JPH02169946A - Defrosting detector - Google Patents

Abstract

PURPOSE:To highly accurately detect frosting by providing power supply means for heating a resistance material, condensation detector means mounted on a condensation detector element, and judgement means for judging the presence of frosting. CONSTITUTION:A control section 15 drives a power supply circuit 10 to heat a resistance material 6, for gradually raising the temperature of a sensor itself. Herein, if the surface of a capacitor section 5 is frosted, the temperature of the capacitor section 5 is raised through heat transmission from the resistor material 6 to melt the frost on the surface when the temperature exceeds a dew point temperature. Hereby, electrostatic capacitance of the capacitor section 5 is rapidly changed and an oscillation frequency of an RC oscillator circuit 13 is also rapidly changed which is detected by a condensation detector circuit 18. The control section 15 stores the temperature of the resistance material 6 upon the detection. A comparator circuit 17 compares evaporation temperature TE and dew point temperature TRA both stored in the memory section 16, and the control section 15 judges frosting to be done when judgement results by 'TE' and 'TRA' measured successively are accumulated to predetermined times within a predetermined time interval.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a defrost detection device for detecting frost formation on an evaporator of an air conditioner, for example.

(Prior Art) In a heat pump air conditioner, frost may form on the outdoor heat exchanger, which serves as an evaporator, during heating operation at low outside temperatures. Frost formation reduces heating capacity. For this reason, conventionally, when frost has formed, the defrost cycle is switched to the defrost cycle, which is the opposite cycle of the heating cycle, to melt the frost on the outdoor heat exchanger.

By the way, such switching from heating operation to defrosting operation is performed by detecting frost adhering to the outdoor heat exchanger with a defrosting detection device.

Conventionally, such defrost detection devices detect the drop in evaporation temperature due to frost and determine that frost has formed when the temperature falls below a certain level, and those that detect the sevenfold change in vibration frequency caused by frost adhesion. There are methods that determine frost formation by measuring the amount of physical change, such as a change in temperature.

(Problems to be Solved by the Invention) However, in the former determination based on a drop in evaporation temperature, even if there is no frost, when the outside temperature is low, it may be determined that frost has formed due to the influence of the outside temperature. For this reason, there is a problem with accuracy.

In addition, the latter method based on physical quantities requires a complicated device and has the problem that detection accuracy cannot be expected.

This invention was made with attention to these circumstances,
The first objective is to provide a defrost detection device with a simple configuration that can detect frost formation accurately and with high detection accuracy under a wide range of conditions.

A second object is to provide a defrost detection device that can obtain the most excellent detection results.

[Configuration of the Invention (Means for Solving the Problems)] In order to achieve the above first object, claim 1 provides a resistive material whose electrical resistance changes are dependent on ambient temperature and self-temperature, and a dew condensation material. A sensor body formed by joining a detection element, a temperature detection means for detecting the ambient temperature from the output of the resistor material, an energizing means for heating the resistor material by energizing it, and a dew condensation detection element generated by this heating, L a dew condensation detection means for detecting condensation of frost from the output of the dew condensation detection element; a condensation temperature detection means for detecting the temperature of the condensation; and a condensation temperature detection means for detecting the temperature of the condensation; A defrosting detection device is constituted by a determination means for determining.

In order to achieve the second object, a sensor body is provided in a component of the evaporator with the dew condensation detection element side exposed on the upstream side of the ventilation path of the evaporator.

(Function) According to the defrosting detection device according to claim 1, the ambient temperature is outputted from the temperature detection means. Further, under the heating action of the dew condensation detection element, the temperature at which the frost adhering to the dew condensation detection element melts is outputted from the dew temperature detection means. That is, the evaporation temperature is obtained from the temperature detection means, and the dew point temperature is obtained from the condensation temperature detection means. and,
These evaporation temperatures and dew point temperatures are compared to determine whether or not frost has formed. Therefore, accurate regardless of disturbance,
Moreover, frost formation can be detected with high accuracy. Moreover,
The configuration is also simple.

According to the defrost detection device according to the second aspect, the temperature of the evaporator is detected by the resistive material, and at the same time, the dew point temperature is detected by the dew condensation detection element exposed to the air before passing through the evaporator, so that frost formation can be detected. You can obtain the information you need all at once under good conditions.

(Example) The present invention will be described below based on an example shown in FIGS. 1 to 5. Reference numeral 1 in FIG. 3 is an outdoor heat exchanger (which becomes an evaporator during heating) that constitutes a heat pump type air conditioner, for example. The outdoor heat exchanger has a structure in which heat exchange vibes 3 are passed through a large number of parallel fins 2 in a meandering manner. And this outdoor heat exchanger 1
For example, the U-shaped bone 3 of the heat exchange vibe 3 is exposed on the side of the
A sensor body 4 is installed at the tip of a.

