Method for modulating torque of vehicle driving motor

Abstract

To provide a vehicle driving motor that realizes torque variations similar to those of an internal combustion.SOLUTION: A method is for modulating a torque of a vehicle driving motor that is driven by first, second and third periodical currents which have a phase angle of 120° relative to each other and are applied in response to a rotational magnetic field created by a rotor. The method includes generating the first, second and third periodical currents by applying a pulse-modulated voltage pulse to switching elements, and applying a phase difference to the first, second and third periodical currents with respect to the rotational magnetic field or applying an amplitude modulation to the first, second and third periodical currents.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The following disclosure relates to a method for modulating the torque of a vehicle drive motor, and in particular to a method for modulating the torque of a vehicle drive motor driven by periodic currents having equidistant phase differences. [Background technology]

[0002] In the field of transportation equipment, internal combustion engines have been the predominant form of vehicle power, but vehicles using internal combustion engines are rapidly being replaced by vehicles using electric motors. The use of electric motors is not only effective in reducing carbon dioxide emissions, but can also contribute to ease of driving, such as by providing excellent acceleration from low speed ranges.

[0003] Normally, motors for driving vehicles use permanent magnet synchronous motors, in which the rotor has a permanent magnet and the stator has a coil. In such motors, control by an external circuit replaces the inherent rectification function, and torque is generated by applying a current synchronized with a rotating magnetic field to the coil. Optimizing current control suppresses torque ripple, enabling smooth driving.

[0004] Patent Documents 1 and 2 disclose related techniques. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-150498 A [Patent Document 2] Patent Publication No. 2022-048802 Summary of the Invention [Problem to be solved by the invention]

[0006] In the past, vehicle drive motors have aimed to achieve smooth torque output without ripples, for example by using an inverter circuit to control current appropriately. This realizes a smooth driving feel that is difficult to obtain in vehicles using internal combustion engines. However, according to the research of the present inventors, it has become clear that the absence of torque ripples is not always advantageous, and that when driving on uneven ground such as deep sand, for example, appropriate torque fluctuations are more advantageous for recovering traction.

[0007] The technology disclosed below relates to a method for modulating the torque of a vehicle drive motor to achieve torque fluctuation similar to that of an internal combustion engine. [Means for solving the problem]

[0008] According to one aspect, a method for modulating torque of a vehicle drive motor driven by first, second and third periodic currents having a phase angle of 120° with respect to each other and applied in response to a rotating magnetic field generated by a rotor includes generating the first, second and third periodic currents by applying pulse-width modulated voltage pulses to switching elements, respectively, and imparting a phase difference to the first, second and third periodic currents with respect to the rotating magnetic field, or imparting amplitude modulation to the first, second and third periodic currents.

[0009] Preferably, the method further comprises generating the phase difference by lagging the voltage pulse with respect to the rotating magnetic field. Also preferably, the method further comprises generating the amplitude modulation by periodically modulating a width of the voltage pulse. Alternatively, the method further comprises generating the amplitude modulation by modulating a gain of the generated first, second and third periodic currents. Effect of the Invention

[0010] Torque fluctuations similar to those of an internal combustion engine are realized in a vehicle drive motor. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing an example of torque fluctuations in the power generated by a conventional internal combustion engine. [Diagram 2] FIG. 2 is a graph showing an example of three-phase AC current and torque applied to a conventional vehicle drive motor. [Diagram 3] FIG. 3 is a graph showing an example of torque modulated by imparting a phase difference to an applied current. [Figure 4] FIG. 4 is a graph showing an example of torque modulated by modulating the applied current. [Diagram 5] FIG. 5 is a circuit diagram illustrating an example of a circuit for generating an alternating current. [Figure 6] FIG. 6 is a graph that illustrates a schematic example of a pulse-width modulated voltage pulse and the alternating current generated thereby. [Figure 7] FIG. 7 is a graph that diagrammatically illustrates another example of a pulse-width modulated voltage pulse and the alternating current generated thereby. [Figure 8] FIG. 8 is a circuit diagram illustrating another example of a circuit for generating an alternating current. [Figure 9] FIG. 9 is an example of a circuit for modulating a voltage pulse. [Figure 10] FIG. 10 is a circuit diagram illustrating yet another example of a circuit for generating an alternating current. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Several exemplary embodiments are described below with reference to the accompanying drawings.

[0013] For example, in a four-stroke gasoline engine, the crankshaft rotates twice and the four processes of intake, compression, combustion, and exhaust are repeated. Of these, only the combustion process generates torque, and the other processes act as resistance. Usually, two or more cylinders with different crank angles are combined so that the processes do not overlap, and the resultant torque T EAs shown in Figure 1, periodic fluctuations appear in the

[0014] In a conventional vehicle drive motor, periodic currents with a phase difference of, for example, 120° in electrical angle are applied to three sets of coils in sequence to generate a rotating magnetic field synchronized with the rotation of the rotor. If a sinusoidal AC current is used as the periodic current and is appropriately controlled, it is possible to generate a torque T with almost no ripple, as shown in FIG. M Up until now, ripple-free torque has been the focus of attention due to its low noise and vibration characteristics.

