JPH0424122A - Driving force distribution controlling type four-wheel drive automobile - Google Patents

Abstract

PURPOSE:To make it hard to be affected by a disturbance as well as to enable it to perform stable control by calculating an actual speed difference between both front-and rear-wheel sides, and controlling a transfer torque regulating mechanism so as to make transfer torque capacity to the wheels correspond to the calculated speed difference. CONSTITUTION:A controller 48 calculates an equation of DELTAN(=NR-NF from rotational speed NF of a front wheel side output shaft and speed NR of a center differential 12 detected by speed sensors 60, 62, and an engine speed difference calculating part 48b. In addition, at a target engine speed difference calculating part 48a, a desired value (target speed difference) DELTAN0of a speed difference between both front-wheel side and rear-wheel side output shafts of the center differential 12 should be set. In addition, a hydraulic multiple disk clutch 28 as a transfer torque regulating mechanism is controlled by a torque control part 48c so as to make an actual speed difference DELTAN converge on the target engine speed difference DELTAN0 on the basis of each information out of the target engine speed difference calculating part 48a and the engine speed difference calculating part 48b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-wheel drive vehicle, and more particularly to a four-wheel drive vehicle with driving force distribution control that enables stable distribution of driving force.

[Prior Art] Conventionally, four-axle drive vehicles have been proposed in which the distribution of transmission torque between front wheels and rear wheels is controlled in accordance with driving conditions.

As a driving force distribution means for such a four-wheel drive vehicle,
For example, a device in which a differential limiting device such as a VCU (viscous coupling unit) is attached to the center differential to appropriately regulate the difference in rotation speed of the center differential;
Devices such as hydraulic multi-plate clutches have been developed that can adjust the power transmission state according to the control oil pressure.

[Problems to be Solved by the Invention] By the way, in the above-mentioned four-wheel drive vehicle, there is a need to be able to control the distribution of driving force stably with a margin against external disturbances during general driving.

The present invention was devised in view of the above-mentioned problems, and provides a four-axis drive vehicle with driving force distribution control, which is less susceptible to external disturbances and can perform stable control in this type of power transmission device. The purpose is to provide.

[Means for Solving the Problems] Therefore, the driving force distribution control type four-axle drive vehicle according to the first aspect of the present invention can drive the vehicle by transmitting the output torque of the engine to the front wheels and the rear wheels. A four-axle drive vehicle, comprising: a transmission torque adjustment mechanism that distributes the output torque between the front wheels and the rear wheels; Rear wheel side rotational speed detection means for detecting the rotational speed of the side rotating portion, and rotational speed difference calculation means for calculating the actual rotational speed difference between the front wheel side and the rear wheel side based on information from each of these detection means. and a torque control means for controlling the transmission torque adjustment mechanism so that the transmission torque capacity to the wheels corresponds to the rotational speed difference calculated by the rotational speed difference calculation means.

Further, the driving force distribution control type four-wheel drive vehicle according to the second aspect of the present invention is a four-axle drive vehicle that can drive the vehicle by transmitting the output torque of the engine to the front wheels and the rear wheels. A transmission torque adjustment mechanism is provided to distribute the transmission torque between the front wheels and the rear wheels, and the final reduction ratio ρf of the front wheels and the dynamic load radius r of the front wheels are provided.
The relationship between (ρt/rf) < (ρr・ρt/rr) is established between f, the final reduction ratio ρ7 of the rear wheels, the dynamic load radius rr of the rear wheels, and the transfer ratio ρr. Front wheel side rotational speed detection means for detecting the rotational speed of the rotating part on the front wheel side; Rear wheel side rotational speed detection means for detecting the rotational speed of the rotating part on the rear wheel side;
Rotational speed difference calculation means for calculating the actual rotational speed difference between the front wheel side and the rear wheel side based on the information from each of these detection means;
Target rotational speed difference calculation means for setting a target value of the rotational speed difference between the front wheels and the rear wheels that occurs depending on the torque transmission state by setting the final reduction ratio, the dynamic load radius, and the transfer ratio; The present invention is characterized by comprising a torque control means for controlling the transmission torque adjustment mechanism so that the rotational speed difference converges to the target rotational speed difference.

