JP2009268337A - Driving force controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrict collision sound from being made in a transmission path of torque when torque transmitted from a driving force source to a tire is oscillated. <P>SOLUTION: When a vehicle is in charge of running, reference torque transmitted from a driving force source to a tire is found, and oscillation torque is found from the reference torque. A friction coefficient between tire and road surface is controlled by transmitting oscillation torque from the deriving force source to the tire in the driving force controller. A reducer is provided in the route from the driving force source to the tire of the front wheel and the rear wheel. The driving force controller includes: a determining means (step S4) for determining whether the oscillation torque, which is transmitted through the reducer to the tire of the front wheel and the rear wheel, goes back and forth by turns on the drive side and on the generation side; and a torque distribution ratio control means (step S5) for controlling a distribution ratio of request torque transmitted to the front wheel and request torque transmitted to the rear wheel so that the oscillation torque serves as one side of the drive and generation sides when it is determined that the oscillation torque goes back and forth by turns on the drive side and the generation side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force control device capable of adjusting a friction coefficient between a tire and a road surface by controlling torque transmitted from a driving force source of a vehicle to the tire.

  Generally, a driving force source is mounted on a vehicle, and torque of the driving force source is transmitted to a tire, so that a driving force is generated between the tire and a road surface. Here, even if the torque transmitted from the driving force source to the tire is the same and the rotation speed of the tire is the same, the driving force also changes when the friction coefficient changes between the tire and the road surface. Thus, the behavior of the vehicle changes depending on the coefficient of friction between the tire and the road surface. On the other hand, paying attention to the relationship between the friction coefficient between the tire and the road surface and the torque characteristics transmitted to the tire, the friction coefficient between the tire and the road surface is arbitrarily determined by vibrating the torque transmitted to the tire. A technique for controlling is described in Patent Document 1.

  In the vehicle control device described in Patent Document 1, an electric motor that drives each wheel of the vehicle is provided, and the electric motor is driven and driven according to a motor torque command value for obtaining a required driving torque. Be controlled. In normal control, the driving torque of each wheel or electric motor is detected, and feedback control is performed so that the detected driving torque becomes a motor torque command value. Further, in addition to the above-described normal control, it is described that a minute vibration is applied to the tire by superimposing a minute vibration signal on the drive signal of the electric motor to control the frictional force of the tire. For example, by controlling the amplitude, frequency, and phase of the minute vibrations of torque applied to the tire and arbitrarily adjusting the friction coefficient between the tire and the road surface, the running performance and behavior of the vehicle are stabilized. ing.

Republished patent WO02 / 000463

  By the way, a gear transmission device, a winding transmission device, a friction transmission device, a traction transmission device, and the like are provided in the power transmission path from the driving force source of the vehicle to the tire. Among these, the gear transmission device is a rotating element. Since there is no slippage between them, there is an advantage that power loss is small. However, in a vehicle in which a gear transmission is provided in the power transmission path from the electric motor to the tire, as described in Patent Document 1, control for giving a minute vibration to the torque transmitted from the electric motor to the tire is performed. When the torque of the electric motor is vibrated so as to alternate between the drive side and the regenerative side, there is a possibility that a tooth contact noise caused by backlash occurs at the meshing portion of the gears.

  The present invention has been made paying attention to the above technical problem, and when a torque transmitted from the driving force source to the tire is vibrated, a collision sound is generated in the power transmission path from the driving force source to the tire. It is an object of the present invention to provide a driving force control device that can suppress the above-described problem.

  In order to achieve the above object, the invention according to claim 1 is directed to a vehicle having a tire that contacts a road surface and a driving force source that generates torque transmitted to the tire. By obtaining a reference torque that is required to be transmitted to the tire, obtaining a vibration torque that alternately changes with the reference torque as a boundary, and transmitting the vibration torque from the driving force source to the tire, In the driving force control apparatus that controls a coefficient of friction with a road surface, a front wheel tire and a rear wheel tire to which torque is transmitted from the driving force source are provided, and the front wheel tire or the rear tire is provided from the driving force source. In the torque transmission path that reaches at least one of the tires of the wheel, a transmission device that performs torque transmission by engagement of the concave portion and the convex portion is provided, Determining means for determining whether or not the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately goes back and forth between the drive side and the regeneration side; When it is determined that the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately travels between the drive side and the regeneration side, The front wheel torque transmitted to the front wheel tire and the rear wheel transmitted to the rear wheel so that the vibration torque transmitted to the tire via the transmission device is one of the drive side and the regeneration side. And a torque distribution ratio calculating means for obtaining a distribution ratio with the service torque.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the present invention further comprises a change amount determining means for determining whether or not the change amount of the reference torque is less than a predetermined first predetermined value. The ratio calculating means determines that the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately goes back and forth between the drive side and the regeneration side, and Means for determining a distribution ratio between the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel when the change amount of the reference torque is less than a predetermined first predetermined value; , It is determined that the vibration torque transmitted to at least one of the front tire and the rear tire via the transmission device alternately moves between the drive side and the regeneration side, and the reference torque The amount of change is Means for prohibiting the determination of the distribution ratio between the front wheel torque transmitted to the front tire and the rear wheel torque transmitted to the rear wheel when the predetermined first predetermined value is exceeded; It is characterized by.

  According to a third aspect of the present invention, in addition to the configuration of the second aspect, the torque distribution ratio calculating means has an absolute value of a differential value of the reference torque exceeding a predetermined first predetermined value, and the Means for prohibiting the determination of the distribution ratio between the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel when the second-order differential value of the reference torque is equal to or less than a predetermined value; It is characterized by this.

  According to a fourth aspect of the invention, in addition to the configuration of the first aspect, the torque distribution ratio calculating means is configured so that the vibration torque on the driving side generated in either the front wheel or the rear wheel is away from zero Newton meter. In the course of changing, it includes means for distributing the vibration torque to the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel.

  According to a fifth aspect of the present invention, in addition to the configuration of the first aspect, the torque distribution ratio calculating means has a driving-side vibration torque generated in either the front wheel or the rear wheel larger than the reference torque. In addition, from the time when the difference between the reference torque and the vibration torque becomes maximum, the vibration torque is distributed to the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel. It is characterized by including a means.