For example, as shown in FIG. 2, the sensor body 4 includes a thin disc-shaped capacitor part 5 (corresponding to a dew condensation detection element) and a disc-shaped capacitor part 5 whose electrical resistance changes depend on the surrounding temperature and its own temperature. The resistive material 6 is closely bonded to the resistive material 6 using a bonding agent (not shown) or the like so as to maintain electrical insulation and good heat conductivity. This sensor body 4 has a capacitor section 5.
is located on the upstream side of the ventilation passage 1a of the outdoor heat exchanger 1, and the resistive material 6 side is fixed in close contact with the tip of the U-shaped rib 3a. That is, the sensor body 4 is attached so that the surface of the condenser part 5 is exposed to the air before passing through the outdoor heat exchanger 1. Note that the resistance material 6 is attached with a small contact surface that has extremely low thermal resistance.

A detection system as shown in FIG. 1 is connected to the resistive material 6 and the lead wires 7, 7 and 8 of the capacitor section 5.

That is, 9 is an electric circuit section for resistive material (hereinafter simply referred to as an electric circuit section). The second electric circuit section 9 includes a current supply circuit 10 (corresponding to current supply means) and a resistance measuring circuit 11 (corresponding to temperature detection means). The electric circuit section 9 is connected to the lead wires 7, 7, so that the resistive material 6 can be heated by electricity supply, and the ambient temperature and self-temperature can be measured by measuring the resistance of the resistive material 6.

Further, an oscillation circuit 12 is connected to the lead wires 8,8. This constitutes a CR type oscillation circuit 13 in which the capacitor section 5 is a component. That is, in the CR type oscillation circuit 13, when frost forms on the capacitor portion 5 and the capacitance changes, the oscillation frequency changes. This oscillation circuit 12 is then connected to the control section 15 (consisting of a microcomputer and its peripheral circuits) through an f/v conversion circuit 14 (which converts the oscillation frequency into a voltage corresponding to the oscillation frequency), together with the electric circuit section 9. It is connected.

The above control unit]5 is a storage unit 16. Comparison circuit 17 (corresponding to determination means), dew condensation detection circuit 18 (corresponding to dew condensation detection means)
, a temperature detection circuit 19 (corresponding to dew point temperature detection means), and an arithmetic circuit 20. The control unit 15 alternately performs, for example, a step of converting the measured resistance of the resistive material 6 into a temperature and storing it, and a step of heating the resistive material 6. Then, the control unit 15 controls, during the heating,
In order to detect a change in the frequency of the RCC optical oscillation circuit 13 due to melting of frost (if there is frost on the capacitor section 5), the resistance of the resistor material 6 at the time of the change is converted into temperature and stored in the storage section 16. I have to. Further, the control unit 15 compares the stored temperatures, and if the air dew point temperature is higher than the surface temperature of the heat exchanger, it determines this as a condition for frost formation. For example, if the repeated determinations are accumulated a certain number of times within a certain period of time, it is determined that defrosting is necessary, and the four-way valve of the heat pump refrigeration cycle 21 is switched to the defrosting side.

Next, the operation of the defrosting detection device configured as described above will be explained.

When the air conditioner is operated for heating, frost may form on the outdoor heat exchanger 1, which serves as an evaporator, when the outside temperature is high.

Generally, such frost formation on the outdoor heat exchanger 1 can be expressed by the difference between the surface temperature of the heat exchanger and the dew point of the air (outside air). That is, for the evaporation temperature T9, which is between the surface temperature of the heat exchanger and the path as shown in A in FIG.
When the air dew point temperature is high like RA (TE < TRA
) is the condensation (Δx)L on the surface of the heat exchanger, which freezes and becomes frost.

In the opposite case B (TE>TnA), no condensation occurs and no frost forms.

That is, frost formation can be determined by detecting the dew point temperature and evaporation temperature of the air. Using these temperature differences,
This invention determines frost formation.

That is, first, the resistance of the resistive material 6 is measured by the resistance measuring circuit 11 according to a command from the control section 15 . As a result, the temperature of the resistance material 6, which is at the same temperature as the outdoor heat exchanger 1, is measured. Then, the arithmetic circuit 20 of the control section 15
Then, this resistance is converted into a temperature, which is set as the evaporation temperature TE, and this temperature is stored in the storage section 16.

Next, the control unit 15 drives the energizing circuit 10 to control the resistance material 6.
The temperature of the sensor body itself is gradually raised.

Along with this energization, the RCC optical oscillation circuit 13 is driven. Furthermore, at the same time, the oscillation frequency of the RCC optical oscillation circuit 13 outputted through the f/v conversion circuit 14 is received by the dew condensation detection circuit 18.

Here, if frost forms on the surface of the capacitor section 5, the temperature of the capacitor section 5 increases due to heat transfer from the resistive material 6, and when the temperature exceeds the dew point temperature, the frost on the surface melts. Then,
The capacitance of the capacitor section 5 changes rapidly. As a result, the oscillation frequency of the RCC optical oscillation circuit 13 changes rapidly. This change is detected by the dew condensation detection circuit 18. In other words, it is detected that dew condensation has occurred. and,
The control unit 15 stores the temperature of the resistive material 6 at the time of this detection.]
I will remember it in 6. That is, the resistance value of the resistance material 6 outputted from the resistance measurement circuit 11 is converted into temperature, and the resistance value is stored in the storage unit 1.
6 as the dew point temperature TRA.

