JP2720699B2 - Differential adjustable front and rear wheel torque distribution control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front and rear wheel torque distribution control device for a four-wheel drive vehicle, and more particularly, to a front and rear wheel by adjusting a differential state between a front wheel and a rear wheel. The present invention relates to a differential adjustment type front and rear wheel torque distribution control device that controls torque distribution.

[0002]

2. Description of the Related Art An automobile configured to control a ratio of a torque transmitted from an engine to a front wheel (also referred to as a driving torque or a driving force) to a torque transmitted to a rear wheel according to a driving state. Various power transmission devices are known. For example, in a so-called full-time four-wheel drive automobile, a center differential for appropriately distributing the torque from the engine to the front wheel side and the rear wheel side, and a viscous coupling for limiting a differential in the center differential are used. It is conceivable to provide a differential limiting mechanism and adjust the differential limiting mechanism to control the torque ratio according to the operating state.

[0003]

However, in each of the above-described differential limiting mechanisms, the differential control characteristics are determined by physical properties and the like, and the differential control mechanism does not actively perform the differential control. No torque distribution control can be performed. Therefore, a differentially adjusted front and rear wheel torque distribution control device as shown in FIGS.

FIG. 3 is a block diagram showing details of a control system of the device, and FIG. 4 is a schematic plan view of a vehicle showing an entire configuration of a drive system of an automobile equipped with the device. As shown in FIG. 4, the output of the engine 2 is transmitted to the output shaft 8 via the torque converter 4 and the automatic transmission 6, and further,
It is transmitted to a center differential (hereinafter abbreviated as a center differential) 12 via an intermediate gear 10.

The output of the center differential 12 is transmitted from the axles 17L and 17R to the left and right front wheels 16 and 18 via a reduction gear mechanism 19 and a front wheel differential gear device (front differential) 14 on the one hand. Mechanism 1
5, transmitted from the axles 25L, 25R to the right and left rear wheels 24, 26 via a propeller shaft 20, a bevel gear mechanism 21, and a rear wheel differential gear device 22.

[0006] The center differential 12 is of a planetary gear type, and receives an output from the engine into a planetary carrier, outputs the output from a sun gear to a front wheel drive system, and outputs from a ring gear to a rear wheel drive system. Further, the center differential 12 has a hydraulic pressure limiting mechanism as a differential limiting mechanism that can change the distribution of the engine output torque between the front wheels and the rear wheels by limiting the differential between the front wheel output portion and the rear wheel output portion. A multi-plate clutch 28 is provided.

Therefore, the center differential 12 appropriately controls the hydraulic multi-plate clutch 28 from a completely free state to a locked state so that the torque transmitted to the front wheels and the rear wheels is approximately equal to that of the front wheels: the rear wheels. The control can be performed at a ratio (for example, 60:40) corresponding to the ground load of the front and rear wheels from about 32:68. The value of front wheel: rear wheel in the completely free state: about 32:68 can be defined by setting the gear ratio of the input gears on the front wheel side and the rear wheel side of the planetary gears. Approximately 32: 6 when the pressure in the hydraulic chamber is zero and completely free
8 is set.

The ratio in the completely free state (for example, about 32:68) changes depending on the load balance between the front wheel system and the rear wheel system, but usually takes such a value. Also,
When the pressure in the hydraulic chamber is set to a set pressure (for example, about 9 kg / cm ² ) and the hydraulic multi-plate clutch 28 is in a locked state and the differential limit becomes substantially zero, the torque distribution between the front wheels and the rear wheels is reduced. , A ratio (for example, 6
0:40).

Reference numeral 30 denotes the steering wheel 3
2 A steering angle sensor (steering angle sensor) 3 for detecting a rotation angle from a neutral position, that is, a steering wheel angle (steering angle) θ.
Reference numerals 4a and 34b denote lateral acceleration sensors for detecting lateral accelerations Gyf and Gyr acting on the front and rear portions of the vehicle body, respectively. In this example, two detection data Gyf and Gyr are averaged to obtain lateral acceleration data. However, only one lateral acceleration sensor 34 may be provided near the center of gravity of the vehicle body, and the detected value may be used as the lateral acceleration data.

Reference numeral 36 denotes a longitudinal acceleration G acting on the vehicle body.
x is a longitudinal acceleration sensor that detects x, 38 is a throttle position sensor that detects the throttle opening θt of the engine 2, 39 is an engine key switch of the engine 2, 40,
42, 46, and 44 are the left front wheel 16, the right front wheel 18,
These are wheel speed sensors for detecting the rotational speeds of the left rear wheel 24 and the right rear wheel 26. The outputs of these switches and the respective sensors are input to the controller 48.

Reference numeral 50 denotes an antilock brake device, which operates in conjunction with a brake switch 50A. That is, when the brake switch 50A is turned on when the brake pedal 51 is depressed, an antilock brake operation signal is output in conjunction therewith, and the antilock brake device 50 is operated. Further, when the operation signal of the anti-lock brake is output, a signal indicating the state is simultaneously output to the controller 4.
8 is input. Reference numeral 52 denotes an indicator light that is turned on based on a control signal from the controller 48.

The controller 48 includes a CPU (not shown), a ROM, a RAM, an interface, etc. necessary for control described later. Reference numeral 54 denotes a hydraulic pressure source, and 56 denotes a pressure control valve system (hereinafter, referred to as a pressure control valve) interposed between the hydraulic pressure source 54 and the hydraulic chamber of the hydraulic multi-plate clutch 28 and controlled by a control signal from a controller 48. (Abbreviated).

Further, the vehicle is provided with an automatic transmission 6, and reference numeral 160 is a shift lever position sensor (shift range detecting means) for detecting a selected shift range of a shift lever 160A of the automatic transmission. The detection information is also sent to the controller 48. Further, the engine speed Ne detected by the engine speed sensor (engine speed sensor) 170 and the transmission speed Nt detected by the transmission speed sensor (transmission speed sensor) 180 are also sent to the controller 48.

Further, a clutch 28 is used as a sensor.
A hydraulic pressure sensor 304 for detecting the hydraulic pressure applied to the piston is provided at a predetermined location. Next, components of a controller for controlling the differential limiting of the center differential 12 by the hydraulic multi-plate clutch 28 (drive force distribution control) will be described with reference to the block diagram of FIG. In this control, each sensor (wheel speed sensors 40, 42, 44, 46, steering angle sensors 30a, 30b, 30c, lateral acceleration sensor 34, longitudinal acceleration sensor 36, throttle position sensor 38, engine speed sensor 170, transmission speed The clutch pressure of the hydraulic multi-plate clutch 28 is set based on detection information from the number sensor 180, the shift position sensor 160, etc., and the differential hydraulic pressure of the hydraulic multi-plate clutch 28 is controlled so as to obtain a target clutch torque. It is supposed to.

In the data, ABS information, wheel speed,
Steering angle, gear position, total communication between ABS control unit and engine control unit (SCI communication: SCI = S
data such as erial Communication Interface) is input digitally, and the longitudinal acceleration, lateral acceleration, accelerator opening,
Analog inputs are made regarding the hydraulic control for the multi-plate clutch, the control of the 4WD control unit, the current to the electromagnetic clutch of the rear wheel differential gear device (rear differential) 22, and the like.

