Patent Description:
An air conditioning apparatus is known which, at the start of a heating operation, sets high an upper limit air volume of a fan with respect to a heat exchanger temperature and which, when stable, sets low the upper limit air volume of the fan (see <CIT>).

<CIT> discloses an air conditioning apparatus forming the basis of the preamble of independent claims <NUM> and <NUM>.

There are cases where this type of air conditioning apparatus has, as a heating function, a hot air mode that blows out hot air that is higher in temperature than in the typical heating mode. In a case where the operating mode has been switched from the hot air mode to the normal heating mode, there are cases where the rotational speed of the fan suddenly decreases. When the rotational speed of the fan suddenly decreases, the temperature of the condenser increases. At this time, when the temperature of the condenser increases too much, that is, when the refrigerant pressure increases too much, the compressor ends up stopping. It will be noted that the same problem can happen not only in a case where the operating mode has been switched from the hot air mode to the normal heating mode but also in a case where the operating mode has been switched from the normal heating mode to the hot air mode.

It is an object of the present invention to provide an air conditioning apparatus that suppresses an excessive increase in refrigerant pressure.

This object is solved by means of an air conditioning apparatus according to independent claim <NUM> or <NUM>. Distinct embodiments are derivable from dependent claim <NUM>.

In the air conditioning apparatus pertaining to the present invention, an excessive increase in the refrigerant temperature in the indoor heat exchanger can be suppressed.

An embodiment of the invention will be described below. It will be noted that the following embodiment is merely a specific example and is not intended to limit the invention which is defined by the claims.

<FIG> is a drawing describing an example of the configuration of an air conditioning apparatus <NUM>. The air conditioning apparatus <NUM> includes an air conditioning outdoor unit <NUM> serving as a heat source-side unit and an air conditioning indoor unit <NUM> serving as a utilization-side unit. The air conditioning outdoor unit <NUM> and the air conditioning indoor unit <NUM> are connected to each other via a refrigerant communication pipe <NUM> for liquid refrigerant and a refrigerant communication pipe <NUM> for gas refrigerant.

A refrigerant circuit of the air conditioning apparatus <NUM> is configured by the air conditioning outdoor unit <NUM>, the air conditioning indoor unit <NUM>, the refrigerant communication pipe <NUM>, and the refrigerant communication pipe <NUM>. More specifically, the refrigerant circuit includes an expansion valve <NUM>, a compressor <NUM>, a four-port switching valve <NUM>, an accumulator <NUM>, an outdoor heat exchanger <NUM>, and an indoor heat exchanger <NUM>.

The air conditioning indoor unit <NUM> has the indoor heat exchanger <NUM> and an indoor fan <NUM>. The indoor heat exchanger <NUM> is, for example, a cross-fin type fin-and-tube heat exchanger configured by heat transfer tubes and numerous fins. The indoor heat exchanger <NUM> functions as an evaporator of the refrigerant in a cooling operation to cool room air and functions as a condenser of the refrigerant in a heating operation to heat room air. That is, the indoor heat exchanger <NUM> generates conditioned air by exchanging heat between the refrigerant and the room air. The generated conditioned air is blown out from an air outlet (not shown in the drawings) in the air conditioning indoor unit <NUM>. The indoor fan <NUM> is connected to a fan motor <NUM> (see <FIG>). When the indoor fan <NUM> rotates because of the driving of the fan motor <NUM>, the air in the room is supplied to the indoor heat exchanger <NUM>.

The air conditioning outdoor unit <NUM> has a gas refrigerant pipe <NUM>, a liquid refrigerant pipe <NUM>, the expansion valve <NUM>, the compressor <NUM>, the four-port switching valve <NUM>, the accumulator <NUM>, the outdoor heat exchanger <NUM>, and an outdoor fan <NUM>. One end of the gas refrigerant pipe <NUM> is connected to a gas-side end portion of the outdoor heat exchanger <NUM>, and the other end of the gas refrigerant pipe <NUM> is connected to the four-port switching valve <NUM>. One end of the liquid refrigerant pipe <NUM> is connected to a liquid-side end portion of the outdoor heat exchanger <NUM>, and the other end of the liquid refrigerant pipe <NUM> is connected to the expansion valve <NUM>.

