Drive system for electric vehicle and electric vehicle equipped with the same

Abstract

To provide a drive system which controls so as to satisfy a required brake torque even in a coil switching period during regeneration of a rotary electric machine.SOLUTION: A drive system for an electric vehicle includes an inverter 3 which supplies an electric power to a rotary electric machine 1, a mechanical type coil switching device 8 which switches a connection state of a rotary electric machine 1 when a rotation speed of the rotary electric machine 1 arrives at a rotary speed threshold and a controller 4 which controls the rotary electric machine 1, the inverter 3 and the mechanical type coil switching device 8. The controller 4 includes an inverter control device 9, a coil switching control device 10 which controls the mechanical type coil switching device 8 and a mechanical brake control device 11 which controls a mechanical brake 16. The inverter control device 9 controls so as to turn the inverter 3 off when switching connection state of the rotary electric machine 1. The mechanical brake control device 11 causes the mechanical brake 16 to compensate a regeneration brake torque of the rotary electric machine 1 which disappears due to turning-off of the inverter 3 upon regeneration state of the rotary electric machine 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a drive system for an electric vehicle equipped with a winding switching device, and to an electric vehicle. [Background technology]

[0002] Patent Document 1, for example, describes a technique for switching motor windings. In Patent Document 1, when switching the windings of a motor used in a compressor of an air conditioner, a first control unit controls the motor to idle, and a second control unit controls the winding changeover switch while the motor is idling. While the motor is idling, the inverter is stopped to prevent current from flowing to the motor. In other words, Patent Document 1 controls the winding changeover switch to switch the motor windings while the inverter is stopped and no current is flowing to the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-145802 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the wiring state is changed while the motor is energized, an arc discharge occurs at the switch contacts, causing problems such as welding of the switch contacts. To prevent this, it is necessary to set up an inverter stop period in which all of the inverter's switching elements are turned off, and change the wiring state during that period. During the inverter stop period, no current is passed to the motor, and torque is zero. This is also true when the motor is regenerating, and the braking torque due to regeneration is zero.

[0005] If the technology described in Patent Document 1 is applied to an electric vehicle, the required brake torque cannot be output during the winding switching period during motor regeneration, and braking force cannot be obtained. On the other hand, if winding switching is not performed during motor regeneration, i.e., during deceleration due to regenerative brake torque, the motor cannot be driven in a wiring state suitable for low-speed rotation, even though the motor rotation speed is in the low-speed rotation range. Patent Document 1 is intended for application to air conditioning compressors, and does not consider the issues involved in applying it to electric vehicles.

[0006] An object of the present invention is to output a required brake torque even during a winding switching period during regeneration of a rotating electric machine, and to drive the rotating electric machine in a suitable connection state even in a low rotation speed range. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a drive system for an electric vehicle including a rotating electric machine that applies rotational torque to wheels during powering and applies braking torque during regeneration, an inverter that supplies power to the rotating electric machine, a mechanical winding switching device that switches a connection state of the rotating electric machine when the rotation speed of the rotating electric machine reaches a predetermined rotation speed threshold, and a control device that controls the rotating electric machine, the inverter, and the mechanical winding switching device, wherein the control device includes an inverter control device that controls the inverter, a winding switching control device that controls the mechanical winding switching device, and a mechanical brake control device that controls a mechanical brake that brakes the wheels, and the inverter control device controls to turn off all switching elements of the inverter when switching the connection state of the rotating electric machine, a winding switching command is output to the winding switching control device after a predetermined period has elapsed since the timing at which all switching elements of the inverter are turned off, and the winding switching control device outputs a winding switching signal to the mechanical winding switching device after receiving the winding switching command from the inverter control device; The mechanical brake control device controls the mechanical brake to compensate for the regenerative brake torque of the rotating electric machine that is lost when all switching elements of the inverter are turned off when the rotating electric machine is in a regenerative state. The predetermined period is set to be shorter during regeneration than during power running. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, it is possible to output the required brake torque even during the winding switching period during regeneration of the rotating electric machine, and to drive the rotating electric machine in a suitable connection state even in the low rotation speed range. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a drive system for an electric vehicle according to a first embodiment of the present invention. [Figure 2] 1 is a diagram showing a winding configuration of a rotating electric machine according to a first embodiment of the present invention; [Figure 3A] 1 is a diagram showing a state in which windings of each phase of a rotary electric machine according to a first embodiment of the present invention are connected in series. [Figure 3B] 1 is a diagram showing a state in which windings of each phase of a rotary electric machine according to a first embodiment of the present invention are connected in parallel. [Figure 4A] FIG. 4 is a diagram showing the relationship between rotation speed and regenerative braking torque. [Figure 4B] FIG. 10 is a diagram showing the relationship between rotation speed and wiring state. [Figure 5] 4 is a flowchart showing a winding switching sequence according to the first embodiment of the present invention. [Figure 6] FIG. 3 is a diagram showing the relationship between rotation speed, mechanical brake torque, and regenerative brake torque according to the first embodiment of the present invention. [Figure 7] 10 is a flowchart showing a winding switching sequence according to the second embodiment of the present invention. [Figure 8A] FIG. 10 is a diagram showing an example of a current flow when the switching elements of the inverter 3 are operating. [Figure 8B] 10 is a diagram showing an example of a flow of a transient current immediately after a switching element of an inverter 3 is turned off. FIG. [Figure 9] FIG. 10 is a schematic diagram showing the attenuation of a transient current immediately after a switching element of an inverter according to Example 2 of the present invention is turned off. [Figure 10] 10 is a flowchart showing a winding switching sequence according to a third embodiment of the present invention. [Figure 11]FIG. 10 is a schematic diagram showing the attenuation of a transient current immediately after a switching element of an inverter according to a third embodiment of the present invention is turned off. [Figure 12] FIG. 10 is a block diagram showing the configuration of a drive system for an electric vehicle according to a fourth embodiment of the present invention. [Figure 13] FIG. 10 is a diagram showing brake torque distribution in a comparative example and a fourth embodiment. [Figure 14] 10 is a flowchart showing a winding switching sequence according to a fifth embodiment of the present invention. [Figure 15] 10A and 10B are diagrams illustrating behaviors of the stator electrodes and the mover electrodes of the mechanical winding switching device according to the fifth embodiment of the present invention. [Figure 16A] FIG. 10 is a schematic diagram showing the attenuation of a transient current immediately after a switching element of an inverter is turned off during power running according to the fifth embodiment of the present invention. [Figure 16B] FIG. 10 is a schematic diagram showing the attenuation of a transient current immediately after a switching element of an inverter is turned off during regeneration according to the fifth embodiment of the present invention. [Figure 17] FIG. 10 is a block diagram showing the configuration of a drive system for an electric vehicle according to a sixth embodiment of the present invention. [Figure 18] FIG. 10 is a block diagram showing the configuration of an electric vehicle drive system according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In principle, identical elements are assigned the same reference numerals in all drawings. Furthermore, descriptions of parts having identical functions will be omitted. Note that the configurations described below are merely examples, and it is not intended that the embodiments of the present invention be limited to the specific embodiments below. [Example]

