Air conditioning system for automotive vehicles

Abstract: In an air conditioning system (10) for controlling the temperature of a vehicle passenger compartment, a valve (107) is disposed in a fluid passageway for controlling an amount of the engine coolant flowing toward the heat exchanger (103). A sensor device (16) senses an air temperature for the air flow through the heat exchanger and generates an electrical sensor signal indicative thereof. A temperature selector selects a target temperature of the air flow through the heat exchanger (103) and generates an electrical set signal indicative thereof. A control circuit (18) controls opening of the valve (107) by integrating a feed-back control and a feed-forward control based on the electrical sensor signal and the electrical set signal. Therefore, the air conditioning system (10) is adapted for improving control response characteristics without influences from disturbances and ensures improved control to provide stable control with rapid response to achieve a target temperature or a modification to the set temperature inside of the automobile compartment, or both.

Description: The present invention relates generally to air conditioning systems, and, more particularly, to an air distributing mechanism for air conditioning systems in automotive vehicles. Automotive air conditioning systems having a passenger compartment air temperature control device are known in the art. Generally, an automotive air conditioner is provided with a heat exchanger which is fluidly connected to and driven by an engine, that radiates heat introduced to the heat exchanger by a flow of engine coolant. The automotive air conditioner controls the heating of the passenger compartment. A coolant pump, which is also fluidly connected to the engine, circulates the coolant. The temperature of the passenger compartment is controlled by either a manual control mechanism or by an automatic control mechanism which employs an algorithm to achieve a predetermined temperature. For example, U.S. Patent No. 5,226,595 to Devera et al. (Unexamined Japanese Publication patent, No. H5-246230) are known. Fig. 1 discloses an overall configuration of an air conditioning system. An air conditioning system 100 includes duct unit 101 provided with a blower device 112; an inside air inlet opening 110, which communicates with the automobile compartment to exhaust recirculated air; and an outside air inlet opening 111, which communicates with an external space. These inlets are opened and closed by a damper 109. Air conditioning system 100 further includes evaporator 102, which is a part of a refrigerant circuit for cooling air passing therethrough; heater core 103 disposed downstream from evaporator 102; and a plurality of outlets ( e.g. , a defroster outlet 113 and a floor outlet 114), each of which opens into the automobile compartment. Heater core 103 is fluidly connected to engine 104 and receives engine coolant from engine 104 through a coolant pump 105, vehicle radiator 108, and control valve mechanism 107, each of which is serially connected to engine 104 by a fluid passageway 106. Coolant pump 105 is driven by engine 104 via an engine driven member, such as a belt. Further, an air temperature sensor 115 for detecting the temperature at the rear of heater core 103 is disposed downstream from heater core 103 and is electrically connected to an electric control unit 117 that controls the opening and closing of control valve 107. A temperature setting device 116 also is electrically connected to electrical control unit 117 to control a set temperature "TS." In the operation of air conditioning system 100, coolant that is heated by engine 104 is pumped into heater core 103 by coolant pump 105 with control valve 107 regulating the amount of the flow of coolant therethrough. The coolant is cooled in radiator 108, as required, and is circulated within fluid passageway 106. Air is drawn from inside and outside air inlet openings 110 and 111 by closing or opening damper 109, and flows into the automotive compartment from outlet openings 113 or 114 through evaporator 102 and through the coils of heater core 103. Typically, air circulation is forced by blower device 112. Further, set temperature "TS" is determined according to temperature setting device 116 in a manual air conditioner. In an automatic air conditioner, set temperature "TS" is determined in response to several factors, including temperature setting device 116, the temperature in the vehicle compartment, the air temperature outside, and the quantity of solar radiation entering the vehicle. The temperature of the air discharged to the vehicle compartment is controlled by regulating the opening of control valve 107. A sensor 115 issues a sensor signal by detecting air temperature "TO" at outlet of heater core 103. Temperature setting device 116 issues a setting signal by determining set temperature "TS." Sensor and setting signals are input continuously into electric control unit 117. Using these signals, electric control unit 117 computes a value for opening "FB" at control valve 107 that is necessary to achieve the desired vehicle compartment temperature "TS" using the automatic feed-back algorithm shown in Fig. 2 . The terms "q" and "r" in arithmetic feedback algorithm represent coefficients. Several factors may alter the operation of the air conditioning system. For example, a change in the rotation speed of engine 104 alters the amount of coolant that flows to the heat exchanger; a change in rotation speed of blower device 112 alters the air quantity generated by blower device 112; the mixture of interior air with exterior air exhausted from interior and exterior air outlet openings 110 or 111 alters air temperature at an inlet of evaporator 102; and, the activation or de-activation of a compressor (not shown) fluidly connected to evaporator 