JPH04183204A - Driver for electric automobile - Google Patents

Abstract

PURPOSE:To reduce the weight of the driver by selecting a torque-slip curve for setting the torque of an induction motor, which drives right and left wheels individually with AC power obtained by inverting DC power, lower on the inner wheel side than on the outer wheel side thereby commanding a rotational speed and a voltage. CONSTITUTION:DC power of a battery 10 is inverted through an inverter 12 into AC power which is then fed to the stator 28 of an induction motor 14. A rotor 26 is divided coaxially into independently rotating squirrel-cage cores 26-R, L for rotating left and right wheels 22-L, R, rotational speeds n1, n2 of which are detected through tachometers 32-L, R. An ECU 16 takes in an accelerator opening theta, the rotational speeds n1, n2 and a steering angle delta and calculates a synchronous speed ns and a voltage V thus controlling the inverter 12. When deltanot equal to 0, one of a plurality of torque-slip curves stored in the ECU 16 is selected so that the rotary torque is lower on the inner wheel side than on the outer wheel side based on the difference between the rotational speed n1, n2 thus commanding a synchronous speed and a voltage. According to the constitution, differential gear can be eliminated resulting the weight reduction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention aims to reduce the weight of the device and ensure turning performance by changing the structure of the electric vehicle drive device, particularly the induction motor, and changing the control content. The present invention relates to a device that achieves this.

[Prior Art] An electric vehicle is a vehicle that is driven by electric power from a battery, and uses a motor as its power source. When an AC induction motor is used as the motor, an inverter is used that converts DC voltage from a battery into alternating AC voltage and supplies it to the induction motor tank.

FIG. 8 shows the configuration of a drive device for an electric vehicle according to a first conventional example. This conventional example is, for example, JP-A-63
The configuration is similar to that of the device disclosed in Japanese Patent No. -203430.

This conventional example includes a battery 10 such as a zinc bromine battery that outputs a predetermined DC voltage. Batch 1J10 is connected to a motor 14 which is a three-phase induction motor via an inverter 12.
The inverter 12 is connected to the ECU 16.

Inverter 12 converts the DC voltage output from battery 10 into three-phase voltage. The inverter 12 generally has switching elements corresponding to each phase of the motor 14, and the ECU 16 controls the frequency and effective voltage value of the AC voltage supplied to the motor 14 by turning on/off the switching elements. . The control of the ECU 16 is executed according to the opening degree of the accelerator and the brake pedal force operated by the driver. That is, the ECU 16 determines the rotation speed and torque of the motor 14 according to the accelerator and the brake, and issues a rotation speed command and a voltage command to the inverter 12 to control its operation in order to realize the determined rotation speed and torque.

Further, the motor 14 is connected to left and right wheels 22 via a reducer (R/G) 18 and a differential gear (diff) 20.
-R and 22-L. Therefore, when AC voltage is supplied from the inverter 12 to the motor 14 and the motor 14 rotates in response, this rotational force is applied to the wheels 22-R.
and 22-L, and the electric vehicle runs.

Here, the differential 20 is a device that absorbs the difference in rotation speed between the left and right wheels 22-R and 22-L when the electric vehicle is about to turn. - Boat fishing consists of a bevel gear and several operating small gears. This device ensures good sliding when the electric vehicle turns.

FIG. 9 shows the configuration of a drive device for an electric vehicle according to a second conventional example. The device shown in this figure has a similar configuration to the device disclosed in, for example, Japanese Patent Application Laid-Open No. 195033/1983.

This conventional example includes two systems of drive means that drive the left and right wheels 22-R and 22-L, respectively. That is, two inverters 12, two ECUs 16, and two motors 14, L and R, are provided corresponding to the left and right wheels 22-R and 22-ri.

In this conventional example, the left and right wheels 22-R and 22,L are driven by separate motors 14-L and 14-R, respectively. Moreover, the operation of motors 14-L and 14-R is as follows:
It is determined by the control operations of the ECUs 16-L and 16-R. Therefore, in this conventional example, even though the differential 20 is not used, it is possible to ensure good sliding movement when the electric vehicle turns. Furthermore, in order to reduce the size of the motor 14 compared to the first conventional example, the motor 14 is installed inside the wheel 22.
can be incorporated, increasing the degree of freedom in the layout of the interior of an electric vehicle.

[Problems to be Solved by the Invention] In the first conventional example described above, the differential 20 is used to ensure the turning performance of the electric vehicle.

