JP2010105466A - Air-conditioner for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve both of preventing the frosting of an evaporator and suppressing the deterioration in the air-conditioning feeling of an occupant. <P>SOLUTION: This air-conditioner includes a refrigerating cycle 10 evaporating discharged coolant from a compressor 11 by the evaporator 9 and cooling the air blown out into the cabin, an evaporator temperature sensor 34 detecting the temperature of the evaporator 9, a frosting prevention control means stopping the compressor 11 when the detected value of the evaporator temperature sensor 34 is below a first set temperature and restarting the compressor 11 when the detected value of the evaporator temperature sensor 34 exceeds a second set temperature, a temperature setting means setting the first set temperature, an operating ratio calculating means calculating the operating ratio of the compressor 11, and a cooling thermal load estimation means estimating the cooling thermal load condition of the evaporator 9 based on the operating ratio of the compressor 11. The temperature setting means sets the first set temperature at a temperature higher than a reference temperature when the cooling thermal load condition of the evaporator 9 is in a first condition in which the frosting easily occurs, and sets the first set temperature at a temperature lower than the reference temperature when the cooling thermal load condition of the evaporator 9 is in a second condition in which the frosting hardly occurs. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle air conditioner that controls the temperature of an evaporator by intermittently controlling the operation of a compressor that sucks and compresses refrigerant.

  Conventionally, in a vehicle air conditioner, when the compressor is driven by an external drive source (engine or the like), the operation of the compressor is intermittently controlled by an electromagnetic clutch or the like to control the temperature of the evaporator. Yes.

  More specifically, a temperature sensor is arranged at a representative part immediately after the air blowing of the evaporator, and the temperature detected by the temperature sensor (the temperature of the blowing air of the evaporator) is set in advance to prevent the evaporator from frosting. When the temperature falls below the reference temperature (off-side target temperature), the operation of the compressor is stopped. When the detected temperature of the temperature sensor becomes higher than the temperature obtained by adding a predetermined hysteresis width to the off-side target temperature (on-side target temperature), the compressor is restarted.

  Here, in the control of the compressor of a normal vehicle air conditioner, since the off-side target temperature set for the above-mentioned frost prevention is a constant value, when the temperature change of the air blown from the evaporator is large, There was a case where frost was generated in the evaporator due to a response delay such as stoppage of operation of the compressor.

In order to suppress the occurrence of frost in the evaporator, for example, in Patent Document 1, the temperature change rate per unit time of the air blown from the evaporator is detected, and when the temperature change rate is a predetermined value or more, the compressor The off-side target temperature that is the operation stop condition is changed to a temperature higher than a preset reference temperature.
Japanese Patent Laid-Open No. 2007-302020

  By the way, for example, in a state where the cooling capacity is insufficient, such as in the summer (a state where the cooling heat load of the evaporator is high), the frost is generated in the evaporator because the air temperature on the suction side of the evaporator is high. It is difficult to occur. In such a state, when the compressor control described in Patent Document 1 is executed, the off-side target temperature in which the temperature change rate is equal to or higher than a predetermined value and the temperature of the air blown from the evaporator is set higher than the reference temperature. If it falls below, the operation of the compressor will be stopped. In this case, the frost of the evaporator is difficult to occur, and the compressor is stopped despite the insufficient cooling capacity. Therefore, the passenger's air conditioning feeling is significantly deteriorated due to a rise in the passenger compartment temperature. There is a problem such as.

  An object of this invention is to make compatible the prevention of the frost of an evaporator, and suppression of the deterioration of the air-conditioning feeling of a passenger | crew in a vehicle interior in view of the said point.

  In order to achieve the above object, according to the first aspect of the present invention, the refrigerant discharged from the compressor (11) is evaporated in the evaporator (9) and the refrigeration cycle (10) for cooling the air blown out into the passenger compartment. The evaporator temperature detection means (34) for detecting the blown air temperature or the evaporator surface temperature of the evaporator (9), and the detection value detected by the evaporator temperature detection means (34) is a preset reference. The operation of the compressor (11) is stopped when the temperature falls below the first preset temperature that is initially set, and the compressor (11) is actuated when the temperature exceeds a second predetermined temperature that is higher than the first set temperature. Of the compressor (11) when the operation of the compressor (11) is controlled by the frost prevention control means for executing the control to resume the operation, the temperature setting means for setting the first set temperature, and the frost prevention control means. Stop time, and compressor The operating rate calculating means for calculating the operating rate of the compressor (11) based on the operating time of 11), and the cooling heat load state of the evaporator (9) based on the operating rate calculated by the operating rate calculating means The temperature setting means is estimated to be a first state in which the cooling heat load state of the evaporator (9) is likely to cause frost in the evaporator (9) by the cooling heat load estimation means. The first set temperature is set to a temperature higher than the reference temperature, and the cooling heat load state of the evaporator (9) is set to a temperature higher than the reference temperature, and the second state in which the frost is unlikely to occur in the evaporator (9). Is estimated, the first set temperature is set to a temperature lower than the reference temperature.

  According to this, when it is estimated that the cooling heat load state of the evaporator (9) is the first state in which the evaporator (9) is likely to generate frost based on the operating rate of the compressor (11), the reference temperature When the temperature falls below the first set temperature set at a higher temperature, the operation of the compressor (11) stops. Therefore, in the first state in which frost is likely to be generated in the evaporator (9), it is possible to prevent the frost from being generated in the evaporator (9) due to a response delay such as operation stop of the compressor (11). In the first state where the frost is likely to be generated in the evaporator (9), the cooling heat load of the evaporator (9) is small and the cooling capacity is excessive. It does not worsen the passenger's air conditioning feeling.

