JPH0747994B2 - Control device for proportional control valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for a proportional control valve that adjusts the passage amount of a fluid in accordance with an energizing current.

[Prior Art] Proportional to simplify arithmetic processing in a control device in order to adjust a passage amount of a fluid according to a control state such as a fuel supply amount to a burner whose combustion amount must be adjusted. Control valves are often used.

In this case, a control amount having a calculation function calculates a control amount, a control voltage is output as a control signal, and a direct current corresponding to the control voltage is supplied to the proportional control valve by the drive circuit.

[Problems to be Solved by the Invention] However, in the proportional control valve, the force for adjusting the passage amount of the fluid by the energizing current is generated against the pressure applied to the diaphragm by the passing fluid. In the conventional control device for the proportional control valve, even if the same current value is applied, the flow rate of the fluid to be adjusted is different depending on whether the flow rate is increased or decreased. For example, the solid line D in FIG.
Since a hysteresis as shown in (3) occurs, an accurate flow rate cannot be obtained.

For this reason, there is a problem that the outlet heated water temperature corresponding to the set temperature cannot be obtained in a device that requires precise fuel adjustment such as a gas water heater that can set the outlet heated water temperature.

Further, in the conventional device, since the current value corresponding to the target opening is constantly energized in order to maintain the opening of the proportional control valve in accordance with the control state, the energizing element ( For example, the load on the power transistor) is heavy,
The calorific value is large.

Furthermore, as the control signal to the drive circuit of the proportional control valve,
Since it is necessary to output the control voltage according to the control amount, there is a problem that the load on the circuit configuration of the control circuit that performs arithmetic processing increases.

The present invention, in a control device for a proportional control valve, reduces hysteresis to improve the opening characteristic of the proportional control valve, reduces the energization load on the energizing elements of the proportional control valve, and further simplifies the circuit configuration. The purpose is to

[Means for Solving the Problem] The present invention relates to a proportional control valve control device for controlling a proportional control valve that adjusts a flow rate of a fluid in proportion to an energized current, in accordance with a target opening degree of the proportional control valve. A control signal transmitting means for transmitting a pulse-width-modulated pulse-shaped control signal, and a signal conversion circuit for converting the pulse-shaped control signal of the control signal transmitting means into a voltage signal indicating a voltage value according to the target opening degree, A current value control circuit provided in the energizing circuit of the proportional control valve for controlling the energizing current of the energizing circuit to a current value according to the voltage signal converted by the signal converting means, and a fixed pulse signal is generated. A pulse generating circuit; and a switching circuit which is provided in the energizing circuit of the proportional control valve in series with the current value control circuit and which interrupts energization of the proportional control valve in response to the pulse signal of the pulse generating circuit. The provision is a technical means.

[Operation] In the present invention, the pulse-shaped control signal sent from the control signal sending means is converted into a voltage signal indicating a voltage value according to the target opening in the signal conversion circuit, and a current value according to this voltage signal is changed. It is the current value of the energizing circuit of the proportional control valve. On the other hand,
The energizing circuit of the proportional control valve is provided with a switching circuit that connects and disconnects the energization in accordance with a fixed pulse signal of the pulse generating circuit in series with the current value control means to connect and disconnect the energizing current to the proportional control valve. Therefore, in the proportional control valve, the control current value of the current value control circuit is intermittently energized at a fixed pulse signal period.

In this case, if the pulse width of the pulse signal generated by the pulse generation circuit is short, the current constantly changes, so the valve body of the proportional control valve cannot follow the change in the energizing current, so a small vibration occurs and the effective effect of the energizing current is reduced. It exhibits an opening according to the value.

EFFECTS OF THE INVENTION In the present invention, the proportional control valve vibrates slightly and exhibits an opening corresponding to the effective value of the energized current. Therefore, when the same current value is energized, the opening gradually increases. There is almost no difference in the opening degree between the case of gradually decreasing and the case of gradually decreasing. Therefore, the hysteresis can be reduced.

Further, since the current switched to the proportional control valve is intermittently energized with the current switched according to the pulse signal,
Since the heat generated by energization is effectively dissipated, the heat generation temperature becomes low. Therefore, the load on the energizing element is reduced.

Since a CR circuit can be used as a signal conversion circuit for converting the pulse-width-modulated control signal into a voltage signal, the circuit configuration around the control circuit can be simplified and the linearity can be improved. .

On the other hand, since the control circuit may output a pulse width modulated control signal, for example, when a microcomputer is used, it can be integrated with other control elements to form one control circuit.

