JP5394187B2 - vehicle - Google Patents

Description

  The present invention relates to a vehicle that drives a driven part by an electric motor.

  In a vehicle in which a driven part is driven by an electric motor, such as a hybrid vehicle, when the rotational output of the electric motor is at a low rotational speed, abnormal noise may occur or drivability may decrease due to cogging torque or the like. is there.

  As a technique for solving such a problem caused by an electric motor, Patent Document 1 discloses an apparatus that reduces magnetic noise of an AC rotary electric motor by superimposing harmonics on a drive current.

Japanese Patent No. 4269881

  However, in the device described in Patent Document 1, when the harmonics are simply superimposed on the drive current, the efficiency of the motor may be reduced. Specifically, the loss due to the electric motor at the time of driving current input includes copper loss and iron loss, but the iron loss has a characteristic that it increases in proportion to the square of the frequency of the AC component of the driving current. For this reason, if the state in which the harmonics are superimposed on the drive current of the AC motor continues for a long time, the iron loss may increase and the efficiency of the motor may decrease.

  In addition, in a vehicle in which driving wheels are driven by a motor via a foot shaft, when the motor and the foot shaft are connected without a clutch, if the rotational speed of the motor is low, torque fluctuation becomes relatively large. , Drivability may be reduced.

  In addition, since the motor rotates at a relatively high speed at a relatively low speed, the influence of the cogging torque is small and drivability does not deteriorate even if a harmonic is not superimposed on the drive current. Therefore, if the above-described harmonic superposition is simply performed not only at the low speed stage but also at all the speed stages among a plurality of speed stages having different speed ratios, the efficiency of the electric motor decreases.

  The present invention has been made in view of such a background, and a vehicle capable of preventing a decrease in drivability due to cogging torque or the like even when the rotational speed of a power transmission shaft of a power transmission device is lower than a predetermined rotational speed. The purpose is to provide.

  In addition, when the power transmission device includes a plurality of shift stages having different gear ratios, a vehicle capable of controlling harmonic superimposition on the drive current of the motor with high accuracy according to the shift stage without reducing the efficiency of the motor. The purpose is to provide.

The vehicle of the present invention includes an electric motor capable of transmitting power to a driven part via a power transmission shaft of the power transmission apparatus, a power storage device that stores electric power, and a control unit that controls a driving current input to the electric motor. The power transmission device includes a plurality of gear speeds having different gear ratios, and the vehicle includes a gear speed detection unit that detects the gear speed selected by the power transmission device. The control unit includes: a rotation speed detection unit that detects a rotation speed of a power transmission shaft of the power transmission device; and a rotation speed detected by the rotation speed detection unit when the rotation speed is lower than a predetermined rotation speed. There line control so as to overlap the harmonic drive current to be input to, wherein when shift speed is below a predetermined speed change stage, intends row control to suppress harmonics superimposed to the driving current And a harmonic superposition processing unit. .

  According to the present invention, the rotational speed detector detects the rotational speed of the power transmission shaft of the power transmission device. Detecting this rotational speed may be, for example, detecting the rotational speed of the power transmission shaft by a rotational speed detection device, or estimating the rotational speed based on parameters relating to the operation of the power transmission device and the electric motor. It may be. The harmonic superimposition processing unit performs control so as to superimpose harmonics on the drive current of the electric motor when the rotation speed detected by the rotation speed detection unit is lower than the predetermined rotation speed. This predetermined rotational speed is set, for example, to a lower limit value of the rotational speed of the power transmission shaft so that the cogging torque of the electric motor is relatively small and the drivability does not deteriorate when no harmonics are superimposed on the drive current.

  That is, the harmonic superimposition processing unit determines whether or not to perform harmonic superimposition of the drive current to the electric motor based on the rotational speed of the power transmission shaft of the power transmission device, and the rotational speed of the power transmission shaft is predetermined rotation. Since harmonics are superimposed on the drive current when the speed is lower than the speed, the timing of harmonics can be controlled with high precision, and drivability can be prevented from being lowered.

Further, example embodiment, when the gear position of the relatively large gear ratio is selected, since the motor is driven at a relatively high rotational speeds, less affected by cogging torque, drivability is not reduced. For this reason, it is preferable to set a gear having a relatively large gear ratio so that the influence by the cogging torque is small and drivability does not deteriorate as the predetermined gear.

  In other words, the harmonic superimposition processing unit performs control so as to suppress the superimposition of harmonics on the drive current when the gear stage is equal to or lower than the predetermined gear stage. It is possible to prevent an increase in the iron loss of the motor and prevent a reduction in the efficiency of the electric motor.

  The harmonic superimposition processing unit may suppress superimposition of harmonics when the rotational speed of the power transmission shaft of the power transmission device is equal to or higher than a predetermined rotational speed.

  That is, when the rotational speed of the power transmission shaft is equal to or higher than the predetermined rotational speed, the superposition of harmonics is suppressed, so that the drivability is prevented from being lowered and the iron loss of the motor is prevented from being increased. Can be prevented.

  In addition, the vehicle includes a driving force setting unit that sets a driving force request to the driven unit, and the harmonic superimposing processing unit superimposes the harmonic when the set driving force is larger than a specified value. Control may be performed so as to suppress the above.

  That is, according to the above harmonic superimposition processing unit, even when the gear position for superimposing the harmonics is selected, if the driving force requirement is large and exceeds the specified value, the rotation speed of the motor is increased. Therefore, it is determined that there is no problem in drivability, and superposition of harmonics on the drive current is suppressed. By doing so, it is possible to prevent the drivability from being lowered and the iron loss of the motor to be reduced, thereby preventing the efficiency of the motor from being lowered.

1 is an overall configuration diagram of a hybrid vehicle according to a first embodiment of the present invention. The functional block diagram of ECU of the hybrid vehicle of 1st Embodiment of this invention. The flowchart for demonstrating operation | movement of the hybrid vehicle of 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the hybrid vehicle of 1st Embodiment of this invention, (a) shows the phase current before a harmonic superimposition and a harmonic superimposition, (b) is before a harmonic superimposition, and a harmonic. The torque waveform after wave superposition is shown. The whole block diagram of the hybrid vehicle of 2nd Embodiment of this invention.

[First Embodiment]
A hybrid vehicle according to a first embodiment of the present invention will be described with reference to the drawings. First, the structure of the hybrid vehicle of this embodiment is demonstrated, referring FIG.

