AC voltage amplitude from the external power supply 110.

  The transistor 140 is periodically turned on / off to convert the DC voltage held in the smoothing capacitor 130 into a pulsed AC voltage. The AC voltage converted by the transistor 140 is applied to the primary winding 152 of the transformer 150.

  An AC voltage having the same frequency as that of the primary winding 152 is output to the secondary winding 155 of the transformer 150, the amplitude of which is converted according to the turn ratio of the primary winding 152 and the secondary winding 155. By transmitting the AC voltage switched by the transistor 140 to the transformer 150, the transformer 150 can be reduced in size.

  The AC voltage output to the secondary winding 155 is converted into a DC voltage Vs between the power supply wiring 210 and the ground wiring 215 by the diode 160 and the smoothing capacitor 170. Hereinafter, the DC voltage Vs is also referred to as “power supply voltage Vs”. Smoothing capacitor 170 is electrically connected between power supply wiring 210 and ground wiring 215. Smoothing capacitor 170 is connected to ground wiring 215 at node Na. By providing the transformer 150, electrical insulation can be ensured between the ground voltage GND # on the primary side of the transformer and the ground voltage GND on the secondary side of the transformer 150.

  The power supply voltage Vs can be controlled by adjusting the effective value of the AC voltage input to the primary winding 152 by the on / off control of the transistor 140. The power supply voltage Vs is controlled to about 15V, for example.

  Between the power supply wiring 210 and the ground wiring 215, a device group that operates upon receiving the supply of the power supply voltage Vs is connected. For example, the gas solenoid valve 60, the gas proportional valve 70, and other loads 90 are connected between the power supply wiring 210 and the ground wiring 215.

  The hot water supply apparatus 10 further includes a voltage regulator 180, a smoothing capacitor 190, a power supply wiring 220, and a ground wiring 225.

  Voltage regulator 180 is connected to power supply wiring 210 and ground wiring 215 and converts DC voltage Vs to DC voltage Vc. The output node of voltage regulator 180 is connected to power supply wiring 220. Smoothing capacitor 190 is electrically connected between power supply wiring 220 and ground wirings 215 and 225. Hereinafter, the DC voltage Vc is also referred to as “power supply voltage Vc”. The power supply voltage Vc is controlled to about 5V, for example.

  The microcomputer 100 shown in FIG. 1 is connected to the power supply wiring 220 and the ground wiring 225, and operates by receiving the supply of the power supply voltage Vc. Here, the ground wirings 215 and 225 are electrically connected via a node Nb electrically connected to the smoothing capacitor 190. That is, the power supply wirings 215 and 225 are arranged to supply the transformer secondary side ground voltage GND.

  When the gas electromagnetic valve 60, the gas proportional valve 70, and the load 90 are operated in the ground wiring 215, there is a concern that the voltage level rises from the original ground voltage GND due to the consumption current of these devices flowing in. On the other hand, the ground line 225 is not connected to a device group with a large current consumption, so that the voltage level fluctuation is smaller than that of the ground line 215.

  Note that the fluctuation of the voltage level in the ground wiring 215 is not directly transmitted to the ground wiring 225 via the node Nb to which the smoothing capacitor 190 is connected. Hereinafter, the voltage of the ground wiring 215 is denoted as GND2, while the voltage of the ground wiring 215 is denoted as GND1. That is, the ground voltage GND2 of the gas proportional valve 70 connected to the ground wiring 215 and the ground voltage GND1 of the microcomputer 100 connected to the ground wiring 225 are distinguished from each other. Normally, GND1 = GND2, but when the ground voltage fluctuation as described above occurs, GND2> GND1.

FIG. 3 is a circuit diagram for explaining a configuration for controlling the opening of the gas proportional valve.
Referring to FIG. 3, drive circuit 300 controls drive current Id of gas proportional valve 70 in accordance with control command voltage Vsv from microcomputer 100. The opening degree of the gas proportional valve 70 changes according to the drive current Id.

  The drive circuit 300 includes an operational amplifier 310, a drive transistor 320, a capacitor C1, and resistance elements R0 to R3. Hereinafter, the electric resistance values of the resistance elements R0 to R3 are also expressed as R0 to R3.

  The drive transistor 320 is connected in series with the gas proportional valve 70 and the resistance element R 0 between the power supply wiring 210 and the ground wiring 215. Resistance element R0 is electrically connected between node Nd and ground wiring 215. The node Nd corresponds to a connection node between the driving transistor 320 and the resistance element R0. In the configuration example of FIG. 3, the drive transistor 320 is configured by an npn transistor. The operational amplifier 310 is connected to the power supply wiring 210 and the ground wiring 215 and operates by receiving the supply of the power supply voltage Vs.

