Drive system

Abstract

A drive system is provided with: a shift operation device; an acceleration operation device; a step-up device that steps up the voltage of the battery and outputs the voltage as a DC step-up voltage; a multi-level inverter which includes a switching element and is capable of outputting a pulse voltage of 3 or more levels, and which converts the boost voltage of the boost device into an AC output voltage and outputs the AC output voltage; a motor generator driven by the output voltage of the multilevel inverter; and a control device that controls the step-up device and the multilevel inverter, a processor of the control device performing a process including: a step of determining a step-up voltage of the step-up device based on a shift operation acquired by the shift operation device; a step of determining an output voltage of the multi-level inverter on the basis of the acceleration operation acquired by the acceleration operation means; and a step of determining the number of levels of the multi-level inverter on the basis of the boost voltage of the boost device and the output voltage of the multi-level inverter.

Description

Technical Field

[0001] The present invention relates to a drive system. Background Art

[0002] For example, Patent Document 1 discloses a technique for driving and controlling a motor by supplying the output voltage of a multilevel inverter to an electric generator. The multilevel inverter of Patent Document 1 involved is, for example, a three-level inverter.

[0003] Prior Art Documents Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-2430. Summary of the Invention

[0004] Technical Problem However, in an electric vehicle including an electric generator as a drive source, since driving can be performed by controlling the rotational speed of the electric generator, there is no need to provide a transmission. Therefore, the shift operation device for changing gears provided in an engine vehicle is sometimes omitted in an electric vehicle.

[0005] In an engine vehicle, the driver can intentionally change the torque of the engine by performing a shift operation. However, in an electric vehicle, if the shift operation device is omitted, the driver cannot obtain the operation feeling of the vehicle brought about by the shift operation as in an engine vehicle.

[0006] Therefore, an object of the present invention is to provide a drive system that can enable a driver to obtain the operation feeling of a vehicle brought about by a shift operation.

[0007] Technical Solution To solve the above problems, a drive system according to an embodiment of the present invention includes: a shift operation device that receives a shift operation; an acceleration operation device that receives an acceleration operation; a booster device that boosts the voltage of a battery and outputs it as a DC boosted voltage; a multilevel inverter that includes switching elements and can output a pulse voltage of 3 levels or more, and converts the boosted voltage of the booster device into an AC output voltage and outputs it; an electric generator that is driven by the output voltage of the multilevel inverter; and a control device that controls the booster device and the multilevel inverter, wherein the control device includes: one or more processors; and one or more memories connected to the processor, The processor executes a process including the following steps: A step of determining the boosted voltage of the boosting device based on a shift operation obtained through the shift operation device; A step of determining the output voltage of the multilevel inverter based on an acceleration operation obtained through the acceleration operation device; A step of determining the number of levels of the multilevel inverter based on the boosted voltage of the boosting device and the output voltage of the multilevel inverter.

[0008] Technical effects According to the present invention, a driver can obtain a feeling of operating a vehicle brought about by a shift operation. Description of the drawings

[0009] Figure 1 is a block diagram showing the configuration of a vehicle to which the drive system of the present embodiment is applied.

[0010] Figure 2 is a circuit diagram showing an example of the configuration of a multilevel inverter.

[0011] Figure 3 is a graph showing the relationship between the rotational speed and torque of an electric generator for each number of levels of the multilevel inverter.

[0012] Figure 4 shows an example of the spectrum of the sound generated when the number of levels is 2 levels.

[0013] Figure 5 shows an example of the spectrum of the sound generated when the number of levels is 3 levels.

[0014] Figure 6 shows an example of the spectrum of the sound generated when the number of levels is 5 levels.

[0015] Figure 7 is a graph explaining the relationship between the gear position of the shift operation device, the boosted voltage of the boosting device, the output voltage of the multilevel inverter, and the number of levels.

[0016] Figure 8 is a graph explaining the case where a shift-up operation for increasing the gear position is obtained through the shift operation device.

[0017] Figure 9 is a graph explaining the case where a downshift operation for decreasing the gear position is obtained through the shift operation device.

[0018] Figure 10 is a graph explaining another example in the case where a downshift operation is obtained through the shift operation device.

[0019] Figure 11 It is a flowchart showing the process of the operation of the drive control unit.

[0020] Symbol Explanation 10 Drive system 20 Electric generator 22 Battery 24 Boost device 26 Multilevel inverter 30 Shift operation device 32 Acceleration operation device 34 Control device 50 Switch element 70 Processor 72 Memory 74 Drive control unit. Detailed implementation

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in the relevant embodiments are merely examples for easy understanding of the invention, and do not limit the present invention except in the case where specifically stated. It should be noted that in this specification and the accompanying drawings, for units having substantially the same functions and structures, repeated descriptions are omitted by labeling the same symbols, and in addition, illustrations of units not directly related to the present invention are omitted.

[0022] Figure 1 It is a block diagram showing the configuration of a vehicle 1 to which the drive system 10 of this embodiment is applied. The vehicle 1 is an electric vehicle or a hybrid electric vehicle including an electric generator 20 as a drive source. The drive system 10 is applied to the vehicle 1 to control the drive of the vehicle 1.

[0023] In addition to the electric generator 20, the drive system 10 further includes a battery 22, a boost device 24, a multilevel inverter 26, wheels 28, a shift operation device 30, an acceleration operation device 32, and a control device 34.

