JP2006218921A - Traction control device for front and rear wheels driving vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traction control device for a four-wheel drive vehicle capable of suppressing deceleration feeling at four-wheel slip and failure of acceleration performance at slip dissolution. <P>SOLUTION: The traction control device 40 is provided with an average wheel speed calculation means 41 for calculating a front wheel average wheel speed Vf, a rear wheel average wheel speed Vr and a four-wheel average wheel speed Va; a presumption vehicle body speed calculation means 42 for calculating a presumption vehicle body speed Vb; an engine traction control means 43 for performing engine traction control based on difference of the four-wheel average wheel speed Va and the presumption vehicle body speed Vb; and a control object selection means 44 for comparing the front wheel average wheel speed Vf with the rear wheel average wheel speed Vr and selecting the wheel at the side with the large average wheel speed. Further, the traction control device 40 transmits wheel information or the like selected by the control object selection means 44 to a brake control device 30 for a vehicle and performs brake traction control only relative to the selected wheel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a traction control device for front and rear wheel drive vehicles that performs both engine traction control and brake traction control.

  In recent years, a center differential that transmits driving torque from the engine to the front and rear wheels, and a torque split device that arbitrarily changes the distribution (torque distribution) of driving torque that is transmitted to the front and rear wheels by the center differential are provided. A four-wheel drive vehicle is known. In such a four-wheel drive vehicle, for example, when the front wheel slips, the torque split device increases the torque distribution to the rear wheel, thereby obtaining a grip force and realizing a comfortable driving. A traction control device is provided for controlling the engine so as to quickly exit the slip state by reducing the engine output when everything slips.

  As the traction control device as described above, conventionally, detection of slip of four wheels is performed by comparing the average value of the wheel speeds of the four wheels with the estimated vehicle speed calculated based on the acceleration detected by the longitudinal acceleration sensor. In some cases, so-called engine traction control is performed such that the engine output is controlled based on the slip amount calculated at that time. (See Patent Document 1). However, this technology only reduces the engine output when it is determined that the four wheels have slipped. Therefore, the engine traction control becomes excessive, and there is a feeling of stall or sacrifice of acceleration performance after the slip state is released. It was.

  On the other hand, as shown in FIG. 5, when the four wheels slip, there is a technique for performing so-called brake traction control in which braking is applied to each wheel in addition to engine traction control. According to this technology, compared to the technology that only performs engine traction control when the four wheels slip, the amount of engine traction control is not excessive, and the feeling of stalling can be suppressed to some extent because the brake traction control is performed. It has become. However, in this technique, normally, when one of the average wheel speed of the front wheels and the average wheel speed of the rear wheels is separated from the estimated vehicle speed by a predetermined amount (approximately 0 in the figure) or more, The engine traction control is performed based on the average wheel speed of the rear wheel. Further, in this technique, when the larger of the average wheel speed of the front wheels and the average wheel speed of the rear wheels is more than the predetermined amount X from the estimated vehicle body speed, the brake traction control is performed for each of the front wheels and the rear wheels. By performing the above, both the average wheel speeds of the front wheels and the rear wheels are brought close to the estimated vehicle body speed.

JP-A-1-113665

  However, even in the technology that performs both engine traction control and brake traction control when the four wheels slip as described above, the engine torque is reduced based on the larger one of the front and rear average wheel speeds. As a result, there was a problem that the feeling of stall and the acceleration performance at the time of slip elimination were deteriorated accordingly. In addition, since brake traction control is executed for both the front wheels and the rear wheels, the average wheel speed of the four wheels is thereby lowered, resulting in a feeling of stalling and a deterioration in acceleration performance at the time of slip cancellation. It was.

  Accordingly, an object of the present invention is to provide a traction control device for a front and rear wheel drive vehicle that can suppress a feeling of stall when the four wheels (front and rear drive wheels) slip and deterioration of acceleration performance when the slip is eliminated. To do.

