JP2012229737A - Control apparatus for driving force distribution mechanism - Google Patents

Abstract

The durability of a driving force distribution mechanism that distributes and transmits an input driving force to two axes is improved.
In a control device for a driving force distribution mechanism configured to distribute input torque to two axes that can rotate independently of each other and to move torque from one axis to the other, the drive An input torque calculation means (step S1) for obtaining torque input to the force distribution mechanism, and an upper limit of the moving torque to be moved between the two axes based on the input torque obtained by the input torque calculation means (step S1) A moving torque limiting means (step S3) is provided for determining a value and restricting the torque to be moved between the two axes to be equal to or less than the upper limit value.
[Selection] Figure 1

Description

  The present invention distributes and transmits the driving force transmitted from the power source to the left and right two axes or the two front and rear axes, and transmits the torque from one axis to the other axis so that it can be moved. The present invention relates to a force distribution mechanism, and more particularly to a device that controls movement of torque between the two axes.

  Conventionally, in various power devices, torque transmitted from a power source is distributed in two directions, and a predetermined operation is generated by the distributed torque, and the operation is performed with the distributed torque. A differential between the devices to be performed is generated according to the torque and load conditions. One example is a differential that distributes driving force to left and right driving wheels in a vehicle and a center differential that distributes driving force to front and rear propeller shafts.

  As a mechanism for distributing power in this way, a differential gear mechanism using a bevel gear, a planetary gear mechanism in which a pinion gear arranged between a sun gear and a ring gear is held by a carrier, and the like are adopted. This type of mechanism uses any one of the rotating elements as an input element and the other two rotating elements as output elements. Differential rotation occurs according to the load applied to these output elements, and torque is also reduced. Distributed. Therefore, when used as a mechanism for distributing driving force to the left and right driving wheels in a vehicle, or as a mechanism for distributing driving force to the front and rear propeller shafts, one of the driving wheels is in contact. If the road surface friction coefficient is low or the wheel is removed, the torque transmitted to the other driving wheel becomes small, or the so-called torque loss occurs such that the driving wheel idles. For example, torque may not be transmitted. Conventionally, as a mechanism for coping with such a situation, a driving force distribution mechanism configured to transmit one distributed torque or a part of the distributed torque to the other and move has been developed. Examples thereof are described in Patent Document 1 and Patent Document 2.

  On the other hand, in a driving force distribution mechanism that can control the movement of torque, a large torque may act locally as the torque moves, and this may cause a decrease in durability. Therefore, for example, in the invention described in Patent Document 3, for the purpose of suppressing deterioration in durability, an upper limit value of the accelerator opening is set based on a friction coefficient of the road surface, and the current accelerator opening is set to the upper limit. An apparatus configured to perform traction control by drive force distribution control by a control differential only when the value is equal to or less than the value is described. Further, Patent Document 4 discloses an anti-lock brake system (ABS) that controls driving force by control differential and restrains tire locking in order to suppress excessive torque from acting on the driving force distribution mechanism (control differential). ), An apparatus configured so as not to interfere with the driving force control according to FIG.

JP 2010-101338 A JP 2010-264806 A JP 2009-166572 A JP 2009-61855 A

  In the apparatus described in Patent Document 3 above, for example, an upper limit value for the accelerator opening is provided so as to prevent or suppress tire slip on a so-called straddle, and the accelerator opening exceeds the upper limit value. In such a case, since the traction control based on the driving force distribution is not executed, when the torque input to the control differential is large, no torque shift occurs in the control differential. Therefore, according to the device described in Patent Document 3, it is considered that excessive torque can be prevented or suppressed from acting on a mechanism that applies torque by torque movement or differential limitation, but a large torque close to the upper limit value. Alternatively, when the frequency at which a smaller torque is applied is high, the fatigue strength tends to decrease, and there is still room for improvement in order to improve the durability of the control differential or the driving force distribution mechanism.

