TURBOCHARGER WITH ROTARY ELECTRIC MACHINE

Abstract: A turbocharger with a rotary electric machine has a permanent magnet, or a nonmagnetized magnetic member, or surfaces of different light reflectivities on a rotatable member of the turbocharger, as a detectable means disposed in a position corresponding to the angular position of magnetic poles of the permanent magnet of a magnet rotor of the rotary electric machine. A detecting means is disposed in a position coacting with the detectable means for detect­ ing the angular position of magnetic poles of the magnet rotor. A shield means is provided for preventing the detectable means from being adversely affected by the mag­ netic field from the magnet rotor, oil, and dust, so that a detected signal of a high S/N ratio can be produced for accurately detecting the angular position of the magnetic poles of the magnet rotor as it rotates.

Description: The present invention relates to a turbocharger with a rotary electric machine, which can be driven by the energy of exhaust gases discharged from an internal combustion engine. There has been employed in recent years, a turbocharger having an exhaust turbine which is rotatable by the energy of exhaust gases from an internal combustion engine to drive a compressor mounted on the rotatable shaft of the exhaust turbine for charging air into the internal combustion engine. Japanese Laid-Open Patent Publication No. 59-101040 discloses an engine supercharging system including a rotary electric machine mounted on the rotatable shaft of a turbocharger combined with an internal combustion engine. When the internal combustion engine rotates at a low speed, the rotary electric machine operates as an electric motor to increase the boost pressure for increasing the power output from the engine. When the internal combustion engine rotates at a high speed, the rotary electric machine operates as an electric generator to produce electric power for charging a battery. Another turbocharger for an internal combustion engine, disclosed in Japanese Laid-Open Patent Publication No. 60-195329, includes a rotary electric machine mounted on the rotatable shaft of the turbocharger, the rotary electric machine being operable as an electric motor or as an electric generator depending on the operating conditions of the internal combustion engine. For operating a rotary electric machine having a rotor with a permanent magnet, it is necessary to control the phase of the electric power supplied to a stator depending on the rotation of the rotor in order to operate the rotary electric machine highly efficiently. The turbochargers disclosed in the above publications do not have any means for detecting the position of magnetic poles of the rotor which has a permanent magnet. Therefore, in the disclosed turbochargers, it is impossible to control the phase of electric power supplied to the stator dependent on the rotation of the rotor, and thus the rotary electric machine cannot efficiently be operated. EP-A-0159146 sets out to overcome this problem and discloses generally the use of a rotary position sensor in a turbocharger with an electric machine. Now, generally, a magnetic sensor or an optical sensor may be employed for detecting the angular position of a rotating body, but, if a magnetic sensor is used as a means for detecting the position of magnetic poles of a rotor having a permanent magnet in a rotary electric machine, it is difficult for the magnetic sensor to detect the exact angular position of the rotor because of the magnetic fields produced by the strong permanent magnet of the rotor or the intensive magnetic fields produced by a large current flowing through the coils of the stator when the rotary electric machine is operated as an electric motor. An optical sensor employing an optical fibre is advantageous in that it is not adversely affected by any magnetic field, but is disadvantageous in that it is susceptible to oil and dust, and its output signal is greatly lowered in level during operation over a long period of time, thus resulting in failure to detect the exact angular position of the rotor. It is an object of the present invention to provide a turbocharger with a rotary electric machine, which has a position detecting means for accurately detecting the angular position of magnetic poles of a rotor without being affected by a magnetic field or by oil and dust. According to the present invention, there is provided a turbocharger having a rotary electric machine, and including a turbine impeller drivable by the energy of exhaust gases emitted from an internal combustion engine, a rotatable shaft having one end coupled to the turbine impeller, a compressor impeller mounted on the other end of the rotatable shaft, a magnet rotor mounted on the rotatable shaft and having a permanent magnet, and a stator core disposed around the magnet core and having stator coils wound thereon, characterised by magnetically detectable means mounted