  As shown in FIG. 1, the hybrid vehicle of this embodiment includes a power transmission device 1, and includes an engine 2 as a power generation source and an electric motor (motor / generator) 3 that can start the engine 2. The engine 2 corresponds to the internal combustion engine in the present invention.

  The power transmission device 1 is configured to be able to drive the driving wheels 4 by transmitting the power (driving force) of the engine 2 and / or the electric motor 3 to the driving wheels 4 as driven parts. The power transmission device 1 is configured to transmit power from the engine 2 and power from the drive wheels 4 to the electric motor 3 so that the electric motor 3 can perform a regenerative operation. Further, the power transmission device 1 is configured to be able to drive the auxiliary machine 5 mounted on the vehicle with the power of the engine 2 and / or the electric motor 3. The auxiliary machine 5 is, for example, an air conditioner compressor, a water pump, an oil pump, or the like.

  The engine 2 is an internal combustion engine that generates power (torque) by burning fuel such as gasoline, light oil, and alcohol. The engine 2 has a driving force input shaft 2 a for inputting generated power to the power transmission device 1. The engine 2 controls the power of the engine 2 by controlling the opening degree of a throttle valve (not shown) provided in an intake passage (not shown) in the same manner as a normal automobile engine. The

  In the present embodiment, the electric motor 3 is a three-phase DC brushless motor. The electric motor 3 includes a hollow rotor (rotary body) 3a that is rotatably supported in a housing, and a stator (stator) 3b. The rotor 3a of the present embodiment is provided with a plurality of permanent magnets. A stator (armature winding) 3ba for three phases is mounted on the stator 3b. The stator 3b is fixed to a housing provided in a stationary part that is stationary with respect to the vehicle body, such as an outer case of the power transmission device 1.

  The coil 3ba is electrically connected to a battery (power storage device, secondary battery) 7 serving as a DC power source via a power drive unit (hereinafter referred to as “PDU”) 6 which is a drive circuit including an inverter circuit. The PDU 6 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 8.

  When the PDU 6 receives a control signal (gate signal) that is a switching command from the ECU 8, the PDU 6 turns on (conducting state) / OFF (non-conducting) a transistor (switching element) paired for each phase of the inverter based on the control signal. By switching the conduction state), the DC power supplied from the battery 7 is converted into three-phase AC power. In addition, the PDU 6 converts the three-phase AC power into DC power by switching the transistor ON / OFF.

  ECU8 is electrically connected to each component of vehicles, such as power transmission device 1, engine 2, and electric motor 3, other than PDU6. The ECU 8 of this embodiment is an electronic circuit unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an interface circuit, and the like, and executes a control process defined by a program. Thus, the power transmission device 1, the engine 2, the electric motor 3, and the like are controlled.

  As shown in FIG. 2, the ECU 8 includes a rotation speed detection unit 8a and a harmonic superimposition processing unit 8b as means for realizing the functions in the present invention. The ECU 8 and the PDU 6 correspond to a control unit in the present invention. The function of this ECU 8 will be described later.

  Further, functions realized by the control process of the ECU 8 include a function of controlling the operation of the engine 2 through an actuator for engine control such as an actuator for a throttle valve (not shown), and operations of various clutches and sleeves of various synchronizers described later. Receiving a signal from the driving force setting unit 9 for setting the driving force required for the driving wheel 4 from the function of controlling the actuator via a not-shown actuator or driving circuit, the vehicle speed, the rotational speed (rotational speed) of the engine 2, and the like, The function etc. which control each component according to the request | requirement driving force and driving | running | working state are controlled.

  Further, the ECU 8 controls the current (torque) output from the rotor 3a by the motor 3 by controlling the current flowing through the coil 3ba via the PDU 6. In this case, by controlling the PDU 6, the electric motor 3 performs a power running operation for generating a power running torque in the rotor 3 a with the electric power supplied from the battery 7 and functions as a motor. That is, the electric power supplied to the stator 3b is converted into power by the rotor 3a and output. Further, by controlling the PDU 6, the electric motor 3 performs a regenerative operation for generating regenerative torque in the rotor 3 a while generating electricity by the rotational energy given to the rotor 3 a and charging the battery 7. That is, the electric motor 3 also functions as a generator. That is, the power input to the rotor 3a is converted into electric power by the stator 3b.

  The driving force setting unit 9 can set the driving force required for the driving wheels 4 based on, for example, the driver's operation and the running state. As the driving force setting unit 9, for example, an accelerator sensor that detects the amount of depression of an accelerator pedal provided in the accelerator pedal, a throttle opening sensor that detects a throttle opening, and the like can be employed.

  The various sensors 10 include, for example, a vehicle speed sensor, an acceleration sensor, an engine rotation speed sensor, a shift speed detection sensor, and the like, and send signals indicating detection results by the sensors to the ECU 8.

  The rotation speed detector 11 detects the rotation speed of the power transmission shaft of the power transmission device 1 and sends the detection result to the ECU 8.

  The gear stage detection unit 12 detects the gear stage selected by the power transmission device 1 and sends the detection result to the ECU 8. When CVT (continuously variable transmission) is adopted as the power transmission device 1, the currently selected gear ratio may be detected and the detection result may be sent to the ECU 8.

  Next, each component of the power transmission device 1 of the present embodiment will be described. The power transmission device 1 includes a power combining mechanism 13 that combines the power of the engine 2 and the power of the electric motor 3. As the power combining mechanism 13, a planetary gear device is employed in this embodiment. The power combining mechanism 13 will be described later.

  A first main input shaft 14 is connected to the driving force input shaft 2 a of the engine 2. The first main input shaft 14 is disposed in parallel with the driving force input shaft 2a, and power from the engine 2 is input via the first clutch C1. The first main input shaft 14 extends from the engine 2 side to the electric motor 3 side. The first main input shaft 14 is configured to be connected to and disconnected from the driving force input shaft 2a of the engine 2 by the first clutch C1. Further, the first main input shaft 14 of the present embodiment is connected to the rotor 3 a of the electric motor 3.

  The first clutch C <b> 1 is configured to be able to connect and disconnect the driving force input shaft 2 a and the first main input shaft 14 under the control of the ECU 8. When the driving force input shaft 2a and the first main input shaft 14 are connected by the first clutch C1, power can be transmitted between the driving force input shaft 2a and the first main input shaft 14. Further, when the connection between the driving force input shaft 2a and the first main input shaft 14 is disconnected by the first clutch C1, the power transmission is interrupted between the driving force input shaft 2a and the first main input shaft 14. .

