JP5307583B2 - Electric vehicle motor control method and electric vehicle drive device - Google Patents

Description

  The present invention relates to an output characteristic of an electric motor that rotationally drives a drive wheel of a vehicle, a low-speed mode corresponding to a low-speed driving region with a switching line on a control map as a boundary, and driving higher than this. The present invention relates to a motor control method for an electric vehicle that is switched between a high-speed mode that can handle a region.

  Conventionally, in the field of automobiles, a so-called electric vehicle using an electric motor as a power source instead of a conventional vehicle using an internal combustion engine such as a gasoline engine or a diesel engine for the purpose of further improving emission performance and fuel efficiency performance. As is well known, so-called hybrid vehicles using an electric motor in combination with an internal combustion engine have been developed.

  As described above, in a vehicle using an electric motor as at least a part of a power source (hereinafter, such a vehicle is referred to as an electric vehicle) in order to make the output characteristics of the electric motor correspond to various traveling scenes of the vehicle. It is desirable to control the electric motor so as to cover a relatively wide range of rotation speeds.

  For example, in Patent Document 1 below, when a condition such as the rotational speed of the electric motor exceeding a predetermined threshold (switching rotational speed) is established, the connection state of the winding of the electric motor is switched or the field control method is switched. As a result, the output characteristic of the electric motor is changed to a characteristic that can cope with a region closer to a higher rotation.

JP-A-6-225588

  By the way, according to the switching of connection as described above, the output characteristics of the electric motor correspond to the output characteristics corresponding to the low rotation range (hereinafter referred to as the low speed mode) and the high rotation range. When switching between output characteristics (hereinafter referred to as a high speed mode), it is considered that the torque transmitted to the drive wheels of the vehicle temporarily varies due to intermittent changes in the output of the electric motor. In particular, when the vehicle is rapidly accelerating, the shock (switching shock) generated when switching the output characteristics as described above becomes large, and the passenger may feel uncomfortable.

  In this regard, Patent Document 1 discloses that switching of output characteristics as described above is prohibited when it is confirmed that the acceleration exceeds a predetermined threshold. In this way, there is an advantage that it is possible to prevent the occurrence of a large switching shock during acceleration and to ensure passenger comfort.

  However, as described in Patent Document 1, when switching of output characteristics during acceleration (switching from the low speed mode to the high speed mode) is prohibited, the electric motor continues to be operated in the low speed mode during acceleration, so that the high speed The output characteristics cannot be appropriately switched to the high-speed mode at the time of transition to the area, and the drive efficiency of the electric motor may be greatly deteriorated.

  The present invention has been made in view of the above-described circumstances, and effectively reduces the shock generated when the output characteristics are switched while appropriately ensuring the driving efficiency of the electric motor for driving the vehicle. It is an object of the present invention to provide a method and an apparatus capable of doing so.

In order to solve the above problems, the present invention is based on the output characteristics of the electric motor that rotationally drives the drive wheels of the vehicle, with the switching line set on the control map having the load and the rotational speed as parameters . A motor control method for an electric vehicle that switches between a low-speed mode corresponding to a driving region closer to a low rotation and a high-speed mode capable of corresponding to a driving region closer to a higher rotation, and determining an acceleration state of the vehicle And when the acceleration determination step confirms that the vehicle is rapidly accelerating , the switching line is lowered so that the shock generated in the vehicle when the output characteristics are switched is reduced. And a shift step for shifting to the rotation side (claim 1).

According to the present invention, when the output characteristic of the electric motor is switched from the low speed mode to the high speed mode, the shock generated in the vehicle is likely to increase. Since the switching line is shifted in the direction in which the shock at the time of switching is reduced (low rotation side) , the shock can be effectively reduced and passenger comfort can be maintained well. Moreover, unlike the conventional control, the control according to the present invention only changes the position of the switching line, and does not prohibit the switching of the output characteristic itself. Therefore, the switching of the output characteristic based on the switching line is performed even during rapid acceleration. Surely executed. For this reason, the problem that the output characteristics of the electric motor do not switch in the low speed mode during the rapid acceleration of the vehicle can be solved, and the deterioration of the drive efficiency of the electric motor due to such a problem can be effectively prevented. There is an advantage.

In the present invention, preferably, in the shift step, the shift amount of the switching line toward the low rotation side is set to be larger as the load becomes higher (Claim 2).

  In this way, the motor current surge phenomenon (a phenomenon in which a temporary high current flows through the electric motor) can be suppressed by relatively advancing the switching timing to the high speed mode in the high load region. There is an advantage that the loss and damage of the motor due to the surge phenomenon can be effectively prevented.

  In the present invention, preferably, the switching line is variably set based on a voltage value of a power supply device that supplies power to the electric motor, and the switching line after the setting is shifted in the shift step. ).

In this way, by setting the switching line variably based on the voltage value of the power supply device that affects the output characteristics of the electric motor, the output characteristics can be set at an appropriate timing considering the influence of the change in the power supply voltage. with switching can be carried out in, is sometimes sudden acceleration, by shifting the switching line after the setting to the low rotation side, while properly considering the change in the power supply voltage, effective shock when the output characteristic changeover There is an advantage that it can be reduced.