Therefore, the circuit configuration can be simplified.

[Embodiment] Next, the present invention will be described based on an embodiment of a gas water heater 1 for hot water heating, which is schematically shown in FIG.

A burner group 11 including a plurality of burners is provided in the combustor case 10. Below the combustor case 10,
A blower 12 for supplying combustion air to the burner group 11 is provided. A water pipe type heat exchanger 13 is provided above the burner group 11 in the combustor case 10, and the water passing through the inside is heated by the combustion heat of the burner group 11. In the vicinity of the burner group 11 in the combustor case 10, a sparker 14 that ignites the burner group 11 and a frame rod 15 that detects ignition of the burner group 11 are provided. Further, an exhaust port 2 for discharging combustion exhaust gas to the outside is provided above the combustor case 10.

A nozzle pipe 16 for supplying fuel gas is provided below the burner group 11, and the nozzle pipe 16 is provided with a plurality of fuel ejection ports 16a for ejecting fuel gas corresponding to each burner of the burner group 11. It is provided.

The fuel pipe 20 for guiding the fuel gas to the nozzle pipe 16 has two solenoid valves 21 and 22 for passing the fuel gas when energized, and a governor for controlling the supply amount of the fuel gas by controlling the supply pressure according to the energized current. Proportional valves 23 are provided in order from the upstream side.

To the heat exchanger 13, water pipes 17 and 17a for circulating heated hot water are connected.

A pump 18 for forcibly circulating hot water is provided in a water pipe 17 upstream of hot water passing through the heat exchanger 13, and an expansion tank 18a for expanding hot water is provided further upstream thereof. There is.

The water pipe 17a connected to the downstream side of the heat exchanger 13 is connected to a heating heat exchanger 19 provided in the room, and the heating heat exchanger 19 is further connected to the expansion tank 18a described above. .

The water is heated by being pushed into the heat exchanger 13 by the pump 18, and the hot water flowing out of the heat exchanger 13 warms the room by the heating heat exchanger 19, and each heat exchanger 13, 19, the water pipe 17,
It circulates in 17a.

On the other hand, the water pipe 17a, which corresponds to the downstream side of the heat exchanger 13, is provided with a thermistor 25 for detecting the temperature of the heated hot water.

A water supply pipe (not shown) is connected to the expansion tank 18a, and water is supplied as needed.

The gas water heater 1 for hot water heating configured as described above is controlled by the control device 30.

As shown in FIG. 3, the control device 30 includes a microcomputer 31, an input circuit 32, and an output circuit 33, and controls an operating state based on each input signal in response to an operation signal from the controller 40.

Microcomputer 31 (hereinafter referred to as "microcomputer 31")
When the controller 40 instructs the start of operation, the pump 18 is driven to circulate water and
Ignition control for igniting the burner group 11 by 14 and starting combustion is performed. Further, the combustion is stopped by the stop signal, and even when the flame is not detected by the flame rod 15 due to the extinction, the solenoid valves 21 and 22 are closed to prevent fuel leakage.

After the combustion is started, the combustion amount is determined based on the detection signal of the thermistor 25 input via the input circuit 32 and the heating temperature set by the controller 40, and the output circuit 33 outputs the blower 12 based on the combustion amount. Also, the governor proportional valve 23 is controlled to heat the warm water circulating in the heat exchanger 13 to a predetermined temperature, and the pump 18 is driven to heat the room.

Here, the blower 12 is driven according to the determined combustion amount, and the governor proportional valve 23 is controlled according to the number of revolutions of the blower 12 indicating the operating state thereof.

A pulse width-modulated (PWM) pulse signal is used as a control signal to the output circuit 33 for controlling the blower 12 and the governor proportional valve 23.

Further, from the microcomputer 31, as a switching signal for energizing the governor proportional valve 23, as shown in FIG. 4A, the pulse repetition period T, the pulse width W and the pulse height H are controlled. A pulse signal with a constant waveform is used regardless.

Next, a proportional valve drive circuit 50 for driving the governor proportional valve 23 in the output circuit 33 will be described with reference to FIG.

When the switching signal from the microcomputer 31 is sent, the proportional valve drive circuit 50 conducts a current value corresponding to the control signal that has been pulse width modulated and sent.

Here, a switching transistor 51 that opens and closes an electric path according to a switching signal of the microcomputer 31, a CR circuit 52 that demodulates a control signal that is pulse-width modulated and sent, an operational amplifier 53 that amplifies the demodulated signal in two stages, 54, a transistor 55 for supplying a current value according to the output current of the operational amplifier 54 to the governor proportional valve 23.

