JP2008215432A - Vehicular differential limiting force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly execute differential limiting force control superior in straightly advancing stability in response to a vehicle speed, in various vehicles different in vehicle specifications. <P>SOLUTION: Assuming that a yaw rate γ of a vehicle is expressed by an expression (4)γ = Gy × äV/(1 +AV<SP>2</SP>)} determined based on various vehicle specifications, a correction factor (k) is calculated in response to an actual vehicle speed V according to an expression (2)k = V/(1 + AV<SP>2</SP>) set based on its expression (4). Differential limiting force Mo is determined by multiplying its correction factor (k) and predetermined reference differential limiting force Mv, and differential limiting force of a differential limiting clutch 34 is controlled based on this differential limiting force Mo. Thus, the differential limiting force control superior in straightly advancing stability is properly executed in response to the vehicle speed V in the various vehicles different in the vehicle specifications. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a vehicle differential limiting force control device that controls a differential limiting force of a differential limiting device that limits the differential of a differential device that distributes driving force to left and right wheels.

In a vehicle drive device that distributes a driving force generated by a drive source such as an engine to left and right wheels via a differential device, the differential device is used to improve the operability and running stability of the vehicle. A differential limiting device for limiting the differential of the differential limiting device is provided, and the differential limiting force of the differential limiting device is controlled based on the vehicle speed. The device described in Patent Document 1 is an example, and the differential limiting force is set to 0 in order to prevent a braking phenomenon when turning at a low vehicle speed range, and stability during straight travel (straight-line stability) at a high vehicle speed range. ) Is provided with a predetermined differential limiting force.
Japanese Patent Application Laid-Open No. 5-96970

  However, such a conventional differential limiting force control device for a vehicle linearly controls the differential limiting force in the middle vehicle speed range when controlling the differential limiting force according to the vehicle speed in order to improve the straight running stability. After the increase, since it is only maintained at a constant value in the high vehicle speed region, appropriate control suitable for each vehicle is not always performed.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to appropriately perform differential limiting force control excellent in straight running stability according to the vehicle speed in various vehicles having different vehicle specifications. It is to make it.

  In order to achieve this object, the first aspect of the present invention is to provide the differential limiting force of the differential limiting device that limits the differential of the differential device that distributes the driving force to the left and right wheels in order to achieve the straight running stability of the vehicle. The differential limiting force control device for a vehicle that controls the differential limiting force Mo determined by using a predetermined reference differential limiting force Mv, a predetermined vehicle stability factor A, and a vehicle speed V as parameters. Is obtained according to the actual vehicle speed V, and the differential limiting force of the differential limiting device is controlled based on the differential limiting force Mo.

According to a second aspect of the present invention, in the differential limiting force control apparatus for a vehicle according to the first aspect, the differential limiting force Mo is expressed by the following equation using the reference differential limiting force Mv, the stability factor A, and the vehicle speed V: Characterized by 1).
Mo = Mv × {V / (1 + AV ² )} (1)

  According to a third aspect of the present invention, there is provided a vehicle differential limiter that controls the differential limiting force of the differential limiting device that limits the differential of the differential device that distributes the driving force to the left and right wheels in order to achieve linear stability of the vehicle (A) a storage device that stores a predetermined reference differential limiting force Mv; and (b) an arithmetic expression that is set in advance with the vehicle speed V as a parameter based on vehicle specifications. A correction coefficient calculating means for calculating a correction coefficient k according to the actual vehicle speed V, and (c) a differential limit for obtaining a differential limiting force Mo by multiplying the correction coefficient k and the reference differential limiting force Mv. And (d) controlling the differential limiting force of the differential limiting device based on the differential limiting force Mo.