  The invention according to claim 1 of the present invention that solves the above-mentioned problems is a center differential that transmits driving torque from the engine to both the front wheel side and the rear wheel side, and a wheel speed that detects the wheel speed of the front and rear wheels. In a traction control device for a front and rear wheel drive vehicle comprising a detection means and a longitudinal acceleration detection means for detecting the longitudinal acceleration of the vehicle body, from the wheel speed of each wheel detected by the wheel speed detection means, An average wheel speed calculating means for calculating an average wheel speed, an average wheel speed on the rear wheel side and an average wheel speed of the front and rear wheels, and an estimated vehicle speed for calculating an estimated vehicle speed from at least the acceleration detected by the longitudinal acceleration detecting means A calculating means, an average wheel speed of the front and rear wheels calculated by the average wheel speed calculating means, an estimated vehicle speed calculated by the estimated vehicle speed calculating means, The engine traction control means for performing engine traction control based on the determined slip amount, the average wheel speed on the front wheel side calculated by the average wheel speed calculation means and the average wheel speed on the rear wheel side are compared, and the average wheel speed is calculated. Brake traction control means for performing brake traction control only on the larger wheel.

  Here, the “slip amount” refers to a value indicating the degree of slip, such as the difference between the wheel speed and the estimated vehicle body speed and the slip rate. Also, “engine traction control” refers to control that fluctuates the engine output so that the difference between the average wheel speed of the front and rear wheels and the estimated vehicle body speed is within a predetermined value, and “brake traction control” For example, the control means that the brake torque (brake control pressure) is changed so that the difference between the average wheel speed on the larger side and the estimated vehicle body speed is within a predetermined value.

  According to the first aspect of the present invention, since the average wheel speed of the front and rear wheels is used for engine traction control, it is excessive as compared with the control using the larger average wheel speed as in the prior art. Engine traction control can be suppressed. In addition, by performing brake traction control only on the wheel having the higher average wheel speed (the wheel having the larger slip amount), the driving torque from the engine is applied to the wheel that is performing brake traction control by the center differential (that is, , A wheel having a large slip amount) can be transmitted to a wheel on which brake traction control is not performed. That is, the engine output can be effectively utilized by allocating the driving torque from the engine more largely to the wheels having a small slip amount or not slipping.

  The invention according to claim 2 is the traction control device for front and rear wheel drive vehicles according to claim 1, wherein the brake traction control means includes an average wheel speed on the front wheel side and an average wheel speed on the rear wheel side. So as to reduce the difference between the average wheel speed on the front wheel side and the average wheel speed on the rear wheel side by applying a brake torque corresponding to the difference between the average wheel speed and the average wheel speed on the rear wheel side. It is characterized by controlling to.

  According to the invention described in claim 2, since the brake torque corresponding to the difference between the average wheel speed on the front wheel side and the average wheel speed on the rear wheel side is applied to the wheel on the side with the higher average wheel speed, Brake with a weak brake torque, that is, a minimum required brake torque that does not significantly affect the deceleration of the vehicle body, compared to the one that applies the brake torque according to the difference between the average wheel speed on the larger side and the estimated vehicle body speed Traction control can be performed. Thereby, the feeling of stall at the time of a slip can be suppressed, and the acceleration performance after slip cancellation can be improved.

  According to the first aspect of the present invention, the engine traction control is performed based on the average wheel speed of the front and rear wheels, and the brake traction control is performed only on the wheel having the larger slip amount. Since the engine output can be effectively utilized, for example, it is possible to suppress a feeling of stall during a four-wheel slip in a four-wheel drive vehicle and a deterioration in acceleration performance after the slip is eliminated.

  According to the second aspect of the present invention, the brake torque corresponding to the difference between the average wheel speed on the front wheel side and the average wheel speed on the rear wheel side is applied to the wheel on the side with the higher average wheel speed. The brake traction control can be performed with the minimum necessary brake torque that does not significantly affect the deceleration of the vehicle, and the feeling of stalling at the time of slip and the acceleration performance after the slip is eliminated can be further suppressed.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a configuration diagram (a) showing a drive system of a vehicle equipped with a traction control device according to the present embodiment, and a configuration diagram (b) showing a brake system, and FIG. 2 is a block diagram showing the configuration of the traction control device. FIG.