102; and the change in air temperature outside the vehicle alters air temperature at the inlet of evaporator 102. Therefore, in these conditions, the disturbances discussed above may cause a change in the outlet air temperature "TO" of heater core 103 blown from outlet openings 113 or 114 because outlet air temperature "TO" is controlled by only feedback control (PI control or PID control). Accordingly, this results in an uncomfortable environment for a vehicle passenger whenever outlet air temperature "TO" of heater core 103 increases. In addition, if coefficients "q" and "r" in the arithmetic feedback algorithm are regulated to prevent a change in outlet air temperature "TO," control valve 107 exhibits a "hunting" phenomena and becomes unstable. Fig. 3 illustrates the control characteristic curves of control valve 107. It shows that outlet air temperature "TO" of heater core 103 changes significantly in response to change 121 in inlet air temperature "TI," change 122 in rotation speed of engine 104, change 123 in voltage of blower 112, and change 124 in set temperature "TS." Further, the regulation of control valve 107 tends to be unstable, i.e. , to overshoot the desired valve position or to exhibit a "hunting" condition. For instance, when the passenger in the vehicle changes set temperature "TS," it takes a significant period of time for the outlet air temperature "TO" to rise to meet set temperature "TS." It takes additional time for the air temperature in the vehicle compartment to reach the set temperature "TS." These and other problems with the prior art are addressed by the invention described below. It is an object of the invention to provide an automobile air conditioner adapted for improving the response characteristics of control, and reducing or eliminating influence from outside disturbances. It is another object of the invention to provide an automobile air conditioner that achieves improved control by providing stable control with a rapid response to attain a target temperature or a modification to the temperature setting inside of an automobile compartment, or both. US-A-5127576 discloses a vehicle compartment temperature control system with feed-forward and feed-back temperature control according to the preamble of independant claim 1. According to the present invention, there is provided an air conditioning system for controlling the temperature of a vehicle passenger compartment comprising: a blower device directing an air flow toward the passenger compartment; a heat exchanger for exchanging heat with the air flow generated by the blower means; a pump driven by an engine for circulating an engine coolant therethrough; a fluid passageway for passing the engine coolant therethrough serially connecting the engine, the pump and the heat exchanger; a valve disposed in the fluid passageway for controlling the engine coolant flowing toward the heat exchanger; a sensor device disposed adjacent to the heat exchanger means for sensing an air temperature or the air flow through the heat exchanger and generating an electrical sensor signal indicative thereof; a temperature selector for selecting a target temperature of the air flow through the heat exchanger means and generating an electrical set signal indicative thereof; and a control circuit for controlling an opening of the valve by integrating a feed-back control and a feed-forward control based on the electrical sensor signal and the electrical set signal; wherein the feed-forward control includes the feed-forward algorithm which calculates a feed-forward signal based on a deviation between the electrical sensor signal and the electrical set signal; and characterised in that: the feed-forward algorithm includes the following equation: FF = ( a • N + b ) • X + c in which X = d • ( TS - TIN ) / ( TW - TIN ) and FF is the opening of the valve expected, N is the rotation speed of the engine, TS is a set air temperature, TIN is an air temperature at an inlet of the heat exchanger, TW is a fluid temperature of the engine coolant at the inlet of the heat exchanger, and "a", "b", "c", and "d" are coefficients. Further objects, features, and advantages of this invention will be understood from the following detailed description of the preferred embodiments of this invention with reference to the drawings. In the accompanying drawings:- Fig. 1 is a schematic view of a known automotive air conditioning system. Fig. 2 is a block diagram of a electrical control unit of the automotive air conditioning system of Fig.1. Fig. 3 is a graph illustrating the relationship of the valve opening, air temperature, blower voltage, and rotation speed of an engine, to time in the automotive air conditioning system of Fig. 1 . Fig. 4 is a schematic view of an automotive air conditioning system in accordance with an embodiment of the present invention. Fig. 5 is a block diagram of a electrical control unit of the automotive air conditioning system in accordance with the present invention. Fig. 6 is a graph illustrating the relationship between the valve opening, air temperature, blower voltage, and rotation speed of an engine, to time in the automotive air conditioning system of the present invention. Fig. 4 depicts an automotive air conditioning system in accordance with an embodiment ofthe present invention. In the drawings, like reference numerals are used to denote elements corresponding to those shown in Fig. 1. An air conditioning system 10 includes a first sensor 16 for detecting air temperature "TIN" at an inlet of heater core 103, which is disposed in duct 101 upstream from heater core 103. A second sensor 17 for detecting air temperature "TO" at an outlet of heater core 103 is disposed in duct 101 downstream from heater core 103. First and second sensors 16 and 17 provide electrical sensor signals according to an inlet air temperature "TIN" and an outlet air