According to a fourth aspect of the present invention, in the vehicle differential limiting force control apparatus according to the third aspect of the present invention, the correction coefficient k is determined according to the following equation (2) set using a predetermined vehicle stability factor A: It is characterized by.
k = V / (1 + AV ² ) (2)

The fifth aspect of the invention provides the vehicle differential limiting force control apparatus of the second invention or the fourth invention, the reference differential limiting force Mv, the reference vehicle speed V _b predetermined, limited slip differential at the reference vehicle speed V _b It is expressed by the following equation (3) using a predetermined set value M _b as a force and a predetermined stability factor A of the vehicle.
Mv = M _b × {(1 + AV _b ² ) / V _b } (3)

In the vehicle differential limiting force control device according to the first aspect of the present invention, the differential limiting force Mo determined with the reference differential limiting force Mv, the vehicle stability factor A, and the vehicle speed V as parameters is set according to the actual vehicle speed V. In order to control the differential limiting force based on the differential limiting force Mo, the differential limiting force control with excellent straight running stability in various vehicles having different vehicle specifications, such as stability factor A, is used for the vehicle speed V. Depending on the situation, it can be performed appropriately. That is, the yaw rate (yaw angular velocity) γ of the vehicle can be approximately expressed by the following equation (4) using a constant G _y determined for each vehicle according to the vehicle specifications: {V / (1 + AV ² )}, the differential limiting force Mo is expressed by the above equation (1) using {V / (1 + AV ² )} as in the second invention, for example. Mo is also proportional to the yaw rate γ. Accordingly, by appropriately setting the reference differential limiting force Mv that is a proportional constant according to, for example, the above equation (3), the differential control force Mo is appropriately controlled according to the change in the yaw rate γ accompanying the change in the vehicle speed V. can do.
γ = G _y × {V / (1 + AV ² )} (4)

  Note that the above equation (4) is merely an approximate equation, and it is possible to express the yaw rate γ by another arithmetic equation such as a finer arithmetic equation. In implementing the first invention, such an arithmetic equation for the yaw rate γ is used. Based on the above, the differential limiting force Mo may be determined by an arithmetic expression different from the expression (1).

  In the differential limiting force control apparatus for a vehicle according to the third aspect of the present invention, the correction coefficient k is calculated according to the actual vehicle speed V according to an arithmetic expression set in advance based on the vehicle specifications, and the correction coefficient k is predetermined. In order to obtain the differential limiting force Mo by multiplying the reference differential limiting force Mv, and to control the differential limiting force of the differential limiting device based on the differential limiting force Mo, By appropriately setting, the differential limiting force control excellent in straight running stability can be appropriately performed according to the vehicle speed V in various vehicles having different vehicle specifications.

In the fourth aspect of the invention, {V / (1 + AV ² )} is calculated as the correction coefficient k according to the equation (2), and the correction coefficient k = V / (1 + AV ² ) is multiplied by the reference differential limiting force Mv. In order to obtain the differential limiting force Mo, the differential limiting force Mo substantially coincides with the differential limiting force Mo expressed by the equation (1), and can be regarded as one embodiment of the second invention. Similar effects can be obtained.

  The above equation (2) is also based on the premise that the yaw rate γ is expressed by the above equation (4) .The equation (4) is only an approximate equation, and the yaw rate can be calculated using other equations such as more detailed equations. Since it is possible to represent γ, when the third invention is implemented, the correction coefficient k can be determined by an arithmetic expression different from the expression (2) based on the arithmetic expression of the yaw rate γ.

  The present invention is applied to control of the differential limiting force of the differential limiting device that limits the differential of the differential device that distributes the driving force to the left and right wheels, and the left and right wheels are rear wheels even if they are front wheels. May be. In the case of a front and rear wheel drive vehicle, the present invention may be applied only to the control of the differential limiting force of either the front wheel or the rear wheel, but the present invention is applied to the differential limiting force control of both the front wheel and the rear wheel. It is also possible to apply.