[0011] A first embodiment of the present invention will be described with reference to FIGS.

[0012] FIG. 1 is a block diagram showing the configuration of a drive system for an electric vehicle according to a first embodiment of the present invention.

[0013] In Figure 1, the drive system for an electric vehicle of the present invention is composed of a rotating electric machine 1, a phase current detection circuit 2, an inverter 3, a controller 4 (control device), a mechanical winding switching device 8, a motor shaft 12, a differential device 13, a drive shaft 14, wheels 15, a mechanical brake 16, and a rotational speed detector 17.

[0014] The rotating electric machine 1 is configured, for example, as a permanent magnet synchronous motor having a plurality of windings, and the start and end of some of the windings are pulled out so that the connection state of each winding can be switched, and are stored in a mechanical winding switching device 8. The rotating electric machine 1 of this embodiment applies rotational torque to the wheels during power running, and applies braking torque during regeneration.

[0015] The phase current detection circuit 2 is composed of a Hall CT (Current Transformer) and the like, and detects any two of the three-phase AC currents of phases U, V, and W. It is configured to calculate the other phase on the assumption that the three-phase AC currents are in a balanced state, but it may also be configured to detect all three phases.

[0016] The inverter 3 includes a DC voltage power supply 5 such as a battery, a gate driver 6, and a switching element S up ~S wn and a main circuit section 7 including diodes D1 to D6. Note that the effects of this embodiment are not limited by the type of switching element.

[0017] The controller 4 is made up of an inverter control device 9 that controls the inverter 3, a winding switching control device 10 that controls the mechanical winding switching device 8, and a mechanical brake control device 11 that controls the mechanical brakes that brake the wheels. The controller 4 controls the inverter 3, the mechanical winding switching device 8, and the mechanical brake 16 based on vehicle signals (not shown) (for example, accelerator signals, brake signals, etc.) to drive the electric vehicle as desired by the driver.

[0018] The inverter control device 9 detects the current i flowing through the U-phase wire 1U, the V-phase wire 1V, and the W-phase wire 1W of the rotating electric machine 1, which is obtained from the phase current detection circuit 2. u , i v , i w Using the rotation speed of the rotating electric machine 1 obtained from the rotation speed detector 17 , an applied voltage command pulse for setting the rotation of the rotating electric machine 1 to a predetermined state is generated and output to the gate driver 6 .

[0019] Furthermore, the inverter control device 9 uses the rotational speed of the rotating electric machine 1 obtained from the rotational speed detector 17 to determine whether or not the rotational speed has reached a predetermined rotational speed threshold. If it determines that the rotational speed threshold has been reached, the inverter control device 9 outputs an inverter-off command to the gate driver 6 to turn off all switching elements of the inverter 3, and outputs a winding switching command to the winding switching control device 10. The inverter control device 9 also determines whether or not the rotating electric machine 1 is in a regenerative state. If the inverter control device 9 determines that the rotational speed of the rotating electric machine 1 has reached the predetermined rotational speed threshold and that the rotating electric machine 1 is in a regenerative state, it outputs a brake torque loss compensation command to the mechanical brake control device 11.