The expansion valve <NUM> is a mechanism that reduces the pressure of the refrigerant. The expansion valve <NUM> is provided between the outdoor heat exchanger <NUM> and the refrigerant communication pipe <NUM>. The compressor <NUM> is a closed compressor driven by a compressor motor.

The four-port switching valve <NUM> is a mechanism that switches the direction in which the refrigerant flows. In the cooling operation, as indicated by the solid lines of the four-port switching valve <NUM> in <FIG>, the four-port switching valve <NUM> interconnects a refrigerant pipe on the discharge side of the compressor <NUM> and the gas refrigerant pipe <NUM> and interconnects, via the accumulator <NUM>, a refrigerant pipe on the intake side of the compressor <NUM> and the refrigerant communication pipe <NUM>. On the other hand, in the heating operation, as indicated by the dashed lines of the four-port switching valve <NUM> in <FIG>, the four-port switching valve <NUM> interconnects the refrigerant pipe on the discharge side of the compressor <NUM> and the refrigerant communication pipe <NUM> and interconnects, via the accumulator <NUM>, the refrigerant pipe on the intake side of the compressor <NUM> and the gas refrigerant pipe <NUM>.

The accumulator <NUM> separates the refrigerant into its gas phase and its liquid phase. The accumulator <NUM> is provided between the compressor <NUM> and the four-port switching valve <NUM>.

The outdoor heat exchanger <NUM> functions as a condenser of the refrigerant in the cooling operation and functions as an evaporator of the refrigerant in the heating operation. The outdoor fan <NUM> supplies air to the outdoor heat exchanger <NUM>.

The opening degree of the expansion valve <NUM> is adjusted in such a way that the degree of superheating of the refrigerant at the outlet of the indoor heat exchanger <NUM> (that is, the gas side of the indoor heat exchanger <NUM>) becomes constant. The state of connection of the four-port switching valve <NUM> in the cooling operation is as has already been described.

In the refrigerant circuit in the state described above, the refrigerant that has been discharged from the compressor <NUM> travels through the four-port switching valve <NUM>, flows into the outdoor heat exchanger <NUM>, radiates heat to the outdoor air, and condenses. The refrigerant that has flowed out from the outdoor heat exchanger <NUM> expands when it travels through the expansion valve <NUM>. Thereafter, the refrigerant flows into the indoor heat exchanger <NUM>, absorbs heat from the room air, and evaporates.

The opening degree of the expansion valve <NUM> is adjusted in such a way that the degree of subcooling of the refrigerant at the outlet of the indoor heat exchanger <NUM> becomes constant at a degree of subcooling target value. The state of connection of the four-port switching valve <NUM> in the heating operation is as has already been described.

In the refrigerant circuit in the state described above, the refrigerant that has been discharged from the compressor <NUM> travels through the four-port switching valve <NUM>, flows into the indoor heat exchanger <NUM>, radiates heat to the room air, and condenses. The refrigerant that has flowed out from the indoor heat exchanger <NUM> expands when it travels through the expansion valve <NUM>. Thereafter, the refrigerant flows into the outdoor heat exchanger <NUM>, absorbs heat from the outdoor air, and evaporates. The refrigerant that has flowed out from the outdoor heat exchanger <NUM> travels through the four-port switching valve <NUM> and thereafter is sucked back into the compressor <NUM> and compressed.

<FIG> is a drawing describing an example of functional blocks of the air conditioning indoor unit <NUM>. The air conditioning indoor unit <NUM> includes a control unit <NUM>, a temperature sensor <NUM>, and a remote controller <NUM> in addition to the fan motor <NUM>.

The control unit <NUM> is a computer configured from an MPU, a ROM, and a RAM. Various types of threshold values used in a later-described flowchart, and a later-described lower limit rotational speed, are stored beforehand in the ROM. The control unit <NUM> is electrically connected to the temperature sensor <NUM> and the fan motor <NUM>.