Next, the operation of the gas water heater of the present embodiment having the above configuration will be described.

When the user operates the controller 40 to instruct the start of the heating operation, the pump 18 operates, and the water flows through the water pipe 17a, the heat exchanger 13, the water pipe 17, the heating heat exchanger 19, and the expansion tank 18a.
Start circulation in the circulation path consisting of.

Further, the solenoid valves 21, 22 are opened to supply the fuel gas to the burner group 11, the sparkers 14 are operated, the burner group 11 is ignited, and the combustion is started.

When ignition is detected by the frame rod 15, based on the heating temperature set by the controller 40 and the outflow temperature from the heat exchanger 13 detected by the thermistor 25,
The combustion amount is determined, and the blower 12 and the governor proportional valve 23 are controlled based on the determined combustion amount.

At this time, the control signal sent from the microcomputer 31 to the output circuit 33 to control the blower 12 and the governor proportional valve 23 is a pulse signal whose pulse width is modulated according to the target value. The switching signal for instructing to energize 23 is a constant pulse signal.

As a result, the governor proportional valve 23 energized by the proportional valve control circuit 50 is pulse-amplitude modulated by the switching signal as shown in B of FIG.
The pulse width W is constant, and a pulse current whose only pulse height H changes according to the control amount is supplied.

Therefore, the valve body of the governor proportional valve 23 cannot follow the change of the pulse current and vibrates slightly to increase the flow rate.
Regardless of the case where the flow rate is decreased, the opening degree according to the effective value of the pulse current is exhibited.

Therefore, the secondary pressure of the fuel gas adjusted by the governor proportional valve 23 has much less hysteresis than the conventional one, as shown by the solid line C in FIG.

Further, since the governor proportional valve 23 is energized by a pulse current whose pulse amplitude is modulated, energization is performed only when a pulse is input. Therefore, each transistor for energizing the governor proportional valve 23 is intermittently energized with the current switched according to the pulse signal. Therefore, the heat generated by the energization is effectively dissipated, and the heat generation temperature is lowered. Therefore, the load on the energizing element is reduced, and the heat sink of the transistor can be downsized.

Further, since the control signal pulse-width modulated (PWM) is demodulated by the microcomputer, the linearity can be improved. At this time, as a demodulation circuit for demodulation, a CR circuit having a simple circuit configuration can be used instead of the low-pass filter, so that the circuit configuration of the output circuit for driving the governor proportional valve is simplified.

In addition, since the microcomputer can be integrated with the control of other blowers to form one control circuit,
The circuit configuration of the entire control device can be simplified.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a proportional valve drive circuit in a gas water heater showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing an outline of the gas water heater of this embodiment, and FIG. 3 is this embodiment. 4 is a block diagram showing the configuration of the control device of FIG. 4, FIG. 4 is a current waveform diagram showing a switching signal in the control device of the present embodiment and a current flowing to the governor proportional valve, and FIG. 5 is a control characteristic of the governor proportional valve according to the embodiment. FIG. 6 is a characteristic diagram showing the control characteristic of the governor proportional valve according to the conventional device. In the figure, 23 ... Governor proportional valve (proportional control valve), 30 ... Control device (control device for proportional control valve), 31 ... Microcomputer (control signal sending means, pulse generation circuit), 50 ...
Proportional drive circuit (energization circuit for proportional control valve), 51 …… transistor (switching circuit), 52 …… CR circuit (signal conversion circuit), 55 …… transistor (current value control circuit).

Claims (1)

[Claims] 1. A controller of a proportional control valve for controlling a proportional control valve for adjusting a flow rate of a fluid in proportion to an energizing current, wherein a pulse-shaped control in which a pulse width is modulated according to a target opening of the proportional control valve. A control signal transmission means for transmitting a signal, a signal conversion circuit for converting a pulsed control signal of the control signal transmission means into a voltage signal indicating a voltage value according to the target opening, and a current supply circuit for the proportional control valve. A current value control circuit, which is provided and controls the energization current of the energization circuit to a current value according to the voltage signal converted by the signal conversion means, a pulse generation circuit which generates a fixed pulse signal, and the proportional control And a switching circuit which is provided in the energizing circuit of the valve in series with the current value control circuit and interrupts energization of the proportional control valve in response to the pulse signal of the pulse generating circuit. Control device for example a control valve.