Vibration control system for electric vehicles

Abstract

The present invention provides a vibration control device for electric vehicles that suppresses vibrations generated in a moving vehicle due to fluctuations in the drive frequency transmitted by the rotation of the propeller shaft. [Solution] The vibration control unit 29 of the electronic control device (vibration control device) 30 calculates a vibration damping rotational speed Npr or vibration damping torque Tpr that pulsates with opposite phase and amount to the rotational fluctuations of the propeller shaft 24. The vibration damping current signal that generates this vibration damping rotational speed Npr or vibration damping torque Tpr is superimposed on the drive current of the second electric motor MG2, thereby canceling out vibrations originating from the rotational fluctuations of the propeller shaft 24 and suppressing vibrations of the vehicle while it is running that originate from the rotational fluctuations of the propeller shaft 24.

Description

Technical Field

[0001] The present invention relates to a vibration control device for an electric vehicle that suppresses torque vibration caused by the intersection angle of a universal joint in a vehicle having a propeller shaft connected via the universal joint in a power transmission system.

Background Art

[0002] Patent Document 1 discloses that, in an electric vehicle provided with an electric motor capable of applying a vibration control torque to a drive shaft in order to suppress rotational fluctuations of a crankshaft due to in-cylinder pressure torque generated by combustion of an engine or inertial torque of a reciprocating mass, the vibration control torque is set so that the vibration control torque becomes minimum at the timing when pulsation of the in-cylinder pressure torque or the like becomes maximum.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, an electric vehicle is considered in which a propeller shaft having universal joints at both ends is connected between a drive unit composed of an engine and / or a first electric motor and a differential gear device having a second electric motor and distributing the driving force of the drive unit and / or the second electric motor to the left and right drive wheels. In such an electric vehicle, when the intersection angle of the universal joint becomes large, pulsation of the driving torque transmitted by the rotation of the propeller shaft occurs, causing a problem of generating vibrations of the vehicle during driving.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vibration control device for an electric vehicle that suppresses vibrations generated in a traveling vehicle due to fluctuations in the driving speed transmitted by the rotation of the propeller shaft. [Means for solving the problem]

[0006] The inventors have discovered that by detecting the rotational fluctuations and magnitude of the propeller shaft, and superimposing a vibration-damping torque that pulsates in the opposite phase to the rotational fluctuations onto the drive current of the second motor, vibrations of a vehicle running using the second motor can be effectively suppressed. This invention is based on this finding.

[0007] In other words, the gist of the present invention is a vibration control device for an electric vehicle in which a propeller shaft having universal joints at both ends is connected between (a) a drive unit consisting of an engine and / or a first electric motor and a differential gear device having a second electric motor that distributes the driving force of the drive unit and / or the second electric motor to the left and right drive wheels, the device comprising: (b) a rotation fluctuation detection unit that detects rotation fluctuations of the propeller shaft; (c) a vibration torque calculation unit that calculates a vibration damping rotation speed or vibration damping torque that pulsates in opposite phase to the rotation fluctuations of the propeller shaft; and (d) a vibration control unit that cancels out vibrations originating from rotation fluctuations of the propeller shaft by superimposing a vibration damping current signal that generates the vibration damping rotation speed or vibration damping torque calculated by the vibration torque calculation unit onto the drive current of the second electric motor. [Effects of the Invention]

[0008] In the vibration control device for electric vehicles of the present invention, a vibration damping rotational speed or vibration damping torque that pulsates in opposite phase to the rotational fluctuations of the propeller shaft is calculated, and a vibration damping current signal that generates this vibration damping rotational speed or vibration damping torque is superimposed on the drive current of the second electric motor, thereby canceling out vibrations originating from the rotational fluctuations of the propeller shaft, and thus suppressing vibrations of the vehicle while it is running that originate from the rotational fluctuations of the propeller shaft. [Brief explanation of the drawing]