  As shown in FIG. 1A, the vehicle CR is a four-wheel drive vehicle mainly including an engine ENG, a transmission TM, and a center differential Dc. As shown in FIG. A wheel speed sensor (wheel speed detection means) 10, a longitudinal acceleration sensor (longitudinal acceleration detection means) 20, a vehicle brake control device 30 and a traction control device 40 are provided.

  The engine ENG is configured such that the output varies according to the amount of depression of an accelerator pedal (not shown), and the output varies depending on a control signal from the traction control device 40. The drive torque from the engine ENG is transmitted to the center differential Dc via the transmission TM. Note that any method may be used for changing the output. For example, a method for adjusting the opening of the throttle valve, a method for adjusting the supercharging pressure, or the like may be employed.

  As is well known, the center differential Dc is a differential mechanism, and the driving torque from the engine ENG is obtained by using left and right front wheels Tf, Tf (hereinafter also simply referred to as “front wheels Tf”) and left and right rear wheels Tr of the vehicle CR. , Tr (hereinafter, also simply referred to as “rear wheel Tr”) is distributed and transmitted at a predetermined ratio. Further, the center differential Dc not only has a function of distributing the driving torque in the front-rear direction as described above, but also, for example, when the vehicle CR turns a curve, the axle Af on the front wheel Tf side and the axle Ar on the rear wheel Tr side For example, when the front wheel Tf is braked, the driving torque that has been transmitted to the front wheel Tf is added to the driving torque that has been applied to the rear wheel Tr. The function of increasing the drive torque applied to the wheel Tr is exhibited.

  The wheel speed sensor 10 is a sensor that detects the wheel speed of each wheel Tf, Tf, Tr, Tr (hereinafter also simply referred to as “wheel T”), and is provided for each wheel T. . Each wheel speed sensor 10 is connected to the traction control device 40, whereby the traction control device 40 can acquire all wheel speeds of the four wheels (four wheels) T.

  The longitudinal acceleration sensor 20 is a sensor that detects acceleration in the longitudinal direction of the vehicle CR (hereinafter referred to as “longitudinal acceleration”). The longitudinal acceleration sensor 20 is connected to the traction control device 40, whereby the traction control device 40 can acquire the longitudinal acceleration of the vehicle CR.

  The vehicle brake control device 30 is for appropriately controlling the braking force (brake hydraulic pressure) applied to each wheel T of the vehicle CR, and includes a hydraulic unit 31 provided with oil passages and various parts, It mainly includes a control device 32 for appropriately controlling various components in the pressure unit 31. Note that the brake hydraulic pressure output from the hydraulic unit 31 is supplied to the wheel cylinders H provided on the wheels T via pipes, and is supplied to the wheels T via the wheel cylinders H. Brake hydraulic pressure is applied to the provided wheel brakes FL, RL, FR, RR.

  Further, a traction control device 40 is connected to the control device 32 of the vehicle brake control device 30, so that signals (control target data and front and rear wheel speed difference data described later) transmitted from the traction control device 40 are thereby transmitted. Based on this, the control device 32 of the vehicle brake control device 30 performs brake traction control. That is, the control device 32 also functions as a part of the traction control device 40. The function of the control device 32 that performs brake traction control will be described later.

  Here, the control device 32 includes, for example, a CPU, a RAM, a ROM, and an input / output circuit, and performs various arithmetic processes based on signals from the traction control device 40 and programs and data stored in the ROM. To execute brake traction control. Similarly, the traction control device 40 includes a CPU, a RAM, a ROM, and an input / output circuit.

  The traction control device 40 determines whether the slip state is a two-wheel slip (a state in which only the front wheel Tf or the rear wheel Tr is slipped) or a four-wheel slip (all the wheels T) based on a signal from each wheel speed sensor 10. Has a function of determining whether or not a slip occurs. Since the present invention has a feature in the control at the time of four-wheel slip, the control of the two-wheel slip is assumed to be the same as the conventional one, and the description thereof will be omitted.

Below, the function for exiting the state of 4 wheel slip among the functions which comprise the traction control apparatus 40 is demonstrated in detail.
As shown in FIG. 2, the traction control device 40 includes an average wheel speed calculation means 41, an estimated vehicle body speed calculation means 42, an engine traction control means 43, a control object selection means 44, and a front and rear wheel speed difference calculation means 45. And mainly.