  According to the first aspect of the present invention, the friction coefficient between the tire and the road surface is obtained by obtaining a reference torque transmitted from the driving force source to the tire and generating a vibration torque that alternately changes with the reference torque as a boundary. Can be controlled. In addition, when the vibration torque transmitted from the driving force source to the tire via the transmission device alternates between the drive side and the regeneration side, the vibration torque transmitted to the tire via the transmission device is The distribution ratio between the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel tire is controlled so as to be set to either the drive side or the regeneration side. Therefore, when vibration torque is transmitted via the transmission device, it is possible to suppress the occurrence of collision noise between the concave portion and the convex portion.

  According to the invention of claim 2, in addition to obtaining the same effect as that of the invention of claim 1, when the change amount of the reference torque is less than a predetermined first predetermined value, it is transmitted to the tire of the front wheel. A distribution ratio between the front wheel torque and the rear wheel torque transmitted to the rear wheel is obtained. On the other hand, when the change amount of the reference torque exceeds a predetermined first predetermined value, the distribution ratio between the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel. Is prohibited. Therefore, when it is predicted that the vehicle body vibrates in the vertical direction when vibration torque is transmitted to the tire, it is prohibited to transmit the vibration torque to the tire.

  According to the invention of claim 3, in addition to obtaining the same effect as that of the invention of claim 2, even when the change amount of the reference torque is relatively large, It is permitted to transmit vibration torque to the tire.

  According to the invention of claim 4, in addition to obtaining the same effect as that of the invention of claim 1, the vibration torque on the driving side generated in either the front wheel or the rear wheel changes in a direction away from zero Newton meter. In this process, it is also possible to distribute the vibration torque to the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel. Therefore, the required torque distributed to the other wheel is started from a relatively small value, and the impact caused by the engagement between the concave portion and the convex portion in the path where the torque is transmitted from the driving force source to the other wheel. Can be relatively reduced.

  According to the invention of claim 5, in addition to obtaining the same effect as that of the invention of claim 1, the driving-side vibration torque generated in either the front wheel or the rear wheel is greater than the reference torque, and From the time when the difference between the reference torque and the vibration torque becomes maximum, the vibration torque is distributed to the front wheel torque that is transmitted to the front wheel tire and the rear wheel torque that is transmitted to the rear wheel. Therefore, the required torque distributed to the other wheel starts from zero Newton meter, and the impact caused by the engagement between the concave and convex portions is minimized in the path where torque is transmitted from the driving force source to the other wheel. Limit.

  The driving force source in the present invention is a power generation device connected to a tire so as to be able to transmit power. Examples of the driving force source include an electric motor, an engine, and a hydraulic motor. The electric motor is a rotating device that converts electric energy into kinetic energy, and the torque of the electric motor can be controlled by controlling the current value of the electric power supplied to the electric motor. As the electric motor, a motor / generator having a function of converting kinetic energy into electric energy can be used. The engine is a power unit that converts thermal energy when fuel is burned into kinetic energy, and an internal combustion engine such as a gasoline engine, a diesel engine, or an LPG engine can be used as the engine. These engines can control the output torque by controlling the intake air amount and the fuel injection amount. Further, the gasoline engine and the LPG engine can control the output torque by controlling the ignition timing. The hydraulic motor is a fluid machine that converts the fluid energy of oil into the kinetic energy of the rotor, and a rotary hydraulic motor such as a gear motor, a vane motor, or a screw motor can be used as the hydraulic motor. In the hydraulic motor, the output torque of the rotor can be controlled by controlling the oil pressure of oil that gives kinetic energy to the rotor.

  In the transmission device according to the present invention, backlash, that is, a circumferential gap or play is inevitably formed between the concave portion and the convex portion. The transmission device according to the present invention includes a gear transmission that transmits torque by the meshing force between the gears. As a power transmission device using this gear transmission, a transmission that can change the ratio of the input rotation speed and the output rotation speed, a reduction gear that cannot change the ratio of the input rotation speed and the output rotation speed, A transfer that distributes power to the front and rear wheels, a differential that allows a difference in rotational speed between the left and right wheels, and the like are included. Examples of the transmission include a planetary gear type transmission, a selection gear type transmission, a constant mesh transmission, and the like. Further, the transmission device according to the present invention includes a spline coupling provided at a connection portion between the output shaft and the propulsion shaft of the transmission, that is, a mechanism for transmitting torque by meshing the inner teeth with the outer teeth. In the present invention, the drive side is a region that applies torque that promotes rotation of the tire, and the regeneration side is a region that applies torque (braking force) that inhibits rotation of the tire to the tire.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a plan view showing a schematic configuration of the vehicle 2. The vehicle 1 has four wheels, specifically, a right front wheel 2, a left front wheel 3, a right rear wheel 4, and a left rear wheel 5. Each wheel is configured by attaching a tire 7 to the wheel 6 and having an electric motor 8 disposed inside the wheel 6, that is, an in-wheel motor type wheel. The electric motor 8 is a motor generator that has both a power running (driving) function for converting electrical energy into kinetic energy and a regeneration function for converting kinetic energy into electrical energy. That is, the power running control is to operate the electric motor 8 as an electric motor, and the regeneration control is to operate the electric motor 8 as a generator. A speed reducer 9 is disposed in the power transmission path from the electric motor 8 to the wheel 6. The reduction gear 9 has a configuration in which the output rotation speed is lower than the input rotation speed. As the reduction gear 9, for example, a constantly meshing gear transmission mechanism can be used.

  As described above, the vehicle 1 shown in FIG. 2 is a four-wheel drive vehicle capable of independently controlling the torque transmitted to the tire 7 of each wheel. The electric motor 8, the speed reducer 9, and the wheels are supported by the vehicle body via a suspension device. This suspension device is a known device having a shock absorber, a spring and the like. Furthermore, a power source 13 is provided on the vehicle body. As the power source 13, a secondary battery that can be discharged and charged, for example, a battery or a capacitor can be used. Furthermore, in addition to the secondary battery, a fuel cell can also be used. The power source 13 and each electric motor 8 are connected by an electric circuit having an inverter (not shown).