The clutch torque of the hydraulic multi-plate clutch 28 is a differential-compatible clutch torque for controlling the front wheel side and the rear wheel side to achieve an ideal differential state by focusing on the differential state. TV (or T _V ), clutch torque TX (or Tx) corresponding to longitudinal acceleration for performing control in accordance with longitudinal acceleration (vehicle acceleration) acting on the vehicle,
An engine torque proportional clutch torque T set in proportion to the engine output torque so that a large road surface transmission torque can be obtained in the front-rear-wheel directly connected four-wheel drive state at the time of sudden start, etc.
A (or Ta), and a clutch torque T for protection control for protecting the clutch portion of the wet multi-plate clutch.
The maximum value is selected from the four torque values with the pc.

Hereinafter, each of these clutch torques Tv, T
The setting of x, Ta, and Tpc will be described with reference to FIG. The differential corresponding clutch torque Tv is a clutch torque that causes the vehicle to behave in accordance with the driver's intention during turning. In order to control the posture of the vehicle body, the rear wheel is used as a drive base and slips from the rear wheel. Is effective, the clutch torque Tv corresponding to the differential is set to realize such a state.

For this reason, a portion related to the setting of the differential corresponding clutch torque Tv (front and rear wheel rotational speed difference proportional calculating means 20)
As shown in FIG. 3, 1) includes a front and rear wheel actual rotation speed difference detection unit 200, a front and rear wheel ideal rotation speed difference setting unit 210, a front and rear wheel actual rotation speed difference ΔVcd, and a front and rear wheel ideal rotation speed difference ΔVh.
c, a differential corresponding clutch torque setting unit 220 for setting the clutch torque Tv ′ from the clutch torque Tv ′.
And a correction unit 246 that corrects the lateral acceleration.

The front and rear wheel actual rotational speed difference detecting section 200 includes filters 202a to 202d for removing a micro-vibration component of data generated due to disturbance or the like, a front wheel rotational velocity data calculating section 204a, and a rear wheel rotational velocity data. Calculator 2
04b, and a front and rear wheel actual rotational speed difference calculation unit 206. Front wheel rotation speed data calculation unit 20
In 4a, the front wheel rotation speed Vf is obtained by averaging the front wheel rotation speeds obtained from the front wheel rotation speed data signals FL and FR, and the rear wheel rotation speed data calculation unit 204b outputs the rear wheel rotation speed data signal RL. , RR, the rear wheel rotation speed Vr is obtained by averaging the respective wheel speeds of the rear wheels.

The front / rear wheel actual rotational speed difference calculation unit 206 subtracts the front wheel rotational speed Vf from the rear wheel rotational speed Vr to obtain the actual rotational speed difference between the front and rear wheels (the rotational difference at the center differential)] Δ
Calculate Vcd. Front and rear wheel ideal rotational speed difference setting unit 210
Are a driver-requested steering angle calculation unit (pseudo-steering angle calculation unit) 212 as steering angle data detection means, and a driver-requested vehicle speed calculation unit (estimated vehicle speed calculation unit or pseudo vehicle speed) as vehicle speed data detection means. (Operation unit) 216 and an ideal rotation speed difference setting unit 218 as an ideal operation state setting unit.

Then, the ideal rotational speed difference setting section 218 calculates the driver's required steering angle δref calculated by the driver's required steering angle calculating section 212 and the estimated vehicle speed Vref calculated by the estimated vehicle speed calculating section 216. , An ideal rotational speed difference ΔVhc is set. In other words, with respect to the vehicle speed, at low vehicle speeds, the influence of the difference in the orbit radii of the front and rear wheels at the time of turning (so-called inner wheel difference) is large, and the rotation speed Vr of the rear wheel is smaller than the rotation speed Vf of the front wheel, but the vehicle speed is high As the rotation speed Vr of the rear wheel increases with respect to the rotation speed Vf of the front wheel, the rear wheel can easily slip at high speed. As a result, the responsiveness of the posture of the vehicle body, which is required at higher speeds, is ensured. As for the steering angle, the larger the steering angle is, the larger the rotation difference required for the front and rear wheels is. Therefore, the larger the magnitude | δref | of the steering angle data δref, the larger the value of ΔVhc.

As described above, the front and rear wheel actual rotation speed difference ΔVcd detected by the front and rear wheel actual rotation speed difference detection unit 200 is:
The difference between the front and rear wheel ideal rotation speed difference ΔVhc set by the front and rear wheel ideal rotation speed difference setting unit 210 is subtracted by the subtractor 222 (ΔVhc).
cd−ΔVhc), and the obtained difference ΔVc (= ΔVcd−Δ)
Vhc) and the ideal rotational speed difference ΔVhc between the front and rear wheels are input to the differential corresponding clutch torque setting unit 220 as data.

The differential corresponding clutch torque setting section 220
Front and rear wheel actual rotation speed difference ΔVcd and front and rear wheel ideal rotation speed difference ΔV
The clutch torque Tv ′ is set in accordance with the difference ΔVc (= ΔVcd−ΔVhc) from the clutch torque Tc.
v ′ is set. (I) When .DELTA.Vhc.gtoreq.0, it is desired that the speed of the rear wheels be higher than that of the front wheels, and the clutch torque Tv 'is set as follows.

If .DELTA.Vcd.gtoreq..DELTA.Vhc, the rear wheels are slipping due to excessive rotation, and it is desired to suppress a rear wheel slip by transferring a part of the engine torque largely distributed to the rear wheels toward the front wheels. . Therefore, the clutch torque Tv '
Tv '= a * ([Delta] Vcd- [Delta] Vhc) = a * [Delta] Vc (1.3) so that is increased in proportion to the difference [Delta] Vc ([Delta] Vcd- [Delta] Vhc) (where a is proportional. constant).

If ΔVhc>ΔVcd> 0, the actual rotational speed of the rear wheel is higher than that of the front wheel even though the front wheel is slipping.
If the value is increased, the engine torque distributed to the front wheels increases, and the slip of the front wheels is promoted. For this reason, it is desired to reduce the engine torque distributed to the front wheels by making the differential limitation free. Therefore, in this case, the clutch torque Tv 'is set to 0 to set a so-called dead zone.

If 0.gtoreq..DELTA.Vcd, the front wheels are slipping, and it is desired to reduce the distribution of the engine torque to the front wheels to reduce the slip of the front wheels. Therefore, Tv ′ = − a × ΔVcd = −a × (ΔVc + ΔVhc) (1.4) is set so that the clutch torque Tv ′ increases in proportion to the magnitude of ΔVcd (where a is Proportional constant).

The relationship between Tv 'and .DELTA.Vc is mapped, and the map is used to calculate the differential corresponding clutch torque Tv from the difference .DELTA.Vc and the ideal front and rear wheel rotational speed difference .DELTA.Vhc.
Can be requested. Note that when ΔVhc = 0, ΔV
There is no dead zone region where hc>ΔVcd> 0. (ii) When ΔVhc <0, it is desired to increase the speed of the front wheels as compared with the rear wheels, and the clutch torque Tv ′ is set as follows.

If .DELTA.Vcd.gtoreq.0, the rear wheel is over-rotating and slipping, and it is desired to suppress a rear wheel slip by shifting part of the engine torque largely distributed to the rear wheel toward the front wheel. . Therefore, when the clutch torque Tv 'is Δ
Tv '= a.times..DELTA.Vcd = a.times. (. DELTA.Vc + .DELTA.Vhc) (1.5) so as to increase in proportion to the magnitude of Vcd (where a is a proportional constant).

If 0>.DELTA.Vcd> .DELTA.Vhc, the actual rotational speed of the rear wheel is higher than that of the front wheel despite the slip of the rear wheel.
Increases the engine torque distributed to the rear wheels, and the slip of the rear wheels is promoted. For this reason, it is desired to reduce the engine torque distributed to the rear wheels by setting the differential limit to free. Therefore, in this case, the clutch torque Tv 'is set to 0 to set a so-called dead zone.