[0020] When the winding switching control device 10 receives a winding switching command output from the inverter control device 9, it generates a winding switching signal and outputs it to the mechanical winding switching device 8.

[0021] The mechanical winding switching device 8 has a circuit configuration capable of switching the connection state of the rotating electric machine 1, and switches the connection state of the rotating electric machine 1 based on a signal from the winding switching control device .

[0022] The mechanical brake control device 11 controls a mechanical brake 16 in accordance with the depression force of a brake pedal (not shown). The mechanical brake 16 generates a brake torque by friction force. There are various types of mechanical brakes 16, such as a disc brake and a drum brake, but the effects of this embodiment are not limited by the type of mechanical brake.

[0023] Next, the configuration of the mechanical winding switching device 8 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a diagram showing the winding configuration of a rotating electric machine according to a first embodiment of the present invention. Fig. 3A is a diagram showing a state in which windings of each phase of the rotating electric machine according to a first embodiment of the present invention are connected in series. Fig. 3B is a diagram showing a state in which windings of each phase of the rotating electric machine according to a first embodiment of the present invention are connected in parallel. Note that while a configuration in which the connection state is switched between series connection and parallel connection is shown here, this is merely an example, and a configuration in which the connection state is switched between Y connection and Δ connection, or a configuration in which the number of turns of the windings is switched, may also be used.

[0024] As shown in Fig. 2, two windings 1A and 1B are provided for each of the U, V, and W phases of the rotating electrical machine 1. Also, a switch SW 1U , S.W. 1V , S.W. 1W and switch SW 2U , S.W. 2V , S.W. 2W These switches are turned on and off by a mechanical winding switching device 8.

[0025] In the rotating electric machine 1, a switch SW 1U , S.W. 1V , S.W. 1W are turned on, and the switch SW 2U , S.W. 2V , S.W. 2W By turning off the switches SW1, SW2, and SW3, the two windings 1A, 1B in each of the U, V, and W phases can be connected in series as shown in FIG. 1U , S.W. 1V , S.W. 1W are turned off, and the switch SW 2U , S.W. 2V , S.W. 2W By turning on each of these, the two windings 1A, 1B of each of the U, V, and W phases can be connected in parallel as shown in Fig. 3B. In this way, it is possible to switch the connection state of the rotating electric machine 1 from a series connection to a parallel connection, or from a parallel connection to a series connection.

[0026] Next, the relationship between the rotation speed and the regenerative braking torque, and the relationship between the rotation speed and the wiring state will be described. Fig. 4A is a diagram showing the relationship between the rotation speed and the regenerative braking torque. Fig. 4B is a diagram showing the relationship between the rotation speed and the wiring state.

[0027] In FIG. 4A, from time t0 to time t1, the inverter operates to generate regenerative braking torque and output the required braking torque. The vehicle then obtains the required braking torque and decelerates. The inverter is stopped from time t1 to time t2, which is the winding switching period. This causes the regenerative braking torque to disappear, making it impossible to output the required braking torque and making it difficult for the vehicle to decelerate. This difficulty in deceleration can lead to collisions, which increases the safety risk. Furthermore, if winding switching is prohibited during regeneration to solve this problem, it becomes possible to output the required braking torque, but another problem arises.

[0028] This problem will be explained using FIG. 4B . First, assume that the operating point is at OPP. At this time, the rotational speed of the rotating electric machine 1 is in the high-speed rotation range, and therefore the rotating electric machine 1 is in a wiring state suitable for the high-speed rotation range. Next, assume that the rotating electric machine 1 decelerates as in operation OP1 and falls below the rotational speed threshold. At this time, winding switching is prohibited to solve the above-mentioned problem. Next, assume that the driver depresses the accelerator pedal before the rotational speed reaches 0 as in operation OP2, and the operating point moves to OPP' in the powering range. At this time, because winding switching was prohibited in operation OP1, the rotating electric machine 1 is in a wiring state suitable for the high-speed rotation range, even though the rotational speed is in the low-speed rotation range. This makes it impossible to achieve the original purpose of applying a winding switching device, such as obtaining high torque and a good acceleration rate in the low-speed rotation range.

[0029] As described above, the configurations shown in FIGS. 4A and 4B have the problem that they cannot both output the required brake torque during the winding switching period during regeneration and drive in a suitable connection state in the low speed range.

[0030] Means for solving this problem will be described with reference to Figures 5 and 6. Figure 5 is a flowchart showing a winding switching sequence according to the first embodiment of the present invention.

[0031] In FIG. 5, when the winding switching sequence starts, the inverter control device 9 uses the rotation speed of the rotating electrical machine 1 obtained from the rotation speed detector 17 to determine whether or not the rotation speed has reached a rotation speed threshold value (step S1).