  The control command voltage Vsv is input to the non-inverting input terminal (+ terminal) of the operational amplifier 310 via the resistance element R3. On the other hand, the inverting input terminal (− terminal) of the operational amplifier 310 is connected to the node Nd via the resistance element R2. The capacitor C1 is connected between the non-inverting input terminal (+ terminal) and the inverting input terminal (−terminal) of the operational amplifier 310. The output terminal of the operational amplifier 310 is electrically connected to the control electrode (base) of the driving transistor 320 via the resistance element R1.

  By the feedback from the operational amplifier 310, the supply current from the drive transistor 320, that is, the drive current Id of the gas proportional valve 70 is controlled so that the voltage at the node Nd becomes equal to the control command voltage Vsv. As a result, the drive current Id by the drive circuit 300 is controlled according to the following equation (1).

Id = (Vsv−GND2) / R0 (1)
As described above, the drive circuit 300 is configured to control the drive current Id according to the voltage difference between the control command voltage Vsv and the ground voltage GND2 in accordance with the control command voltage Vsv.

  The microcomputer 100 calculates the opening command value of the gas proportional valve 70 according to the required amount of heat generated in the combustion burner 50, and also generates the control command voltage Vsv for generating the drive current Id corresponding to the opening command value. Is output. For example, if the correspondence between the opening degree (command value) of the gas proportional valve 70 and the drive current Id is determined in advance by a map or an arithmetic expression, the formula (1) can be obtained by referring to the map or the arithmetic expression each time. ), The control command voltage Vsv for combustion control can be calculated.

  As shown in FIG. 3, the microcomputer 100 is grounded by the ground wiring 225, while the drive circuit 300 is grounded by the ground wiring 215. That is, the ground wiring 225 corresponds to the “first ground wiring”, and the ground wiring 215 corresponds to the “second ground wiring”.

  As described in FIG. 2, the ground voltage GND1 (ground wiring 225) of the microcomputer 100 is stable, while the ground voltage GND2 (ground wiring 215) of the drive circuit 300 is caused by the inflow of current consumption of the device group. May rise. As a result, there is a concern that the drive current Id varies.

FIG. 4 is a conceptual diagram for explaining the fluctuation of the drive current accompanying the rise of the ground voltage.
Referring to FIG. 4, GND1 = GND2 at the normal time. At this time, as shown in Equation (1), the drive current Id is proportional to the voltage difference ΔV1 (ΔV1 = Vsv−GND1). In other words, the microcomputer 100 generates the control command voltage Vsv with reference to the voltage difference ΔV1.

  Here, when the ground voltage GND2 of the drive circuit 300 increases by ΔVgnd, the drive current Id becomes proportional to the voltage difference ΔV2 (ΔV2 = ΔV1−ΔVgnd). As a result, the drive current Id varies with respect to the same control command voltage Vsv. Specifically, the drive current Id decreases by ΔVgnd / R0. Due to such fluctuations in the drive current Id, an error occurs in the amount of gas supplied from the combustion burner 50 in response to a command from the microcomputer 100. Due to this influence, there is a concern that the combustion state deteriorates due to the change in the air-fuel ratio between the amount of gas supplied from the combustion burner 50 and the combustion air from the desired value.

  Therefore, in the first embodiment, the opening degree of the gas proportional valve 70 is controlled so as to suppress the fluctuation of the driving current with respect to the fluctuation in the ground voltage of the driving circuit 300.

  FIG. 5 is a block diagram showing a configuration for controlling the opening degree (differential amount) of gas proportional valve 70 in the combustion apparatus according to the present embodiment.

  Referring to FIG. 5, voltage detection circuit 350 is further provided in the combustion apparatus according to the present embodiment.

  The voltage detection circuit 350 includes an operational amplifier 360 and resistance elements R4 and R5. The electric resistance values of the resistance elements R4 and R5 are also expressed as R4 and R5. The operational amplifier 360 is connected to the power supply wiring 210 and the ground wiring 215, and operates by receiving the supply of the power supply voltage Vs.

  The inverting input terminal (− terminal) of the operational amplifier 360 is connected to the ground wiring 215. That is, the ground voltage GND2 is input to the inverting input terminal (− terminal). The non-inverting input terminal (+ terminal) of the operational amplifier 360 is electrically connected to the ground wiring 225 (GND1) via the resistance element R4. Furthermore, the resistance element R5 is connected between the non-inverting input terminal (+ terminal) of the operational amplifier 360 and the output terminal.