  In the above method, the voltage value of the power supply device at the time when the output characteristic is switched is predicted based on the voltage change rate at the initial stage of acceleration, and the switching line is variably set based on the predicted value. (Claim 4).

In this way, even when it is difficult to accurately detect the voltage value of the power supply device due to abrupt change, the position of the switching line can be appropriately determined using the predicted voltage value. There is an advantage.

  In the present invention, preferably, when it is confirmed in the acceleration determination step that the vehicle is decelerating rapidly, the switching line is shifted to the low rotation side in the shift step.

  In this way, it is possible to suppress the induced voltage when the output characteristics of the electric motor are switched from the high speed mode to the low speed mode when the vehicle is suddenly decelerated. There is an advantage that can be prevented.

The present invention also provides an electric motor that rotationally drives a drive wheel of a vehicle, and the output characteristics of the electric motor, with a switching line set on a control map having a load and a rotational speed as parameters as a boundary. The drive means for an electric vehicle comprising a control means for switching between a low-speed mode corresponding to the driving region and a high-speed mode capable of dealing with a driving region closer to higher rotation than the driving region. and acceleration determination means for determining the acceleration state of the vehicle, when the said vehicle is suddenly accelerated is confirmed by the pressurized deceleration determining means, so that the shock is reduced which occurs to the vehicle at the time of switching of the output characteristic And a shift means for shifting the switching line to the low rotation side (Claim 6).

  Even in the case of the present invention, it is possible to obtain the same operational effects as in the case of the motor control method described above.

  As described above, according to the present invention, there is an advantage that shock generated when the output characteristics are switched can be effectively reduced while appropriately ensuring the driving efficiency of the electric motor for driving the vehicle.

1 is a schematic plan view showing an overall configuration of an electric vehicle drive device to which a motor control method according to an embodiment of the present invention is applied. It is a block diagram which shows the control system of the said drive device for electric vehicles. It is a circuit diagram which shows electric structures, such as an electric motor and an inverter, in the said drive device for electric vehicles. It is a figure which shows the output characteristic of the said electric motor. It is a figure for demonstrating the control map for the said electric motor set corresponding to the said output characteristic changing with battery voltages. It is a flowchart which shows the content of the control action performed with respect to the said electric motor. It is a figure for demonstrating the driving | running | working area | region where the control which determines the acceleration state of a vehicle is performed. It is a figure for demonstrating a mode that a switching line is shifted at the time of sudden acceleration. It is a figure for demonstrating a mode that a switching line is shifted at the time of sudden deceleration. It is a figure for demonstrating a mode that the induced voltage of an electric motor changes at the time of deceleration of a vehicle. It is a figure for demonstrating that the excessive rise of an induced voltage can be prevented by shifting a switching line to the low rotation side.

  FIG. 1 is a schematic plan view showing an overall configuration of an electric vehicle drive device to which a motor control method according to an embodiment of the present invention is applied, and FIG. 2 is a block diagram showing a control system of the electric vehicle drive device. is there. The drive device for an electric vehicle shown in these drawings is configured as a drive device for driving an electric vehicle 1 (hereinafter simply referred to as a vehicle 1) composed of a hybrid vehicle. Specifically, the electric vehicle drive device includes an engine 2 that is a gasoline engine or a diesel engine provided as a power source for power generation, and starts the engine 2 when necessary, and obtains driving force from the engine 2. A generator 3 for generating electric power, an electric motor 5 provided as a driving power source, and a battery 9 (corresponding to the power supply device according to the present invention) for storing the electric power generated by the generator 3 and supplying the electric power to a necessary location The first inverter 11 and the second inverter 12 that drive the generator 3 and the electric motor 5 by converting the power supplied from the battery 9 to alternating current, and the controller 15 that comprehensively controls these components (according to the present invention). Equivalent to control means).

  The electric motor 5 is linked to a drive shaft 8 via a gear train 6 and a differential device 7, and passes through a power transmission path including the gear train 6, the differential device 7, and the drive shaft 8. Thus, the driving force of the electric motor 5 is transmitted to the pair of left and right drive wheels 16 connected to the drive shaft 8. In the vehicle 1 of the present embodiment, two of the four wheels provided on the front, rear, left and right are drive wheels 16 and the remaining wheels are driven wheels 17.

  The electric motor 5 is composed of, for example, a three-phase AC synchronous motor or the like, and receives power from the battery 9 via the second inverter 12 when necessary, so that the drive shaft 8 and the drive are driven via the gear train 6 and the like. While driving the wheel 16, the vehicle is configured to generate power by obtaining a driving force from the drive shaft 8 during deceleration or traveling downhill, and to store the generated power in the battery 9.

  The generator 3 receives a supply of electric power from the battery 9 via the first inverter 11 when the engine 2 is started, thereby forcibly rotating the crankshaft of the engine 2 to start the engine 2, and It has both functions as an alternator that generates driving power from the crankshaft of the engine 2.