[0024] The battery 22 is a secondary battery capable of charging and discharging. The battery 22 is, for example, a lithium-ion battery, etc., but is not limited to this example, and may be any secondary battery.

[0025] The boost device 24 is, for example, a DC-DC converter. The boost device 24 is electrically connected to the battery 22. The boost device 24 boosts the DC voltage of the battery 22 and outputs it as a DC boosted voltage. The boost device 24 can change the boosted voltage under the control of the control device 34. For example, the boost device 24 includes a switch element and can change the boosted voltage by controlling the switching frequency of the switch element.

[0026] The multilevel inverter 26 is electrically connected to the boost device 24. The multilevel inverter 26 includes a plurality of switching elements. The multilevel inverter 26 is configured to be able to output a pulse voltage of 3 levels or more. The multilevel inverter 26 can also output a pulse voltage of 2 levels.

[0027] The multilevel inverter 26 is configured to be able to change the number of levels of the output pulse voltage. For example, the multilevel inverter 26 can output a pulse voltage of any number of levels determined from 2 to 8 levels by controlling the operation of the switching elements under the control of the control device 34. In this example, the multilevel inverter 26 can make a seven-stage change in the number of levels from 2 to 8 levels.

[0028] It should be noted that 1 level is equivalent to direct current and cannot be a pulse voltage, so it is not the object of the number of levels of the multilevel inverter 26. In addition, the range in which the multilevel inverter 26 can select the number of levels is not limited to the 2 to 8 level mode. The multilevel inverter 26 only needs to be configured to be able to determine the number of levels from a plurality of numbers of levels including at least 3 levels or more.

[0029] In addition, the multilevel inverter 26 can change the output voltage by controlling the operation of the switching elements under the control of the control device 34.

[0030] The multilevel inverter 26 converts the DC boost voltage of the boost device 24 into an AC voltage and outputs it. For example, the multilevel inverter 26 generates a pulse voltage of a determined number of levels by performing predetermined modulation on the boost voltage supplied from the boost device 24 using the switching elements. The generated pulse voltage substantially becomes a sinusoidal AC voltage. The multilevel inverter 26 substantially outputs an AC output voltage by outputting the generated pulse voltage.

[0031] The electric generator 20 is electrically connected to the multilevel inverter 26. The electric generator 20 is driven using the output voltage of the multilevel inverter 26 supplied from the multilevel inverter 26.

[0032] The wheel 28 is mechanically connected to the electric generator 20 via a shaft and a gear mechanism (not shown). The wheel 28 rotates as the electric generator 20 is driven.

[0033] Figure 2 It is a circuit diagram showing an example of the configuration of the multilevel inverter 26. As Figure 2 shown, the multilevel inverter 26 is constituted by, for example, a circuit method of the flying capacitor method. It should be noted that the circuit method of the multilevel inverter 26 is not limited to the flying capacitor method, and it can also be constituted by any known circuit method such as the cascaded H-bridge method and the diode clamping method. Hereinafter, the flying capacitor method will be taken as an example for explanation.

[0034] As shown Figure 2 in FIG. Figure 2 , the multilevel inverter 26 includes a plurality of switching elements 50, a plurality of diodes 52, and a plurality of capacitor units 54. The switching element 50 is, for example, a semiconductor switch such as an IGBT (Insulated Gate Bipolar Transistor). The capacitor unit 54 is, for example, a condenser.

[0035] The diode 52 is connected in anti-parallel with respect to the switching element 50. One diode 52 is connected to one switching element 50. Hereinafter, for the sake of convenience of explanation, a set composed of one switching element 50 and one diode 52 connected in anti-parallel may sometimes be referred to as a switching unit.

[0036] In the multilevel inverter 26, a plurality of switching units are connected in series to form an arm. Both ends of the arm become input terminals 56. The input terminals 56 are connected to the boost device 24. The center of the arm becomes an output terminal 58. The output terminal 58 is connected to the motor generator 20.

[0037] The number of switching units on the side of one input terminal 56 with respect to the output terminal 58 is the same as the number of switching units on the side of the other input terminal 56 with respect to the output terminal 58. The multilevel inverter 26 can increase the maximum value of the number of determinable levels as the number of switching units between one input terminal 56 and the output terminal 58 increases.

[0038] The capacitor unit 54 is connected in parallel with a part of the arm. More specifically, the capacitor unit 54 is provided between a node between the switching units between one input terminal 56 and the output terminal 58 and a node between the switching units between the other input terminal 56 and the output terminal 58. The capacitor unit 54 is connected to the arm in such a manner that the number of switching units between the node where the capacitor unit 54 is connected to the arm on the side of one input terminal 56 and the output terminal 58 is the same as the number of switching units between the node where the capacitor unit 54 is connected to the arm on the side of the other input terminal 56 and the output terminal 58. The capacitor unit 54 floats in a circuit in the flying capacitor method.

[0039] If an input voltage E is input to the input terminal 56, each capacitor unit 54 holds a voltage reduced by a predetermined amount different for each capacitor unit 54 based on the input voltage E. The multilevel inverter 26 can output a pulsed voltage of a set number of levels by adding and subtracting the voltage values of each capacitor unit 54.