  As a result, the operational amplifier 360 and the resistance elements R4 and R5 constitute an inverting amplifier. Therefore, the voltage detection circuit 350 outputs the detection voltage Vdg obtained by amplifying the voltage difference (GND2-GND1) according to the resistance ratio (R5 / R4). The detection voltage Vdg is Vdg = 0 when GND1 = GND2 (normal), while Vdg> 0 as GND2 rises. That is, the detection voltage Vdg is a voltage proportional to the variation amount ΔVgnd of the GND 2 (hereinafter also referred to as the GND voltage difference ΔVgnd).

  The microcomputer 100 includes nodes 101 and 105, an A / D converter 102, a CPU 104, and a D / A converter 106.

  The A / D converter 102 is configured to convert an analog voltage input to the node 101 into digital data having a predetermined number of bits. The D / A converter 106 is configured to convert digital data output from the CPU 104 into an analog voltage.

  Detection voltage Vdg from voltage detection circuit 350 is transmitted to node 101 of microcomputer 100. The A / D converter 102 converts the detection voltage Vdg into digital data DVdg and outputs it to the CPU 104.

  The CPU 104 outputs digital data DVsv indicating the opening command value of the gas proportional valve 70 by a control calculation using the digital data DVdg. The D / A converter 106 converts the digital data DVsv from the CPU 104 into a control command voltage Vsv that is an analog voltage. Control command voltage Vsv is input from node 105 to drive circuit 300 (FIG. 2).

  FIG. 6 is a flowchart illustrating opening degree control calculation processing of the gas proportional valve according to the first embodiment. The control process according to the flowchart shown in FIG. 6 is repeatedly executed by the microcomputer 100 every control cycle (for example, every 100 ms).

  With reference to FIG. 6, the microcomputer 100 calculates the opening command value of the gas proportional valve 70 by the combustion control in the combustion burner 50 in step S100. Further, the drive current Id is calculated according to the map or the arithmetic expression described above in correspondence with the calculated opening command value.

  For example, the required heat generation amount for the combustion burner 50 is calculated based on the temperature information and the flow rate information so that the temperature of the hot water from the hot water supply device 10 is controlled to the set hot water temperature. Further, the fuel gas supply amount from the combustion burner 50 is determined according to the calculated required heat generation amount. The opening command value of the gas proportional valve 70 can be calculated corresponding to the calculated fuel gas supply amount.

  In step S110, the microcomputer 100 converts the drive current Id calculated in step S100 into a control command voltage Vsv. For example, Vsv = R0 · Id can be calculated according to the equation (1).

  Further, in step S120, the microcomputer 100 reads the detection voltage Vdg that changes depending on the GND voltage difference ΔVgnd based on the digital data DVdg from the A / D converter 102.

  In step S130, the microcomputer 100 calculates a correction amount ΔVsv for the control command voltage Vsv calculated in step S110 according to the detection voltage Vdg read in step S120.

  As can be understood from FIG. 4, by correcting the control command voltage Vsv according to the GND voltage difference ΔVgnd, the same drive current Id as when GND1 = GND2 can be secured. Therefore, the correction amount ΔVsv can be determined so as to compensate for the GND voltage difference ΔVgnd calculated backward from the detection voltage Vdg. When the ground voltage GND2 of the drive circuit 300 is not changing (GND2 = GND1), ΔVsv = 0.

  In step S140, the microcomputer 100 calculates the control command voltage Vsv from the microcomputer 100 according to the sum of the control command voltage (S110) obtained from the combustion control and the correction amount ΔVsv calculated in step S130.

  Referring to FIG. 5 again, CPU 104 outputs digital data DVsv to D / A converter 106 in accordance with control command voltage Vsv calculated in step S140 of FIG. The D / A converter 106 converts the digital data DVsv from the CPU 104 into an analog voltage and outputs it from the node 105. As a result, the control command voltage Vsv is input to the drive circuit 300 shown in FIG.

  Thus, according to the combustion apparatus according to the first embodiment, even if the ground voltage of drive circuit 300 of gas proportional valve 70 fluctuates, detection changes depending on GND voltage difference ΔVgnd (ΔVgnd = GND2−GND1). Based on the voltage Vdg, the control command voltage Vsv from the microcomputer 100 to the drive circuit 300 can be corrected. Therefore, by preventing fluctuations in the drive current Id of the gas proportional valve 70 due to the influence of ground voltage fluctuations, the gas proportional valve 70 that controls the fuel supply in the combustion apparatus is accurately controlled in accordance with a command from the microcomputer 100. can do.