  The differential device transmits input torque to both wheels while allowing relative rotation of the left and right wheels. The differential device includes one input member and a pair of output members. Dynamic gear devices are widely used. The differential limiting device limits the differential by the differential device, that is, the relative rotation of the left and right wheels. In the present invention, a hydraulic differential limiting clutch capable of controlling the differential limiting force is preferably used. However, an electromagnetic clutch or the like can also be used. The differential limiting device may limit the relative rotation of a pair of output members (axles or the like) of the differential device, or may limit the relative rotation of one of the output members and the input member.

Reference differential limiting force Mv, as for example, the fifth invention, the predetermined reference vehicle speed V _b, the reference vehicle speed V differential limiting force in _b (set value) M _b, and a predetermined vehicle static The differential limiting force M _b is expressed by the above equation (3) using the stability factor A, and the differential limiting force M _b is obtained through experiments, simulations, and the like so as to obtain a predetermined straight-line stability regardless of the yaw rate γ at the reference vehicle speed V _b . Is set. The reference vehicle speed V _b is appropriately determined, for example, at 50 km / hour, 100 km / hour, or the like. The above equation (3) is also based on the premise that the yaw rate γ is expressed by the above equation (4), and when the yaw rate γ is expressed by another arithmetic expression, it depends on the arithmetic expression of the yaw rate γ. An arithmetic expression for the reference differential limiting force Mv is also set.

  In the first aspect of the invention, the differential limiting force Mo determined by, for example, the above equation (1) using the reference differential limiting force Mv, the vehicle stability factor A, and the vehicle speed V as parameters is obtained according to the actual vehicle speed V. For example, it is configured to include differential limiting force calculating means for calculating the differential limiting force Mo according to the actual vehicle speed V in accordance with an arithmetic expression such as the expression (1). A differential limiting force map corresponding to the equation (1) for obtaining the dynamic limiting force Mo is stored in advance, and the differential limiting force Mo is directly calculated from the map according to the actual vehicle speed V. You can also For example, the differential limiting force calculating means is preset with (a) a storage device storing a reference differential limiting force Mv and a vehicle stability factor A, and (b) the stability factor A and the vehicle speed V as parameters. Correction coefficient calculation means for calculating the correction coefficient k according to the actual vehicle speed V in accordance with the calculated calculation formula such as the formula (2), and (c) the correction coefficient k and the reference differential limiting force. The differential limiting force Mo can be calculated by multiplying by Mv.

The equation (4) that approximately represents the yaw rate γ is determined with the vehicle speed V only as a parameter on the assumption that the vehicle travels at a constant speed, and the equations (1) to (3) are based on the equation (4). Although are set respectively, yaw rate γ is acceleration or deceleration of the vehicle, or to change the driving conditions such as road gradient and crosswind change, (4) the constant G _y and the reference differential limiting force Mv, the reference vehicle speed The differential limiting force (set value) M _{b at} V _b is set to be large in consideration of such disturbances, for example. However, the reference differential limiting force Mv, the differential limiting force (set value) M _{b at} the reference vehicle speed V _b , or the differential limiting force Mo is used, for example, at the time of acceleration / deceleration, the throttle valve opening changing speed, braking force, brake It is possible to correct the operating force etc. as a parameter, or if information on the running condition such as road gradient and wind speed is available, it is possible to correct such a running condition as a parameter. Regardless of the conditions (disturbances), the differential limiting force Mo can be made as small as possible while ensuring a predetermined straight running stability.

  The differential limiting force may be controlled in a completely different manner from the differential limiting force control of the present invention except during straight traveling, that is, during turning, but the differential limiting force during straight traveling of the present invention may be controlled. Based on the control, it is also possible to perform control by correcting the differential control force using the operation angle of the steering wheel as a parameter during turning.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating a vehicle drive device 10 to which the present invention is preferably applied, and is for a front and rear wheel drive vehicle based on a front engine front wheel drive (FF). In FIG. 1, the driving force (torque) generated by the engine 12, which is a driving force source, is transmitted to the left and right via the automatic transmission 14, the front wheel differential gear device 16, and the pair of left and right front wheel axles 18L and 18R. While being transmitted to a pair of front wheels 20L, 20R, a central differential gear device (center differential) 22, a propeller shaft 24 as a driving force transmission shaft, a rear wheel driving force distribution device 26, and a pair of left and right rear wheel axles 28L. , 28R to the left and right rear wheels 30L, 30R.

