Vehicle air conditioner

1. A vehicle air conditioner to condition air of a vehicle interior, including a refrigerant circuit having a compressor to compress a refrigerant, a radiator to let the refrigerant radiate heat, a pressure reducing unit, and a heat absorber to let the refrigerant absorb heat, comprising:

a control device to control the compressor,

wherein the control device holds normal time data indicating a relation between a number of revolutions NC of the compressor and a discharge refrigerant temperature Td in a normal time at which an amount of the refrigerant is filled in the refrigerant circuit,

wherein the control device calculates a discharge refrigerant temperature estimated value Tdst, where Tdst is an estimated value of the discharge refrigerant temperature Td in the normal time from the normal time data on the basis of the number of revolutions NC at present, and

wherein the control device compares the discharge refrigerant temperature estimated value Tdst and the discharge refrigerant temperature Td at present to thereby determine a lack of refrigerant in the refrigerant circuit.

2. The vehicle air conditioner according to claim 1 , wherein the normal time data is data indicating a relation between the number of revolutions NC, a discharge refrigerant pressure Pd of the compressor, and the discharge refrigerant temperature Td in the normal time.

3. The vehicle air conditioner according to claim 1 , wherein the normal time data is a multiple regression formula in which the discharge refrigerant temperature estimated value Tdst is assumed to be a target variable, and the number of revolutions NC and the discharge refrigerant pressure Pd of the compressor are assumed to be explanation variables.

4. A vehicle air conditioner to condition air of a vehicle interior, including a refrigerant circuit having a compressor to compress a refrigerant, a radiator to let the refrigerant radiate heat, a pressure reducing unit, and a heat absorber to let the refrigerant absorb heat, comprising:

a control device to control the compressor,

wherein the control device holds normal time data indicating a relation between a number of revolutions NC of the compressor and a discharge refrigerant pressure Pd in a normal time at which an of the refrigerant is filled in the refrigerant circuit,

wherein the control device calculates a discharge refrigerant pressure estimated value Pdst, where Pdst is an estimated value of the discharge refrigerant pressure Pd in the normal time from the normal time data on the basis of the number of revolutions NC at present, and

wherein the control device compares the discharge refrigerant pressure estimated value Pdst and the discharge refrigerant pressure Pd at present to thereby determine a lack of refrigerant in the refrigerant circuit.

5. The vehicle air conditioner according to claim 4 , wherein the normal time data is data indicating a relation between the number of revolutions NC, the discharge refrigerant temperature Td of the compressor, and the discharge refrigerant pressure Pd in the normal time.

6. The vehicle air conditioner according to claim 4 , wherein the normal time data is a multiple regression formula in which the discharge refrigerant pressure estimated value Pdst is assumed to be a target variable, and the number of revolutions NC and the discharge refrigerant temperature Td of the compressor are assumed to be explanation variables.

7. The vehicle air conditioner according to claim 1 , wherein when the control device decides that there is a doubt about the lack of refrigerant in the refrigerant circuit, the control device lowers a capability of the compressor.

8. The vehicle air conditioner according to claim 7 , wherein after the capability of the compressor is lowered, the control device determines the occurrence of the lack of refrigerant in the refrigerant circuit on a condition that a difference between the discharge refrigerant temperature estimated value Tdst and the discharge refrigerant temperature Td at present, or a condition that a difference between the discharge refrigerant pressure estimated value Pdst and the discharge refrigerant pressure Pd at present becomes larger.

9. The vehicle air conditioner according to claim 1 , wherein when the control device decides that there is a doubt about a lack of refrigerant in the refrigerant circuit, the control device narrows down a usage band of the number of revolutions NC of the compressor and in that state, compares again the discharge refrigerant temperature estimated value Tdst and the discharge refrigerant temperature Td at present, or compares again the discharge refrigerant pressure estimated value Pdst and the discharge refrigerant pressure Pd at present to determine the occurrence of the lack of refrigerant in the refrigerant circuit.

10. The vehicle air conditioner according to claim 9 , wherein in a state in which the control device narrows down the usage band of the number of revolutions NC of the compressor, the control device determines the occurrence of the lack of refrigerant in the refrigerant circuit while the difference between the discharge refrigerant temperature estimated value Tdst and the discharge refrigerant temperature Td at present, or the difference between the discharge refrigerant pressure estimated value Pdst and the discharge refrigerant pressure Pd at present is smaller.

11. The vehicle air conditioner according to claim 8 , wherein when the control device determines the occurrence of the lack of refrigerant in the refrigerant circuit, the control device executes a predetermined notifying operation.

12. The vehicle air conditioner according to claim 8 , wherein when the control device determines the occurrence of the lack of refrigerant in the refrigerant circuit, the control device lowers the number of revolutions NC of the compressor or stops the compressor.