on the compressor impeller for rotation therewith and disposed in a position corresponding to the angular position of a magnetic pole of the magnet rotor; a magnetic sensor disposed in a position confronting the magnetically detectable means for thus detecting the angular position of the rotor on rotation of the magnetically detectable means upon rotation thereof; and shield means disposed between the sensor and the rotary electric machine for protecting the magnetic sensor from influence by changes in the magnetic field resulting from rotation of the magnet rotor or from changes in the electric current flowing in the stator coils. Two examples of turbochargers according to the present invention will now be described with reference to the accompanying drawings in which:- Fig. 1(a) is a cross-sectional view of a turbocharger with a rotary electric machine; Fig. 1(b) is a cross-sectional view taken along line I - I of Fig. 1(a); Fig. 2(a) is a fragmentary cross-sectional view of a second turbocharger with a rotary electric machine; and, Fig. 2(b) is a cross-sectional view taken along line II - II of Fig. 2(a). As shown in Figs. 1(a) and 1(b), a turbocharger housing assembly 1 comprises a turbine housing 14, a compressor housing 12, and a central housing 13 disposed therebetween. A shaft 2 is rotatably supported in the housing assembly 1 by means of a pair of bearings 3. A turbine impeller 4 housed in the turbine housing 14 is mounted on one end of the shaft 2 and a compressor impeller 5 housed in the compressor housing 12 is mounted on the other end of the shaft 2. A rotary electric machine 6 is disposed on the rotatable shaft 2 in the central housing 13 and comprises a magnet rotor 61 mounted on the shaft 2, a stator core 62 disposed in confronting relation to the magnet rotor 61, and stator coils 63 wound on the stator core 62. The magnet rotor 61 is in the form of a cylindrical permanent magnet made of a rare earth element and having intensive residual magnetism. For operating the rotary electric machine 6 as an electric motor, an electric current is supplied to the stator coils 63. When the rotary electric machine 6 operates as an electric generator, electric power induced by the stator coils 63 is extracted. Between the rotor 61 and the compressor impeller 5, there is disposed a tubular spacer 7 fitted over the shaft 2. When the compressor impeller 5 is fastened to the shaft 2 by means of a nut 8, the spacer 7 keeps the rotor 61 and the compressor impeller 5 spaced a certain distance from each other. Permanent magnets 9 for detecting the position of magnetic poles are embedded in the back of the blades of the compressor impeller 5 and where the permanent magnet of the rotor 61 has two N and S poles, these magnets 9 are positioned in radial alignment with the respective N and S poles as shown in Fig. 1(b). A magnetic sensor 10 is supported in the central housing 13. The magnetic sensor 10 has on its inner tip end a detector coil 101 disposed in a radial position which confronts the permanent magnets 9 embedded in the back of the blades of the compressor impeller 5. The magnetic sensor 10 serves to detect the angular position of the magnetic poles of the magnetic rotor 61 rotating with the compressor impeller 5 by detecting a change in the magnetic field produced by movement of the permanent magnets 9 upon rotation of the compressor impeller 5. A detected signal is sent from the magnetic sensor 10 to a controller (not shown). A shield plate 11 is embedded in the central housing 13 between the magnetic sensor 11 and the magnet rotor 61. The shield plate 11 comprises an annular thin steel plate made of a magnetic material such as S10C, S25C, or the like. The shield plate 11 serves to absorb changes in the magnetic field due to rotation of the permanent magnet of the rotor 61 or due to changes in an electric current flowing through the stator coils 63, and to suppress noise which would otherwise be induced in the magnetic sensor 10 by such changes in the magnetic field. The turbocharger with the rotary electric machine thus constructed will operate as follows: The turbine impeller 4 is driven by the energy of exhaust gases emitted from an internal combustion engine to rotate the compressor impeller 5 which produces and supplies compressed air into the internal combustion engine. When the compressor impeller 5 is rotated, the permanent magnets 9 embedded in the back of the blades thereof are also rotated. A change in the magnetic field from the permanent magnets 9 is detected by the magnetic sensor 10, which then transmits a detected signal to the controller. Since the transmitted signal corresponds to the angular position of the magnetic poles of the magnet rotor 61, the phase or angular position of the magnetic poles of the magnet rotor 61 can accurately be detected. Since the shield plate 11 is disposed between the magnetic sensor 10 and the magnet rotor 61, the shield plate 11 absorbs changes in the