  The controller 15 includes a well-known CPU, ROM, RAM, I / O (input / output interface), and the like, and various control programs necessary for driving the vehicle 1 are stored in the ROM in advance. The RAM stores various work memories necessary for executing the control program.

  As shown in FIG. 2, various sensors provided in each part of the vehicle 1 are electrically connected to the controller 15. Specifically, the controller 15 includes a vehicle speed sensor 30 that detects a traveling speed (vehicle speed) V of the vehicle 1, and an accelerator opening sensor 31 that detects an opening degree TVO of an accelerator pedal (not shown) that is depressed by a driver. From the engine rotation speed sensor 32 that detects the rotation speed of the crankshaft of the engine 2, the generator rotation speed sensor 33 that detects the rotation speed of the generator 3, and the input current input from the battery 9 to the generator 3 or from the generator 3 A generator current sensor 34 that detects an output current output to the battery 9, a motor rotation speed sensor 35 that detects a shaft rotation speed N of the electric motor 5, and a motor current sensor 36 that detects an input / output current of the electric motor 5. And a battery sensor 37 that detects a voltage Vb between terminals of the battery 9 are connected to each other. They are various control information detected by the sensors 30 to 37 is adapted to be inputted as an electric signal to the controller 15.

  And the said controller 15 performs various calculations based on the input information from each said sensors 30-37, and the said engine 2, the generator 3, the electric motor 5, and inverter 11,12 grade | etc., Based on the result Control the overall operation. And by controlling each part by the controller 15 in this way, in the vehicle 1 of this embodiment, the electric motor 5 is driven and controlled based on the accelerator operation or the like of the driver, and the traveling speed of the vehicle 1 is adjusted. For example, when the remaining capacity of the battery 9 decreases, the engine 2 is started and the generator 3 generates power, and the generated power is replenished to the battery 9.

  FIG. 3 is a circuit diagram of the generator 3, the electric motor 5, and the inverters 11 and 12. As shown in this figure, each phase (U phase, V phase, W phase) of the electric motor 5 has two windings composed of a first winding L1 and a second winding L2 connected in series. The second inverter 12 is provided with a switching element Sw as means for switching the path of the current flowing through the windings L1, L2 of the respective phases. Then, according to the switching operation by the switching element Sw, the current Im from the second inverter 12 flows through both the first and second windings L1 and L2, and only the first winding L1 among them. The current-carrying state is switched between the state in which the current Im flows.

  FIG. 4 is a diagram illustrating output characteristics of the electric motor 5. In FIG. 4, a characteristic line A1 indicated by a thick line indicates an output characteristic when a current is passed through both the first and second windings L1 and L2, and a characteristic line A2 indicated by a thin line indicates the first winding. Output characteristics when current is supplied only to L1 are shown. As shown in the figure, when a current is passed through only the first winding L1 (in the case of the characteristic line A2), compared with a case where a current is passed through both the windings L1 and L2 (in the case of the characteristic line A1). Thus, although the shaft torque T of the electric motor 5 decreases, the electric motor 5 can be driven to a higher rotational speed. This is due to the following reason.

  That is, when current flows through the first and second windings L1 and L2 of the electric motor 5, the electric motor 5 has an induced voltage Va corresponding to the motor rotational speed N as shown in FIG. Although this occurs, while this induced voltage Va is smaller than the voltage Vdc on the inverter 12 side, a current Im flows from the inverter 12 side to the electric motor 5 due to the potential difference. However, when the motor rotation speed N further increases from this state and the induced voltage Va becomes substantially equal to the inverter-side voltage Vdc, the current Im does not flow to the electric motor 5, and the limit line AL of the characteristic line A1 in FIG. As shown, the torque T of the electric motor 5 rapidly decreases. Therefore, if the current path is switched by the switching element Sw before the current Im stops flowing so that the current Im bypasses the second winding L2 and flows only to the first winding L1, the motor is driven by that amount. Since the induced voltage Va of the motor 5 decreases, a potential difference can be generated between the inverter 12 and the electric motor 5 even in the region on the higher rotation side than the limit line AL. It becomes possible to drive.

  As described above, in this embodiment, a plurality of windings L1 and L2 connected in series are provided in each phase of the electric motor 5, and a current flows through all or part of the plurality of windings L1 and L2. By switching the path, the output characteristics of the electric motor 5 are characterized by a characteristic corresponding to the driving region near the low rotation (characteristic line A1 in FIG. 4) and a characteristic corresponding to the driving region near the high rotation (characteristic line A2). Is switched as appropriate. In the following description, the state in which the electric motor 5 is controlled so as to obtain output characteristics such as the characteristic line A1 by flowing current through both the first and second windings L1 and L2 is a low speed mode. A state in which the electric motor 5 is controlled so that an output characteristic such as the characteristic line A2 is obtained by passing a current only through the first winding L1 is referred to as a high-speed mode.

