Variable-reluctance-type angle sensor

Abstract: A variable-reluctance-type angle sensor having an output winding wound in each slot on a one-slot pitch basis and in a sinusoidal distribution. The variable-reluctance-type angle sensor is so structured that the number of the poles of exciting windings is equal to the number of slots and that the induced voltage in the output winding corresponding to one phase of n-phase output windings is sinusoidally distributed.

Description: The present invention relates to a variable-reluctance-type angle sensor, and in particular, to improvements in the variable-reluctance-type angle sensor that eliminate harmonic-frequency components, improve accuracy, and permit machine-winding by allowing the output winding to be wound in a distributed manner at slots on a one-slot pitch basis and in a sinusoidal configuration. Conventionally available as one type of angle sensor is a resolver illustrated in Figs. 1 through 4. Designated 1 in Fig. 1 is a ring-shaped stator having four slots 2, each formed between two of four neighboring projecting poles 3. A single phase exciting winding 4 is wound around each projecting pole 2 and in the slots beside the projecting pole 3. A rotor 5 that is formed of iron cores only and without winding on it is rotatably freely supported within the stator 1. The center of the rotor 5 is off-centered from the center of the stator 1. The rotor 5 is so arranged that permeance of the gap between the rotor 4 and the projected pole 3 of the stator 1 varies sinusoidally with respect to angle . SIN and COS output windings 6, 7, with an electrical angle of 90° allowed therebetween, are provided. Either a COS winding or a SIN winding is wound around each of the projecting poles 3 and in the slots 2 in the stator 1. The SIN output winding 6 gives an SIN output voltage 8 as a sine wave, and the COS output winding 7 gives a COS output voltage 9 as a cosine wave. As shown in Fig. 2, the SIN output winding 6 and the COS output winding 7 are arranged in each slot 2 for single slot excitation, and the exciting winding 4 is arranged sequentially in each slot 2 on a one-slot pitch basis. As shown in Fig. 3, when the exciting voltage is supplied via the exciting winding 4, the SIN output winding 6 and the COS output winding 7 output the SIN output voltage 8 designated c+D and the COS output voltage 9 designated a+B in response to the rotation of the rotor 5, as shown in Fig. 4 and as shown in marks a, B, c, D in Fig.4. The prior art variable-reluctance-type angle sensor thus constructed suffers the following problem. The prior art variable-reluctance-type angle sensor picks up as a voltage variation the variation in magnetic flux that crosses the output windings. The magnetic flux varies when the gap between the rotor and stator varies. The output voltage changes are respectively proportional to SIN  and COS . Because of tolerance or variations in the configuration of the rotor, harmonic-frequency components are generated and accuracy improvements are extremely difficult. A fractional pitch winding may be employed in the output winding as shown in Fig. 3 to remove harmonic-frequency components. This technique, however, requires that the exciting winding and the output windings skip alternate slots, and thus machine-winding is impossible. EP-A-0 527 673 discloses a sensor similar to that shown in Figure 3 of this application. The exciting winding and the output windings again are not wound through adjacent slots - that is, each turn is not wound around a single pole. The excitation winding is wound on a cylindrical portion of the stator, the output winding being provided in the stator notches so that the voltage induced is sinusoidal and represents, apart from phase-shift, the position of the rotor relative to the stator. Machine-winding is again not possible. An angle sensor similar to that shown in Figure 1 is disclosed by EP-A-0522941. The excitation and reception windings are wound on the poles of the stator, the excitation windings being connected together in series phase by phase and the reception winding of the same phase and offset by 180° are connected together in series. The rotor comprises a number of lobes. The present invention provides a variable-reluctance-type angle sensor comprising: a stator having a plurality of slots, each pair of adjacent slots defining a pole; an exciting winding disposed on the stator; an n-phase output winding disposed on the stator; and a rotor rotatably supported relative to the stator, the rotor having an iron core with no windings thereon and having a configuration such that the gap permeance between the stator and the rotor varies sinusoidally with respect to the angle of rotation () of the rotor relative to the stator; said angle sensor being characterised in that the exciting winding is wound sequentially and with alternating polarity around a plurality of individual poles of the stator and each of the output windings are wound around the plurality of individual poles of the stator; in that the exciting winding is wound around each individual pole of the stator; in that the number of turns of the output windings wound around each individual pole of the stator varies sinusoidally around the stator; and in that the direction of the output windings on each individual pole are determined so that the respective output voltages correspond with the sine and cosine wave. Preferably, an n-phase excitation/single-phase output structure is arranged by using the exciting winding as an output winding and the output windings as exciting windings. According to the variable-reluctance-type angle sensor of the present invention, the exciting winding and output windings are wound in each slot on a one-slot pitch basis, and the output windings are wound in a distributed fashion so that the distribution of the voltage induced in the output windings is sinusoidal. Therefore, regardless of one-slot pitch winding at each slot, each output winding presents an SIN output voltage and COS output voltage according to the rotation of the rotor. According to the variable-reluctance-type angle sensor of the present invention, harmonic components from low to high frequencies contained in each induced voltage are reduced. Since each slot is filled with winding on a one-slot pitch basis, machine-winding using a machine is possible. Fig. 1 shows the construction of the prior art angle sensor. Fig. 2 is an explanatory view showing the winding structure in each slot in the angle sensor of Fig. 1. Fig. 3 shows the prior art winding structure. Fig. 4 shows the waveforms of the output voltages of the output windings. Fig. 5 shows generally the variable-reluctance-type angle sensor according to the present invention. Fig. 6 is an explanatory view showing the winding structure in each slot according to the present invention. Referring to the drawings, a preferred embodiment of the variable-reluctance-type angle sensor according to the present invention is now discussed. In the discussion that follows, components equivalent to those described with reference to the prior art are designated with the same reference numerals and their explanation will not be repeated. Designated 1 in Fig. 5 is a ring-shaped stator having 12 projecting poles 3, and 12 slots 2, each formed between two neighboring projecting poles 3. An exciting winding 4 of one phase is wound around each projecting pole 3 and in the respective slots 2. The number of the poles of the exciting windings 4 is equal to the number of the slots 2. A rotor 5 constructed of iron cores without any winding thereon is freely rotatably supported within the stator 1. Since the center of the rotor 5 is off-centered from the center of the stator 1, gap permeances between the rotor 5 and the projecting poles 3 of the stator 1 sinusoidally vary with respect to angle  as well known in the art. The rotor 5 is not limited to the off-centered structure. Alternatively, the same effect may be achieved by a rotor 5 which is center-aligned but deformed in its shape to have projections and recesses. SIN output winding 6 and COS output winding 7, with their two phases having an electrical angle of 90° therebetween, are wound in the slots on a one-slot pitch basis (the slots are filled with respective winding, sequentially rather than in an alternately skipped fashion). As shown in Fig. 6, though not shown in Fig. 5, the SIN and COS output windings 6, 7 are wound so that the number of turns of each winding around a pole varies in a sinusoidal manner so that the induced voltage has a sinusoidal waveform. The numbers of the turns of the output windings 6, 7 are proportional to SIN , CDS , respectively. Their polarities are arranged in consideration of the polarities of the exciting windings so that the polarities of the SIN and COS output windings 6, 7 agree with the polarities of the SIN and COS output voltages 8, 9 at each of the slot positions. As shown in Fig. 6, the exciting winding 4 in normal winding and the output windings 6, 7 in normal winding result in in-phase output, the exciting winding 4 in normal winding and the output windings 6, 7 in reverse winding result in reversed-phase output, the exciting winding 4 in reverse winding and the output windings 6, 7 in normal winding result in reversed-phase output, and the exciting winding 4 in reverse winding and the output windings 6, 7 in reverse winding result in in-phase output. The polarities of the output windings 6, 7 are determined (the positive pole is given by a reverse winding) so that SIN output voltage 8 and COS output voltage 9 agree with sine wave and cosine wave, respectively. The construction in Fig. 5 illustrates 1X, two-phase output (X means number of multiple). The present invention can be applied to n-phase output type and multi-pole output type (2X or greater). The present invention is not limited to the above-described 12-slot type, and a different number of slots may be used. Fig. 5 illustrates one-phase excitation/n-phase (2-phase) output. Alternatively, the excitation side and output side may be reversed. Namely, an arrangement of n-phase (2-phase) excitation/one-phase output may be incorporated. There are two possible constructions for the winding: namely, the windings can be wound around the poles 3 or can be preformed and inserted into the slots 2. The variable-reluctance-angle sensor thus constructed according to the present invention offers the following advantages. The output windings are wound on a one-slot pitch basis and the numbers of the turns (the quantity) of the output windings are set to agree with a sinusoidal distribution. The harmonics from low to high frequencies contained in the output voltages (induced voltages) are reduced, and thus angle sensor accuracy is improved compared to the prior art (to the error level half to one-fifth that of the prior art). Since the sinusoidal distribution is arranged by one-slot pitch winding, winding is automated using machine-winding. This results in a substantial cost reduction.