  A braking device is provided for controlling the braking force applied to each wheel. The braking device includes a rotor that rotates integrally with the wheel 7, a disk caliper that sandwiches the rotor, a wheel cylinder 10 that operates the disk caliper, and an actuator 11 that controls the hydraulic pressure of the wheel cylinder 10. The wheel cylinder 10 is provided for each wheel, and the actuator 11 is provided on the vehicle body. Further, a steering device 12 is provided for controlling the steering angle of each wheel, particularly the front wheel. The steering device 12 has a known structure including a steering wheel provided in a room, a tie rod provided below the vehicle body, a gear box that converts a rotation operation of the steering wheel into an operating force of the tie rod, and the like. When the steering wheel of the steering device 12 is operated by the driver, the steering angle of the right front wheel 2 and the left front wheel 3 changes, and the steering angle of the right rear wheel 4 and the left rear wheel 5 changes. . That is, the vehicle 1 can control the steering angle of the four wheels. Further, an electronic control device 14 for controlling the braking device and the electric motor 8 is provided. The electronic control device 14 includes an accelerator pedal operation state, a brake pedal operation state, a steering angle of each wheel, and a center of gravity of the vehicle 1. Sensors and switch signals for detecting the surrounding yaw rate, vehicle speed, rotation speed of each wheel, rotation speed and torque of the electric motor 8, load supported by each wheel, stroke of the suspension device in each wheel, and the like are input. The electronic control device 14 outputs vibrations for controlling the rotation speed and torque of the electric motor 8, signals for controlling the hydraulic pressure of the wheel cylinder 10, and the like.

  The vehicle 1 shown in FIG. 2 includes an anti-lock brake system, a traction control system, and the like as functions for controlling running performance. These systems control the frictional force of the tire 7 so as to stabilize the vehicle body by maximizing the frictional force of the tire 7. For example, the cornering force is sufficiently large and the braking force is large. The target slip ratio is calculated, and the hydraulic control of the wheel cylinder 10 of the braking device, the rotational speed and torque of the electric motor 8 are controlled so that the actual slip ratio of the tire 7 approaches the target slip ratio. The steering performance, power performance, braking performance, turning performance, etc. of the vehicle 1 are to be ensured. In order to perform such control, the electronic control unit 14 stores a map and data representing the relationship between the slip ratio of the tire 7 and the friction coefficient between the tire 7 and the road surface. Based on this, the hydraulic pressure of the wheel cylinder 10 and the torque and rotation speed of the electric motor 8 are controlled.

On the other hand, the correspondence relationship between the slip ratio of the tire 7 and the friction coefficient between the tire 7 and the road surface varies depending on the road surface condition. It is also known that the friction coefficient between the tire 7 and the road surface can be arbitrarily adjusted by changing the torque transmitted to the tire 7, that is, by giving vibration to the torque. Specifically, when the torque of the electric motor 8 applied to the tire 7 is vibrated, the friction coefficient between the tire 7 and the road surface is arbitrarily adjusted by controlling the amplitude, frequency, phase, etc. of the vibration. It is known. This principle is described in the republished patent publication WO-02 / 000463. For example, a friction model using a rubber block instead of the tire 7 can be expressed by the following vibration equation (1).

In this vibration equation 1, Fn is a load in the vertical direction where the rubber block contacts the road surface, and μ · Fn is a frictional force (μ is a friction coefficient of the road surface) acting on the rubber block sliding in a certain direction. , M is the mass of the rubber block, k is the spring constant between the rubber block and the road surface, c is the damping coefficient of the rubber block, and ω0 is the resonance frequency of the rubber block. By solving this vibration equation 1, the ratio μre1 between the frictional force when not giving minute vibration to the rubber block and the frictional force when giving minute vibration to the rubber block is obtained by the following equation (2).

  From the above two formulas, it can be seen that the friction coefficient between the tire 7 and the road surface can be arbitrarily adjusted by applying a vibration torque in the front-rear direction of the tire 7 to be controlled, specifically in the rotational direction. The ratio μre1 depends on the frequency ω of the applied vibration torque, and the value of the ratio re1 tends to decrease as the frequency ω approaches the resonance frequency ω0. Further, the value of the ratio re1 can be relatively increased by applying a vibration torque having a frequency higher than the resonance frequency ω0 by frequency modulation. Further, by applying a vibration torque in the rotational direction of the tire 7, the relationship between the friction coefficient and the slip ratio in the front-rear direction of the tire 7 tends to increase as the slip ratio increases. This is known and is also described in the republished patent publication WO-02 / 000463.

  In this embodiment, in order to estimate whether or not the actual friction coefficient has reached the target friction coefficient, the electronic control unit 14 stores a map and data indicating the relationship between the slip ratio and the friction coefficient. And while estimating the slip ratio of the tire 7, an actual friction coefficient can be estimated from a map and data. Note that the slip ratio of each tire 7 can be estimated based on a signal from a sensor that detects the rotational speed of each wheel, and an estimation method thereof is disclosed in JP-A-2002-274356, JP-A-6-258196, and the like. Since it is well-known as described in the above, a detailed description is omitted. As described above, the friction coefficient in the front-rear direction between the tire and the road surface can be adjusted by vibrating the torque transmitted to the tire. In addition, when the case where vibration torque is applied to the tire is compared with the case where vibration torque is not applied, if the slip ratio in the front-rear direction is the same, the case where vibration torque is applied is compared to the case where vibration torque is not applied. Thus, it is known that the coefficient of friction in the front-rear direction of the tire is reduced. Also, comparing the case where vibration torque is applied to the tire and the case where vibration torque is not applied, if the slip ratio in the front-rear direction is the same, the case where vibration torque is applied to the tire is not applied It is known that the coefficient of friction in the left-right direction, that is, the width direction of the tire is larger than that of the tire. These principles are described in, for example, the republished patent publication WO-02 / 000463.