  On the other hand, when it is estimated that the cooling heat load state of the evaporator (9) is the second state in which the frost is unlikely to occur in the evaporator (9) based on the operating rate of the compressor (11), the initially set reference The compressor (11) is not stopped until the temperature falls below the first set temperature set to a temperature lower than the temperature. Therefore, in the second state where the frost is unlikely to occur in the evaporator (9), the operation continuation time of the compressor (11) can be lengthened, and the air conditioning feeling of the passenger in the passenger compartment due to the operation stop of the compressor (11). Can be prevented. In the second state in which frost is unlikely to occur in the evaporator (9), the cooling heat load of the evaporator (9) is large and the cooling capacity is insufficient, so the temperature of the evaporator (9) is reduced to the evaporator (9). 9) It is difficult to decrease to a temperature at which frost is generated.

  Therefore, both the prevention of the frost of the evaporator (9) and the suppression of the deterioration of the air conditioning feeling of the passenger in the passenger compartment can be achieved by changing the first set temperature according to the cooling heat load state of the evaporator (9). Can do.

  By the way, when the cooling heat load state of the evaporator (9) is the first state in which frost is likely to be generated in the evaporator (9), the evaporator (9) after the operation of the compressor (11) is resumed. The greater the rate of temperature change (the faster the cooling rate), the more likely frost is generated in the evaporator (9). Conversely, when the evaporator (9) is in the second state in which frost is not easily generated, the frost is less likely to be generated in the evaporator (9) as the cooling rate of the evaporator (9) is lower.

  Therefore, in the invention according to claim 2, in the invention according to claim 1, the maximum value of the detected value of the evaporator temperature detecting means (34) during the operation period from the start to the stop of the compressor (11) Cooling rate calculating means () for calculating the cooling rate of the evaporator (9) based on the temperature deviation from the minimum value and the operating time of the compressor (11) during the operating period is provided, and the temperature setting means is the cooling heat load When the estimation unit estimates that the cooling heat load state of the evaporator (9) is the first state, and the cooling rate calculated by the cooling rate calculation unit is faster than a preset first reference rate, the first reference The first set temperature is set to a higher temperature than when the speed is slower than the speed, the cooling heat load state of the evaporator (9) is estimated as the second state by the cooling heat load estimation means, and the cooling speed calculation means The calculated cooling rate is set in advance. If slower than the second reference speed which is, and sets the first predetermined temperature than when higher than the second reference speed to a lower temperature.

  Thus, when the cooling heat load state of the evaporator (9) is the first state, and the cooling rate of the evaporator (9) is faster than the first reference speed, the first set temperature is set. By setting the temperature higher, the frost generation of the evaporator (9) can be more reliably prevented.

  On the other hand, when the cooling heat load state of the evaporator (9) is the second state and the cooling rate of the evaporator (9) is slower than the second reference speed, the first set temperature is set to a low temperature. By setting to, the operation continuation time of the compressor (11) can be made longer. Therefore, it is possible to more effectively suppress the deterioration of the air conditioning feeling of the passenger in the passenger compartment due to the operation stop of the compressor (11).

  Further, specifically, as in the invention described in claim 3, in the invention described in claim 1 or 2, the thermal load estimating means has a case where the operating rate falls below a preset first reference value. When the cooling heat load state of the evaporator (9) is estimated to be the first state, and the operating rate exceeds the second reference value set higher than the first reference value, the evaporator (9) It can be estimated that the cooling heat load state is the second state.

  Further, as in the invention according to claim 4, in the invention according to any one of claims 1 to 3, in the operation rate calculation means, after the operation of the compressor (11) is stopped, the operation is resumed, When the period until the operation is stopped again is one cycle, the compressor operation ratio occupied by the operation time of the compressor (11) in the time required for one cycle may be calculated as the operation rate.

  Further, as in the invention according to claim 5, in the invention according to any one of claims 1 to 3, in the operation rate calculation means, after the operation of the compressor (11) is stopped, the operation is resumed, When the period until the operation is stopped again is one cycle, the compressor operation ratio occupied by the operation time of the compressor (11) in the time required for one cycle is calculated for a plurality of cycles, and the calculated plurality of cycles are calculated. You may calculate the average value of a compressor operation ratio as an operation rate.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an overview of the overall system configuration of a vehicle air conditioner according to the present embodiment. The vehicle air conditioner is an indoor air conditioner disposed inside an instrument panel (not shown) at the foremost part of the vehicle interior. A unit 1 is provided. This indoor air-conditioning unit 1 has a case 2 and constitutes an air passage through which air is blown toward the vehicle interior.

  An inside / outside air switching box 5 having an inside air introduction port 3 and an outside air introduction port 4 is arranged at the most upstream part of the air passage of the case 2. Inside / outside air switching box 5, an inside / outside air switching door 6 as inside / outside air switching means is rotatably arranged.

  The inside / outside air switching door 6 is driven by a servo motor 7, and an inside air mode for introducing inside air (vehicle compartment air) from the inside air introduction port 3 and an outside air mode for introducing outside air (vehicle compartment outside air) from the outside air introduction port 4. And switch.

  On the downstream side of the inside / outside air switching box 5, an electric blower 8 that generates an air flow toward the vehicle interior is disposed. The blower 8 is configured to drive a centrifugal blower fan 8a by a motor 8b. An evaporator 9 that cools the air flowing in the case 2 is disposed on the downstream side of the blower 8. The evaporator 9 is a cooling heat exchanger that cools the air blown from the blower 8 and is one of the elements constituting the refrigeration cycle 10.

  Here, the refrigeration cycle 10 is a well-known configuration in which the refrigerant circulates from the discharge side of the compressor 11 to the evaporator 9 via the condenser 12, the liquid receiver 13, and the expansion valve 14 forming a pressure reducing means. Is. Outdoor air (cooling air) is blown to the condenser 12 by an electric cooling fan 12a.

  In the present embodiment, a fixed displacement compressor that always operates with a constant discharge capacity is adopted as the compressor 11 of the refrigeration cycle 10, and the compressor 11 is driven by a vehicle engine (not shown) via an electromagnetic clutch 11a. Driven.

  Further, the evaporator 9 cools the blown air by the low-temperature and low-pressure gas-liquid two-phase refrigerant that has been decompressed by the expansion valve 14 absorbs heat from the blown air of the blower 8 and evaporates. Here, the temperature of the evaporator 9 can be controlled by intermittently controlling the operation of the compressor 11 by intermittently energizing the electromagnetic clutch 11a of the compressor 11 described above.

