ELECTRIC POWER GENERATING APPARATUS

Abstract: An (exhaust gas turbine powered) electric power generating apparatus for supplying electrical loads (78) on a motor vehicle. The inlet (56) of the gas turbine (40) is supplied with the exhaust gas of an internal combustion engine. The effective turbine inlet area (56A) is controlled by inlet control valve (54) which is adjusted as a function of the output current of the electric generator (66). As generator output current increases the inlet control valve (54) is adjusted to decrease turbine inlet area thereby increasing engine back pressure which tends to slow the internal combustion engine down. An idle speed control unit (106) is provided which in response to engine slow-down increases the amount of air and fuel supplied to the internal combustion engine to thereby increase the exhaust gas mass flow supplied to the gas turbine.

Description: This invention relates to apparatus for generating electric power for the electrical loads on a motor vehicle and more particularly to apparatus wherein the exhaust gas of an internal combustion engine is supplied to a gas turbine which drives an electric generator that supplies electrical power to the electrical loads on the motor vehicle. Apparatus that drive an electric generator from a gas turbine that is supplied with the exhaust gas of an internal combustion engine are known, examples being the arrangements disclosed in US patent nos. 4,694,653 and 4,694,654. When driving an electric generator from a gas turbine, where the gas turbine is fed by the exhaust gas of an internal combustion engine, it is possible that at engine idle speed there will not be enough gas generated in terms of engine exhaust mass flow to drive the gas turbine at a speed that is sufficient to cause enough electric power to be generated by the electric generator to accommodate the electric loads on the motor vehicle. This is particularly true where there is a high electrical load on the electric generator. It accordingly is an object of this invention to provide an electric power generating apparatus for a motor vehicle wherein a gas turbine that drives an electric generator is supplied with the exhaust gas of an internal combustion engine and wherein the apparatus is so controlled that the gas turbine is supplied with sufficient exhaust gas mass flow at engine idle to cause the electric generator to be driven at a speed that is high enough to satisfy the electrical loads on the motor vehicle. To this end, an electric power generating apparatus in accordance with the present invention is characterised by the features specified in the characterising portion of Claim 1. In a preferred arrangement for accomplishing this object the gas turbine is provided with a controllable inlet control valve that can control the exhaust gas input to the gas turbine. As this inlet control valve moves toward a closed position, engine back pressure increases thereby tending to reduce engine speed. The internal combustion engine has an idle speed control unit and as engine speed decreases below a set idle speed the throttle valve on the intake side of the internal combustion engine is moved to a more open position with the result that more air and fuel is supplied to the intake side of the internal combustion engine. The net result of this is that exhaust gas mass flow of the internal combustion engine is increased which tends to increase gas turbine speed or at least maintain gas turbine speed at some value that is high enough to cause sufficient power to be generated by the electric generator that is driven by the gas turbine. Further, the apparatus of this invention includes means for sensing the output current of the electric generator and for adjusting the inlet control valve of the gas turbine as a function of the output current of the electric generator. The present invention is now described, by way of example, with reference to the accompanying single figure drawing which illustrates an (exhaust gas turbine) electric power generating apparatus made in accordance with this invention. Referring now to the drawing, the reference numeral 10 designates one cylinder of an internal combustion engine. A piston 12 reciprocates in the cylinder 10 and which is connected to crankshaft 14. The cylinder 10 has an intake valve 16 and exhaust valve 18 and is fitted with a spark plug 20 that is connected to a suitable ignition system (not illustrated). The exhaust valve 18 is connected to exhaust passage 24 provided by a pipe 26 so that the exhaust gas of the internal combustion engine is supplied to exhaust passage 24. The intake valve 16 communicates with an intake passage 28 provided by pipe 30. A pivotable throttle plate or throttle valve 32 is positioned within the intake passage 28 and is connected to pivotable actuating lever 34. The intake passage 28 can be supplied with fuel by a fuel injector 36 controlled by fuel control device 38. The inlet end 28A of the inlet passage 28 is the air inlet of the internal combustion engine and can be connected to an air cleaner or filter. The inlet end 