However, this differential 20 uses many gears and is a member having a certain weight. The differential 20 has a weight of, for example, about 5 kg. Therefore, in the configuration of the first conventional example, the weight of the device increases.

Further, in the second conventional example, although the differential 20 does not increase the weight, the use of driving means, especially two inverters 12, may still cause an increase in weight. Specifically, compared to the inverter 12 of the first conventional example, the weight of the two inverters 12 of the second conventional example is about 1.5 times.

As described above, in the past, there was a problem in that the weight of the device increased in order to ensure good sliding during turning.

The present invention was made to solve these problems, and aims to reduce the weight of the device while ensuring turning performance.

[Means for Solving the Problem] In order to achieve such an object, the present invention provides an induction motor having at least two rotors that respectively apply torque to left and right wheels, and controlling an inverter. The control means selects the slip of each rotor so that the torque of the rotor related to the inner ring is smaller than the torque of the rotor related to the outer ring based on the rotation speed of each rotor when the electric vehicle turns. The present invention includes means for selecting a torque-slip curve based on the slip of each rotor and determining a synchronous speed and voltage value, and a means for issuing a rotation speed command and a voltage command based on the determined synchronous speed and voltage value. Features.

[Operation] In the present invention, the induction motor has at least two rotors. When AC voltage from the inverter is applied to the primary winding of the stator, each rotor rotates and torque is applied to the corresponding left and right wheels. When going straight,
The torque values to be applied to the left and right wheels are equal to each other, and the control means issues rotational speed and voltage commands to the inverter according to the required torque, so that the necessary driving force is delivered from the rotor of the induction motor to the left and right wheels. Supplied.

Further, in the present invention, when the electric vehicle turns, the slip is selected based on the rotation speed of each rotor of the induction motor. This selection is performed such that the rotor torque associated with the inner ring is smaller than the rotor torque associated with the outer ring.

That is, when the electric vehicle tries to turn, the rotation speed of the inner wheels becomes smaller than the rotation speed of the outer wheels. In the induction motor, the slip is small in the torque-slip curve, that is, the rotational speed is close to the synchronous speed (i.e., large),
It is driven in the region where torque increases monotonically with respect to slip. Therefore, the torque of the rotor associated with the outer ring, which has a high number of rotations, becomes smaller than that of the rotor associated with the inner ring, which has a lower number of rotations. Such torque provides a force that causes the electric vehicle to turn in the opposite direction to the direction in which it should turn, against the intention of the driver of the electric vehicle. In the present invention, in order to prevent the generation of such torque, slip is selected when turning, and the induction motor is driven in a region where the rotational speed is lower than that when traveling straight on the torque-slip curve.

Further, in the present invention, a torque-slip curve is selected while maintaining the slip selected as described above. Furthermore, synchronous speed and voltage values are determined based on the selected torque-slip curve, and a rotation speed command and voltage command are issued to the inverter based on these values.

Therefore, in the present invention, the drive control of both left and right wheels is performed by a single induction motor without using a differential, so that the weight of the device is reduced.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the same components as those of the conventional example shown in FIGS. 8 and 9 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows the configuration of an electric vehicle drive device according to a first embodiment of the present invention. This figure is a cross-sectional view schematically illustrating the structure of the motor 14 in this embodiment, and the configuration related to driving and controlling the motor 14 is added in blocks.

The motor 14 used in this embodiment has a structure having one stator and two rotors. That is, either the primary winding 28 or the stator 24 wound in the slot.
are arranged on the outer shell, and two rotors 26 are arranged in parallel inside. Each of the rotors 26-L and 26-R is a cage rotor, and is provided to be rotatable independently of each other via bearings.

Each rotor 26-L and 26-R has an output shaft 30
-L and 30-R. (2) The inner shafts 30-L and 30-R are connected to the left and right wheels 22-R and 22-R, respectively. Corresponding rotors 26-L and 26
The rotation of -R causes the left and right wheels 22-L and 22-R to rotate, thereby driving the electric vehicle.

Furthermore, in this embodiment, the rotors 26-
Rotation speed sensors 32-L and 32-R are provided to detect rotation speeds 01 and n2 of L and 26-R. The detected rotational speeds n and n2 are supplied to the ECU 16 along with the accelerator opening degree θ and the steering wheel turning angle δ. ECU1
6 issues a rotation speed command and a voltage command to the inverter 2 based on this information, and outputs a rotation speed command and a voltage command from the inverter 12 to the primary winding 2.
The excitation current and torque current supplied to 8 are controlled.

FIG. 2 shows the operation of this embodiment, particularly the flow of the operation of the ECUI 6.