[Function] In the four-wheel drive vehicle with spurious force distribution control according to the first aspect of the present invention, the rotational speed difference calculation means calculates the difference based on the information from the front wheel rotational speed detection means and the rear wheel rotational speed detection means. The torque control means calculates the actual rotation speed difference between the front wheel side and the rear wheel side, and the torque control means adjusts the transmission torque so that the transmission torque capacity to the axle corresponds to the rotation speed difference calculated by the rotation speed difference calculation means. control.

Further, in the driving force distribution control type four-wheel drive vehicle according to the second aspect of the present invention, the rotational speed difference calculation means calculates the rotational speed of the front wheel based on the information from the front wheel rotational speed detection means and the rear wheel rotational speed detection means. The actual rotational speed difference between the front wheel side and the rear wheel side is calculated, and the target rotational speed difference calculation means calculates the difference that may occur depending on the torque transmission state by setting the final reduction ratio, dynamic load radius, and transfer ratio of the front wheel side and rear wheel side. A target value for the rotational speed difference between the front wheels and the rear wheels is set, and the torque control means controls the transmission torque adjustment mechanism so that the actual rotational speed difference converges to the target rotational speed difference.

[Example] Hereinafter, a driving force distribution control type four-wheel drive vehicle as an example of the present invention will be described in detail with reference to the drawings.
The figure is a schematic overall configuration diagram, Figure 2 is a flowchart regarding the driving force distribution control, Figures 3 to 6 are graphs showing the characteristics of the driving force distribution control, and Figures 7 and 8 are respectively driving force distribution. FIG. 9 is a diagram showing the control oil pressure for control, and FIG. 9 is a schematic overall configuration diagram showing a modification of the driving force distribution control type four-wheel drive vehicle of the present invention.

In FIG. 1, reference numeral 2 denotes an engine, and the output of the engine 2 is transmitted to an output shaft 8 via a torque converter 4 and an automatic transmission 6. The output of the output shaft 8 is transmitted via an intermediate gear 10 to a planetary gear type differential device t (center differential).
12.

The output of this planetary gear type differential 12 is transmitted on the one hand to a reduction gear mechanism 19. The transmission is transmitted from the axles 17L, 17R to the left and right front wheels 16.18 via the front wheel differential gear mechanism 14, and the bevel gear mechanism 15. Propeller shaft 20 and bevel gear mechanism 21. Differential amount vehicle equipment for rear wheels W2
2 from the axles 25L and 25R to the left and right rear wheels 24.2
6. The planetary gear type differential device 12 includes a sun gear 12a, a planetary gear 12b disposed outside the sun gear 12a, and a ring gear 12c disposed outside the planetary gear 12b, as in the conventionally known one. In addition, a carrier 12d supports the planetary gear 12b.
The output of the output shaft 8 of the automatic transmission 6 is input to the sun gear 12a, and the ring gear 12c is linked to the front differential gear N14, and the ring gear 12c is linked to the propeller shaft 20.

Furthermore, a hydraulic multi-plate clutch 28 whose frictional force changes depending on the pressure applied to its own hydraulic chamber is interposed between the ring gear 12c and the carrier 12d.

Therefore, the planetary gear type differential device 12 can control the torque transmitted to the front wheels and the rear wheels by appropriately controlling the hydraulic multi-disc clutch 28 from a completely free state to a locked state. .

Further, numeral 30 is a steering sensor that detects the rotation angle of the steering wheel 32 from the neutral position, that is, the steering angle O8, 34 is a lateral acceleration sensor that detects lateral acceleration GV acting on the vehicle body, and 36 is a sensor that detects the lateral acceleration GV acting on the vehicle body. A longitudinal acceleration sensor that detects acceleration GX in the longitudinal direction; 38 is the engine 2;
a throttle sensor for detecting the throttle opening θT of 3;
9 is the engine key switch of engine 2, 40.42.
44 and 46 are wheel speed sensors that detect the rotation speeds of the right front wheel 16, the right front wheel 18, the left rear wheel 26, and the right rear wheel 28, respectively, and the outputs of these switches and each sensor are input to the controller 48.