If .DELTA.Vhc.gtoreq..DELTA.Vcd, the front wheels are slipping, and it is desired to reduce the distribution of the engine torque to the front wheels to reduce the slip of the front wheels. Therefore, Tv '=-a.times. (. DELTA.Vcd-.DELTA.Vhc) =-a.times..DELTA.Vc (1.6) so that the clutch torque Tv' increases in proportion to the magnitude of .DELTA.Vc (.DELTA.Vcd-.DELTA.Vhc). (Where a is a proportional constant).

The relationship between Tv 'and .DELTA.Vc is mapped, and the differential corresponding clutch torque Tv can be obtained from the difference .DELTA.Vc and the ideal front and rear wheel rotational speed difference .DELTA.Vhc. In this way, the differential-corresponding clutch torque setting unit 220 refers to the map to determine ΔVc and ΔVc.
Vhc and the differential corresponding clutch torque Tv '
Is to be corrected for lateral acceleration.

[0032] The correction unit 246 is subjected to a lateral acceleration correction by multiplying the lateral G gain k ₁ to the differential corresponding clutch torque Tv ', but so as to obtain a differential response clutch torque Tv, the lateral G gain k ₁ is set as follows. That is, the detection data Gy from the lateral acceleration sensor 34 is sent to the lateral G gain setting unit 244 after the fine vibration component of the data generated due to disturbance or the like is removed through the filter 242. In the lateral G gain setting unit 244 sets the lateral G gain k ₁ from the lateral acceleration data Gy according to the map shown in the block of the setting portion 244 of FIG.

The lateral G gain k ₁ is determined by the friction coefficient μ of the road surface.
Is to be reflected in the control, and the lateral acceleration G
As y becomes larger, it can be determined that the road surface μ is larger, and as the road surface μ becomes larger, it is desired that the distribution of the engine torque is made mainly of the rear wheels and that the turning performance of the vehicle body is given priority. Therefore,
The size of the road μ (therefore, the size of the lateral acceleration Gy)
If larger, the lateral G gain k ₁ is decreased, thereby performing the correction for reducing the set clutch torque Tv. It should be noted that even when the road surface μ is large, it is conceivable to omit the correction by the lateral G gain k ₁ unless special priority is given to the turning performance of the vehicle body.

The clutch torque Tx corresponding to the longitudinal acceleration is a low μ in the clutch torque control corresponding to the front-rear wheel differential.
When running on a road (a road with a low coefficient of friction μ), all four wheels slip and there is a possibility that control hunting will occur. This is a clutch torque for preventing the vehicle from under-steering strongly and enabling the vehicle to perform a smooth turning operation. Control is performed in accordance with the longitudinal acceleration Gx acting on the vehicle.

The setting of the clutch torque Tx corresponding to the longitudinal acceleration is performed by the clutch torque setting means 254 corresponding to the longitudinal acceleration.
And the detection data G from the longitudinal acceleration sensor 36
x is sent to the clutch torque setting means 254 after the micro-vibration component of the data generated by disturbance or the like is removed through the filter 252. The longitudinal acceleration corresponding clutch torque setting means 254 obtains the longitudinal acceleration corresponding clutch torque Tx 'from the longitudinal acceleration data Gx based on, for example, a map (refer to a map in a block 254 in FIG. 3). The longitudinally-accelerated clutch torque Tx 'thus set is applied to the lateral-acceleration-based correction unit 256.
Is corrected. The correction unit 256 includes the correction unit 2 described above.
46 and a similar correction is subjected to a lateral acceleration correction by multiplying the lateral G gain k ₁ in longitudinal acceleration corresponding clutch torque Tx ', but so as to obtain a longitudinal acceleration corresponding clutch torque Tx, the lateral G gain k ₁ is described above, because the aim is also an seeks to reflect control the state of the friction coefficient μ of the road surface in the same manner as described above will not be described here.

The clutch torque Tx corresponding to the longitudinal acceleration corrected in this manner is output as data when the switch 258a is turned on and off. The switch 258a determines whether the front wheel speed Vf is equal to the vehicle speed V based on a signal from the determination means 258.
When the value is larger than ref, that is, when the front wheel is slipping (at the time of front slip), the signal is turned off. In other cases, the signal is turned off.

This is because, as described above, the clutch torque control corresponding to the longitudinal acceleration prevents the hunting phenomenon of the clutch torque control corresponding to the differential when the four wheels are slipping. Is determined. Therefore, the clutch torque Tx corresponding to the longitudinal acceleration set only at the time of front slip is output, and is not output in other cases (in this case, Tx
= 0, hereinafter, generally, when the switch is turned off and the clutch torque is not output, the clutch torque value is set to 0).

Engine torque proportional clutch torque Ta
The set torque for setting the direct-coupled four-wheel drive state in advance so that the initial slip of the rear wheels can be prevented when the transmission torque is expected to increase when the vehicle suddenly starts from a stopped state. It is. Therefore, a part (engine torque proportional clutch torque setting means) 260 for setting the engine torque proportional clutch torque Ta includes an engine torque detector 264 for detecting the engine torque Te at a certain moment, as shown in the lower left part of FIG. , A torque converter torque ratio detector 26 for detecting the torque converter torque ratio t at that time.
6, a transmission reduction ratio detecting unit 276 for detecting the transmission reduction ratio ρm at that time, and the engine torque Te to the engine torque proportional torque T based on a map set in proportion to the engine torque Te.
an engine torque proportional torque setting unit 268 for obtaining a ′;
The engine torque proportional torque Ta 'in the above torque converter torque ratio t, transmission reduction ratio .rho.m, by multiplying the final reduction [rho ₁ and the rotational difference gain k _2, the engine torque proportional clutch torque computing to obtain the engine torque proportional clutch torque Ta Section 270 and the set engine torque proportional clutch torque Ta at low speed (for example, Vref <20).
km / h) as a switch.

In the engine torque detector 264, the filter 262 sent from the throttle position sensor 38
The throttle opening degree data θth from which the minute vibration component of the data generated by the disturbance or the like is removed through a, and the engine from which the minute vibration component of the data generated by the disturbance and the like is transmitted from the engine speed sensor 170 through the filter 262b. From the rotation speed data Ne, the engine torque Te at that time is obtained through an engine torque map.

In the torque converter torque ratio detecting section 266, a filter 262b sent from the engine speed sensor 170
From the engine speed data Ne from which the disturbance components have been removed through the transmission speed sensor N and the transmission speed data Nt sent from the transmission speed sensor 180 and from which the disturbance components have been removed through the filter 262c, the transmission torque at that time can be obtained through the transmission torque ratio map. The ratio t is determined.

Transmission reduction ratio detector 276
In this example, the transmission reduction ratio ρm is obtained from the selected shift stage information from the shift lever position sensor 160 with reference to a shift stage-reduction ratio correspondence map as shown in a block 276 in FIG. A map used for setting of the engine torque proportional torque setting unit 268 (FIG. 3)
), The engine torque Te and the engine torque proportional torque Ta ′ are proportional constants determined from known constants such as the number of teeth Zs and Zr of the sun gear and the ring gear, the front wheel shared load Wf, and the vehicle weight Wa. Is a linear relationship.