The control unit <NUM> fulfills a role as a setting unit that sets operating modes on the basis of a later-described command signal. The operating modes include a normal heating mode serving as an example of a first heating mode and a hot air mode serving as an example of a second heating mode. That is, the air conditioning apparatus <NUM> has, as heating functions, a normal heating mode and a hot air mode. The outgoing air temperature in the hot air mode is higher than the outgoing air temperature in the normal heating mode. That is, in the hot air mode, conditioned air higher in temperature than in the normal heating mode is generated. The operating modes further include a fan mode and a cooling mode.

The control unit <NUM> acquires an output value of the temperature sensor <NUM> from the temperature sensor <NUM>. The control unit <NUM> controls the rotational speed of the indoor fan <NUM> on the basis of the acquired output value. That is, the control unit <NUM> controls the fan motor <NUM>. Although details will be described later, in a case where the operating mode has been switched from the hot air mode to the normal heating mode, the control unit <NUM> sets a lower limit value of the rotational speed if the acquired output value is larger than a preset threshold value. Because of this, the control unit <NUM> decreases the rotational speed of the indoor fan <NUM> in stages.

The temperature sensor <NUM> detects the indoor heat exchanger temperature serving as an example of a value relating to refrigerant pressure. The indoor heat exchanger temperature is the temperature in the two-phase region of the indoor heat exchanger <NUM>. The temperature sensor <NUM> sends the detected indoor heat exchanger temperature to the control unit <NUM>.

The remote controller <NUM> sends command signals to the control unit <NUM> by infrared on the basis of user operations. The command signals include a command signal relating to the setting of the operating mode. The user can set the operating mode of the air conditioning indoor unit <NUM> by operating the remote controller <NUM>.

<FIG> is a drawing describing switching between the normal heating mode and the hot air mode. As has already been described, the air conditioning apparatus <NUM> has, as heating functions, the normal heating mode and the hot air mode. In a case where the operating mode is set to the hot air mode, the air conditioning indoor unit <NUM> switches from the hot air mode to the normal heating mode if there is a request from the user to switch off the function of the hot air mode. Furthermore, the air conditioning indoor unit <NUM> switches from the hot air mode to the normal heating mode also in a case where a preset amount of time has elapsed since the operating mode was set to the hot air mode.

<FIG> is a drawing describing rates of decrease in the rotational speed of the indoor fan <NUM>. The horizontal axis represents time and the vertical axis represents the rotational speed of the indoor fan <NUM>.

In graph g1, the rotational speed of the indoor fan <NUM> decreases linearly downward to the right from a current rotational speed RCUR to a target rotational speed RRE. That is, the rotational speed of the indoor fan <NUM> monotonically decreases as a linear function. In graph g1, a period of time t5 - time t1 is needed until the rotational speed of the indoor fan <NUM> decreases from the current rotational speed RCUR to the target rotational speed RRE. That is, the rate of decrease in the rotational speed serving as a first rate is (RCUR - RRE) / (t5 - <NUM>). In a case where the operating mode is set to the normal heating mode, the rotational speed of the indoor fan <NUM> is lowered at the first rate as shown in graph g1.

In graph g2, the rotational speed of the indoor fan <NUM> does not monotonically decrease as a linear function but decreases from the current rotational speed RCUR to the target rotational speed RRE while alternating between decrease intervals dec and maintain intervals mt. That is, the rotational speed of the indoor fan <NUM> decreases in stages. Although details will be described later, by appropriately setting a lower limit value of the rotational speed, that is, by providing the maintain intervals mt, a situation where the rotational speed monotonically decreases as a linear function is avoided. The decrease intervals dec are intervals in which the rotational speed of the indoor fan <NUM> decreases, and the maintain intervals mt are intervals in which the rotational speed of the indoor fan <NUM> is maintained.