  On the other hand, in the indoor air conditioning unit 1, a heater core 15 that heats the air flowing in the case 2 is disposed on the downstream side of the evaporator 9. The heater core 15 is a heating heat exchanger that heats the air (cold air) that has passed through the evaporator 9 using warm water (engine cooling water) of the vehicle engine as a heat source. A bypass passage 16 is formed on the side of the heater core 15, and the bypass air of the heater core 15 flows through the bypass passage 16.

  Between the evaporator 9 and the heater core 15, an air mix door 17 serving as a temperature adjusting means is rotatably arranged. The air mix door 17 is driven by a servo motor 18 so that its rotational position (opening degree) can be continuously adjusted.

  The ratio of the amount of air passing through the heater core 15 (warm air amount) and the amount of air passing through the bypass passage 16 and bypassing the heater core 15 (cold air amount) is adjusted by the opening degree of the air mix door 17. The temperature of the air blown into the room is adjusted.

  At the most downstream part of the air passage of the case 2, a defroster outlet 19 for blowing conditioned air toward the front window glass W of the vehicle, a face outlet 20 for blowing conditioned air toward the face of the occupant, A total of three types of air outlets 21 are provided, which are foot outlets 21 for blowing air-conditioned air toward the feet of passengers.

  A defroster door 22, a face door 23, and a foot door 24 are rotatably disposed upstream of the air outlets 19 to 21. The doors 22 to 24 are opened and closed by a common servo motor 25 via a link mechanism (not shown).

  Next, the outline of the electric control unit of the present embodiment will be described. The air conditioning control device (A / C ECU) 30 includes a known microcomputer including a CPU, a ROM, a RAM, and the like, and peripheral circuits thereof. The air conditioning control device 30 stores a control program for air conditioning control in its ROM, and performs various calculations and processes based on the control program.

  Sensor detection signals are input from the sensor groups 31 to 35 to the input side of the air conditioning control device 30, and various operation signals are input from the air conditioning panel 36 disposed near the instrument panel (not shown) in the front of the vehicle interior. Is done.

  Specifically, the sensor group detects an outside air sensor 31 that detects an outside air temperature (outside temperature) Tam, an inside air sensor 32 that detects an inside temperature (inside temperature) Tr, and an amount of solar radiation Ts incident on the inside of the vehicle. A solar radiation sensor 33, an evaporator temperature sensor 34 that is disposed immediately after the air blowing portion of the evaporator 9 and detects the evaporator blown air temperature TE, and a water temperature sensor that detects the hot water (engine cooling water) temperature Tw flowing into the heater core 15. 35 etc. are provided.

  The air-conditioning panel 36 has various temperature control switches 37 for setting the cabin temperature, a blow mode switch 38 for manually setting the blow mode switched by the blow mode doors 22 to 24, and an internal air mode by the inside / outside air switching door 6. And an outside / inside air changeover switch 39 for manually setting the outside air mode, an air conditioner switch 40 for issuing an operation command signal for the compressor 11 (ON signal of the electromagnetic clutch 11a), a blower operation switch 41 for manually setting the air volume change of the blower 8, and air conditioning automatic An auto switch 42 and the like for outputting a control state command signal are provided.

  On the output side of the air conditioning control device 30, there are an electromagnetic clutch 11a of the compressor 11, servo motors 7, 18, 25 serving as electric drive means for each device, a motor 8b of the blower 8, a motor 12b of the condenser cooling fan 12a, and the like. The operation of these devices is controlled by the output signal of the air conditioning control device 30.

  Next, the operation of this embodiment in the above configuration will be described. First, the outline of the operation of the indoor air conditioning unit 1 will be described. By operating the blower 8, the air introduced from the inside air introduction port 3 or the outside air introduction port 4 is blown through the case 2 toward the vehicle interior. . In addition, the refrigerant is circulated in the refrigeration cycle 10 by energizing the electromagnetic clutch 11a so that the electromagnetic clutch 11a is connected and the compressor 11 is driven by the vehicle engine.

  The blown air from the blower 8 first passes through the evaporator 9 to be cooled and dehumidified, and this cold air then flows through the heater core 15 and the bypass passage 16 according to the rotational position (opening) of the air mix door 17. It is divided into the flow that passes. The flow passing through the heater core 15 is heated to become hot air, and the flow passing through the bypass passage 16 remains cold air.

  Therefore, the ratio of the amount of air passing through the heater core 15 (warm air amount) and the amount of air passing through the bypass passage 16 (cold air amount) is adjusted by the opening degree of the air mix door 17, and thereby the air blown into the vehicle interior The temperature can be adjusted. And this temperature-controlled conditioned air is supplied from any one or more of the defroster air outlet 19, the face air outlet 20 and the foot air outlet 21 located at the most downstream part of the air passage of the case 2. It blows out into the passenger compartment and performs air conditioning in the passenger compartment and fogging prevention of the front window glass W of the vehicle.

  Here, in the vehicle air conditioner, the frost prevention control of the compressor 11 is performed by energization ON / OFF of the electromagnetic clutch 11 a of the compressor 11. In the frost prevention control of the compressor 11, when the blown air temperature TE (hereinafter referred to as the detected temperature of the evaporator) of the evaporator 9 detected by the evaporator temperature sensor 34 decreases to the off-side target temperature (first set temperature) TEO. The compressor 11 is stopped (the electromagnetic clutch 11a is energized OFF).

  Further, when the temperature becomes higher than the on-side target temperature (second set temperature) obtained by adding a predetermined hysteresis width (for example, 1 ° C.) to the off-side target temperature TEO, the operation of the compressor 11 is resumed (the energization of the electromagnetic clutch 11a is turned on). I am doing so. By adjusting the temperature of the evaporator 9 by such frost prevention control of the compressor 11, the occurrence of frost in the evaporator 9 is suppressed.

