JP2014118074A - Control unit of four-wheel-drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control unit of a four-wheel-drive vehicle capable of improving turning performance of a vehicle compared with an existing one.SOLUTION: When a four-wheel-drive vehicle is turning, an ECU determines whether a rotating speed Vi of an inner race of a front wheel is equal to or lower than a rotating speed Vo of an outer race (step S1). If a determination is made that the rotating speed Vi of the inner race of the front wheel is equal to or lower than the rotating speed Vo of the outer race, an electronic controlled coupling is controlled so that a driving force to be allocated to rear wheels can be decreased (for example, nullified) (step S2).

Description

  The present invention relates to a control device for a four-wheel drive vehicle.

  Conventional control devices for four-wheel drive vehicles include driving force distribution means for constantly and variably distributing driving force from a driving source to front and rear wheels of the vehicle, and distribution of driving force between the front and rear wheels based on the turning state of the vehicle. Control amount calculation means for calculating a turning-related control amount as a correction amount for the vehicle, steer characteristic determination means for determining the current steering characteristic of the vehicle, wheel speed detection means for detecting the wheel speeds of the front and rear wheels, and steer characteristic determination Depending on the combination of the steer characteristic determined by the means and the magnitude relationship between the wheel speeds of the front and rear wheels detected by the wheel speed detecting means, the turning correspondence control amount is applied to the increase correction side or the decrease correction side, and the corrected A driving force distribution control unit that controls the driving force distribution unit based on the driving force distribution is known.

JP 2007-261484 A

  However, such a conventional control device for a four-wheel drive vehicle can improve the turning performance of the vehicle depending on the timing of distributing the driving force to the front and rear wheels and the distribution ratio of the driving force at that timing. There was a problem that it might become impossible.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a control device for a four-wheel drive vehicle capable of improving the turning performance of the vehicle as compared with the conventional one. To do.

  In order to achieve the above object, the control device for a four-wheel drive vehicle of the present invention (1) a drive force capable of changing the distribution ratio of the drive force transmitted from the drive source to the main drive wheel and the slave drive wheel. In the control device for a four-wheel drive vehicle including a distribution mechanism, the slave drive wheel is provided on the condition that when the four-wheel drive vehicle is in a turning state, the rotation speed of the inner wheel of the steering wheel is equal to or lower than the rotation speed of the outer wheel. And a driving force distribution control unit for controlling the driving force distribution mechanism so as to reduce the driving force distributed to each other.

  With this configuration, the control device for a four-wheel drive vehicle according to the present invention distributes to the driven wheels at the initial stage of turning acceleration in which the rotation speed of the inner wheel of the steering wheel is equal to or lower than the rotation speed of the outer wheel when the vehicle is in a turning state. By reducing the driving force, the inner wheel of the steered wheel is slipped early.

  As a result, the torque difference between the inner wheel and the outer wheel increases, and the turning moment of the vehicle increases. Therefore, the control device for a four-wheel drive vehicle of the present invention can improve the turning performance of the vehicle as compared with the conventional one.

  In the control device for a four-wheel drive vehicle described in (1) above, (2) the driving force distribution control unit is configured to reduce the driving force distributed to the slave driving wheels, on the condition that the slave driving wheels are The driving force distribution mechanism may be controlled so that the driving force distributed to zero is zero.

  With this configuration, the control device for a four-wheel drive vehicle of the present invention can reduce the driving force distributed to the driven wheels at the beginning of turning acceleration.

  Further, in the control device for a four-wheel drive vehicle described in (1) or (2) above, (3) the drive force distribution control unit is configured such that when the four-wheel drive vehicle is in a turning state, the inner wheel of the steering wheel On the condition that the rotational speed of the outer wheel is higher than the rotational speed of the outer wheel, the driving force according to the difference between the rotational speed of the inner ring of the steering wheel and the rotational speed of the outer wheel, and the slip between the main driving wheel and the sub driving wheel You may make it control the said driving force distribution mechanism so that the higher driving force among the driving force according to a rate difference may be distributed to the said driven wheel.

