JP2009035028A - Torque fluctuation reducing device for hybrid vehicle - Google Patents

Abstract

A torque fluctuation reducing device for a hybrid vehicle capable of suppressing torque fluctuation without adversely affecting the fuel consumption of an engine is proposed.
A torque fluctuation reducing device for a hybrid vehicle having an engine (1) and a motor (2), wherein the engine torque waveform and the motor cogging torque waveform are set to a predetermined relationship in which the engine torque fluctuation is reduced. Then, the engine and the motor are connected. Since the motor cogging torque waveform and the engine torque waveform are set to have a predetermined relationship for reducing the engine torque fluctuation, the engine torque fluctuation can be reduced without energizing the motor. Therefore, torque variation can be suppressed with a simple configuration without deteriorating the fuel consumption of the engine.
[Selection] Figure 1

Description

  The present invention relates to a torque fluctuation reducing device for a hybrid vehicle. More specifically, the present invention relates to an apparatus that is applied to a hybrid vehicle equipped with an engine and a motor and that reduces torque fluctuations that occur when the engine is driven.

  In recent years, hybrid vehicles have attracted particular attention from the viewpoints of fuel economy and environmental protection. A hybrid vehicle uses a plurality of drive sources in combination, but a vehicle equipped with an engine (internal combustion engine) and a motor (electric motor) is generally used.

  However, at present, the majority of vehicles are equipped with only an engine. For a vehicle equipped with an engine alone, suppression of torque fluctuation that occurs during driving is regarded as one of the important technical problems to be solved, and many studies have been made heretofore. For this reason, even in the case of a hybrid vehicle that employs an engine as one of the drive sources, suppression of torque fluctuation is also an important technical issue. For example, Patent Document 1 proposes a control device for a hybrid vehicle. This control device suppresses torque fluctuations by generating a damping torque that changes in a rectangular wave shape in a traveling motor connected to an engine.

JP 2005-65408 A

  In the control device of Patent Document 1, a command value of a pulse waveform of minus torque is applied to the motor in the combustion (explosion) stroke of the engine, and plus torque in the other strokes. By controlling the motor in this way, engine torque fluctuations are reduced. However, in the above control, an operation of reversing the direction of the output torque of the motor is executed in the engine explosion stroke and other strokes. As a result, since the motor is constantly energized to consume electricity, the fuel consumption on the engine side is deteriorated accordingly.

  Therefore, an object of the present invention is to propose a torque fluctuation reducing device for a hybrid vehicle that can suppress torque fluctuation without adversely affecting the fuel consumption of the engine.

  For the above purpose, a torque fluctuation reducing device for a hybrid vehicle according to the present invention is a torque fluctuation reducing device for a hybrid vehicle having an engine and a motor, wherein the torque waveform of the engine and the cogging torque waveform of the motor are The engine is characterized in that the engine and the motor are connected to each other with a predetermined relationship in which the torque fluctuation of the engine decreases.

  According to the hybrid vehicle torque fluctuation reducing apparatus of the present invention, the motor cogging torque waveform and the engine torque waveform are set to have a predetermined relationship for reducing the engine torque fluctuation. The torque fluctuation of the engine can be reduced without doing so. Therefore, torque variation can be suppressed with a simple configuration without deteriorating the fuel consumption of the engine.

  Hereinafter, an example suitable as one embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a drive unit of a hybrid vehicle to which a torque fluctuation reducing device according to an embodiment of the present invention is applied. As shown in the figure, the engine 1 and the motor 2 of the hybrid vehicle are connected via a connecting portion 3. Here, a differential device constituted by a planetary gear train is attached to the output shaft 4 of the engine 1 as the connecting portion 3, and the engine 1 and the motor 2 are connected via this differential device. The motor 2 is connected to a ring gear RG, and the output shaft 4 of the engine 1 is connected to a sun gear SG. A planetary gear PG is set on the carrier CA fixed at a fixed position. With these gears, the speed ratio between the engine 1 and the motor 2 can be set. Therefore, as will be described later, the period of the cogging torque waveform of the motor 2 can be adjusted so as to correspond to the period of the torque waveform of the motor 1 as necessary.

  The engine 1 is a conventional general internal combustion engine, and generates torque from the output shaft 4 through intake, compression, combustion (explosion), and exhaust strokes (combustion cycle). At this time, torque fluctuations periodically occur. Torque fluctuations induce engine vibration and noise and reduce the commercial value of the vehicle, so it is desirable to reduce it as much as possible. In this regard, the torque fluctuation reducing device of the present embodiment embodies a new technical idea of canceling the torque fluctuation of the engine 1 using the cogging torque of the motor 2.