  However, when the off-side target temperature TEO, which is a condition for stopping the operation of the compressor 11, is fixed to a preset reference temperature (for example, 1.5 ° C.), depending on the cooling heat load state of the evaporator 9, the evaporator 9 has a problem that frost is generated.

  As a countermeasure, if the off-side target temperature is increased according to the temperature change of the detected temperature of the evaporator after the operation of the compressor 11 is resumed, the compressor 11 is stopped for a long time when the cooling heat load is high. There is a problem that the air conditioning feeling of passengers in the passenger compartment deteriorates due to time.

  Therefore, the present inventors investigated changes in the detected temperature TE of the evaporator and changes in the behavior of the compressor 11 when the cooling heat load of the evaporator 9 was changed. Specifically, assuming the low heat load state where the cooling heat load of the evaporator 9 is low, such as in winter, and the high heat load state where the cooling heat load of the evaporator 9 is high, such as in summer, the evaporator 9 The air temperature on the suction side was investigated at a low temperature (for example, 10 ° C.) and a high temperature (for example, 30 ° C.).

  The results of this investigation will be described with reference to FIGS. Here, FIG. 2 shows changes in the detected temperature of the evaporator when the cooling heat load of the evaporator 9 is in a low heat load state (when the air temperature on the suction side of the evaporator 9 is lowered), and the compressor 11 The behavior is shown. FIG. 3 shows changes in the detected temperature of the evaporator and the behavior of the compressor 11 when the cooling heat load of the evaporator 9 is in a high heat load state (when the air temperature on the suction side of the evaporator 9 is set to a high temperature). Show.

  According to the investigation results, as shown in FIG. 2, when the cooling heat load of the evaporator 9 is in a low heat load state, the temperature change per unit time of the evaporator detected temperature TE after the operation of the compressor 11 is resumed. The rate tends to be large, that is, the cooling rate of the evaporator 9 tends to be fast.

  In addition, the behavior of the compressor 11 is such that the compressor 11 per cycle is defined as one control cycle (one cycle) from the stop of the operation of the compressor 11 through the restart of the operation to the stop of the operation again. The stop time tends to be longer than the operation time.

  That is, when the cooling heat load of the evaporator 9 is in a low heat load state, the time during which the evaporator detection temperature TE is equal to or lower than the off-side target temperature TEO is long, and the cooling speed of the evaporator 9 is also high. 11 is in a state where frost is likely to be generated in the evaporator 9 due to a delay in response after the stop of 11. Note that the low heat load state of the cooling heat load of the evaporator 9 corresponds to the first state of the cooling heat load of the evaporator 9 in the present invention.

  On the other hand, as shown in FIG. 3, when the cooling heat load of the evaporator 9 is in a high heat load state, the temperature change rate of the evaporator detected temperature TE after the restart of the operation of the compressor 11 is in a low heat load state. It tends to be smaller than the case, that is, the cooling rate of the evaporator 9 tends to be slow.

  Further, the behavior of the compressor 11 tends to be longer than the stop time of the compressor 11 per cycle. Furthermore, the temperature increase rate of the evaporator detection temperature TE after the compressor 11 is stopped tends to be higher than that in the low heat load state.

  That is, when the cooling heat load of the evaporator 9 is in a high heat load state, the time that the evaporator detection temperature TE is higher than the off-side target temperature TEO is long, and the cooling rate of the evaporator 9 is also slow. The evaporator 9 is in a state where frost is hardly generated. The high heat load state of the cooling heat load of the evaporator 9 corresponds to the second state of the cooling heat load of the evaporator 9 in the present invention.

  Here, according to the tendency of the investigation result, the low heat load state and the high heat load state of the cooling heat load of the evaporator 9 are the cooling rate of the evaporator 9 after the restart of the operation of the compressor 11 and the compressor 11 in one cycle. It is expected to be distinguishable by behavior.

  In order to confirm the effectiveness of the prediction of the cooling heat load of the evaporator 9 based on the result of this investigation, the inventors changed the air temperature on the suction side of the evaporator 9 between 10 ° C. and 35 ° C. The cooling rate of the evaporator 9 and the behavior of the compressor 11 in one cycle were verified.

  The verification result will be described with reference to FIGS. Here, FIG. 4 shows the relationship between the maximum value of the evaporator detection temperature TE at each air temperature on the suction side of the evaporator 9 and the cooling rate of the evaporator 9. FIG. 5 shows the relationship between the maximum value of the evaporator detection temperature TE and the ON / OFF ratio of the compressor 11 at each air temperature on the suction side of the evaporator 9. The ON / OFF ratio of the compressor 11 indicates the ratio between the operation time and the stop time when one cycle is from the stop of the operation of the compressor 11 through the restart of the operation to the stop of the operation again.

  According to the verification result, as shown in FIG. 4, the cooling rate in the low temperature region (low heat load state) where the air temperature on the suction side of the evaporator 9 is about 10 ° C. to 20 ° C., and the suction side of the evaporator 9 There is a region (mixed region in FIG. 4) in which the cooling rate in the high temperature region (high heat load state) where the air temperature is about 25 ° C. to 35 ° C. is mixed.

  That is, in this mixed region, it is estimated whether the cooling heat load of the evaporator 9 is in a low heat load state where the frost is easily generated in the evaporator 9 or a high heat load state where the frost is hardly generated in the evaporator 9. It has become difficult to do.

  On the other hand, as shown in FIG. 5, when the air temperature on the suction side of the evaporator 9 is in a low temperature region (low heat load state), the ON / OFF ratio of the compressor 11 tends to be small (in FIG. 3 or less).

  Further, when the air temperature on the suction side of the evaporator 9 is in a high temperature region (high heat load state), the ON / OFF ratio of the compressor 11 tends to be large (about 2 or more in FIG. 5). When the air temperature on the suction side of the evaporator 9 is an intermediate region (intermediate heat load state) where the air temperature is about 20 ° C. to 25 ° C., the ON / OFF ratio of the compressor 11 is an intermediate value (in FIG. 0.3-2).