[0040] In the multilevel inverter 26, for example, a carrier phase shift modulation method is adopted as the modulation method. The carrier phase shift modulation method is a method in which the phases of (m - 1) carrier waves corresponding to the m levels are equally displaced and compared with the modulation wave. The multilevel inverter 26 can control the on / off times of the respective switching elements 50 by performing modulation of the carrier phase shift modulation method, thereby generating a pulse voltage of a predetermined number of levels.

[0041] Figure 3 is a graph showing the relationship between the rotational speed and torque of the motor generator 20 for each number of levels of the multilevel inverter 26. As Figure 3 shown, as the number of levels of the multilevel inverter 26 increases, the rotational speed and torque of the motor generator 20 increase.

[0042] That is, if the number of levels is increased, the motor generator 20 can output a relatively high torque. In other words, if the number of levels is decreased, the motor generator 20 can only output a relatively low torque, thereby being able to limit the torque.

[0043] However, in the multilevel inverter 26, a sound associated with the switching operation is generated with the switching operation of the switching element 50. The driver of the vehicle 1 can hear the sound generated from the multilevel inverter 26.

[0044] In the multilevel inverter 26, the pitch of the generated sound varies depending on the number of levels. In the multilevel inverter 26, when the number of levels is changed, the pitch of the generated sound changes corresponding to the change in the number of levels.

[0045] Figure 4 shows an example of the spectrum of the sound generated when the number of levels is 2 levels. Figure 5 shows an example of the spectrum of the sound generated when the number of levels is 3 levels. Figure 6 shows an example of the spectrum of the sound generated when the number of levels is 5 levels. In Figures 4 - 6 the horizontal axis is the frequency of the sound, and the vertical axis is the normalized amplitude. In Figures 4 - 6 the peaks, that is, the portions where the amplitude sharply increases, appear at multiple frequencies.

[0046] In Figure 4 the peaks of the amplitude appear at a relatively low frequency (for example, 2 kHz), and the intervals between the peaks are relatively narrow. In Figure 5 the peaks of the amplitude are shifted more toward the high - frequency side (for example, 4 kHz) compared to the case of Figure 4 and the intervals between the peaks become wider compared to the case of Figure 4 In Figure 6 the peaks of the amplitude are shifted more toward the high - frequency side (for example, 8 kHz) compared to the case of Figure 5 and the intervals between the peaks are...Figure 5 becomes wider compared to the case of

[0047] That is, in the multilevel inverter 26, the lower the number of levels, the lower the pitch of the generated sound, and the higher the number of levels, the higher the pitch of the generated sound.

[0048] Therefore, for example, when the number of levels changes from a relatively low state to a relatively high state, the pitch of the generated sound changes to the higher pitch side. Additionally, for example, when the number of levels changes from a relatively high state to a relatively low state, the pitch of the generated sound changes to the lower pitch side.

[0049] Return Figure 1 will be described. The shift operation device 30 is configured to be able to receive a shift operation that instructs a change or specification of a gear position. The shift operation device 30 can be a paddle shift device or a gear lever device. The shift operation device 30 includes a sensor that can detect the received shift operation.

[0050] The acceleration operation device 32 is configured to be able to receive an acceleration operation that instructs the acceleration of the vehicle 1. The acceleration operation device 32 is, for example, an accelerator pedal. The acceleration operation device 32 includes a sensor that can detect the acceleration operation amount of the received acceleration operation.

[0051] The control device 34 includes one or more processors 70 and one or more memories 72 connected to the processor 70. The memory 72 includes a ROM that stores programs and the like, and a RAM that serves as a work area. The processor 70 of the control device 34 cooperates with the programs included in the memory to control the entire vehicle 1.

[0052] The processor 70 of the control device 34 also functions as a drive control unit 74 that controls the drive of the motor generator 20. The drive control unit 74 substantially controls the drive of the motor generator 20 by controlling the boost device 24 and the multilevel inverter 26.

[0053] The drive control unit 74 can obtain the driver's shift operation through the shift operation device 30. The drive control unit 74 determines the boost voltage of the boost device 24 based on the shift operation obtained through the shift operation device 30.

[0054] The drive control unit 74 can obtain the driver's acceleration operation through the acceleration operation device 32. The drive control unit 74 determines the output voltage of the multilevel inverter 26 based on the acceleration operation obtained through the acceleration operation device 32.

[0055] The drive control unit 74 determines the number of levels of the multilevel inverter 26 based on the boosted voltage of the boosting device 24 and the output voltage of the multilevel inverter 26. It should be noted that the determination of the number of levels will be described in detail later.

[0056] The drive control unit 74 sends a boosted voltage command to the boosting device 24, and this boosted voltage command indicates the determined boosted voltage. If the boosting device 24 receives the boosted voltage command, it causes the switching element to operate at a switching frequency corresponding to the boosted voltage shown in the received boosted voltage command, and outputs this boosted voltage to the multilevel inverter 26.

[0057] In addition, the drive control unit 74 sends a number-of-levels command and an output voltage command to the multilevel inverter 26. This number-of-levels command indicates the determined number of levels of the multilevel inverter 26, and this output voltage command indicates the determined output voltage of the multilevel inverter 26. If the multilevel inverter 26 receives the number-of-levels command and the output voltage command, it causes each switching element 50 to operate in such a way as to become the number of levels shown in the received number-of-levels command and to become the output voltage shown in the received output voltage command. Thereby, the multilevel inverter 26 outputs a pulse voltage to the motor generator 20, and this pulse voltage is a pulse voltage of the indicated number of levels and substantially becomes the indicated output voltage.

