An automotive electric system including a loop-type voltage regulating device and a method of loop regulating a voltage of an automotive electric system

Abstract: The invention relates to a loop-type voltage regulating device (10), particularly for regulating a voltage of an automotive electric system, being of a type which includes at least one thermal engine (15), a voltage regulator (13) and an alternator (11) operative to deliver a system regulated-voltage signal (A+) to and receive a regulation signal (DF) from the voltage regulator (13). Advantageously, according to the invention, the voltage regulating device further includes a control unit (14) within the regulating loop, which unit is connected between the thermal engine (15) and the voltage regulator (13) and is adapted to supply the latter with a signal related to the engine operation.

Description: This invention relates to an automotive system including a voltage regulating device. Specifically, the invention relates to a loop-type voltage regulating device, particularly for regulating a voltage of an automotive electric system, including at least one thermal engine, a voltage regulator and an alternator operative to deliver a system regulated voltage signal to and receive a regulation signal from the voltage regulator. The invention also relates to a method of loop regulating a voltage. In particular, but not exclusively, the invention relates to a voltage regulating device for an automotive electric system, and the description which follows will cover this field of application for convenience of illustration. Prior Art Automotive electric systems are known to incorporate provisions for regulating the system voltage according to the thermal engine rotational speed. At low rpm (revolutions per minute), a thermal engine as used for automobile vehicles is bound to develop a low drive torque. In this condition, connecting in an electric load of substantial magnitude, such as an air-conditioning apparatus, may bring the engine to switch off because the alternator coupled thereto, in order to supply the amount of current required, would demand a higher torque than the engine can produce. Shown generally and schematically at 1 in Figure 1 is a conventional voltage regulating device for an automotive electric system according to the preamble of claim 1. The regulating device 1 includes essentially an alternator 2, a battery 3 and a voltage regulator 4, being connected in parallel together. The voltage regulator 4 includes: a first terminal TR'1, being connected to a first terminal TA'1 of the alternator 2 and receiving a phase signal PH; a second terminal TR'2 connected to a second terminal TA'2 of the alternator 2 and connected to a voltage reference, specifically a ground voltage GND; a third terminal TR'3, being connected to a third terminal TA'3 of the alternator 2 and receiving a regulated-voltage signal A + ; and a fourth terminal TR'4 being connected to a fourth terminal TA'4 of the alternator 2 and delivering a regulation signal DF. Based on the phase signal PH from the alternator 2, the voltage regulator 4 will essentially monitor the regulated-voltage signal A + and regulate it by means of the regulation signal (or field driver) DF. Thus, in the regulating device 1, the phase signal PH is utilised to provide an indication of the engine state of operation through the operation of the alternator 2. In fact, with the engine crankshaft being coupled to the alternator shaft by a pulley drive, the alternator rpm will be proportional to the engine rpm. This scheme should be found in many commercially available regulators, whereby the phase signal from the alternator is analysed and different strategies are used, according to the signal width and frequency, to control the system regulated-voltage signal. Figure 2 shows in greater detail a voltage regulator 4 of a type currently employed in automotive electric systems. The voltage regulator 4 comprises a threshold comparator 5 connected between first and second terminals, TR'1 and TR'2, of the voltage regulator 4, and is biased at its input by a voltage source VB. The threshold comparator 5 is connected with its output to a plurality of switches SW1,...SWN which are controlled by a plurality of buffers I1,...IN according to the frequency value fPH of the phase signal PH at the first terminal TR'1, as well as according to reference values f1,...fN set by said buffers I1,...IN. The controlled switches SW1,...SWN are connected directly to the fourth terminal TR'4 of the voltage regulator 4 as well as to the third terminal TR'3 through a plurality of ramp comparators CR1,...CRN. The voltage regulator 4 of Figure 2 operates as follows. According to the frequency fPH of the phase signal PH at the first terminal TR'1, the voltage regulator 4 will regulate the system voltage A + using different time constants which have been set by the buffers I1,...IN according to the operational state of the vehicle engine. In particular, the buffers I1,...IN will close one of the switches SW1,...SWN to connect, via a ramp comparator CR1,...CRN, the third terminal TR'3 of the voltage regulator 4, whereat the regulated-voltage signal A + is present, to the fourth terminal TR'4 of the voltage regulator, whereat the regulation signal DF is present. When no signal is received by the alternator 2, or if its frequency is less than a first reference value f1, no switches SW1,...SWN would be closed and the voltage regulator 4 would be switched off to a stand-by condition. In the presence of a heavy electric load while the engine is at low rpm, the voltage regulator 4 will control the torque to the alternator 2 to increase proportionally, so that a current can be generated to match the load. Thus, an E.C.U. (Engine Control Unit) 6 of an automotive thermal engine 7 is enabled to reply increasing the engine rpm, without switching off the thermal engine 7, as shown schematically in Figure 3. In particular, the voltage regulator 4 controls the alternator 2 by means of the regulation signal DF and according to the information received from the alternator 2 itself through the phase signal PH and the regulated-voltage signal A + . Similarly, the control unit 6 will receive from the engine 7, via a plurality of sensors, various information INF concerning the engine state, and will act on it by a plurality of signals AT, generally designated as actuators. While being in many ways advantageous, this prior scheme has a drawback in that the voltage regulator 4 obtains the information about the engine operation from the rotational speed of the alternator 2, thus losing concurrence of this information. In fact, by the time that the engine rpm is derived from the alternator rotation, the engine may have changed its state and the voltage regulation proves less than optimum for the system. Also known from the German Patent Application No. DE 196 45 944 A1 filed on November 7, 1996 in the name of Robert Bosch GmbH is a control unit for a power supply system on-board comprising of at least two batteries rechargeable by a