temperature "TO," respectively, to electrical control unit 18. Further, air conditioning system 10 includes a third sensor 19 for detecting the temperature "TW" of a fluid, such as a engine coolant ( e.g , an aqueous solution of ethylene glycol) at a fluid inlet of heater core 103, and is disposed in fluid passageway 106 between control valve 107 and the inlet of heater core 103. Third sensor 19 also generates an electrical sensor signal according to fluid temperature "TW" to electric control unit 18. Further, engine 104 and blower device 102 are electrically connected to electric control unit 18 and provide electrical signals according to the rotation speed "N" of engine 104 and the voltage "BLV" of blower device 112 to electrical control unit 18. Electric control unit 18 comprises a microprocessor which includes a arithmetic feed-forward algorithm 21 and a arithmetic feedback algorithm 22, as shown in Fig. 5. Arithmetic feedback algorithm 22 determines the opening "FB" of control valve 107 by performing an arithmetic operation on the electrical signals set temperature "TS" and air outlet temperature "TO" of heater core 103. Feed-forward algorithm 21 calculates a desirable opening of control valve 107. Arithmetic feed-forward algorithm 21 calculates opening "FF" of control valve 107 by performing an arithmetic operation on the electrical signals set temperature "TS," air inlet temperature "TIN" of heater core 103, fluid temperature "TW" of heater core 103, rotation speed "N" of a vehicle engine, and blower voltage "BLV." In arithmetic feed-forward algorithm 21, opening "FF" of valve control 107 is calculated based on the following equation: FF = (a • N+b)•x+c in which X = d • (TS - TIN)/(TW - TIN) K+e • BLV + f In the foregoing feed-forward algorithm, "a," "b," "c," "d," "e," and "f" are coefficients that are determined by the design specifications for the automotive air conditioner. The equation is an empirical formula introduced by the experience of the inventor. Table 1 shows illustrates relationships between the coefficients and the design specifications. Coefficients Design specification a, b, c (1) capacity of a pump (2) driving ratio between an engine and a pump (3) heat exchange efficiency of a heater core (4) capacity of a control valve d, e, f (1) rating of a blower (2) heat exchange efficiency of a heater core As is apparent from the equation above, arithmetic feed-back control, algorithm is the arithmetic PI or PID control algorithm, each of which is controlled by combining Proportion Calculus Action and Integration Calculus Action or by combining Proportion Calculus Action, Integration Calculus Action, and Differential Caloulus Action. Thus, set temperature "TS" is set according to temperature setting device 116, such as a potentiometer, in manual air conditioners. On the other hand, set temperature "TS" is set according to set value of temperature setting device 116, such as an electrical circuit, and is calculated based on information such as the air temperature in the vehicle compartment, the air temperature at outside of the vehicle, the quantity of solar radiation entering the vehicle through the windows, and the like, in the automatic air conditioner. Accordingly, the desired opening "FV" of valve control 107 incorporated by feed forward control is represented by the followings equation. FV = FB + FF Therefore, control valve 107 is operated according to opening "FV" which is the sum of "FF"and "FB." In the operation of air conditioning system 10, coolant that is heated by engine 104 is pumped into heater core 103 by coolant pump 105 with control valve 107 regulating the amount of the flow of coolant therethrough by using feed forward control "FV." The coolant is cooled in radiator 108 as required and is circulated within fluid passageway 106. Air is drawn from inside or outside air inlet openings 110 and 111, respectively, by opening or closing damper 109, and flows into the automotive compartment from outlet openings 113 or 114 through evaporator 102 and heater core 103. Normally, air circulation is forced by blower device 112. Fig. 6 illustrates control characteristic curves of an air conditioning system according to an embodiment of this invention obtained when (31) inlet air temperature "TIN" of heater core 103 is forcibly changed by shifting damper 110, (32) rotation speed "N" of engine 104 is changed, (33) voltage "BLV" of blower 112 is changed and (34) set temperature "TS" is changed. Outlet air temperature "TO" of heater core 103 does not change significantly and exhibits a stable condition despite these disturbances. Even if set temperature "TS" is changed, outlet air temperature "TO" of heater core 103 quickly achieves set temperature "TS." Therefore, the air conditioner that has electrical control unit 18 has a superior responsiveness to changes in set temperature "TS." Further, outlet air temperature "TO" of heater core 103 exhibits a significant upturn, i.e. , an overshooting locus, as shown in Fig. 6 . This control character is designed to inherently improve the quickness in raising the air temperature in the vehicle compartment. Air temperature in the vehicle compartment does not rapidly reach set temperature "TS" even if heater core outlet temperature rises rapidly. Therefore, the air conditioner allows heater core outlet air temperature "TO" to rise, initially overshooting the value of "TS" to ensure that the air temperature in the vehicle compartment reaches set temperature "TS" rapidly. Therefore, the automobile air conditioning system is adapted to improve a control response characteristic against influence from various disturbances. Further, the automobile air conditioning system may ensure improve control to provide stable control with a rapid response to reach a target temperature or to a modification of the set temperature inside of an automobile compartment, or both.

