JP2009262584A - Driving force distribution control device of four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving force distribution control device of a four-wheel drive vehicle in which the bearing strength of a drive system on an auxiliary drive wheel side is set small. <P>SOLUTION: In a four-wheel drive vehicle, the output torque of an engine 1 is transmitted to main drive wheels 5, 6, and transmitted to auxiliary drive wheels 7, 8 through a torque distribution actuator 9, an estimated main drive wheel allowable torque calculation means 10 calculates estimated main drive wheel allowable drive torque based on estimated loads of the main drive wheels, a target transmission torque setting means 10 stores, as the target transmission torque to the auxiliary drive wheel, a value obtained by deducting the estimated main drive wheel allowable drive torque from overall drive torque based on the output torque of the engine, and sets the target transmission torque a value of previously-stored target transmission torque as far as there arises no rotational difference not smaller than a prescribed value between the main drive wheels and the auxiliary drive wheels when there is a drive torque request higher than that in succeeding processing, and an actuator control means 10 controls the target transmission torque so as to be transmitted to the auxiliary drive wheels. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention transmits the output torque of a prime mover that is a drive source of a vehicle to a main drive wheel that is one of front wheels and rear wheels, and is the other of front wheels and rear wheels via a torque distribution actuator. A driving force distribution control device that controls the operation of the torque distribution actuator of a four-wheel drive vehicle that transmits to the sub drive wheels, and makes the torque distribution between the main drive wheels and the sub drive wheels according to the vehicle state. It is about.

As a driving force distribution control device for a four-wheel drive vehicle as described above, a device disclosed in, for example, Patent Document 1 is conventionally known. This driving force distribution control device controls the operation of a torque distribution actuator, thereby The torque distribution between the drive wheels and the sub-drive wheels is made according to the static load distribution as the vehicle state, and when a higher drive torque is requested from the driver or the general control device, the four wheels of the front wheel drive base According to the increase in the load distribution due to the acceleration of the rear wheels as the auxiliary driving wheels because of the driving vehicle, the torque distribution of the auxiliary driving wheels is increased to meet the demand.
JP 2001-225658 A

  However, in the driving force distribution control device for the conventional four-wheel drive vehicle, when a higher driving torque is required, the load distribution of the auxiliary driving wheel is always increased without considering the estimated allowable driving torque of the main driving wheel. The target transmission torque is set by increasing the torque distribution of the auxiliary drive wheels. For this reason, although it has excellent startability and acceleration, torque is distributed to the sub drive wheels even when the drive torque can be tolerated only by the main drive wheels. Since a load is applied, it is desirable to improve that it is difficult to reduce the drive unit weight and cost by setting the proof strength of the drive system on the auxiliary drive wheel side to be smaller.

  SUMMARY OF THE INVENTION An object of the present invention is therefore to propose a driving force distribution control device for a four-wheel drive vehicle, in which the proof strength of the drive system on the auxiliary drive wheel side can be set small.

  For this purpose, the driving force distribution control device for a four-wheel drive vehicle according to the present invention transmits the output torque of a prime mover that is a drive source of the vehicle to the main drive wheel that is one of the front wheels and the rear wheels, and the torque. The torque of the main drive wheel and the sub drive wheel is controlled by controlling the operation of the torque distribution actuator of a four-wheel drive vehicle that transmits to the sub drive wheel, which is the other of the front wheels and the rear wheels, via the distribution actuator. In the driving force distribution control device in which the distribution depends on the vehicle state, the driving force distribution control device includes estimated main driving wheel allowable torque calculating means, target transmission torque setting means, and actuator control means, each of which repeatedly performs processing at predetermined time intervals. The main drive wheel allowable torque calculating means calculates an estimated main drive wheel allowable drive torque based on the estimated load of the main drive wheel, and the target transmission torque setting means is an output of the prime mover. The value obtained by subtracting the estimated main driving wheel allowable driving torque from the total driving torque based on the torque is set and stored as the target transmission torque to the auxiliary driving wheel, and when a higher driving torque is requested in the next processing If the rotation difference between the main drive wheel and the sub drive wheel is not greater than a predetermined value, the stored target transmission torque value is set as the target transmission torque to the sub drive wheel, and the actuator control means is The operation of the torque distribution actuator is controlled so as to transmit the target transmission torque to the auxiliary driving wheel.