  A first sub input shaft 15 is coaxially arranged with respect to the first main input shaft 14. The power from the engine 2 is input to the first auxiliary input shaft 15 via the second clutch C2. The second clutch C <b> 2 is configured to be able to connect and disconnect between the driving force input shaft 2 a and the first sub input shaft 15 under the control of the ECU 8. When the driving force input shaft 2a and the first auxiliary input shaft 15 are connected by the second clutch C2, power transmission between the driving force input shaft 2a and the first auxiliary input shaft 15 becomes possible. Further, when the connection between the driving force input shaft 2a and the first auxiliary input shaft 15 is disconnected by the second clutch C2, power transmission is interrupted between the driving force input shaft 2a and the first auxiliary input shaft 15. . The first clutch C1 and the second clutch C2 are arranged adjacent to each other in the axial direction of the first main input shaft 14. The first clutch C1 and the second clutch C2 of the present embodiment are constituted by wet multi-plate clutches.

  As described above, in the power transmission device 1, the first clutch C1 transmits the rotation of the driving force input shaft 2a to the first main input shaft 14 (first driving gear shaft) in a releasable manner, and the second clutch C1 The rotation of the driving force input shaft 2a is releasably transmitted to the second main input shaft 22 (second driving gear shaft).

  A reverse shaft 16 is disposed in parallel to the first main input shaft 14. A reverse gear 17 is rotatably supported on the reverse shaft 16. The first main input shaft 14 and the reverse gear 17 are always coupled via a gear train 18. The gear train 18 is configured by meshing a gear 14 a fixed on the first main input shaft 14 and a gear 17 a provided on the reverse gear 17.

  The reverse shaft 16 is provided with a reverse gear 17c fixed on the reverse gear shaft 17 and a reverse synchronizer SR capable of switching connection and disconnection with the reverse shaft 16.

  An intermediate shaft 19 is arranged with respect to the reverse shaft 16 and in parallel with the first main input shaft 14. The intermediate shaft 19 and the reverse shaft 16 are always connected via a gear train 20. The gear train 20 is configured by meshing a gear 19 a fixed on the intermediate shaft 19 and a gear 16 a fixed on the reverse shaft 16. The intermediate shaft 19 and the first auxiliary input shaft 15 are always connected via a gear train 21. The gear train 21 is configured by meshing a gear 19 a fixed on the intermediate shaft 19 and a gear 15 a fixed on the first auxiliary input shaft 15.

  A second main input shaft 22 is arranged parallel to the first main input shaft 14 with respect to the intermediate shaft 19. The second main input shaft 22 and the intermediate shaft 19 are always connected via a gear train 23. The gear train 23 is configured by meshing a gear 19a fixed on the intermediate shaft 19 and a gear 22a fixed on the third main input shaft.

  The first main input shaft 14 has gears of odd-numbered or even-numbered gears (odd-numbered third and fifth gears in this embodiment) among the plurality of gears having different gear ratios. The row drive gears are rotatably supported and connected to the motor 3.

  Specifically, the second sub input shaft 24 is coaxially disposed with respect to the first main input shaft 14. The second sub input shaft 24 is disposed closer to the electric motor 3 than the first sub input shaft 15. The first main input shaft 14 and the second auxiliary input shaft 24 are connected via a first synchronous meshing mechanism S1 (in this embodiment, a synchromesh mechanism). The first synchronous meshing mechanism S1 is provided on the first main input shaft 14, and selectively connects the third speed gear 24a and the fifth speed gear 24b to the first main input shaft 14. Specifically, the first synchronous meshing mechanism S1 is a well-known one such as a synchro clutch, and by moving the sleeve S1a along the axial direction of the second sub input shaft 24 by an actuator and a shift fork (not shown), The third speed gear 24 a and the fifth speed gear 24 b are selectively connected to the first main input shaft 14. Specifically, when the sleeve S1a moves from the illustrated neutral position to the third speed gear 24a side, the third speed gear 24a and the first main input shaft 14 are connected. On the other hand, when the sleeve S1a moves from the illustrated neutral position to the fifth speed gear 24b side, the fifth speed gear 24b and the first main input shaft 14 are connected.

  The second main input shaft 22 has gears of even-numbered or odd-numbered gears (even-numbered 2nd gear and 4th gear in this embodiment) among a plurality of gears having different gear ratios. The drive gear of the row is supported rotatably. A third auxiliary input shaft 25 is coaxially arranged with respect to the second main input shaft 22. The second main input shaft 22 and the third sub input shaft 25 are connected via a second synchronous meshing mechanism S2 (in this embodiment, a synchromesh mechanism). The second synchromesh mechanism S2 is provided on the second main input shaft 22, and is configured to selectively connect the second speed gear 25a and the fourth speed gear 25b to the second main input shaft 22. The second synchromesh mechanism S2 is a well-known one such as a synchro clutch, and the second-speed gears 25a and 4 are moved by moving the sleeve S2a in the axial direction of the third auxiliary input shaft 25 by an actuator and shift fork (not shown). The speed gear 25 b is selectively connected to the second main input shaft 22. When the sleeve S2a moves from the illustrated neutral position to the second speed gear 25a side, the second speed gear 25a and the second main input shaft 22 are connected. On the other hand, when the sleeve S2a moves from the illustrated neutral position to the fourth speed gear 25b side, the fourth speed gear 25b and the second main input shaft 22 are connected.

  The third sub input shaft 25 and the output shaft 26 are coupled via a second speed gear train 27. The second gear train 27 is configured by meshing a gear 25 a fixed on the third sub input shaft 25 and a gear 26 a fixed on the output shaft 26. Further, the third sub input shaft 25 and the output shaft 26 are coupled via a fourth speed gear train 28. The fourth speed gear train 28 is configured by meshing a gear 25 b fixed on the third sub input shaft 25 and a gear 26 b fixed on the output shaft 26.