  As shown in FIG. 4, the switching between the low speed mode and the high speed mode is performed when the rotation speed N of the electric motor 5 passes through a switching line P set in advance in the overlapping portion between the low speed mode and the high speed mode. To be executed. For example, as indicated by an arrow D1 in the figure, the rotation speed N is lower than the switching line P when the electric motor 5 is driven in the low speed mode because the rotation speed N is lower than the switching line P. In the case of increasing to the high rotation side region, the output characteristics of the electric motor 5 are switched from the low speed mode to the high speed mode. On the other hand, in contrast to the arrow D1, when the electric motor 5 is driven in the high speed mode and the rotation speed N decreases to a region on the lower rotation side than the switching line P, the electric motor 5 is switched from the high speed mode to the low speed mode.

  Here, the switching line P, which is a boundary line between the low speed mode and the high speed mode, is variably set by the controller 15 as shown in FIGS. Specifically, the controller 15 determines the acceleration state while the vehicle 1 is traveling. As a result, when it is confirmed that the vehicle 1 is rapidly accelerating or decelerating, the controller 15 rotates the switching line P for a predetermined rotation. It is configured to variably set within the speed range.

  Returning to FIG. 2 again, the function of the controller 15 relating to the setting of the switching line P will be described in detail. As shown in the figure, the controller 15 includes acceleration determining means 15a, shift means 15b, and storage means 15c as functional elements.

  The acceleration determination means 15a calculates an acceleration value from a change in the vehicle speed V detected by the vehicle speed sensor 30, and determines the acceleration state of the vehicle 1 based on the magnitude or the like.

  The shift means 15b shifts the switching line P when it is confirmed by the acceleration determination means 15a that the host vehicle is rapidly accelerating or decelerating.

  The storage unit 15e stores a control map that is referred to when the shift unit 15b shifts the switching line P.

  FIG. 5 is a diagram for explaining a control map stored in the storage unit 15e. The control map M shown in the figure is composed of a bundle of a plurality of maps M1, M2,... Set according to conditions. Specifically, a plurality of maps M1, M2,... With different rotation speed ranges are prepared according to the voltage Vb between the terminals of the battery 9 detected by the battery sensor 37, and a bundle of these maps is the control map. M is stored in the storage means 15e.

  In other words, the terminal-to-terminal voltage (battery voltage) Vb decreases due to a decrease in the remaining capacity of the battery 37 that supplies power to the electric motor 5 and a voltage drop due to the battery internal resistance when the battery outputs a large current during rapid acceleration. Then, since the upper limit rotational speed of the electric motor 5 is reduced accordingly, the output characteristics of the electric motor 5 are reduced in the direction of the horizontal axis as shown. Therefore, a plurality of maps M1, M2,... Set corresponding to the value of the battery voltage Vb are prepared, and an appropriate map among them is appropriately selected based on the detection value of the battery sensor 37. ing. Note that a map M1 in FIG. 5 is a map when the battery voltage Vb is near the maximum value (voltage at full charge) so that the rotation speed range of the electric motor 5 can be secured most widely. Indicates the nth narrowest map from the map M1. As can be seen by comparing the map M1 and the map Mn, the position of the switching line P is also moved in the direction of the horizontal axis in accordance with the change in the rotation speed region due to the switching of the maps.

  Next, specific contents of the control operation performed by the controller 15 configured as described above will be described with reference to the flowchart of FIG. When this flowchart is started, the controller 15 first detects the vehicle speed V and the rotation speed of the electric motor 5 from the vehicle speed sensor 30, the accelerator opening sensor 31, the motor rotation speed sensor 35, and the battery sensor 37 as detection values of the sensors. N, control for reading the accelerator pedal opening TVO and the voltage across the battery 9 (battery voltage) Vb is executed (step S1). Further, based on the accelerator opening TVO and the like read here, the current required torque of the electric motor 5 is calculated (step S2).

  Next, the controller 15 selects an appropriate map corresponding to the battery voltage Vb read in step S1 from among a plurality of control maps M1, M2,... (See FIG. 5) stored in the storage means 15c. Control to perform is executed (step S3).

  Further, the controller 15 uses the control map (one of M1, M2,...) Selected in step S3 to switch the switching operation in which the current operating state of the electric motor 5 is a reference when switching output characteristics. Control is performed to determine whether or not the line P is in the vicinity (step S4). Specifically, here, the current operating state of the electric motor 5 specified based on the motor rotation speed N read in step S1 and the required torque calculated in step S2 is the region shown in FIG. When it is within a range as indicated by Q, that is, within a predetermined rotational speed range centering on the switching line P, it is determined that the switching line P is in the vicinity.

  When it is determined as YES in step S4 and it is confirmed that the vehicle is in the vicinity of the switching line P, the controller 15 is based on the change between the vehicle speed V read in step S1 and the vehicle speed V previously read. Then, control for calculating the acceleration α of the vehicle 1 is executed (step S5). The acceleration α obtained here is calculated as a positive value if the vehicle 1 is accelerating, and is calculated as a negative value if the vehicle 1 is decelerating.