  In the driving force distribution control device for a four-wheel drive vehicle according to the present invention, the estimated main drive wheel allowable torque calculating means performs the estimated main drive wheel based on the estimated load of the main drive wheel by performing processing repeatedly at predetermined time intervals. The allowable drive torque is calculated, and the target transmission torque setting means sets and stores the value obtained by subtracting the estimated main drive wheel allowable drive torque from the total drive torque based on the output torque of the prime mover as the target transmission torque to the sub drive wheels. When a higher driving torque is requested in the next process, if the rotational difference between the main driving wheel and the sub driving wheel does not occur more than a predetermined value, the stored target transmission torque value is set to the target driving wheel. The transmission torque is set, and the actuator control means controls the operation of the torque distribution actuator so that the target transmission torque set by the target transmission torque setting means is transmitted to the sub drive wheels.

  Therefore, according to the driving force distribution control device for a four-wheel drive vehicle of the present invention, when the vehicle can start or accelerate with only the main drive wheel, for example, traveling on a high μ road, the estimated main drive wheel allowable drive torque Therefore, the target transmission torque to the auxiliary driving wheel is set smaller than the allowable driving torque of the auxiliary driving wheel, so that the driving load applied to the driving system on the auxiliary driving wheel side can be reduced. Therefore, the proof strength of the drive system on the side of the auxiliary drive wheel can be set smaller, and the weight of the drive unit can be reduced and the cost can be reduced.

  Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings. FIG. 1 is an overall system diagram showing a power train provided with a first embodiment of the driving force distribution control device for a four-wheel drive vehicle according to the present invention.

  In the figure, reference numeral 1 is an engine as a prime mover, 2 is a stepped automatic transmission, 3 is a front differential, 4 is a rear differential, 5 is a right front wheel, 6 is a left front wheel, 7 is a right rear wheel, 8 is a left rear wheel, 9 is a torque distribution actuator having a normal electromagnetic clutch, 10 is a torque distribution controller having a normal microcomputer, 11 is a right front wheel speed sensor, 12 is a left front wheel speed sensor, 13 is a right rear wheel speed sensor, 14 Is a left rear wheel speed sensor, 15 is an accelerator opening sensor for detecting the amount of depression of an accelerator pedal, and 16 is an engine controller that also includes an ordinary microcomputer and controls the ignition timing of the engine 1 and the like.

  In the four-wheel drive vehicle to which the drive force distribution control device of the first embodiment is applied, the drive torque of the engine 1 is directly transmitted to the left and right front wheels 5 and 6 as main drive wheels, and the left and right as sub drive wheels. The rear wheels 7 and 8 are front-wheel drive-based four-wheel drive vehicles to which the drive torque of the engine 1 is transmitted via the torque distribution actuator 9. That is, when the torque distribution actuator 9 is in the released state, the torque distribution ratio of front wheel: rear wheel = 100: 0 is established, and the torque distribution actuator 9 is fastened with a torque equal to or greater than ½ torque of the drive torque of the engine 1. For example, the front wheel: rear wheel = 50: 50 is an equal torque distribution ratio, and is transmitted to the front wheels 5, 6 and the rear wheels 7, 8 by the fastening torque of the torque distribution actuator 9 that operates according to a control command from the torque distribution controller 10. The torque distribution ratio is variably controlled in the range of front wheel: rear wheel = 100: 0 to 50:50.

  The torque distribution controller 10 includes a wheel speed signal from each wheel speed sensor 11, 12, 13, 14, an accelerator opening signal from the accelerator opening sensor 15, an engine rotation signal from the engine controller 16, and this is also normal. And a gear position signal from an automatic transmission controller (not shown) that controls the shift operation of the automatic transmission 2.

  Then, the torque distribution controller 10 performs estimation processing for calculating the estimated main driving wheel allowable driving torque based on the estimated load of the main driving wheel by repeatedly performing arithmetic processing according to the determined control law every short time (for example, 100 ms). A value obtained by subtracting the estimated main driving wheel allowable driving torque from the total driving torque based on the driving torque of the engine 1 and the main driving wheel allowable torque calculating unit 10a is set and stored as a target transmission torque to the sub driving wheel, and stored next time. When a higher drive torque is required in the processing, if the rotation difference between the main drive wheel and the sub drive wheel does not exceed a predetermined value, the previously stored target transfer torque value is used as the target transfer torque to the sub drive wheel. A target transmission torque setting unit 10b to be set and an actuator for controlling the operation of the torque distribution actuator so as to transmit the set target transmission torque to the sub drive wheels. Functions as motor control section 10c, and outputs a control command due to the calculation result to the torque distribution actuator 9.