Then, the comparison circuit 17 compares the evaporation temperature TE stored in the storage section 16 and the dew point temperature TRA. Here, if the relationship rTg <TRA J holds as above, then
This is regarded as a condition for frost formation and is determined to be frost formation.

This judgment process is repeated and measurements are made every moment.
When the determination results from ``TE'' and rTRAJ are integrated a certain number of times within a predetermined time, it is determined that defrosting is necessary and the operation is switched to defrosting. Of course, after measuring "TE" and rTi A J, the a current is stopped and the sensor body 4 receives heat from the heat exchanger vibrator 3 and reaches the evaporation temperature TE.
cooled down to.

Note that when the relationship is "TE>TRB", the oscillation frequency of the RCC optical oscillation circuit 13 does not change even if the temperature of the capacitor 1ffi5 is increased, but for example in an air conditioner, depending on the capacity of the equipment, etc. Since the range in which frost formation occurs is shown in the psychrometric chart in Figure 5, this rising temperature limit temperature is set as TRB (for example, +5°C), and if there is no change in the oscillation frequency by TRB, it is assumed that frost does not form. Defrosting may not be performed.

In this way, since it detects the presence or absence of frost by comparing the evaporation temperature and dew point temperature, it can be used under a wide range of conditions, regardless of external disturbances such as when the temperature drops as in the past. Accurate and accurate detection results can be obtained. Moreover, the device configuration is simple because the system only detects and compares evaporation temperature and dew point temperature, rather than detecting physical quantities such as changes in vibration frequency and weight. In particular, since the structure is such that one sensor body 4 detects both the evaporation temperature and the dew point temperature, the number of parts can be reduced.

Moreover, the structure in which the sensor body 4 is attached to the outdoor heat exchanger 1 with the condenser part 5 side exposed to the upstream side of the ventilation passage 1a is as follows.
The evaporator temperature is detected through the resistance material 6, and the dew point temperature is detected at the condenser section 5 exposed to the air before passing through the outdoor heat exchanger 1, so the information necessary for frost detection can be obtained under good conditions. can be obtained at once. Therefore, excellent detection results can be obtained.

The end of defrosting after starting the defrosting operation is determined by converting the resistance change of the resistance material 6 into temperature, and for example, if this temperature is "
The determination can be made based on whether the temperature exceeds the melting point of water, such as +5°C.

[Effects of the Invention] As explained above, according to the invention according to claim 1, it is possible to detect frost formation regardless of external disturbances by comparing the evaporation temperature and dew point temperature obtained from the temperature detection means and the dew temperature detection means. can be detected.

Therefore, accurate and precise detection results can be obtained under a wide range of conditions. The configuration of the device is simple, as it only involves detecting and comparing the evaporation temperature and dew point temperature. In addition, since one sensor body detects both the evaporation temperature and the dew point temperature, the number of parts can be reduced.

Further, according to the invention described in claim 2, the temperature of the evaporator is detected from the resistive material, and the dew point temperature is detected by the dew condensation detection element exposed to the air before passing through the evaporator, which is necessary for frost detection. information can be obtained all at once under good conditions, and the best detection results can be obtained.

[Brief explanation of the drawing]

1 to 5 show one embodiment of the present invention.
The figure is a block diagram showing the configuration of the defrost detection device, Figure 2 is a perspective view of the sensor body, Figure 3 is a perspective view showing the installation structure of the sensor body on the evaporator, and Figure 4 is the evaporation temperature and air dew point. A diagram showing the relationship with temperature, FIG. 5 is a diagram showing the range where frost formation occurs in an air conditioner to which a defrost detection device is applied. DESCRIPTION OF SYMBOLS 1... Outdoor heat exchanger (evaporator), 4... Sensor body, 5... Capacitor part (dew condensation detection element), 6... Resistance material, 10... Current-carrying circuit (current-carrying means) , 11... Resistance measurement circuit (temperature detection means') 13.18...R
C-type oscillation circuit, dew condensation detection circuit (dew condensation detection means) 17...
Comparison circuit (determination means), 19... Temperature detection circuit (dew point temperature detection means). Applicant's agent Patent attorney Takehiko Suzue Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A sensor body formed by joining a dew condensation detection element to a resistive material whose electrical resistance changes depend on ambient temperature and self-temperature, and detecting the ambient temperature from the output of the resistive material. a temperature detection means for detecting, an energization means for heating the resistive material by energizing it, a dew condensation detection means for detecting dew condensation on the dew condensation detection element caused by this heating from an output of the dew condensation detection element, and a temperature of the condensation. What is claimed is: 1. A defrosting detection device comprising: a dew condensation temperature detection means for detecting dew condensation temperature; and a determination means for comparing the dew condensation temperature with the ambient temperature to determine the presence or absence of frost formation. 2. The defrosting detection device according to claim 1, wherein the sensor body is provided on a component of the evaporator with the dew condensation detection element side exposed on the upstream side of the ventilation path of the evaporator.