JPH0260841A - Device for controlling differential limiting force - Google Patents

Abstract

PURPOSE:To secure optimum running performance by setting up a differential limiting force control means at a reference value for the quantity of drive slipping to be great at the time of low vehicle speed running and of cornering with a small cornering radius. CONSTITUTION:In a vehicle equipped with a differential limiting force control means 4 which enables the joining force control of a differential limiting clutch 1 to control the differential limiting force between a right and a left driving wheel 2 and 3 in such a way as to be freely changeable, the vehicle is provided with at least one out of a drive slipping quantity detecting means 5 detecting the quantity S of the drive slipping of the driving wheels 2 and 3, a vehicle speed detecting means 6 detecting the vehicle speed V of the vehicle and a cornering radius detecting means 7 detecting a cornering radius R. The differential limiting force control means 4 outputs a signal to reduce the differential limiting force when the quantity S of the drive slipping of the driving wheels 2 and 3 exceeds a reference value So at the time of vehicle running to which the differential limiting force is imparted, and concurrently the means sets up the reference value So at a great one when the vehicle speed V or the cornering radius R is small, and also sets up the value at a small one when the vehicle speed V or the cornering radius R is large.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a differential limiting force control device that variably controls differential limiting force between left and right drive wheels by external clutch engagement force control.

(Prior art) Conventionally, a differential eye control III device uses a hydraulic flanch as a differential limiting clutch, and the clutch engagement pressure is variably controlled by an external hydraulic control means, so that the clutch engagement pressure is proportional to the clutch engagement pressure. A device for controlling the related differential limiting force is known (for example, JP-A-62-103226).

(Problem to be Solved by the Invention) However, in such a conventional differential limiting force control device, the differential limiting force is controlled in a direction that matches the actual outer wheel slip ratio or the target outer wheel slip ratio. The system is configured to increase, decrease, or cancel the differential limiting force based only on the slip ratio, and with regard to vehicle speed and turning radius, it is possible to obtain favorable driving performance based on the most frequent vehicle speed and turning radius using a general method. It was set up so that

For this reason, especially in sporty vehicles, when starting acceleration or power drift driving by accelerator operation is required, such as when driving at low speeds or when driving with a small turning radius, the differential limiting force may be too low and the starting speed may be reduced. Problems arise in that the drive wheels may be allowed to spin at times, and that turning performance is poor when entering a corner with the accelerator on.

In addition, when driving stability is required, such as when driving at high speeds or when driving with a large turning radius, the differential limiting force may be too high.
When cornering, a problem arises in that the tire cornering force of the drive wheels (particularly on the outer wheels) decreases, causing instability in vehicle behavior.

The present invention was made in view of the above-mentioned problems and the fact that the slip ratio that allows the driver to drive without anxiety depends on the vehicle speed or turning radius. The objective is to develop a differential limiting force control device that can improve driving performance.

(Means for Solving the Problems) In order to solve the above problems, in the differential limiting force control device of the present invention, when setting the reference value of the drive wheel slip value for reducing the differential limiting force, Made it dependent.

That is, as shown in the diagram corresponding to the claims in FIG. In the vehicle equipped with the drive slip I detection means 5 for detecting the drive slip fts of the drive wheels 2.3, the vehicle speed detection means 6 for detecting the vehicle speed V of the vehicle, and the turning radius detection means Y for detecting the turning radius R. At least one of these is provided, and the differential limiting force control means 4 controls the drive slip EMS of the drive wheels 2.3 or the reference value S when driving with the differential limiting force applied. If it exceeds the reference value S, a signal is output to reduce the differential limiting force. is characterized in that it is set to a large value when the vehicle speed V or the turning radius R is small, and is set to a small value when the vehicle speed V or the turning radius R is large.

Incidentally, the differential limiting force control means 4 has a reference value S. It is also possible to set the value to be increased as the lateral acceleration Y9 increases.

