JPH0633908B2 - Drive control device for electric expansion valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a drive control device for an electric expansion valve in a refrigeration system.

(Prior Art) As a drive control device for a conventional electric expansion valve for a refrigeration system,
For example, the device described in JP-A-59-205559 can be mentioned. In this device, the degree of superheat of the evaporated refrigerant is detected, the detected degree of superheat is compared with the reference degree of superheat, and a signal corresponding to the difference is output, and the electric expansion valve is driven according to this signal. Is controlled. Further, in the above device, the number of expansion valve driving pulses per unit signal output according to the difference in the degree of superheat is changed according to the opening range of the electric expansion valve. That is, in the large opening range of the electric expansion valve, the number of drive pulses per unit signal is increased, and in the small opening range, the operation gain is adjusted so that the number of drive pulses per unit signal is decreased.

(Problems to be Solved by the Invention) The drive control device for an electric expansion valve as described above has the following drawbacks. It is necessary to use a motor with a small step angle per pulse if the electric expansion valve is controlled as described above, that is, if the small opening degree control is performed in small increments. This means that the structure of the rotor and stator of the pulse motor becomes complicated, and the electric expansion valve and thus the entire device become expensive. It is also conceivable to use a pulse motor with a relatively large step angle and use the speed reduction mechanism to perform minute control, but in this case the speed reduction mechanism becomes complicated and the entire device is also expensive. There will be a problem that it will become a strange thing.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object thereof is an electric motor that can perform precise opening control without using a cost increase even if a pulse motor having a large step angle is used. It is to provide a drive control device for an expansion valve.

(Means for Solving Problems) Therefore, in the drive control device for the electric expansion valve of the present invention, the superheat detection means (13) for detecting the superheat degree of the evaporated refrigerant and the superheat degree detected by the above are Discriminating means (16) for discriminating whether or not the state is close to the set superheat degree
When the detected superheat degree is apart from the set superheat degree, a number of pulses corresponding to the difference between the set superheat degree and the detected superheat degree is output to the electric expansion valve (5) to open the valve. Of the electric expansion valve (5) within the sampling time when the detected superheat degree is close to the set superheat degree. An opening / closing control means (19) for alternately driving one step in both the closing direction and the closing direction is provided.

(Operation) In the above-mentioned device, when the detected superheat is in a state of being away from the set superheat, that is, the electric expansion valve (5)
When it is necessary to perform a large opening control in
Similar to the conventional device, the step control means (18) inputs a number of pulses corresponding to the difference in the degree of superheat to input the electric expansion valve (5).
In the valve opening or closing direction at predetermined sampling times. On the other hand, when the detected superheat degree is close to the set superheat degree, that is, when it is necessary to control the opening degree of the electric expansion valve (5) slightly, the opening / closing control means (19) performs the sampling. The electric expansion valve (5) is alternately driven for one step in the opening direction and the closing direction within the time. Then, in the electric expansion valve (5),
An intermediate opening change of the opening change corresponding to one step occurs, which enables a minute opening change, that is, a slight superheat control.

(Embodiment) Next, a specific embodiment of the drive control device for the electric expansion valve of the present invention will be described in detail with reference to the drawings.

In FIG. 1, (1) shows an outdoor heat exchanger, (2) shows an indoor heat exchanger, and both (1) and (2).
Are connected in parallel by a liquid pipe (3) and a gas pipe (4). The liquid pipe (3) is provided with an electric expansion valve (5), and the gas pipe (4) is provided with a four-way switching valve (6). The four-way switching valve (6) is used for compression. Machine (7) is connected.