  The output shaft 26 and the second auxiliary input shaft 24 are coupled via a third speed gear train 29. The third speed gear train 29 is configured by meshing a gear 26 a fixed to the output shaft 26 and a gear 24 fixed on the second auxiliary input shaft 24. The output shaft 26 and the second auxiliary input shaft 24 are coupled via a fifth speed gear train 30. The fifth speed gear train 30 is configured by meshing a gear 26b fixed to the output shaft 26 and a gear 24b fixed on the second sub input shaft 24. The gears 26a and 26b of each gear train fixed to the output shaft 26 are referred to as driven gears.

  A final gear 26 c is fixed to the output shaft 26. The rotation of the output shaft 26 is configured to be transmitted to the drive wheels 4 via the final gear 26c, the differential gear unit 31 and the axle 32.

  The power combining mechanism 13 of this embodiment is provided inside the electric motor 3. Part or all of the rotor 3a, the stator 3b, and the coil 3ba constituting the electric motor 3 are arranged so as to overlap the power combining mechanism 13 along a direction orthogonal to the axial direction of the first main input shaft 14. .

  The power combining mechanism 13 includes a differential device that can differentially rotate the first rotating element, the second rotating element, and the third rotating element. In the present embodiment, the differential device that constitutes the power combining mechanism 13 is a single pinion type planetary gear device, and includes three rotation elements: a sun gear 13s (first rotation element) and a ring gear 13r (second rotation element). And a carrier (third rotating element) 13c that rotatably supports a plurality of planetary gears 13p engaged with the sun gear 13s and the ring gear 13r between the sun gear 13s and the ring gear 13r. These three rotating elements 13s, 13r, and 13c can transmit power between each other, and rotate while maintaining a constant collinear relationship between the respective rotational speeds (rotational speeds).

  The sun gear 13 s is fixed to the first main input shaft 14 so as to rotate in conjunction with the first main input shaft 14. The sun gear 13s is fixed to the rotor 3a so as to rotate in conjunction with the rotor 3a of the electric motor 3. Thereby, the sun gear 13s, the first main input shaft 14, and the rotor 3a rotate in conjunction with each other.

  The ring gear 13r is configured to be switchable between a fixed state and a non-fixed state with respect to the housing 33, which is a non-moving portion, by the third synchronous meshing mechanism SL. Specifically, by moving the sleeve SLa of the third synchronous meshing mechanism SL along the rotation axis direction of the ring gear 13r, the first speed gear 33a provided in the housing 33 and the gear 13a fixed to the ring gear 13r are fixed. It is configured to be able to switch between the state and the non-fixed state.

  The carrier 13 c is connected to one end of the second sub input shaft 24 on the electric motor 3 side so as to rotate in conjunction with the second sub input shaft 24.

  The input shaft 5 a of the auxiliary machine 5 is arranged in parallel to the reverse shaft 16. The reverse shaft 16 and the input shaft 5a of the auxiliary machine 5 are coupled via, for example, a belt mechanism 34. The belt mechanism 34 is configured by connecting a gear 17b fixed on the reverse gear shaft 17 and a gear 5b fixed on the input shaft 5a via a belt. An auxiliary machine clutch 35 is interposed on the input shaft 5 a of the auxiliary machine 5. The gear 5b and the input shaft 5a of the auxiliary machine 5 are connected coaxially through an auxiliary machine clutch 35.

  The auxiliary device clutch 35 is a clutch that operates so as to connect or disconnect between the gear 5 b and the input shaft 5 a of the auxiliary device 5 under the control of the ECU 8. In this case, when the auxiliary machine clutch 35 is operated in the connected state, the gear 5b and the input shaft 5a of the auxiliary machine 5 are coupled via the auxiliary machine clutch 35 so as to rotate integrally with each other. Further, when the auxiliary machine clutch 35 is operated in the disconnected state, the coupling between the gear 5b and the input shaft 5a of the auxiliary machine 5 by the auxiliary machine clutch 35 is released. In this state, power transmission to the first auxiliary input shaft 15 and the input shaft 5a of the auxiliary machine 5 is interrupted.

  Next, each gear stage will be described. As described above, the power transmission device 1 of the present embodiment shifts the rotational speed of the input shaft to a plurality of stages via the gear trains of a plurality of shift stages having different speed ratios, and outputs it to the output shaft 26. It is configured. Further, in the power transmission device 1, it is defined that the gear ratio is smaller as the gear position is larger.

  When the engine is started, the first clutch C1 is connected, the electric motor 3 is driven, and the engine 2 is started. That is, the electric motor 3 also has a function as a starter.

  The first gear is established by bringing the ring gear 13r and the housing 33 into a connected state (fixed state) by the third synchronous meshing mechanism SL. When traveling by the engine 2, the second clutch C <b> 2 is disengaged (hereinafter referred to as OFF state) and the first clutch C <b> 1 is engaged (hereinafter referred to as ON state). The driving force output from the engine 2 is transmitted to the drive wheels 4 through the sun gear 13s, the carrier 13c, the gear train 29, the output shaft 26, and the like.

  In addition, when the engine 2 is driven and the electric motor 3 is driven, the assist traveling by the electric motor 3 at the first gear (the traveling in which the driving force of the engine 2 is assisted by the electric motor 3) can be performed. Furthermore, if the first clutch C1 is in the OFF state, EV traveling that travels only by the electric motor 3 can be performed.

  Further, during the deceleration regenerative operation, the electric motor 3 is braked so that the vehicle is decelerated to generate electric power with the electric motor 3 and the battery 7 can be charged via the PDU 6.

  In the second gear, the ring gear 13r and the housing 33 are unfixed by the third synchronous mesh mechanism SL, and the second synchronous mesh mechanism S2 is connected to the second main input shaft 22 and the second gear 25a. It is established by that. When traveling by the engine 2, the second clutch C2 is turned on. In the second speed, the driving force output from the engine 2 is transmitted via the first main input shaft 14, the gear train 21, the intermediate shaft 19, the gear train 23, the second main input shaft 22, the output shaft 26, and the like. It is transmitted to the drive wheel 4.

  If the first clutch C1 is turned on, the first clutch C1 is turned on, the engine 2 is driven and the electric motor 3 is driven, the assist travel by the electric motor 3 at the second speed stage can also be performed. Furthermore, in this state, driving by the engine 2 can be stopped and EV traveling can be performed. When stopping the driving by the engine 2, for example, the engine 2 may be in a fuel cut state or a cylinder resting state. Further, the decelerating regenerative operation can be performed at the second speed stage.