[0032] If it is determined in step S1 that the rotation speed threshold has been reached (YES in step S1), the inverter control device 9 generates an inverter-off command to turn off all switching elements of the inverter 3 and outputs this to the gate driver 6 (step S2).If it is determined in step S1 that the rotation speed threshold has not been reached (NO in step S1), the inverter control device 9 repeats the processing of step S1.

[0033] Next, the inverter control device 9 determines whether the rotary electric machine 1 is in a regenerative state (step S3).

[0034] When it is determined in step S3 that the rotating electric machine 1 is in a regenerative state (YES in step S3), the inverter control device 9 outputs a brake torque loss compensation command to the mechanical brake control device 11. The mechanical brake control device 11 controls the mechanical brake 16 to compensate for the loss of regenerative brake torque of the rotating electric machine 1 and to match the required brake torque (step S4).

[0035] Also, if it is determined in step S3 that the vehicle is not in a regenerative state (NO in step S3), the process proceeds to step S5 without passing through step S4 since no regenerative brake torque is being generated.

[0036] Next, the inverter control device 9 outputs a winding switching command to the winding switching control device 10. After receiving the winding switching command, the winding switching control device 10 generates a winding switching signal and outputs it to the mechanical winding switching device 8 (step S5). As a result, the mechanical winding switching device 8 switches the connection state of the rotating electric machine 1.

[0037] Next, the inverter control device 9 executes control to restart the current supply from the inverter 3 to the rotary electric machine 1 (step S6), and ends the winding switching sequence.

[0038] As described above, in the first embodiment, in the winding switching sequence, the inverter control device 9 determines whether the rotating electric machine 1 is in a regenerative state, and if it determines that it is in a regenerative state, the inverter control device 9 outputs a brake torque loss compensation command to the mechanical brake control device 11, and the mechanical brake control device 11 causes the mechanical brake 16 to compensate for the loss of regenerative brake torque of the rotating electric machine 1, and controls the mechanical brake 16 so that the brake torque matches the required brake torque.

[0039] An example of distribution of mechanical brake torque and regenerative brake torque will be described below. Fig. 6 is a diagram showing the relationship between rotation speed, mechanical brake torque, and regenerative brake torque according to the first embodiment of the present invention.

[0040] Upon receiving the deceleration request, the inverter control device 9 and the mechanical brake control device 11 respectively control the regenerative brake torque and the mechanical brake torque so as to satisfy the required brake torque. That is, the inverter control device 9 and the mechanical brake control device 11 control so that the sum of the regenerative brake torque and the mechanical brake torque becomes the required brake torque.

[0041] Between time t0 and time t1, the inverter control device 9 and the mechanical brake control device 11 distribute the brake torque so that the regenerative brake torque is greater than the mechanical brake torque, and output the required brake torque.

[0042] During the winding switching period from t1 to t2, the inverter control device 9 turns off all switching elements of the inverter 3, so that the regenerative braking torque becomes zero. The mechanical brake control device 11 increases the mechanical braking torque to compensate for the loss of the regenerative braking torque, and controls the mechanical braking torque alone to satisfy the required braking torque.

[0043] After t3, which is after the winding switching period ends, the mechanical brake torque and the regenerative brake torque are distributed in the same manner as between time t0 and time t1.

[0044] By controlling in this manner, in the first embodiment, it is possible to output the required brake torque even during the winding switching period during regeneration, and it is also possible to drive in a suitable connection state in the low rotation speed range by switching the winding. Note that the distribution of mechanical brake torque and regenerative brake torque outside the winding switching period in Figure 6, i.e., from time t0 to time t1 and after time t2, is merely an example, and changes in this distribution do not affect the effects of the first embodiment. For example, it is also possible to set the mechanical brake torque to zero from time t0 to time t1 and after time t2, and satisfy the required brake torque with only the regenerative brake torque.

[0045] According to the first embodiment, it is possible to output the required brake torque even during the winding switching period during regeneration, and also to drive in a suitable connection state even in the low speed rotation range. [Example]

[0046] A second embodiment of the present invention will be described with reference to Figures 7 to 9. Figure 7 is a flowchart showing a winding switching sequence according to the second embodiment of the present invention.

[0047] Differences from the first embodiment will be described with reference to Fig. 7. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0048] As shown in FIG. 7, the winding switching sequence of the second embodiment includes step S7 between step S4 and step S5.

[0049] The process proceeds to step S7 after the process of step S4 is completed or if the determination in step S3 is NO.

[0050] In step S7, the inverter control device 9 turns off all the switching elements of the inverter 3, and then starts a predetermined period T A As an example, it is determined whether a predetermined period T A is the period until the transient current due to the winding inductance of the rotating electric machine 1 becomes approximately zero when the maximum current that can flow when the rotating electric machine 1 is energized, and can be calculated in advance analytically or experimentally.