  By the way, in the power train of FIG. 2, a speed reducer 9 is arranged in a power transmission path from the electric motor 8 to the tire 7. The reduction gear 9 has a backlash formed at the meshing portion between the gears. For this reason, when the torque transmitted from the electric motor 8 to the tire 7 vibrates and the torque of the electric motor 8 moves back and forth between the drive side and the regeneration side, the teeth collide at the meshing portion of the gears. There was a possibility that an impact sound might be generated. Here, the drive side means that the electric motor 8 is power-running controlled, and the regeneration side means that the electric motor 8 is regeneratively controlled.

(First control example)
Therefore, in this embodiment, when vibration is applied to the torque transmitted from the electric motor 8 to the tire 7, in order to suppress the occurrence of an impact sound due to the collision between the teeth at the meshing portion of the gears, The flowchart of FIG. 1 is executed. The flowchart of FIG. 1 is an example in which the torque transmitted to the tire 7 is vibrated while the vehicle 1 is traveling. First, the required driving force is obtained using the vehicle speed and the accelerator opening as parameters, and the reference torque output from the electric motor 8 is obtained based on the required driving force (step S1). In order to perform the process of step S1, data and a map for obtaining the reference torque are stored in the electronic control unit 14. Further, since the vehicle 1 is a four-wheel drive vehicle, a reference torque is required for all the tires 7 for the front wheels and the rear wheels.

  Further, in this step S1, control for dividing the distribution ratio between the required torque for the front wheel transmitted to the tire 7 for the front wheel and the required torque for the rear wheel transmitted to the tire for the rear wheel, or the front wheel and the rear wheel It is possible to perform control to determine the distribution ratio between the required torque for the front wheel transmitted to the front tire 7 and the required torque for the rear wheel transmitted to the rear tire based on the distribution ratio of the support load between It is. Here, the following control will be described by taking as an example the case where the distribution ratio between the required torque for the front wheels transmitted to the front tire 7 and the required torque for the rear wheels transmitted to the rear tire 7 is equally divided. The reference torque is a required torque when the distribution ratio between the required torque for the front wheels transmitted to the tire 7 for the front wheels and the required torque for the rear wheels transmitted to the tires for the rear wheels is equally divided.

  Following this step S1, it is determined whether or not a condition for starting vibration of torque transmitted to each tire 7 is established (step S2). For example, in order to adjust the coefficient of friction between the tire 7 and the road surface, if a switch for selecting whether or not to start torque vibration is provided according to the driver's intention, based on the operation state of the switch The determination in step S2 can be made. If a negative determination is made in step S2, the process returns to the start without vibrating the torque transmitted to each tire 7.

  On the other hand, when a positive determination is made in step S2, the gain (amplitude) T of the vibration torque and the frequency F of the vibration torque are obtained for each tire 7 of each wheel based on the reference torque T0 (step S3). ). The processing in step S3 will be described with reference to the waveform diagram of FIG. FIG. 3 is a waveform diagram showing the relationship between the reference torque T0 and the vibration torque. In FIG. 3, the vertical axis is torque and the horizontal axis is time. As shown in FIG. 3, by adding a predetermined torque to the reference torque and subtracting the predetermined torque from the reference torque, a torque that fluctuates up and down around the reference torque, that is, a vibration torque is obtained. As described above, the vibration torque alternates between the phase higher than the reference torque and the phase lower than the reference torque at a predetermined cycle with the reference torque as a boundary. That is, the vibration torque changes alternately with the reference torque as a boundary. The reference torque T0 is represented by a difference from zero Nm, the difference (maximum difference) between the reference torque T0 and the vibration torque is a gain (amplitude) T, and the number of vibration cycles per unit time is a frequency.

This vibration period is the time from the reference torque as a starting point, which becomes higher than the reference torque, then becomes lower than the reference torque via the reference torque, and thereafter returns to the reference torque. In this embodiment, data and a map indicating the correspondence between the vehicle speed and the friction coefficient are stored in the electronic control unit 14, and the target friction coefficient is obtained from the vehicle speed. Next, a map and data in which the gain T and frequency are determined for each target friction coefficient are stored in the electronic control unit 14, and in step S3, the gain T and frequency are obtained using the map and data. . The vibration torque is obtained by the following equation.
Vibration torque = T0 + Tsinωt
Here, ω is the angular velocity of the tire, and t is time.

  Following this step S3, when vibration torque is generated by each electric motor 8, it is determined whether or not tooth contact occurs at the meshing portion of the gears constituting each reduction gear 9 (step S4). An example of the determination in step S4 will be described with reference to the waveform diagrams of FIGS. 4 and 5, the vertical axis represents torque, and the horizontal axis represents time. The waveform diagram of FIG. 4 is an example in which the reference torque T0 is set on the drive side for all four wheels. As shown in the waveform diagram of FIG. 4, when the vibration torque obtained from the reference torque T0 alternately moves between the drive side and the regenerative side, the tooth contact is made at the meshing portion of the gears constituting each reduction gear 9. Therefore, a positive determination is made in step S4. On the other hand, the waveform diagram of FIG. 5 is an example in which the reference torque T0 is set on the regeneration side for all four wheels. As shown in the waveform diagram of FIG. 5, when the vibration torque obtained from the reference torque T0 alternates between the drive side and the regeneration side, the tooth contact occurs at the meshing portion of the gears constituting each reduction gear 9. Therefore, a positive determination is made in step S4.