  With this configuration, the control device for a four-wheel drive vehicle according to the present invention enables the inner wheel of the steering wheel to slip excessively when the rotation speed of the inner wheel of the steering wheel is higher than the rotation speed of the outer wheel when the vehicle is turning. In this case, since the driving force is distributed to the driven wheels so as to prevent the lateral force of the inner wheels of the steered wheels from being lowered, the turning performance of the vehicle can be improved compared to the conventional one.

  ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional one, the control apparatus of the four-wheel drive vehicle which can improve the turning performance of a vehicle can be provided.

It is a block diagram which shows the structure of the vehicle to which the control apparatus of the four-wheel drive vehicle which concerns on embodiment of this invention is applied. It is a flowchart which shows the driving force distribution operation | movement by ECU which comprises the control apparatus of the four-wheel drive vehicle which concerns on embodiment of this invention. It is a graph for demonstrating an effect | action of the control apparatus of the four-wheel drive vehicle which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, an example in which the control device for a four-wheel drive vehicle according to the present invention is applied to a so-called FF-type four-wheel drive vehicle of the front engine / front drive type will be described.

  As shown in FIG. 1, a four-wheel drive vehicle 1 includes an engine 10 as an internal combustion engine that generates a driving force, a transmission 11, and a front differential device (hereinafter simply referred to as “front differential”) 12. Transaxle 13, transfer device 14, left and right front wheels 15 L and 15 R, left and right drive shafts 16 L and 16 R, propeller shaft 17, electronic control coupling 18, rear differential device (hereinafter simply referred to as “rear differential”). 19), left and right rear wheels 20L, 20R, left and right drive shafts 21L, 21R, and an ECU (Electronic Control Unit) 23.

  In the present embodiment, the engine 10 is described as an inline 4-cylinder engine that uses gasoline as fuel. However, in the present invention, an inline 6-cylinder engine, a V-type 6-cylinder engine, V You may be comprised with various types of engines, such as a type | mold 12 cylinder engine or a horizontally opposed 6 cylinder engine.

  The fuel used for the engine 10 may be a hydrocarbon fuel such as light oil instead of gasoline, or an alcohol fuel obtained by mixing alcohol such as ethanol and gasoline.

  The transmission 11 is provided between the engine 10 and the front differential 12 so that the rotation of the engine 10 is changed and output to the front differential 12. The transmission 11 includes a torque converter 30, a gear unit 31 that forms a plurality of forward speeds and reverse speeds, and an output shaft 32.

  An output gear 33 is attached to one end of the output shaft 32 so as to be integrally rotatable. In the present embodiment, transmission 11 is described as an automatic transmission. However, in the present invention, it may be configured by a continuously variable transmission or the like.

  The front differential 12 includes a differential case 40, and the differential case 40 is rotatably supported by the housing 13a of the transaxle 13 via a bearing (not shown). A ring gear 41 that meshes with the output gear 33 is provided on the outer periphery of the differential case 40, and a pair of differential pinion gears 42 are attached in the differential case 40 so as to face each other.

  The pair of differential pinion gears 42 can revolve with the differential case 40 and can rotate with respect to the differential case 40. A pair of side gears 43 mesh with the pair of differential pinion gears 42. The pair of side gears 43 are connected to the front wheels 15L and 15R via the drive shafts 16L and 16R, respectively. In the present embodiment, the front wheels 15L and 15R constitute the main drive wheel and the steering wheel in the present invention.

  Thus, the front differential 12 is connected to the drive shafts 16L and 16R, and distributes and transmits the driving force output from the engine 10 via the transmission 11 to the front wheels 15L and 15R. The difference in rotational speed of the driving force is allowed.

  Further, front wheels 15L and 15R are connected to the drive shafts 16L and 16R, respectively, and the front wheels 15L and 15R rotate around the drive shafts 16L and 16R.