[0051] In step S7, a predetermined period T A If it is determined that the predetermined period T has elapsed (YES in step S7), the process proceeds to step S5, and the connection state is switched. A If it is determined that the time has not elapsed (NO in step S7), the operation of step S7 is repeated.

[0052] In the circuit that constitutes the inverter, even when all the switching elements of the inverter 3 are turned off, a transient current still flows immediately after that.

[0053] Fig. 8A is a diagram showing an example of a current flow when the switching elements of the inverter 3 are operating. Fig. 8B is a diagram showing an example of a transient current flow immediately after the switching elements of the inverter 3 are turned off.

[0054] In FIG. 8A , a current path is formed in which current flows from inverter 3 through U-phase wire 1U, through the windings of rotating electric machine 1, and then through V-phase wire 1V and back to inverter 3. If all switching elements of inverter 3 are turned off while current is flowing, the winding inductance of rotating electric machine 1 causes a transient current to flow from inverter 3 to U-phase wire 1U, through the windings of rotating electric machine 1, and from V-phase wire 1V to inverter 3, as shown in FIG. 8B . Therefore, if winding switching is performed while such a transient current is flowing, arc discharge may occur at the contact points between the stator electrode and the mover electrode of the winding switching device, potentially causing problems such as welding. For ease of explanation, FIGS. 8A and 8B depict the rotating electric machine 1 as being connected in series. However, the possibility of such problems occurring exists regardless of the wiring state of rotating electric machine 1. Also, components not necessary for explanation are omitted from FIGS. 8A and 8B as appropriate.

[0055] Next, the effect of the second embodiment will be described with reference to Fig. 9. Fig. 9 is a schematic diagram showing the attenuation of the transient current immediately after the switching elements of the inverter according to the second embodiment of the present invention are turned off.

[0056] 9 shows a schematic representation of a phase current flowing in one of the U, V, and W phases of the rotating electric machine 1. In FIG. 9, the period from time t0 to time t1 is a period during which the rotating electric machine 1 is energized, and at time t1, all switching elements of the inverter 3 are turned off. The transient current due to the winding inductance of the rotating electric machine 1 refers to the current that flows after time t1 in FIG. 9. Note that the effect of the second embodiment is not related to the direction in which the phase current flows, and therefore the vertical axis in FIG. 9 represents the absolute value of the phase current.

[0057] In the second embodiment, the transient current shown in FIG. 9 is maintained for a predetermined period T A The connection state is switched after a predetermined period T A is the period until the transient current becomes approximately zero when the maximum current is flowing. Therefore, regardless of the current flowing from time t0 to time t1, the predetermined period T A After that time, the transient current always becomes approximately zero.

[0058] According to the second embodiment, arc discharge due to transient current can be prevented, and therefore the life of the winding switching device can be extended. [Example]

[0059] A third embodiment of the present invention will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a flowchart showing a winding switching sequence according to the third embodiment of the present invention. The following description will focus on differences from the first and second embodiments. Configurations common to the first and second embodiments will be given the same reference numerals, and detailed description thereof will be omitted.

[0060] 10, the winding switching sequence of the third embodiment includes steps S8 and S9. The process proceeds to step S8 after the process of step S4 is completed. The process proceeds to step S9 if the determination in step S3 is NO.

[0061] In step S8, the inverter control device 9 turns off all the switching elements of the inverter 3, and then starts a predetermined period T A-R As an example, it is determined whether a predetermined period T A-R The predetermined time period T may be calculated analytically or experimentally in advance as the time period until the transient current becomes approximately zero when the maximum current flows through the rotating electrical machine 1 during regeneration. A-R If it is determined that the predetermined period T has elapsed (YES), the process proceeds to step S5. A-R If it is determined that the time has not elapsed (NO), the process of step S8 is repeated.

[0062] In step S9, the inverter control device 9 turns off all the switching elements of the inverter 3, and then starts a predetermined period T A-P As an example, it is determined whether a predetermined period T A-PThe predetermined time period T may be calculated analytically or experimentally in advance as the time period until the transient current becomes approximately zero when the maximum current that can flow through the rotating electrical machine 1 is flowing. A-P If it is determined that the predetermined period T has elapsed (YES), the process proceeds to step S5. A-P If it is determined that the time has not elapsed (NO), the process of step S9 is repeated.

[0063] 11 is a schematic diagram showing the attenuation of a transient current immediately after the switching elements of the inverter according to the third embodiment of the present invention are turned off. In FIG. 11, the phase current flowing through one of the U-phase, V-phase, and W-phase of the rotating electric machine 1 is depicted separately during power running and during regeneration.

[0064] In Fig. 11, the period from time t0 to time t1 is the period during which the rotating electric machine 1 is energized, and all switching elements of the inverter 3 are turned off at time t1. The transient current due to the winding inductance of the rotating electric machine 1 refers to the current that flows after time t1 in Fig. 11. Note that the effect of the third embodiment is not related to the direction in which the phase current flows, and therefore the vertical axis in Fig. 11 represents the absolute value of the phase current.