  The cogging torque of the motor is a magnetic attractive force generated when the rotor (rotor) is rotated in a non-energized (non-excited) state. In other words, it is the holding torque generated when the rotor is rotated at an ultra-low speed. This cogging torque is a torque generated with a predetermined phase for each motor, and is often an unfavorable torque when performing control. The present invention actively uses such cogging torque to efficiently reduce torque fluctuation with a simple configuration.

  FIG. 2 is a diagram showing the state of torque (output) generated by the engine 1 in the combustion cycle, with the horizontal axis being the crank angle and the vertical axis being the torque. As can be seen from FIG. 2, the torque waveform ET of the engine 1, which is an output curve, is characterized as a constant phase. In this torque waveform ET, the position of a particularly large mountain (upwardly convex peak) corresponds to the combustion (explosion) stroke. The position of the valley (the peak that protrudes downward) corresponds to the compression stroke. The larger the torque waveform ET is in a shape including peaks and valleys, the larger the engine that generates torque fluctuations.

  In contrast, the torque fluctuation reducing device of the present embodiment suppresses the torque fluctuation of the engine 1 so that the torque waveform of the engine 1 and the cogging torque waveform of the motor 2 have a predetermined relationship in which the torque fluctuation of the engine 1 decreases. Is set to To briefly explain the basic concept, as shown in FIG. 2, the phase of the cogging torque waveform CT of the motor 2 is adjusted to the opposite phase to the torque waveform ET of the engine, and The value is reduced by cogging torque (cancelled) to suppress torque fluctuation. Therefore, in the torque fluctuation reducing apparatus of the present embodiment, the phase of the cogging torque CT of the motor 2 is adjusted as appropriate so that the torque waveform of the engine 1 and the mountain valley are reversed. That is, “valley-mountain” of the cogging torque waveform CT corresponds to “mountain-valley” of the torque waveform ET of the engine 1. In FIG. 2, a combined torque waveform RT is shown as a combined result of the two torque waveforms, and it can be confirmed that the peak value is reduced from the torque waveform ET. In this way, part of the engine torque fluctuation can be reduced by cogging torque. When it is difficult to cancel the peak of the cogging torque waveform having the opposite phase to the torque waveform of the engine 1 over the entire range, a large peak (a peak generated with the combustion stroke) is obtained. It is desirable to adjust the phase of the cogging torque waveform so as to reduce.

  The torque fluctuation reducing device of the present embodiment can suppress the torque fluctuation of the engine 1 with a simple configuration without energizing the motor 2. Therefore, torque fluctuation can be reduced without deteriorating the fuel consumption of the engine 1. In addition, as shown in the upper part of FIG. 2, the engine speed before adding the cogging torque is indicated by a broken line, and the engine speed after adding the cogging torque is indicated by a solid line. It is confirmed.

  FIG. 3 is a diagram for confirming the effect when the phase adjustment of the cogging torque of the motor 2 is performed as described above so as to cancel the torque fluctuation of the engine 1. The vertical axis represents the rotational speed fluctuation reduction rate. Torque fluctuation suppression effect is more effective in the case of low speed rotation (eg 1100 rpm) indicated by low speed 1 or ultra-low speed rotation (eg 700 rpm) indicated by low speed 2 than in the case of high speed rotation (eg 4000 rpm) or medium speed rotation (eg 2000 rpm). Can be confirmed to be high. In general, the vibration in the passenger compartment based on engine drive is more conscious of the occupant during low-speed operation or idle operation than during medium-high speed operation or high-speed operation. Is desired. Therefore, in the torque fluctuation reducing device of this embodiment, it is desirable to set the phase of the cogging torque waveform so as to reliably suppress the torque fluctuation at the time of low rotation and low load. Thereby, it can be set as the torque fluctuation reduction apparatus which can suppress a torque fluctuation effectively.

  The cogging torque of the motor 2 depends on the shape of the core (magnet) and the core around which the coil is wound. In particular, the relationship between the number of slots set in the core and the number of magnet poles is important. FIG. 4 is a diagram collectively showing a state in which the number of poles and the number of slots are variously changed. One cycle is an electrical angle of 60 ° (degrees), and the half cycle is a magnetic stable point where the cogging torque is zero (0). In the figure, for example, “4-6” is a cogging torque of a motor in which a magnet has four poles and the number of slots is set to six.