[0042] In the engine torque proportional clutch torque computing unit 270, an engine torque proportional torque Ta 'determined as described above, the torque converter torque ratio t, transmission reduction ratio .rho.m, final reduction [rho ₁ and the rotational difference gain k
_The rotation difference gain k ₂ is set by the rotation difference gain setting section 275 as follows. That is, the rotation difference gain k ₂ is to avoid the tight corner braking phenomenon, and the ideal rotation speed difference setting unit 218
Is determined from the ideal rotational speed difference ΔVhc set in accordance with a map (not shown).

Then, as the ideal rotation speed difference ΔVhc increases, the rotation difference gain k ₂ decreases linearly,
By multiplying and correcting this rotation difference gain k ₂ ,
When the ideal rotation speed difference ΔVhc becomes large during turning or the like, the engine torque proportional clutch torque Ta is reduced so that turning performance (performance that can prevent a tight corner braking phenomenon) is prioritized over sudden starting performance. Because

Further, the switch 274a is connected to the judgment means 2
At the time of low vehicle speed (in this example, Vref <
At 20 km / h), it is turned on to enable the output of the engine torque proportional clutch torque Ta as data, but the vehicle speed further increases (Vref ≧ 20 km / h).
And the output is stopped as the data of the engine torque proportional clutch torque Ta. This is because engine torque proportional control may cause a tight corner braking phenomenon when turning at a certain speed, or may eliminate other control speeds when slip tolerance is required. Thus, a condition is provided that this engine torque proportional control is performed only at low vehicle speed.

Next, the setting of the protection control clutch torque Tpc for protecting the clutch portion of the wet multi-plate clutch 28 will be described. The setting of the clutch torque Tpc is performed by the protection control section 230. .
That is, in the wet-type multi-plate clutch 28, in general, when the differential rotation between the clutch plates becomes large, there is a fear that damage such as seizure of the clutch facing and an increase in the amount of wear may be caused. Is larger, the damage is more likely to occur. On the other hand, in order to protect the clutch 28 by avoiding such a state, it is conceivable to make the clutch free (disconnecting the connection between the clutch plates). If performed instantaneously, there is a fear that the attitude of the vehicle may change suddenly. Therefore, the protection control unit 230 sets the protection control clutch torque Tpc so as to avoid any of these phenomena.

The protection control unit 230 receives the front and rear wheel actual rotation speed difference Vcd calculated by the front and rear wheel actual rotation speed difference calculation unit 206, and sets the front and rear wheel actual rotation speed difference Vcd to a reference value (8 in this example). (0.6 km / h) for more than the reference time (1 second in this example), the protection control clutch torque Tpc is set in a predetermined pattern.

That is, when the above-mentioned detection condition is satisfied, the protection control clutch torque Tpc is first set to the upper limit for a short time (1 second in this example), and then gradually reduced to 0 (natural release). ) Let me do it. In this example, T
The relationship between pc and time tt is as follows. Tpc = 40−14tt (4.1) When the above detection condition is not satisfied, the value of the protection control clutch torque Tpc is set to zero.

The clutch torques of the differential corresponding clutch torque Tv, the longitudinal acceleration corresponding clutch torque Tx, the engine torque proportional clutch torque Ta, and the protection control clutch torque Tpc are obtained in each control cycle repeated at an appropriate timing. Each set clutch torque Tv, Tx, Ta, Tpc is set as follows:
It is sent to the maximum value selection unit 280.

In the maximum value selecting section 280, the maximum one of the clutch torques Tv, Tx, Ta and Tpc (this clutch torque is referred to as Tc) for each control cycle.
Select However, when the switch 258a or 274a is OFF, the clutch torque Tx or Ta is not sent, and the maximum value selection unit 280 selects the maximum value from the clutch torques sent.

The clutch torque Tc selected in this way is sent to the torque-pressure converter 282, where
The clutch control pressure Pc is set such that the set clutch torque Tc is obtained. Here, the clutch control pressure Pc is obtained from the clutch torque Tc by a map (see the block 282 in FIG. 3). However, since the clutch torque Tc and the clutch control pressure Pc are generally in a proportional relationship, the map is also shown. It is linear.

Further, the clutch control pressure Pc thus changed is added to an adder / subtractor 284 as a preload applying means.
, Centrifugal pressure correction and preload correction are performed. The centrifugal pressure correction is based on the clutch control pressure Pc and the centrifugal correction pressure P set by the centrifugal correction pressure setting unit 286.
v is subtracted, but the centrifugal correction pressure setting unit 2
At 86, a map is obtained from the front wheel speed Vf calculated at 204a using a map as shown in the block 286 of FIG. This is because the piston chamber rotates in synchronization with the front wheel side shaft, so that the centrifugal oil pressure is generated corresponding to the front wheel vehicle speed Vf, and the centrifugal correction pressure Pv is proportional to the square of the front wheel vehicle speed Vf. Is set.

The preload correction is a correction in which the initial engagement pressure (initial pressure) set by the initial engagement pressure setting section (preload setting section) 288 is added to the clutch control pressure Pc as Pi preload. The purpose of this preload correction is to keep the clutches 28 of the clutch 28 in a marginal contact state (extremely slight contact state) such that no drag torque is generated between the clutch plates.
The purpose is to increase the control response.

However, the clearance between the clutch plates of the clutch varies from product to product from the manufacturing stage due to a component error, an assembly error, and the like, and the same product also changes over time. In particular, since the return spring of the clutch plate is generally strong, errors and aging of each part greatly affect the clearance between the clutch plates.

For this reason, it is necessary to always keep the state of contact between the clutch plates in a very close state while detecting the clearance state between the clutch plates at an appropriate timing. Therefore, the preload setting unit 288 sets the initial pressure Pi by performing a trial (here, learning) at an appropriate time interval to determine how much preload is required.

Thus, the centrifugal pressure correction is performed by subtracting the centrifugal correction pressure Pv from the clutch control pressure Pc, which is the effective hydraulic pressure, and the preload application correction is performed by adding the initial pressure (preload) Pi. Oil chamber supply level control pressure P
cd (= Pc−Pv + Pi) is the peak hold filter 2
90. The peak hold filter 290 is a kind of limiter for preventing an excessive sudden change in the hydraulic pressure so that hunting does not occur in the control due to a sudden change in the hydraulic pressure. 4kg / cm ² / s) is set and for the falling edge of hydraulic, are set slightly lower limit speed (e.g. 15.7kg / cm ² / s).

When the control pressure Pcd at which the speed of the oil pressure change exceeds such a limit is sent, the control pressure according to the limit value is maintained. Further, the control pressure Pcd ′ passing through the filter 290 is
a, 294a, and is sent to the duty setting unit 295. The switch 292a is turned off by the signal from the judging means 292 when the ABS control (anti-lock brake control) is being performed (if it is in the ON state), and is turned on when the ABS control is not being performed. .
In other words, on condition that ABS control is not performed,
A signal of the control pressure Pcd 'is sent. This is because it is necessary to reliably operate the ABS during the ABS control, and at this time, controlling the torque distribution state of the front and rear wheels is not preferable because it interferes with the ABS control.

The switch 294a is connected to the judgment means 29.
This is a control switch for protecting the duty solenoid valve in response to a signal from the control unit 4. When the speed is low and the set clutch torque Tc is small, the duty is set to 0. The low-speed condition can be defined as, for example, Vref ≦ 5 km / h, and the clutch torque Tc can be defined as, for example, Tc ≦ 1 kgfm. Then, when these two conditions are satisfied, the switch 294a is turned off, and the signal of the control pressure Pcd 'is not sent.