[0065] The absolute value of the regenerative braking torque of the rotating electric machine 1 is less than the maximum torque during power running due to the presence of the braking torque of the mechanical brake 16. In other words, the maximum current that flows when the rotating electric machine 1 is regenerating is less than the maximum current that can flow through the rotating electric machine 1. Therefore, as shown in FIG. 11, the period until the transient current becomes approximately zero during regeneration is shortened, and therefore, the predetermined period T during regeneration is A-R is the specified period T during powering A-P can be set shorter than

[0066] The winding switching period consists of a period for waiting for a predetermined period to elapse and a period for the winding switching device to switch the connection state, and the winding switching period can be shortened by shortening the predetermined period. In other words, the period for which the mechanical brake 16 compensates for the loss of regenerative braking torque of the rotating electric machine 1 can be shortened.

[0067] According to the third embodiment, it is possible to extend the life of the winding switching device and reduce wear on the brake pads. [Example]

[0068] A fourth embodiment of the present invention will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a block diagram showing the configuration of an electric vehicle drive system according to the fourth embodiment of the present invention. Fig. 13 is a diagram showing brake torque distribution in a comparative example and in the fourth embodiment. Differences from the first to third embodiments will be mainly described below. Components common to the first to third embodiments will be assigned the same reference numerals, and detailed description thereof will be omitted.

[0069] As shown in FIG. 12, the inverter control device 9 has a brake torque distribution device 18 that distributes the regenerative brake torque and the mechanical brake torque based on the rotation speed of the rotary electric machine 1.

[0070] The brake torque distribution device 18 outputs a brake torque distribution command to the inverter control device 9 and the mechanical brake control device 11 using the rotational speed of the rotating electric machine 1 obtained by the rotational speed detector 17. Specifically, as shown in Fig. 13, it controls so that the sum of the regenerative brake torque of the rotating electric machine 1 and the mechanical brake torque of the mechanical brake 16 matches the required brake torque, and also controls so that as the rotational speed of the rotating electric machine 1 approaches the rotational speed threshold, the ratio of the brake torque output by the mechanical brake 16 to the total brake torque becomes larger than the ratio of the regenerative brake torque output by the rotating electric machine 1. Then, when the rotational speed of the rotating electric machine 1 reaches the rotational speed threshold, the brake torque distribution device 18 controls so that only the mechanical brake 16 operates.

[0071] Next, the effect of the fourth embodiment will be described with reference to Fig. 13. Generally, the response of a mechanical brake is slower than that of a regenerative brake. Therefore, as shown in the comparative example of Fig. 13(a), a time lag occurs before the loss of regenerative braking is compensated for, which may cause fluctuations in brake torque and result in a deterioration in ride comfort. To prevent this fluctuation in brake torque, a mechanical brake with a fast response is required, which leads to higher costs.

[0072] Therefore, in the fourth embodiment, the brake torque of the mechanical brake is increased in advance before the winding switching is performed so that it matches the required brake torque, thereby preventing fluctuations in the brake torque as shown in Fig. 13(b).

[0073] According to the fourth embodiment, even when a low-cost, slow-response mechanical brake is used, the fluctuation of the brake torque can be suppressed, and the cost of the mechanical brake can be reduced. [Example]

[0074] A fifth embodiment of the present invention will be described with reference to Figs. 14 and 16. Fig. 14 is a flowchart showing a winding switching sequence according to the fifth embodiment of the present invention. Fig. 15 is a diagram showing the behavior of the stator electrodes and the mover electrodes of the mechanical winding switching device according to the fifth embodiment of the present invention. Differences from the first to fourth embodiments will be mainly described below. Configurations common to the first to fourth embodiments will be assigned the same reference numerals, and detailed description thereof will be omitted.

[0075] As shown in FIG. 14, the winding switching sequence of the fifth embodiment includes steps S10, S11, and S12.

[0076] The process proceeds to step S10 after step S2 is completed, to step S11 after step S4 is completed, and to step S12 if the determination in step S3 is NO.

[0077] An example of the mechanical winding switching device 8 is shown in Figure 15. The mover electrode 82 of the mechanical winding switching device 8 is made of a metal piece with spring properties, and the stator electrode 81 is made of metal. Both ends (ends 82a, 82b) of the mover electrode 82 are fixed to two separate mover electrode bases 83a, 83b, respectively, and as one or both of the mover electrode bases 83a, 83b slide, the mover electrode 82 deforms and the contact area changes. The winding switching control device 10 operates the mover electrode 82 starting from the timing when all switching elements of the inverter 3 are turned off, and controls the contact area between the stator electrode 81 and the mover electrode 82 of the mechanical winding switching device 8 to decrease (step S10).

[0078] In step S11, the inverter control device 9 turns off all the switching elements of the inverter 3, and then starts a predetermined period T A-R It is determined whether this predetermined period T A-R The setting method will be described later.