  Further, the controller 15 executes control for determining whether or not the vehicle 1 is rapidly accelerating based on the value of the acceleration α calculated in step S5 (step S6). That is, the controller 15 determines that the vehicle 1 is rapidly accelerating when the value of the acceleration α is positive and the magnitude is equal to or greater than a predetermined threshold value.

  When it is determined YES in step S6 and it is confirmed that the vehicle 1 is rapidly accelerating, the controller 15 determines the current electric motor 5 based on the operating state of the switching element Sw of the second inverter 12. Control is performed to determine whether or not the output characteristic is set to the low speed mode (step S8). That is, as described above, if the current path is set so that current flows through both of the two windings L1 and L2 of the electric motor 5 in accordance with the operating state of the switching element Sw, the electric motor Since the low speed mode is selected as the output characteristic of the motor 5, it is determined that the electric motor 5 is driven in the low speed mode when the switching element Sw is in the operating state as described above.

  When it is determined YES in step S8 and it is confirmed that the low speed mode is set, the controller 15 is originally set in the control map (one of M1, M2,...) Selected in step S3. The shifted switching line P is shifted to the low rotation side as indicated by an arrow X in FIG. 8 so that the low shock property at the time of switching the output characteristics (when switching from the low speed mode to the high speed mode) is emphasized. Control for shifting the switching line P is executed (step S9).

  That is, in the control map selected in step S3, the switching line P is originally set at a position determined in consideration of the driving efficiency of the electric motor 5 and the like, but the vehicle 1 is suddenly moved as described above. In the acceleration state, when the output characteristic is switched to the high speed mode with the switching line P as a boundary, a considerably large shock (switching shock) occurs in the vehicle 1 due to the torque fluctuation at the time of switching, There is something that makes you feel uncomfortable. Therefore, in this embodiment, when the vehicle 1 is rapidly accelerating, the occupant can shift the switching line P from the normal position to the low rotation side as a direction to reduce the switching shock as described above. I try to reduce the sense of incongruity.

  Here, as can be seen from FIG. 8, the switching line P that is shifted to the low rotation side in step S <b> 9 is largely shifted to the low rotation side in the higher load range (plus side of the vertical axis). That is, assuming that the optimum line that can reduce the switching shock most is the line indicated by the alternate long and short dash line in FIG. 8, in step S9, the high load portion is corrected to the position where the high load portion is corrected to the low rotation side. The switching line P is shifted. This is to reduce the surge of the motor current that occurs when the output characteristic of the electric motor 5 is switched from the low speed mode to the high speed mode with the switching line P as a boundary.

In general, the surge of the motor current that occurs when switching to the high-speed mode (a phenomenon in which the current temporarily becomes excessive) cannot be avoided at a certain level in the control of the motor, but if the surge amount is too large Further, the loss of the motor due to the flow of unnecessary high current increases, and the motor may be damaged. Therefore, in order to suppress such a surge phenomenon, in step S9, as shown in FIG. 8, the shift amount of the switching line P to the low rotation side is set to be larger as the load becomes higher.

  In other words, the surge amount of the motor current tends to increase in the high rotation / high load range where a higher target current value is set. However, it is advantageous in that the amount of surge can be reduced. In consideration of such points, in the step S9, the switching line P is shifted to the lower rotation side in the higher load region, thereby switching to the high speed mode in the higher load region earlier. The surge phenomenon as described above is suppressed.

  Returning to FIG. 6 again, the continuation of the flowchart will be described. When the shift of the switching line P is completed in step S9, the controller 15 determines whether or not the operating state of the electric motor 5 currently operating in the low speed mode has passed the shifted switching line P, that is, Then, control for determining whether or not the region has shifted to a region on the higher rotation side than the switching line P is executed (step S10). That is, the position of the current operating state of the electric motor 5 based on the motor rotation speed N and the required torque acquired in steps S1 and S2 is identified on the control map of FIG. And the shift switching line P after the shift, it is determined whether or not the operating state of the electric motor 5 has shifted to the higher rotation side than the switching line P.

  When it is determined YES in step S <b> 10 and it is confirmed that the shift has shifted to the higher rotation side than the switching line P after the shift, the controller 15 operates the switching element Sw of the second inverter 12 to Control is performed to switch the output characteristics of the electric motor 5 from the low speed mode to the high speed mode by switching the current path so that the current flows only through the first winding L1 of the first and second windings L1, L2. Step S11).

  On the other hand, if it is determined as NO in step S10 and it is confirmed that the shift line P is not shifted to the higher rotation side, the process returns without performing the switching operation as described above, and the electric motor 5 Maintain the output characteristics of the low-speed mode.

  Next, the control operation when it is determined NO in step S6, that is, when the vehicle 1 is not rapidly accelerating will be described. In this case, the controller 15 executes control for determining whether or not the vehicle 1 is decelerating rapidly based on the value of the acceleration α calculated in step S5 (step S7). That is, the controller 15 determines that the vehicle 1 is decelerating rapidly when the value of the acceleration α is negative and the magnitude (absolute value) is equal to or greater than a predetermined threshold value.