  That is, in a low heat load state where the frost is likely to be generated in the evaporator 9, the frost is generated in the evaporator 9 with the ON / OFF ratio of the compressor 11 sandwiching the ON / OFF ratio of the compressor 11 in the intermediate heat load state. The value is smaller than the ON / OFF ratio of the compressor 11 in a high heat load state that is difficult to perform.

  Therefore, it can be said that the cooling heat load state of the evaporator 9 can be estimated by the behavior of the compressor 11 (for example, the ON / OFF ratio). In the control of the compressor 11, the cooling heat load state of the evaporator 9 is estimated according to the behavior of the compressor 11, so that the stop condition of the compressor 11 is turned off according to the estimated cooling heat load state. The side target temperature TEO can be set to an appropriate value.

  Next, the flow of compressor control according to this embodiment will be described with reference to FIG. FIG. 6 is a flowchart of compressor control executed by the microcomputer of the air conditioning controller 30.

  The compressor 11 is controlled by turning on the auto switch 42 when the ignition switch of the vehicle engine is turned on, initializing various counters and flags, detection signals from the sensor groups 30 to 35, various operation signals from the air conditioning panel 36, and the like. Start after loading.

  When the control of the compressor 11 is started, first, the electromagnetic clutch 11a of the compressor 11 is energized and turned on in step S10.

  Then, in step S20, it is determined whether or not the evaporator detected temperature TE, which is the detected value of the evaporator temperature sensor 34, is lower than the reference temperature. Here, the reference temperature is set to a temperature (for example, 1.5 ° C.) at which it is determined from experience that frost is unlikely to be generated in the evaporator 9, and is stored in advance in the ROM or the like of the air conditioning control device 30. The evaporator detection temperature TE is periodically detected by the evaporator temperature sensor 34.

  When it is determined in step S20 that the detected evaporator temperature TE is lower than the reference temperature, the process proceeds to step S30 and frost prevention control of the compressor 11 is performed. In addition, the control process of step 30 in this embodiment is equivalent to the frost prevention means of this invention.

  In the frost prevention control of the compressor 11, the operation of the compressor 11 is stopped when the evaporator detection temperature TE decreases to the off-side target temperature TEO as described above. After the operation of the compressor 11 is stopped, when the evaporator detection temperature TE becomes higher than the on-side target temperature (TEO + 1 ° C.) obtained by adding a predetermined hysteresis width (for example, 1 ° C.) to the off-side target temperature TEO, the compressor 11 is restarted. I am trying to start. The off-side target temperature TEO is set to a reference temperature as an initial value.

  And after implementing frost prevention control of compressor 11 at Step S30, it is judged at Step S40 whether the behavior of compressor 11 in frost prevention control passed one control cycle (one cycle). Here, the control cycle of the compressor 11 is set to one time from the stop of the operation of the compressor 11 to the stop of the operation again after the restart of the operation of the compressor 11 as described above.

  When it is determined in step S40 that the behavior of the compressor 11 has passed one cycle, the operation rate φ of the compressor 11 is calculated in step S50. In addition, the process of step S50 in this embodiment is corresponded to the operation rate calculation means of this invention.

The calculation of the operating rate φ of the compressor 11 is a ratio (compressor operating ratio) of the operating time ON-time of the compressor 11 in the time required for one cycle, and is calculated by the following formula F1.
φ = ON-time (n) / (ON-time (n) + OFF-time (n)) (F1)
However, OFF-time is the stop time of the compressor 11 in one cycle, and n is control sampling. Note that the operating rate φ of the compressor 11 corresponds to the ON / OFF ratio of the compressor, and the cooling heat load of the evaporator 9 can also be estimated by the operating rate φ of the compressor 11.

  Next, in step S60, the cooling rate K of the evaporator 9 after restarting the operation of the compressor 11 is calculated. In addition, the process of step S60 in this embodiment is equivalent to the cooling rate calculation means of this invention.

As shown in FIG. 7, the cooling rate K of the evaporator 9 is a temperature change rate of the evaporator detected temperature TE in the operation period from the operation restart (operation start) to the operation stop of the compressor 11 in one cycle. Specifically, the cooling rate K of the evaporator 9 is calculated by the following formula F2 based on the maximum value TEmax and the minimum value TEmin of the evaporator detection temperature TE and the operation time.
K = (TEmax (n) −TEmin (n)) / ON-time (n) (F2)
However, TEmax is the maximum value of the evaporator detection temperature TE during the operation period of the compressor 11 during one cycle, and TEmin is the minimum value of the evaporator detection temperature TE during the operation period of the compressor 11 during one cycle. FIG. 7 is an explanatory diagram for explaining a method for calculating the cooling rate of the evaporator 9. The cooling rate of the evaporator 9 corresponds to the gradient of the temperature change of the evaporator 9.

  Next, in step S70, it is determined whether or not the operation rate φ is equal to or less than the first reference value. The first reference value is set to a boundary value between the low heat load state and the intermediate heat load state of the cooling heat load of the evaporator 9 in the behavior (operating rate) of the compressor 11. It can be set to 0.25 corresponding to an OFF ratio of 0.3. The first reference value is stored in advance in the ROM or the like of the air conditioning control device 30.

  When the operation rate φ of the compressor 11 is equal to or less than the first reference value in step S70, it can be estimated that the cooling heat load of the evaporator 9 is in a low heat load state. Therefore, in step S80, the first off-side target temperature TEO1 that is a stop condition of the compressor 11 when the cooling heat load of the evaporator 9 is in a low load state is calculated.

  In step S80, the first off-side target temperature TEO1 is calculated based on the control map shown in FIG. FIG. 8A is a control characteristic diagram that defines the correspondence between the cooling rate of the evaporator 9 and the first off-side target temperature TEO1 when the cooling heat load of the evaporator 9 is in the low heat load state.