  FIG. 2 is a flowchart showing torque distribution control executed by the torque distribution controller 10 of the driving force distribution control device of the first embodiment.

  In step S1, the estimated main driving wheel load and the estimated longitudinal load distribution are calculated and the estimated road friction coefficient μ (previous value) is read. Here, the estimated main drive wheel (front wheel) load and the estimated front-rear load distribution can be obtained from the total vehicle weight and the front-rear weight distribution given in advance according to the specifications of the vehicle. The estimated road surface μ (previous value) is stored by the previous execution of steps S7 to S9 described later.

  In the next step S2, the calculated estimated main driving wheel load is multiplied by the read estimated estimated road surface μ (previous value), and the estimated main driving wheel equal to the estimated friction force of the left and right front wheels 5, 6 as the main driving wheel. The allowable torque (previous value) is calculated, and in the subsequent step S3, the total driving force is calculated and the auxiliary driving wheel command torque (previous value) is read. Here, the total driving force is determined based on the current engine torque estimated value and the current gear ratio of the automatic transmission 2, and the current engine torque estimated value is determined by the accelerator opening signal from the accelerator opening sensor 15 and the engine controller 16. And the current gear ratio of the automatic transmission 2 is obtained from the gear position signal from the automatic transmission controller. The auxiliary drive wheel command torque (previous value) is set and stored in step S12 described later.

  In the next step S4, the main driving wheel distribution torque is calculated by subtracting the auxiliary driving wheel command torque (previous value) from the total driving force, and in the subsequent step S5, the forward / backward differential rotation, which is the rotational speed difference between the front and rear wheels, is predetermined. It is determined whether or not the value is greater than or equal to the value. In this determination, first, a front wheel right wheel speed, a front wheel left wheel speed, a rear wheel right wheel speed, and a rear wheel left wheel speed are calculated based on wheel speed signals from the wheel speed sensors 11, 12, 13, and 14. Then, the difference between the front and rear rotational speeds is calculated by taking the difference between the average value of the left and right front wheel speeds and the average value of the left and right rear wheel speeds. This calculation may be omitted by diverting the calculation result of the ABS controller in a vehicle equipped with an anti-skid brake system (ABS).

  Next, the obtained front-rear differential rotation is compared with a predetermined value to determine whether the front-rear differential rotation is equal to or smaller than a predetermined value. This predetermined value is set, for example, to the extent that it occurs due to the idling of the front wheels whether or not the driver notices during two-wheel drive driving with only the front wheels on a wet road surface due to rain, so that the normal dry road surface or slightly wet The forward / backward differential rotation is less than a predetermined value on the road surface. For example, the forward / backward differential rotation exceeds a predetermined value on a snowy road or an icy road.

  If the result of determination in step S5 is that the forward / backward differential rotation is less than or equal to a predetermined value (YES), in next step S6, whether or not the main drive wheel distribution torque is greater than or equal to the estimated main drive wheel allowable torque (previous value). If the main driving wheel distribution torque is greater than the estimated main driving wheel allowable torque (previous value) (YES), the estimated road surface μ value has not yet reached the predetermined upper limit value in the next step S7. If not, the value is increased by a certain value to obtain the current value (increment).

  On the other hand, if the result of determination in step S5 is that the forward / backward differential rotation is not less than or equal to the predetermined value (NO), in step S8, the main driving wheel distribution torque and the estimated main driving wheel allowable torque (previous value) are lower. The estimated road surface μ (current value) is calculated from the road and the estimated driving wheel load and compared with the estimated road surface μ (previous value). If the current value is lower, the estimated road surface μ value is still set to the specified lower limit. If the value does not reach, the value is decreased by a certain value to the current value (decrement). As a result of the determination in step S6, if the main drive wheel distribution torque is not equal to or greater than the estimated main drive wheel allowable torque (previous value) (NO), the previous value as the current value of the estimated road surface μ is obtained in step S9. To maintain.

  In the next step S10, the current value of the estimated road surface μ is multiplied by the estimated main drive wheel load to calculate the estimated main drive wheel allowable torque (current value). In the subsequent step S11, the estimated main drive wheel is calculated from the total drive force. The sub drive wheel distribution torque T1 is calculated by subtracting the allowable torque (current value). In the next step S12, the sub drive wheel distribution torque T1 is used as the sub drive wheel command torque (current value) as the target transmission torque. Set and remember. Then, a control command corresponding to the sub drive wheel command torque (current value) is output to the torque distribution actuator 9.