generator, intended to supply electricity to various users. The control unit is located between the two batteries and comprises a power supply unit, a bus-interface microcomputer, a DC/DC converter and a short circuit proof output stage. Based on system information, the control unit switches on or off the linkage between both batteries and, after power down, shifts to "sleep-mode". Furthermore, a method of voltage regulation which is carried out with the assistance of a control unit including a timer is known from the European Patent Application No. EP 1 093 974 A2 filed on September 14, 2000 also in the name of Robert Bosch GmbH. As described in this document, the already set charging capacity for the battery is matchable according to the need dependent fluctuating power intakes of the electric user loads, and to engine speed dependent fluctuating power outputs of the generator, or the generator loading. In particular, the battery is used as a starting battery for the engine. The underlying technical problem of this invention is to provide a voltage regulating device, particularly for automotive electric systems, with such structural and functional features as to optimise the system voltage regulation, thereby overcoming the limitations of known devices. Summary of the Invention The resolutive idea proposed by the invention is based on using the system control unit to let a voltage regulator know the operational state of the engine in real time. This resolutive idea for the technical problem is achieved by a voltage regulating device as previously indicated and defined in Claim 1. The technical problem is further solved by a voltage regulating method as previously indicated and defined in Claim 9. The features and advantages of the voltage regulating device according to the invention will be apparent from the following description of an embodiment thereof, given by way of non-limitative example with reference to the accompanying drawings. Brief Description of the Drawings In the drawings: Figure 1 shows schematically a voltage regulating device of a known automotive electric system; Figure 2 shows schematically a detail of the device of Figure 1; Figure 3 shows schematically the principle of operation of the device shown in Figure 1; Figure 4 shows schematically a voltage regulating device for an automotive electric system according to the invention; Figure 5 shows schematically the principle of operation of the device shown in Figure 4. Detailed Description With reference to the drawings, and in particular to Figure 4 thereof, a voltage regulating device for an automotive electric system, according to this invention, is shown generally at 10 in schematic form. The voltage regulating device 10 includes essentially an alternator 11, a battery 12, and a voltage regulator 13. The voltage regulator 13 has a first terminal TR1 connected to a first terminal TC1 of a control unit 14 and arranged to receive a phase signal PH. The control unit 14 itself has a second terminal TC2 connected to a first terminal TA1 of the alternator 11 and arranged to receive a regulated-voltage signal A+, and has a third terminal TC3 connected to a second terminal TA2 of the alternator 11, as well as connected to a second terminal TR2 of the voltage regulator 13 and connected to a voltage reference, in particular a ground voltage reference GND. The voltage regulator 13 also has a third terminal TR3 connected to a third terminal TA3 of the alternator 11 and arranged to receive the regulated-voltage signal A + , and has a fourth terminal TR4 connected to a fourth terminal TA4 of the alternator 11 and arranged to deliver a regulation signal DF. In this way, the control unit 14 is used to keep the voltage regulator 13 informed about the operational state of the thermal engine 15, as shown schematically in Figure 5. In particular, the voltage regulating device 10 includes a regulating loop comprising in turn the thermal engine 15, the alternator 11, the voltage regulator 13, and the control unit 14, the latter controlling the voltage regulator 13 by means of the phase signal PH. The control unit 14 is in fact normally connected to a plurality of sensors (not shown) which provide it with different variables INF related to the operation of the engine 15. Among other parameters, the control unit 14 will know the drive torque value, engine rpm, engine temperature, and whether the driver of the vehicle is speeding up. In addition, the control unit 14 will monitor the load applied to the electric system. All this information is processed quite rapidly, thanks to the high calculating capacity of the control unit 14, to supply the engine with the proper amount of fuel/air, control the opening and closing times of valves, and provide other functions generally indicated in Figure 5 as actuators AT. In other words, the control unit 14, and the information processed and contained therein, provide a very accurate real-time assessment of the operational state of the engine, and allow subsequent changes of this state to be predicted. Advantageously in this invention, existing control units 14 in the electric systems of automobile vehicles are utilised to drive a voltage regulator 13 for optimum system voltage and, hence, extended life of the system battery 12 utilised in such system. Also, advantageously according to this invention, the engine minimum rpm can be kept down, and with it, the emission of polluting exhaust gases. It should be noted that the voltage regulating device 10 of this invention uses a conventional voltage regulator 13, the control unit 14 supplying, on its first terminal TC1, a phase signal PH in the form of a square-wave signal having similar characteristics as the phase signal from the alternator 11 and being processable by a conventional voltage regulator 13. The operation of the voltage regulating device 10 according to the invention will now be described. According to the frequency fPH of the phase signal PH from the control unit 14, the voltage regulator 13 operates to regulate the system voltage A + by the application of different time constants according to the operational state of the engine, as previously explained in connection with the state of the art. In particular, these time constants can be set by suitable buffers arranged to close corresponding switches within the voltage regulator 13. When no signal reaches the control unit 14, or its frequency is less than a minimum value f1, no switches are closed, and the voltage regulator 13 is switched off to a stand-by condition. Briefly, whereas conventional devices for regulating the voltage in an automotive electric system perform a loop type of regulation through the engine/alternator/regulator combination, utilising the phase signal from the alternator to control the system voltage regulator, the voltage regulating device of this invention also incorporates the system control unit with the regulation loop, and uses the phase signal from the control unit, specifically a square-wave signal which is compatible with the voltage regulators currently in use.