Reference numeral 50 denotes an anti-lock brake device, and the anti-lock brake device 50 is configured such that when the anti-lock brake device 50 outputs an anti-lock brake activation signal, a signal indicating the state thereof is input to the controller 48. 52 is a warning light that lights up based on a control signal from the controller 48.

Reference numeral 54 indicates a hydraulic pressure source, and 56 indicates a pressure control valve interposed between the hydraulic pressure source 54 and the hydraulic chamber of the hydraulic multi-disc clutch 28, and the pressure control valve 56 is controlled by a control signal from the controller 48. Ru.

Further, reference numeral 60 is a front wheel rotation speed sensor (rotation speed) that detects the rotation speed (rotation speed) NF of the front wheel output shaft of the center differential 12.
62 is a rear wheel rotation speed sensor (rear shaft rotation speed detection means) that detects the rotation speed (rotation speed) NR of the rear wheel output shaft of the center differential 12.

By the way, the final reduction ratio of the front wheels is ρ8. Front wheel dynamic load radius rf
+Rear wheel final reduction ratio ρr. The dynamic load radius rr of the rear wheels and the transfer ratio ρ are generally Cpt/rf)
= (ρr・ρt/rr), but in the drive system of this car, under all driving conditions, (ρi/rf)< (ρr・ρ,/rr)...・
The settings are made so that the relationship (1) holds true.

Note that the final reduction ratio ρf of the front wheels relates to, for example, the reduction gear mechanism 19, and the final reduction ratio ρr of the rear wheels relates to, for example, the bevel gear mechanism 21.
Regarding this, the transfer ratio ρr is a value related to the bevel gear mechanism 15, for example.

In general, since the dynamic load radius rf of the front wheels is equal to the dynamic load radius rr of the rear wheels, Equation 1 (1) is expressed as ρf×ρr゛ρ
t --------(1).

With this setting, if both the front wheels and the rear wheels are not slipping, the rotational speed of the rear wheels of the clutch disk of the hydraulic multi-disc clutch 28 will be faster than the rotational speed of the front wheels. For this reason, the hydraulic multi-plate clutch 28
When the pressure in the hydraulic chamber is increased to connect the clutch, the rotation will normally shift from the rear wheel to the front wheel based on this difference in rotation between the front wheel side clutch disk and the rear wheel side clutch disk. Torque transmission takes place. In this case, the transmitted torque capacity has a size corresponding to the decrease in the rotational difference between both clutch disks, that is, a size corresponding to the size of the actual rotational difference and the contact pressure between both clutch disks.

In addition, FIG. 3 is a characteristic diagram showing the relationship between the front-rear driving force distribution ratio and the control oil pressure when the clutch 28 transmits torque from the rear wheels to the front wheels, and FIG. FIG. 2 is a characteristic diagram showing the relationship between engine torque and clutch transmission torque when torque is transmitted to the clutch. Also,
FIG. 5 is a characteristic diagram showing the relationship between the front-rear driving force distribution ratio and the control oil pressure when the clutch 28 transmits torque from the front wheels to the rear wheels, similar to FIG. 3, and FIG.
8 is a characteristic diagram similar to FIG. 4 showing the relationship between engine torque and clutch transmission torque when torque is transmitted from the front wheels to the rear wheels.

When transmitting torque from the rear wheels to the front wheels, as shown in FIG.
When the control oil pressure is zero and it is completely free, 32
: Approximately 68 (this value varies depending on the load balance between the front and rear wheels, etc., but is generally around this value)
It can be seen that as the control oil pressure increases, the proportion of driving force distributed to the front wheels increases. In particular, when the engine torque TE is small, a slight increase in the control oil pressure will significantly increase the proportion of driving force distributed to the front wheels.As the engine torque TE increases, the proportion of driving force distributed to the front wheels increases. A large amount of control oil pressure is required to increase this, and it is also difficult to significantly increase the proportion of drive force distributed to the front wheels, but the drive force distribution is adjusted little by little in response to changes in control oil pressure.

It is easy to reliably adjust to the target driving force distribution.

Furthermore, as shown in FIGS. 4 and 6, it can be seen that in order to obtain a constant driving force distribution, a clutch transmission torque proportional to the engine torque is required.

On the other hand, when torque is transmitted from the front wheels to the rear wheels, as shown in FIG. 5, the variable range of driving force distribution is narrow, and moreover, it is not possible to distribute the torque closer to the front, which is not preferable.