  When it is determined YES in step S7 and it is confirmed that the vehicle 1 is decelerating rapidly, the controller 15 determines the current electric motor 5 based on the operating state of the switching element Sw of the second inverter 12. Control for determining whether or not the output characteristic is set to the high speed mode is executed (step S12).

  If it is determined YES in step S12 and it is confirmed that the high-speed mode is set, the controller 15 is originally set in the control map (one of M1, M2,...) Selected in step S3. Control is performed to shift the switched switching line P to the low rotation side as indicated by the arrow Y in FIG. 9 (step S13).

  Such a shift of the switching line P to the low rotation side is performed in order to prevent the induced voltage Va (FIG. 3) of the electric motor 5 from becoming excessive during sudden deceleration. That is, when the output characteristic of the electric motor 5 is switched from the high speed mode to the low speed mode when the vehicle 1 is in the sudden deceleration state as described above, the induced voltage Va at the time of the switching is excessive and the electric motor 5 is damaged. In order to prevent such a situation, the switching line P is shifted to the low rotation side.

  This point will be described in more detail. FIG. 10 is a diagram illustrating a change in the induced voltage Va of the electric motor 5 when the vehicle 1 is decelerated. In this figure, the point indicated by Nt on the horizontal axis represents the rotational speed corresponding to an arbitrary point on the switching line P (hereinafter, such rotational speed is referred to as switching rotational speed Nt). That is, when the motor rotation speed N decreases to the switching rotation speed Nt as the vehicle 1 is decelerated, the output characteristics of the electric motor 5 are switched from the high speed mode to the low speed mode.

  When the output characteristic is switched to the low speed mode, a current flows through both the first and second windings L1, L2 of the electric motor 5 (that is, the number of flux linkages that determines the magnitude of the induced voltage Va increases). Therefore, the induced voltage Va of the electric motor 5 increases instantaneously with the switching rotational speed Nt as a boundary. At this time, if the allowable voltage for guaranteeing the performance of the electric system composed of the electric motor 5, the generator 3, the battery 9, the first inverter 11, and the second inverter 12 is Vmax, the induced voltage at the moment of switching to the low speed mode. The maximum value of Va approaches the allowable voltage Vmax as the value of the switching rotational speed Nt is higher, as shown by the broken line waveform in the figure.

  If the induced voltage Va greatly exceeds the allowable voltage Vmax, any of the electric systems may be damaged. Therefore, care should be taken that the induced voltage Va does not become excessive particularly when the vehicle 1 is decelerated. There is a need.

  Here, in the characteristic diagram of the electric motor shown in FIG. 4, in a region where the torque characteristic with respect to the rotational speed has a negative slope, control called field weakening control is generally performed. This is a control for reducing the induced voltage Va by shifting the phase of the sine wave current for driving the electric motor. When the induced voltage Va of the electric motor 5 exceeds the voltage Vdc of the second inverter 12, This is done to prevent the drive current from flowing. At this time, the amount of decrease in the induced voltage Va can be increased as the amount of phase shift in field weakening control is increased. Therefore, if the induced voltage Va increases as the motor speed increases, the phase shift amount by the field weakening control may be increased accordingly. Here, immediately after switching to the low speed mode, the induced voltage Va increases instantaneously, so that the phase shift amount in the field weakening control needs to be greatly changed instantaneously. However, when the deceleration of the vehicle 1 is relatively large (that is, at the time of sudden deceleration), the waveform of the one-dot chain line in FIG. Thus, the induced voltage Va at the time of switching may greatly exceed the allowable voltage Vmax. Therefore, in this embodiment, when it is confirmed that the vehicle 1 is decelerating rapidly, the switching line P is shifted to the low rotation side as shown in FIG. The speed Nt is shifted to the low rotation side (see the broken line waveform in the figure). As a result, even if there is a temporary increase in the induced voltage Va during sudden deceleration, it is avoided that the induced voltage Va greatly exceeds the allowable voltage Vmax, and damage to the electric system including the electric motor 5 is prevented. Can do.

  Returning to FIG. 6 again, the continuation of the flowchart will be described. When the shifting of the switching line P is completed in step S13, the controller 15 determines whether or not the operating state of the electric motor 5 currently operating in the high speed mode has passed the shifted switching line P, that is, Then, control for determining whether or not the region has shifted to the lower rotation side than the switching line P is executed (step S14). And when it determines with YES here and it has confirmed that it has shifted to the low rotation side rather than the switching line P, the switching element Sw of the said electric motor 5 is operated, and 1st * 2nd coil | winding L1, L2 By switching the current path so that a current flows through both of them, control is performed to switch the output characteristics of the electric motor 5 from the high speed mode to the low speed mode (step S15).

  On the other hand, if it is determined NO in step S14 and it is confirmed that the engine has not shifted to the lower rotation side than the switching line P, the process returns without performing the switching operation as described above, and the electric motor 5 Maintain the output characteristics of the high-speed mode.