[0009] [Figure 1]The diagrams illustrate the schematic configurations of the drive systems of electric vehicles to which the present invention is applied, wherein the vehicle in (a) comprises a drive unit consisting of an engine or a first electric motor and a transmission, a differential gear device having a second electric motor on the input shaft side of the differential mechanism, and a propeller shaft connecting the drive unit and the differential gear device via a universal joint; the vehicle in (b) comprises a drive unit having a power distribution mechanism having a first rotating element connected to the engine, a second rotating element and a third rotating element connected to the first electric motor, a differential gear device having a second electric motor on the input shaft side of the differential gear mechanism, and a propeller shaft connecting the drive unit and the differential gear device via a universal joint; and the vehicle in (c) has a differential gear device having a second electric motor on the side gear side of the differential gear mechanism. [Figure 2] Figure 1 is a flowchart illustrating the key aspects of the operation of the vibration control device for the electric vehicle. [Figure 3] Figure 2 is a flowchart illustrating the key components of another operational example of the vibration control device for the electric vehicle. [Figure 4] This is a flowchart illustrating the main parts of another operational example of the vibration control device for the electric vehicle shown in Figure 1 or Figure 2. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0011] Figure 1 is a diagram illustrating the schematic configuration of an electric vehicle to which the present invention is applied. In Figure 1, (a) shows an electric vehicle 10 and an electronic control device 30 to which the present invention is applied, (b) shows an electric vehicle 32 of a different example from electric vehicle 10, and (c) shows the main parts of other examples of electric vehicle 10 and electric vehicle 32. In (b) and (c), the same reference numerals are used for parts common to (a), and their description is omitted.

[0012] In Figure 1(a), the electric vehicle 10 comprises a drive unit 16 consisting of a drive source 12 which is an engine or a first electric motor MG1 and an automatic transmission 14; a differential gear device 20 having a second electric motor MG2 connected to the input shaft side of a differential gear mechanism, which distributes the driving force from the drive unit 16 to the left and right drive wheels 18 while allowing differential movement; a propeller shaft 24 connecting the drive unit 16 and the differential gear device 20 via a pair of universal joints 22; and a rotation sensor 25 that detects the rotational speed Np of the propeller shaft 24. The resolver of the second electric motor MG2 may be used instead of the rotation sensor 25.

[0013] The electric vehicle 10 is equipped with an electronic control device 30 that functions as a vibration control device, functionally comprising a drive control unit 26, a rotational fluctuation detection unit 27, a vibration damping torque calculation unit 28, and a vibration damping control unit 29, which are configured to control the driving of the electric vehicle 10, for example by including a microcomputer. The drive control unit 26 controls the engine or the first electric motor MG1 and the automatic transmission 14 so that the required drive torque calculated based on the accelerator opening θacc and the vehicle speed V is obtained with the best fuel efficiency. The rotational fluctuation detection unit 27 detects the rotational fluctuation of the propeller shaft 24 from its rotational speed Np. The vibration damping torque calculation unit 28 calculates a vibration damping rotational speed Npr or vibration damping torque Tpr that pulsates in opposite phase to the rotational fluctuation of the propeller shaft 24. The vibration control unit 29 suppresses vibrations of the vehicle during travel caused by rotational fluctuations of the propeller shaft 24 by superimposing a vibration damping current signal that generates a vibration damping rotational speed Npr or vibration damping torque Tpr that pulsates in opposite phase to the rotational fluctuations of the propeller shaft 24 onto the drive current of the second motor MG2.

[0014] In Figure 1(b), the electric vehicle 32 includes an engine 34 and a first electric motor MG1, a drive unit 38 having a power distribution mechanism 36 having a first rotating element RE1 connected to the engine 34, a second rotating element RE2 connected to the first electric motor MG1, and a third rotating element RE3, a differential gear device 20 having a second electric motor MG2 connected to the input shaft side of a differential gear mechanism, which distributes power from the drive unit 38 to the left and right drive wheels 18 while allowing differential action, and a propeller shaft 24 connecting the drive unit 38 and the differential gear device 20 via a pair of universal joints 22. The universal joints 22 provided at both ends of the propeller shaft 24 are also called, for example, Fuchs joints, universal joints, Cardan joints, or cross joints, and the rotational speed transmitted varies (pulsations) depending on the operating angle. Although not shown, the electric vehicle 32 is equipped with an electronic control device 30.

[0015] Figure 1(c) shows a differential gear set 40, which is a key component of another example of electric vehicles 10 and 32. Compared to the differential gear set 20, the differential gear set 40 has a pair of second motors MG2-1 and MG2-2 connected to a pair of side gears on the output side of the differential gear set, instead of the second motor MG2 connected to the input shaft side of the differential gear set.

[0016] The differential gear unit 20 and the differential gear unit 40 are well-known final reduction gears, and each comprises a reduction gear mechanism having a drive pinion and a ring gear, a differential case to which the ring gear is fixed, and a differential gear mechanism provided inside the differential case, meshing via the pinion and connected to the left and right drive wheels 18 via the drive shaft.