[Embodiment 2]
In the first embodiment, an example in which the detection voltage Vdg from the voltage detection circuit 350 is input to the microcomputer 100 as a voltage that changes depending on the GND voltage difference ΔVgnd (ΔVgnd = GND2−GND1) has been described. In the second embodiment, a modification of detecting the GND voltage difference ΔVgnd will be described.

FIG. 7 is a block diagram for controlling the opening of the gas proportional valve according to the second embodiment.
Referring to FIG. 7, drive circuit 300 for gas proportional valve 70 is configured in the same manner as in the first embodiment (FIG. 3). That is, the drive current Id of the gas proportional valve 70 is controlled by the drive transistor 320 according to the control command voltage Vsv from the microcomputer 100.

  In the combustion apparatus according to the second embodiment, a voltage detection circuit 400 is provided instead of voltage detection circuit 350 shown in FIG.

The voltage detection circuit 400 includes an operational amplifier 410 and resistance elements Ra and Rb. The electric resistance values of the resistance elements Ra and Rb are also expressed as Ra and Rb. Operational amplifier 410 is connected to the power supply line 2 2 0 and ground wiring 2 2 5, it operates by receiving the power supply voltage V c. Therefore, the operational amplifier 410 is preferably arranged in the vicinity of the microcomputer 100.

  The inverting input terminal (− terminal) of the operational amplifier 410 is electrically connected to the node Nd of the drive circuit 300 via the wiring 240 and the resistance element Ra. On the other hand, the non-inverting input terminal (+ terminal) of the operational amplifier 410 is electrically connected to the ground wiring 215 via the wiring 216. The resistance element Rb is electrically connected between the inverting input terminal (− terminal) of the operational amplifier 410 and the output terminal.

  Thereby, the operational amplifier 410 and the resistance elements Ra and Rb constitute an inverting amplifier. Therefore, voltage detection circuit 400 outputs detection voltage V0 obtained by amplifying voltage drop amount ΔV0 (ΔV0 = Id · R0) at resistance element R0 according to the resistance ratio (Rb / Ra). The detection voltage V 0 from the voltage detection circuit 400 is input to the node 101 of the microcomputer 100. Therefore, the microcomputer 100 can acquire the detection voltage V0 from the digital data from the A / D converter 102 (FIG. 5).

  Here, as shown in FIG. 4, when the GND voltage difference ΔVgnd occurs, the voltage drop amount ΔV0 changes with respect to the same control command voltage Vsv. Therefore, it is understood that the detection voltage V0 also changes depending on the GND voltage difference ΔVgnd. Note that the wirings 216 and 240 need to transmit the voltage of the node Nd and the ground wiring 215 to the operational amplifier 410. Therefore, in particular, it is preferable not to connect a device group that consumes current to the wiring 216.

  FIG. 8 is a flowchart illustrating the opening degree control calculation process of the gas proportional valve according to the second embodiment. The control process according to the flowchart shown in FIG. 8 is also repeatedly executed by the microcomputer 100 every control cycle (for example, every 100 ms).

  Referring to FIG. 8, microcomputer 100 calculates an opening command value of gas proportional valve 70 in step S <b> 100 similar to FIG. 6, and generates drive current Id corresponding to the calculated opening command value. Calculate further.

  The microcomputer 100 converts the drive current Id calculated in step S110 into the control command voltage Vsv in step S110 similar to FIG.

  Further, in step S125, the microcomputer 100 reads the detection voltage V0 that changes depending on the GND voltage difference ΔVgnd based on the digital data from the A / D converter 102.

  In step S135, the CPU 130 corrects the control command voltage Vsv calculated in step S110 according to the voltage difference (V0 * −V0) between the reference value V0 * of the detection voltage V0 and the read detection voltage V0. ΔVsv is calculated. Here, the reference value V0 * is the value of the detection voltage V0 when GND1 = GND2, and can be calculated from the control command voltage Vsv indicating the original drive current Id. Therefore, when GND1 = GND2 (ΔVgnd = 0), V0 * = V0. On the other hand, when the GND voltage difference ΔVgnd occurs, (V0 * −V0) increases in proportion to ΔVgnd.

  For this reason, in step S135, when the ground voltage GND2 of the drive circuit 300 does not fluctuate (GND2 = GND1), ΔVsv = 0. On the other hand, when the GND voltage difference ΔVgnd occurs, the same drive current Id as when GND1 = GND2 can be secured by correcting the control command voltage Vsv according to the voltage difference (V0 * −V0). it can.

  The microcomputer 100 controls the control command voltage from the microcomputer 100 according to the sum of the control command voltage (S110) obtained from the combustion control and the correction amount ΔVsv calculated at step S135 in step S140 similar to FIG. Vsv is calculated. The drive circuit 300 controls the drive current Id of the gas proportional valve 70 according to the control command voltage Vsv calculated in step S140.