The duty setting section 295 includes a pressure feedback correction section 296 and a pressure-duty conversion section 298.
With Pressure feedback correction unit 296
Receives the control information from the pressure sensor 304 for detecting the actual pressure acting on the piston and receives the control pressure Pcd ′.
This is for correcting the characteristic of the hydraulic circuit. The signal sent from the pressure sensor 304 to the pressure feedback correction unit 296 has a filter 306 from which noise components due to disturbance or the like are removed.

The pressure-duty conversion section 298 sets (Duty) corresponding to the control pressure P that has been feedback-corrected by the pressure feedback correction section 296, and is set in the block of the clutch pressure-duty conversion section 298 in FIG. As shown in the map, the duty increases linearly with the pressure P from the preload state to the maximum pressure state. From such a correspondence, a duty corresponding to the control pressure P is set.

A hydraulic circuit 300 functioning as a control execution unit
Thus, the duty solenoid 302 is operated in accordance with the duty set in this way to control the center differential hydraulic multiple disc clutch 28. on the other hand,
In parallel with such center differential control, the state of torque distribution to the front and rear wheels is displayed in a meter cluster of an instrument panel in a driver's seat.

That is, in the meter cluster, there is provided a torque distribution display section 312 for graphically displaying (or meter display) the state of torque distribution to the front wheels (or rear wheels). The torque distribution state is displayed according to the estimated magnitude of the distribution torque. Thus, the torque estimating means 3
The reason for estimating the torque distribution state by 10 is that it is difficult to actually measure the torque distribution state.

With the above configuration, first, by setting the clutch torque Tv corresponding to the differential, the posture control of the vehicle body can be appropriately adjusted while setting the rear wheel as a drive base so as to slip from the rear wheel. As a result, the vehicle can behave in accordance with the driver's will when turning. In addition, at the time of acceleration, such as during front slip, the torque distribution equivalent to the direct connection 4WD is provided by the clutch torque Tx corresponding to the front-rear acceleration. Under turning is prevented and smooth turning can be performed.

Further, when the vehicle is started or when suddenly accelerating from a low speed, the vehicle is brought into the direct connection 4WD state by the engine torque proportional clutch torque Ta so that a high torque can be transmitted to the road surface. This prevents tire slippage at the time of rapid acceleration, improves running performance, and contributes to improvement in durability of the driving system. Further, the clutch plate is protected by the protection control clutch torque Tpc, which contributes to the improvement of the durability of the device and the effect of preventing the spin of the vehicle.

However, as described above, the clutch torque corresponding to the longitudinal acceleration (the clutch torque corresponding to the vehicle body acceleration) Tx
, Differential clutch torque (front-rear rotation difference clutch torque) Tv, engine torque proportional clutch torque Ta
The torque determined by these three factors is determined by further adjusting the lateral G, the steering wheel angle, and the vehicle speed. However, when setting each constant of three inputs and three factors and a characteristic map, a lot of tests are performed. , And a complicated interpretation is required.

As described above, adopting the maximum value among the clutch torque Tx corresponding to the longitudinal acceleration, the clutch torque Tv corresponding to the differential, and the clutch torque Ta corresponding to the engine torque does not necessarily realize an appropriate control state. Not limited to this, the selection of the maximum value may work more effectively, but the magnitude of the torque may be accidentally set by some unconscious factor.

In the microcomputer constituting the controller, high-speed processing at a high cost is required to calculate various control elements, and there is a problem in cost. The present invention has been made in view of the above problems, and provides a differentially adjusted front and rear wheel torque distribution control device that can be configured at low cost and can always appropriately perform front and rear torque distribution control. With the goal.

[0067]

SUMMARY OF THE INVENTION Accordingly, a differentially adjusted front and rear wheel torque distribution control device according to the present invention of claim 1 permits a differential between a front wheel side drive shaft and a rear wheel side drive shaft, and allows these to be performed. A center differential that distributes torque from the engine to the front wheel drive shaft and the rear wheel drive shaft, a differential limiting mechanism that limits the differential of the center differential, and control means that controls the differential limiting mechanism. Well,
The control means includes: a vehicle-body acceleration-dependent control amount element setting means for setting a control amount element according to the vehicle body acceleration; and a front-rear wheel difference rotation-related control amount element setting means for setting a control amount element according to the front and rear wheel difference rotation. An engine output corresponding control amount element setting means for setting a control amount element according to the output of the engine, and adding the respective control amount elements set by the respective control amount element setting means to perform the differential operation. A control amount setting means for setting the control amount of the limiting mechanism is provided.

Further, according to a second aspect of the present invention, there is provided a differentially-adjustable front / rear wheel torque distribution control apparatus which allows a front wheel side drive shaft and a rear wheel side drive shaft to be differentially driven, and which includes a front wheel side drive shaft and a rear wheel side drive shaft. A center differential for distributing torque from the engine to the wheel drive shaft, a differential limiting mechanism for limiting the differential of the center differential, and control means for controlling the differential limiting mechanism, wherein the control means includes: A vehicle-acceleration-dependent control amount element setting means for setting a control amount element according to the vehicle body acceleration; a front-rear wheel differential rotation-responsive control amount element setting means for setting a control amount element according to the front-rear wheel differential rotation; Control amount element setting means for setting the control amount element according to the engine output, and adding the respective control amount elements set by the respective control amount element setting means to obtain the difference. Control amount setting means for setting the control amount of the limiting mechanism; and the engine output-corresponding control amount element setting means is provided with an engine output corresponding to the engine output so as to prevent the front and rear wheel differential rotation caused by the load movement due to the gradient of the traveling road surface. A correction means for correcting the controlled variable element according to the gradient of the traveling road surface is provided.

[0069]

In the above-described first and second embodiment of the present invention, the center differential includes:
The differential between the front wheel drive shaft and the rear wheel drive shaft of the vehicle is allowed, and the torque from the engine is distributed to the front wheel drive shaft and the rear wheel drive shaft. At this time, the differential limiting mechanism can adjust the torque distribution state by limiting the differential of the center differential. The differential limiting mechanism is controlled by a control means. In the control means, a control amount element corresponding to the vehicle body acceleration is set by a vehicle acceleration corresponding control amount element setting means, and a front-rear wheel differential rotation corresponding control amount element setting means is provided. To set the control amount element according to the front and rear wheel differential rotation, set the control amount element according to the engine output by the engine output corresponding control amount element setting means, and set these control amount elements by the control amount setting means. The control amount of the differential limiting mechanism is set by adding the respective control amount elements set by the means. The control means controls the differential limiting mechanism according to the control amount thus set.

Further, in the above-described second aspect of the present invention, the center differential allows the front-wheel drive shaft and the rear-wheel drive shaft of the vehicle to be differential. The torque from the engine is distributed to the front wheel side drive shaft and the rear wheel side drive shaft. At this time, the differential limiting mechanism can adjust the torque distribution state by limiting the differential of the center differential. The differential limiting mechanism is controlled by a control means. In the control means, a control amount element corresponding to the vehicle body acceleration is set by a vehicle acceleration corresponding control amount element setting means, and a front-rear wheel differential rotation corresponding control amount element setting means is provided. The control amount element according to the front and rear wheel differential rotation is set, and the control amount element according to the engine output is set by the engine output corresponding control amount element setting means. In order to prevent the front and rear wheel differential rotation caused by the load movement due to the gradient of the above, the control means corrects the control amount element according to the engine output according to the gradient of the traveling road surface. And, by the control amount setting means,
Each control amount element set by each of these control amount element setting means is added to set the control amount of the differential limiting mechanism. The control means controls the differential limiting mechanism according to the control amount thus set.