[0058] Figure 7 It is a diagram showing the relationship among the gear position of the shift operation device 30, the boosted voltage of the boosting device 24, the output voltage of the multilevel inverter 26, and the number of levels. In the memory 72 of the control device 34, setting map information equivalent to Figure 7 the relationship diagram is pre-stored.

[0059] As Figure 7 shown, in the drive system 10, the gear position is associated with the boosted voltage. More specifically, it is set that the boosted voltage becomes higher as the gear position becomes a higher-speed gear position.

[0060] In Figure 7 the example, the gear positions are set to be from the first gear to the eighth gear. It should be noted that the first gear is the lowest-speed gear position, and the eighth gear is the highest-speed gear position.

[0061] In Figure 7 the example, when the gear position is the first gear, the boosted voltage is 200V. When the gear position is the second gear, the boosted voltage is 300V. When the gear position is the third gear, the boosted voltage is 400V. When the gear position is the fourth gear, the boosted voltage is 500V. When the gear position is the fifth gear, the boosted voltage is 600V. When the gear position is the sixth gear, the boosted voltage is 700V. When the gear position is the seventh gear, the boosted voltage is 800V. When the gear position is the eighth gear, the boosted voltage is 900V.

[0062] The drive control unit 74 determines the boosting voltage of the boosting device 24 such that the boosting voltage of the boosting device 24 increases as the gear position shifts to the high-speed side and decreases as the gear position shifts to the low-speed side.

[0063] In addition, the upper limit value of the voltage range that the multilevel inverter 26 can output is related to the input voltage of the multilevel inverter 26. In the drive system 10, since the boosting voltage becomes the input voltage of the multilevel inverter 26, if the boosting voltage is different, the upper limit value of the output voltage of the multilevel inverter 26 becomes different. As described above, since the gear position is associated with the boosting voltage, the upper limit value of the output voltage of the multilevel inverter 26 is different for each gear position.

[0064] In Figure 7 the example, the output voltage Vup1 is the upper limit value of the output voltage in the first gear. The output voltage Vup2 is the upper limit value of the output voltage in the second gear. The output voltage Vup3 is the upper limit value of the output voltage in the third gear. The output voltage Vup4 is the upper limit value of the output voltage in the fourth gear. The output voltage Vup5 is the upper limit value of the output voltage in the fifth gear. The output voltage Vup6 is the upper limit value of the output voltage in the sixth gear. The output voltage Vup7 is the upper limit value of the output voltage in the seventh gear. The output voltage Vup8 is the upper limit value of the output voltage in the eighth gear.

[0065] The relatively higher the boosting voltage is, that is, the relatively higher the gear position is on the high-speed side, the higher the upper limit value of the output voltage of the multilevel inverter 26. The relatively lower the boosting voltage is, that is, the relatively lower the gear position is on the low-speed side, the lower the upper limit value of the output voltage of the multilevel inverter 26.

[0066] In this way, in the drive system 10, the upper limit value of the output voltage of the multilevel inverter 26 corresponding to the boosting voltage of the boosting device 24 is set for each gear position.

[0067] In addition, in the drive system 10, within the voltage range that the multilevel inverter 26 can output, the number of levels of the multilevel inverter 26 corresponds to the output voltage of the multilevel inverter 26. More specifically, it is set that the number of levels of the multilevel inverter 26 increases as the output voltage of the multilevel inverter 26 increases.

[0068] For example, in Figure 7In the example, the voltage range that the multilevel inverter 26 can output is distinguished according to the number of levels from 2 to 8 levels. It is set that the number of levels of the multilevel inverter 26 changes by 1 level successively in order from 2 levels to 8 levels as the voltage range that the multilevel inverter 26 can output moves from the lower limit value to the upper limit value. In addition, each number of levels is set at approximately equal intervals within the voltage range that the multilevel inverter 26 can output, so that the widths of the output voltages at each number of levels from 2 to 8 levels are approximately equal.

[0069] In addition, the correspondence between the number of levels and the output voltage is set for each gear position, in other words, for each boost voltage. In any gear position from the 1st gear to the 8th gear, within the voltage range that the multilevel inverter 26 corresponding to each gear position can output, it is also approximately equally spaced according to the number of levels from 2 to 8 levels.

[0070] As described above, since the upper limit value of the output voltage of the multilevel inverter 26 becomes lower as the gear position moves to the low-speed side, the width of the output voltage corresponding to each number of levels divided into 2 to 8 levels becomes narrower as the gear position moves to the low-speed side.

[0071] Here, for example, it is assumed that the currently specified gear position is the 6th gear. In this case, the drive control unit 74 determines the boost voltage to be 700V. In addition, for example, the drive control unit 74 determines the Figure 7 output voltage Va in as the current output voltage of the multilevel inverter 26. In this way, the drive control unit 74 determines the number of levels of the multilevel inverter 26 to be 6 levels based on the 700V boost voltage, the output voltage Va, and the set mapping information. In this way, the boost voltage of the boost device 24, the output voltage of the multilevel inverter 26, and the number of levels are determined.