In the present embodiment, the rotational speed of the indoor fan <NUM> first decreases from the current rotational speed RCUR to a first lower limit rotational speed RLIM1 from time t1 to time t2. The first lower limit rotational speed RLIM1 is a rotational speed at a particular fan tap. The first lower limit rotational speed RLIM1 is preset as a sufficiently allowed rotational speed from the standpoint of avoiding stopping of the compressor <NUM>. Thereafter, the rotational speed of the indoor fan <NUM> alternates between the maintain intervals mt and the decrease intervals dec. More specifically, the intervals of the rotational speed of the indoor fan <NUM> are a maintain interval mt from time t2 to time t3 and a decrease interval dec from time t3 to time t4. From time t4 to time t6 is a maintain interval mt, and from time t6 to time t7 is a decrease interval dec. From time t7 to time t8 is a maintain interval mt, and from time t8 to time t9 is a decrease interval dec.

In each decrease interval dec in the alternating intervals, the rotational speed of the indoor fan <NUM> decreases a second lower limit rotational speed at a time. It will be noted that, in <FIG>, the drop from the current rotational speed RCUR to the first lower limit rotational speed is smaller than the drop at each decrease interval dec in the alternating intervals.

In graph g2, a period of time t9 - time t1 is needed until the rotational speed of the indoor fan <NUM> decreases from the current rotational speed RCUR to the target rotational speed RRE. That is, as shown in graph g3, the overall rate of decrease in the rotational speed serving as a second rate is (RCUR - RRE) / (t9 - <NUM>).

As will be understood from graph g1 and graph g3, the second rate is slower than the first rate. Furthermore, the rate in each decrease interval dec in graph g2 is the same as the first rate.

<FIG> is a drawing showing an example of a flowchart of processing for setting the lower limit value of the rotational speed of the indoor fan <NUM>. The flowchart is started in the case where the operating mode has been switched from the hot air mode to the normal heating mode. In the flowchart, variable TEMh represents the indoor heat exchanger temperature. Constant TEMth represents the threshold value of the indoor heat exchanger temperature. Variable RFLIM represents the lower limit value of the rotational speed of the indoor fan <NUM>. Constant RFLIM1 represents the first lower limit rotational speed. Constant RFLIM2 represents the second lower limit rotational speed. Constant RFRE represents the target rotational speed. The target rotational speed is, for example, the rotational speed in the normal heating mode just before the operating mode is switched to the hot air mode. Variable TIM represents a count value of a timer. Constant TIMth represents a threshold value of the timer.

When the operating mode is switched from the hot air mode to the normal heating mode, the control unit <NUM> determines whether variable TEMh is greater than constant TEMth (step S101). That is, the control unit <NUM> determines whether the indoor heat exchanger temperature is greater than the preset threshold value.

In a case where the control unit <NUM> has determined that variable TEMh is greater than constant TEMth (YES in step S101), the control unit <NUM> assigns constant RFLIM1 to variable RFLIM (step S102). That is, the control unit <NUM> sets the lower limit value of the rotational speed of the indoor fan <NUM> to the first lower limit rotational speed. Thereafter, the control unit <NUM> lowers the lower limit value of the rotational speed of the indoor fan <NUM> every certain amount of time. That is, the control unit <NUM> lowers the lower limit value of the rotational speed of the indoor fan <NUM> in stages. Because of this, the control unit <NUM> lowers the rotational speed at the second rate that is slower than the first rate. Specifically, the control unit <NUM> accomplishes this as follows.

First, the control unit <NUM> starts the timer (step S103). Next, the control unit <NUM> determines whether or not variable TIM is equal to or greater than constant TIMth (step S104). In a case where the control unit <NUM> has determined that variable TIM is less than constant TIMth (NO in step S104), the control unit <NUM> stands by. On the other hand, in a case where the control unit <NUM> has determined that variable TIM is equal to or greater than constant TIMth (YES in step S104), the control unit <NUM> assigns to variable RFLIM a new value obtained by subtracting constant RFLIM2 from variable RFLIM (step S105). That is, the control unit <NUM> lowers the lower limit value of the rotational speed of the indoor fan <NUM> by constant RFLIM2.