  Thereby, in the combustion apparatus according to the second embodiment, even if the ground voltage of the drive circuit 300 of the gas proportional valve 70 fluctuates, from the microcomputer 100 based on the detection voltage V0 that changes depending on the GND voltage difference ΔVgnd. The control command voltage Vsv to the drive circuit 300 can be corrected. As a result, since the drive current Id of the gas proportional valve 70 can be prevented from fluctuating due to the influence of the ground voltage variation, the gas proportional valve 70 for controlling the fuel supply in the combustion apparatus can be controlled by a microcomputer as in the first embodiment. It is possible to accurately control in accordance with a command from 100.

  In this embodiment, gas is exemplified as the fuel in the combustion mechanism, but combustion using any fuel is possible as long as the fuel supply amount is controlled by a device whose operation amount changes according to the drive current. The present invention can be applied to an apparatus.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 10 Hot-water supply apparatus, 20 Inlet pipe, 30 Outlet pipe, 40 Heat exchanger, 50 Combustion burner, 55 Gas supply pipe, 60 Gas solenoid valve, 70 Gas proportional valve, 90 Load, 100 Microcomputer, 101,105 Input / output node ( Microcomputer), 102, 106 Converter, 110 External power supply, 120 Diode bridge, 130, 170, 190 Smoothing capacitor, 140 Transistor, 150 Transformer, 152 Primary winding, 155 Secondary winding, 160 Diode, 180 Voltage Regulator, 200, 210, 220 Power supply wiring, 205, 215, 225 Ground wiring, 216, 240 wiring, 300 drive circuit, 310, 360, 410 operational amplifier, 320 drive transistor, 350, 400 voltage detection circuit, C1 capacitor, DV dg, DVsv Digital data, Na, Nb, Nd node, GND ground voltage (transformer secondary side), GND1 ground voltage (microcomputer), GND2 ground voltage (drive circuit), GND # ground voltage (transformer primary side), Id Drive current (gas proportional valve), R0 to R5, Ra, Rb resistance elements, V0, Vdg detection voltage, V0 * reference value (detection voltage V0), Vc, Vs power supply voltage, Vsv control command voltage.

Claims (3)

A combustion device,
A combustion mechanism configured to generate heat by fuel combustion;
A control device configured to control a fuel supply amount according to an operation amount that changes according to a drive current; and
First and second ground wirings for supplying a common ground voltage;
A microcomputer for controlling the operation amount of the control device;
A drive circuit for adjusting the drive current of the control device according to a control command voltage from the microcomputer;
The microcomputer is grounded by the first ground wiring,
The drive circuit is grounded by the second ground wiring,
The first and second ground wirings are electrically connected via a node connected to a smoothing capacitor;
The drive circuit is configured to control the drive current according to a voltage difference between the control command voltage and the second ground wiring;
The microcomputer is configured to receive an input of a voltage that varies depending on a voltage difference between the first and second ground wirings, and to correct the control command voltage based on the input voltage.
The combustion device comprises:
A voltage detection circuit configured to output a voltage obtained by amplifying a voltage difference between the first and second ground wirings;
The microcomputer output voltage of the voltage detection circuit as the input voltage, to correct the control command voltage according to the voltage difference between the first and second ground wiring, combustion apparatus. A combustion device,
A combustion mechanism configured to generate heat by fuel combustion;
A control device configured to control a fuel supply amount according to an operation amount that changes according to a drive current; and
First and second ground wirings for supplying a common ground voltage;
A microcomputer for controlling the operation amount of the control device;
A drive circuit for adjusting the drive current of the control device according to a control command voltage from the microcomputer;
The microcomputer is grounded by the first ground wiring,
The drive circuit is grounded by the second ground wiring,
The first and second ground wirings are electrically connected via a node connected to a smoothing capacitor;
The drive circuit is configured to control the drive current according to a voltage difference between the control command voltage and the second ground wiring;
The microcomputer is configured to receive an input of a voltage that varies depending on a voltage difference between the first and second ground wirings, and to correct the control command voltage based on the input voltage.
The drive circuit has a resistance element through which the drive current passes,
The combustion device comprises:
A voltage detection circuit for detecting a voltage drop amount in the resistance element;
The microcomputer uses the output voltage of the voltage detection circuit as the input voltage, and a voltage difference between a reference value of the voltage drop corresponding to the control command voltage and the voltage drop detected by the voltage detection circuit It corrects the control command voltage in accordance with, combustion apparatus. Wherein the control device comprises a proportional valve opening is changed according to the driving current, a combustion apparatus according to claim 1 or 2.

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