  The engine 12 is, for example, an internal combustion engine such as a gasoline engine or a diesel engine that generates driving force by combustion of fuel injected in a cylinder. The automatic transmission 14 is a stepped automatic transmission (automatic transmission) that outputs, for example, the rotation input from the engine 12 by decelerating or increasing the speed at a predetermined gear ratio, and the forward shift stage, the reverse drive Either the gear stage or neutral is selectively established, and speed conversion is performed in accordance with the respective gear ratios. The input shaft of the automatic transmission 14 is connected to the output shaft of the engine 12 via a torque converter (not shown).

  As specifically shown in FIG. 2, the rear wheel driving force distribution device 26 includes a rear wheel differential gear device 32 and a hydraulic differential limiting clutch 34 that limits the differential of the differential gear device 32. In order to control the differential limiting force of the differential limiting clutch 34, that is, the clutch hydraulic pressure, a hydraulic circuit 36 and an electronic control unit 38 are provided. The rear wheel differential gear unit 32 corresponds to a differential unit. In this embodiment, a bevel gear type differential gear unit is used, and a pair of small gears 32 is rotated from a differential case 32c that is rotationally driven by the propeller shaft 24. Torque is transmitted to the pair of axles 28L and 28R via the gear and the large gear. The differential case 32c corresponds to an input member, and the pair of axles 28L and 28R corresponds to an output member. The differential limiting clutch 34 corresponds to a differential limiting device. In this embodiment, the differential limiting clutch 34 is disposed between the differential case 32c of the rear wheel differential gear device 32 and the right rear wheel axle 28R. The relative rotation (differential) is limited according to the clutch hydraulic pressure. The hydraulic circuit 36 includes an electromagnetic pressure regulating valve that electrically controls the clutch hydraulic pressure supplied to the differential limiting clutch 34, and the electromagnetic pressure regulating valve and the like are controlled by an electronic control unit 38. The hydraulic pressure is adjusted to a predetermined hydraulic pressure to generate a predetermined differential limiting force, or the differential hydraulic clutch 34 is released by draining the clutch hydraulic pressure.

  The electronic control unit 38 is a so-called microcomputer that includes a CPU, a ROM, a RAM, an input / output interface, and the like, and executes signal processing according to a program stored in advance in the ROM while using a temporary storage function of the RAM. The clutch hydraulic pressure, that is, the differential limiting force supplied to the differential limiting clutch 34 is controlled by controlling the excitation current supplied to the electromagnetic pressure regulating valve and the like provided in the hydraulic circuit 36. Regarding the control of the differential limiting force, the electronic control unit 38 functionally includes the storage device 50, the correction coefficient calculating unit 52, and the differential limiting force calculating unit 54 shown in FIG. The vehicle speed sensor 40 is supplied with a signal representing the vehicle speed V. The storage device 50 is configured by the ROM or other storage medium, and stores a predetermined vehicle stability factor A and a reference differential limiting force Mv.

The stability factor A is obtained in advance for each vehicle based on vehicle specifications and the like based on straight travel. The reference differential limiting force Mv, the reference vehicle speed V _b predetermined, predefined set value M _b, and said using the stability factor A as a differential limiting force at the reference vehicle speed V _b ( 3) It is a constant value obtained according to the equation. Equation (3) is based on the premise that the yaw rate γ of the vehicle is approximately expressed by Equation (4), and Equation (4) is determined based on various vehicle specifications. This is obtained based on Equation (5).

Further, the constant G _y in the equation (4) is defined by the following equation (6) based on the above equation (5). In this case, the disturbance moment M and the disturbance lateral force Y, taking into account the personality and running environment of the vehicle, by setting at a predetermined safety factor, it is possible to define a constant G _y at a constant value Thus, the yaw rate γ can be expressed by the equation (4) using only the vehicle speed V as a variable.