  Next, a description will be given of the control operation when it is determined NO in step S7, that is, when the vehicle 1 is not suddenly accelerated or decelerated. In this case, the controller 15 uses the control map selected in step S3 to determine whether or not the operating state of the electric motor 5 has passed the normal switching line P originally set on the control map. That is, control is performed to determine whether or not the operating state has shifted from the low rotation side to the high rotation side or vice versa with the switching line P as a boundary (step S16).

  When it is determined as YES in Step S16 and it is confirmed that the switching line P has been passed, the controller 15 determines whether the operation state of the electric motor 5 has shifted to the low rotation side or the high rotation side from the switching line P. Control is performed to switch the output characteristic of the electric motor 5 from the high-speed mode to the low-speed mode or vice versa depending on whether or not the transition has been made (step S17).

As described above, the electric vehicle drive device of the present embodiment is configured so that the electric motor 5 that rotationally drives the drive wheels 16 of the vehicle 1 and the output characteristics of the electric motor 5 are represented by the switching line P on the control map M. At the boundary, a controller 15 is provided that switches between a low-speed mode corresponding to an operation region closer to a low rotation and a high-speed mode capable of corresponding to an operation region closer to a higher rotation. And in this embodiment, as a control with respect to the said electric motor 5, the step (S6, S7) which determines the acceleration state of the vehicle 1, and the case where it is confirmed that the vehicle 1 accelerates rapidly at this step (S6) (In the case of YES), a step (S9) of shifting the switching line P in the direction in which the shock generated in the vehicle 1 at the time of switching the output characteristic is reduced , that is, the low rotation side (X direction in FIG. 8) is included. The control operation is executed by the controller 15. According to such a configuration, there is an advantage that a shock generated when the output characteristics are switched can be effectively reduced while appropriately securing the driving efficiency of the electric motor 5.

That is, when the vehicle 1 is rapidly accelerating, when the operation state of the electric motor 5 passes through the switching line P and its output characteristic is switched to the high speed mode, the vehicle 1 is considerably changed due to torque fluctuation at the time of switching. Although a large shock may occur, in the above-described embodiment, the shock at the time of switching is effective by shifting the switching line P in a direction (low rotation side) in which the shock at the time of switching is reduced during sudden acceleration. And the passenger comfort can be maintained well. Moreover, unlike the conventional control, the control according to the above embodiment only changes the position of the switching line P, and does not prohibit the switching of the output characteristics. Therefore, the switching of the output characteristics based on the switching line P is not performed. It is executed reliably even during sudden acceleration. For this reason, the problem that the output characteristic of the electric motor 5 does not switch in the low speed mode during the rapid acceleration of the vehicle 1 can be solved, and the deterioration of the drive efficiency of the electric motor 5 due to such a problem is effectively prevented. There is an advantage that can be prevented.

Further, in the above embodiment, as shown in FIG. 8, when the switching line P is shifted in a direction in which the shock at the time of switching is reduced (low rotation side in the above embodiment), the shift to the low rotation side is performed. The amount was set larger as the high load range. According to such a configuration, a current surge phenomenon (a phenomenon in which a high current temporarily flows through the electric motor 5 when switching to the high speed mode) is achieved by relatively advancing the switching timing to the high speed mode in the high load region. There is an advantage that loss and damage of the motor due to the surge phenomenon can be effectively prevented.

  Moreover, in the said embodiment, when it is confirmed by the step which determines the acceleration state of the vehicle 1 that the vehicle 1 is decelerating rapidly (in the case of YES at step S7), the said step is followed by the above step (S13). Since the switching line P is shifted to the low rotation side (see arrow Y in FIG. 9), the induced voltage Va when the output characteristic of the electric motor 5 is switched from the high speed mode to the low speed mode when the vehicle 1 is suddenly decelerated is suppressed. There is an advantage that the electric motor 5 and the like can be effectively prevented from being damaged due to the excessive increase in the induced voltage Va.

  That is, at the time of sudden deceleration, the field weakening control for the electric motor 5 (control for shifting the phase of the sine wave current that drives the electric motor to weaken the induced voltage Va) is not in time, and as shown in FIG. Since Va is likely to exceed the allowable voltage Vmax, the induced voltage Va easily exceeds the allowable voltage Vmax while the switching line P is maintained at the normal position, and the electric motor 5, the generator 3, the battery 9. Any one of the electric systems including the first inverter 11 and the second inverter 12 may be damaged. On the other hand, when the switching line P is shifted to the low rotation side when the vehicle 1 is suddenly decelerated as in the above embodiment, the motor when the electric motor 5 switches from the high speed mode to the low speed mode. Since the rotational speed (switching rotational speed Nt) becomes relatively small, the value of the induced voltage Va at the time of switching the low speed mode is suppressed, and damage to the electric motor 5 and the like due to excessive increase of the induced voltage Va is effectively prevented. There is an advantage that you can.