In this case, the outdoor heat exchanger (1) serves as a condenser during cooling operation and an evaporator during heating operation, while the indoor heat exchanger (2) serves as an evaporator during cooling operation and performs heating operation. It is a part that sometimes becomes a condenser. A pair of temperature sensors (8) and (9) for detecting the refrigerant temperature on the inlet side of the evaporator are attached to the liquid pipe (3), and the suction side of the compressor (7) is attached. The temperature sensor (10) is also attached to the pipe. On the other hand, (11) shows the entire drive control device for the electric expansion valve, but this device (11) has a temperature sensor (8) or (9) on the evaporator inlet side and a temperature on the compressor suction side. A superheat detection circuit (1) for detecting the superheat based on the detection result of the sensor (10).
2), and the circuit (12) and the above-mentioned sensors (8), (9), (10) detect the degree of superheat (13).
Is configured. Incidentally, (14) is an initial setting circuit for setting the opening degree of the electric expansion valve (5) at the start of operation. The outputs of the superheat detection circuit (12) and the initialization circuit (14) are input to the control circuit (15), which is detected by the detection means (13). The superheated degree has a discriminating means (16) for discriminating whether or not the superheated degree is close to the set superheat degree and another control function (17). When the detected degree of superheat is far from the set degree of superheat, the step control means (18) causes the electric expansion valve (5) to apply the number of pulses corresponding to the difference between the set degree of superheat and the detected degree of superheat. ) And the detected superheat degree is close to the set superheat degree, the opening / closing control means (19) causes the electric expansion valve (5) to pulse and close in the valve opening direction. The pulse in the valve direction and the pulse in the valve direction are alternately output step by step. The details of this control will be described below.

FIG. 2 shows the first embodiment. First, the initial setting circuit (14) sets the initial opening of the electric expansion valve (5) (step S1) and drives the compressor (7) (step S2). After that, in step S3, when a predetermined time elapses, the superheat degree detected by the superheat degree detecting means (13) is read (step S4). Then, in the next step S5, it is determined whether the detected superheat degree is within a reference set superheat degree range, is smaller than it, or is larger than it. In this case, if the detected degree of superheat is within the set range, the process returns to step S3 and this operation is repeated. If the detected superheat is less than the set superheat range, step
Moving to S6, a pulse in the valve closing direction is output to the electric expansion valve (5). In this case, step control is performed to output to the electric expansion valve (5), for example, a proportional number of pulses corresponding to the difference between the detected superheat degree and the set superheat degree. After that, hold this state for a predetermined time (step
S7), read the detected degree of superheat again (step S
8), in step S9, comparison is made with the set superheat degree range. When the detected superheat degree is still smaller than the set superheat degree range, the process returns to step S6 to perform the valve closing operation, and when the detected superheat degree is within the set superheat degree range, proceeds to step S7. Return and maintain that condition. When the detected superheat degree exceeds the set superheat degree range, the process proceeds to step S10 described below, and the open / close control mode is entered.
If the detected superheat degree exceeds the set superheat degree range in step S5, the valve opening operation opposite to the above is performed in steps S11 to S14, and the detected superheat degree is set in the superheat degree range in step S14. When it gets smaller, step S1
Switch to the open / close control mode of 0.

In the opening / closing control mode, first, in step S15, a triangular wave voltage serving as a reference value for the degree of superheat is output. As shown in Fig. 3 (a), this triangular wave voltage is centered on the set superheat range and changes over time over a wider voltage range, and the range of change is It is preferable to set a voltage corresponding to the amount of change in the degree of superheat that occurs when the expansion valve 5 is changed in opening degree by one step. On the other hand, together with the output of the triangular wave voltage, the detected degree of superheat is output as a voltage in step S16, and then the triangular wave voltage and the degree of superheat voltage are compared in step S17. As a result, there is no overlap between both voltages as indicated by A and B in FIG. 3 (a), and the detected superheat A,
When B is shifted up and down, it is determined that the load is changed or the operation mode is changed, the mode is stopped in step S18, and the process returns to step S4. If both voltages are overlapped as shown by C and D in FIG. 3 (a) and the detected superheat degree C is located on the small side, step S19 is performed.
At, the valve closing output is performed in the opening / closing control mode.
That is, as shown in C of FIG. 3 (b), the pulse motor of the electric expansion valve (5) is closed by one step from the current position within the sampling time to reduce the sampling time by half.
After the lapse of time, the valve is opened for one step, that is, the operation of returning to the original position is performed. By performing such an operation, in the electric expansion valve (5), an opening degree equivalent to that obtained by closing only 1/2 step can be obtained. The opening / closing time ratio within the sampling time may be changed according to the deviation. Further, when the detected superheat voltage and the triangular wave voltage overlap and the detected superheat D is located on the larger side, the valve opening output in the opening / closing control mode is performed in step S20. In this case, contrary to the above-mentioned valve closing output, the pulse motor of the electric expansion valve (5) is opened for one step from the current position within the sampling time, and for one step after half the sampling time has elapsed. It operates like closing the valve (Fig. 3).
(b) D). As a result, in the electric expansion valve (5),
/ 2 steps will be equivalent to opening the valve. The comparison of the triangular wave voltage and the superheat voltage in step S17 and the execution of each subsequent step are
Perform every sampling time.