[0072] In addition, for example, when determining that the number of levels of the multilevel inverter 26 is 6 levels, by operating the multilevel inverter 26 according to 6 levels, a sound with a pitch corresponding to the 6 levels is generated. The driver of the vehicle 1 can hear the sound with a pitch corresponding to the 6 levels.

[0073] Figure 8 is a diagram for explaining the case where an upshift operation for raising the gear position is obtained through the shift operation device 30. In Figure 8 the example, it is assumed that an upshift operation for raising the gear position from the 6th gear to the 7th gear is obtained in the state where the gear position is the 6th gear. In Figure 8 only shows Figure 7 the part related to the gear position of concern in, and the parts related to other gear positions are omitted.

[0074] As Figure 8As shown, when the gear position is in the 6th gear and an upshift operation to raise the gear position to the 7th gear is obtained, the drive control unit 74 determines 800V as the boosted voltage corresponding to the 7th gear.

[0075] That is, corresponding to obtaining the upshift operation, the drive control unit 74 causes the boosted voltage of the boosting device 24 to rise compared to the boosted voltage before obtaining the upshift operation.

[0076] In addition, as Figure 8 shown, let the current output voltage of the multilevel inverter 26 be the output voltage Vb. In this example, when the gear position is in the 6th gear, the number of levels of the multilevel inverter 26 is 6 levels.

[0077] If an upshift operation to raise the gear position to the 7th gear is obtained, then as Figure 8 indicated by the thick arrow, while maintaining the current output voltage Vb of the multilevel inverter 26, the boosted voltage and the gear position change. Then, based on the 800V boosted voltage corresponding to the 7th gear, the output voltage Vb, and the set mapping information, the drive control unit 74 determines the number of levels of the multilevel inverter 26 to be 5 levels.

[0078] That is, corresponding to the rise of the boosted voltage of the boosting device 24, the drive control unit 74 causes the number of levels of the multilevel inverter 26 to decrease compared to the number of levels before obtaining the upshift operation.

[0079] If the number of levels decreases, the torque of the motor generator 20 decreases. Therefore, if an upshift operation is performed, there is a case where at the moment when the upshift operation is performed, the torque of the motor generator 20 is smaller than the torque before the upshift operation. That is, in the drive system 10, by the driver performing an upshift operation, the torque of the motor generator 20 can be freely decreased to a torque that conforms to the driver's intention.

[0080] In addition, when the number of levels of the multilevel inverter 26 decreases corresponding to obtaining the upshift operation, the pitch of the sound of the multilevel inverter 26 changes to the lower pitch side compared to before obtaining the upshift operation. That is, in the drive system 10, the situation of raising the gear position corresponding to the upshift operation can be shown by the change in the pitch of the sound generated from the multilevel inverter 26.

[0081] The driver of the vehicle 1 can hear the sound with the pitch changing to the lower pitch side by performing an upshift operation. Thus, the driver of the vehicle 1 can recognize that an upshift operation has been performed by the sound.

[0082] It should be noted that even if the number of levels is reduced to 5 levels by setting to the 7th gear using an upshift operation, the number of levels can then be increased in the state of the 7th gear and returned to 6 levels by increasing the acceleration operation amount. In this way, the driver can freely operate the torque as in a motor vehicle using the gear and the acceleration operation amount.

[0083] In addition, depending on the relationship between the current output power of the multilevel inverter 26 and the gears before and after the upshift operation, there are also cases where the number of levels is not changed.

[0084] Figure 9 It is a diagram for explaining the case where a downshift operation that reduces the gear is obtained through the shift operation device 30. In Figure 9 the example, it is assumed that a downshift operation for reducing the gear from the 6th gear to the 5th gear is obtained in the state of the 6th gear. In Figure 9 only shows Figure 7 the part related to the gear of concern in

[0085] As Figure 9 shown, in the state of the 6th gear, if a downshift operation for reducing the gear to the 5th gear is obtained, the drive control unit 74 determines 600V as the boost voltage corresponding to the 5th gear.

[0086] That is, corresponding to obtaining the downshift operation, the drive control unit 74 causes the boost voltage of the boost device 24 to decrease compared to the boost voltage before obtaining the downshift operation.

[0087] In addition, as Figure 9 shown, it is assumed that the current output voltage of the multilevel inverter 26 is the output voltage Vc. In this example, when the gear is in the 6th gear, the number of levels of the multilevel inverter 26 is 4 levels.

[0088] If a downshift operation for reducing the gear to the 5th gear is obtained, then as Figure 9 the thick arrow in

[0089] shown, while maintaining the current output voltage Vc of the multilevel inverter 26, the boost voltage and the gear change. Then, the drive control unit 74 determines 5 levels as the number of levels of the multilevel inverter 26 based on the 600V boost voltage corresponding to the 5th gear, the output voltage Vc, and the set mapping information.

[0090] If the number of levels increases, the torque of the motor generator 20 increases. Therefore, if a downshift operation is performed, there is a case where the torque of the motor generator 20 at the moment when the downshift operation is performed is higher than the torque before the downshift operation. That is, in the drive system 10, by the driver performing a downshift operation, the torque of the motor generator 20 can be freely increased to a torque that conforms to the driver's intention.

[0091] In addition, when the number of levels of the multilevel inverter 26 increases in response to obtaining a downshift operation, the pitch of the sound of the multilevel inverter 26 changes to the higher pitch side compared to before obtaining the downshift operation. That is, in the drive system 10, it is possible to indicate a downshift corresponding to the downshift operation by a change in the pitch of the sound generated from the multilevel inverter 26.