  Here, as described above, when the cooling heat load of the evaporator 9 is in the low heat load state and the cooling speed of the evaporator 9 is high, the frost is likely to be generated in the evaporator 9 as compared with other situations. It becomes. Therefore, in the present embodiment, the first off-side target temperature TEO1 is a reference temperature (for example, 1.5 ° C.) in proportion to the improvement of the cooling rate when the cooling rate of the evaporator 9 exceeds the first reference rate. The temperature is gradually raised from

  The first reference speed is calculated, for example, by an experiment or the like, and is stored in advance in the ROM or the like of the air conditioning control device 30. In order to prevent the first off-side target temperature TEO1 from becoming too high, an upper limit temperature (for example, 4.5 ° C.) is provided for the first off-side target temperature TEO1.

  In step S90, the first off-side target temperature TEO1 calculated in step S80 is set to the off-side target temperature TEO, and the process returns to the frost prevention control of the compressor 11 in step S30.

  Thus, when the evaporator 9 is in a low heat load state, such as in winter, and the cooling rate of the evaporator 9 is fast, the off-side target temperature TEO is set higher than a preset reference temperature. Thus, frost generation in the evaporator 9 can be more reliably prevented. In addition, when the cooling heat load of the evaporator 9 is a low load state, since the cooling capacity is excessive, deterioration of the occupant's air conditioning feeling due to the stop of the compressor 11 hardly occurs.

  When the operation rate φ of the compressor 11 is larger than the first reference value in step S70, the process proceeds to step S100, and it is determined whether or not the operation rate φ of the compressor 11 exceeds the second reference value. This second reference value is set to the boundary value between the intermediate heat load state and the high heat load state of the cooling heat load of the evaporator 9 in the behavior (operating rate) of the compressor 11. It can be set to 0.75 corresponding to an OFF ratio of 2. The second reference value is stored in advance in the ROM or the like of the air conditioning control device 30.

  When the operation rate φ of the compressor 11 is larger than the second reference value in step S100, it can be estimated that the cooling heat load of the evaporator 9 is in a high heat load state. Therefore, in step S110, a second off-side target temperature TEO2 that is a stop condition of the compressor 11 when the cooling heat load of the evaporator 9 is in a high heat load state is calculated.

  In step S110, the second off-side target temperature TEO2 is calculated based on the control map shown in FIG. FIG. 8B is a control characteristic diagram that defines the correspondence between the cooling rate of the evaporator 9 and the second off-side target temperature TEO2 when the cooling heat load of the evaporator 9 is in a high heat load state.

  As described above, when the cooling heat load of the evaporator 9 is in a high heat load state and the cooling speed of the evaporator 9 is low, it becomes difficult for the evaporator 9 to generate frost compared to other situations. . Therefore, the second off-side target temperature TEO2 is set to a temperature gradually decreased from the reference temperature in proportion to the decrease in the cooling rate when the cooling rate of the evaporator 9 is lower than the second reference rate. .

  The second reference speed is calculated, for example, by an experiment or the like, and is stored in advance in the ROM or the like of the air conditioning control device 30. In order to prevent the second off-side target temperature TEO2 from becoming too low, a lower limit temperature (for example, 0.5 ° C.) is provided for the second off-side target temperature TEO2.

  In step S120, the second off-side target temperature TEO2 calculated in step S110 is set to the off-side target temperature TEO, and the process returns to the frost prevention control of the compressor 11 in step S30.

  Thus, when the evaporator 9 is in a high heat load state, such as in summer, and the cooling rate of the evaporator 9 is slow, the off-side target temperature TEO is set to be lower than the reference temperature, so that the compressor 11 operation continuation time can be lengthened. Accordingly, it is possible to more effectively suppress the deterioration of the air conditioning feeling of the occupant due to the operation stop of the compressor 11. In addition, when the cooling heat load of the evaporator 9 is in a high load state, the air temperature on the suction side of the evaporator 9 is high and the cooling capacity is insufficient, so that the evaporator 9 hardly causes frost.

  Further, when the operation rate φ of the compressor 11 is equal to or lower than the second reference value in step S100, that is, when the operation rate φ of the compressor 11 is in the range of the first reference value to the second reference value, spring, autumn, etc. Thus, it can be estimated that the cooling heat load of the evaporator 9 is an intermediate heat load state in which the cooling heat load is relatively stable. Therefore, in step S120, a third off-side target temperature TEO3 that is a stop condition of the compressor 11 when the cooling heat load of the evaporator 9 is in the intermediate heat load state is calculated.

  In step S120, the third off-side target temperature TEO3 is calculated based on the control map shown in FIG. FIG. 8C is a control characteristic diagram that defines the correspondence between the cooling rate of the evaporator 9 and the third off-side target temperature TEO3 when the cooling heat load of the evaporator 9 is in the intermediate heat load state.

  Here, in the intermediate heat load state, since the frost is not easily generated in the evaporator 9 and the cooling heat load of the evaporator 9 is relatively stable, the third off-side target temperature TEO3 is equal to the evaporator 9 The reference temperature is used regardless of the cooling rate. When the cooling rate of the evaporator 9 is relatively fast, the third off-side target temperature TEO3 may be slightly raised.

  In step S140, the third off-side target temperature TEO3 calculated in step S130 is set to the off-side target temperature TEO, and the process returns to the frost prevention control of the compressor 11 in step S30.

  In addition, the determination process of step S70 and step S100 in this embodiment is equivalent to the cooling heat load estimation means of this invention, and the process of step S80, step S110, and step S130 is the off side target temperature (1st of this invention). This corresponds to temperature setting means for setting (set temperature).

  As described above, in the frost prevention control of the compressor 11 according to the present embodiment, the frost of the evaporator 9 is changed by changing the off-side target temperature according to the cooling heat load state estimated from the operating rate of the compressor 11. It is possible to achieve both prevention of occurrence and suppression of deterioration of the air conditioning feeling of the occupant.

  Further, in the present embodiment, the off-side target temperature is changed according to the cooling rate of the evaporator 9 in each cooling heat load state of the evaporator 9, and the frost generation of the evaporator 9 can be reliably prevented. At the same time, it is possible to more effectively suppress the deterioration of the air conditioning feeling of the passenger.

