ARRANGEMENT FOR ENERGY TRANSMISSION IN A VEHICLE DRIVE UNIT

Abstract: Arrangement in a vehicle driven by an internal combustion engine (1), the exhaust from which is directed through a power generating turbine (8). Mechanical work obtained from the turbine (8) is returned to the engine (1) drive shaft via an electrical transmission system (11). The mechanical work of the turbine (8) is converted therein into electrical energy which is transmitted to an electrical machine unit (15) coupled to the engine drive shaft. A control unit (12) is arranged to regulate the transmission by the transmission system (11) of electrical energy so that when the engine (1) is subjected to load, the electrical machine unit (15) will operate as a motor, and when the vehicle is braked, the machine unit (15) will operate as a generator. In addition to enabling exhaust energy converted in the power turbine (8) into mechanical work to be transmitted to the engine drive shaft as useful work, the invention also provides an extra vehicle brake, a so-called retarder.

Description: Arrangement for energy transmission in a vehicle drive unit The present invention relates to an arrangement in a vehicle driven by an internal combustion engine, the exhaust from which is directed through a power generating turbine, which is arranged to drive an electric generator coupled to the turbine shaft. In vehicles equipped with a power generating turbine built into the engine exhaust system, it is previously known to transmit the driving force from the turbine to the engine output shaft via a mechanical gear system. Due to the large gear ratios, such trans¬ missions give rise to oscillations which are difficult to deal with and cause significant wear on the compo¬ nent parts of the mechanical gearing, as well as noise. The present invention relates to an arrangement for electrical power transmission from the power turbine to the engine output shaft, which arrangement eliminates said disadvantages and can also be used as an extra braking device for the vehicle, a so-called retarder. The invention is characterized in that the generator coupled to the turbine shaft is a component in an electrical transmission system coupled to a rotary electrical machine unit having a rotor included in a flywheel mounted on the output shaft of the internal combustion engine, and that a control unit is disposed to control the transmission by the trans¬ mission system of electrical energy between the generator and the machine unit, so that the machine unit operates as a motor when the engine is subjected to load and as a generator when the vehicle is braked. The electrical energy transmission from the turbine to the engine output shaft provides increased freedom in placement and use of the components in the engine compartment. An electronic control unit provides good capability to control the work transmitted, in response to the operating conditions of the vehicle and the engine. With the arrangement according to the invention it is possible to select the gear ratio so that the power turbine and the diesel engine achieve optimal cooperation both dynamically and thermodynamic- ally. Use according to the invention of an electric motor built into the engine flywheel also makes possible great savings in space. According to an advantageous embodiment of the invention, the transmission system comprises means for storing electrical energy. This makes it possible to store energy given off by the turbine generator when the engine is idling or decelerates and it makes possible as well the storage of energy when the machine built into the flywheel operates as a generator when the vehicle is being braked. The energy stored can then be returned to the output shaft of the engine as useful energy when the engine is subjected to load. Other features characterizing the invention are revealed in the accompanying clains and the description below of an embodiment exemplifying the invention, wherein reference is made to the accompanying figure which shows in schematic form an arrangement according to the invention applied to the drive unit of a large highway vehicle. The drive unit in the example consists of a supercharged diesel engine 1, to the output shaft of which there is coupled a usual mechanical transmission 2 comprising a clutch and a gearbox. The output shaft 3 of the transmission unit is coupled in a known manner to transmit torque to the vehicle drive wheels 4. The diesel engine 1 is supercharged by means of a known turbo unit 5. In such a unit, a turbine driven by the engine exhaust drives in turn a compressor located at the engine intake. A significant portion of the energy remaining thereafter in the exhaust is used to drive an additional turbine 8, usually called the power turbine. Its rotational speed is regulated by means of a so-called waste gate valve 9, which can shunt part of the exhaust past the turbine. Mechanical work can be transmitted, according to the invention, from the turbine shaft 10 to an