In this embodiment, first, the accelerator opening degree θ, the steering wheel turning angle δ, the rotational speeds 01 and n2 are read (100). Next, the slip s1 voltage V and torque T are determined (102).

The slip voltage s1 and the torque T are determined by a map or calculation formula stored in the ECU 16. The relationships treated as maps or calculation formulas are, for example, the relationships illustrated in FIGS. 3 to 5 and expressed as the following formulas.

s=f (θ) V−h(n) T−g (S, V) That is, the slide S and the voltage V are approximately proportional to the accelerator opening θ and the rotation speed n, respectively.

Further, the torque T is determined by the slip S using the voltage ■ as a parameter. Torque T has a characteristic that has a peak with respect to slip S. In other words, on the slip-torque curve, the torque T monotonically increases in a region where the slip S is small, and monotonically decreases in a region where the slip S is large.

In step 102, the slip S is determined according to the accelerator opening degree θ read in step 102. Similarly, the voltage V is determined according to the average value of the rotational speeds n and n2 read in step 102.

This voltage V selects one of the full torque curves, and the determined full torque S determines the torque T on the selected full torque curve.

Next, the synchronous speed n is determined (104).

The synchronous speed n is the rotation speed when the slip S is 0.

Conversely, the suberi S is defined by the following equation.

S de(n - n)/n S S In step 104, a modified formula n
The average value of the rotational speeds n and n2 is substituted for the rotational speed n of -n/(1-s),
The synchronous speed n is determined.

The synchronous speed n and voltage V obtained in this way are:
When the electric vehicle tries to go straight, that is, rotor 2
When 6-L and 26-R are to be driven at the same rotational speed and torque (in the case of n rotational speeds), it can be used as a command value for the inverter 2 as is.

Therefore, after step 104, n 1 "" n 2
The determination 106 of whether n 1 ”” is executed.
(If it is 12, the rotation speed and voltage commands are issued based on the synchronous speed n and the voltage (108). As a result, drive control is performed according to the accelerator opening degree θ when traveling straight.

If it is determined in determination 106 that n 1 - n 2 is not the case, it can be considered that the electric vehicle is about to turn. However, in reality, potholes on the road surface,
Due to steps etc., nl-n2 may not be achieved even when turning. Therefore, in order to avoid misinterpreting such a state as turning, determination 110 is executed, and only when the steering wheel turning angle δ is not 0, the process moves to the next step 112. In other cases, the process moves to step 108.

In step 112, each rotor 26-L and 26-L
-R's suberi S and s2 are determined.

These slips sl and s2 are the same for each rotor 26-L and 26-L.
- It is calculated based on the rotation speed 01 and n2 of R. That is, s1-(ns-n1)/nsS2''
(n,'n2)/nS.

Furthermore, based on S and s2 and voltage V, torques T1 and T2 of each rotor 26-L and 26-R are determined (114). That is, T 1-g (S 1 ,
Torques T and T2 are determined as V) T2-g (s2.V) and are subjected to determination 116.

In determination 116, the average value of torques T and T2 is compared with the torque T determined in step 102 ≦ Here, the torque T determined in step 102 is determined when the electric vehicle is traveling straight. This is the torque that should be generated when fA. When the average values of torques T1 and T2 are equal to this, if the rotation speed and voltage command are given using the synchronous speed n and voltage V obtained in steps 102 and 104 or updated in step 118 described later, the This means that no turning force is generated in the opposite direction to the direction in which the vehicle should turn, and the same accelerator feeling as when driving straight ahead can be achieved. According to the characteristics of motor 4, the currently used torque is -
This means that it is possible to continue using the slip curve and maintain slip.

Therefore, if it is determined in determination 116 that the two are equal, the process moves to step 108 after determination 107, and the rotation speed and voltage commands based on the synchronous speed port and voltage V are issued. In other cases, the currently desired rotation speed (
Therefore, it is not possible to maintain the voltage (slip), and the voltage (
Therefore, it is not possible to maintain the torque-slip curve. Therefore, step 118 is executed.

First, in determination 117, it is determined whether one of the following conditions 1 and 2 is present.

Condition 1: δ〉O and T1〉T2 Condition 2: δ〉O〉T1〉T2 Here, if the value of the steering wheel turning angle δ is positive, it indicates a right turn, and if it is negative, it indicates a left turn. shall be.

In the determination 117, if either condition 1 or condition 2 is satisfied, the process moves to step 08. In other cases, that is, if it is determined that neither condition 1 nor condition 2 is satisfied, the process moves to step 118.