  Accordingly, in the processing of the torque distribution controller 10, steps S1 to S10 are estimated main drive wheel allowable torque calculation units 10a as estimated main drive wheel allowable torque calculation means, and steps S11 to S12 are target transmissions as target transmission torque setting means. The torque setting unit 10b and step S12 correspond to an actuator control unit 10c as actuator control means.

  According to the driving force distribution control device of the first embodiment, the estimated main driving wheel allowable driving torque is greatly calculated in a state where starting or acceleration is possible with only the main driving wheel, such as traveling on a high μ road. Therefore, since the target transmission torque to the auxiliary driving wheel is set smaller than the allowable driving torque of the auxiliary driving wheel, the vehicle can travel with the front and rear wheel torque distribution close to that of the front wheel driving vehicle. The driving load applied to the drive system can be reduced. Therefore, the proof strength of the drive system on the side of the auxiliary drive wheels can be set smaller to reduce the weight and cost of the drive unit.

  FIG. 3 is an overall system diagram showing a power train provided with a second embodiment of the driving force distribution control apparatus for a four-wheel drive vehicle according to the present invention. The same parts as those in the first embodiment in the figure are the same as those shown in FIG. It shows with the code | symbol. The driving force distribution control device for a four-wheel drive vehicle according to the second embodiment differs from the first embodiment only in that the torque distribution controller 10 further includes a target transmission torque lower limit holding unit 10d. The configuration is the same as in the first embodiment.

  FIG. 4 is a flowchart showing the torque distribution control executed by the torque distribution controller 10 of the driving force distribution control apparatus of the second embodiment, and this flowchart is different from the flowchart of the first embodiment shown in FIG. Since only step S12 and subsequent steps are described, only the differences will be described below.

  In the driving force distribution control apparatus of the second embodiment, the torque distribution controller 10 is the same as the conventional one based on the estimated longitudinal load distribution previously obtained in step S1 and the total kite power obtained in step S3 in step S12. A sub-drive wheel distribution torque T2 in which the total power is distributed to the rear wheel side as a sub drive wheel according to the front-rear load distribution is obtained.

  In the next step S13, it is determined whether or not the auxiliary driving wheel distribution torque T2 obtained in step S12 is equal to or larger than a predetermined lower limit value Tmin1 of the auxiliary driving wheel command torque, and the auxiliary driving wheel distribution torque T2 corresponding to the longitudinal load distribution is determined. If it is equal to or greater than the predetermined lower limit value Tmin1 (YES), in the next step S14, the predetermined lower limit of the sub drive wheel distribution torque T1 and the sub drive wheel command torque based on the estimated main drive wheel allowable drive torque obtained in step S11 The value Tmin2 (<Tmin1) is compared, and the higher value is set and stored as the auxiliary driving wheel command torque (current value) as the target transmission torque. Then, a control command corresponding to the sub drive wheel command torque (current value) is output to the torque distribution actuator 9.

  On the other hand, if the sub-drive wheel distribution torque T2 is not equal to or greater than the predetermined lower limit value Tmin1 (NO) in step S13, in step S15, the sub-drive wheel distribution torque T2 corresponding to the front / rear load distribution is used as the sub-target transmission torque. Set and store as drive wheel command torque (current value). Then, a control command corresponding to the sub drive wheel command torque (current value) is output to the torque distribution actuator 9.

  Therefore, steps S12 to S15 in the processing of the torque distribution controller 10 correspond to the target transmission torque lower limit holding unit 10d. According to the driving force distribution control device of the second embodiment, the same operation as that of the first embodiment is performed. In addition to obtaining the effect, if the auxiliary drive wheel distribution torque T2 corresponding to the front / rear load distribution is less than the predetermined lower limit Tmin1, the auxiliary drive wheel distribution torque T2 corresponding to the front / rear load distribution (not zero) is transmitted to the target. When the auxiliary drive wheel distribution torque T2 corresponding to the front / rear load distribution is equal to or greater than the predetermined lower limit value Tmin1, the predetermined lower limit of the sub drive wheel distribution torque T1 and the sub drive wheel command torque based on the estimated main drive wheel allowable drive torque Since the higher one of the values Tmin2 is the target transmission torque, the initial idling of the main drive wheels when starting the vehicle can be suppressed, and the startability can be improved.