Claims: An automotive electric system including at least one thermal engine (15) and a loop-type voltage regulating device, the loop-type voltage regulating device comprising a voltage regulator (13) and an alternator (11) driven by the thermal engine (15), the alternator (11) being operative to deliver a system regulated-voltage signal (A + ) to and to receive a regulation signal (DF) from the voltage regulator (13), the voltage regulating device having a first terminal (TC1) for receiving a phase signal from the alternator (11), characterised in that the automotive electric system further includes a control unit (14) connected between the thermal engine (15) and the first terminal (TC1) of the voltage regulator (13), and in that the control unit (14) receives at least one engine operation signal (INF) and, in response thereto, supplies the voltage regulator (13) with a signal (PH) corresponding to the engine operation, the signal (PH) supplied to the first terminal (TC1) by the control unit (14) being a suitable square-wave phase signal to be processed by the voltage regulator (13). An automotive electric system according to Claim 1, characterised in that the control unit (14) has at least a second terminal (TC2) connected to the alternator (11) to receive the system regulated-voltage signal (A + ). An automotive electric system according to Claim 1, characterised in that the control unit (14) is connected to a plurality of sensors providing it with a set of variables related to the engine operation among drive torque value, engine rpm, engine temperature, and whether a driver of a vehicle comprising said voltage regulating device is speeding up. An automotive electric system according to Claim 3, characterised in that the calculating capacity of the control unit (14) is appropriate to: process the incoming variables at a fast rate; supply, as a phase signal (PH), an accurate assessment of the operational state of the engine in real time; and predict any later changes of said state. An automotive electric system according to Claim 1, characterised in that the control unit (14) delivers, on its first terminal (TC1), a phase signal (PH) in the form of a square-wave signal having similar characteristics as a phase signal from the alternator (11) and being processable by a conventional voltage regulator (13). An automotive electric system according to Claim 1, characterised in that the voltage regulator (13) comprises a plurality of buffers and switches effective to regulate the system voltage signal (A + ) by application of different time constants according to the operational state of the engine and the frequency (fPH) of the phase signal (PH) from the control unit (14). An automotive electric system according to Claim 6, characterised in that the voltage regulator (13) is switched off and held in a stand-by condition when no signal is delivered to the control unit (14). An automotive electric system according to Claim 6, characterised in that said voltage regulator (13) is switched off and held in a stand-by condition upon the control unit (14) being delivered a signal at a frequency below a minimum value (f1). A method of loop regulating a voltage of an automotive electric system including at least one thermal engine (15) and a loop-type voltage regulating device, the loop-type voltage regulating device comprising a voltage regulator (13) and an alternator (11) driven by the thermal engine (15), the alternator (11) being operative to deliver a system regulated-voltage signal (A + ) to and to receive a regulation signal (DF) from the voltage regulator (13), the voltage regulating device having a first terminal (TC1) for receiving a signal from the alternator (11), the method comprising at least the steps of: detecting variables related to the operation of the thermal engine (15) by having a control unit (14) connected between the thermal engine (15) and the first terminal (TC1) of the voltage regulator (13), the control unit (14) receiving at least one engine operation signal (INF) and, in response thereto, supplying the voltage regulator (13) with a signal (PH) corresponding to the engine operation; real-time processing the variables detected by the control unit (14) in order to assess the actual conditions of the thermal engine (15) operation; regulating the system regulated-voltage signal according to the thermal engine (15) conditions of operation detected, using the voltage regulator (13) which is supplied by the control unit (14) with a suitable square-wave phase signal (PH) corresponding to the engine operation to be processed by the voltage regulator (13).

Inventors: GALLINARI MAURIZIO, MAGGIONI GIAMPIETRO, MORELLI MARCO, SERRATONI CLAUDIO, GALLINARI, MAURIZIO, MAGGIONI, GIAMPIETRO, MORELLI, MARCO, SERRATONI, CLAUDIO
Applicants: ST MICROELECTRONICS SRL, STMICROELECTRONICS S.R.L.
Application year: 2000
Main classification: B60R16
IPC codes: H02J7, B60R16, H02P9