28A is at atmospheric pressure. The drawing illustrates only one cylinder 10 of an internal combustion engine. It is to be understood that the internal combustion engine has more than one cylinder and all of the exhaust valves, like exhaust valve 18, of all cylinders are connected to exhaust passage 24 via, for example an exhaust manifold. The same is true of intake passage 28, that is, it is connected to all of the intake valves 16 of all of the cylinders of the internal combustion engine. The exhaust gas in exhaust passage 24, which is developed by the internal combustion engine, is supplied to the inlet of a gas turbine 40 that has a rotor 42. This gas turbine 40 is of the known radial inlet axial exhaust type and the axial exhaust of the gas turbine is via exhaust passage 44 provided by pipe 46. The gas turbine 40 can be bypassed by conduit or exhaust passage 50 which has an inlet connected to exhaust passage 24. Located in the exhaust passage 50 is a waste gate throttle valve 52. The gas turbine 40 has an inlet control valve 54 which cooperates with inlet passage 56 and with internal walls of the gas turbine. The inlet control valve 54 is vane-shaped and is connected to a pivotally mounted pin or rod 58. Inlet control valve 54 is connected to an actuator lever 60 by pivotally mounted pin 58 so that inlet control valve 54 is moved by actuator lever 60. As inlet control valve 54 is moved counterclockwise it tends to reduce the effective turbine inlet area 56A and as it moves clockwise it tends to increase the effective turbine inlet area. As will be more fully described hereinafter the position of inlet control valve 54 will control engine back pressure in exhaust passage 24; that is, back pressure increases as inlet control valve 54 moves toward a closed position (area 56A reduced) and back pressure decreases as inlet control valve 54 moves toward a fully open position (area 56A increased). Exhaust gas flow is therefore variably throttled, dependent upon the position of inlet control valve 54. The inlet control valve 54 can be of the type disclosed in US patent no. 4,633,670 or could be of the type disclosed in US patent nos. 4,214,850 and 3,313,518. The inlet control valve 54 is spring biased to a fully open position by a spring 62 connected to actuator lever 60. This spring 62 urges actuator lever 60 clockwise to a position where it engages a fixed stop 63. When actuator lever 60 engages stop 63, inlet control valve 54 is in a fully open position. As will be more fully described hereinafter, the inlet control valve 54 is adjusted in accordance with the load that is applied to gas turbine 40 by an electrical generator. The rotor 42 of gas turbine 40 is connected to the rotor 64 of an alternating current (ac) generator (electric generator) 66 by a shaft 68 illustrated by a dotted line. The ac generator 66 has a (three-phase, Y-connected) stator winding 70. The ac generator 66 is a permanent magnet alternating current generator and accordingly the rotor 64 is provided with permanent magnets (not illustrated) in a known manner. The rotor 64 is driven by the rotor 42 through shaft 68 so that the rotor 64 rotates at the same speed as the rotor 42. The stator or output winding 70 is connected to a (three-phase, full-wave) bridge rectifier 72 that is of the type disclosed in US patent no. 3,427,529 which is incorporated herein by reference. As shown in that patent, the bridge rectifier 72 has three diodes and three controlled rectifiers and the controlled rectifiers are controlled so as to maintain a desired regulated output voltage from bridge rectifier 72. The positive direct voltage output terminal of bridge rectifier 72 is connected to power supply conductor 74 and its negative direct voltage output terminal is connected to ground. The power supply conductor 74 is connected to the positive terminal of a storage battery 76 the negative terminal of which is connected to ground. The electrical loads on the motor vehicle are supplied by power supply conductor 74 and one of these loads is designated by reference numeral 78. This load 78 is energized when switch 80 is closed. A conductor 82 is a sense lead which senses the voltage on power supply conductor 74 and controls the conduction of the controlled rectifiers of bridge rectifier 72 to maintain the voltage on power supply conductor 74 constant in a manner that is described in the above-referenced US patent no. 3,427,529. By way of example, if the electrical circuit is a 12 volt circuit the voltage on power supply conductor 74 may be maintained at a regulated voltage of about 14 volts. The amount of current that is supplied to storage battery 76 and to the other electrical loads on the motor vehicle is sensed by a current transformer that is comprised of a winding 84 that is wound about power supply conductor 74. The winding 84 is connected to a load signal circuit 86, and together they define current sensing means. This circuit develops an output voltage on line 88 which is a function of the amount or magnitude of current being supplied to the electrical loads 78 on the motor vehicle. The