When the determination in step S4 is affirmative in this way, the distribution ratio between the required torque transmitted to the front tire 7 and the required torque transmitted to the rear tire 7 is changed (step S5) to start. Return. The processing in step S5 will be described with reference to the waveform diagrams in FIGS. 6 and 7, the vertical axis is torque, and the horizontal axis is time. FIG. 6 shows an example in which the torque distribution ratio is changed when the reference torque is on the drive side as shown in FIG. In FIG. 6, the front wheel required torque is set on the drive side, and the rear wheel required torque is set on the regeneration side. Further, the vibration torque corresponding to the front wheel required torque is set on the driving side, and the vibration torque corresponding to the rear wheel required torque is set on the regeneration side. For example,
Required torque for front wheels = T + 2T0
Required torque for rear wheel = T
Is set to

FIG. 7 is an example of changing the torque distribution ratio when the reference torque is on the regeneration side as shown in FIG. In FIG. 7, the front wheel required torque is set on the drive side, and the rear wheel required torque is set on the regeneration side. Further, the vibration torque corresponding to the front wheel required torque is set on the driving side, and the vibration torque corresponding to the rear wheel required torque is set on the regeneration side. For example,
Required torque for front wheels = T
Required torque for rear wheel =-(T-2T0)
Is set to

  As described above, the required torque for the front wheels and the required torque for the rear wheels are set to be equal in step S1, but are not uniform in step S5. It should be noted that the front wheel required torque and the rear wheel required torque are determined so that the driving force of the vehicle 1 as a whole is the same in step S1 and step S5. On the other hand, if all the reference torques of the four wheels are on the drive side and the vibration torque is on the drive side at the time of determination in step S4, a negative determination is made in step S4 and the process returns to the start. Further, when all the reference torques of the four wheels are on the regeneration side and the vibration torque is on the regeneration side at the time of determination in step S4, the determination is negative in step S4 and the process returns to the start. That is, when a negative determination is made in step S4, the vibration torque obtained in step S3 is transmitted to each tire 7.

  If the control of FIG. 1 is performed as described above, it is possible to suppress the occurrence of rattling noise in the speed reducer 9 when the vibration torque is output from the electric motor 8 in order to adjust the friction coefficient of each tire 7. . Moreover, although each reference torque calculated | required by step S1 and each request | requirement torque calculated | required by step S5 differ, since the vibration gain used by step S3 and the vibration gain used by step S5 are the same, the time of step S3 The traveling characteristics of the vehicle required in the above are ensured. In addition, as shown in the waveform diagram of FIG. 6, the rear wheel electric motor 8 is set by making the minimum portion of the absolute value of the vibration torque of the rear wheels as close as possible to zero Nm or set to zero Nm. Energy loss due to regeneration can be minimized. On the other hand, as shown in the waveform diagram of FIG. 7, by setting the minimum portion of the absolute value of the vibration torque of the front wheels as close to zero Nm as possible or setting it to zero Nm, Energy loss due to regeneration can be minimized.

  Next, an example in which part of the control in FIG. 1 is changed will be described. For example, as shown in the waveform diagram of FIG. 4, when the reference torque T0 is on the driving side and the vibration torque is straddling the driving side and the regeneration side, an affirmative determination is made in step S4. The rear wheel required torque is set on the drive side, the vibration torque is set only on the drive side, the front wheel required torque is set on the regeneration side, and the vibration torque is set only on the regeneration side. As described above, it is also possible to change the distribution ratio between the required torque for the front wheels and the required torque for the rear wheels.

  Further, as shown in the waveform diagram of FIG. 5, when the reference torque T0 is on the regeneration side and the vibration torque is straddling the drive side and the regeneration side, an affirmative determination is made in step S4. The rear wheel required torque is set on the drive side, the vibration torque is set only on the drive side, the front wheel required torque is set on the regeneration side, and the vibration torque is set only on the regeneration side. As described above, it is also possible to change the distribution ratio between the required torque for the front wheels and the required torque for the rear wheels.

  Further, in the power train shown in FIG. 2, the speed reducer 9 is provided on both the power transmission path from the electric motor 8 to the front wheels and the power transmission path from the electric motor 8 to the rear wheels. Alternatively, if any one of the rear wheels is not provided with a transmission that generates tooth contact, even if the vibration torque straddles the drive side and the regeneration side, tooth contact does not occur. For this reason, when changing the distribution ratio between the required torque for the front wheels and the required torque for the rear wheels in step S5, the vibration torque is straddled across the regeneration side and the drive side in a wheel that is not provided with a transmission that generates tooth contact. It is also possible to use a torque distribution ratio. Further, the control shown in FIG. 1 can be executed in a four-wheel drive vehicle having a configuration in which the torque of the electric motor mounted on the vehicle body is transmitted to both the front wheels and the rear wheels via the transmission.

  This first control example corresponds to claim 1, and the correspondence between the functional means shown in FIG. 1 and the configuration of the present invention will be described. Step S4 is the determination means of the present invention. Correspondingly, step S5 corresponds to the torque distribution ratio calculating means of the present invention. Further, the correspondence between the configuration shown in FIG. 2 and the configuration of the present invention will be described. The tire 7 corresponds to the tire of the present invention, the electric motor 8 corresponds to the driving force source of the present invention, The reduction gear 9 corresponds to the transmission device of the present invention.

(Second control example)
Next, a second control example that can be executed by the vehicle of FIG. 2 will be described. This second control example corresponds to claims 2 and 3. An example of the change in the reference torque is shown in FIG. In FIG. 8, the reference torque decreases on the drive side after time t1, and the reference torque is switched from the drive side to the regeneration side after time t3. Thereafter, the reference torque increases on the regeneration side, and further, the reference torque decreases on the regeneration side after time t5. Next, the basic torque is switched from the regeneration side to the drive side, and after time t6, the reference torque decreases again on the drive side. First, the change in the required torque for front wheels between time t1 and time t5 will be described with reference to the time chart of FIG. As shown in FIG. 8, the reference torque T0 is equal to or greater than T from time t1 to time t2, and the vibration torque obtained from the reference torque T0 is on the drive side and does not cross zero Nm. like,
Required torque for front wheels> T
It has become. Further, since the reference torque is reduced on the drive side as shown in FIG. 8, the front wheel required torque shown in FIG. 9 is also reduced on the drive side.