[0071]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram showing an outline of a control system of a differential-adjustment type front and rear wheel torque distribution control apparatus according to an embodiment of the present invention. It is a typical block diagram showing the outline of the control system of the modification.

The differential-adjustable front and rear wheel torque distribution control device is provided in a drive system of an automobile as shown in FIG. That is, as shown in FIG. 4, the output of the engine 2 is transmitted through the torque converter 4 and the automatic transmission 6 to the output shaft 8.
, And further transmitted to a center differential (hereinafter abbreviated as center differential) 12 via an intermediate gear 10.

The output of the center differential 12 is transmitted from the axles 17L and 17R to the left and right front wheels 16 and 18 via a reduction gear mechanism 19 and a front differential gear device (front differential) 14 on the one hand, and bevel gears on the other hand. Mechanism 1
5, transmitted from the axles 25L, 25R to the left and right rear wheels 24, 26 via the propeller shaft 20, the bevel gear mechanism 21, and the differential gear device 22 for the rear wheels.

The center differential 12 is of a planetary gear type here, so that the output from the engine is input to the planetary carrier, output from the sun gear to the front wheel drive system, and output from the ring gear to the rear wheel drive system. Has become.
Further, the center differential 12 has a hydraulic pressure limiting mechanism as a differential limiting mechanism that can change the distribution of the engine output torque between the front wheels and the rear wheels by limiting the differential between the front wheel output portion and the rear wheel output portion. A multi-plate clutch 28 is provided.

Therefore, the center differential 12 appropriately controls the hydraulic multi-plate clutch 28 from a completely free state to a locked state, so that the torque transmitted to the front wheels and the rear wheels is approximately equal to that of the front wheels: the rear wheels. The control can be performed at a ratio (for example, 60:40) corresponding to the ground load of the front and rear wheels from about 32:68. The value of front wheel: rear wheel in the completely free state: about 32:68 can be defined by setting the gear ratio of the input gears on the front wheel side and the rear wheel side of the planetary gears. Approximately 32: 6 when the pressure in the hydraulic chamber is zero and completely free
8 is set.

The ratio in the completely free state (for example, about 32:68) changes depending on the load balance between the front wheel system and the rear wheel system, but usually has such a value. Also,
When the pressure in the hydraulic chamber is set to a set pressure (for example, about 9 kg / cm ² ) and the hydraulic multi-plate clutch 28 is in a locked state and the differential limit becomes substantially zero, the torque distribution between the front wheels and the rear wheels is reduced. , A ratio (for example, 6
0:40).

The details of the configuration of the drive system of the vehicle have already been described, and will not be described here. And
This device differs from the above-described example (see FIG. 3) in the portion related to the setting of the control torque of the hydraulic multiple disc clutch 28 in the controller 48. That is, the controller 4
8, for setting the clutch torque of the hydraulic multi-plate clutch 28, as shown in FIG. 1, a control amount element setting means 203A corresponding to the vehicle body acceleration, a control amount element setting means 200A corresponding to the front and rear wheel differential rotation, and an engine Output corresponding control amount element setting means 260A and correction means 246, 260B, 260C
And a control amount setting means (adder) 380.

Control amount element setting means 203 corresponding to vehicle body acceleration
A sets a clutch torque (restraint torque) TX corresponding to the vehicle body acceleration Gx as a control amount element, and this value TX is set substantially in the same manner as the clutch torque Tx shown in FIG. That is, this control amount element TX is
For example, when there is a possibility that all four wheels slip and control hunting occurs when traveling on a low μ road or the like, a control amount (clutch torque) corresponding to the longitudinal acceleration (running acceleration / deceleration) Gx of the vehicle is given. The purpose of this is to prevent the vehicle from under-steering strongly and to enable the vehicle to perform a smooth turning operation.

The control amount element TX is set, for example, by detecting the detection data Gx input from the longitudinal acceleration sensor 36,
After filtering and removing components such as disturbance, the front wheel shared load (W) during acceleration is calculated from the longitudinal acceleration data Gx.
f '/ Wa) and the total output torque Ta required for acceleration (which is a torque considered on the propeller shaft) are obtained, and these are integrated to obtain the front wheel shared torque Tf. Then, the clutch torque TX can be set corresponding to the front wheel shared torque Tf.

The longitudinal acceleration Gx and the clutch torque T
By examining the relationship with X and mapping this relationship in advance, the clutch torque TX can be obtained from the longitudinal acceleration Gx using the map. The front-rear wheel differential rotation-responsive control amount element setting means 200A sets a control amount element (restriction torque) TV according to the front-rear wheel differential rotation ΔVcd.
V is set substantially the same as the clutch torque Tv shown in FIG.

That is, the control amount element TV is a control amount element for performing control such that an ideal differential state is achieved by focusing on the differential state between the front wheel side and the rear wheel side. That is, the control amount element TV is a clutch torque that causes the vehicle to behave in accordance with the driver's intention during turning. For example, to control the posture of the vehicle body, the rear wheel is slipped from the rear wheel as a drive base. Setting is effective,
It is set so as to realize such a state.

The setting of the control amount element TV is performed in accordance with FIG.
The front and rear wheel actual rotation speed difference ΔVcd and the front and rear wheel ideal rotation speed difference Δ determined by the functional parts such as the front and rear wheel actual rotation speed difference detection unit 200 and the front and rear wheel ideal rotation speed difference setting unit 210 shown in FIG.
Vhc. Note that the front and rear wheel actual rotation speed difference Δ
Based on the front wheel speed data Vf and the rear wheel speed data Vr output from the wheel speed sensor 40 and filtered to remove components such as disturbance, the actual wheel speed difference ΔVcd (= front and rear wheels) is subtracted. Vr−Vf).

The ideal rotational speed difference ΔVhc between the front and rear wheels is
A driver-requested steering angle obtained based on the steering angle data θ output from the steering angle sensor 30;
And the driver-requested vehicle speed obtained based on the wheel speed data V output from the vehicle. To estimate the driver request vehicle speed (estimated vehicle speed), for example, 4
From among the rotation speed data signals FL, FR, RL, and RR of the wheels detected by the wheel speed sensors 40 of the wheels, the wheel speed data having the second largest value (from the smaller one) is selected, and this selection is performed. Wheel speed data etc. and longitudinal acceleration sensor 3
Based on the longitudinal acceleration detected in step 6, the vehicle speed after that is estimated from both data SVW and Gx at a certain point in time. That is, the wheel speed data SVW at a certain point in time
Is V ₂ and the longitudinal acceleration data Gx is a, the theoretical vehicle speed Vref after a time t from this point is Vref
= V ₂ + at.

The portion for estimating the driver's requested vehicle speed (estimated vehicle speed) can be defined as a vehicle speed sensor 216. In addition, two of the rotation speed data from the bottom
The reason why the wheel speed data of the second size is adopted is that each wheel usually slips to the over-rotation side in many cases, and it is normally desirable to use the wheel speed of the lowest rotation speed. The second wheel speed from the bottom is adopted in consideration of the performance.

Then, the ideal rotational speed difference ΔVhc between the front and rear wheels
As for the vehicle speed, when the vehicle speed is low, the influence of the difference in the orbit radii of the front and rear wheels at the time of turning (so-called inner wheel difference) is large, and the rotation speed Vr of the rear wheel is smaller than the rotation speed Vf of the front wheel, but the vehicle speed is high. As the rotation speed Vr of the rear wheel increases with respect to the rotation speed Vf of the front wheel, the rear wheel can easily slip at high speed. As a result, the responsiveness of the posture of the vehicle body, which is required at higher speeds, is ensured. As for the steering angle, the larger the steering angle is, the larger the rotation difference required for the front and rear wheels is. Therefore, the larger the magnitude | δref | of the steering angle data δref, the larger the value of ΔVhc.