line 88 is connected to one input of an AND gate 90. The idle speed of the internal combustion engine is controlled by an idle speed control system that is of the type disclosed in US patent no. 4,237,833 which is incorporated herein by reference. This idle speed control comprises an electric motor 92 that drives a throttle stop 94 that engages pivotable actuating lever 34. Pivotable actuating lever 34 can be moved by accelerator pedal 96 against the force of spring 97 which tends to move throttle valve 32 toward a closed position. The spring 97 also urges pivotable actuating lever 34 against throttle stop 94. The throttle stop 94 is projected or retracted by the electric motor 92. The electric motor 92 that drives throttle stop 94 is powered from an idle speed control unit 106 which is connected to electric motor 92 by line 108. The idle speed control unit 106 receives engine speed information from line 110 and may have other inputs as described in the above-referenced US patent no. 4,237,833. The engine speed information is provided by a magnetic pickup 112 that cooperates with a toothed wheel 114 that is driven by the crankshaft 14. The output of magnetic pickup 112 is applied to an engine speed signal shaping circuit 116, the output of which is applied to line 110. The signal on line 110 varies as a function of engine speed. The waste gate throttle valve 52 is controlled by an actuator 120 which receives the engine speed signal from line 122. The arrangement is such that waste gas throttle valve 52 is opened when engine speed exceeds a predetermined high speed value. The engine speed signal is applied to a low speed enable circuit 124 via lines 122 and 126. The output of low speed enable circuit 124 is an input to AND gate 90 via line 128. The low speed enable circuit 124 applies a signal to AND gate 90 when engine speed drops below some predetermined low engine speed. At engine speeds above the predetermined low speed no signal is developed on line 128. The inlet control valve 54 is adjusted by an electric motor 130. The electric motor 130 is connected to actuator lever 60 by a suitable mechanical drive which has been indicated by the dotted line 132. The actuator lever 60 is also mechanically coupled (dotted line 134) to a shiftable wiper 136 of a variable resistor 138. The voltage developed at the shiftable wiper 136 varies with variation in the position of inlet control valve 54 and this voltage is applied to a voltage comparator 140 via line 142. The output of AND gate 90 is applied as another input to voltage comparator 140 via line 144. The voltage comparator 140 compares the voltages on lines 142 and 144 and applies an error signal to a motor control circuit 146 via line 147. Motor control circuit 146 is connected to electric motor 130 via line 150. The signal on line 144 is also applied to motor control circuit 146 by line 151. With no signal on line 151 the motor control circuit 146 operates to maintain electric motor 130 deenergized and spring 62 can then move inlet control valve 54 to a fully open position against stop 63. It should be evident that the voltage at shiftable wiper 136 represents the actual position of inlet control valve 54. When AND gate 90 has an output the voltage on line 144 represents the desired position of inlet control valve 54 and this voltage is a function of the output current of ac generator 66 that is sensed by winding 84. This voltage also represents the extent to which the ac generator 66 and gas turbine 40 are being loaded or in other words the amount of torque required to drive the ac generator. Line 88, AND gate 90, and elements 120-151 define control means. The operation of the arrangement shown in Figure 1 will now be described. In describing the operation of Figure 1, some general principals of operation will be discussed first. As previously mentioned, the inlet control valve 54 can be adjusted to increase or decrease the effective turbine inlet area 56A. As the inlet control valve 54 is moved to decrease turbine inlet area 56A the back pressure in exhaust passage 24 will increase. As the back pressure in exhaust passage 24 increases the speed of the internal combustion engine tends to decrease. Assuming that the internal combustion engine is being controlled by the idle speed control unit 106, a reduction in speed of the internal combustion engine below the idle speed setting will cause the throttle valve 32 to move toward an open position thereby increasing the amount of air and fuel supplied to the internal combustion engine. This increase in both air and fuel causes the magnitude of the exhaust gas mass flow to increase which in turn causes the speed of the rotor 42 of the gas turbine 40 to increase or at least maintain some speed. In summary, the increase in back pressure within exhaust passage 24, which is caused by the movement of the inlet control valve 54 to reduce turbine inlet area 56A eventually causes the throttle valve 32 to move more toward an open position which in turn increases the exhaust gas mass flow. With the foregoing in mind, the operation of Figure 1 