[0079] In step S11, a predetermined period T A-R If it is determined that the predetermined period T' has elapsed (YES), the process proceeds to step S5. A-R If it is determined that the time period has not elapsed (NO), the process of step S11 is repeated.

[0080] In step S12, the inverter control device 9 turns off all the switching elements of the inverter 3, and then starts a predetermined period T A-P It is determined whether this predetermined period T A-P In step S12, a predetermined period T A-P If it is determined that the predetermined period T' has elapsed (YES), the process proceeds to step S5. A-P If it is determined that the time period has not elapsed (NO), the process of step S12 is repeated.

[0081] As an example, a predetermined period T A-R' may be calculated analytically or experimentally in advance as the period until the transient current becomes approximately zero when the maximum current is flowing through the rotating electric machine 1 during regeneration in a state where the contact area between the stator electrode 81 and the movable electrode 82 of the winding switching device has become small.

[0082] Also, as an example, a predetermined period T A-P ' may be calculated analytically or experimentally in advance as the period until the transient current becomes approximately zero when the maximum current that can flow when the rotating electric machine 1 is energized is flowing in a state where the contact area between the stator electrode 81 and the movable electrode 82 of the winding switching device is small.

[0083] Next, the effect of the fifth embodiment will be described with reference to Fig. 16. Fig. 16A is a schematic diagram showing how a transient current decays immediately after the switching elements of the inverter are turned off during power running according to the fifth embodiment of the present invention. Fig. 16B is a schematic diagram showing how a transient current decays immediately after the switching elements of the inverter are turned off during regeneration according to the fifth embodiment of the present invention.

[0084] In the fifth embodiment, the contact area between the stator electrode 81 and the mover electrode 82 of the mechanical winding switching device 8 is reduced, which increases the resistance of the rotating electric machine 1 and shortens the time constant. Therefore, in the fifth embodiment, as shown in Figures 16A and 16B, the period until the transient current becomes approximately zero is shorter compared to when the contact area between the stator electrode 81 and the mover electrode 82 is not reduced, regardless of whether the motor is running or regenerating, and therefore the winding switching period can be shortened.

[0085] According to the fifth embodiment, the period until the transient current becomes substantially zero during regeneration is shortened, and the period during which the mechanical brake 16 compensates for the loss of regenerative brake torque of the rotary electric machine 1 can be shortened, thereby extending the life of the winding switching device and further reducing wear on the brake pads. Furthermore, according to the fifth embodiment, the period during which the torque due to winding switching becomes zero during power running can be shortened, enabling smooth acceleration. [Example]

[0086] A sixth embodiment of the present invention will be described with reference to FIG.

[0087] 17 is a block diagram showing the configuration of an electric vehicle drive system according to a sixth embodiment of the present invention. The following description will focus on differences from the first to fifth embodiments. Components common to the first to fifth embodiments are given the same reference numerals, and detailed description thereof will be omitted.

[0088] 17, the drive system for an electric vehicle includes at least two or more (plural) rotating electric machines 1, a phase current detection circuit 2, an inverter 3, a mechanical winding switching device 8, and a motor shaft 12. A controller 4 controls the at least two or more rotating electric machines 1 so that the winding switching periods of the respective rotating electric machines 1 are different from each other.

[0089] In Example 6, while one of at least two rotating electric machines 1 is switching windings, another rotating electric machine 1 is outputting regenerative braking torque, so the loss of regenerative braking torque of the rotating electric machine 1 that should be compensated for by the mechanical brake 16 is reduced.

[0090] According to the sixth embodiment, in addition to the effects of claims 1 to 5, wear of the brake pads can be further reduced. [Example]

[0091] Seventh embodiment of the present invention will be described with reference to Fig. 18. Fig. 18 is a block diagram showing the configuration of an electric vehicle drive system according to the seventh embodiment of the present invention. The seventh embodiment is an example in which the electric vehicle drive system according to any one of the first to sixth embodiments is applied to a four-wheel electric vehicle.

[0092] The electric vehicle is provided with four (plural) wheels 15 on the front, rear, left and right sides, and each wheel 15 is provided with a mechanical brake 16. The left and right wheels are connected via drive shafts 14. Either the front or rear drive shaft 14 (for example, the drive shaft connecting the left and right rear wheels) is provided with a differential device 13, and the driving force of the rotating electric machine 1 is transmitted to the left and right wheels 15 (rear wheels) via the motor shaft 12 and differential device 13.

[0093] The rotating electric machine 1 is provided with a mechanical winding switching device 8, and is supplied with power from a battery (see FIG. 1) via an inverter 3. A phase current detection circuit 2 is provided between the rotating electric machine 1 and the inverter. The inverter 3 and the rotating electric machine 1 are controlled by a controller 4.

[0094] Regarding the winding switching by the winding switching control device 10, the control of the regenerative braking torque by the inverter control device 9, and the control of the mechanical braking torque by the mechanical brake control device 11, any of the above-described first to sixth embodiments may be applied.