In step 118, the synchronous speed n and the voltage 2 are updated in predetermined steps. That is, n n ten Δ
As n S S S V ← - ΔV, the synchronous speed n increases (that is, the slip decreases), and the voltage ■ decreases (that is, the torque-slip curve decreases below the figure 5). ) is changed to the curve located at , and the operations from step 10 are repeated. Note that Δn and ΔV are set depending on the size of the electric vehicle and the motor 4, the calculation speed of the ECU 16, the required acceleration link, and the characteristics of the motor 4.

The meaning of such updating of the synchronous speed n and voltage (2) will be explained. FIG. 6 shows the turning operation of an electric vehicle equipped with the drive device according to this embodiment.

As shown in this figure, when the electric vehicle attempts to turn left, the left wheel 22-L, which is the inner wheel, has a lower rotation speed than the right wheel 22-R, which is the outer wheel. That is, in this embodiment, the rotor is 26-L.
Since two wheels, 22-L and 26-R, are provided, the left and right wheels 22-L and 22-R can be rotated independently, and as a result, when turning left,
The relationship n 1 < n 2 holds true.

Such a relationship provides the following relationship regarding torques T1 and T2 in normal operation.

T 1 > T 2 That is, the motor 14, which is an induction motor, is normally driven in a region of small slip, and in the second region, the torque increases monotonically with respect to slip. For example, as shown in Fig. 5, when an electric vehicle turns while driving normally with the voltage set to 1 or V,
The slips sl and s2 of each rotor 26-L and 26-R become sl' and S2-, and the corresponding torque T1
As clearly shown in the figure, the above-mentioned magnitude relationship holds true for - and T2-.

However, if such a relationship is allowed, it will not be possible to turn well. That is, the rotor 26 related to the inner ring
If the torque T1 of -L is greater than the torque T2 of the rotor 26-R related to the outer ring, a turning force will be generated in the opposite direction to the steering wheel operation, and the vehicle will not be able to turn properly.

Therefore, in this embodiment, the synchronous speed n and voltage V are updated in step 1]8 to prevent the torque of the rotor 26 related to the inner ring from becoming larger than the torque of the rotor 26 related to the outer ring. .

This update is an update in the direction of increasing the synchronous speed n. As described above, since the slip S is determined from the synchronous speed n 2 and the rotational speed n, an increase in the synchronous speed n 2 is a decrease in the slip S. In other words, in this embodiment, it can be said that by updating the synchronous speed n, the total S is updated to a larger value.

In FIG. 5, this updated setting is applied to each rotor 26-L and 26- on the torque-slip curve for the same voltage V.
This corresponds to moving the driving point of R to the left.

The torque-slip curve is a curve that has a peak regarding slip, and therefore, by repeating the above-described updating, the magnitude relationship between the torques T□ and T2 will be reversed at a certain point. That is, the rotors 26-L and 26-R related to the left and right wheels 22-L and 22-R are fully S
and s2 belong to the small slip region, then T1>T2
However, once the peak is exceeded, this relationship is reversed, and
T1 becomes T2. This relationship does not cause the problem that occurs when T1>T2 (when turning, a turning force may be generated that interferes with the /X steering operation). Therefore, by updating the slip in this manner, good turning performance can be ensured.

Also, the update of the voltage V means that the torque related to the lower voltage V -
This corresponds to selecting the perfect curve.

For example, this corresponds to a transition from a torque-slip curve related to the voltage V□ having the relationship v > ■ to a torque-slip curve related to the voltage V3.

The fact that this update is repeatedly executed means that the average value of the torques T and T2 related to the left and right rotors 26-L and 26-R during turning is the same as the value of torque T during normal operation (operation when traveling straight). This corresponds to matching. That is, the torque T when traveling straight determined in step 102
If this is not maintained, problems will occur such as the accelerator feeling changing between driving straight and turning. □ Therefore, in this embodiment, the voltage V is updated in step 118, and determination 1
At step 16, it is determined whether the average torque matches the torque T when traveling straight, and the rotation speed and voltage commands are executed according to the torque-slip curve when the match is realized.

Further, in this embodiment, a determination is made in step 117 if either condition 1 or condition 2 is satisfied. This determination 117 is performed in order to prevent problems caused by the average value of torques T1 and T2 coincidentally matching torque T, that is, the condition in determination 116 being satisfied.

For example, in this example, when the driver turns the steering wheel to the left, the initial rotational speed relationship is n 1 > n
It becomes 2.