As described above, in the drive control device, when the detected superheat degree is in a state of being far from the set superheat degree range,
That is, when the detected superheat degree does not overlap the triangular wave voltage as in the upper and lower positions A and B in FIG. 3 (a), the number of pulses corresponding to the difference between the set superheat degree range and the detected superheat degree is set. When the step control to output to the electric expansion valve (5) is performed and the detected superheat degree is close to the set superheat range, that is, as shown in C and D of FIG. And the triangular wave voltage overlap, the electric expansion valve (5) is alternately driven in the opening direction and the closing direction for one step within the sampling time. Therefore, even in the above-mentioned device, even with an electric expansion valve that uses a pulse motor with a large step angle, it is possible to apparently control the angle to the intermediate position of the step, and the same result as the resolution of the pulse motor is improved. Can be obtained, and as a result, accurate superheat control can be performed.

FIG. 4 shows a modified example of the control method. In this case, the step control mode and the opening / closing control mode are switched in the same manner as described above, but in this case, the judging procedure of the judging means for judging whether to execute the opening / closing control mode is changed. First, the detected superheat degree and the set superheat degree range are compared with each other by the same steps S1 to S5 as in the above embodiment. As a result, if the detected superheat degree is within the set range, the procedure returns to step S3 and the same procedure is repeated.On the other hand, if the detected superheat degree is smaller than the set superheat degree range, the superheat at that time is performed in step S6. The electric expansion valve (5) is operated by closing the electric expansion valve (5) by outputting a number of pulses to the electric expansion valve (5) according to the degree deviation. When the detected superheat degree exceeds the set superheat degree range, in step S7, the electric expansion valve (5) is opened by outputting a number of pulses corresponding to the deviation of the superheat degree at that time to the electric expansion valve (5). Operate in the valve direction. Since the procedure after step S6 and the procedure after step S7 are based on a substantially similar idea, the following steps will be described.
Only the procedure after S6 will be described. When the pulse in the valve closing direction is output in step S6, the number of output steps at that time is counted in the next step S8.
When the number of output steps is 2 or more, this state is held for a predetermined time (step S9), and then again
The superheat degree is detected (step S10), and the detected superheat degree is compared with the set superheat degree range in step S11. As a result, if the detected degree of superheat is within the above range, the process returns to step S9 and the same operation is repeated. If the detected superheat degree is smaller than the set superheat degree, the process returns to step S6 to repeat the valve closing operation, while if the detected superheat degree exceeds the set superheat degree, the process proceeds to step S7 to open the valve. Will be done.

Then, in step S8, when the counted number of steps is 1, the step is held for a predetermined time in step S12, then the superheat is detected in step S13, and then the detected superheat is detected in step S14. Compare with the set superheat range. As a result, if the detected superheat is within the set range, the process returns to step S12 to maintain this state, and if the detected superheat is still smaller than the set superheat, the process returns to step S6 to repeat the valve closing operation. . On the other hand, if the detected superheat degree exceeds the set superheat degree in step S14, in step S15,
The degree of superheat detected in step S13 is stored. Next, in step S16, contrary to the above, a pulse is output to the electric expansion valve (5) in the direction to open it by one step, and the electric expansion valve (5) is opened by one step. Valve, hold for a predetermined time in step S17,
Then, in step S18, the degree of superheat is detected again. Then, in step S19, the degree of superheat detected above is compared with the degree of superheat stored in step S15,
If the two are the same, or if the degree of superheat detected later is greater, it is determined that there has been a change in load or a change in operation mode, and the first control, that is, to step S5. return. On the other hand, when the superheat degree detected in step S18 is small, the detected superheat degree is further compared with the set superheat degree range in step S20. As a result, if the detected superheat degree is within the set range, the process returns to step S3 to maintain this opening degree, and if the detected superheat degree still exceeds the set superheat degree range, the first control ( Return to step S5). When the detected superheat degree is smaller than the set superheat degree range, the process proceeds to step S21 shown in FIG. 5 to perform the valve closing output in the opening / closing control mode.