As shown in FIG. 8, when the reference torque T0 is less than T and exceeds zero Nm after time t2, the vibration torque obtained from the reference torque T0 crosses zero Nm. As shown in FIG. 9, the distribution ratio between the required torque for the vehicle and the required torque for the rear wheel is changed.
Required torque for front wheels = T + 2T0
Is raised to. Thereafter, since the reference torque T0 shown in FIG. 8 decreases on the driving side, the front wheel required torque shown in FIG. 9 also decreases on the driving side. Then, as shown in FIG. 8, when the reference torque T0 is switched from the drive side to the regeneration side at time t3 as shown in FIG. 8, in order to prevent the vibration torque from crossing zero Nm, as shown in FIG.
Required torque for front wheels = T
Fixed to. Further, as shown in FIG. 8, the reference torque T0 increases on the regeneration side, and after time t4, the reference torque T0 becomes -T or more, and even if the vibration torque is obtained from the reference torque T0, it exceeds zero Nm. Therefore, as shown in FIG. 9, the reference torque T0 is the required torque for the front wheels after time t4.

Thus, when the amount of change in the reference torque T0 is relatively large, as shown in FIG.
Required torque for front wheels = T
To front wheel required torque = -T
May change rapidly. In this way, when the required torque for the front wheels changes abruptly, the torque fluctuation is transmitted to the vehicle body via the suspension device, and the vehicle body vibrates in the vertical direction, so that the occupant may feel uncomfortable.

  In order to prevent such a problem, in the second control example, conditions for prohibiting transmission of vibration torque to the tire and conditions for permitting are defined. More specifically, the second control example is a subroutine that specifically provides conditions for prohibiting and permitting the first control example, and the second control example will be described with reference to the flowchart of FIG. When the flowchart of FIG. 10 is started, it is first determined whether or not there is a request to transmit vibration torque to the tire (step S2). The determination in step S2 is the same as the determination in step S2 in FIG. If a negative determination is made in step S2, the process returns to the start. On the other hand, when a positive determination is made in step S2, it is determined whether or not the reference torque T0 shown in FIG. 8 is less than T and exceeds zero Nm on the drive side. (Step S11).

If the determination in step S11 is affirmative, it is determined whether or not the absolute value T0 ′ of the differential value of the reference torque is less than a predetermined first predetermined value (threshold value) α (step S12). . This step S12 is a step of determining whether or not the amount of change in the reference torque is relatively small. If the determination in step S12 is affirmative, there is no possibility of the above-described problem occurring, so the processing described based on FIG. 6 is performed (step S13), and the process returns to the start. That is, in step S13,
Required torque for front wheels = T + 2T0
Required torque for rear wheel = -T
Gain = T
As a result, the vibration torque of each tire 7 is obtained.

  On the other hand, when a negative determination is made in step S12, that is, when the amount of change in the reference torque T0 is relatively large, a second-order (twice) differential value T0 ″ of the reference torque is determined in advance. 2. It is determined whether or not a predetermined value (threshold value) β is exceeded (step S14), where the gradient of the change amount of the reference torque is going to be relatively gentle or the current state is maintained. Further, it is a step of determining whether or not it is going to be relatively abrupt.Affirmative determination in step S14 means that the gradient of change in the reference torque is becoming relatively gentle (rounding). Therefore, if the determination in step S14 is affirmative, the process proceeds to step S13, whereas if the determination in step S14 is negative, the reference is made. Since the change gradient of the torque is assumed to be maintained or to be abrupt, control for transmitting the vibration torque to the tire 7 is prohibited (step S15), and the process returns to the start, that is, the process proceeds to step S15. In this case, the control described with reference to FIG. 6 is prohibited.

If a negative determination is made in step S11, it is determined in FIG. 8 whether or not the reference torque T0 is between zero Nm and -T on the regeneration side (step S16). The negative determination in step S16 is, for example, the reference torque T0 from time t4 to time t5 in FIG. 8, and even if the vibration torque is obtained based on the reference torque, the vibration torque is zero Nm. Since it doesn't straddle, return to the start. On the other hand, if an affirmative determination is made in step S16, it is determined whether or not the absolute value T0 ′ of the differential value of the reference torque is less than a predetermined first predetermined value (threshold value) α. (Step S17). The meaning of the determination in step S17 is the same as that in step S12, and the determination in step S17 is performed on the regeneration side. If the determination in step S17 is affirmative, the amount of change in the reference torque is relatively small, so the control described with reference to FIG. 7 is executed to transmit the vibration torque to the tire (step S18), and start. Return to. That is, in step S18,
Required torque for front wheels = T
Required torque for rear wheel =-(T-2T0)
Gain = T
As a result, the vibration torque of each tire 7 is obtained.

  On the other hand, the negative determination in step S17 means that the second-order differential value T0 ″ of the reference torque is a predetermined second predetermined value (threshold value) − because the reference torque change amount is relatively large. It is determined whether or not it is less than β (step S 19) Affirmative determination in step S 19 means that the change gradient of the reference torque is becoming relatively gentle (becomes rounded). Therefore, if a positive determination is made in step S19, the process proceeds to step S18, whereas if a negative determination is made in step S19, the reference torque change gradient becomes steeper, Alternatively, since the current state is considered to be maintained, the process proceeds to step S15, that is, when the process proceeds from step S19 to step S15, the control described with reference to FIG.

  Here, the relationship between the time chart of FIG. 8 and the flowchart of FIG. 10 will be described. On the way from point A to point B in FIG. 8, a positive determination is made in step S11. Further, the process proceeds from step B to point C in the routine of steps S12, S14, and S15. On the other hand, at point D in FIG. 8, since the amount of change in the reference torque is relatively large, a negative determination is made in step S12, and the application of vibration torque to the tire is prohibited. After that, since the gradient of the reference torque becomes gentle, for example, in the region E, the process proceeds from step S19 to step S18. That is, the control to give the vibration torque to the tire is permitted, more specifically, is resumed. In the process where the reference torque changes from the regeneration side to the drive side, the amount of change is abrupt and more abrupt, and in the process where the reference torque changes from the regeneration side to the drive side, An example of a case where the amount of change is abrupt and the gradient becomes gentle thereafter (starts to round) is not particularly explained, but the basic principle is that the reference torque changes from the drive side to the regeneration side Is the same.