  When the first clutch C1 is in the OFF state and the second clutch C2 is in the ON state, and the ECU 8 is traveling at the second speed by driving the engine 2, the ECU 8 is expected to upshift to the third speed depending on the traveling state of the vehicle. If the determination is made, the first synchronous meshing mechanism S1 sets the first main input shaft 14 and the third speed gear 24a in a connected state or a pre-shifted state approaching this state. As a result, the upshift from the second gear to the third gear can be performed smoothly.

  The third speed is established by bringing the first synchronous meshing mechanism S1 into a state where the first main input shaft 14 and the third speed gear 24a are connected. When traveling by the engine 2, the first clutch C1 is turned on. At the third speed, the driving force output from the engine 2 is transmitted to the drive wheels 4 via the first main input shaft 14, the third speed gear train 29, the output shaft 26, and the like.

  In addition, if the 1st clutch C1 is made into an ON state, the engine 2 is driven, and the electric motor 3 is driven, the assist driving | running | working by the electric motor 3 in 3rd speed can also be performed. Furthermore, the EV clutch can be performed with the first clutch C1 in the OFF state. Note that during EV traveling, the first clutch C1 can be turned on to stop driving by the engine 2, and EV traveling can be performed. Further, the decelerating regenerative operation can be performed at the third speed stage.

  During traveling at the third gear, the ECU 8 predicts whether the next gear to be shifted is the second gear or the fourth gear based on the traveling state of the vehicle. When the ECU 8 predicts a downshift to the second speed, the second synchronous meshing mechanism S2 is connected to the second speed gear 25a and the second main input shaft 22, or is in a preshift state in which this state is approached. And When the ECU 8 predicts an upshift to the fourth speed stage, the second synchronous meshing mechanism S2 is connected to the fourth speed gear 25b and the second main input shaft 22 or is in a preshift state in which this state is approached. And Thereby, the upshift and the downshift from the third gear can be performed smoothly.

  The fourth speed is established by bringing the second synchronous meshing mechanism S2 into a state where the second main input shaft 22 and the fourth speed gear 25b are connected. When traveling by the engine 2, the second clutch C2 is turned on. In the fourth speed, the driving force output from the engine 2 is transmitted via the first main input shaft 14, the gear train 21, the intermediate shaft 19, the gear train 23, the second main input shaft 22, the output shaft 26, and the like. It is transmitted to the drive wheel 4.

  If the second clutch C2 is turned on, the first clutch C1 is turned on, the engine 2 is driven, and the electric motor 3 is driven, the assist traveling by the electric motor 3 at the fourth speed can be performed. Furthermore, in this state, driving by the engine 2 can be stopped and EV traveling can be performed.

  The second clutch C2 is turned off, the first clutch C1 is turned on, and the ECU 8 is driven at the fourth speed by driving the engine 2, and the ECU 8 is next shifted based on the running state of the vehicle. Predict whether it is 3rd gear or 5th gear. When the ECU 8 anticipates a downshift to the third speed, the first synchronous meshing mechanism S1 connects the first main input shaft 14 and the third speed gear 24a, or a preshift approaching this state. State. When the ECU 8 expects an upshift to the fifth speed, the first synchronous mesh mechanism S1 connects the first main input shaft 14 and the fifth speed gear 24b, or a preshift approaching this state. State. Thereby, the upshift and the downshift from the fourth gear can be performed smoothly.

  The fifth speed is established by bringing the first synchronous meshing mechanism S1 into a state where the first main input shaft 14 and the fifth speed gear 24b are connected. When traveling by the engine 2, the first clutch C1 is turned on. At the fifth speed, the driving force output from the engine 2 is transmitted to the drive wheels 4 via the first main input shaft 14, the third gear train 29, the output shaft 26, and the like.

  In addition, if the 1st clutch C1 is made into an ON state, the engine 2 is driven, and the electric motor 3 is driven, the assist driving | running | working by the electric motor 3 in 5th speed can also be performed. Furthermore, the second clutch C2 can be turned off, the first clutch C1 can be turned on, and EV travel can be performed. Note that during EV traveling, the first clutch C1 can be turned on to stop driving by the engine 2, and EV traveling can be performed. Further, the decelerating regenerative operation can be performed at the fifth gear.

  When the ECU 8 determines that the next gear to be shifted is the fourth gear based on the traveling state of the vehicle while traveling at the fifth gear, the ECU 8 sets the second synchromesh mechanism S2 to 4 A state in which the speed gear 25b and the second main input shaft 22 are connected to each other, or a pre-shift state close to this state is set. Thereby, the downshift from the fifth gear to the fourth gear can be performed smoothly.

  In the reverse gear, the reverse synchronous meshing mechanism SR is connected to the reverse shaft 16 and the reverse gear 17c, and the second synchronous meshing mechanism S2 is connected to, for example, the second main input shaft 22 and the second speed gear 25a. Established by entering a state. When traveling by the engine 2, the first clutch C1 is turned on. In this reverse speed, the driving force output from the engine 2 is the first main input shaft 14, the gear train 18, the reverse gear 17c, the reverse shaft 16, the gear train 20, the intermediate shaft 19, the gear train 23, the second main input. It is transmitted to the drive wheel 4 via the shaft 22, the third auxiliary input shaft 25, the gear train 27, the output shaft 26, and the like. In addition, if the engine 2 is driven and the electric motor 3 is driven, assist traveling by the electric motor 3 in the reverse speed can be performed. Furthermore, EV traveling can also be performed by setting the first clutch C1 to the OFF state. Deceleration regenerative operation can be performed in the reverse gear.

  Next, functions of the ECU 8 of this embodiment shown in FIG. 2 will be described.

  The rotational speed detector 8 a detects the rotational speed of the power transmission shaft of the power transmission device 1. In the present embodiment, the power transmission shaft corresponds to the output shaft 26 of the power transmission device 1. The power transmission shaft may be any of the first main input shaft 14, the first sub input shaft 24, and the output shaft 26.

  In the present embodiment, the rotation speed detection unit 8a detects the rotation speed of the power transmission shaft based on the rotation speed of the power transmission shaft of the power transmission device 1 detected by the rotation speed detection unit 11. In the present embodiment, the rotational speed detector 11 detects the rotational speed of the output shaft 26 as a power transmission shaft. Further, the rotation speed detection unit 11 may detect the rotation speed of any of the first main input shaft 14, the first sub input shaft 24, and the output shaft 26.