The control unit <NUM> determines whether or not variable RFLIM is equal to or less than constant RFRE (step S106). That is, the control unit <NUM> determines whether or not the lower limit value of the rotational speed of the indoor fan <NUM> has reached the target rotational speed. In a case where variable RFLIM is greater than constant RFRE (NO in step S106), the control unit <NUM> resets the timer (step S107) and returns to step S103. In a case where the control unit <NUM> has determined that variable RFLIM is equal to or less than constant RFRE, the control unit <NUM> ends the series of processes. Furthermore, also in a case where the control unit <NUM> has determined in step S101 that variable TEMh is equal to or less than constant TEMth (NO in step S101), the control unit <NUM> ends the series of processes without performing the lower limit value setting processing. In this case, it suffices to decrease the rotational speed of the indoor fan <NUM> at the first rate.

In the air conditioning apparatus <NUM> of the present embodiment, in the case where the operating mode has been switched from the hot air mode to the normal heating mode, the control unit <NUM> does not lower the rotational speed at the first rate but lowers the rotational speed at the second rate that is slower than the first rate. Because of this, an excessive increase in the refrigerant temperature in the indoor heat exchanger <NUM> can be suppressed.

In the air conditioning apparatus <NUM> of the present embodiment, in the case where the operating mode has been switched from the hot air mode to the normal heating mode, the control unit <NUM> controls the rotational speed on the basis of the indoor heat exchanger temperature. Specifically, first, the control unit <NUM> determines whether or not the indoor heat exchanger temperature is greater than the preset threshold value. Then, in a case where the indoor heat exchanger temperature is greater than the preset threshold value, the control unit <NUM> lowers the rotational speed at the second rate. In a case where the indoor heat exchanger temperature is equal to or less than the preset threshold value, the control unit <NUM> lowers the rotational speed at the first rate. The control unit <NUM> controls the rotational speed on the basis of the indoor heat exchanger temperature, so the rotational speed can be lowered at a rate suited to the refrigerant pressure.

In the air conditioning apparatus <NUM> of the present embodiment, the control unit <NUM> lowers the rotational speed at the second rate if the output value of the temperature sensor <NUM> serving as the indoor heat exchanger temperature is higher than the threshold value. Consequently, the air conditioning apparatus <NUM> does not need to be equipped with a pressure sensor.

In the air conditioning apparatus <NUM> of the present embodiment, the control unit <NUM> lowers the rotational speed to the target rotational speed at the second rate overall by alternating between intervals in which it maintains the rotational speed and intervals in which it lowers the rotational speed. Because of this, a simplification of control by a program can be expected.

Example modifications applicable to the embodiment of the present invention will be described.

In the above description, the air conditioning apparatus <NUM> was equipped with the temperature sensor <NUM>, but according to the alternative embodiment of appended claim <NUM>, the air conditioning apparatus <NUM> is equipped with a pressure sensor instead of the temperature sensor <NUM> or in addition to the temperature sensor <NUM>. The pressure sensor detects the refrigerant pressure on the discharge side of the compressor <NUM>. The control unit <NUM> acquires an output value of the pressure sensor. Additionally, the control unit <NUM> controls the fan motor <NUM> in accordance with the acquired output value.

In the case where the operating mode has been switched from the hot air mode to the normal heating mode, the control unit <NUM> may also set the lower limit value of the rotational speed if the acquired output value is greater than a preset threshold value. Because of this, the rotational speed of the indoor fan <NUM> can be decreased in stages, so the rotational speed of the indoor fan <NUM> can be decreased at the second rate. In this case, for example, the flowchart described in <FIG> can be applied. In a case where the control unit <NUM> controls the fan motor <NUM> in accordance with the output value of the pressure sensor, the rotational speed of the indoor fan <NUM> can be controlled with even higher precision.