Therefore, the setting is made so that inequality (1) holds true so that torque can be transmitted from the rear wheels to the front wheels.

With this setting, the torque distribution to the front wheels can be made much larger than that to the rear wheels, and the torque distribution ratio at which the torque to the front wheels is maximized is the above-mentioned (ρf/rf).
By setting the value of and the value of (ρr"ρt/rr), the torque distribution to the front wheels can be significantly increased.
0:O or more (e.g. 120 knees 20)
It can also be set to . Therefore, for example, the torque distribution ratio (front wheels:rear axle) can be adjusted over a very wide range from 33:67 to 100:0.

Although not shown, the controller 48 includes a CPU, ROM, RAM, interface, etc. necessary for control described later, and includes a target rotational speed difference calculation section (target rotational speed difference calculation means) 48a, and a rotational speed difference calculation section (target rotational speed difference calculation means) 48a. 48b (rotational speed difference calculation means), and a torque control section (torque control means) 48c that controls the hydraulic multi-disc clutch 28 as a transmission torque adjustment mechanism.

In the rotational speed difference calculation unit 48b, the rotational speed sensor 60.62
ΔN (=NR
NF) is calculated.

Further, the target rotational speed difference calculation unit 48a sets a target value (target rotational speed difference) ΔN0 of the rotational speed difference (rotational speed difference) between the front wheel side output shaft and the rear wheel side output shaft of the center differential 12. This target rotation speed difference ΔN is the steering wheel angle (steering angle) θH2 and the vehicle body speed V.

It can be determined based on the running condition of the vehicle, such as the vehicle body acceleration V'.

In other words, the target rotational speed difference ΔN, is determined by each of these values θ, .
Function ΔNo=f(θH2v, v') of V and V'... (2)
It can be shown as

The reason for setting the target rotational speed difference ΔN0 in this way is as follows.

As mentioned above, in the drive system of this automobile, when no slip occurs in the wheels, a rotational speed difference occurs between the front wheel output shaft and the rear wheel output shaft of the center differential 12. , when the clutch 28 is connected, this clutch 28
Torque is transmitted from the rear wheel side to the front wheel side through the clutch 28, and the torque distribution between the front and rear wheels is adjusted, but the above-mentioned rotational speed difference also changes depending on the capacity of the torque transmitted through the clutch 28 at this time. Therefore, in order to set the torque distribution between the front wheels and the rear wheels to be optimal for the driving conditions, focus on the rotational speed difference between the front wheel side output shaft and the rear wheel side output shaft of the center differential 12. It is conceivable to control this rotational speed difference so that it takes a value corresponding to the optimal glare force distribution state.

The distribution state of the driving force can be determined by the running state of the vehicle such as the steering wheel angle θH2, the vehicle body speed V, and the vehicle body acceleration V', so as mentioned above, the rotational speed difference ΔN,
Each of these values θH+V+V' can be expressed as a function [see equation (2)].

Also, from another point of view, when torque is transmitted through the clutch 28, slip occurs in the front wheels and rear wheels, but when the slip of these wheels is in an optimal state, that is, each wheel has an optimal slip. The theoretical ΔN on the center differential that occurs when the engine speed is at a certain speed is determined by the vehicle's driving condition. It can also be said that such a theoretical ΔN is set as the rotational speed difference ΔNo.

The torque control unit 48c controls the hydraulic pressure as a transmission torque adjustment mechanism so that the actual rotational speed difference ΔN converges to the target rotational speed difference ΔN0 based on the upward information from the target rotational speed difference calculation unit 48a and the rotational speed difference calculation unit 48b. Controls the multi-disc clutch 28.

Specifically, as shown in FIG.
The control oil pressure P of No. 8 is set according to the actual rotational speed difference ΔN.

In other words, the actual rotational speed difference ΔN becomes the target rotational speed difference ΔN, (
>O), the control oil pressure P is changed to the difference D between the actual rotational speed difference ΔN and the target rotational speed difference ΔN0 (=ΔN−ΔN
. ), set (p=αD) so that the actual rotational speed difference ΔN is smaller than the target rotational speed difference ΔN0 and 0.
If it is above (range indicated by K1), the control oil pressure P is set to O, and if the actual rotational speed difference ΔN is less than or equal to O, the control oil pressure P
is set as (p=-βΔN) according to the magnitude of ΔN.