  Further, the rotational speed detection unit 8a estimates the rotational speed of the power transmission shaft of the power transmission device 1 based on the driving force request from the driving force setting unit 9, the traveling state (traveling mode), and the like, so that the power transmission is performed. The rotational speed of the shaft may be detected. Specifically, for example, a map that associates the rotational speed of the power transmission shaft with the driving force request and the traveling state (traveling mode) is stored in advance in the storage unit, and the rotational speed detection unit 8a uses the map to drive Based on the force request and the running state (running mode), the rotational speed of the power transmission shaft of the power transmission device 1 is calculated. Thus, by estimating the rotational speed of the power transmission shaft of the power transmission device 1, the rotational speed of the power transmission shaft can be obtained relatively easily without providing the rotational speed detector 11.

  The harmonic superimposition processing unit 8b performs control so that harmonics are superimposed on the drive current input to the electric motor 3 when the rotation speed detected by the rotation speed detection unit 8a is lower than a predetermined rotation speed. As the harmonics, those having a frequency component that is n times the fundamental frequency component can be employed (n is an integer of 2 or more). In addition, as the harmonic, the second harmonic, the third harmonic, the fourth harmonic, the fifth harmonic, the sixth harmonic,..., The nth harmonic, etc., or two or more harmonics thereof It is preferable to employ a synthesized wave. As this harmonic, for example, the amplitude, phase, etc. of each higher-order harmonic may be appropriately set according to the gear position of the power transmission device 1.

  In addition, the predetermined rotational speed is set to a lower limit value of the rotational speed of the power transmission shaft so that the cogging torque of the electric motor is relatively small and drivability is not lowered when no harmonic is superimposed on the driving current, for example. It is preferable. In this way, based on the rotational speed of the power transmission shaft of the power transmission device, it is determined whether or not to superimpose the harmonics of the drive current to the motor 3, and the timing for superimposing the harmonics on the drive current is increased. The accuracy can be controlled, and the drivability can be prevented from decreasing.

  Further, the harmonic superimposition processing unit 8b performs control so as to suppress the superposition of harmonics when the rotational speed of the power transmission shaft of the power transmission device 1 is equal to or higher than a predetermined rotational speed. By carrying out like this, the increase in the iron loss of the electric motor 3 can be prevented and the fall of the efficiency of an electric motor can be prevented.

  In addition, the harmonic superimposition processing unit 8b performs control so as to suppress the superposition of harmonics when the driving force request set by the driving force setting unit 9 is larger than a specified value. In this way, for example, even when a gear position that superimposes harmonics is selected, it is determined that it is not necessary to superimpose harmonics on the drive current when the driving force requirement is a specified value or more. Thus, the superposition of harmonics is suppressed. That is, it is possible to reduce the iron loss of the electric motor 3 to prevent the efficiency of the electric motor 3 from being lowered and to prevent the drivability from being lowered.

  Further, the harmonic superimposition processing unit 8b performs control so as to suppress the superimposition of harmonics on the drive current when the gear position is equal to or lower than a predetermined gear position (first speed in this embodiment). For example, when a gear stage having a relatively large gear ratio is selected, the electric motor 3 is driven at a relatively high rotational speed, so that the influence of the cogging torque is small and drivability does not deteriorate. For this reason, it is preferable to set a gear stage having a relatively large gear ratio so that the influence of the cogging torque is small and drivability does not deteriorate as the predetermined gear stage. Specifically, at the first speed, the electric motor 3 is driven at a relatively high rotation frequency. Further, in the second speed to the fifth speed, the frequency at which the electric motor 3 is driven in a relatively low rotational speed range is high. For this reason, in the present embodiment, the above-described harmonic superposition is not performed at the first speed stage, and the above-described harmonic superposition is performed at the second speed stage or higher where the gear ratio is smaller than the first speed stage, for example, the second speed stage to the fifth speed stage. Control. In other words, since the harmonic superimposition on the drive current is controlled according to the gear position, the timing of the harmonic superposition can be controlled with high accuracy relatively easily.

  Next, the operation of the hybrid vehicle of this embodiment will be described with reference to FIG.

  In step ST1, for example, the ECU 8 determines whether or not the rotational speed of the power transmission shaft of the power transmission device 1 detected by the rotational speed detector 8a is smaller than a predetermined rotational speed (for example, 100 rpm). As a result of the determination, if the rotation speed of the power transmission shaft is smaller than the specified rotation speed, the process proceeds to step ST3. If the rotation speed of the power transmission shaft is equal to or higher than the specified rotation speed, the process proceeds to step ST2.

  In step ST <b> 2, the ECU 8 does not perform control for superimposing harmonics on the drive current input to the electric motor 3 (suppressing harmonics superimposition). Specifically, when the ECU 8 sends a control signal instructing to suppress harmonic superposition to the drive current to the PDU 6, the PDU 6 suppresses the above harmonic superposition.

  In step ST3, the ECU 8 determines whether or not the gear position needs to be subjected to the harmonic superposition based on the gear position detected by the gear position detection unit 12. Specifically, the ECU 8 determines whether or not the detected shift speed is equal to or lower than a predetermined shift speed (for example, the first speed). When the ECU 8 determines that it is necessary to perform the above harmonic superimposition (below a predetermined gear position), the process proceeds to step ST4, and otherwise, the process proceeds to step ST2.

  In step ST4, the ECU 8 determines whether or not a value (for example, accelerator opening (AP)) indicated by the driving force request is larger than a specified value based on the driving force request set by the driving force setting unit 9. to decide. When the value indicated by the driving force request is larger than the specified value, the ECU 8 proceeds to the process of step ST2 and performs control so as to suppress harmonic superposition on the driving current. If the value indicated by the driving force request is equal to or less than the specified value, the process proceeds to step ST5.

  In step ST5, the ECU 8 performs control so that harmonics are superimposed on the drive current. Specifically, when the ECU 8 sends a control signal instructing to superimpose harmonics to the drive current to the PDU 6, the PDU 6 superimposes harmonics to the drive current.

  In the present embodiment, when the motor 3 is at a low rotation speed, that is, when the power transmission shaft is at a low rotation speed, harmonics are superimposed on the phase current input to the motor 3 as shown in FIG. When there is no phase current, the phase current is a sine wave, and as shown in FIG. 4B, the fluctuation range of the torque waveform of the electric motor 3 is relatively large due to the cogging torque.