Claims: A variable-reluctance-type angle sensor comprising: a stator (1) having a plurality of slots (2), each pair of adjacent slots defining a pole (3); an exciting winding (4) disposed on the stator; an n-phase output winding (6,7) disposed on the stator; and a rotor (5) rotatably supported relative to the stator (1), the rotor having an iron core with no windings thereon and having a configuration such that the gap permeance between the stator (1) and the rotor (5) varies sinusoidally with respect to the angle of rotation () of the rotor (5) relative to the stator (1); said angle sensor being characterised in that the exciting winding (4) is wound sequentially and with alternating polarity around a plurality of individual poles (3) of the stator (1) and each of the output windings (6,7) are wound around the plurality of individual poles (3) of the stator (1); in that the exciting winding (4) is wound around each individual pole of the stator (3); in that the number of turns of the output windings (6,7) wound around each individual pole (3) of the stator (1) varies sinusoidally around the stator (1); and in that the direction of the output windings on each individual pole are determined so that the respective output voltages correspond with the sine and cosine wave. The variable-reluctance-type angle sensor according to Claim 1, wherein an n-phase excitation/single-phase output structure is arranged by using the exciting winding as an output winding and the output windings as exciting windings.

Inventors: KITAZAWA KANJI, KITAZAWA, KANJI
Applicants: TAMAGAWA SEIKI CO LTD, TAMAGAWA SEIKI KABUSHIKI KAISHA
Application year: 1996
Main classification: G01D5
IPC codes: G01B7, G01D5