[0017] Figure 2 is a flowchart illustrating the main control operation corresponding to the vibration damping control unit 29 of the electronic control device 30 for electric vehicle 10 or electric vehicle 32 of the type in which the second electric motor MG2 of Figure 1(a) or (b) is connected to the input shaft side of the differential gear mechanism.

[0018] In step S1 of Figure 2 (the step will be omitted hereafter), it is determined whether or not there is output from the engine. If the determination in S1 is negative, then in S2, electric motor driving is performed using either the first electric motor MG1 or the second electric motor MG2. If the determination in S1 is positive, then in S3, it is determined whether or not there is output from the second electric motor MG2. If the determination in S3 is negative, then in S4, engine-driven driving is performed. If the determination in S3 is positive, then in S5, it is determined whether or not the steering angle θst of the steering wheel is less than or equal to a predetermined determination steering angle A(deg) of a few degrees or less for determining straight-line driving. If the judgment in S5 is denied, the vibration damping rotational speed Npr, Ndr or vibration damping torque Tpr, Tdr are not calculated in S6. However, if the judgment in S5 is affirmed, in S7, the rotational speed Np (rpm), including rotational fluctuations (advancement or lag in rotation) that occur while the propeller shaft 24 rotates 360° (one revolution), is calculated based on signals from the resolver of the second motor MG2 or from the left and right wheel speed sensors RH and LH, respectively, which are provided on the left and right drive wheels 18. Next, in S8, the advance / lag phase (pulsation) and the amount of advance / lag (amplitude) of the rotational speed Np of the propeller shaft 24 are calculated. In S9, the vibration damping rotational speed Npr, which is in the opposite phase and the opposite amount of advance / lag, is calculated from the advance / lag phase (pulsation) and the amount of advance / lag (amplitude) of the rotational speed Np of the propeller shaft 24. In S10, the vibration damping current representing the vibration damping rotational speed Npr is added to the drive current of the second motor MG2.

[0019] Next, in S11, in the speed reduction mechanism of the differential gear device 20, the rotational speed Nd (rpm) including the rotational fluctuation (advance and delay of meshing rotation) of the drive pinion of the differential gear device 20 that occurs while the drive pinion rotates 360° (one rotation) is calculated based on signals from the resolver of the second electric motor MG2 or the left and right wheel speed sensors RH and LH provided on the left and right drive wheels 18, respectively. Next, in S12, the advance and delay (pulsation) of the rotational speed Nd of the drive pinion and the amount of the advance and delay (amplitude) are calculated. In S13, from the advance and delay (pulsation) of the rotational speed Nd of the drive pinion and the amount of the advance and delay (amplitude), a vibration damping rotational speed Ndr representing a reverse phase to the advance and delay and an amount opposite to the amount of the advance and delay is calculated. In S14, a vibration damping current representing the vibration damping rotational speed Ndr is added to the drive current of the second electric motor MG2.

[0020] FIG. 3 is a flowchart for explaining the main part of the control operation corresponding to the vibration damping control unit 29 of the electronic control device 30 in the case where the electric vehicle 10 or the electric vehicle 32 shown in (a) or (b) of FIG. 1 is of a type including a differential gear device 40 in which a pair of second electric motors MG2-1 and MG2-2 shown in (c) of FIG. 1 are connected to a pair of side gears instead of the differential gear device 20. S1 to S9 in FIG. 3 are the same as those in FIG. 2. In S20 of FIG. 3, a vibration damping current representing the vibration damping rotational speed Npr is added to the drive currents of the second electric motors MG2-1 and MG2-2.

[0021] FIG. 4 is a flowchart for explaining the main part of the control operation corresponding to the vibration damping control unit 29 of the electronic control device 30 for the electric vehicle 10 or the electric vehicle 32 in which the second electric motor MG2 shown in (a) or (b) of FIG. 1 is connected to the input shaft side of the differential gear mechanism, and for the case where the electric vehicle 10 or the electric vehicle 32 is of a type including a differential gear device 40 in which a pair of second electric motors MG2-1 and MG2-2 shown in (c) of FIG. 1 are connected to a pair of side gears instead of the differential gear device 20.