  On the other hand, even with the device described in Patent Document 4, it is possible to avoid or suppress the excessive torque from acting on the driving force distribution mechanism, but it is the same as the invention described in Patent Document 3 above. In addition, not only relatively large torque but also less frequent torque is applied frequently, the fatigue strength tends to decrease, and it is still improved to improve the durability of the control differential or driving force distribution mechanism. There was room for.

  The present invention has been made paying attention to the above technical problem, and an object thereof is to provide a control device capable of improving the durability of the driving force distribution mechanism.

  In order to achieve the above object, the invention of claim 1 is configured to distribute the input torque to two shafts that can rotate independently of each other and to move the torque from one shaft to the other shaft. In the control device for the driving force distribution mechanism, an input torque calculation means for obtaining a torque input to the driving force distribution mechanism, and a movement for moving between the two axes based on the input torque obtained by the input torque calculation means A moving torque limiting means is provided for obtaining an upper limit value of the torque and for restricting a torque to be moved between the two axes to be equal to or lower than the upper limit value.

  According to a second aspect of the present invention, in the first aspect of the invention, each of the two shafts is configured to transmit torque to a driving wheel of a vehicle, and the movement of the torque between the two shafts by the moving torque limiting means. A control device for a driving force distribution mechanism configured to execute stabilization control of the vehicle when a slip of one of the driving wheels is detected in a state where the driving force is limited .

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the upper limit value is obtained based on a necessary number of repetitions of torque movement between the two axes and a torque input to the driving force distribution mechanism. The driving force distribution mechanism control device further includes an upper limit value calculation unit.

  According to a fourth aspect of the present invention, in the invention of the second or third aspect, the stabilization control includes a control for increasing the braking force of the slipped driving wheel and a control for decreasing the torque input to the driving force distribution mechanism. It is a control apparatus of the driving force distribution mechanism characterized by including control of at least any one of these.

  The invention of claim 5 is configured such that, in the invention of any one of claims 1 to 4, the upper limit value is set to a smaller value as the torque input to the driving force distribution mechanism is larger. Is a control device for a driving force distribution mechanism.

  According to the present invention, the upper limit value of the moving torque between the two axes is set based on the input torque to the driving force distribution mechanism, and when the torque is moved between the two axes, the moving torque is less than the upper limit value. Limited. Therefore, the torque applied to the mechanism for transmitting and moving the torque between the two axes is restricted, so that the durability of the driving force distribution mechanism can be improved. In particular, as described in claim 3, by configuring the upper limit value based on the required number of repetitions and the input torque, it is possible to suppress a decrease in fatigue strength and to improve the durability of the driving force distribution mechanism. Can be improved.

  In particular, according to the invention of claim 2, when the drive wheel slips in a state where the movement of the torque between the two shafts is limited, the vehicle stabilization control is executed, and the drive in which the slip is generated is performed. Controls such as increasing the braking force of the wheels or reducing the torque input to the driving force distribution mechanism are executed, so that the durability of the driving force distribution mechanism can be improved and the behavior of the vehicle is stabilized. Can be made.

It is a flowchart for demonstrating an example of the control performed by the driving force control apparatus which concerns on this invention. It is a diagram which shows the relationship between the lifetime of a driving force distribution mechanism, an input torque, and a movement torque. It is a diagram which shows the relationship between the estimated drive pinion torque at the time of setting a required life (predetermined number of times of torque movement) and movement torque. It is a schematic diagram for demonstrating the usage type of the driving force distribution mechanism in a vehicle.