Then, for example, the actual rotational speed difference ΔVcd between the front and rear wheels
Is subtracted from the front and rear wheel ideal rotational speed difference ΔVhc to obtain the difference Δ
The clutch torque TV is set according to Vc (ΔVcd−ΔVhc). Engine output corresponding control amount element setting means 260
A is for setting a control amount element (restraint torque) TA according to the engine output Te.
Are set substantially in the same manner as the clutch torque Ta shown in FIG.

In other words, when the transmission torque is expected to increase when the vehicle suddenly starts from a stopped state, the control amount element TA prevents initial slip of the rear wheels and obtains a large road surface transmission torque. Is set in advance to set the direct connection four-wheel drive state. The control amount element TA is set, for example, by obtaining the engine torque Te at a certain moment, the torque converter torque ratio t at that time, and the transmission reduction ratio ρm at that time, and, for example, from the engine torque Te to the engine torque based on a map. The proportional torque TA 'is obtained, and the torque converter torque ratio t, the transmission reduction ratio ρm,
The engine torque proportional clutch torque TA is obtained by multiplying the final deceleration ρ ₁ and the rotation difference gain k _{2 and the} like.

Then, the control amount element (constraint torque) TX determined by the vehicle acceleration-dependent control amount element setting means 203A.
Since this control amount element TX is for running on a low μ road, etc., the switch 258 is configured to output only when four wheels are slipping. Further, a limiter 310A is provided at an output portion of the control amount element TX, and in consideration of prevention of sudden change in control, protection of the clutch, and the like, the control amount element TX
Is restricted.

A control amount element setting means 20 corresponding to front and rear wheel differential rotation
The control amount element (constraint torque) TV obtained at 0 A is corrected by the correction means 246. This correction is a lateral acceleration correction, for example, by multiplying the map 320 by a lateral G gain k ₁ determined according to the lateral G of the vehicle. Explaining the map 320, this horizontal G gain k
₁ is to reflect the state of the friction coefficient μ of the road surface in the control, and it can be determined that the road surface μ increases as the lateral acceleration Gy increases, and the distribution of the engine torque is mainly performed by the rear wheels as the road surface μ increases. I want to be able to give priority to the turning of the car body. Then, the size of the road surface μ (therefore,
When the lateral acceleration Gy) increases, the lateral G gain k
A correction is made to decrease the set clutch torque Tv by decreasing ₁ . It should be noted that even when the road surface μ is large, it is conceivable to omit the correction by the lateral G gain k ₁ unless special priority is given to the turning performance of the vehicle body. In addition, a limiter 3 is also provided at the output of the control amount element TV.
10B is provided, and the value of the control amount element TX is limited in consideration of prevention of sudden change in control, protection of the clutch, and the like.

Engine output corresponding control amount element setting means 26
The control amount element (restraint torque) TA obtained at 0A is corrected by the correction means 260B and 260C. Correction by the correction unit 260B is a steering angle correction is performed by multiplying for example a steering angle gain k ₂ determined according to the steering angle by the map 330 (steering wheel angle).

That is, the control amount element TA is for setting the direct-coupled four-wheel drive state so as to obtain the large road surface transmission torque while preventing the initial slip of the rear wheels. I want to adjust the steer characteristics to slightly oversteer by increasing the torque. So, map 33
As shown in 0, the steering angle is increased, the steering angle gain k ₂ is given to reduce the control volume element TA.

The correction by the correction means 260C is a correction relating to the vehicle speed, the lateral acceleration and the gradient.
A vehicle speed gain k ₃ for determining in accordance with the vehicle speed by 0, for example, obtains a lateral acceleration-gradient gain k ₄ be determined according to the lateral acceleration and the gradient a map 340, a maximum value selection unit 260D, the larger of the Select the gain of
The correction gain is used for the correction means 260C. The correction by the correction means 260C is also performed by multiplying the correction gain.

[0093] Incidentally, the vehicle speed gain k _3, as shown in the map 340, the control gain k ₃ so as to decrease the controlled variable element TA and the vehicle speed increases are given. This is because the control amount element TA is for a start or a low speed. Further, as shown in the map 350, the lateral acceleration / gradient gain k ₄ decreases the control amount element TA as the lateral acceleration increases, but controls the gradient as the gradient increases. It is set so as not to decrease the quantity element TA. In the map,
(+) Indicates an upward gradient, and (-) indicates a downward gradient.

Among these, the gain factor relating to the lateral G is to reflect the state of the friction coefficient μ of the road surface in the control similarly to the control by the correction means 246 described above, and as the lateral acceleration Gy increases, the gain factor of the road surface μ increases. It is determined that the larger the road surface μ, the more the turning of the vehicle body can be prioritized with the distribution of engine torque as the rear wheels. Therefore, when the size of the road surface μ (and therefore the size of the lateral acceleration Gy) increases, the lateral G gain k ₁ is reduced,
Correction for reducing the set clutch torque Tv is performed.

Further, as for the gain element relating to the gradient, the driving force and the braking force (engine brake) are required as the gradient increases, so that as the gradient increases, the control amount element TA increases to obtain a large road surface transmission torque. This is to bring the vehicle closer to the direct-coupled four-wheel drive state. Then, the maximum value selection unit 260D, (a vehicle speed gain k _3, lateral acceleration, gradient gain k ₄₎ gain of two systems by selecting the larger one of, because trying to secure a gradient running performance during medium or high speed is there.

The control amount elements TX, TV, and TA thus set are added by the adders 380A, 380B of the control amount setting means 380, and the clutch torque (clutch restraining torque) T (= TX + TV + TA) is obtained. It is determined. The clutch torque (clutch restraining torque) T set in this way is sent as a control signal to the hydraulic control system of the hydraulic multiple disc clutch 28 for center differential control. The output from the control amount setting means 380 is: For example, as shown in FIG. 3, a process from the torque-pressure converter 282 to the hydraulic circuit 300 may be performed, and then the process may be used for hydraulic control of the hydraulic multi-plate clutch 28.

For the above-described correction, a vehicle speed sensor for detecting the vehicle speed (vehicle speed) and a steering angle (handle angle) θ
Angle sensor (steering wheel angle sensor) for detecting vehicle acceleration, lateral acceleration sensor (lateral G sensor) for detecting lateral acceleration (lateral G) Gy, road surface gradient sensor for detecting road surface gradient, and detecting slip condition of four wheels A wheel slip sensor is provided. The vehicle speed sensor, the steering angle sensor, and the lateral G sensor described above can be used.

As the road surface gradient sensor, for example, an existing vehicle body posture detecting sensor or the like can be used, or an appropriate detection can be performed by correcting the road surface gradient sensor according to the behavior of the vehicle such as a nose dive or a nose bump. The wheel slip sensor can be configured to make a determination by comparing, for example, detection data from wheel speed sensors provided on four wheels with detection data from a vehicle speed sensor. In addition,
For example, in the case of the driving force distribution mainly of the rear wheels, if the front wheels slip, it can be determined that all four wheels are slipping, so that the wheel slip may be detected only for the front wheels.

The differential-adjustment-type front / rear wheel torque distribution control device according to one embodiment of the present invention is configured as described above, so that the clutch torque TA proportional to the estimated engine torque and the differential between the front and rear wheels are obtained. Clutch torque TV corresponding to
And a clutch torque TX corresponding to the vehicle acceleration, the clutch torque (clutch constraint torque) T is determined by adding these.