Furthermore, when the target rotational speed difference ΔNo is negative (ΔN0<O), it is possible to set the control oil pressure P as shown in FIG. 8, but in this case, the reaction to rear wheel slip will deteriorate, Unfavorable in terms of steering stability.

Note that the reason why the oil pressure is set to 0 and differential restriction is not performed in the range shown by K-xtKz is that if differential restriction is performed in this case, torque will be further distributed to the slipping wheels, which is undesirable.

Therefore, in general, the target rotational speed difference ΔNo is set to be positive, that is, the rotational speed NR of the rear wheel output shaft of the center differential 12 is set larger than the rotational speed NF of the front wheel output shaft, as shown in FIG. The oil pressure P is controlled as shown in FIG.

While adjusting the oil pressure P in this manner, the torque control unit 48c controls the connection state of the hydraulic multi-disc clutch 28 so that the actual rotational speed difference ΔN converges to the target rotational speed difference ΔN.

Next, the content of such control will be explained according to the flowchart shown in FIG.

Each control element, etc. is initialized (step Sl), and if the engine is not turned off, the process proceeds from step S2 to step S3, where the steering wheel angle θH2, vehicle speed V, vehicle acceleration v', shaft rotation speed NFe, NR, etc. Read the signal (detected data).

Then, the rotational speed difference calculation unit 48b calculates the shaft rotational speed NFy.
The actual differential rotation speed (actual rotation speed difference) ΔN is calculated from NR (step S4), and the target rotation speed difference calculation unit 48a calculates the target differential rotation speed (target rotation (speed difference) ΔN is calculated (step S5).

Further, in step S6, it is determined whether the actual rotational speed difference ΔN is 0 or less, and if ΔN is not 0 or less, in step S7, it is determined whether the actual rotational speed difference ΔN is greater than or equal to the target rotational speed difference ΔN0 ( In other words, whether ΔN−ΔN,>O or not) is determined, and these steps S6. At S7's discretion,
If ΔN<O, the process advances to step S9, and the control oil pressure P of the hydraulic multi-disc clutch 28 is set to P=-βΔN.
The control oil pressure P of the hydraulic multi-disc clutch 28 is set to P=0, and if ΔN<ΔN, the process proceeds to step S10, and the control oil pressure P of the hydraulic multi-disc clutch 28 is set to P=α(ΔN−ΔN,).

Then, the pressure control valve 5 is adjusted so that these set oil pressures are achieved.
Hydraulic pressure is controlled through 6 etc.

As a result, feedback control is performed so that the actual rotational speed difference ΔN converges to the target rotational speed difference ΔN, and the torque distribution between the front and rear axles is always appropriately adjusted so that each wheel always maintains the optimal slip ratio state. I started running while doing so. As a result, the driving force distribution control is not performed in an unstable direction, and the driving force distribution control can be performed stably.

In addition, in the above-mentioned embodiment, the case where the hydraulic multi-disc clutch 28 for differential limiting was combined with the center differential 12 was explained, but the structure of the present invention can also be applied to a transfer clutch as shown in FIG. .

In FIG. 9, reference numeral 11 is a front wheel clutch for driving the front wheels, and 13 is a rear wheel clutch for driving the rear wheels. It is controlled in substantially the same way as the clutch 28. Note that the other parts are configured almost the same as in the embodiment (see FIG. 1), so explanations will be omitted.

In other words, in this case, a target value for the difference between the rotational speed of the front wheel output shaft and the rotational speed of the rear wheel output shaft in one part of the transfer is set so that the actual rotational speed difference converges to the target rotational speed difference. , the control oil pressure of both clutches 11.13 is set to control the engagement state of both clutches 11.13.

In addition, on each side mentioned above, control is based on the rotation difference in the center differential or transfer part, but since the axle also rotates in response to the rotation of these parts, the hydraulic pressure is controlled based on the rotation speed of the wheels. may be controlled. That is, the actual rotational speed difference between the front and rear wheels is calculated from the detected values of the wheel speed sensors 40 to 46, and a target value for the rotational speed difference between the front and rear wheels is set, and the actual rotational speed difference is calculated from the target rotational speed difference. The control oil pressure is set so that it converges to .

