Controller for heating in reversible air conditioning and heat pump HVAC system for electric vehicles

• US 6,118,099 A
• Filed: 11/12/1998
• Issued: 09/12/2000
• Est. Priority Date: 11/12/1998
• Status: Expired due to Term

• Current Assignee: FCA US LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Corporation (Mercedes-Benz Group AG)
• Inventors: Ziehr, Lawrence, Tagliapietra, Lance C., Lake, Barry J.
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US09/190,547
• Time in Patent Office: 670 Days
• Field of Search: 219/202-208, 219/497, 219/494, 219/491, 219/506, 219/511, 62/239, 62/196 C, 62/198, 62/244, 62/323.1, 62/323.3, 62/228.4, 165/43, 165/29, 165/23, 165/51
• US Class Current: 219/202
• CPC Class Codes: B60H 1/00907 where the flow direction of the refrigerant changes and an evaporator becomes condenser
• CPC Class Codes: B60H 1/2218 controlling the operation of electric heaters
• CPC Class Codes: B60H 2001/00935 comprising four way valves for controlling the fluid direction

Abstract

A reversible HVAC system for heating a passenger compartment of a motor vehicle is disclosed. The HVAC system includes a heat pump and an electric heater for supplying heat directly to air blown into the passenger compartment. A controller initially selects the heat pump to provide the heat that is directed into the passenger compartment. The heat pump attempts for a predetermined period of time to heat the passenger compartment to a target temperature. The controller stores a heat pump gain value representing the heating capacity of the heat pump before switching the heating operation to the electric heater. During operation of the electric heater, the controller calculates a system heat gain value representing the required heating capacity to maintain the passenger compartment at the target temperature. While the electric heater is operating, the controller continuously modifies the heat pump gain value to reflect changes in the ambient temperature. When the heat pump gain value approximately equals or exceeds the system gain value the controller selects the heat pump to provide heating.

Claims

1. A heating control system for heating an interior compartment of a motor vehicle, the heating control system comprising:

an air-flow structure defining therein an air passageway to the interior compartment;

a blower for forcing air through the air passageway towards the interior compartment;

a reversible heat pump system having an electric compressor for compressing a refrigerant, an outside heat exchanger for transferring heat between an outside environment at an ambient temperature and the refrigerant, an inside heat exchanger for transferring heat between the refrigerant and the air flowing through the air-flow structure, a refrigerant flow switching device for switching the flow of refrigerant to provide a cooling mode and a heating mode, and a flow management center for providing pressure reduced refrigerant to the inside heat exchanger and the outside heat exchanger;

an electric heater arranged in the air-flow structure for generating electric heat for directly heating the air flow directed to the interior compartment;

a controller for determining a heat pump gain representing a heat pump heating capacity and for determining a system gain representing a required heating capacity for obtaining a desired interior compartment temperature, said controller modifying the heat pump gain based upon changes in the ambient temperature, and said controller selecting the reversible heat pump system for supplying heat to the interior compartment when the heat pump gain is substantially equal to or greater than the system gain.

2. The heating control system of claim 1 further comprising:

a temperature selector for inputting a target temperature value representative of the desired interior compartment temperature.

3. The heating control system of claim 1 wherein the electric heater is a PTC heater.

4. The heating control system of claim 3 wherein the electric heater further comprises a blend door for regulating the electric heat transferred to the air flow directed to the interior compartment.

5. The heating control system of claim 2 further comprising:

a temperature sensor for measuring a post inside heat exchanger temperature; and

wherein the controller adjusts the speed of the electric compressor to vary the heat transferred to the air flowing through the air-flow structure so that the post inside heat exchanger temperature is substantially equal to the target temperature.

6. A method of heating a passenger compartment of a motor vehicle having a reversible HVAC system, the HVAC system having a heat pump and an electric heater, the heat pump having an electric compressor for compressing a refrigerant, a refrigerant flow switching device coupled to the electric compressor for reversing the flow of the refrigerant, an inside and an outside heat exchanger in communication with the flow reversal device for transferring heat between the outside environment and the passenger compartment, and a pressure reducing assembly in communication with the inside and the outside heat exchangers for providing pressure reduced refrigerant to act as a heat transfer medium, said HVAC system having a heating mode and a cooling mode, the method comprising the steps of:

turning on the heat pump;

ascertaining a first value representative of a target temperature for the passenger compartment;

ascertaining a second value representative of a passenger compartment temperature;

controlling a rotating speed of the compressor based on a first error determined from the first value and the second value such that a quantity of heat energy is transferred into the passenger compartment, thereby causing an increase in the passenger compartment temperature to a first temperature above an ambient temperature;

storing a heat pump gain value representative of a first heating capacity associated with the increase in the passenger compartment temperature to the first temperature;

ascertaining whether the first error has failed to decrease to about zero within a predetermined period of time, such that if the first error has failed to decrease to about zero within a predetermined period of time, switching the heat pump off and turning on the

supplemental heater;

modifying the stored heat pump gain value based upon changes in the ambient temperature;

generating a quantity of heat from the supplemental heater such that the passenger compartment temperature is increased to a second temperature that is substantially equal to the target temperature;

calculating a system gain value representative of a second heating capacity associated with the increase in the passenger compartment temperature to the second temperature;

selecting the heat pump for supplying heat to the passenger compartment when the heat pump gain is substantially equal to or greater than the system gain and otherwise selecting the electric heater for supplying heat to the passenger compartment.

7. The method of claim 6 wherein the predetermined period of time is approximately 40 seconds.

8. The method of claim 6 further comprising the steps of:

determining that the system gain value exceeds a predetermined value that represents an overhead energy associated with operating the heat pump and electric heater simultaneously, and

operating both the heat pump and the electric heater.