[0095] In the configuration of Example 7, winding switching, regenerative braking torque control, and mechanical braking torque control are performed on the rear wheels of the front and rear wheels 15, but the front wheels may be controlled instead of the rear wheels, or both the front and rear wheels may be controlled.

[0096] According to the seventh embodiment, it is possible to provide an electric vehicle that can output the required brake torque even during the winding switching period during regeneration and that can be driven in a suitable connection state even in the low speed rotation range. [Explanation of symbols]

[0097] 1...Rotating electric machine, 2...Phase current detection circuit, 3...Inverter, 4...Controller (control device), 5...DC voltage power supply, 6...Gate driver, 7...Main circuit section, 8...Mechanical winding switching device, 9...Inverter control device, 10...Winding switching control device, 11...Mechanical brake control device, 12...Motor shaft, 13...Differential device, 14...Drive shaft, 15...Wheel, 16...Mechanical brake, 17...Rotational speed detector, 18...Brake torque distribution device, 81...Stator electrode, 82...Mover electrode, 82a, 82b...End, 83a...Mover electrode base, 83b...Mover electrode base

Claims

1. A drive system for an electric vehicle includes a rotating electric machine that applies rotational torque to wheels during power running and applies braking torque during regeneration, an inverter that supplies power to the rotating electric machine, a mechanical winding switching device that switches a connection state of the rotating electric machine when the rotational speed of the rotating electric machine reaches a predetermined rotational speed threshold, and a control device that controls the rotating electric machine, the inverter, and the mechanical winding switching device, the control device includes an inverter control device that controls the inverter, a winding switching control device that controls the mechanical winding switching device, and a mechanical brake control device that controls a mechanical brake that brakes the wheels, the inverter control device controls all switching elements of the inverter to be turned off when switching the connection state of the rotating electric machine, and outputs a winding switching command to the winding switching control device after a predetermined period has elapsed from the timing at which all switching elements of the inverter are turned off; the winding switching control device outputs a winding switching signal to the mechanical winding switching device after receiving the winding switching command from the inverter control device; the mechanical brake control device controls the mechanical brake to compensate for a regenerative brake torque of the rotating electric machine that is lost when all switching elements of the inverter are turned off when the rotating electric machine is in a regenerative state; A drive system for an electric vehicle, characterized in that the predetermined period is set to be shorter during regeneration than during power running.

2. 2. The drive system for an electric vehicle according to claim 1, The mechanical brake control device controls the mechanical brake to compensate for the loss of regenerative braking torque of the rotating electric machine so that the required braking torque matches the mechanical brake torque.

3. 3. The drive system for an electric vehicle according to claim 2, the inverter control device includes a brake torque distribution device that distributes regenerative brake torque and mechanical brake torque based on the rotational speed of the rotating electric machine, The brake torque distribution device controls the ratio of mechanical brake torque to total brake torque so that it becomes greater than the ratio of regenerative brake torque as the rotational speed of the rotating electric machine approaches the rotational speed threshold.

4. 4. The drive system for an electric vehicle according to claim 3, A drive system for an electric vehicle, characterized in that the brake torque distribution device controls so that only the mechanical brake operates when the rotational speed of the rotating electric machine reaches the rotational speed threshold.

5. 2. The drive system for an electric vehicle according to claim 1, the mechanical winding switching device includes a stator electrode and a mover electrode that changes a contact area with the stator electrode; The winding switching control device controls the contact area between the stator electrode and the mover electrode to be small, starting from the timing when all switching elements of the inverter are turned off.

6. A drive system for an electric vehicle comprising: a rotating electric machine that applies rotational torque to a wheel during power running and applies braking torque during regeneration; an inverter that supplies power to the rotating electric machine; a mechanical winding switching device that switches the connection state of the rotating electric machine when the rotational speed of the rotating electric machine reaches a predetermined rotational speed threshold; and a control device that controls the rotating electric machine, the inverter, and the mechanical winding switching device, the control device includes an inverter control device that controls the inverter, a winding switching control device that controls the mechanical winding switching device, and a mechanical brake control device that controls a mechanical brake that brakes the wheels, the inverter control device controls all switching elements of the inverter to be turned off when switching the connection state of the rotating electric machine; the mechanical brake control device controls the mechanical brake to compensate for a regenerative brake torque of the rotating electric machine that is lost when all switching elements of the inverter are turned off when the rotating electric machine is in a regenerative state; the mechanical winding switching device includes a stator electrode and a mover electrode that changes a contact area with the stator electrode; The winding switching control device controls the contact area between the stator electrode and the mover electrode to be small, starting from the timing when all switching elements of the inverter are turned off.

7. In any one of claims 1 to 6, a plurality of the rotating electric machines, the inverters, and the mechanical winding switching devices are provided; The control device controls the mechanical winding switching device so as to make the winding switching periods of the plurality of rotating electric machines different from each other.

8. An electric vehicle equipped with the drive system for an electric vehicle according to any one of claims 1 to 6.

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