(Function) At low vehicle speeds or when turning with a small turning radius, the differential limiting force control means 4 sets the reference value So of the drive slip H5 to a large value.

This standard value S. With this setting, when driving with the differential limiting force applied, the drive slip amount S of the drive wheels 2 and 3 reaches the reference value S0.
The differential limiting force control is performed without reducing the differential limiting force until it exceeds the differential limiting force, that is, the differential limiting force is controlled to be higher.

At high vehicle speeds or when turning with a large turning radius, the drive slip H3 or reference value So is set to a small value in the differential limiting force control means 4.

By setting this reference value S0, when driving with the differential limiting force applied, the drive slip amount S of the drive wheels 2 and 3 is set to the reference value S0.
As soon as the differential limiting force is exceeded, control is performed to reduce the differential limiting force, that is, control is performed to reduce the differential limiting amount.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, the configuration will be explained.

As shown in FIG. 2, the rear wheel drive vehicle to which the differential limiting force control device of the embodiment is applied includes an engine 10, a transmission 11, a propeller shaft 12, a differential 13, a drive shaft 14, +5, rear wheels +6. 17,
It has a front wheel of 18.19.

The left and right rear wheels 16.
The differential limiting force control that variably controls the differential limiting force in step 7 is to set the pressurized oil from the external hydraulic source 30 to a predetermined clutch engagement pressure via the hydraulic control valve 31 and guide it to the differential limiting clutch 20. It will be held in

A predetermined differential limiting command current value ■ to the hydraulic control valve 31
The controller 32 outputs a memory circuit (RAM,
This controller 32 is an electronic control circuit including a ROM), an arithmetic processing circuit (CPU), etc.
3, lateral acceleration sensor 34, right rear wheel speed sensor 35, left rear wheel speed sensor 36, right front wheel speed sensor 37, and left front wheel speed sensor 3
Detection signals from 8 V, Yg, NRR, NRL,
NFR and NFL are input.

Next, the effect will be explained.

First, the flow of the differential limiting control operation in the controller 32 will be described based on the flowchart shown in FIG.

In step 100, vehicle speed V, lateral acceleration Y9, right rear wheel speed NRR, left rear wheel speed N, , right front wheel speed N, Il, and left front wheel speed NF are read.

In step 101, a differential limiting force command value P79 is calculated based on the lateral acceleration Y9.

The relationship between the differential limiting force command value P7g and the lateral acceleration Y9 is such that the differential limiting force command value pvg increases in proportion to the lateral acceleration Y9, as shown in FIG.

In step 102, the driving wheel slip speed ΔN is calculated from the difference between the driving outer wheel speed Nll0UT and the non-driving wheel speed NF.

The driving outer wheel speed NROUT is determined by determining the inner turning wheel and the outer turning wheel based on the direction of occurrence of the lateral acceleration Y9, and determining the right rear wheel speed NR.
It is determined by selecting the rear wheel speed on the outer wheel side from R and the left rear wheel speed, and the non-driven wheel speed N is determined by the average value of the right front wheel speed NFR and the left front wheel speed NFL. .

In step 103, the vehicle speed V and the driving wheel slip speed △N
The differential limiting force reduction value PN is calculated from the lateral acceleration Y9 and the V-ΔN-Y9 map shown in FIG.

Here, the V-△N-Y9 map shown in FIG.
Based on the map based on the map, up to a predetermined type J
. If it exceeds, the driving wheel slip speed Δ is independent of the vehicle speed V.
When N is constant, the differential limiting force reduction value PN becomes a constant value.

In addition, the value of the differential limiting force reduction value PN determined by the vehicle speed V and the driving wheel slip speed ΔN is modified by the lateral acceleration Y9, and when turning at high speed on a high friction coefficient road, etc., the value of the differential limiting force reduction value PN is When L2. As L3 shifts and the PN range expands, the differential limiting force reduction value PN tends to decrease at the same vehicle speed V and driving wheel slip speed ΔN.