In the above description, the rate in each decrease interval dec in the graph g2 of <FIG> was the same as the first rate, but it does not need to be the same as the first rate. For example, the rate may also be slower than the first rate. Because of this, an excessive increase in the refrigerant temperature in the indoor heat exchanger <NUM> can be suppressed even more.

In the above description, the control unit <NUM> lowered the rotational speed of the indoor fan <NUM> at the second rate by lowering the rotational speed of the indoor fan <NUM> in stages, but the control unit <NUM> does not need to lower the rotational speed in stages. For example, as indicated by graph g3 in <FIG>, the control unit <NUM> may also monotonically decrease the rotational speed of the indoor fan <NUM> as a linear function.

The drop from the current rotational speed RCUR to the first lower limit rotational speed may also be appropriately set in accordance with the current rotational speed RCUR. Furthermore, the drop from the current rotational speed RCUR to the first lower limit rotational speed may also be the same as the drop at each decrease interval dec in the alternating intervals, or may also be larger than the drop at each decrease interval dec in the alternating intervals.

The example modification E does not correspond to an embodiment that falls under the scope of the claims.

In <FIG>, the control unit <NUM> ended the series of processes in a case where the control unit <NUM> determined that variable RFLIM is equal to or less than constant RFRE (YES in step S106) or determined in step S101 that variable TEMh is equal to or less than constant TEMth. However, the control unit <NUM> may also, even if these conditions are not met, end the series of processes in a case where the compressor <NUM> has stopped. For example, the compressor <NUM> stops in a case where the operating mode has been switched to the fan mode or the cooling mode. Consequently, the control unit <NUM> may also end the series of processes in a case where the operating mode has been switched to the fan mode or the cooling mode. That is, the control unit <NUM> may also cancel the setting of the lower limit value.

It should be noted that the execution order of processes such as operations, procedures, steps, and stages in a device, program, and method described in the claims, specification, and drawings can be realized in an arbitrary order unless expressions such as "before" and "preceding" are clearly indicated or in a case where the output of a previous process is used in a subsequent process. Even if an operational flow in the claims, specification, and drawings is described using expressions such as "first" and "next" for the sake of convenience, this does not mean that the operational flow must be implemented in this order. intervals, or may also be larger than the drop at each decrease interval dec in the alternating intervals.

The example modification F does not correspond to an embodiment that falls under the scope of the claims.

In the above description, a case where the operating mode was switched from the hot air mode to the normal heating mode was given as an example, but the control unit <NUM> may lower the rotational speed of the indoor fan <NUM> at the second rate also in a case where the operating mode has been switched from the normal heating mode to the hot air mode. In this case also, the flowchart shown in <FIG> can be applied. That is, the flowchart shown in <FIG> can be applied to a case where the operating mode has been switched from one to the other of the hot air mode and the normal heating mode.

The example modification G does not correspond to an embodiment that falls under the scope of the claims.

Claim 1:
An air conditioning apparatus (<NUM>) comprising:
an indoor fan (<NUM>);
an indoor heat exchanger (<NUM>) that is configured to generate heated air by exchanging heat between refrigerant and room air either in a normal heating mode or in a hot air mode,
wherein a temperature of outgoing air in the hot air mode is higher than the temperature of the outgoing air in the normal heating mode;
a condenser (<NUM>);
a setting unit (<NUM>) that is configured to set the hot air mode or the normal heating mode as operating modes; and
a control unit (<NUM>) that is configured to control a rotational speed of the indoor fan(<NUM>) based on the setting of the hot air mode or the normal heating mode,
characterized in that
the air conditioner further comprises a temperature sensor (<NUM>) that detects the temperature of the condenser,
and wherein in a case where the operating mode is the normal heating mode, the control unit can lower the rotational speed of the indoor fan (<NUM>) at a first rate, and
in a case where the operating mode has been switched from the hot air heating mode to the normal heating mode, the control unit is configured to lower the rotational speed of the indoor fan (<NUM>) at a second rate, which is slower than the first rate,
if an output value of the temperature sensor is higher than a preset threshold value.