magnetic field due to rotation of the permanent magnet of the rotor 61 or due to changes in an electric current flowing through the stator coils 63 and suppresses noise which would otherwise be induced in the magnetic sensor 10 by such magnetic field changes. Therefore, the detected signal from the magnetic sensor 10 has a good S/N ratio. Inasmuch as the permanent magnets 9, for detecting the angular position of the magnetic poles, are embedded in the back of the blades of the compressor impeller 5, they are not adversely affected by centrifugal forces produced when the compressor impeller 5 rotates at very high speeds, and it is easy to make adjustments for rotational balancing of the compressor impeller 5. Figs. 2(a) and 2(b) illustrate a turbocharger according to a second embodiment of the present invention. In the second embodiment, thin amorphous layers 91 of silicon steel are attached to the compressor impeller 5 in place of the permanent magnets 9 in the first embodiment. Those parts in Figs. 2(a) and 2(b) which are identical to those of Figs. 1(a) and 1(b) are denoted by identical reference numerals. In Figs. 2(a) and 2(b). a compressor impeller 5 is made of a non-magnetic material such as an aluminum alloy, and non-magnetized thin layers 91 of amorphous silicon steel are firmly deposited by evaporation on the compressor impeller 5 at radial positions corresponding to the N and S poles of the permanent magnet of a rotor 61. A magnetic sensor 100 has a magnetic pole and a detector coil for detecting a change in the magnetic field which is caused by a magnetic member approaching the magnetic sensor 100. Upon such detection, the detector coil transmits a signal to a (non-illustrated) controller as in the first example. When the compressor impeller 5 and the rotor 61 are rotated, the thin layers 91 of amorphous silicon steel on the compressor impeller 5 are also rotated, and changes are produced in the magnetic field by the aluminum-alloy compressor impeller 5 rotating near the magnetic sensor 100 and the non-magnetized ferromagnetic thin layers 91. Therefore, the magnetic sensor 100 transmits a detected signal each time one of the thin layers 91 moves past the magnetic sensor 100. Since the transmitted signal corresponds to the angular position of one of the magnetic poles of the rotor 61, the angular position of the magnetic poles of the rotor 61 as it rotates can accurately be detected. A shield plate 11 is also provided to protect the magnetic sensor 100 from the magnetic fields from the rotor 61 and the stator coils 63. Therefore, the detected signal from the magnetic sensor 100 has a good S/N ratio.

Claims: A turbocharger having a rotary electric machine (6), and including a turbine impeller (4) drivable by the energy of exhaust gases emitted from an internal combustion engine, a rotatable shaft (2) having one end coupled to the turbine impeller, a compressor impeller (5) mounted on the other end of the rotatable shaft, a magnet rotor (61) mounted on the rotatable shaft and having a permanent magnet, and a stator (62) core disposed around the magnet rotor and having stator coils (63) wound thereon, characterised by magnetically detectable means (9) mounted on the compressor impeller (5) for rotation therewith and disposed in a position corresponding to the angular position of a magnetic pole of the magnet rotor (61); a magnetic sensor (10) disposed in a position confronting the magnetically detectable means (9) for thus detecting the angular position of the rotor (61) on rotation of the magnetically detectable means upon rotation thereof; and shield means (11) disposed between the sensor (10) and the rotary electric machine (6) for protecting the magnetic sensor (10) from influence by changes in the magnetic field resulting from rotation of the magnet rotor (61) or from changes in the electric current flowing in the stator coils (63). A turbocharger according to claim 1, wherein the magnetically detectable means (9) is embedded in the back of a blade of compressor impeller (5). A turbocharger according to claim 1 or claim 2, wherein the magnetically detectable means comprises one or more permanent magnets. A turbocharger according to claim 1 or claim 2, wherein the magnetically detectable means comprises one or more non-magnetisable members. A turbocharger according to claim 4, wherein the non-magnetizable magnetic member is made of amorphous silicon steel. A turbocharger according to claim 5, wherein said non-magnetizable magnetic member of amorphous silicon steel is deposited by evaporation on the back of a blade of said compressor impeller. A turbocharger according to any of claims 1 to 6, wherein the shield means comprises an annular member in the form of a thin magnetic steel plate (11).

Inventors: HARA, SHINJI ISUZU FUJISAWA DAI, KOIZUMI, YOSHIHISA ISUZU TOTSUKA
Applicants: ISUZU MOTORS LIMITED
Application year: 1988
Main classification: F02B37
IPC codes: F02B39, H02K7, F02B37, F01D15, H02K29