electrical transmission system 11, in which the mechanical work is transformed into electrical energy, which is fed under the direc¬ tion of a control unit 12 to an electrical asynchronous machine 15 built into the engine 1 flywheel. The transmission system 11 comprises an AC- generator 16 driven without intermediate gearing by the power turbine 8. This generator is suitably a two- pole polyphase synchronous machine with a DC-magnetized rotor. At a turbine speed of about 60,000 rpm such a generator 16 will provide through each phase line alternating current of a frequency of about 1,000 Hz. The alternating current is then rectified in a recti¬ fier circuit 17 and the direct current emitted there¬ from is stabilized in a regulator 18 and is thereafter fed into an energy-storing circuit 20. Both the recti¬ fier circuit 17 and the regulator 18 have in principle the same construction as those used currently for converting AC to DC. The energy-storing circuit 20 comprises means, i.e. batteries of accumulator or capacitor type capable of storing energy at relatively high voltage levels of up to 500 V. At power levels of between 25 and 50 kW, which are transmitted between the turbine 8 and the asynchronous machine 15, currents of between 50 and 100 A are obtained, which means that there is a broad selection of commercially available electrical compo¬ nents which can be used in the transmission system 11. Direct current is delivered from the circuit 20 to an inverter circuit 21, wherein the direct current is converted into alternating current, which is supplied via a switching circuit 22 and a number of wires 23 to the asynchronous motor 15. The number of phases in the alternating current is adapted to the number of phases in the asynchronous motor 15 and the frequency and voltage is controlled by signals from the control unit 12. The inverter circuit 21 can comprise a usual bridge configuration with rectifiers, e.g. thyristors, controlled by signals from the control unit 12. In an alternative embodiment the rectifiers in the inverter circuit 21 can function bilaterally, i.e. conduct current in both directions in response to signals from the control unit 12. The inverter circuit 21 can thus also serve as a rectifier circuit for the alternating current delivered by the asynchronous machine 15, when it is operating as a generator. A stabilized direct current obtained is thus fed back into the energy-storing circuit 20. If this circuit 20 is fully charged, the switching circuit 22 will see to it that the energy generated by the asynchronous machine 15. ill be supplied to a resistive load 24 for convertion into heat. The switching circuit 22 also comprises rectifiers controlled by signals from the control unit 12. The asynchronous machine 15 can have any number of phases, preferably about nine. Suitably it has a short-circuited rotor winding and thus has no slip rings or brushes, which are subject to wear, energy losses etc. The machine is built into the fly¬ wheel of the engine 1 so that the rotor serves as a flywheel, while the stator of the machine 15 is a portion of the flywheel casing fixed to the engine 1. The operation of the electrical transmission system 11 is controlled by the control unit 12, which comprises one or more micro-processors. The control unit 12 controls the transmission -system 11 with signals through a plurality of wires 25-28. The control- unit 12 also controls a drive step 29 for controlling the waste gate valve 9 via a wire 31. The output signals are dependent on input signals fed to the control unit 12, from the transmission system 11 through a number of wires 33-35, from the drive unit through wires- 36,37 and from a number of means 41-43 manually actuatable from the driver's seat through wires 38-40. More specifically, the control unit 12 receives input signals through wires 33 from the rectifier unit 17 concerning the voltage and frequency produced by the generator, through wires 3 from the circuit 20 regarding the charge condition of the circuit 20 and through wires 35 from the inverter circuit 21 regarding the frequency and voltage of the alternating current fed to or from the asynchronous machine 15. Input signals are also fed to the control unit 12 via wire 3 from a sensor 44 which senses the rotational speed of the engine crankshaft, via wire 37 from a sensor 45 which senses the vehicle speed from the gearbox output shaft 3, via wire 40 from a position indicator which senses the engine load at the driver's accelerator pedal 41 or alternatively at the engine control rod, and via wire 39 from a sensor which senses the position of the brake pedal 42. Input signals to the control unit 12 are also fed from a start button 43 in the driver's cab via wire 38. The control unit 12 ' starts the diesel engine in response to such a signal. In response to said input signals, the control unit 12 sends output signals via wires 25-28 and 31. Wire 31 sends control signals to the drive step 29 for the waste gate valve 9 of the power