Claims: An air conditioning system (10) for controlling the temperature of a vehicle passenger compartment comprising: a blower device (112) directing an air flow toward the passenger compartment; a heat exchanger (103) for exchanging heat with the air flow generated by the blower means; a pump driven by an engine for circulating an engine coolant therethrough; a fluid passageway (106) for passing the engine coolant therethrough serially connecting the engine, the pump and the heat exchanger; a valve (107) disposed in the fluid passageway for controlling the engine coolant flowing toward the heat exchanger; a sensor device (16) disposed adjacent to the heat exchanger means for sensing an air temperature or the air flow through the heat exchanger and generating an electrical sensor signal indicative thereof; a temperature selector for selecting a target temperature of the air flow through the heat exchanger means and generating an electrical set signal indicative thereof; and a control circuit (18) for controlling an opening of the valve by integrating a feed-back control and a feed-forward control based on the electrical sensor signal and the electrical set signal; wherein the feed-forward control includes the feed-forward algorithm (21) which calculates a feed-forward signal based on a deviation between the electrical sensor signal and the electrical set signal; and characterised in that : the feed-forward algorithm (21) includes the following equation: FF = ( a • N + b ) • X + c in which X = d • ( TS - TIN ) / ( TW - TIN ) and FF is the opening of the valve expected, N is the rotation speed of the engine, TS is a set air temperature, TIN is an air temperature at an inlet of the heat exchanger, TW is a fluid temperature of the engine coolant at the inlet of the heat exchanger, and "a", "b", "c", and "d" are coefficients. The air conditioning system (10) of claim 1, wherein the feed-back control includes a feed-back algorithm (22) which calculates a feed-back signal based on a deviation between the electrical sensor signal and the electrical set signal. The air conditioning system (10) of claim 1, wherein the sensor device (16) includes a sensor disposed in the heat exchanger (103) for sensing a fluid temperature of the engine coolant passed through the heat exchanger and providing an electrical sensor signal indicative thereof, and the feed-forward algorithm (21) further calculates a second feed-forward signal based on the electrical fluid sensor signal. The air conditioning system (10) of claim 3, wherein the feed-forward algorithm (21) further calculates a third feed-forward signal based on an electrical signal generated by the rotation speed of the engine. The air conditioning system (10) of claim 4, wherein the feed-forward algorithm further calculates a fourth feed-forward signal based on an electrical signal issued by the voltage of the blower. The air conditioning system (10) of claim 1, wherein the sensor device (16) further includes a sensor disposed in an inlet of the heat exchanger (103) for sensing an air temperature of the air flow at the inlet of the heat exchanger and generating an electrical inlet air signal indicative thereof. The air conditioning system (10) of claim 1, wherein X = d • ( TS - TIN ) / ( TW - TIN ) + e • BLY + f , in which BLV is a voltage of the blower (112), and "e" and "f" are coefficients. The air conditioning system (10) of claim 1, wherein the feed-back control is a PI control. The air conditioning system (10) of claim 1, wherein the feed-back control is a PDI control. The air conditioning system (10) of claim 1, wherein the temperature selector includes a temperature selector operated by a passenger. The air conditioning system (10) of claim 1, wherein the temperature selector includes a first sensor device for sensing air temperature in the vehicle compartment, a second sensor device for sensing air temperature outside of the vehicle, and a solar sensor device for sensing quantity of solar radiation. The air conditioning system (10) of claim 12, wherein the temperature selector is operated by calculating the target temperature based on an electrical signal generated by at least one of the first, second, and third sensor devices.

Inventors: INOUE ATSUO, INOUE, ATSUO, INOUE, ATSUO, C/O SANDEN CORPORATION
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1997
Main classification: B60H1
IPC codes: B60H1