Here, the yaw rate γ represented by the equation (4) changes continuously and non-linearly, for example, as shown in FIG. 4, using the vehicle speed V as a parameter, and the vehicle specifications, the disturbance moment M, the disturbance lateral force, and so on. Depending on the set value of Y, etc., it differs from vehicle to vehicle or vehicle type as indicated by a solid line, a dashed line, or a broken line. In FIG. 4, the yaw rate γ gradually decreases at a predetermined vehicle speed or higher. However, the yaw rate γ is merely an example. For example, depending on how the individual vehicle specifications, the disturbance moment M, and the disturbance lateral force Y are set, for example, the predetermined vehicle speed or higher. Therefore, the yaw rate γ characteristic, that is, the constant G _y in the equation (4) varies depending on the individual vehicle and vehicle type.

Then, (4), since a proportional relationship between ^{{V / (1 + AV 2} )}, if indicated differential limiting force Mo in (1) using the ^{{V / (1 + AV 2} )}, This differential limiting force Mo is also proportional to the yaw rate γ. Therefore, by appropriately setting the reference differential limiting force Mv serving as a proportional constant, the differential control force Mo can be appropriately controlled according to the change in the yaw rate γ accompanying the change in the vehicle speed V. In that case, assuming that the appropriate differential limiting force Mo at the reference vehicle speed V _b is set as M _b on the assumption that the vehicle travels straight at a predetermined reference vehicle speed V _b , for example, 100 km / hour, (1) The equation becomes the following equation (7), and the above equation (3) can be obtained by rewriting this equation (7). The differential limiting force M _b is determined by experiments, simulations, or the like so as to obtain a predetermined straight-line stability regardless of the yaw rate γ at the reference vehicle speed V _b .
M _b = Mv × {V _b / (1 + AV _b ² )} (7)

In this embodiment, the constant G _y is set to a constant value with the disturbance moment M and the disturbance lateral force Y as design items. However, the disturbance moment M and the disturbance lateral force Y are left as variables, and actual measured values are used. with change under certain conditions constant G _y based on and external information like, on the basis of the yaw rate γ obtained according to the equation (4) based on such constant G _y, the reference differential limiting force Mv Can be set, or the reference differential limiting force Mv can be corrected by the disturbance moment M or the disturbance lateral force Y.

Returning to FIG. 3, the correction coefficient calculating means 52 and the differential limiting force calculating means 54 control the clutch hydraulic pressure of the differential limiting clutch 34 according to the vehicle speed V in order to achieve running stability when the vehicle is traveling straight ahead. Therefore, the correction coefficient calculation means 52 reads the stability factor A of the vehicle from the storage device 50, and calculates the correction coefficient k according to the equation (2) based on the vehicle speed V detected by the vehicle speed sensor 40. To do. The equation (2) is defined on the assumption that the yaw rate γ of the vehicle is expressed by the equation (4). Specifically, the step before calculating the differential limiting force Mo according to the equation (1). Then, {V / (1 + AV ² )} is calculated as the correction coefficient k.

The differential limiting force calculating means 54 calculates the differential limiting force Mo by multiplying the correction coefficient k = {V / (1 + AV ² )} and the reference differential limiting force Mv. This differential limiting force Mo substantially coincides with the differential limiting force Mo expressed by the equation (1). Based on the differential limiting force Mo, the electromagnetic pressure regulating valve of the hydraulic circuit 36 is controlled to adjust the clutch hydraulic pressure of the differential limiting clutch 34, so that the difference between the differential limiting clutch 34 and the vehicle speed V is controlled. The dynamic limiting force is appropriately controlled, and excellent linear stability can be obtained.