The change phenomenon of the superheat degree from step S12 to step S20 will be described with reference to FIG. 6 (a).
First, by the output for one step in step S6,
The detected superheat degree (step S13) exceeds the set superheat degree in step S14 (Fig. 6 (a)).
Point E). Then, when the valve is opened by one step from this state (step S16), the superheat degree decreases (step S19) and further becomes smaller than the set superheat range (step S20) (FIG. 6 (a)). ) Point F). That is, when the valve is opened for one step, the superheat degree becomes smaller than the set superheat range (point F), while when the valve is closed for one step, the superheat degree is set. The state is such that it becomes larger than the range (point G). When such a state is reached, the valve closing output is performed in step S21 in FIG. That is, as shown in the lower side of FIG. 6 (b), the pulse motor of the electric expansion valve (5) is closed for one step from the current position, and for one step after half the sampling time has elapsed. Open the valve. That is, the electric expansion valve (5) for returning to the original position is operated for a predetermined time (step S22). Then, after this time has elapsed, the superheat degree is read again in step S23, and this detected superheat degree is compared with the set superheat degree range in step S24.
As a result, if the detected degree of superheat is within the set range, the process returns to step S21 and the above operation is repeated, while if it is outside the set range, the opening / closing control mode is stopped in step S25. At the same time, the initial control is performed, that is, the process returns to step S5 to repeat the series of operations described above.

Even when the above control is performed, it is possible to apparently control the opening degree at the intermediate position of the step even with the electric expansion valve (5) having a relatively large step angle, as in the above embodiment. Therefore, it is possible to obtain the same result as that when the resolution of the pulse motor is increased, and it is possible to perform accurate superheat degree control.

(Effects of the Invention) In the drive control device for the electric expansion valve of the present invention, the step control means and the opening / closing control means are provided as described above, and when it is necessary to control the minute opening degree in the electric expansion valve. Since the opening / closing control means can obtain an intermediate opening change of the opening change corresponding to one step,
Even with an electric expansion valve that uses a motor with a relatively large step angle, it is possible to perform accurate superheat degree control. Further, when it is necessary to perform a large opening degree control, the opening degree can be greatly changed by the step control means, so that it is possible to promptly deal with a large fluctuation of the superheat degree.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a drive control device for an electric expansion valve of the present invention together with a refrigerant circuit. FIG. 2 is a flow chart diagram of an example of an operation control method in the device, and FIG.
(a) is an explanatory view for explaining a relative positional relationship between the triangular wave voltage and the detected superheat voltage, and FIG. 3 (b) is an explanatory view showing an input state to the pulse motor at each position, and FIG. And FIG. 5 is a flow chart of a modification of the operation control method in the above apparatus, FIG. 6 (a) is an explanatory view showing a change state of the detected superheat degree by the above operation, and FIG. 6 (b) is a pulse motor It is explanatory drawing which shows an input state. (5) ... Electric expansion valve, (8), (9), (10) ... Temperature sensor, (11) ... Drive controller, (12) ... Superheat detection circuit, (16). Means, (18) ... Step control means, (19) ... Opening / closing control means.

Claims (1)

[Claims] 1. A superheat degree detecting means (13) for detecting a superheat degree of an evaporated refrigerant, and a judging means (16) for judging whether or not the superheat degree detected by the above is close to a set superheat degree. ), And when the detected superheat degree is away from the set superheat degree, the number of pulses corresponding to the difference between the set superheat degree and the detected superheat degree is output to the electric expansion valve (5) to output the valve. Step control means (18) for controlling the opening degree every predetermined sampling time, and the electric expansion valve (5) is opened within the sampling time when the detected superheat degree is close to the set superheat degree. A drive control device for an electric expansion valve, comprising: an opening / closing control means (19) for alternately driving only one step in both the closing direction and the closing direction.