[0092] The driver of the vehicle 1 can hear a sound with a pitch that changes to the higher pitch side by performing a downshift operation. Thus, the driver of the vehicle 1 can recognize that a downshift operation has been performed by the sound.

[0093] It should be noted that even if the number of levels is increased to 5 levels by setting to the 5th gear using a downshift operation, it is possible to subsequently decrease the number of levels and return to 4 levels in the state of the 5th gear by reducing the amount of acceleration operation. In this way, the driver can freely operate the torque as in a gasoline vehicle using the gear and the amount of acceleration operation.

[0094] In addition, depending on the relationship between the current output power of the multilevel inverter 26 and the gears before and after the downshift operation, there is also a case where the number of levels is not changed.

[0095] In this way, the drive system 10 can improve the operating feeling of the vehicle 1 felt by the driver of the vehicle 1. For example, the drive system 10 can provide the driver of the vehicle 1 with an operating feeling just like driving a gasoline vehicle.

[0096] Figure 10 It is a diagram for explaining another example in the case where a downshift operation is obtained by the shift operation device 30. In Figure 10 the example, it is assumed that a downshift operation for reducing the gear from the 6th gear to the 5th gear is obtained in the state of the 6th gear. In Figure 10 only the part related to the gear of interest in Figure 7 is shown, and the parts related to other gears are omitted.

[0097] As Figure 10 shown, in the state of the 6th gear, if a downshift operation for reducing the gear to the 5th gear is obtained, the drive control unit 74 determines 600V as the boost voltage corresponding to the 5th gear.

[0098] In addition, as Figure 10As shown, assume that the current output voltage of the multilevel inverter 26 is the output voltage Vd. In this example, when the gear position is in the 6th gear, the number of levels of the multilevel inverter 26 is 8 levels.

[0099] In this example, if a downshift operation to lower the gear position to the 5th gear is obtained, the output voltage Vd of the multilevel inverter 26 will exceed the output voltage Vup5 at the upper limit value at the lowered 5th gear based on the downshift operation.

[0100] In such a case, as Figure 10 shown by the thick arrow, at the lowered 5th gear based on the downshift operation, the drive control unit 74 limits the output voltage of the multilevel inverter 26 to the output voltage Vup5 as the upper limit value.

[0101] That is, the drive control unit 74 limits the output voltage to the upper limit value after lowering based on the downshift operation when the limit conditions related to the output voltage of the multilevel inverter 26 are satisfied. The limit conditions are that both the following first condition and second condition are satisfied. The first condition is that a downshift operation is obtained. The second condition is that the output voltage of the multilevel inverter 26 exceeds the upper limit value of the output voltage of the multilevel inverter 26 at the gear position after lowering based on the downshift operation.

[0102] Thereby, the drive control unit 74 can output an appropriate output voltage corresponding to the gear position from the multilevel inverter 26.

[0103] In addition, since the output voltage is limited when the above limit conditions are satisfied, for example, the driver can also perform a driving operation such as intentionally limiting the output voltage and intentionally reducing the torque of the motor generator 20 by performing a downshift operation.

[0104] Figure 11 is a flowchart showing the flow of the operation of the drive control unit 74. The drive control unit 74 repeatedly executes Figure 11 a series of processes at each arrival of a predetermined interruption time that comes at a predetermined cycle.

[0105] If the predetermined interruption time arrives, the drive control unit 74 determines whether a shift operation for changing the gear position from the current gear position is obtained through the shift operation device 30 (S10). The shift operation can be an operation that absolutely designates the gear position or an operation that relatively designates with respect to the current gear position.

[0106] When a shift operation for changing the gear position from the current gear position is obtained (Yes in S10), the drive control unit 74 updates the gear position according to the obtained shift operation (S11). It should be noted that the drive control unit 74 can store the updated gear position in the memory 72.

[0107] After the gear position is updated, the drive control unit 74 updates the boost voltage of the boost device 24 based on the updated gear position (S12), and proceeds to the process of step S15. It should be noted that the drive control unit 74 may also store the updated boost voltage in the memory.

[0108] If, for example, the shift operation obtained in step S10 is an upshift operation, the drive control unit 74 increases the boost voltage in step S12. Additionally, if, for example, the shift operation obtained in step S10 is a downshift operation, the drive control unit 74 decreases the boost voltage in step S12.

[0109] Furthermore, in step S10, when no shift operation that changes the gear position from the current gear position is obtained (No in S10), the drive control unit 74 maintains the current gear position (S13). Since the gear position is maintained, the drive control unit 74 also maintains the boost voltage of the boost device 24 (S14), and proceeds to the process of step S15.

[0110] In step S15, the drive control unit 74 generates a boost voltage command based on the updated boost voltage in step S12 or the maintained boost voltage in step S14 (S15).

[0111] Next, the drive control unit 74 obtains the current acceleration operation amount through the acceleration operation device 32 (S16). The drive control unit 74 determines the output voltage of the multilevel inverter 26 based on the obtained current acceleration operation amount (S17).