  FIG. 5 is an overall system diagram showing a power train provided with a third embodiment of the driving force distribution control device for a four-wheel drive vehicle according to the present invention. The same parts as those in the second embodiment are the same as those in the second embodiment. It shows with the code | symbol. The driving force distribution control device for a four-wheel drive vehicle of the third embodiment further includes a longitudinal acceleration detector 17 composed of a normal acceleration sensor as a longitudinal acceleration detection means for detecting the longitudinal acceleration of the vehicle. Only the point provided and connected is different from the second embodiment, and the other points are the same as those of the second embodiment. Although the torque distribution controller 10 of the driving force distribution control device for a four-wheel drive vehicle according to the third embodiment also has a target transmission torque lower limit holding unit 10d, illustration thereof is omitted.

  FIG. 6 is a flowchart showing the torque distribution control executed by the torque distribution controller 10 of the driving force distribution control device of the third embodiment, and this flowchart is different from the flowchart of the second embodiment shown in FIG. Since only step S0 is provided, only the difference will be described below.

  In the driving force distribution control device of the third embodiment, the torque distribution controller 10 calculates the estimated main driving wheel load obtained in the next step S1 in accordance with the longitudinal acceleration value input from the longitudinal acceleration detector 17 in step S0. to correct. That is, when the vehicle accelerates, the front and rear load distribution increases on the auxiliary driving wheel (rear wheel) side and the main driving wheel as compared with the distribution obtained from the total vehicle weight and the front and rear weight distribution given in advance according to the specification of the vehicle. Since the (front wheel) side decreases, the estimated main drive wheel load is decreased in accordance with an increase in the longitudinal acceleration value.

  According to the driving force distribution control device of the third embodiment, the same effect as that of the second embodiment can be obtained, and the estimated main driving wheel load is corrected according to the longitudinal acceleration value. The target transmission torque can be calculated more accurately, and the target transmission torque to the rear wheels, which are the auxiliary drive wheels, can be increased in accordance with the load movement to the rear when the vehicle starts and accelerates. And acceleration can be improved.

  FIG. 7 is an overall system diagram showing a power train provided with a fourth embodiment of the driving force distribution control device for a four-wheel drive vehicle of the present invention. The same parts as those in the second embodiment are the same as those in the second embodiment. It shows with the code | symbol. The driving force distribution control device for a four-wheel drive vehicle of the fourth embodiment is different from the second embodiment only in that it further includes a wheel slip detector 18 as wheel slip detection means for detecting wheel slip. The other points are the same as in the second embodiment.

  Specifically, the torque distribution controller 10 of the driving force distribution control device for the four-wheel drive vehicle according to the fourth embodiment is configured so that the front wheel right side is based on the wheel speed signals from the wheel speed sensors 11, 12, 13, and 14. Calculate the wheel speed, front wheel left wheel speed, rear wheel right wheel speed, rear wheel left wheel speed, and take the difference between the average value of the left and right front wheel speeds and the average value of the left and right rear wheel speeds. By calculating the difference, it functions as a wheel slip detector 18. Further, the torque distribution controller 10 of the driving force distribution control device for a four-wheel drive vehicle according to the fourth embodiment also has a target transmission torque lower limit holding unit 10d, which is not shown.

  FIG. 8 is a flowchart showing the torque distribution control executed by the torque distribution controller 10 of the driving force distribution control apparatus of the fourth embodiment. This flowchart differs from the flowchart of the second embodiment shown in FIG. Since only step S5-1 and step S5-2 are included, only the differences will be described below.

  In the driving force distribution control device of the fourth embodiment, the torque distribution controller 10 determines the left and right front wheels 5, 6 based on the wheel speed signals from the wheel speed sensors 11, 12, 13, 14 in step S5-1. In addition, it is determined whether or not the amount of slipping of one or more of the left and right rear wheels 7 and 8 is greater than or equal to a predetermined value. If the amount of slipping of one or more wheels is greater than or equal to a predetermined value (YES), the process proceeds to step S8 described above. Otherwise, in the next step S5-2, as in step S5 described above, it is determined whether the front-rear differential rotation is equal to or less than a predetermined value.If the front-rear differential rotation is equal to or less than the predetermined value, the process proceeds to step S7 described above. Otherwise, the process proceeds to step S9 described above.

  According to the driving force distribution control device of the fourth embodiment, in addition to the same effects as those of the second embodiment, in addition to the idling amount of one or more wheels being a predetermined value or more, or the forward / rearward rotation is a predetermined value. If it exceeds, the estimated road surface μ value is decreased to reduce the estimated main drive wheel allowable drive torque, so even if idling occurs on the main drive wheel, the total drive force is reduced regardless of the method such as engine torque reduction. It is possible to suppress the subsequent idling of the wheels without having to do so, and even when starting acceleration or intermediate acceleration by entering a low μ road such as a snowy road with a small distribution torque to the auxiliary driving wheels, The distribution torque is set to a predetermined value or more to prevent the main drive wheels from slipping, so that start acceleration and intermediate acceleration equivalent to those on asphalt roads can be performed even on snowy roads.