  The control device according to the present invention is a control device targeting a driving force distribution mechanism that distributes and transmits input driving force to two axes, and a typical example thereof is a differential mechanism used in a vehicle. The present invention is not limited to this, and may be a driving force distribution mechanism widely used in general industrial machines. An example used in a vehicle is schematically shown in FIG. 4. FIG. 4A is an example in which the driving force distribution mechanism 1 is used as a rear differential of a vehicle, and an engine, a motor, or a hybrid device combining these. The driving force distribution mechanism 1 is connected to the driving force source 2 such as the above, and the driving force input from the driving force source 2 is distributed to the left and right rear wheel axles 3 and 4 and distributed to the left and right rear wheels 5 and 6. It is configured to transmit the driving force. FIG. 4B shows an example in which the driving force distribution mechanism 1 is used as a front differential. The driving force input from the driving force source 2 is distributed to the left and right front axles 7 and 8, and the distributed driving force is distributed. Is transmitted to the left and right front wheels 9,10. FIG. 4C shows an example in which the driving force distribution mechanism 1 is provided on each of the rear wheels 5 and 6 and the front wheels 9 and 10, and the driving force transmitted from the driving force source 2 is applied to each driving force. The force distribution mechanism 1 is configured to be distributed and transmitted to the left and right rear wheels 5 and 6 and the left and right front wheels 9 and 10. Further, the example shown in FIG. 4D is an example in which the driving force distribution mechanism 1 is used as a center differential, and the driving force input from the driving force source 2 is used as the rear propeller shaft on the rear wheels 5 and 6 side. 11 and the front propeller shaft 12 on the side of the front wheels 9 and 10 are distributed and transmitted.

  The driving force distribution mechanism 1 used in this way is a differential mechanism mainly composed of a bevel gear, a differential mechanism mainly composed of a planetary gear mechanism, and its differential, similarly to the previously known one. A friction mechanism that limits the action or a differential limiting mechanism that transmits the torque of one output element to the other output element, examples of which are described in Patent Document 1 and Patent Document 2, The driving force distribution mechanism 1 according to the present invention may have the same configuration as that described in Patent Documents 1 and 2. Therefore, the mechanism for moving the torque between the two output elements or the two shafts connected to each of them is constituted by a friction engagement mechanism such as a clutch or a brake operated by electromagnetic force or hydraulic pressure. The control device 13 according to the invention is configured to control the movement torque between the two shafts by controlling the engagement / release of the friction engagement element or controlling the torque capacity thereof.

  The control of the moving torque or the control of the differential limit in the driving force distribution mechanism 1 is executed to stabilize the behavior of the vehicle, to suppress the slip of the wheel, or to improve the turning performance, and the control May be a conventionally known control of content. Briefly explaining an example, a state in which one of the left and right wheels is out of wheel or slips on a road surface having a small road surface friction coefficient is determined based on an output value of a sensor such as a rotational speed sensor, Based on the determination result, the torque is moved to the other wheel side so that the torque distributed to the idling or slipping wheel side becomes small. Also, if the yaw or yaw rate is smaller than the target value during turning, the torque on the inner ring side is moved to the outer ring side in the turning state, and conversely if the yaw or yaw rate is larger than the target value, The torque is moved from the outer ring side to the inner ring side. Such torque movement is a control or control state that can also be referred to as differential restriction because it is a control that makes the distribution ratio different from the driving force distribution according to the load on each of the two axes to which torque is distributed. is there.

  The control device according to the present invention limits the movement of torque performed as described above based on the input torque to the driving force distribution mechanism 1. This is because the durability is improved or the deterioration of the durability is suppressed.

  An example of the control will be described with reference to the flowchart shown in FIG. The example shown here is directed to the driving force distribution mechanism 1 in a vehicle in which a transmission equipped with a torque converter is connected to the output side of the engine. Therefore, first, the turbine torque Tt, the shift position Psht, Is used to determine the estimated drive pinion torque Tdp (step S1). The turbine torque Tt can be calculated based on the output torque of the engine and the speed ratio of the torque converter, and the shift position Psht can be detected by a sensor. Further, the estimated drive pinion torque Tdp is a torque applied to the drive pinion constituting the input element in the driving force distribution mechanism 1 and corresponds to the input torque of the driving force distribution mechanism 1, and this is the turbine torque Tt described above. And the gear ratio according to the shift position Psht. Next, it is determined whether or not the estimated drive pinion torque Tdp exceeds the moving torque upper limit control start torque Tx (step S2).