  The average wheel speed calculation means 41 calculates the average wheel speed Vf of the front wheel Tf, the average wheel speed Vr of the rear wheel Tr, and the average wheel speed Va of the four wheels T from the wheel speed of each wheel T detected by each wheel speed sensor 10. It has a function to calculate. In the following description, for convenience, the average wheel speed Vf of the front wheel Tf is also referred to as “front wheel average wheel speed Vf”, and the average wheel speed Vr of the rear wheel Tr is also referred to as “rear wheel average wheel speed Vr”. The average wheel speed Va is also referred to as “four-wheel average wheel speed Va”. The average wheel speed calculating means 41 outputs the calculated four-wheel average wheel speed Va to the engine traction control means 43, and calculates the calculated front wheel average wheel speed Vf and the rear wheel average wheel speed Vr as control target selecting means. 44 and the front-rear wheel speed difference calculating means 45.

  The estimated vehicle speed calculation means 42 has a function of calculating an estimated vehicle speed (estimated vehicle speed) Vb from each wheel speed detected by each wheel speed sensor 10 and the longitudinal acceleration detected by the longitudinal acceleration sensor 20. ing. Note that any method may be used as a method for calculating the estimated vehicle body speed. For example, for example, the signal from each wheel speed sensor 10 is a normal value (a value in a non-slip state). When the estimated vehicle speed is calculated with reference to these signals and each signal indicates an abnormal value (a value in a slipping state), the longitudinal acceleration sensor 20 The estimated vehicle body speed may be calculated by arbitrarily referring to the longitudinal acceleration of the vehicle. The estimated vehicle speed calculation means 42 is configured to output the calculated estimated vehicle speed Vb to the engine traction control means 43 and the control object selection means 44.

  The engine traction control means 43 performs engine traction control based on the difference between the four-wheel average wheel speed Va calculated by the average wheel speed calculation means 41 and the estimated vehicle speed Vb calculated by the estimated vehicle speed calculation means 42. It has a function. Specifically, the engine traction control means 43 sets the engine torque when the difference between the four-wheel average wheel speed Va and the estimated vehicle body speed Vb exceeds the first threshold value β shown in FIG. It functions to decrease with a decrease according to the difference between the average wheel speed Va and the estimated vehicle speed Vb. Further, the engine traction control means 43 performs the above-described engine traction control (control for reducing the engine output) when the difference between the four-wheel average wheel speed Va and the estimated vehicle body speed Vb is equal to or less than the first threshold value β. End.

  The control object selection means 44 includes the front wheel average wheel speed Vf, the rear wheel average wheel speed Vr and the four wheel average wheel speed Va calculated by the average wheel speed calculation means 41 and the estimated vehicle body speed Vb calculated by the estimated vehicle body speed calculation means 42. And the function of selecting a control object (front wheel Tf or rear wheel Tr) for brake traction control. Specifically, when the difference between the four-wheel average wheel speed Va and the estimated vehicle body speed Vb exceeds the second threshold value α (see FIG. 3), the control target selection unit 44 determines the average of the front wheels at that time. The wheel speed Vf is compared with the rear wheel average wheel speed Vr, the larger wheel T (rear wheel Tr in FIG. 3) is selected as a control target, and the selected rear wheel Tr is used as control target data for vehicle braking. By outputting to the control device 32 of the control device 30, the brake traction control is started. Further, the control object selection means 44 outputs the control object data once, and then the condition (the difference between the four-wheel average wheel speed Va and the estimated vehicle body speed Vb exceeds the second threshold value α). When the condition (condition) is not satisfied, the brake traction control is terminated by outputting a stop command to the control device 32 of the vehicle brake control device 30.

  When the front and rear wheel speed difference calculating means 45 receives the front wheel average wheel speed Vf and the rear wheel average wheel speed Vr output from the average wheel speed calculating means 41, these differences are calculated as absolute values, and the difference is calculated as the front and rear wheels. The speed difference data is output to the control device 32 of the vehicle brake control device 30.