  Here, according to the frost prevention control of the compressor 11 of the present embodiment, the following secondary effects can be obtained. For example, by preventing the occurrence of frost in the evaporator 9, it is possible to prevent the generation of a strange odor accompanying the frost of water adhering to the evaporator surface. Further, when the cooling heat load of the evaporator 9 is in a high heat load state, a strange odor due to evaporation of water (water attached to the evaporator surface) due to a rapid temperature rise of the evaporator 9 when the operation of the compressor 11 is stopped. Occurrence can be suppressed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Parts that are the same as or equivalent to those in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the first embodiment described above, the cooling heat load state of the evaporator 9 is estimated based on the operating rate of the compressor 11, and the operation of the compressor 11 is performed according to the cooling rate of the evaporator 9 in the estimated cooling heat load state. The off-side target temperature TEO, which is a stop condition, is changed.

  In the present embodiment, the cooling heat load state of the evaporator 9 is estimated based on the operating rate of the compressor 11, and the off-side target temperature TEO that is the operation stop condition of the compressor 11 is changed according to the estimated cooling heat load state. To do. Specifically, in the present embodiment, the processes in steps S80 and S110 in FIG. 6 described in the first embodiment are different.

  In the present embodiment, in step S80 in FIG. 6, the first off-side target temperature TEO1 is set to an upper limit value (for example, 4.5 ° C.) regardless of the cooling rate of the evaporator 9. Thereby, in the low heat load state of the evaporator 9 which is easy to generate | occur | produce in the evaporator 9, the frost generation | occurrence | production of the evaporator 9 can be prevented.

  In step S110 in FIG. 6, the second off-side target temperature TEO1 is set to a lower limit value (for example, 0.5 ° C.) regardless of the cooling rate of the evaporator 9. Thereby, in the high heat load state of the evaporator 9 in which the frost is hardly generated in the evaporator 9, it is possible to suppress the deterioration of the air conditioning feeling of the occupant due to the stop of the operation of the compressor 11.

  Therefore, the frost prevention control of the compressor 11 according to the present embodiment can achieve both the prevention of the frost generation of the evaporator 9 and the suppression of the deterioration of the air conditioning feeling of the passengers in the passenger compartment.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows.

(1) In each of the above-described embodiments, the compressor operating ratio in the time required for one cycle is the operating rate φ of the compressor 11 (see Formula F1), but is not limited thereto. For example, the compressor operation ratio in the time required for one cycle may be calculated for a plurality of cycles, and the average value of the compressor operation ratios for the plurality of cycles may be used as the operation ratio of the compressor 11. For example, when calculating the average value of the compressor operation ratios for m cycles as the operation rate φ (n) of the compressor 11, it may be calculated by the following mathematical formula F3.
φ = {φ (n) + φ (n−1) +... + φ (n−m + 1)} / m (F3)
(2) In the first embodiment described above, the temperature change rate of the evaporator detection temperature TE during the operation period of the compressor 11 in one cycle is the cooling rate of the evaporator 9 (see Formula F2), but this is limited to this. Not. For example, the temperature change rate of the evaporator detection temperature TE during the operation period of the compressor 11 in one cycle is calculated for a plurality of cycles, and the average value of the temperature change rates of the evaporator detection temperatures TE for a plurality of cycles is calculated by the evaporator 9. It is good also as a cooling rate. For example, when the average value of the temperature change rate of the evaporator detection temperature TE for m cycles is calculated as the cooling rate K (n) of the evaporator 9, it may be calculated by the following formula F4.
K = {K (n) + K (n−1) +... + K (n−m + 1)} / m (F4)
(3) In the first embodiment described above, the first and second off-states are determined by the respective control maps that define the relationship between the cooling rate of the evaporator 9 and the first and second off-side target temperatures in step S80 and step 110. Although the side target temperature TEO is calculated, it is not limited to this. The first and second off-side target temperatures TEO may be calculated by, for example, mathematical formulas that define the relationship between the cooling rate of the evaporator 9 and the first and second off-side target temperatures based on experimental results and the like.

  The first off-side target temperature is raised in proportion to the improvement in the cooling rate of the evaporator 9 when a predetermined condition is satisfied, and the second off-side target temperature is the evaporator when the predetermined condition is satisfied. Although the temperature is decreased in proportion to the decrease in the cooling rate of 9, the present invention is not limited to this. For example, the first off-side target temperature is raised stepwise according to the cooling rate of the evaporator 9 when a predetermined condition is satisfied, and the second off-side target temperature is an evaporator when the predetermined condition is satisfied. Depending on the cooling rate of 9, the temperature may be lowered stepwise.

  (4) In each of the above-described embodiments, the cooling heat load state of the evaporator 9 is estimated based on the operating rate of the compressor 11. In addition to the operating rate of the compressor 11, vehicle information (engine speed, etc.) You may estimate in consideration of the driving | running state (Internal temperature, external temperature, solar radiation amount, compressor rotation speed, etc.) of a vehicle air conditioner.

  For example, when the rotation speed of the compressor 11 is high, the refrigerant compression capacity of the compressor 11 is increased, so that the evaporator 9 is likely to be frosted. Therefore, for example, when the low heat load state of the evaporator 9 is estimated (step S70), the operation rate of the compressor 11 is not more than the first reference value and the compressor speed is not less than a predetermined speed. Alternatively, it may be estimated that the cooling heat load of the evaporator 9 is in a low heat load state, and the off-side target temperature may be set to a high temperature.

  Further, when the outside air temperature is low, the cooling capacity of the condenser 12 becomes high, so that the evaporator 9 is likely to generate frost. Therefore, for example, when the low heat load state of the evaporator 9 is estimated, the cooling of the evaporator 9 is performed when the operating rate of the compressor 11 is not more than the first reference value and the outside air temperature is not more than a predetermined temperature. It may be estimated that the heat load is in a low heat load state.