This also provides the same effects and effects as described above.

[Effects of the Invention] According to the four-wheel drive vehicle with driving force distribution control according to the first and second claims of the present invention, the driving force distribution control is not performed in an unstable direction, and the driving force distribution is improved. This has the advantage that control can be performed stably and the performance of a four-wheel drive vehicle can be greatly improved.

[Brief explanation of the drawing]

Figures 1 to 9 show a four-wheel drive vehicle with driving force distribution control as an embodiment of the present invention. Figure 1 is a schematic overall configuration diagram thereof, and Figure 2 is related to its driving force distribution control. The flowchart, Figures 3 to 6 are graphs showing the characteristics of the driving force distribution control, Figures 7 and 8 are diagrams showing the control oil pressure of the driving force distribution control, respectively, and Figure 9 is a graph showing the driving force distribution of the present invention. FIG. 3 is a schematic overall configuration diagram showing a modified example of a controlled four-wheel drive vehicle. 2-engine, 4-torque converter, 6-automatic transmission, 8-output shaft, 10-intermediate gear, 12--planetary gear differential W (center differential), 14-differential gear for front shaft Device, 15-Bevel gear mechanism, 16.18-Front wheel, 17
L, 17R - axle, 19 - reduction gear mechanism, 20 - propeller shaft, 21 - bevel gear mechanism, 22 - differential gear mechanism for rear wheels. 24.26-Rear wheel, 25L, 25R-Axle, 28-Hydraulic multi-plate clutch as differential limiting mechanism, 30-Steering sensor, 34-Lateral acceleration sensor, 36-Longitudinal acceleration sensor, 3
8-throttle sensor, 39-engine key switch,
4o, 42.44.46-Wheel speed sensor, 48-Controller, 50-Anti-lock brake device, 52-Warning light, 54--Hydraulic pressure source, 56-Pressure control valve, 60-Front wheel rotation speed sensor ( front wheel side rotation speed detection means), 62-rear shaft side rotation speed sensor (rear wheel side rotation speed detection means).

Claims (2)

[Claims] (1) A four-wheel drive vehicle that can drive the vehicle by transmitting the output torque of the engine to the front wheels and the rear wheels, which is equipped with a transmission torque adjustment mechanism that distributes the output torque between the front wheels and the rear wheels; Front wheel side rotational speed detection means for detecting the rotational speed of the rotating part on the front wheel side, rear wheel side rotational speed detection means for detecting the rotational speed of the rotating part on the rear wheel side, and information from each of these detection means. a rotational speed difference calculation means for calculating an actual rotational speed difference between the front wheel side and the rear wheel side based on the rotational speed difference calculation means; A four-wheel drive vehicle with driving force distribution control, characterized by comprising a torque control means for controlling a transmission torque adjustment mechanism. (2) In a four-axle drive vehicle that can drive the vehicle by transmitting the output torque of the engine to the front wheels and the rear wheels, the front wheels are equipped with a transmission torque adjustment mechanism that distributes the output torque between the front wheels and the rear wheels. final reduction ratio ρ_f and front wheel dynamic load radius r_
Between f, the final reduction ratio ρ_r of the rear wheels, the dynamic load radius r_r of the rear wheels, and the transfer ratio ρ_t, (ρ_f/r_f)
<(ρ_r・ρ_t/r_r), and a front wheel side rotation speed detecting means for detecting the rotation speed of the rotating portion on the front wheel side, and a rotation speed detecting means for detecting the rotation speed of the rotating portion on the rear wheel side. a rear wheel side rotational speed detection means for detecting, a rotational speed difference calculation means for calculating an actual rotational speed difference between the front wheel side and the rear wheel side based on information from each of these detection means, the final reduction ratio, A target rotation speed difference calculating means for setting a target value of a rotation speed difference between a front wheel side and a rear wheel side that may occur depending on a torque transmission state by setting a dynamic load radius and a transfer ratio; A four-wheel drive vehicle with driving force distribution control, comprising: torque control means for controlling the transmission torque adjustment mechanism so as to converge to a rotational speed difference.