  Thus, in the vehicle differential limiting force control apparatus of the present embodiment, on the assumption that the yaw rate γ of the vehicle is expressed by the above-described equation (4) determined based on various vehicle specifications, By calculating the correction coefficient k according to the actual vehicle speed V according to the expression (2) set based on the expression (4), and multiplying the correction coefficient k by a predetermined reference differential limiting force Mv Since the differential limiting force Mo is obtained and the differential limiting force of the differential limiting clutch 34 is controlled based on the differential limiting force Mo, the differential limiting is excellent in straight running stability in various vehicles having different vehicle specifications. Force control is appropriately performed according to the vehicle speed V.

  In the above embodiment, the differential limiting force Mo is substantially calculated according to the equation (1). For example, this corresponds to the equation (1) for obtaining the differential limiting force Mo using the vehicle speed V as a parameter. A differential limiting force map as shown in FIG. 5 is stored in advance in the storage device 50 or the like, and the differential limiting force Mo is directly calculated from the differential limiting force map according to the actual vehicle speed V. good.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

It is the schematic explaining the structure of the vehicle drive device of the front-and-rear wheel drive vehicle to which this invention is applied suitably. FIG. 2 is a skeleton diagram illustrating a configuration of a rear wheel driving force distribution device in the vehicle driving device of FIG. 1. It is a block diagram explaining the function with which the electronic controller of FIG. 2 is provided regarding control of the differential limiting force of a differential limiting device. FIG. 3 is a diagram illustrating an example of a correspondence relationship between a yaw rate γ and a vehicle speed V, which are preconditions for differential limiting force control performed by the electronic control device of FIG. 2. It is a figure which shows an example of the differential limiting force map in the case of calculating directly the differential limiting force Mo according to the vehicle speed V.

Explanation of symbols

  30L, 30R: Rear wheels (left and right wheels) 32: Differential gear device for rear wheels (differential device) 34: Differential limiting clutch (differential limiting device) 50: Storage device 52: Correction coefficient calculation means 54: Difference Dynamic limit force calculation means

Claims (5)

Differential limiting force control for a vehicle that controls the differential limiting force of the differential limiting device that limits the differential of the differential device that distributes driving force to the left and right wheels in order to achieve stability when the vehicle is traveling straight ahead A device,
A differential limiting force Mo determined by using a predetermined reference differential limiting force Mv, a predetermined vehicle stability factor A, and a vehicle speed V as parameters is determined according to the actual vehicle speed V, and the differential limiting is performed. A differential limiting force control device for a vehicle, wherein the differential limiting force of the differential limiting device is controlled based on a force Mo. The differential limiting force Mo is determined by the following equation (1) using the reference differential limiting force Mv, the stability factor A, and the vehicle speed V: Mo = Mv × {V / (1 + AV ² )}・ (1)
The differential limiting force control device for a vehicle according to claim 1. Differential limiting force control for a vehicle that controls the differential limiting force of the differential limiting device that limits the differential of the differential device that distributes driving force to the left and right wheels in order to achieve stability when the vehicle is traveling straight ahead A device,
A storage device that stores a predetermined reference differential limiting force Mv;
Correction coefficient calculation means for calculating a correction coefficient k according to the actual vehicle speed V according to a calculation formula set in advance using the vehicle speed V as a parameter based on vehicle specifications;
Differential limiting force calculating means for calculating the differential limiting force Mo by multiplying the correction coefficient k and the reference differential limiting force Mv;
And controlling the differential limiting force of the differential limiting device based on the differential limiting force Mo. The correction coefficient k is determined according to the following equation (2) set using a predetermined vehicle stability factor A: k = V / (1 + AV ² ) (2)
The vehicle differential limiting force control device according to claim 3. The reference differential limiting force Mv, the reference vehicle speed V _b predetermined, the reference vehicle speed V _b set value predetermined as a differential limiting force in M _b, and a stability factor A predetermined vehicle Mv = M _b × {(1 + AV _b ² ) / V _b } expressed by the following equation (3): (3)
The differential limiting force control device for a vehicle according to claim 2 or 4, characterized in that:

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