  The control device 32 of the vehicle brake control device 30 includes control target data (rear wheel Tr) output from the control target selection means 44, and front and rear wheel speed difference data output from the front and rear wheel speed difference calculation means 45. Based on the above, it has a function of performing brake traction control. Specifically, when the control device 32 receives the control target data (rear wheel Tr) from the control target selection unit 44, the control device 32 determines a brake control pressure corresponding to the front and rear wheel speed difference data (for example, a predetermined difference in the front and rear wheel speed difference). (Value multiplied by a coefficient) is calculated, and the calculated brake control pressure is applied only to the rear wheel Tr represented by the control target data.

  Then, the control device 32 applies the brake control pressure only to the rear wheel Tr in this way, so that the driving torque applied to the rear wheel Tr is slipped by the center differential Dc (average wheel speed and estimated vehicle body speed). Is transmitted to the front wheel Tf having a small difference (see FIG. 4B). Therefore, as shown by the white arrow in FIG. 3, a phenomenon occurs in which the average front wheel speed Vf increases while the average rear wheel speed Vr decreases, and the difference between the front and rear wheel speeds decreases rapidly. Thus, brake traction control is performed. The control device 32 also has a function of terminating the brake traction control when receiving the stop command described above from the control target selection unit 44.

  In the present embodiment, the control object selection means 44, the front and rear wheel speed difference calculation means 45, and the control device 32 of the vehicle brake control device 30 are referred to as “brake traction control means”. Is equivalent to. However, the present invention is not limited to this. For example, by providing the control device 32 of the vehicle brake control device 30 with the functions of the control target selection means 44 and the front and rear wheel speed difference calculation means 45 in this embodiment, Only the control device 32 may be used as the brake traction control means.

Next, traction control at the time of four-wheel slip by the traction control device 40 and the control device 32 of the vehicle brake control device 30 will be described.
First, engine traction control will be described.

  As shown in FIG. 3, when an attempt is made to start by depressing an accelerator pedal (not shown) from a state in which the vehicle CR is stopped, first, from the acceleration detected by the vehicle CR slightly accelerating when starting. An estimated vehicle speed Vb is calculated. In the present embodiment, the control is executed on the assumption that the vehicle CR advances at the estimated vehicle body speed Vb obtained first. However, the present invention is not limited to this, and is periodically estimated. The vehicle body speed Vb may be updated.

  Then, when the vehicle starts moving, the four-wheel T starts to slip, and when the average four-wheel wheel speed Va exceeds a value obtained by adding the first threshold value β to the estimated vehicle body speed Vb, engine traction control is started (time T1). ). In this engine traction control, the reduction range of the engine torque is determined based on the difference between the four-wheel average wheel speed Va and the estimated vehicle body speed Vb. Therefore, as in the conventional case shown in FIG. Compared to the calculation of the reduction range of the engine torque based on the speed (rear wheel average wheel speed in FIG. 5), the reduction speed of the engine torque can be made moderate. Then, by starting the engine traction control in this way, the engine torque is controlled so as to increase while being controlled at an increase rate smaller than the initial increase rate, or to decrease at a moderate decrease rate. It will be.

  The engine traction control ends when the four-wheel average wheel speed Va becomes equal to or less than the estimated vehicle body speed Vb plus the first threshold value β.

Next, brake traction control that is executed independently of the engine traction control described above will be described.
As shown in FIG. 3, when the vehicle CR in a stopped state is started, first, the estimated vehicle body speed Vb is calculated as in the engine traction control. When the vehicle starts moving, the four-wheel T starts to slip, and when the four-wheel average wheel speed Va exceeds the estimated vehicle body speed Vb plus the second threshold value α, the brake traction control is started (time T2). . Since this brake traction control is performed only on the rear wheel Tr, as described above, when the driving torque on the rear wheel Tr side moves to the front wheel Tf, the brake traction control is conspicuous in the portion indicated by the white arrow in FIG. As shown in, the rear wheel average wheel speed Vr gradually decreases, and the front wheel average wheel speed Vf gradually increases. As a result, the average wheel speed difference between the front wheel Tf and the rear wheel Tr converges to become substantially zero. Further, by converging the front wheel average wheel speed Vf and the rear wheel average wheel speed Vr so as to approach each other in this way, the four wheel average wheel speed Va is changed to the conventional control (front wheel average wheel speed and Compared to the curve of the average wheel speed of four wheels passing between the average wheel speeds of the rear wheels (not shown), the vehicle will rise slowly and not fluctuate up and down. Can be suppressed.