Therefore, the flow of processing is as follows: Judgment 106 -> Judgment 110 - Step 112 -> Step 114 -> Judgment 116 At this time, if the condition of Judgment 116 is satisfied by chance,
Step 1 even though the outer ring has more torque
The operations after 18 will not be performed. In order to prevent these, a decision 117 is provided after the decision 116 to ensure that the relationship between the direction of the steering wheel turning angle δ and the torque match before step 108.

For example, in the case of a right turn, the torque T2 related to the inner wheel is adjusted to be smaller, and in the case of a left turn, the torque T2 related to the inner wheel is adjusted to be larger.

In this way, in this embodiment, the difference in rotational speed between the left and right wheels 22-L and 22-R is absorbed to achieve good sliding running without using a differential or using any other drive means. It becomes possible to do so. At this time, a turning force in the opposite direction to the steering wheel operation, that is, a movement that opposes the turning in the required direction, is not generated, and the weight of the electric vehicle is also reduced. Furthermore, there is no change in accelerator feeling between driving straight and turning.

Furthermore, the structure of the motor 14 in this embodiment (structure including two rotors 26) is effective when escaping from muddy ground. In an electric car equipped with a conventional differential, when only one wheel is caught in muddy ground and the vehicle is in a one-sided slip state, the wheel that is caught in the muddy ground only spins, and the wheel that is not caught in the muddy ground only spins. No torque is transmitted to the wheels. However, in this embodiment, torque can be transmitted to the wheels that are not caught in the mud by independent left and right drives, and escape from the mud can be made quickly and easily.

FIG. 7 shows the configuration of a drive device for an electric vehicle according to a second embodiment of the present invention. In this example,
The two rotors 26-L and 26-R are not arranged in parallel but concentrically.

If the motor 14 is driven by such a configuration and by a control operation similar to that shown in FIG. 2, the same effects as in the first embodiment can be obtained in this embodiment as well. However, in this embodiment, two rotors 26-t
, and 26-R do not have the same shape and dimensions, it is necessary to perform control while paying attention to the fact that their respective torque-slip curves are different.

[Effects of the Invention] As explained above, according to the present invention, since an induction motor having two rotors is used and is driven in a region with large slippage, the weight of the device can be reduced while maintaining turning performance. do. It also makes it easier to escape from muddy areas.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing the configuration of a drive device for an electric vehicle according to a first embodiment of the present invention, FIG. 2 is a flowchart showing the flow of operation of the ECU in this embodiment, and FIG. , a diagram showing the relationship between slip and accelerator opening in this example, Figure 4 is a diagram showing the relationship between voltage and rotational speed in this example, and Figure 5 is a diagram showing the relationship between motor torque and slip in this example. A diagram showing a curve, FIG. 6 is a diagram showing the relationship between the rotation speed and torque of the left and right rotors during turning in this embodiment, and FIG. 7 is a diagram showing the relationship between the rotation speed and torque of the left and right rotors during turning in this embodiment. FIG. 8 is a block diagram showing the configuration of the electric vehicle drive device according to the first conventional example; FIG. 9 is a schematic cross-sectional view showing the configuration of the device; FIG. 9 is the configuration of the electric vehicle drive device according to the second conventional example. FIG. 10...Battery 12...Inverter 14...Motor 16...ECU 22-L, 22-R...Wheel 24...Stator 26-L, 26-R...Rotor 28 ... Primary winding 32-L, 32-R... Rotation speed sensor n r 11
, n 2 ... Rotation speed θ ... Accelerator opening n -7・Synchronized speed V ... Voltage

Claims (1)

[Scope of Claims] A battery that outputs a predetermined DC voltage, an inverter that converts the DC voltage from the battery into an AC voltage of a predetermined number of phases and a predetermined value alternating at a predetermined frequency, and a stator that outputs the AC voltage from the inverter. An induction motor that rotates the rotor by applying it to the primary winding and generates driving torque for an electric vehicle, and an inverter that commands the rotation speed and voltage so that the torque is in a monotonically increasing range with respect to slip. A drive device for an electric vehicle, comprising: a control means for controlling torque of an induction motor; the induction motor has at least two rotors that apply torque to left and right wheels, respectively; means for selecting the slip of each rotor so that the torque of the rotor relating to the inner ring is smaller than the torque of the rotor relating to the outer ring based on the rotation speed of each rotor, and based on the selected slip of each rotor; A driving device for an electric vehicle, comprising: means for selecting a torque-slip curve and determining a synchronous speed and voltage value; and means for issuing a rotation speed command and a voltage command based on the determined synchronous speed and voltage value. .