  FIG. 9 is an overall system diagram showing a power train provided with a fifth embodiment of the driving force distribution control device for a four-wheel drive vehicle of the present invention, and the same parts as those of the second embodiment are the same as those in the second embodiment. It shows with the code | symbol. The driving force distribution control device for a four-wheel drive vehicle of the fifth embodiment is different from the second embodiment only in that it further includes a gradient detector 19 as a gradient detecting means for detecting the gradient of the road surface. This is the same as in the second embodiment.

  It should be noted that there is a relationship between the road surface gradient and the vehicle longitudinal acceleration because the vehicle longitudinal acceleration decreases as the angle of the road gradient increases even with the same total driving force. In the driving force distribution control device for a four-wheel drive vehicle of the fifth embodiment, the torque distribution controller 10 includes the longitudinal acceleration detector 17 as in the third embodiment shown in FIG. 5, and the longitudinal acceleration detector 17 detects it. Based on the longitudinal acceleration of the vehicle and the total driving force previously obtained in step S2, the degree of the road slope is obtained using, for example, a map determined in advance through experiments. Further, the torque distribution controller 10 of the driving force distribution control device for a four-wheel drive vehicle according to the fifth embodiment also has a target transmission torque lower limit holding unit 10d, which is not shown.

  FIG. 10 is a flowchart showing the torque distribution control executed by the torque distribution controller 10 of the driving force distribution control apparatus of the fifth embodiment, and this flowchart is different from the flowchart of the second embodiment shown in FIG. Since only step S0 is provided, only the difference will be described below.

  In the driving force distribution control device of the fifth embodiment, the torque distribution controller 10 determines in step S0 according to the road surface gradient determined as described above from the longitudinal acceleration value input from the longitudinal acceleration detector 17. The estimated main driving wheel load obtained in the next step S1 is corrected. That is, when the angle of the road slope increases, the front / rear load distribution increases on the secondary drive wheel (rear wheel) side than the distribution obtained from the total vehicle weight and the front / rear weight distribution given in advance according to the specifications of the vehicle. At the same time, since the main drive wheel (front wheel) side is reduced, the estimated main drive wheel load is reduced in accordance with an increase in the angle of the road slope.

  According to the driving force distribution control device of the fifth embodiment, in addition to obtaining the same operational effects as the second embodiment, the estimated main driving wheel load is corrected according to the angle of the road slope, so The target transmission torque to the rear wheels can be calculated with higher accuracy, and the target transmission torque to the auxiliary drive wheels can be increased as the angle of the road slope increases when the vehicle starts and accelerates. And acceleration can be improved.

  FIG. 11 is a time chart showing the effect of the driving force distribution control by the driving force distribution control device of each of the above-described embodiments at the time of starting acceleration of the vehicle and the subsequent intermediate acceleration. As shown in FIG. When the accelerator opening is maintained at 25% for 3 seconds and the accelerator opening is returned to 0% for 3 seconds when starting acceleration up to 4 seconds, first the high total driving torque rises at the first speed, and at about 3 seconds as the vehicle speed increases. Upshifting to 2nd speed and then 3rd speed at about 4 seconds, the total driving torque decreases accordingly, and the gear position is maintained at 0 for the total driving torque from 0 to 4% after about 4 seconds. And coast.

  At the time of starting acceleration, the distribution torque to the rear wheels, which are auxiliary driving wheels, is maintained almost constant as shown by the broken line at the bottom of FIG. 11 in the case of conventional control. As indicated by the solid line in the same section, the total driving torque can be reduced after rising, thereby allowing the vehicle to travel with front and rear wheel torque distribution close to that of the front wheel drive vehicle.

  Also, as shown in the figure, when the accelerator opening is maintained at 50% for 5 seconds during the intermediate acceleration from 10 seconds to 15 seconds and then returned to 0%, the first speed is maintained at the third speed maintained by the coasting. As the driving torque increases and the vehicle speed increases, the upshift is made to the fourth speed at about 13 seconds, and the total driving torque decreases accordingly, and the total driving torque is 0 for the subsequent accelerator opening 0% after about 15 seconds. Keep coasting and keep coasting.