From FIG. 4, when the number of poles of the magnet is smaller than the number of slots, a relatively high value of cogging torque is obtained in the following combinations “4-6”, “6-9”, and “8-12”. These can be summarized as one group (first group) in which the ratio of the number of poles to the number of slots is “number of poles: number of slots = 2: 3”. On the other hand, “10-12” and “8-9” have relatively low values of cogging torque.
Further, when the number of poles of the magnet is larger than the number of slots, a relatively high value of cogging torque is obtained in the following combinations “8-6” and “12-9”. These can be summarized as another group (second group) in which the ratio of the number of poles to the number of slots is “number of poles: number of slots = 4: 3”. On the other hand, “10-9” and “14-12” have relatively low values of cogging torque.

  It should be noted that a relatively large cogging torque is obtained when the least common multiple of the number of poles and the number of slots is relatively small, such as 12, 24, and 36, as compared with the case where the least common multiple is large, such as 60, 72, 84, and 90. Is generated. The first group has a peak cogging torque at an electrical angle of less than 10 °, whereas the second group has a peak at an electrical angle of 10 ° to 20 °.

  As understood from the above description, the phase of the cogging torque waveform to be generated can be adjusted by appropriately designing the number of poles and the number of slots of the motor 2 connected to the drive shaft of the engine 1. Therefore, a torque fluctuation can be suppressed by designing a cogging torque waveform having an opposite phase to the torque waveform of the engine 1.

  The relative position of the cogging torque waveform with respect to the torque waveform can be adjusted by adjusting the position (position in the rotational direction of the rotor) when the motor 2 is fixed to the engine 1. More specifically, when the engine 1 is stopped, the position of the cogging torque waveform (position relative to the crank angle) can be adjusted by appropriately changing the installation position of the motor 2 in the rotor rotation direction.

  Further, as described above, it is possible to easily match the cycle of the cogging torque waveform of the motor 2 with the cycle of the torque waveform of the engine 1. For example, when the engine 1 is a four-cylinder engine, one cycle of the torque waveform is 180 °. On the other hand, as described with reference to FIG. 4, one cycle of the cogging torque waveform of the motor 2 is 60 °. Therefore, the cycle can be matched by setting the gear ratio of the connecting portion 3 shown in FIG. 1 so that the engine rotation is three times the motor rotation.

  Furthermore, a torque fluctuation reducing device having a more preferable structure capable of suppressing generation of noise (combustion noise) based on engine torque fluctuation will be described. FIG. 5 is a diagram for explaining a preferred phase adjustment example of the cogging torque of the motor 2 from the viewpoint of noise reduction. As in FIG. 2, the fine broken line indicates the engine torque ET, the broken line indicates the cogging torque CT, and the solid line indicates the combined torque RT. Further, in FIG. 5, the combustion stroke of the engine 1 is shown to start from a point where the crank angle is zero (0) ° and a point where the crank angle is 180 °.

  Accordingly, the zero (0) ° point and the range from the 180 ° point to the peak (peak) correspond to regions where the torque increases rapidly, and the zero and 180 ° points are the slopes of the tangent LT of the torque waveform. Is the largest point. As the height (peak) of the mountain increases, the torque fluctuation increases, but not only that, the slope of the tangent LT of the torque waveform at the zero point and the 180 ° point increases. Thus, the combustion noise increases when the inclination of the tangent LT increases. The inclination of the tangent LT indicates the temperature increase rate of the in-cylinder temperature of the engine 1, and an increase in the inclination of the tangent LT indicates an increase in combustion noise.

  Therefore, in FIG. 5, in the constant region on the right side from the zero point and the 180 ° point, the cogging torque waveform of the motor 2 is opposite in phase to the engine torque waveform, and the phase is set so that the valley peak (see VP) comes. It is preferable to set. That is, the noise is attenuated by setting an opposite phase so that the peak of the cogging torque CT of the motor 2 comes in a region where the torque increases in the combustion stroke of the engine 1. In this way, the torque waveform curve (ET) in which the slope of the tangent increases at the rising edge of the torque waveform is corrected with the cogging torque curve (CT) to obtain a torque waveform curve (RT) in which the slope of the tangent is reduced. it can. Therefore, noise can be suppressed thereby.