  In addition, as described above, when the vehicle CR makes a curve, the slip amount of the rear wheel Tr is larger than the slip amount of the front wheel Tf by performing brake traction control only on the rear wheel Tr as described above. It is possible to suppress the degree of oversteer phenomenon (hereinafter referred to as “oversteer amount”). That is, in the prior art, as shown in FIG. 4 (a), by applying the brake control pressure evenly to all four wheels T, the driving torque of the front wheels Tf and the rear wheels Tr is reduced, so that the slip is small. Alternatively, the force of pulling the vehicle CR by the front wheel Tf that does not slip is weakened, and the amount of oversteer is increased. On the other hand, in this embodiment, as shown in FIG. 4B, only the driving torque of the rear wheels Tr having a large slip amount is reduced by the brake control pressure, and the driving torque of the front wheels Tf having a small slip amount is increased. Therefore, the force for pulling the vehicle CR is increased by the front wheel Tf having a small slip amount, and the oversteer amount can be kept small. If the driving torque of the front wheels Tf is excessively increased, an understeer phenomenon occurs on the contrary, so that the driving torque of the front wheels Tf, which increases when the driving torque is transmitted from the rear wheels Tr, for example, becomes a predetermined value or more. In this case, the brake control pressure may be applied to the front wheel Tf as appropriate, or the control pressure applied to the rear wheel Tr may be reduced.

  As shown in FIG. 3, the above-described brake traction control is terminated when the four-wheel average wheel speed Va decreases to a value obtained by adding the second threshold value α to the estimated vehicle body speed Vb (time). T3). If the above-mentioned conditions are satisfied thereafter, brake traction control is executed (time T4 to T5).

  Further, by executing the traction control (engine traction control and brake traction control) as described above, as shown in FIG. 3, in this embodiment, the front wheel average wheel speed Vf and the rear wheel average wheel speed Vr are both Before reaching the estimated vehicle speed Vb, the vehicle starts to rise again. On the other hand, as shown in FIG. 5, conventionally, the front wheel average wheel speed Vf and the rear wheel average wheel speed Vr both start increasing again after reaching the estimated vehicle body speed Vb. That is, in the conventional traction control, the slip rate [in the case of the front wheel Tf; (Vf−Vb) / Vb × 100] reaches 0%, but in the traction control of this embodiment, the slip rate is lower than 0. It is kept at a large predetermined value (a value at which acceleration efficiency is considered to be the best).

According to the above, the following effects can be obtained in the present embodiment.
By using the average wheel speed of the four wheels T to perform engine traction control, excessive engine traction control can be suppressed as compared to the control using the larger average wheel speed as in the past. The feeling of stalling given to the driver can be suppressed.

  By performing the brake traction control only on the rear wheel Tr having the larger slip amount, the drive torque from the engine ENG does not perform the brake traction control from the rear wheel Tr on which the brake traction control is performed by the center differential Dc. For example, even when the rear wheel Tr is likely to slip when turning a curve, the amount of oversteer is kept small, and the operation of the vehicle CR is easily performed. It becomes possible. In addition, since the slip ratio can be maintained at a value at which the acceleration efficiency becomes the best, the vehicle CR can be accelerated well when the slip is eliminated.

Since the brake torque according to the average wheel speed difference between the front wheel Tf and the rear wheel Tr is applied to the rear wheel Tr on the side where the average wheel speed is larger, the minimum necessary amount that does not significantly affect the deceleration of the vehicle CR. The brake traction control can be performed with the brake torque of, and the stalling feeling at the time of slip and the acceleration performance after slip cancellation can be further suppressed.
Since the brake traction control is started when the average wheel speed of the four wheels exceeds a value obtained by adding the second threshold value α to the estimated vehicle body speed Va, the average of the wheels having the higher average wheel speed as in the conventional case is used. The time during which the brake traction control is performed is shorter than when the wheel speed (the rear wheel average wheel speed in FIG. 5) exceeds the estimated vehicle body speed by adding a predetermined amount X to start the brake traction control. It is possible to reduce the engine torque by reducing the engine torque.