  Here, the moving torque upper limit control start torque Tx will be described. The fatigue strength of the driving force distribution mechanism 1 includes the torque that is moved between one output element or a shaft that is integral with the output element and the other output element or the shaft that is integral with the output element, the number of repetitions of the movement, and the estimated drive pinion. It changes according to the torque (input torque) Tdp. An example thereof is schematically shown in FIG. 2. The larger the moving torque, the smaller the allowable number of repetitions, the larger the input torque Tdp, the smaller the allowable number of repetitions, and the smaller the allowable moving torque. Become. Such a relationship can be understood as the fact that the cumulative amount of load energy applied to the driving force distribution mechanism 1 affects the fatigue strength, and the specific amount is obtained by design or experiment. Or can be determined by simulation. From the relationship shown in FIG. 2 obtained in this way, the upper limit value of the moving torque for each input torque Tdp can be obtained by giving the required life (required life) as a product. If the relationship shown in FIG. 2 is replaced with the relationship between the estimated drive pinion torque Tdp and the upper limit value of the moving torque for the predetermined required life, it is as shown in FIG.

  In FIG. 3, the thick solid line indicates the upper limit value of the moving torque, and in particular, the constant value line indicated as Tmax is the upper limit value determined by the mechanism of the driving force distribution mechanism 1, and is the estimated drive pinion torque (input torque) Tdp. In the range where the torque increases to a predetermined value, the moving torque is limited to the upper limit value Tmax or less determined by the mechanism. The upper limit value of the estimated drive pinion torque Tdp that defines the range is the moving torque upper limit control start torque Tx. This is because the moving torque Tetv is increased as the estimated drive pinion torque Tdp increases in order to maintain a predetermined life. This is the torque at which control to gradually decrease starts.

In order to maintain a predetermined life, the moving torque Tetv is decreased as the estimated drive pinion torque Tdp increases, so when the estimated drive pinion torque Tdp increases, the moving torque Tetv is finally reduced to zero. Become. The estimated drive pinion torque Tdp that causes the moving torque Tetv to be zero is indicated by “Ty” in FIG. 3, and this is the moving torque non-operation lower limit torque. Therefore, the relationship between the estimated drive pinion torque Tdp and the moving torque Tetv for maintaining a predetermined life in the range of the above moving torque upper limit control starting torque Tx is such that the slope a is a = −Tmax / (Ty−Tx )
It can be represented by a straight line.

Therefore, if a negative determination is made in step S2, the movement torque Tetv is not limited in terms of control even if it is limited in terms of mechanism, so the routine shown in FIG. On the other hand, if the determination in step S2 is affirmative, that is, if the estimated drive pinion torque Tdp exceeds the moving torque upper limit control start torque Tx, the estimated drive for maintaining the above-mentioned predetermined lifespan. The moving torque Tetv is limited so as not to exceed the characteristic line (thick line in FIG. 3) that defines the relationship between the pinion torque Tdp and the moving torque Tetv (step S3). More specifically, the moving torque Tetv is limited to the following equation based on the estimated drive pinion torque Tdp at that time and the relationship between the estimated drive pinion torque Tdp that defines the predetermined life and the moving torque Tetv. .
Tetv <a × (Ty−Tdp)

  That is, when it is detected that the estimated drive pinion torque Tdp increases due to the accelerator pedal being depressed or downshifted, and one of the front, rear, left and right drive wheels slips in that state. To stabilize the behavior of the vehicle or to smoothly start the vehicle, the torque moves from the drive wheel where slip occurs or from the drive wheel where the grip force is expected to decrease to the other drive wheel. Be made. If the estimated drive pinion torque Tdp is equal to or less than the above-described moving torque upper limit control starting torque Tx, the moving torque can be increased to the maximum on the mechanism, but if it exceeds the moving torque upper limit control starting torque Tx, Depending on the estimated drive pinion torque Tdp, the travel torque Tetv is determined based on the life determined in design. Specifically, the greater the estimated drive pinion torque Tdp, the smaller the moving torque Tetv is limited. For example, when such a control is applied to the driving force distribution mechanism or the control differential described in Patent Document 1 or Patent Document 2 described above, the engagement force (ie, torque capacity) of the friction engagement mechanism is increased or decreased. It is executed by controlling to.