  The transfer device 14 is provided so as to be positioned in the rotational axis direction of the front differential 12. The rotational axis direction of the front differential 12 is the same as the rotational axis direction of the differential case 40 and the drive shafts 16L and 16R.

  A cylindrical boss 40 a protruding into the transfer device 14 is formed at the end of the differential case 40. The transfer device 14 includes a bevel gear 50 and an output pinion 51.

  The propeller shaft 17 is provided between the transfer device 14 and the electronic control coupling 18, and the tip of the propeller shaft 17 is connected to the output pinion 51 of the transfer device 14. The electronic control coupling 18 is connected to the propeller shaft 17 at the front end and is connected to the rear differential 19 at the rear end.

  The electronic control coupling 18 constitutes a driving force distribution mechanism, and operates according to the control current output from the ECU 23, whereby the torque generated from the engine 10 is transmitted to the front wheels 15L and 15R and the rear wheels 20L and 20R. Therefore, it is distributed steplessly in the range from 100: 0 to 50:50.

  The rear differential 19 includes a differential case 60, and a ring gear 61 that meshes with the drive pinion gear 18 a of the electronic control coupling 18 is provided on the outer periphery of the differential case 60.

  A pair of differential pinion gears 62 is attached in the differential case 60 so as to face each other. The pair of differential pinion gears 62 can revolve together with the differential case 60 and can rotate with respect to the differential case 60.

  A pair of side gears 63 are meshed with the pair of differential pinion gears 62, and the pair of side gears 63 are connected to the rear wheels 20L and 20R via the drive shafts 21L and 21R, respectively. In the present embodiment, the rear wheels 20L and 20R constitute the driven wheels in the present invention.

  Although not shown, the ECU 23 is configured by a microprocessor having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a flash memory, and an input / output port. Yes.

  A program for causing the microprocessor to function as the ECU 23 is stored in the ROM of the ECU 23. That is, when the CPU of the ECU 23 executes a program stored in the ROM using the RAM as a work area, the microprocessor functions as the ECU 23.

  In the present embodiment, on the input side of the ECU 23, wheel speed sensors 101FL, 101FR, 101RL, 101RR for detecting the rotational speeds of the drive shafts 16L, 16R, 21L, 21R, and a steering angle of a steering wheel (not shown) are detected. Various sensors such as a rudder angle sensor 102 are connected. Various control objects such as an electronic control coupling 18 are connected to the output side of the ECU 23.

  The ECU 23 constitutes a driving force distribution control unit that controls the electronic control coupling 18 by a control current output to the electronic control coupling 18. Specifically, the ECU 23 calculates the average rotational speed value Vf detected by the wheel speed sensors 101FL and 101FR and the average rotational speed value Vr detected by the wheel speed sensors 101RL and 101RR during normal times. It has become.

  Further, the ECU 23 calculates the slip ratio difference Ds (= (Vf−Vr) / Vr) between the front wheels 15L and 15R and the rear wheels 20L and 20R based on the calculated average values Vf and Vr, and calculates the calculated slip. The electronic control coupling 18 is controlled so that a value Gs × D obtained by multiplying the rate difference Ds by an experimentally optimally determined gain Gs is distributed to the rear wheels 20L and 20R as a value of the driving force Fs. Yes.

  Further, the ECU 23 determines that the rotational speed Vi of the inner wheel of the front wheels 15L and 15R (the front wheel 15R in the right turn state) when the four-wheel drive vehicle 1 is turning is the outer wheel (the front wheel 15L in the right turn state). ), The electronically controlled coupling 18 is controlled so that the driving force distributed to the rear wheels 20L and 20R is lower than normal (set to 0 in the present embodiment). It is like that.

  Here, the ECU 23 determines that the four-wheel drive vehicle 1 is in a turning state when the absolute value of the steering angle detected by the steering angle sensor 102 is, for example, 15 degrees or more. .