  The torque fluctuation reducing device according to the embodiment described above is configured to suppress the torque fluctuation generated when the engine 1 is driven by the cogging torque of the motor 2 connected to the engine 1. Torque fluctuation can be suppressed without any problem. Therefore, this torque fluctuation reducing device can efficiently suppress the torque fluctuation with a simple configuration without deteriorating the fuel consumption of the engine. Therefore, a hybrid vehicle employing such a torque fluctuation reducing device can suppress vibration and noise during driving, and can be provided as a vehicle that takes into account improvement in fuel consumption.

(Modification)
Although the said Example illustrated the case where the transmission unit comprised by the gear train was comprised in the connection part, it is not restricted to this. FIG. 6 shows a modification in which another connecting portion 30 is interposed between the engine 1 and the motor 2. When the amplitude and cycle of the cogging torque waveform of the motor 2 are in reverse phase with respect to the torque waveform of the engine 1 in advance, the configuration of the connecting portion can be simplified. This modification is for such a case, and as the connecting portion 30 in FIG. 6, a fixed gear that does not change the phase of the cogging torque, or one that directly connects the motor 2 to the output shaft of the engine 1 is used. In this way, a structure in which the motor 2 is connected to the drive shaft of the engine 1 without using a transmission may be employed.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

  As described above, according to the torque fluctuation reducing device for a hybrid vehicle of the present invention, the motor cogging torque waveform is set to have a predetermined relationship with the engine torque waveform to cancel the engine torque fluctuation. Therefore, engine torque fluctuations can be reduced without energizing the motor. Therefore, torque variation can be suppressed with a simple configuration without deteriorating fuel consumption.

  The waveform of the cogging torque may be set in an opposite phase to the torque waveform of the engine. Thereby, the peak value can be reduced by setting the valley-mountain to the waveform of the cogging torque so as to cancel the peak-valley of the torque waveform of the engine. Therefore, it is possible to reliably reduce the torque fluctuation and suppress the occurrence of vibration.

  Further, the phase may be adjusted so that the cogging torque has an antiphase peak in a region where the torque change rate increases in the combustion stroke of the engine. As a result, noise can be reduced by laying the engine torque waveform so that the slope of the rising portion becomes small.

  In addition, a transmission unit may be provided in a connecting unit that connects the engine and the motor, and a gear ratio of the transmission unit may be set based on a combustion cycle period of the engine / a period of the cogging torque. Thereby, the cycle of the cogging torque can be matched with the torque of the engine, and the torque fluctuation can be reliably reduced. Similarly, the gear ratio may be set based on the combustion cycle angle of the engine / the angle of the cogging torque.

It is the figure which showed schematic structure of the drive part of the hybrid vehicle to which the torque fluctuation reduction apparatus which concerns on one Example of this invention is applied. It is the figure which showed the mode of the torque which the engine shown in FIG. 1 generate | occur | produces in a combustion cycle. It is the figure which confirmed the effect at the time of performing the phase adjustment of the cogging torque of a motor and setting so that an engine torque fluctuation may be canceled. It is the figure which showed collectively the mode when changing the number of poles and the number of slots variously. It is the figure shown in order to demonstrate the preferable phase adjustment example of the cogging torque of a motor from the point of noise reduction. It is the figure which showed the modification which interposed the other connection part between the engine and the motor.

Explanation of symbols

1 Engine 2 Motor 3, 30 Connection ET Engine torque waveform CT Cogging torque waveform RT Synthetic torque waveform

Claims (4)

A torque fluctuation reducing device for a hybrid vehicle having an engine and a motor,
The torque waveform of the engine and the cogging torque waveform of the motor are set to a predetermined relationship in which the torque fluctuation of the engine decreases,
A torque fluctuation reducing device for a hybrid vehicle, wherein the engine and the motor are connected. In the hybrid vehicle torque fluctuation reducing device according to claim 1,
The torque fluctuation reducing device for a hybrid vehicle, wherein the waveform of the cogging torque is set in an opposite phase to the torque waveform of the engine. In the hybrid vehicle torque fluctuation reducing device according to claim 1,
A torque fluctuation reducing device for a hybrid vehicle, characterized in that a phase is adjusted so that a peak of an antiphase is present in the cogging torque in a region where the torque increases in the combustion stroke of the engine. In the hybrid vehicle torque fluctuation reducing device according to any one of claims 1 to 3,
A connecting portion that connects the engine and the motor includes a transmission.
A gear fluctuation reduction device for a hybrid vehicle, wherein a gear ratio of the transmission is set based on a combustion cycle period of the engine / a period of the cogging torque.

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