[0015] In each of the embodiments described below, a vehicle drive motor achieves torque fluctuations similar to those of an internal combustion engine.

[0016] In three-phase sinusoidal drive, when the current applied to the rotor is synchronous with the rotation of the rotor, the generated torque follows the formula below.

[0017]

number

[0018] Here, Kt is the torque coefficient of the motor, I0 is the total applied current, and φ is the electrical angle.

[0019] Each of the three terms on the right-hand side generates a torque that fluctuates periodically, but when the three terms are added together, the fluctuations cancel each other out, resulting in a generated torque without ripples as shown in Figure 2. However, when a slight phase difference or lag θ is intentionally given to the applied current with respect to the rotating magnetic field, the generated torque follows the following formula.

[0020]

number

[0021] The torque fluctuations are not cancelled out by adding them together, and the generated torque T M is obtained.

[0022] Alternatively, the torque T can be generated by applying amplitude modulation to the applied current I0. M can be modulated. Figure 4 shows one such example. The modulation obtained by the phase difference described above is typically sinusoidal as in the example of Figure 3, but any waveform can be realized by reflecting the modulation by amplitude modulation of the current I0.

[0023] Alternatively, the generated torque can be modulated by frequency modulation. However, since this can easily cause step-out in a short period of time, it may be possible to use frequency modulation when you want to cause modulation for only a short period of time.

[0024] A specific means for modulating the torque of a vehicle drive motor will be described below with reference to Fig. 5. The circuit 1 includes a power supply 3 and three sets of switching elements S1, S2, and S3, each of which has its output connected to the input of a coil 5 of the motor. For each of the switching elements S1, S2, and S3, an insulated gate bipolar transistor can be used, for example, but is not limited to this.

[0025] When a width-modulated voltage pulse P is input to the gates of the switching elements S1, S2, and S3, corresponding periodic currents C1, C2, and C3 are output from each output terminal. Figure 6 shows an example of the relationship between the input voltage pulse P and the output wave C, and in this example, a sine wave is output. By changing the input pulse width modulation, any output wave can be obtained. In the example shown in Figure 7, a distorted sine wave is output. As can be easily understood, if the input voltage pulse P is delayed, a delay also appears in the output wave C, which means that a phase difference can be given to the periodic current with respect to the rotating magnetic field. The amplitude of the output wave C can also be modulated by modulating the input voltage pulse P.

[0026] To modulate the voltage pulse P, for example, a circuit as shown in Fig. 8 can be used. That is, another circuit for modulation is added to each gate of the switching elements S1, S2, and S3, and the input voltage pulse P is modulated by applying a waveform for modulation to each circuit. In such an example, the basic voltage pulse P is the same as the conventional one, and modulation occurs by applying a modulating wave M to the added circuit. The added circuit can be, but is not limited to, grounded emitter circuits D1, D2, and D3 as shown in the example.

[0027] Alternatively, the basic voltage pulse P may be pre-modulated. FIG. 9 shows such an example, where the voltage pulse P is modulated by the logic operation element A. M Such a voltage pulse P M By inputting this to a circuit such as that shown in FIG. 6, the amplitude of the output wave C can be modulated.

[0028] Alternatively, as shown in FIG. 10, a circuit C M Add circuit C M The amplitude of the output wave C may be modulated by the action of

[0029] According to this embodiment, the torque generated by the motor for driving a vehicle can be modulated with a simple configuration. The modulated generated torque is advantageous for recovering traction depending on the road surface conditions. Moreover, the modulated generated torque is sufficiently similar to that generated by an internal combustion engine, and is expected to be felt favorably rather than unnaturally by drivers who are accustomed to driving conventional vehicles. Moreover, whether the generated torque is constant or modulated can be easily controlled by turning on and off the function of an added circuit. For example, the driver of the vehicle can select whether or not to modulate the torque depending on the road surface conditions by operating a switch at hand, or under automatic control by the vehicle.

[0030] Although several embodiments have been described, the embodiments can be modified or altered based on the above disclosure. [Industrial Applicability]

[0031] A method for modulating torque in a vehicle traction motor is provided. [Explanation of symbols]

[0032] 1 Circuit 3 Power supply 5 Coil C,C1,C2,C3 periodic current C M circuit M Modulated Wave P Pulse S1, S2, S3 switching elements T E Resultant Torque T M Generated torque

Claims

1. A method for modulating torque of a vehicle traction motor driven by first, second and third periodic currents having a phase angle of 120° with respect to each other and applied in response to a rotating magnetic field generated by a rotor, comprising the steps of: applying pulse-width modulated voltage pulses to respective switching elements to generate the first, second and third periodic currents; imparting a phase difference to the first, second and third periodic currents with respect to the rotating magnetic field, or imparting amplitude modulation to the first, second and third periodic currents; The method comprises:

2. generating the phase difference by lagging the voltage pulse with respect to the rotating magnetic field; The method of claim 1 further comprising:

3. generating said amplitude modulation by imparting a periodic modulation to the width of said voltage pulses; The method of claim 1 further comprising:

4. generating the amplitude modulation by modulating gains of the first, second and third periodic currents; The method of claim 1 further comprising:

Images