  On the other hand, the ECU 23 sets the rotational speed Vi of the inner wheels of the front wheels 15L and 15R on the condition that the rotational speed Vi of the inner wheels of the front wheels 15L and 15R is higher than the rotational speed Vo of the outer wheels when the four-wheel drive vehicle 1 is in a turning state. Between the driving force Fd according to the difference between the rotational speed Vo of the outer wheel and the outer wheel and the driving force Fs according to the slip ratio difference Ds between the front wheels 15L, 15R and the rear wheels 20L, 20R. The electronic control coupling 18 is controlled so as to be distributed to 20L and 20R.

  That is, the ECU 23 sets the rotation speed Vi of the inner wheels of the front wheels 15L and 15R and the outer wheel on the condition that the rotation speed of the inner wheels of the front wheels 15L and 15R is higher than the rotation speed of the outer wheels when the four-wheel drive vehicle 1 is in a turning state. A value Gd × Dd obtained by multiplying the difference Dd (= Vo−Vi) of the rotation speed Vo by a gain Gd determined optimally experimentally in advance is calculated as the driving force Fd distributed to the rear wheels 20L and 20R. ing.

  Further, the ECU 23 controls the electronic control coupling 18 so as to distribute the higher driving force of the driving force Fd calculated in this way and the driving force Fs during normal time to the rear wheels 20L and 20R. ing.

  The driving force distribution operation by the ECU 23 configured as described above will be described with reference to FIG. The driving force distribution operation described below is repeatedly executed on condition that the four-wheel drive vehicle 1 is in a turning state.

  First, the ECU 23 determines whether or not the rotation speed Vi of the inner rings of the front wheels 15L and 15R (denoted as “driving inner ring speed”) Vi is higher than the rotation speed of the outer ring (denoted as “driving outer ring speed” in the figure) Vo. Is determined (step S1).

  Here, when it is determined that the rotational speed Vi of the inner ring of the front wheels 15L and 15R is not higher than the rotational speed Vo of the outer ring, the ECU 23 distributes to the rear wheels 20L and 20R (denoted as “driven wheels” in the figure). The electronic control coupling 18 is controlled so that the driving force is zero (step S2), and the driving force distribution operation is terminated.

  On the other hand, when it is determined that the inner wheel rotational speed Vi of the front wheels 15L and 15R is higher than the outer wheel rotational speed Vo, the ECU 23 determines the difference between the inner wheel rotational speed Vi of the front wheels 15L and 15R and the outer wheel rotational speed Vo ( As a driving force Fd (denoted as “driven wheel driving force” in the figure) that distributes a value Gd × Dd obtained by multiplying Dd by a gain Gd to the rear wheels 20L and 20R Calculate (step S3).

  Next, the ECU 23 calculates a slip ratio difference Ds between the front wheels 15L and 15R and the rear wheels 20L and 20R, and multiplies the calculated slip ratio difference (denoted as “front and rear wheel slip ratio difference”) Ds by a gain Gs. The value Gs × Ds is calculated as the driving force Fs distributed to the rear wheels 20L, 20R (step S4).

  Next, the ECU 23 distributes the higher driving force of the driving force Fd calculated in step S3 and the driving force Fs calculated in step S4 to the rear wheels 20L and 20R (step S5), and ends the driving force distributing operation. To do.

  Here, the operation of the present embodiment will be described with reference to FIG. FIG. 3 shows the relationship between the steering angle of the steering and the driving force (driven wheel distribution ratio [%]) distributed to the rear wheels 20L and 20R, the steering angle of the steering, The relationship with the turning moment (yaw rate [deg / s]) of the drive vehicle 1 is shown. In FIG. 3, an example when the normal driving force distribution operation is executed is indicated by a broken line, and an example when the driving force distribution operation in the present embodiment is executed is indicated by a solid line.