In addition, (PN20) < (PN = 1) < (PN = 2) < (
P N = 3).

In step 104, a final differential limiting force command value P* is calculated from the difference between the differential limiting force command values P, 9 and the differential limiting force reduction value PN.

The calculation formula is P*=PYg-PN.

However, when P* is negative, P*=○.

In step 105, the current value I from which the final differential limiting force command value P* is obtained is output to the hydraulic control valve 31.

Next, the operation during driving will be explained.

(a) Predetermined vehicle speed V when traveling at low vehicle speed. When the vehicle is running at the following low speeds, as shown in the map in Figure 5, the lower the vehicle speed V is, the more the driving wheel slip speed ΔN does not become a large value, which is the limit that becomes the reference value for differential limiting force reduction. It doesn't reach the line.

That is, when the vehicle is traveling at a low speed, control is performed to continue applying differential limiting force in accordance with the lateral acceleration Y9 until a considerable amount of drive wheel slip occurs.

Therefore, when the vehicle is running at low speed, by controlling the differential limiting force to the ON side, it is possible to effectively prevent the drive wheels from spinning when starting in a straight direction, and when making a power drift turn by depressing the accelerator from a low speed state, the inner wheel By preventing the release of driving force from the tire and actively causing the outer drive wheel to slip, it is possible to reduce the knurling force of the tire and improve its turning performance.

(b) Predetermined vehicle speed V when traveling at high vehicle speed. When the vehicle is running at a high speed that exceeds 1, as shown in the map in Figure 5, regardless of the vehicle speed V, if the drive wheel slip speed △N reaches a small predetermined value - 8 No, this is the standard value for reducing the differential limiting force. The boundary line L1 is reached.

In other words, when the vehicle is running at a high speed, control is performed to reduce the differential limiting force without sufficiently allowing the occurrence of drive wheel slip.

Therefore, when the vehicle is running at a high speed, by controlling the differential limiting force to the OFF side, the amount of drive slip on the outer wheel side is reduced, the cornering force of the tires is prevented from being reduced, and the stability of vehicle behavior when turning can be improved.

This is because by applying differential limiting force, the drive torque that is originally transmitted from the high-speed inner wheel to the low-speed outer wheel, which tends to spin away from the road surface when turning, is reduced by the differential limiting force. In other words, the drive torque transmitted from the inner wheel side to the outer wheel side by applying the differential limiting force is suppressed by the reduction in the differential limiting force. Therefore, when turning, the occurrence of slip on the outer wheels is suppressed, and sufficient cornering force is ensured.

(c) Effects associated with lateral acceleration In the differential limiting force reduction value map shown in FIG. 5, the larger the lateral acceleration Y9, the higher the boundary lines L1 and L2.13 move upward. As a result, even if the vehicle speed V and driving wheel slip speed ΔN are the same, the differential limiting force reduction value PN
The value becomes larger as the lateral acceleration Y9 becomes smaller.

This is to reduce the differential limiting force early if the drive wheels easily spin even at a low lateral acceleration of Y9, resulting in unstable vehicle behavior caused by the above-mentioned slipping of the outer turning wheels during high-speed turns. This is to prevent

That is, when the vehicle speed V and the drive wheel slip speed ΔN are at the position of point A in FIG. When L3 is selected from two, differential limiting force reduction value PN or PN=1 is generated, but due to the increase in lateral acceleration Y9, each boundary line, L2. When L3 is moved to the dotted line position or selected, the differential limiting force reduction value PN is PN=0, and the differential limiting force is not reduced.

Although the embodiments have been described above based on the drawings, the specific configuration is not limited to these embodiments, and any changes or additions that do not depart from the gist of the present invention are included in the present invention. It will be done.

For example, in the embodiment, as shown in FIG. 5, the differential limiting force reduction value map was shown with vehicle speed V on the horizontal axis, but instead of this vehicle speed V, as shown in FIG. A differential limiting force reduction value map may be used in which the turning radius R is taken as the horizontal axis.