  Further, when the amount of air blown to the evaporator 9 by the blower 8 is small and when the cooling rate of the evaporator 9 is high, the evaporator 9 is likely to be frosted. Therefore, for example, when determining the low heat load state of the evaporator 9, the operation rate of the compressor 11 is equal to or lower than the first reference value, the air flow rate of the blower 8 is equal to or less than a predetermined air flow rate, and the cooling rate of the evaporator 9 is When the speed is equal to or higher than the first reference speed, it may be estimated that the cooling heat load of the evaporator 9 is in a low heat load state.

  Here, the determination conditions for estimating the cooling heat load of the evaporator 9 include, in addition to the operating rate of the compressor 11, the cooling rate of the evaporator 9, the rotational speed of the compressor 11, the outside air temperature, It is good also as conditions which combined various conditions, such as blast volume. In addition, although the case where the evaporator 9 is in a low heat load state has been described, depending on the condition when the evaporator 9 is not estimated to be in a low heat load state, the condition when the evaporator 9 is in a high heat load state is set and the evaporator 9 The cooling heat load state may be estimated.

  (5) In each of the above-described embodiments, the evaporator temperature sensor 34 is disposed immediately after the air blowing portion of the evaporator 9 to detect the evaporator blowing temperature, but the evaporator temperature sensor 34 is disposed on the surface of the evaporator 9. It is also possible to detect the evaporator surface temperature by disposing it.

  (6) In each of the above-described embodiments, the example in which the fixed capacity type compressor is adopted as the compressor 11 has been described. However, the present invention is not limited to this. As the compressor 11, for example, a variable capacity compressor capable of changing the discharge capacity of the compressor 11 or an electric compressor including a compression mechanism driven by an electric motor can be employed. When a variable displacement compressor not provided with an electromagnetic clutch is employed, the discharge capacity of the compressor 11 is substantially zero when the evaporator detected temperature TE is equal to or lower than the off-side target temperature TEO. What is necessary is just to perform control.

1 is an overall system configuration diagram of a vehicle air conditioner according to an embodiment. It is explanatory drawing explaining the evaporator detection temperature in case a cooling heat load is a low heat load state, and the behavior of a compressor. It is explanatory drawing explaining the evaporator detection temperature and the behavior of a compressor in case a cooling heat load is a high heat load state. It is explanatory drawing explaining the relationship between the cooling heat load state and the cooling rate of an evaporator. It is explanatory drawing explaining the relationship between the cooling heat load state and the behavior of a compressor. It is a flowchart which shows the flow of the compressor control which concerns on embodiment. It is explanatory drawing for demonstrating the calculation method of the cooling rate of an evaporator. It is a control characteristic figure which defined the correspondence of the cooling rate of an evaporator, and each off side target temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Evaporator 10 Refrigeration cycle 11 Compressor 30 Air-conditioning control apparatus 34 Evaporator temperature sensor (evaporator temperature detection means)

Claims (5)

A refrigerating cycle (10) for cooling the air discharged from the compressor (11) in the evaporator (9) by evaporating the refrigerant discharged from the compressor (11);
An evaporator temperature detecting means (34) for detecting a blown air temperature or an evaporator surface temperature of the evaporator (9);
When the detected value detected by the evaporator temperature detecting means (34) falls below a first preset temperature that is initially set to a preset reference temperature, the operation of the compressor (11) is stopped and the first Frost prevention control means for executing control to resume the operation of the compressor (11) when the second predetermined temperature set higher than the set temperature is exceeded,
Temperature setting means for setting the first set temperature;
The compressor (11) based on the stop time of the compressor (11) when the operation of the compressor (11) is controlled by the frost prevention control means and the operation time of the compressor (11). An operation rate calculating means for calculating the operation rate of
A cooling heat load estimating means for estimating a cooling heat load state of the evaporator (9) based on the operating rate calculated by the operating rate calculating means,
When the cooling heat load estimation means estimates that the cooling heat load state of the evaporator (9) is a first state in which frost is likely to occur in the evaporator (9), the temperature setting means is The preset temperature is set to a temperature higher than the reference temperature, and the cooling heat load estimation means estimates that the cooling heat load state of the evaporator (9) is the second state in which frost is unlikely to occur in the evaporator (9). In this case, the vehicle air conditioner is characterized in that the first set temperature is set to a temperature lower than the reference temperature. The temperature deviation between the maximum value and the minimum value of the detected value of the evaporator temperature detection means (34) in the operation period from the start to the stop of the operation of the compressor (11), and the compressor (11) in the operation period Cooling rate calculation means () for calculating the cooling rate of the evaporator (9) based on the operation time of
The temperature setting means includes
The cooling heat load state of the evaporator (9) is estimated as the first state by the cooling heat load estimation unit, and the cooling rate calculated by the cooling rate calculation unit is based on a preset first reference speed. The first set temperature is set to a higher temperature than when the speed is slower than the first reference speed,
The cooling heat load state of the evaporator (9) is estimated to be the second state by the cooling heat load estimation unit, and the cooling rate calculated by the cooling rate calculation unit is based on a preset second reference speed. 2. The vehicle air conditioner according to claim 1, wherein the first set temperature is set to a lower temperature when the speed is slower than when the speed is higher than the second reference speed. The cooling heat load estimating means includes
When the operating rate falls below a preset first reference value, the cooling heat load state of the evaporator (9) is estimated as the first state,
The cooling heat load state of the evaporator (9) is estimated as the second state when the operating rate exceeds a second reference value set to a value higher than the first reference value. The vehicle air conditioner according to claim 1 or 2.   When the period from the stop of the operation of the compressor (11) to the resumption of operation after restarting the operation is defined as one cycle, the operating rate calculating means is configured to include the compressor in the time required for the one cycle. The vehicle air conditioner according to any one of claims 1 to 3, wherein the compressor operating ratio occupied by the operating time of (11) is calculated as the operating rate.   When the period from the stop of the operation of the compressor (11) to the resumption of operation after restarting the operation is defined as one cycle, the operating rate calculating means is configured to include the compressor in the time required for the one cycle. 4. The compressor operating ratio occupying the operating time of (11) is calculated for a plurality of cycles, and an average value of the calculated compressor operating ratios for the plurality of cycles is calculated as the operating ratio. The vehicle air conditioner as described in any one.

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