  Even during this intermediate acceleration, the distribution torque to the rear wheels, which are auxiliary driving wheels, is maintained at a certain level as shown by the broken line at the bottom of FIG. Accordingly, as indicated by the solid line in the same section, it can be maintained at a low level as it is lowered at the time of starting acceleration, thereby enabling traveling with front and rear wheel torque distribution close to that of the front wheel drive vehicle.

  Therefore, also from this result, it can be seen that the driving force distribution control device of each of the above embodiments can reduce the driving load applied to the driving system on the auxiliary driving wheel side. Therefore, according to the driving force distribution control device of each of the above embodiments, it is possible to reduce the driving unit in weight and cost by setting the proof strength of the driving system on the auxiliary driving wheel side smaller.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described examples, and various modifications can be made within the scope of the claims. For example, the driving force distribution control of the present invention can be applied to a four-wheel drive vehicle based on rear wheel drive, in which case the rear wheel is the main drive wheel and the front wheel is the auxiliary drive wheel. Moreover, although the said Example was applied to the four-wheel drive vehicle provided with a stepped automatic transmission, the drive force distribution control of this invention can also be applied to the four-wheel drive vehicle provided with a continuously variable automatic transmission.

  Thus, according to the driving force distribution control device for a four-wheel drive vehicle of the present invention, the estimated main drive wheel allowable drive torque is increased in a state where starting or acceleration is possible with only the main drive wheel, for example, traveling on a high μ road. Since the target transmission torque to the auxiliary drive wheel is set smaller than the allowable drive torque of the auxiliary drive wheel, the driving load applied to the drive system on the auxiliary drive wheel side can be reduced. Therefore, it is possible to reduce the drive unit weight and cost by setting the proof strength of the drive system on the auxiliary drive wheel side smaller.

  In the present invention, the target transmission torque setting means has a target transmission torque lower limit value, and the higher value of the set target transmission torque and the target transmission torque lower limit value is newly set as the target transmission torque. It may be set. In this way, even when entering a low μ road such as a snowy road with a small distribution torque to the auxiliary drive wheels and starting acceleration or intermediate acceleration, the distribution torque to the auxiliary drive wheels is greater than a predetermined value. As the main drive wheels are prevented from idling, starting acceleration and intermediate acceleration equivalent to those on asphalt roads can be performed even on snowy roads.

  In the present invention, the driving force distribution control device includes a longitudinal acceleration detecting means for detecting longitudinal acceleration of the vehicle, and the main driving wheel estimated allowable torque calculating means is a vehicle detected by the longitudinal acceleration detecting means. The estimated load of the main drive wheel may be corrected according to the magnitude of the longitudinal acceleration. In this way, the target transmission torque to the rear wheels can be calculated with higher accuracy, so that the target to the rear wheels, which are the auxiliary driving wheels, can be determined according to the rearward load movement when the vehicle starts and accelerates. The transmission torque can be increased, and the startability and acceleration can be improved.

  Further, according to the present invention, the driving force distribution control device includes main driving wheel slip detection means for detecting slip of the main driving wheel of the vehicle, and the main driving wheel estimated allowable torque calculation means includes the main driving wheel. When the wheel slip detection means detects the slip of the main driving wheel, the estimated allowable torque of the main driving wheel may be reduced. In this way, even if idling occurs on the main drive wheel, it is possible to suppress the subsequent idling of the wheel without reducing the total driving force, regardless of the method such as engine torque reduction, and distribution to the sub drive wheel. Even if you enter a low μ road such as a snowy road with low torque and start acceleration or intermediate acceleration, the distribution torque to the sub drive wheels is set to a predetermined value or more to prevent the main drive wheels from slipping. Even on roads, start acceleration and intermediate acceleration equivalent to asphalt roads can be performed.