  The control example shown in FIG. 1 is configured to further determine the stability of the behavior of the vehicle in a state where the moving torque Tet is limited as described above. That is, following the above step S3, the slip is determined (step S4). For example, in a vehicle equipped with an anti-lock brake system (ABS), this determination may be performed by obtaining a determination result by the anti-lock brake system, or the steering angle (steering angle or turning angle) and the left and right What is necessary is just to comprise so that it may determine that the slip has arisen when the difference rotation exceeding the rotation speed difference of the right-and-left wheels according to a steering angle is detected based on the difference rotation of a tire.

  If the slip determination is not satisfied, that is, if a negative determination is made in step S4, the routine of FIG. 1 is temporarily terminated without performing any new control. On the contrary, if the determination of slip is established, the control for stabilizing the behavior of the vehicle is forcibly executed (step S5). The control is for giving priority to the stabilization of the vehicle, and increases the braking force of the wheel in which the slip occurs, or decreases the output of the driving force source such as the engine, and is applied to the driving wheel. This is a control in which upshifting is performed in order to reduce the torque, either alone or in combination, and conventionally known vehicle stability control (VSC) is one example. In addition, when such control for stabilizing the vehicle is forcibly executed, it is preferable to execute notification control such as making a warning sound for the driver or overturning the warning display. .

  As described above, according to the control device of the present invention, the moving torque Tetv is limited according to the estimated drive pinion torque Tdp of the driving force distribution mechanism 1, that is, the input torque. The service life can be improved by suppressing the decrease. In particular, the required life is set so that the moving torque with respect to the input torque Tdp becomes smaller as the number of times of torque movement is repeated, so that the moving torque is not excessively limited, and thus the vehicle behavior stability control is impaired. It will not be. Further, when slip occurs in the state where the moving torque in the driving force distribution mechanism 1 is limited, the control for stabilizing the behavior of the vehicle is preferentially or forcibly executed. The behavior of the vehicle can be stabilized without reducing the durability of the vehicle 1.

  Here, the relationship between the above specific example and the present invention will be briefly described. The functional means for executing the control in step S1 shown in FIG. 1 corresponds to the input torque calculating means in the present invention. The functional means for executing the control corresponds to the moving torque limiting means or the upper limit value calculating means in the present invention, and the control in step S5 corresponds to the vehicle stabilization control in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Driving force distribution mechanism, 2 ... Driving force source, 3, 4 ... Rear wheel axle, 5, 6 ... Rear wheel, 7, 8 ... Front wheel axle, 9, 10 ... Front wheel, 11 ... Rear propeller shaft, 12 ... Front Propeller shaft, 13 ... Control device.

Claims (5)

In the control device of the driving force distribution mechanism configured to distribute the input torque to two axes that can rotate independently from each other and to move the torque from one axis to the other axis,
Input torque calculating means for obtaining torque input to the driving force distribution mechanism;
Based on the input torque obtained by the input torque calculating means, the upper limit value of the moving torque to be moved between the two axes is obtained, and the moving torque limit for restricting the torque to be moved between the two axes to the upper limit value or less. And a driving force distribution mechanism control device. Each of the two shafts is configured to transmit torque to the drive wheels of the vehicle,
It is configured to execute the vehicle stabilization control when a slip of one of the drive wheels is detected in a state where the movement of the torque between the two shafts is limited by the moving torque limiting means. The drive force distribution mechanism control device according to claim 1, wherein   The apparatus further comprises an upper limit value calculating means for obtaining the upper limit value based on a required number of repetitions of torque movement between the two axes and a torque input to the driving force distribution mechanism. 3. A control device for a driving force distribution mechanism according to 1 or 2.   The stabilization control includes at least one of control for increasing braking force of slipped drive wheels and control for reducing torque input to the driving force distribution mechanism. 4. The control device for a driving force distribution mechanism according to 2 or 3.   5. The driving force distribution mechanism according to claim 1, wherein the upper limit value is set to a smaller value as the torque input to the driving force distribution mechanism is larger. Control device.

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