will now be described in more detail. In this description it will be assumed that the idle speed control unit 106 is set to provide an engine idle speed of 800 rpm. It will further be assumed that the low speed enable circuit 124 develops an output signal on line 128 at an engine speed which is slightly higher than the idle speed, for example 900 rpm where engine idle speed is 800 rpm. Assuming now that engine speed is below 900 rpm, the AND gate 90 will have an input signal applied thereto via line 128. The AND gate 90 will now output a signal on line 144 that is a function of the amount of current being supplied to the electrical loads 78 on the motor vehicle. The inlet control valve 54 will now be adjusted in accordance with the amount of current being supplied to the electrical loads 78 on the motor vehicle. Thus, as the electrical load 78 increases the inlet control valve 54 is moved to decrease the turbine inlet area 56A. Putting it another way, as the current sensed by winding 84 increases the back pressure in exhaust passage 24 is increased which in turn, by virtue of the idle speed control unit 106, causes the throttle valve 32 to move to a more open position thereby increasing the exhaust gas mass flow. Thus, as previously mentioned, the increasing electrical load, as sensed by winding 84, in effect causes the internal combustion engine to operate as a gas generator with sufficient exhaust gas mass flow to drive the gas turbine 40 at a speed that is high enough to cause a power level to be generated by the ac generator 66 that is sufficient to supply the electrical loads 78 on the motor vehicle. When the engine speed is above 900 rpm there is no signal output from the low speed enable circuit 124 and accordingly there is no output from the AND gate 90 with the result that the electric motor 130 is deenergized. The spring 62 now moves the inlet control valve 54 to a fully open position. At engine speeds above, for example 2000 rpm, the waste gate throttle valve 52 is opened to thereby bypass some of the exhaust gas being supplied to the gas turbine 40. In the design of the apparatus shown in Figure 1 the degree that the inlet control valve 54 restricts the turbine inlet area 56A will be related in some manner to the current output of the ac generator 66 as sensed by the winding 84. Thus, the apparatus can be arranged such that inlet control valve 54 remains in a completely open position until load current reaches some predetermined value. Above this predetermined value the inlet control valve 54 can be progressively moved toward a position that progressively reduces the turbine inlet area 56A as a function of increasing load current above the predetermined value.

Claims: 1. An electric power generating apparatus for a motor vehicle comprising an internal combustion engine having an intake passage (28) connected to the intake valves (16) of the internal combustion engine and an exhaust passage (24) connected to the exhaust valves (18) of the internal combustion engine, a throttle valve (32) for controlling the amount of air and fuel supplied to the internal combustion engine through the intake passage, the electric power generating apparatus comprising a gas turbine (40) having a rotor (42) and an inlet passage (56) connectable to the exhaust passage (24), the inlet passage having an inlet control valve (54) for controlling the effective turbine inlet area (56A), the inlet control valve causing the back pressure in the exhaust passage to increase as the turbine inlet area (56A) is reduced, an electric generator (66) connected to the rotor (42) of the gas turbine (40) so as to be driven thereby, an electrical load (76) on the motor vehicle connectable to the output of the electric generator; an engine speed control unit (106) responsive to engine speed for varying the position of throttle valve (32) to maintain engine speed at a predetermined value; and current sensing means (84-86) for sensing the output current of the electric generator (66); characterised by control means (88,90,120-151) coupled to the current sensing means and to the inlet control valve (54) for controlling the inlet control valve as a function of the magnitude of the current sensed by the current sensing means, the control means being operative to decrease the effective turbine inlet area (56A) to effect an increase in the output current of the electric generator (66). 2. An electric power generating apparatus according to claim 1, wherein the electric generator is an alternating current generator (66) and wherein the output winding (70) of the alternating current generator is connected to a bridge rectifier (72) for providing direct current to electrical loads (76,78) on the motor vehicle. 3. An electric power generating apparatus according to claim 2, wherein the current sensing means (84,86) senses the direct current output of the bridge rectifier (72).

Inventors: MICK, STANLEY H., WYCZALEK, FLOYD A.
Applicants: GENERAL MOTORS CORPORATION
Application year: 1989
Main classification: F02B41
IPC codes: F02D41, F01D15, F02B63, F01N5, F02D29, F02C6, F02B41