Note that the turning radius can be determined by calculating the formula R=V'/f(Yg) using the vehicle speed V and the centripetal acceleration f(Y9).

Also, as a differential limiting force reduction value map, instead of the characteristic line drawn as a straight line as shown in Figs.
It is also possible to use a curved characteristic line as shown in the figure.

In addition, in the embodiment, as shown in FIG. 4, control based on lateral acceleration was shown as the basic control of differential restriction, but vehicle status/information other than lateral acceleration, such as engine torque (
The determination may be made based on the throttle opening (judgment based on the throttle opening).

In addition, in the embodiment, an example was shown in which the drive slip speed based on the difference between the drive outer wheel speed and the non-drive wheel speed was used as the drive wheel slip amount, but the outer wheel slip ratio may also be used. In order to simplify the control by omitting the discrimination between the inner and outer wheels, etc., the slower speed side of the left and right wheels of the drive wheels may be used as the drive wheel speed.

Even if you select the slower side in this way, you can still obtain the speed of the wheels where the driving torque is transmitted to the road surface, that is, the outer wheels (the inner wheels that have floated are faster).

Further, the present invention is not limited to differential limiting force control, but can also be used as a warning value to warn the driver that the driving time is inappropriate for applying differential limiting force.

(Effects of the Invention) As explained above, the differential eye power control iI of the present invention
In the 'Il device, the differential limiting force control means outputs a signal to reduce the differential limiting force if the drive slit amount of the drive wheels exceeds a reference value when driving with differential limiting force applied. In addition to outputting the reference value, the reference value is set to a large value when the vehicle speed or turning radius is small, and is set to a small value when the vehicle speed or turning radius is large, so it can be used when driving at low speeds such as when driving on mountain roads. When driving with a small turning radius, such as when driving at high speeds or racing, it is possible to prevent the drive wheels from spinning while improving verbal ability when calling by pressing the accelerator, and when driving at high speeds such as on a highway or when driving with a large turning radius. In some cases, the reduction in the tire cornering force of the driving outer wheels can be suppressed to a low level and the vehicle behavior can be stabilized, resulting in the effect that optimum driving performance can be obtained regardless of the vehicle speed or the size of the turning radius.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a claim showing a differential eye power control device of the present invention, FIG. 2 is an overall view showing a rear wheel drive vehicle to which the differential eye power control device of the embodiment is applied, and FIG. 3 is an implementation diagram. A flowchart showing the flow of the differential limiting control operation in the example controller, FIG. 4 is a differential limiting command value map for lateral acceleration,
Fig. 5 is a map of differential side visual acuity reduction value for vehicle speed, driving wheel slip speed, and lateral acceleration; Fig. 6 is a map of differential limiting force reduction value for turning radius, driving wheel slip speed, and lateral acceleration;
FIG. 7 is a differential limiting force reduction value map with curved boundaries. 1...Differential limiting clutch 2.3...Drive wheel 4...Differential limiting force control means 5...Drive slip amount detection means 6...Vehicle speed detection means 7...Turning radius detection means

Claims (1)

[Scope of Claims] 1) In a vehicle equipped with differential limiting force control means capable of variably controlling the differential limiting force between left and right drive wheels by controlling the engagement force of a differential limiting clutch, the drive slip of the drive wheels is provided. at least one of a drive slip amount detection means for detecting a drive slip amount, a vehicle speed detection means for detecting a vehicle speed of the vehicle, and a turning radius detection means for detecting a turning radius; When driving with force applied, if the drive slip amount of the drive wheels exceeds a reference value, a signal is output to reduce the differential limiting force, and the reference value is set to a large value when the vehicle speed or turning radius is small. Set to
A differential limiting force control device characterized by being a means for setting a small value when the vehicle speed or turning radius is large. 2) The differential limiting force control device according to claim 1, wherein the differential limiting force control means is a unit that increases the reference value as the lateral acceleration increases.