  In the second control example, the first predetermined value α is a threshold value for determining whether or not the change amount of the reference torque is relatively small. On the other hand, the second predetermined value β is a threshold value for determining whether the change gradient of the reference torque is going to be gentle, more abrupt, or the current state is maintained. That is, the first predetermined value α and the second predetermined value β are technically different and have no relative magnitude relationship. Note that the predetermined value used in each determination step of FIG. 10 is obtained in advance by experiment or simulation and stored in the electronic control unit 14.

  As described above, in the second control example, it is determined whether to prohibit or permit the control of transmitting the vibration torque to the tire based on whether the change amount of the reference torque is relatively large or small. . More specifically, it is determined whether the gradient of change in the reference torque is going to be gentle, more abrupt, or the current situation is maintained, and the vibration torque is calculated based on the determination result. It is judged whether the control to be transmitted to the tire is prohibited or permitted. Therefore, according to the second control example, when vibration torque is transmitted to the tire, it can be avoided that the vehicle body vibrates via the suspension device and the passenger feels uncomfortable. Here, the correspondence between the functional means shown in FIG. 10 and the configuration of the present invention will be described. Steps S12 and S16 correspond to change amount determining means of the present invention, and steps S13, S14, S15, S17, S18, and S19 correspond to the torque distribution ratio calculation means of the present invention.

(Third control example)
Next, another control example that can be performed in step S5 in the flowchart of FIG. 1 described in the first control example will be described. For example, as shown in FIG. 11, the vibration torque on the driving side is applied to the front wheels and the vibration torque is not applied to the rear wheels (zero [Nm]), and the vibration torque approaches the zero Newton meter or When it is close to zero Newton meter, it is determined in step S4 of FIG. 1 that tooth contact occurs. In step S5, the vibration torque applied to the front wheel is increased on the driving side, and the vibration torque on the regeneration side is increased on the rear wheel. Is assumed to be given. When such control is performed, at the meshing portion between the gears of the reduction gear 8 for the rear wheel, when the regeneration side vibration torque is applied to the rear wheel, the tooth surface of the driving side gear is shifted to the driven side. Vibration is generated by colliding with the tooth surface. At this time, considering the acceleration of the tooth surface of the gear on the driving side, the vibration caused by the collision between the gears is
T / I = d (dθ / dt) dt
Can be obtained as Here, T is a torque applied to the gear, I is a gear inertia moment, and θ is a rotation angle of the gear. The acceleration is determined by the magnitude of the absolute value of the vibration torque X (Nm) on the regeneration side. That is, as the magnitude of the absolute value of the vibration torque X [Nm] on the regeneration side becomes relatively large, the acceleration becomes relatively large and the vibration due to the collision between the gears becomes relatively large.

  In the third control example, the distribution ratio of the torque transmitted to the front wheels and the rear wheels is changed, and a vibration torque exceeding zero Nm is applied to a wheel that has not been given a vibration torque, and is connected to the wheel. This is done for the purpose of preventing the gears of the transmission from colliding with each other. This third control example will be described based on the flowchart of FIG. Here, for the sake of convenience, an example will be described in which the reference torque is set on the drive side of the front wheels and the torque of the rear wheels is set to zero [Nm]. First, the determination in step S2 is made. The determination in step S2 is the same as the determination in step S2 in FIG.

  If a negative determination is made in step S2, the process returns. If a positive determination is made in step S2, it is determined whether or not the reference torque T0 decreasing on the drive side has become less than a predetermined value T2. (Step S21). Here, the predetermined value T2 is a value of the driving side torque, is the same magnitude as the gain T described in FIGS. 3 and 4, and is a value based on zero [Nm]. As described above, since the vibration torque changes alternately with the reference torque as a boundary, when the reference torque becomes less than the predetermined value T2 having the same magnitude as the gain T of the vibration torque, the vibration torque is zero [Nm Since it can be predicted that the following will occur, the predetermined value T2 is used for the determination in step S21.

  If a negative determination is made in step S21, the process returns because the vibration torque transmitted to the front wheels is generated only on the drive side. On the other hand, if the determination in step S21 is affirmative, if vibration torque is applied to the front wheels as they are, the vibration torque alternately moves between the drive side and the regeneration side, and the reduction gear connected to the front wheels. There is a possibility that a collision will occur at the meshing portion of the gears. Therefore, it is determined whether or not the vibration torque (T0 + Tsinωt) exceeds zero [Nm] on the drive side (step S22). If the determination in step S22 is affirmative, control is performed to distribute the vibration torque to the required torque transmitted to the front tire and the required torque transmitted to the rear tire at a predetermined timing (step S23). ), Return. In step S23, the torque distribution ratio is determined so that the vibration torque of the front wheels is generated only on the drive side and the vibration torque of the rear wheels is generated only on the regeneration side. Further, the required torque for the front wheels transmitted to the front wheels and the required torque for the rear wheels transmitted to the rear wheels so that the vibration torque of the rear wheels gradually increases toward the regeneration side starting from zero [Nm]. The timing for starting the distribution is determined.

  The process of step S23 will be described more specifically. As described above, when the regenerative torque is applied with an absolute value exceeding zero [Nm] at the start of transmitting the regenerative side torque to the rear wheels, the meshing portion of the gears of the speed reducer 9 connected to the rear wheels A collision occurs. For example, as shown in FIG. 13, when the reference torque T0 applied to the front wheels is gradually decreasing on the drive side, the vibration torque applied to the front wheels is larger than the reference torque, and the vibration torque is When the control for distributing the reference torque T0 to the required torque for the front wheels and the required torque for the rear wheels is started as shown in FIG. 14 from time t1 when the sum of the reference torque T0 and the gain T coincides, Is generated on the regeneration side starting from zero [Nm].