  In the present invention, the main driving wheel is a front wheel of the vehicle, and the driving force distribution control device includes an ascending gradient detecting means for detecting an ascending gradient of a road surface on which the vehicle is traveling, and The transmission torque setting means may set the target transmission torque larger when the ascending gradient detecting means detects the ascending gradient than when there is no gradient. In this way, the target transmission torque to the rear wheel, which is the auxiliary drive wheel, can be calculated with higher accuracy. Therefore, when the vehicle starts and accelerates, the larger the angle of the road uphill, the greater the change to the auxiliary drive wheel. The target transmission torque can be increased, and the startability and acceleration can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall system diagram showing a power train provided with a first embodiment of a driving force distribution control device for a four-wheel drive vehicle according to the present invention; It is a flowchart which shows the torque distribution control which the torque distribution controller of the driving force distribution control apparatus of the said 1st Example performs. It is a whole system figure which shows the power train provided with 2nd Example of the driving force distribution control apparatus of the four-wheel drive vehicle of this invention. It is a flowchart which shows the torque distribution control which the torque distribution controller of the driving force distribution control apparatus of the said 2nd Example performs. It is a whole system figure which shows the power train provided with 3rd Example of the driving force distribution control apparatus of the four-wheel drive vehicle of this invention. It is a flowchart which shows the torque distribution control which the torque distribution controller of the driving force distribution control apparatus of the said 3rd Example performs. It is a whole system figure which shows the power train provided with 4th Example of the driving force distribution control apparatus of the four-wheel drive vehicle of this invention. It is a flowchart which shows the torque distribution control which the torque distribution controller of the driving force distribution control apparatus of the said 4th Example performs. It is a whole system figure which shows the power train provided with 5th Example of the driving force distribution control apparatus of the four-wheel drive vehicle of this invention. It is a flowchart which shows the torque distribution control which the torque distribution controller of the driving force distribution control apparatus of the said 5th Example performs. It is a time chart which shows the effect of the driving force distribution control by the driving force distribution control apparatus of each said Example at the time of start acceleration of a vehicle, and the time of intermediate acceleration after that.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Continuously variable transmission 3 Front differential 4 Rear differential 5 Right front wheel 6 Left front wheel 7 Right rear wheel 8 Left rear wheel 9 Torque distribution actuator 10 Torque distribution controller 10a Estimated main drive wheel allowable torque calculation part 10b Target transmission torque setting part 10c Actuator control section 10d Target transmission torque lower limit holding section 11 Right front wheel speed sensor 12 Left front wheel speed sensor 13 Right rear wheel speed sensor 14 Right rear wheel speed sensor 15 Accelerator opening sensor 16 Engine controller 17 Longitudinal acceleration detector 18 Wheel slip Detector 19 Gradient detector

Claims (5)

The output torque of the prime mover that is the drive source of the vehicle is transmitted to the main drive wheel that is one of the front wheels and the rear wheels, and the auxiliary drive wheel that is the other of the front wheels and the rear wheels via the torque distribution actuator. In the driving force distribution control device that controls the operation of the torque distribution actuator of the four-wheel drive vehicle that transmits the torque distribution between the main drive wheel and the sub drive wheel according to the vehicle state,
An estimated main driving wheel allowable torque calculating means, a target transmission torque setting means, and an actuator control means, each of which repeatedly performs processing at predetermined time intervals,
The estimated main driving wheel allowable torque calculating means calculates an estimated main driving wheel allowable driving torque based on the estimated load of the main driving wheel,
The target transmission torque setting means sets and stores a value obtained by subtracting the estimated main driving wheel allowable driving torque from the total driving torque based on the output torque of the prime mover as the target transmission torque to the auxiliary driving wheel, When a higher driving torque is required in the processing, if the rotational difference between the main driving wheel and the sub driving wheel is not greater than a predetermined value, the stored target transmission torque value is used as the target transmission torque to the sub driving wheel. Set,
The actuator control means controls the operation of the torque distribution actuator so as to transmit the target transmission torque set by the target transmission torque setting means to the auxiliary drive wheels. Distribution controller.   The target transmission torque setting means has a target transmission torque lower limit value, and sets the higher value of the set target transmission torque and the target transmission torque lower limit value as the target transmission torque again. The driving force distribution control device for a four-wheel drive vehicle according to claim 1. The driving force distribution control device comprises longitudinal acceleration detection means for detecting longitudinal acceleration of the vehicle,
2. The main driving wheel estimated allowable torque calculating means corrects the estimated load of the main driving wheel according to the magnitude of longitudinal acceleration of the vehicle detected by the longitudinal acceleration detecting means. Driving force distribution control device for four-wheel drive vehicles. The driving force distribution control device comprises main driving wheel slip detection means for detecting slip of the main driving wheel of the vehicle,
The main driving wheel estimated allowable torque calculating means reduces the estimated allowable torque of the main driving wheel when the main driving wheel slip detecting means detects a slip of the main driving wheel. A drive force distribution control device for a four-wheel drive vehicle as described. The main drive wheel is a front wheel of the vehicle;
The driving force distribution control device comprises an ascending slope detecting means for detecting an ascending slope of a road surface on which the vehicle is traveling,
2. The four-wheel drive vehicle according to claim 1, wherein the target transmission torque setting means sets the target transmission torque to be larger than when there is no gradient when the ascending gradient detecting means detects the ascending gradient. Driving force distribution control device.

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