[0112] Next, the drive control unit 74 determines whether the limit conditions related to the output voltage of the multilevel inverter 26 at the updated gear position in step S11 or the maintained gear position in step S13 are satisfied (S18). When the output voltage of the multilevel inverter 26 in step S17 exceeds the upper limit value at the updated gear position in step S11 or the maintained gear position in step S13, the drive control unit 74 may determine that the limit conditions are satisfied.

[0113] When the limit conditions are satisfied (Yes in S18), the drive control unit 74 limits the output voltage of the multilevel inverter 26 to the upper limit value of the output voltage of the multilevel inverter 26 at the reduced gear position based on the downshift operation (S19). Thereafter, the drive control unit 74 proceeds to the process of step S20.

[0114] When the limit conditions are not satisfied (No in S18), the drive control unit 74 directly proceeds to the process of step S20.

[0115] In step S20, the drive control unit 74 determines the number of levels of the multilevel inverter 26. More specifically, in the case where the limitation of step S19 is performed, the drive control unit 74 determines the number of levels based on the output voltage of the multilevel inverter 26 after the limitation, the boost voltage determined in step S12 or step S14, and the set mapping information. In the case where the limitation of step S19 is not performed, the drive control unit 74 determines the number of levels based on the output voltage of the multilevel inverter 26 determined in step S17, the boost voltage determined in step S12 or step S14, and the set mapping information.

[0116] If, for example, the shift operation obtained in step S10 is an upshift operation, there is a case where the drive control unit 74 decreases the number of levels in step S20 compared to the number of levels before the upshift operation is obtained. Additionally, if, for example, the shift operation obtained in step S10 is a downshift operation, there is a case where the drive control unit 74 increases the number of levels in step S20 compared to the number of levels before the downshift operation is obtained.

[0117] The drive control unit 74 generates a level number command based on the number of levels determined in step S20 (S21).

[0118] The drive control unit 74 generates an output voltage command (S22). More specifically, in the case where the limitation of step S19 is performed, the drive control unit 74 generates the output voltage command based on the output voltage of the multilevel inverter 26 after the limitation. In the case where the limitation of step S19 is not performed, the drive control unit 74 generates the output voltage command based on the output voltage of the multilevel inverter 26 determined in step S17.

[0119] Then, the drive control unit 74 sends the generated boost voltage command to the boost device 24, and sends the generated level number command and output voltage command to the multilevel inverter 26 (S23), and ends a series of processes.

[0120] As described above, the drive control unit 74 of the drive system 10 of the present embodiment determines the boost voltage of the boost device 24 based on the shift operation obtained by the shift operation device 30. The drive control unit 74 determines the output voltage of the multilevel inverter 26 based on the acceleration operation obtained by the acceleration operation device 32. The drive control unit 74 determines the number of levels of the multilevel inverter 26 based on the boost voltage of the boost device 24 and the output voltage of the multilevel inverter 26.

[0121] In the drive system 10 of the present embodiment, there is a case where if the gear position is changed by a gear shift operation, the number of levels of the multilevel inverter 26 changes. If the number of levels changes, the torque characteristics of the motor generator 20 change. More specifically, if the number of levels increases, the torque of the motor generator 20 increases, and if the number of levels decreases, the torque of the motor generator 20 decreases.

[0122] Therefore, in the drive system 10 of the present embodiment, by the driver performing a gear shift operation, the torque of the motor generator 20 can be freely increased and decreased to a torque that conforms to the driver's intention.

[0123] For example, in a situation such as merging onto a highway, the driver can also intentionally perform a downshift operation to increase the torque of the motor generator 20, thereby rapidly accelerating the vehicle 1 and performing driving that can appropriately merge onto the highway.

[0124] Therefore, in the drive system 10 of the present embodiment, the driver can obtain the operating feeling of the vehicle 1 brought about by the gear shift operation as in the case of a gasoline vehicle.

[0125] In addition, in the drive system 10 of the present embodiment, if the number of levels changes, the pitch of the sound associated with the switching operation of the switching element 50 of the multilevel inverter 26 changes. Therefore, in the drive system 10 of the present embodiment, it is possible to indicate that a gear shift operation has been performed by the change in the sound of the multilevel inverter 26. That is, in the drive system 10 of the present embodiment, it is possible to recall the change in the engine sound during the gear shift operation in a gasoline vehicle by the change in the sound of the multilevel inverter 26.

[0126] Therefore, in the drive system 10 of the present embodiment, from the perspective of such sound, the driver can also obtain the operating feeling of the vehicle 1 brought about by the gear shift operation as in the case of a gasoline vehicle. As a result, in the drive system 10 of the present embodiment, it is possible to provide the driver with the same driving pleasure as during the driving operation of a gasoline vehicle.

[0127] In addition, if the number of levels of the multilevel inverter 26 changes, the efficiency of the multilevel inverter 26 changes. The efficiency is relatively high for levels such as 5 levels and around in the range of 2 to 8 levels, and relatively low for 2 to 3 levels. The efficiency of the multilevel inverter 26 affects the electrical efficiency of the vehicle 1. Thus, in the drive system 10 of the present embodiment, the driver can drive the vehicle 1 with an electrical efficiency that conforms to the driver's Figure 1 intention by performing a gear shift operation.

[0128] In addition, for example, when the gear position is in the 8th gear and the number of levels is 3 levels, the efficiency of the multilevel inverter 26 becomes relatively low, and the electrical efficiency becomes relatively low. However, in this case, since the gear position is in the 8th gear, a relatively high output voltage can be allowed as the output voltage of the multilevel inverter 26.