As mentioned above, this invention is implemented in various forms, without being limited to the said embodiment.
In the present embodiment, the control device 32 of the vehicle brake control device 30 mainly performs the brake traction control based on the conditions derived by the traction control device 40, but the present invention is not limited to this. Absent. For example, the function related to the brake traction control of the control device 32 may be transferred to the traction control device 40 so that the traction control device 40 appropriately activates the vehicle brake control device 30 to perform the brake traction control.
In this embodiment, the difference between the wheel speed of the driving wheel and the estimated vehicle body speed is used as the slip amount. However, the present invention is not limited to this, and for example, a slip ratio that is a ratio between the wheel speed and the estimated vehicle body speed is set. It may be used.

FIG. 2 is a configuration diagram (a) showing a drive system of a vehicle equipped with a traction control device according to the present embodiment, and a configuration diagram (b) showing a brake system. It is a block diagram which shows the structure of a traction control apparatus. It is a time chart which shows the relationship between the engine torque of the vehicle which concerns on this embodiment, each wheel speed, an estimated vehicle body speed, and brake control pressure. It is a figure which shows the oversteer phenomenon which arises when a rear wheel slips when a vehicle curves, and is a top view (a) which shows the conventional oversteer phenomenon, and a top view which shows the oversteer phenomenon of this embodiment ( b). It is a time chart which shows the relationship between the engine torque of a conventional vehicle, each wheel speed, an estimated vehicle body speed, and brake control pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wheel speed sensor 20 Longitudinal acceleration sensor 30 Vehicle brake control apparatus 31 Hydraulic unit 32 Control apparatus 40 Traction control apparatus 41 Average wheel speed calculation means 42 Estimated vehicle body speed calculation means 43 Engine traction control means 44 Control object selection means 45 Front and rear wheels Speed difference calculation means CR vehicle Dc Center differential ENG Engine FL Wheel brake H Wheel cylinder T Wheel TM Transmission Tf Front wheel Tr Rear wheel Vf Front wheel average wheel speed Vr Rear wheel average wheel speed Va Four wheel average wheel speed Vb Estimated vehicle speed

Claims (2)

A center differential that transmits drive torque from the engine to both the front and rear wheels,
Wheel speed detecting means for detecting wheel speeds of the front and rear wheels;
A longitudinal acceleration detecting means for detecting longitudinal acceleration of a vehicle body, and a traction control device for a front and rear wheel drive vehicle,
From the wheel speed of each wheel detected by the wheel speed detection means, average wheel speed calculation means for calculating the average wheel speed on the front wheel side, the average wheel speed on the rear wheel side, and the average wheel speed of the front and rear wheels;
Estimated vehicle body speed calculating means for calculating an estimated vehicle body speed from at least the acceleration detected by the longitudinal acceleration detecting means;
Engine traction control means for performing engine traction control based on a slip amount determined from the average wheel speed of the front and rear wheels calculated by the average wheel speed calculation means and the estimated vehicle body speed calculated by the estimated vehicle body speed calculation means; ,
Brake traction control means for comparing the front wheel average wheel speed calculated by the average wheel speed calculation means and the rear wheel average wheel speed, and performing brake traction control only for the wheel having the higher average wheel speed. And a traction control device for a front and rear wheel drive vehicle. A traction control device for a front and rear wheel drive vehicle according to claim 1,
The brake traction control means includes
The average wheel speed on the front wheel side is provided by applying a braking torque corresponding to the difference between the average wheel speed on the front wheel side and the average wheel speed on the rear wheel side to the wheel on the side with the higher average wheel speed. And a traction control device for front and rear wheel drive vehicles, characterized in that control is performed to reduce the difference between the average wheel speed on the rear wheel side.

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