  Here, when the vibration torque applied to the front wheels coincides with the sum of the reference torque T0 and the gain T, the vibration torque of the front wheels is maximum in one vibration cycle (sinωT = 1) as shown in FIG. This is the moment. In other words, it is the moment when the difference between the vibration torque and the reference torque becomes maximum in one vibration cycle. As described above, when the timing for starting the distribution of the required torque for the front wheels transmitted to the front wheels and the required torque for the rear wheels transmitted to the rear wheels is determined, the gear on the driving side of the reduction gear of the rear wheels is The acceleration that collides with this gear becomes zero [rad / s2]. Therefore, even if the tooth surfaces of the gear collide with each other due to the backlash formed on the gear, the vibration can be minimized. In step S23, control for distributing the vibration torque to the front wheel required torque and the rear wheel required torque can be started in the process of changing the vibration torque in a direction away from zero Newton meter. In this case, the regenerative torque generated at the rear wheel can be relatively reduced.

  On the other hand, when a negative determination is made in step S22, a process of setting the vibration torque (output torque) to zero “Nm” is performed (step S24), and the process of step S24 is performed in the time charts of FIGS. In the range where the calculated vibration torque is less than zero [Nm] as shown by a broken line as shown in FIG. 15, the vibration torque actually output is zero [Nm as shown by a broken line in FIG. Following this step S24, it is determined whether or not the vibration torque exceeds zero [Nm] on the drive side (step S25), and if a positive determination is made in step S25, step S25 is performed. If the determination in step S25 is negative, the process returns to step S24, where the functional means shown in the flowchart of FIG. When the correspondence relationship with the configuration is described, Step S21, Step S22, and Step S23 correspond to the torque distribution ratio calculation means of Claims 4 and 5. The predetermined value T2 described in Step S22 is Claim 4. In the third control example, when vibration torque is applied to the rear wheel and vibration torque is not applied to the front wheel, the process proceeds to step S23 to distribute the vibration torque to the front wheel and the rear wheel. It can also be applied to control.

It is a flowchart which shows the 1st example of control which can be performed with the driving force control apparatus of this invention. It is a conceptual diagram of the vehicle used as the object of the driving force control apparatus of this invention. It is a wave form diagram which shows the vibration torque transmitted to a tire by this invention. It is a wave form diagram which shows the example of a vibration torque when a reference torque exists in a drive side by this invention. It is a wave form diagram which shows the example of a vibration torque when a reference torque exists in the regeneration side by this invention. FIG. 5 is a waveform diagram illustrating an example in which a required torque and a vibration torque are changed based on the waveform diagram of FIG. 4. FIG. 6 is a waveform diagram illustrating an example of changing a required torque and a vibration torque based on the waveform diagram of FIG. 5. It is a time chart which shows the example of a time-dependent change of the reference torque transmitted to the tire of a vehicle. It is a time chart which shows the example of a time-dependent change of required torque for front wheels. It is a flowchart which shows the 2nd example of control which can be performed with the driving force control apparatus of this invention. It is a 1st time chart which shows the vibration torque before performing the 3rd control example. It is a flowchart which shows the 3rd control example. It is a 2nd time chart which shows the vibration torque equivalent to the 3rd control example. It is the 3rd time chart which shows the vibration torque which corresponds to the 3rd control example. It is a 4th time chart which shows the vibration torque equivalent to the 3rd control example. It is a 5th time chart which shows the vibration torque equivalent to the 3rd control example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 7 ... Tire, 8 ... Electric motor, 9 ... Reduction gear, 14 ... Electronic control unit.

Claims (5)

When a vehicle having a tire in contact with a road surface and a driving force source that generates torque to be transmitted to the tire travels, a reference torque that is required to be transmitted from the driving force source to the tire is obtained. In a driving force control device for controlling a friction coefficient between the tire and a road surface by obtaining a vibration torque that alternately changes with a reference torque as a boundary, and transmitting the vibration torque from the driving force source to the tire.
A front wheel tire and a rear wheel tire to which torque is transmitted from the driving force source are provided, and a recess is provided in a torque transmission path from the driving force source to at least one of the front wheel tire and the rear wheel tire. A transmission device that transmits torque by meshing with the convex portion is provided,
Determining means for determining whether or not the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately goes back and forth between the drive side and the regeneration side;
When it is determined that the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately travels between the drive side and the regeneration side, The front wheel torque transmitted to the front wheel tire and the rear wheel transmitted to the rear wheel so that the vibration torque transmitted to the tire via the transmission device is one of the drive side and the regeneration side. A driving force control device comprising: a torque distribution ratio calculating means for determining a distribution ratio with the use torque. A change amount judging means for judging whether or not the change amount of the reference torque is less than a predetermined first predetermined value;
The torque distribution ratio calculating means includes
It is determined that the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately moves between the drive side and the regeneration side, and the change in the reference torque Means for determining a distribution ratio between the front wheel torque transmitted to the front wheel tire and the rear wheel torque transmitted to the rear wheel when the amount is less than a predetermined first predetermined value;
It is determined that the vibration torque transmitted to at least one of the front wheel tire or the rear wheel tire via the transmission device alternately moves between the drive side and the regeneration side, and the change in the reference torque Means for prohibiting obtaining a distribution ratio between the front wheel torque transmitted to the front tire and the rear wheel torque transmitted to the rear wheel when the amount exceeds a predetermined first predetermined value; The driving force control apparatus according to claim 1, comprising:   When the absolute value of the differential value of the reference torque exceeds a predetermined first predetermined value and the second-order differential value of the reference torque is less than or equal to a predetermined value, the torque distribution ratio calculating means 3. The driving force control apparatus according to claim 2, further comprising means for prohibiting obtaining a distribution ratio between the front wheel torque transmitted to the front tire and the rear wheel torque transmitted to the rear wheel.   The torque distribution ratio calculating means transmits the vibration torque to the tire of the front wheel in a process in which the driving-side vibration torque generated in either the front wheel or the rear wheel changes in a direction away from zero Newton meter. 2. The driving force control apparatus according to claim 1, further comprising means for distributing the torque for the front wheels and the torque for the rear wheels transmitted to the rear wheels.   The torque distribution ratio calculating means is such that the driving-side vibration torque generated in either the front wheel or the rear wheel is larger than the reference torque, and the difference between the reference torque and the vibration torque is maximized. 2. The driving force according to claim 1, further comprising means for distributing the vibration torque to a front wheel torque transmitted to the front wheel tire and a rear wheel torque transmitted to the rear wheel. Control device.

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