  On the other hand, when harmonics are superimposed on the phase current input to the electric motor 3, the width of fluctuation of the torque waveform of the electric motor 3 is relatively small. For this reason, the influence by the cogging torque is reduced, and a decrease in drivability can be prevented.

[Second Embodiment]
A hybrid vehicle according to a second embodiment of the present invention will be described with reference to FIG. Constituent elements similar to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted. When superimposing a harmonic on the drive current, the ECU 8 preferably includes any one of a first harmonic setting unit 8c, a second harmonic setting unit 8d, and a third harmonic setting unit 8e, for example.

  First, the case where the 1st harmonic setting part 8c is provided in ECU8 is demonstrated. In this case, the second harmonic setting unit 8d, the third harmonic setting unit 8e, and the like are not provided.

  For example, the fundamental wave target value setting unit 41 sets the amplitude and phase of the fundamental wave current command value in the three-phase AC coordinate system based on the driving force request set by the driving force setting unit 9.

  The first harmonic setting unit 8c sets a harmonic current command value that is the frequency, amplitude, and phase of a harmonic of a predetermined order with respect to a predetermined fundamental wave, under the control of the harmonic superposition processing unit 8b. The frequency, amplitude, and phase of this harmonic can be set as appropriate based on, for example, the gear position of the power transmission device 1, the rotational speed of the power transmission shaft of the power transmission device 1, and the like. The drivability is improved by superimposing optimum harmonics on the gear position of the power transmission device 1 and the rotational speed of the power transmission shaft.

  The synthesizing unit 42 adds the fundamental wave current command value by the fundamental wave target value setting unit 41 and the harmonic current command value by the first harmonic setting unit 8c for each phase to obtain a synthesized three-phase AC current command. Generate.

  The three-phase-dp conversion unit 43 performs coordinate conversion of the combined three-phase alternating current command into the dq axis coordinate system.

  The subtractor 44 calculates a difference between signals output from the three-phase-dq conversion unit 43 and the three-phase-dq conversion unit 45.

  The current control unit 46 calculates a voltage command value (dq coordinate system) based on a signal indicating the difference calculated by the subtractor 44.

  The dp-three-phase converter 47 corrects the voltage command value (dq coordinate system) by the current controller 46 based on the position (angle) of the rotor of the electric motor 3 detected by the position detector 3c, Convert to three-phase current command value. As the position detector 3c, for example, a resolver can be employed.

  A PWM (Pulse width modulation) circuit 48 generates a PWM signal (three-phase AC control signal) that is a gate signal for controlling the inverter of the PDU 6 based on the three-phase voltage command value by the dp-three-phase converter 47. To do.

  The PDU 6 is supplied from the battery 7 by switching ON (conductive state) / OFF (non-conductive state) of each pair of transistors for each phase of the PWM inverter based on the PWM signal from the PWM circuit 48. DC power is converted into three-phase AC power. By supplying three-phase AC power from the PDU 6 to each of the coils provided on the stator of the electric motor 3, the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw are supplied to the electric motor 3.

  The filter circuit 49 removes harmonic components from the phase currents Iu, Iv, Iw detected by the current detector 50. The three-phase-dq converter 45 is based on the current signals Iu, Iv, Iw sent from the filter circuit 49 and a signal indicating the position (angle) of the rotor of the electric motor 3 detected by the position detector 3c. Then, a current instruction signal (dq coordinate system) is generated and output to the subtractor 44. Details of the feedback control of the above circuit are well known and will not be described. Further, by providing the filter circuit 49, it is possible to perform feedback control with high accuracy.

  As described above, the harmonic superimposition processing unit 8b, when superimposing a harmonic on the drive current to the motor 3, causes the first harmonic setting unit 8c to perform a harmonic current command value with respect to the fundamental current command value. And the combining unit 42 combines the fundamental current command value and the harmonic current command value, so that the harmonic can be superimposed on the drive current to the motor 3 relatively easily. Further, the electric motor 3 has a relatively small torque fluctuation even at a low rotational speed due to the driving current on which the harmonics are superimposed.

  Next, a case where the ECU 8 includes the second harmonic setting unit 8d will be described. In this case, the first harmonic setting unit 8c and the synthesis unit 42 are not provided.

  The second harmonic setting unit 8 d generates a signal that superimposes the harmonic on the PWM signal as the fundamental wave by the PWM circuit 48.

  The adder 51 adds the PWM signal from the PWM circuit 48 and the signal from the second harmonic setting unit 8d to generate a PWM signal for superimposing the harmonic on the fundamental wave.

  Based on the PWM signal, the PDU 6 switches the DC power supplied from the battery 7 to 3 by switching ON (conductive state) / OFF (non-conductive state) of each transistor paired for each phase of the PWM inverter. It is converted into phase AC power and sent to the motor 3.

  As described above, since the ECU 8 includes the second harmonic setting unit 8d, it is possible to superimpose harmonics on the drive current relatively easily.

  Next, a case where the ECU 8 includes the third harmonic setting unit 8e will be described. In this case, the first harmonic setting unit 8c, the second harmonic setting unit 8d, the synthesis unit 42, and the adder 51 are not provided.

  The 3rd harmonic setting part 8e produces | generates the harmonic to be superimposed on each phase current Iu, Iv, Iw by PDU6.

  The adder 52 superimposes the harmonics generated by the third harmonic setting unit 8e on the phase currents Iu, Iv, Iw from the PDU 6 and outputs the phase currents Iu, Iv, Iw on which the harmonics are superimposed. Send to electric motor 3.

  As described above, since the ECU 8 includes the third harmonic setting unit 8e, the harmonics can be superimposed on the drive current relatively easily.

  As described above, the vehicle according to the present embodiment stores electric power with the engine 2, the electric motor 3 that can transmit power to the drive wheels 4 via the power transmission shaft (output shaft) 26 of the power transmission device 1, and the electric power. The battery 9 includes a PDU 6 and an ECU 8 that control a drive current input to the electric motor. Then, the ECU 8 detects the rotational speed of the power transmission shaft 26 of the power transmission device 1, and performs control so that harmonics are superimposed on the drive current input to the electric motor 3 when the rotational speed is lower than the predetermined rotational speed. I do. That is, the timing of harmonic superposition can be controlled with high accuracy, and the cogging torque can be reduced to prevent drivability from being lowered.