[0022] Steps S1-S3 and S5-S6 in Figure 4 are the same as in Figure 2. In step S24 of Figure 4, the rotational speed Nd of the drive pinion is detected by the resolver of the second motor MG2 based on input from the deceleration surface (the surface that slides against the ring gear during deceleration) during deceleration. The lead / lag (pulsation) and the amount of lead / lag (amplitude) of the rotational speed Nd of the drive pinion are calculated, and a vibration damping rotational speed Ndr or vibration damping torque Tdr is calculated, which is in opposite phase to the lead / lag (pulsation) and inversely to the amount of lead / lag (amplitude). Next, in step S25, which is executed when the judgment in S5 is confirmed and the vehicle is in a straight-line driving state, a vibration damping current representing the vibration damping rotational speed Ndr or vibration damping torque Tdr is added to the drive current of the second motor MG2. In this embodiment, compared to Figure 3, the opposite phase and cancellation amount are calculated even when not in an accelerating state, and when the accelerating state is subsequently entered, the vibration damping rotation speed Ndr and vibration damping torque Tdr are added to the motor output, so that the lead / lag (pulsation) of the drive pinion rotation speed Nd and the amount of lead / lag (amplitude) can be canceled out more quickly.

[0023] As described above, in the vibration control unit 29 of the electronic control device (vibration control device) 30 of the electric vehicles 10 and 32 of this embodiment, a vibration damping rotational speed Npr or vibration damping torque Tpr that pulsates in opposite phase to the rotational fluctuations of the propeller shaft 24 is calculated, and a vibration damping current signal that generates this vibration damping rotational speed Npr or vibration damping torque Tpr is superimposed on the drive current of the second electric motor MG2, thereby canceling out vibrations originating from the rotational fluctuations of the propeller shaft 24 and suppressing vibrations of the vehicle while it is running that originate from the rotational fluctuations of the propeller shaft 24.

[0024] Although embodiments of the present invention have been described in detail above with reference to the drawings, these are merely examples, and the invention can be implemented in other forms as well.

[0025] For example, in the embodiments shown in Figures 2 and 3, similar to the embodiment in Figure 4, a vibration damping torque Tdr is calculated that is in the opposite phase to the lead / lag (pulsation) of the rotational speed Nd of the drive pinion and the amount of lead / lag (amplitude), and the amount of lead / lag is inversely opposite to the lead / lag amount (amplitude). The vibration damping current representing this vibration damping torque Tdr may be added to the drive current of the second motor MG2.

[0026] In the embodiments shown in Figures 2, 3, and 4 above, a vibration damping rotational speed Ndr was used, which is in opposite phase to the lead / lag (pulsation) of the drive pinion's rotational speed Nd and is also inversely proportional to the amount of lead / lag (amplitude). However, the vibration damping rotational speed Ndr does not necessarily have to be inversely proportional to the lead / lag (pulsation) of the drive pinion's rotational speed Nd; at least being in opposite phase will suffice to obtain a certain level of effectiveness.

[0027] Furthermore, the second motor MG2 does not necessarily have to be mounted coaxially with the drive pinion that constitutes the input side of the reduction mechanism of the differential gear unit 20. Also, the second motors MG2-1 and MG2-2 do not necessarily have to be mounted coaxially with the pair of side gears that constitute the output side of the differential gear mechanism of the differential gear unit 40.

[0028] It should be noted that the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms without departing from its spirit. [Explanation of symbols]

[0029] 10: Electric vehicle, 12: Drive source, 16: Drive unit, 18: Drive wheel, 20: Differential gear system, 22: Universal joint, 24: Propeller shaft, 27: Rotational fluctuation detection unit, 28: Vibration damping torque calculation unit, 29: Vibration damping control unit, 30: Electronic control unit (vibration damping control unit), 32: Electric vehicle, 34: Engine, 36: Power distribution mechanism, 38: Drive unit, 40: Differential gear system, MG1: First motor, MG2: Second motor, MG2-1: Second motor, MG2-2: Second motor, Npr: Vibration damping rotation speed, Tpr: Vibration damping torque

Claims

[Claim 1] A vibration control device for an electric vehicle, wherein a propeller shaft having universal joints at both ends is connected between a drive unit consisting of an engine and / or a first electric motor and a differential gear system having a second electric motor that distributes the driving force of the drive unit and / or the second electric motor to the left and right drive wheels, A rotational fluctuation detection unit for detecting rotational fluctuations of the propeller shaft, A vibration damping torque calculation unit calculates a vibration damping rotation speed or vibration damping torque that pulsates in opposite phase to the rotational fluctuations of the propeller shaft, The vibration control unit includes a vibration control signal that generates a vibration damping rotation speed or vibration damping torque calculated by the vibration damping torque calculation unit, which is superimposed on the drive current of the second motor to cancel out vibrations originating from rotational fluctuations of the propeller shaft. A vibration control device for electric vehicles characterized by the following features.

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