[0129] In contrast, for example, when the gear position is in the 2nd gear and the number of levels is 5 levels, the efficiency of the multilevel inverter 26 becomes relatively high, and the electrical efficiency becomes relatively high. However, in this case, since the gear position is in the 2nd gear, only a relatively low upper limit value can be allowed as the output voltage of the multilevel inverter 26.

[0130] In this way, by freely changing the gear position using the shift operation, the driver can intentionally widen the voltage range of the output voltage to prioritize driving performance, or can also intentionally prioritize electrical efficiency.

[0131] In addition, in the drive system 10 of the present embodiment, the boost voltage becomes lower as the gear position shifts to the low-speed side. Thus, in the drive system 10 of the present embodiment, the upper limit value of the output voltage of the multilevel inverter 26 becomes lower as the gear position shifts to the low-speed side.

[0132] For example, when the driver is driving at a high speed on a highway or the like, the driver can perform a shift operation to make the gear position on the relatively high-speed side, and when driving at a low speed on a general road or the like, the driver can perform a shift operation to make the gear position relatively low. In this case, the drive system 10 of the present embodiment can stably perform high-speed driving by supplying a relatively high output voltage to the motor generator 20 during high-speed driving. In addition, the drive system 10 of the present embodiment can suppress the output voltage from becoming too high during low-speed driving, thereby improving safety.

[0133] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the present invention is of course not limited to these embodiments. Various modification examples or correction examples can be conceived within the scope described in the claims, and it should be understood that these modification examples or correction examples naturally also belong to the technical scope of the present invention.

[0134] For example, in the above embodiment, when the limit condition is satisfied, the output voltage of the multilevel inverter 26 is limited to the upper limit value. However, when the limit condition is satisfied, the drive control unit 74 may not allow the gear position to be lowered and may maintain the current gear position.

Claims

1. A drive system, characterized in that: have: a gear shift operation device that receives a gear shift operation; an acceleration operation device that receives an acceleration operation; A voltage booster device that boosts the voltage of the battery and outputs the voltage as a DC boosted voltage; A multi-level inverter, comprising a switching element and capable of outputting a pulse voltage of three or more levels, and converting the boosted voltage of the boosting device into an alternating output voltage for output; a motor generator driven by the output voltage of the multi-level inverter; as well as a control device for controlling the voltage boost device and the multi-level inverter, The control device has: one or more processors; and one or more memories connected to the processor, The processor performs a process comprising the following steps: a step of determining the boost voltage of the boost device based on the shift operation acquired by the shift operation device; The step of determining the output voltage of the multilevel inverter based on the acceleration operation acquired by the acceleration operation device; as well as A step of determining the number of levels of the multilevel inverter based on the boosted voltage of the boosting device and the output voltage of the multilevel inverter.

2. The drive system according to claim 1, characterized in that: The multilevel inverter generates a sound associated with a switching operation of the switching element, and a pitch of the sound changes in accordance with a change in the number of levels.

3. The drive system according to claim 1, characterized in that: The processor performs a process including the following steps, determining the boost voltage of the boost device in such a manner that the boost voltage of the boost device increases as the gear shifts toward a high-speed position, and decreases as the gear shifts toward a low-speed position.

4. The drive system according to claim 1, characterized in that: The processor performs a process comprising the following steps: In response to an upshift operation for raising a gear position acquired by the shift operation device, the step of increasing the boosted voltage of the boost device compared to the boosted voltage before the upshift operation is acquired; as well as A step of reducing the number of levels of the multilevel inverter compared to the number of levels before the upshift operation is acquired in accordance with the increase of the boosted voltage of the boost device.

5. The drive system according to claim 4, characterized in that: The multilevel inverter generates a sound associated with the switching action of the switching element, and the pitch of the sound changes in accordance with the change of the level number. When the number of levels of the multilevel inverter decreases in response to the acquisition of the upshift operation, the pitch of the sound of the multilevel inverter changes to a lower pitch than before the acquisition of the upshift operation.

6. The drive system according to claim 1, characterized in that: The processor performs a process comprising the following steps: In response to a downshift operation for lowering a gear position being acquired by the shift operation device, the step of lowering the boosted voltage of the boosting device compared to the boosted voltage before the downshift operation is acquired; as well as A step of increasing the number of levels of the multilevel inverter compared to the number of levels before the downshift operation is acquired in response to a decrease in the boosted voltage of the boost device.

7. The drive system according to claim 6, characterized in that: The multilevel inverter generates a sound associated with the switching action of the switching element, and the pitch of the sound changes in accordance with the change of the level number. When the level number of the multilevel inverter increases in response to the downshift operation being acquired, the pitch of the sound of the multilevel inverter changes to a higher pitch side compared to before the downshift operation is acquired.

8. The drive system according to claim 1, characterized in that: An upper limit value of the output voltage of the multilevel inverter corresponding to the boost voltage of the boost device is set for each gear. The processor executes a process including a step of limiting the output voltage of the multilevel inverter to the upper limit value when a downshift operation to lower the gear position is acquired through the gear shift operation device and the output voltage of the multilevel inverter exceeds the upper limit value of the output voltage of the multilevel inverter at the gear position after the downshift operation.

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