Moreover, in the said embodiment, according to the power supply voltage value for the electric motor 5, ie, the voltage Vb between the terminals of the battery 9, an appropriate map is selected from the plurality of control maps M (M1, M2,...) Shown in FIG. The switching line P is variably set in accordance with the voltage value Vb (step S3), and at the time of sudden acceleration or sudden deceleration, the set switching line P is set to the subsequent steps S9 or S13. And shifted to the low rotation side . According to such a configuration, the switching line P is variably set according to the battery voltage Vb that affects the output characteristics of the electric motor 5, so that it is possible to appropriately consider the influence due to the change in the battery voltage Vb. The switching of the output characteristics (switching between the low speed mode and the high speed mode) can be performed at the timing, and at the time of sudden acceleration or sudden deceleration, the switching line P after the setting is shifted to the low rotation side to thereby change the battery voltage. There is an advantage that it is possible to effectively prevent a shock at the time of switching the output characteristics and an increase in the induced voltage Va while properly considering the change in Vb.

  In the above embodiment, as shown in the flowchart of FIG. 6, by selecting an appropriate map from the plurality of control maps M (M1, M2,...) Each time according to the detected value of the battery voltage Vb, etc. Although the position of the switching line P is determined while always considering the influence on the output characteristics due to the change in the battery voltage Vb, the control in consideration of the influence of the battery voltage Vb is not limited to this.

  For example, when the vehicle 1 is rapidly accelerating at full throttle and the acceleration is considerably large, the battery voltage Vb changes rapidly, so that the value is sequentially and accurately detected by the battery sensor 37. It may be difficult to do this. Therefore, in such a case, the value of the battery voltage Vb at the time when the electric motor 5 switches to the high speed mode is predicted based on the rate of change of the battery voltage Vb in the early stage of acceleration, and the above control is performed based on this predicted value. By selecting an appropriate map from the map M (M1, M2,...), The switching line P may be variably set at a position corresponding to the predicted value. In this way, even when it is difficult to accurately detect the value of the battery voltage Vb due to abrupt change, the position of the switching line P is appropriately determined using the predicted value of the battery voltage Vb. There is an advantage that you can. This is the same when the vehicle 1 is suddenly decelerated.

  Moreover, although the said embodiment demonstrated the example which applied the control method of this invention with respect to the hybrid type vehicle which used the engine 2 and the electric motor 5 together as a motive power source, the control method of this invention is the electric motor 5. As long as the vehicle is an electric vehicle using at least a part of the power source, it is applicable regardless of the type.

1 vehicle 5 electric motor 9 battery (power supply device)
15 Controller (control means)
15a Acceleration determining means 15b Shift means 16 Driving wheel M (M1, M2...) Control map P Switching line α Acceleration Vb Voltage between terminals of battery (voltage value of power supply device)

Claims (6)

The output characteristics of the electric motor that rotationally drives the drive wheels of the vehicle, and the low speed mode corresponding to the driving region near the low speed with the switching line set on the control map having the load and the rotational speed as parameters, and this A motor control method for an electric vehicle that switches between a high-speed mode that can handle a driving region closer to a higher rotation speed,
An acceleration determination step of determining an acceleration state of the vehicle;
A shift that shifts the switching line to the low rotation side so that a shock generated in the vehicle at the time of switching the output characteristics is reduced when it is confirmed in the acceleration determination step that the vehicle is suddenly accelerating. And a motor control method for the electric vehicle. In the motor control method of the electric vehicle according to claim 1,
In the shifting step, the motor control method for an electric vehicle is characterized in that the shift amount of the switching line to the low rotation side is set to be larger as the load becomes higher. In the motor control method of the electric vehicle according to claim 1 or 2,
A motor control method for an electric vehicle, wherein the switching line is variably set based on a voltage value of a power supply device that supplies power to the electric motor, and the switching line after the setting is shifted in the shift step. . In the motor control method of the electric vehicle according to claim 3,
An electric vehicle characterized in that a voltage value of the power supply device at a time when the output characteristic is switched is predicted based on a voltage change rate at the initial stage of acceleration, and the switching line is variably set based on the predicted value. Motor control method. In the motor control method of the electric vehicle according to any one of claims 1, 2, and 4,
A motor control method for an electric vehicle, wherein when the acceleration determination step confirms that the vehicle is decelerating rapidly, the shift line is shifted to a low rotation side in the shift step. An electric motor that rotationally drives the driving wheels of the vehicle, and the output characteristics of the electric motor correspond to a driving region close to a low rotation speed, with a switching line set on a control map having a load and a rotational speed as parameters. A drive device for an electric vehicle comprising a control means for switching between a low-speed mode and a high-speed mode capable of handling an operation region closer to a higher rotation than this,
The control means includes
Acceleration determining means for determining an acceleration state of the vehicle;
A shift that shifts the switching line to the low rotation side so that a shock generated in the vehicle at the time of switching the output characteristics is reduced when it is confirmed by the acceleration determining means that the vehicle is suddenly accelerating. Means for driving an electric vehicle.

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