  As shown in FIG. 3, when a normal driving force distribution operation is performed, the driving force (driven wheel) distributed to the rear wheels 20L and 20R from the region indicated by reference numeral 3 in which the steering angle of the steering is about 90 degrees or more. Even if the distribution ratio [%] is increased, the turning moment (yaw rate [deg / s]) of the four-wheel drive vehicle 1 does not increase, and thus the turning performance of the vehicle cannot be improved.

  On the other hand, when the driving force distribution operation in the present embodiment is executed, the turning moment of the four-wheel drive vehicle 1 can be increased even in the region where the steering angle of the steering is about 90 degrees or more. .

  As described above, in the present embodiment, when the four-wheel drive vehicle 1 is in a turning state, the rear wheels 20L and 20R are in the initial stage of turning acceleration in which the rotation speed of the inner wheels of the front wheels 15L and 15R is equal to or lower than the rotation speed of the outer wheels. The inner wheels of the front wheels 15L and 15R are slipped at an early stage by reducing the driving force distributed to the front wheels 15L and 15R.

  As a result, the torque difference between the inner and outer wheels of the front wheels 15L and 15R increases, and the turning moment of the four-wheel drive vehicle 1 increases. Therefore, the ECU 23 according to the present embodiment can improve the turning performance of the vehicle as compared with the conventional one.

  Further, in the present embodiment, when the four-wheel drive vehicle 1 is in a turning state, the rotation speed of the inner wheels of the front wheels 15L and 15R is higher than the rotation speed of the outer wheels, that is, the inner wheels of the front wheels 15L and 15R slip excessively. In this case, since the driving force is distributed to the rear wheels 20L and 20R so as to prevent a decrease in lateral force of the inner wheels of the front wheels 15L and 15R, the turning performance of the vehicle can be improved compared to the conventional one. .

  In the present embodiment, the example in which the control device for a four-wheel drive vehicle in the present invention is applied to an FF type four-wheel drive vehicle has been described. However, the control device for a four-wheel drive vehicle in the present invention is an ECU 23 The present invention can also be applied to a so-called FR type four-wheel drive vehicle of the front engine / rear drive type.

  As described above, the control device for a four-wheel drive vehicle according to the present invention has an effect that the turning performance of the vehicle can be improved as compared with the conventional one, and the main drive wheel from the drive source. This is useful for a four-wheel drive vehicle equipped with a driving force distribution mechanism capable of changing the distribution ratio of the driving force transmitted to the driving wheel and the driven wheel.

  DESCRIPTION OF SYMBOLS 1 ... Four-wheel drive vehicle, 15L, 15R ... Front wheel (main drive wheel, steering wheel), 17 ... Propeller shaft, 18 ... Electronically controlled coupling (drive force distribution mechanism), 20L, 20R ... Rear wheel (slave drive wheel) 23 ... ECU (driving force distribution control unit)

Claims (3)

In a control device for a four-wheel drive vehicle provided with a drive force distribution mechanism capable of changing a distribution ratio of drive force transmitted from a drive source to a main drive wheel and a slave drive wheel,
The driving force distribution mechanism that reduces the driving force distributed to the driven wheels on condition that the rotational speed of the inner wheel of the steering wheel is equal to or lower than the rotational speed of the outer wheel when the four-wheel drive vehicle is in a turning state. A control device for a four-wheel drive vehicle, comprising a drive force distribution control unit for controlling the vehicle.   The driving force distribution control unit controls the driving force distribution mechanism so that the driving force distributed to the slave driving wheels is zero on condition that the driving force distributed to the slave driving wheels is reduced. The control device for a four-wheel drive vehicle according to claim 1.   The driving force distribution control unit is configured such that when the four-wheel drive vehicle is in a turning state, the rotation speed of the inner ring of the steering wheel is higher than the rotation speed of the outer ring. The driving force is distributed to the slave driving wheel with the higher driving force of the driving force according to the difference between the rotational speed of the motor and the driving force according to the slip ratio difference between the main driving wheel and the slave driving wheel. The control device for a four-wheel drive vehicle according to claim 1 or 2, wherein the driving force distribution mechanism is controlled to do so.

Images