  Further, since the ECU 8 performs control so as not to superimpose harmonics on the drive current input to the motor when the rotational speed is equal to or higher than a predetermined rotational speed, the iron loss in the motor 3 can be reduced, and the efficiency in the motor 3 can be reduced. A decrease can be prevented.

  Further, the ECU 8 performs control so as to suppress harmonics from being superimposed on the drive current of the electric motor 3 when the shift speed is equal to or lower than a predetermined shift speed (for example, the first speed). In the above-described embodiment, in the power transmission device 1, the first synchronous meshing mechanism S1 is turned on so that the planetary gear mechanism has a substantially first speed function. It is set to have a large gear ratio. At this time, at the first speed, the electric motor 3 has a high rotational speed, and therefore the influence of the cogging torque is small. That is, at the first speed stage, the efficiency of the electric motor 3 can be prevented from lowering by controlling so that harmonics are not superimposed on the drive current.

  In addition, at the second speed or higher, when the power transmission shaft has a relatively small rotational speed, control is performed so that harmonics are superimposed on the drive current, thereby reducing the width of the torque fluctuation. For this reason, it is possible to prevent a decrease in drivability.

  Further, since the ECU 8 performs control so as to suppress the superposition of harmonics when the driving force request is larger than a specified value, in detail, when the accelerator opening (AP) is larger than the specified value, power transmission is performed. It is determined that the rotational speed of the shaft is relatively large, and control is performed so that harmonics are not superimposed on the drive current. When the rotational speed of the power transmission shaft is high, drivability is relatively high. Specifically, for example, even when a gear stage (for example, the third speed stage) on which harmonics are superimposed is selected in the power transmission device 1, harmonics are superimposed when the driving force requirement is equal to or greater than a threshold value. Is suppressed. That is, the iron loss of the electric motor 3 can be reduced, and the efficiency reduction of the electric motor 3 can be prevented.

  In the above-described embodiment, the power transmission device 1 includes a plurality of shift stages having different gear ratios, but is not limited to this form. For example, a CVT (continuously variable transmission) may be employed as the power transmission device 1. In this case, the gear position detection unit 12 may estimate or detect the gear ratio of the CVT. The ECU 8 determines whether or not the gear ratio of the CVT is equal to or less than a predetermined gear ratio. As a result of the determination, if it is smaller than the predetermined gear ratio, the ECU 8 performs control so that harmonics are superimposed on the drive current, and if it is greater than the predetermined gear ratio, the ECU 8 suppresses harmonics superimposed on the drive current. To control.

  By doing this, even when CVT is adopted as the power transmission device 1, it is controlled to superimpose or suppress superimposition of harmonics on the drive current according to the transmission ratio of the CVT, thereby reducing the influence of cogging torque. In addition, the drivability can be prevented from being lowered and the loss of the electric motor 3 can be reduced.

  Although the embodiment has been described above, the present invention is not limited to the above embodiment.

  The configuration of the ECU 8 is not limited to the above-described form. If the condition for superimposing the harmonics on the drive current to the electric motor 3 is satisfied, the configuration may be arbitrary as long as the control can be performed so that the harmonics are superimposed on the drive current to the electric motor 3.

  DESCRIPTION OF SYMBOLS 1 ... Power transmission device, 2 ... Engine (internal combustion engine: ENG), 2a ... Driving force input shaft (input shaft), 3 ... Electric motor, 3a ... Rotor, 3b ... Stator, 4 ... Drive wheel (driven part), 5 ... Auxiliary machine, 6 ... Power drive unit (PDU), 7 ... Battery (power storage device, secondary battery), 8 ... Electronic control unit (ECU), 8a ... Rotational speed detection unit, 8b ... Harmonic superposition processing unit, 8c ... 1st harmonic setting part, 8d ... 2nd harmonic setting part, 8e ... 3rd harmonic setting part, 9 ... Driving force setting part, 10 ... Various sensors, 11 ... Rotational speed detection part, 12 ... Shift speed detection part , 13 ... power combining mechanism (planetary gear unit), 13c ... carrier, 13p ... planetary gear, 13r ... ring gear, 13s ... sun gear, 14 ... first main input shaft (first drive gear shaft), 15 ... first auxiliary input shaft , 16 ... Reverse axis, 17 ... Reverse YA shaft, 18 ... gear train, 19 ... intermediate shaft, 20 ... gear train, 21 ... gear train, 22 ... second main input shaft (second drive gear shaft), 23 ... gear train, 24 ... second sub input shaft 25 ... 3rd auxiliary input shaft, 26 ... output shaft, 26a, 26b ... driven gear, 27 ... 2nd gear train, 28 ... 4th gear train, 29 ... 3rd gear train, 30 ... 5th gear train, 31 ... Differential gear unit, 32 ... Axle, 33 ... Housing (non-moving part), 34 ... Belt mechanism, C1 ... First clutch (connection / disconnection device), C2 ... Second clutch, S1 ... First synchronous meshing mechanism, S2 ... Second synchronous meshing mechanism, SL: third synchronous meshing mechanism, SR: reverse synchronous meshing mechanism.

Claims (3)

A vehicle comprising: an electric motor capable of transmitting power to a driven part via a power transmission shaft of the power transmission device; a power storage device that stores electric power; and a control unit that controls a drive current input to the electric motor. ,
The power transmission device includes a plurality of shift stages having different gear ratios,
The vehicle has a shift speed detection unit that detects the shift speed selected by the power transmission device,
The control unit is a rotation speed detection unit that detects a rotation speed of a power transmission shaft of the power transmission device;
Wherein when the rotation speed detection unit rotational speed detected by the is lower than a predetermined rotational speed, have row control so as to overlap the harmonic drive current to be input to the electric motor, the gear stage is a predetermined gear stage the following cases, the vehicle characterized in that it comprises a row intends harmonic superimposition processing unit controls so as to suppress the harmonics superimposed to the driving current.   2. The vehicle according to claim 1, wherein the harmonic superposition processing unit suppresses the superposition of the harmonics when the rotational speed of the power transmission shaft of the power transmission device is equal to or higher than a predetermined rotational speed. A driving force setting unit for setting a driving force request to the driven unit;
The harmonic superimposition processing unit of the vehicle according to claim 1 or claim 2 wherein the set driving force is greater than the specified value, characterized in that to suppress the superposition of the harmonic.

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