Heat pump for a motor vehicle and a method of operating the heat pump

Abstract

A method for operating a heat pump of a motor vehicle that includes a compressor, an expander, an ambient heat exchanger and a heating heat exchanger. In the method, a defrost mode for defrosting the ambient heat exchanger is initiated. In the defrost mode, a refrigerant is compressed to a high pressure by the compressor to transfer thermal energy to the ambient heat exchanger, the refrigerant is expanded to a low pressure by the expander, and the refrigerant absorbs thermal energy in the heating heat exchanger. Further, a defrosting process of the ambient heat exchanger triggered by the defrost mode is monitored. The monitoring of the defrosting process includes monitoring the pressure difference between the high pressure and the low pressure and/or monitoring the pressure gradient of the pressure difference between the high pressure and the low pressure and/or monitoring the high pressure.

Claims

1. A method for operating a heat pump of a motor vehicle, the heat pump comprises a compressor, an expander, an ambient heat exchanger, and a heating heat exchanger, the method comprising: initiating a defrost mode for defrosting the ambient heat exchanger, wherein the defrost mode comprises: compressing a refrigerant to a high pressure via the compressor; transferring thermal energy from the refrigerant to the ambient heat exchanger; expanding the refrigerant to a low pressure via the expander; and the refrigerant absorbing thermal energy in the heating heat exchanger; monitoring a defrosting process of the ambient heat exchanger triggered by the defrost mode, the monitoring of the defrosting process comprises monitoring of the pressure difference between the high pressure and the low pressure and/or monitoring of the pressure gradient of the pressure difference between the high pressure and the low pressure and/or monitoring of the high pressure, and detecting an appearance of an indicator that indicates the end of defrosting of the defrosting process, the indicator being detected when the pressure difference exceeds a predefined threshold and/or the pressure gradient exceeds a predefined threshold and/or the high pressure exceeds a predefined threshold, wherein, the predefined threshold for the pressure difference is 120% of a pressure difference between the high pressure and the low pressure that is detected at the initiation of the defrost mode and/or the predefined threshold for the pressure gradient is 120% of a pressure gradient of the pressure difference between the high pressure and the low pressure that is detected at the initiation of the defrost mode and/or the predefined threshold for the high pressure is 120% of a high pressure that is detected at the initiation of the defrost mode.

2. The method according to claim 1, wherein the method comprises detecting the end of defrosting, and wherein the end of defrosting is detected as soon as at least one end-of-defrosting indicator is detected.

3. The method according to claim 1, wherein the method comprises detecting the end of defrosting, and wherein the end of defrosting is detected when a previously defined delay time has elapsed upon detecting the appearance of the indicator.

4. The method according to claim 1, wherein the method further comprises terminating the defrost mode as soon as the end of defrosting is detected or the duration of the defrost mode exceeds a predefined length.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 is a process flow chart of a process flow of a method according to the invention, with FIGS. 3-8 depicting the process flow chart of FIG. 1 taking into account alternative pressure aspects that are monitored during the monitoring step 106; and

(3) FIG. 2 is a schematic representation of a heat pump according to the invention.

DETAILED DESCRIPTION

(4) The method 100 according to the invention comprises initiating 101 a defrost mode of the ambient heat exchanger 14 of the heat pump 10.

(5) In defrost mode, the method includes compressing 102 a refrigerant to a high pressure by means of a compressor 11, transferring 103 thermal energy from the refrigerant to the ambient heat exchanger 14, thereby heating the ambient heat exchanger 14 and defrosting it accordingly. The method 100 further comprises expanding 104 the refrigerant to a low pressure by means of an expander 13, and receiving 105 thermal energy from a mass air flow of a vehicle interior onto the refrigerant by means of the heating heat exchanger.

(6) In defrost mode, the refrigerant circuit is reversed as compared to the heating mode. While in heating mode, the ambient heat exchanger serves as an evaporator; in defrost mode it serves as a condenser. The same applies to the heating heat exchanger, which acts as an evaporator in defrost mode and as a condenser in heating mode.

(7) Further, the method 100 according to the invention comprises monitoring 106 a defrosting process of the ambient heat exchanger 14 initiated by the defrost mode. A pressure difference between the high pressure and the low pressure is monitored 107 and/or a pressure gradient of the pressure difference between the high pressure and the low pressure is monitored 108 and/or the high pressure is monitored 109.

(8) Further, the method 100 may comprise detecting 110 an appearance of an end-of-defrosting indicator, and in particular when the pressure difference and/or the pressure gradient and/or the high pressure exceed a respective predefined threshold. Furthermore, the end of defrosting may be detected 111 as soon as at least one indicator for the end of defrosting has been detected, or after expiry of a previously defined delay upon detection of the appearance of an indicator.

(9) In addition, the method 100 preferably comprises terminating 112 the defrost mode once the end of defrosting has been determined 111 and/or the duration of the defrost mode exceeds a previously defined length.

(10) FIG. 2 shows a heat pump 10 of a motor vehicle according to the invention, comprising a compressor 11 for compressing a refrigerant to a high pressure, an ambient heat exchanger 14, an expander 13 for expanding the refrigerant to a low pressure, and a heating heat exchanger 12 for absorbing thermal energy. Further, the heat pump 10 comprises a monitoring unit 15, which may comprise at least one respective sensor to detect the high pressure and the low pressure and to monitor the high pressure and/or the pressure difference and/or the pressure gradient. Moreover, the monitoring unit may further be configured as a control unit to, for example, initiate and/or terminate the defrost mode and/or initiate and/or terminate the heating mode.

(11) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.