For this reason, if there is an element for which it is desired to increase the clutch torque, this is taken in as appropriate and is reflected in the control, so that the front-rear drive distribution can be appropriately controlled according to the running state and the running environment. There is an effect that an appropriate control state is realized. In addition, in a computer constituting a controller, multiplication is generally easier to perform than addition, so that control responsiveness is improved so that a relatively low-cost, small-capacity microcomputer can sufficiently perform control. become. In addition, the control can be performed in a finer cycle, and the performance of the apparatus can be improved.

Further, since the gradient of the road surface on which the vehicle travels is taken into consideration as a control element, the restraining torque due to the engine output can be effectively used on an uphill or downhill, for example, when the load is moved. It becomes possible to prevent the differential rotation of the front and rear wheels beforehand. The map 32 of the horizontal G gain k ₁
As shown in FIG. 2, 0 may be set in consideration of the gradient, as in the map 350. In this case, the restraint torque corresponding to the front-rear rotation difference can also be used for the gradient of the road surface, and the gradient traveling performance can be further improved.

Each map of this embodiment is an example,
What is necessary is just to have the characteristic which aims, and it is not limited to the thing of this Example.

[0103]

As described above in detail, according to the differential front and rear wheel torque distribution control device of the first aspect of the present invention, the differential between the front wheel drive shaft and the rear wheel drive shaft is allowed. A center differential for distributing torque from the engine to the front wheel drive shaft and the rear wheel drive shaft, a differential limiting mechanism for limiting the differential of the center differential, and control means for controlling the differential limiting mechanism. With
The control means includes: a vehicle-body acceleration-dependent control amount element setting means for setting a control amount element according to the vehicle body acceleration; and a front-rear wheel difference rotation-related control amount element setting means for setting a control amount element according to the front and rear wheel difference rotation. An engine output corresponding control amount element setting means for setting a control amount element according to the output of the engine, and adding the respective control amount elements set by the respective control amount element setting means to perform the differential operation. With a configuration that includes a control amount setting means for setting the control amount of the limiting mechanism, it is possible to control the front-rear drive distribution with low cost, good responsiveness and close responsiveness according to the traveling state and traveling environment, There is an effect that an appropriate control state is always realized.

According to the differential-adjustment-type front / rear wheel torque distribution control device of the second aspect of the present invention, the differential between the front wheel side drive shaft and the rear wheel side drive shaft is allowed, and these front wheel side drive shafts are provided. A center differential for distributing torque from the engine to the rear wheel drive shaft, a differential limiting mechanism for limiting the differential of the center differential, and control means for controlling the differential limiting mechanism; But,
A vehicle-acceleration-dependent control amount element setting means for setting a control amount element according to the vehicle body acceleration; a front-rear wheel differential rotation-responsive control amount element setting means for setting a control amount element according to the front-rear wheel differential rotation; Control amount element setting means for setting a control amount element according to the engine output, and adding the control amount elements set by these control amount element setting means to add the control amount element to the control amount of the differential limiting mechanism. Control amount setting means for setting a control amount element corresponding to the engine output in order to prevent the front and rear wheels from rotating due to the load movement due to the gradient of the running road surface. With the configuration in which the correction unit that corrects according to the gradient of the traveling road surface is provided, in addition to the same effect as the device of the first aspect, an effect of improving the gradient traveling performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an outline of a control system of a differentially adjusted front and rear wheel torque distribution control device as one embodiment of the present invention.

FIG. 2 is a schematic block diagram showing an outline of a modified example of a control system of a differentially adjusted front and rear wheel torque distribution control device as one embodiment of the present invention.

FIG. 3 is a schematic block diagram showing a configuration of a control system of a differentially adjusted front and rear wheel torque distribution control device proposed in the process of devising the present invention.

FIG. 4 is a schematic diagram of a vehicle showing a configuration of a differential-adjustable front and rear wheel torque distribution control device proposed in the process of devising the present invention.

[Explanation of symbols]

Reference Signs List 2 engine 4 torque converter 6 automatic transmission 8 output shaft 10 intermediate gear (transfer idler gear) 12 center differential (center differential) 14 differential gear device for front wheel (front differential) 15 bevel gear mechanism 15A bevel gear shaft 15a bevel gear 16,18 front wheel 17L, 17R Front wheel axle 19 Reduction gear mechanism 19a Output gear 20 Propeller shaft 21 Bevel gear mechanism 22 Differential gear device for rear wheel (rear differential) 24, 26 Rear wheel 25L, 25R Rear wheel axle 27 Front wheel output shaft 27a Hollow Shaft member 28 Hydraulic multi-plate clutch (differential limiting mechanism) 28a Front wheel output side disk plate 28b Input side disk plate 29 Rear wheel output shaft 30, 30a, 30b, 30c Handle angle sensor (steering wheel angle sensor) 32 Alling wheel 34, 34a, 34b Lateral acceleration sensor 36 Forward / backward acceleration sensor 38 Throttle sensor 39 Engine key switch 40, 42, 44, 46 Wheel speed sensor 48 Controller 50 Antilock brake device 50A Brake switch 51 Brake pedal 52 Indicator light 54 Hydraulic source 56 Pressure control valve system (pressure control valve) 121 Sun gear 122 Planetary pinion (planetary gear) 123 Ring gear 124 Input case 125 Planet carrier 160 Shift lever position sensor (shift range detecting means) 170 Engine speed sensor 180 Transmission speed sensor 200A Front and rear wheels Differential rotation control amount element setting means 203A Vehicle acceleration corresponding control amount element setting means 246 Correction means 258 Switch 260A Engine Output corresponding control quantity element setting unit 260B, 260C correcting means 260D maximum value selecting means 310A, 310B limiter 320-350 control gain map 380 control amount setting means 380A, 380B adder

Claims (2)

(57) [Claims] 1. A center differential for allowing a differential between a front wheel side drive shaft and a rear wheel side drive shaft and distributing torque from an engine to the front wheel side drive shaft and the rear wheel side drive shaft, and the center differential. And a control means for controlling the differential limiting mechanism, wherein the control means sets a control amount element according to the vehicle acceleration. A front-rear wheel differential rotation corresponding control amount element setting means for setting a control amount element according to front and rear wheel differential rotation; and an engine output corresponding control amount element setting means for setting a control amount element according to the output of the engine. And control amount setting means for setting the control amount of the differential limiting mechanism by adding the control amount elements set by the control amount element setting means. A differential-adjustment-type front and rear wheel torque distribution control device. 2. A center differential for allowing a differential between the front wheel drive shaft and the rear wheel drive shaft and distributing torque from the engine to the front wheel drive shaft and the rear wheel drive shaft, and the center differential. And a control means for controlling the differential limiting mechanism, wherein the control means sets a control amount element according to the vehicle acceleration. A front-rear wheel differential rotation corresponding control amount element setting means for setting a control amount element according to front and rear wheel differential rotation; and an engine output corresponding control amount element setting means for setting a control amount element according to the output of the engine. Control amount setting means for setting the control amount of the differential limiting mechanism by adding each control amount element set by each of these control amount element setting means; The gin output corresponding control amount element setting means includes a correction means for correcting the control amount element according to the engine output in accordance with the slope of the running road surface, in order to prevent the front and rear wheel differential rotation caused by the load movement due to the slope of the running road surface. A differentially-adjustable front and rear wheel torque distribution control device, which is provided.