turbine. The drive step 29 regulates electromagnetically the supply of pressure to a pressure means (not shown) regulating the waste gate valve 9, so that the turbine 8, and with it the generator 16, will not exceed a pre¬ determined maximum rpm. The wires 25 feed the magne¬ tization current to the rotor of the generator 16, whereby the voltage of the alternating current produced can be regulated in response to the charge state of the energy-storing circuit 20. At full charge the magnetization current is brought down to zero, and ' the generator 16 ceases to generate current. Control signals are sent via wires 26 to the voltage and charging regulator 18 for the purpose of regulating the current/voltage fed to the energy-storing circuit 20 in response to the charge condition of said circuit 20. Signals are sent from the control unit 12 to the inverter circuit 21 via wire 27. In response to the load and rpm of the engine 1, the voltage and frequency of the alternating current fed to the asynchronous machine 15 are regulated for varied torque from the same. Signals are fed to the switching circuit 22 via wire 28 to take up if necessary excess energy from the asynchronous machine 15 and direct it to the resistive load 24. The inverter 21 also receives signals from the control unit 12 causing the inverter 21 to deliver starting current to the asynchronous machine 15 to start the diesel engine 1. The control unit 12 controls the transmission of electrical energy to the asynchronous machine 15 so that when the diesel engine 1 is loaded, i.e. when the accelerator pedal 41 is actuated, the asynchronous machine 15 will operate as a motor, and when the brake pedal 42 is actuated and at a certain minimum vehicle speed, it will function as a retarder. If the diesel engine 1 idles or decelerates by quickly letting up on the accelerator pedal 41, only charging of the energy-storing circuit 20 will take place. Within the scope of the accompanying claims, the invention can, however, be modified in several alternative embodiments.

Claims: CLAIMS 1. Arrangement in a vehicle driven by an r- internal combustion engine (1), the exhaust from said engine (1) being directed through a power generating turbine (8), which is arranged to drive an electric 5 generator (16) coupled to the turbine shaft (10), characterized in that the generator (16) is a compo¬ nent in an electrical transmission system (11) coupled to a rotary electrical machine unit (15) having a rotor included in a flywheel which is mounted on the 10 output shaft of the engine, and that a control unit (12) is disposed to control the transmission by the transmission system (11) of electrical energy between the generator (16) and the machine unit (15), so that the machine unit (15) is made to operate as a motor 15 when the engine (1) is subjected to load and as a generator when the vehicle is braked. 2. Arrangement according to Claim 1, characterized in that the transmission system (11) comprises means (20) for storing electrical energy 20 delivered by the generator (16) or by the machine unit (15) when operating as a generator. 3. Arrangement according to Claim 2, characterized in that the machine unit (15) is a brushless asynchronous machine and that the energy 25 delivered therefrom when operating as a generator is stored, after rectification, in said means (20). 4. Arrangement according to Claim 3, characterized in that the energy delivered from the asynchronous machine (15) in response to the signals 30 emitted by the control unit (12) can be conducted to a resistive load (24). 5. Arrangement according to Claim 4, characterized in that self-generated heat in the asynchronous machine (15) is removed by forced 35 cooling, for example water cooling. 6. Arrangement according to Claim 2, characterized in that the generator (16) is a DC magnetized synchronous generator, and that the control unit (12) regulates the magnetization current in response to the charge level of the energy storing means (20). 7. Arrangement according to Claim 1, characterized in that a waste gate valve (9) directs the flow of exhaust through the turbine (8) in response to signals from the control unit (12). 8. Arrangement according to Claim 3, characterized in that the transmission system (11) includes a reversible inverter (21) which regulates the supply of current to and from the asynchronous machine (15) in response to signals emitted by the control unit (12). 9. Arrangement according to Claim 4, characterized in that the- transmission system (11) includes a switching circuit (22) which directs, in response to output signals from the control unit (12), the energy given off by the asynchronous machine (15) either to the energy storing means (20) or to the resistive load (24).

Inventors: JOHANSSON SVEN HANS, SJOESTROEM SVERKER, JOHANSSON, SVEN, HANS, SJOESTROEM, SVERKER
Applicants: SAAB SCANIA AB, SAAB-SCANIA AKTIEBOLAG
Application year: 1985
Main classification: B60L11
IPC codes: B60K6, B60L11, B60W10, B60W20, B60W30, F02G5