JPH0536251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a differential control device for a vehicle, specifically a device for differential operation that creates a rotation difference between inner and outer wheels or front and rear wheels when a vehicle turns, and a device that limits the differential. Regarding.

(Prior Art) In general, a vehicle is provided with a differential device that transmits engine power between the left and right or front and rear drive wheels while allowing differential movement in order to perform smooth turning motion.

However, when a wheel on one side gets stuck in the mud and spins, it is necessary to limit the differential operation in order to transmit stronger torque to the other wheels and make it easier to escape. Become.

Conventional differential control devices for this type of vehicle include:
For example, there are those described in JP-A-58-133920 and the one described in Japanese Patent Application No. 60-162267 (JP-A-62-20724), which was previously proposed by the present applicant.

In the former device, the locking device in the rear differential is turned on and off according to the difference in rotational speed between the left and right drive wheels.

On the other hand, the latter device controls the differential limiting amount in the rear differential according to the rotational speed difference between the front and rear wheels and/or the acceleration difference between the front and rear wheels.

(Problem to be Solved by the Invention) The former device restricts the differential of the drive wheels when the difference in left and right rotational speeds of the drive wheels is greater than a predetermined value, thereby creating a low friction coefficient road (hereinafter referred to as a low μ road). ), the aim is to avoid one-sided slips (idling).
Since the difference in rotational speed between the left and right drive wheels during high-speed straight running is much smaller than when driving on a low μ road, it is impossible to detect the state of drive slip during high-speed straight running. Therefore, this one has a low μ
Although it can be applied to prevent stuckness on roads (preventing one-wheel slip of the drive wheels), it cannot be applied to differential limiting control that is performed with the intention of improving the stability of high-speed straight running.

On the other hand, the latter device calculates the difference ΔN between the average rotational speed of the left and right driving wheels and the average rotational speed of the left and right driven wheels, and controls the differential limiting amount based on this difference ΔN. The difference ΔN can include both the amount of one-wheel slip on a low μ road and the amount of drive slip when traveling straight at high speed, and it is possible to achieve both of the above, but the difference ΔN is Since the rotational speeds of the left and right driving wheels and the left and right driven wheels are simply averaged, the amount of information about one-wheel slip and drive slip included in the difference ΔN is small, and therefore the sensitivity of slip detection is low. The drawback was that sufficient control accuracy and high responsiveness could not be obtained, and there was room for improvement.

(Object of the Invention) Therefore, the object of the present invention is to provide differential limiting control that is performed with the intention of preventing stuckness (preventing one-wheel slippage of the driving wheels) on low μ roads, and with the intention of improving the stability of high-speed straight running. The objective is to achieve compatibility with the differential limiting control that is performed, and to improve the accuracy and responsiveness of both of these controls.

(Means for Solving the Problems) Fig. 1 is a basic conceptual diagram of a vehicle differential control device according to the present invention, in which a shows a distribution of engine power to the drive wheels by allowing a differential between the left and right wheels. and power distributing means which generates a target differential resistance force and limits the amount of differential when differential restriction is commanded, b is a first speed detection means which detects the rotational speed of the driving wheels, and c is a first speed detection means of the driven wheels. A second speed detection means for detecting the rotational speed, and d is the rotational speed difference between the driving wheel and the driven wheel based on the average value of the left and right rotational speeds of the driven wheel and the higher value of the left and right rotational speeds of the driving wheel. e is a target value setting means for setting a target differential resistance force between the left and right drive wheels according to the rotational speed difference, and f is a means for causing the power distribution means to generate a target differential resistance force. This is a command means for commanding the restriction of the differential.

(Function) Single-wheel slip on a low-μ road appears as uneven rotation speeds of the left and right drive wheels, and the degree of slip is sensitively indicated by the higher value of the rotation speeds of the left and right drive wheels. It will be done. Therefore, by applying the above, highly responsive and highly accurate differential limiting control can be performed.

Furthermore, there is a proportional relationship between the amount of drive slip and the vehicle speed during high-speed straight running, and the vehicle speed can be accurately expressed by the average rotational speed of the driven wheels. Even when applied to the above, highly responsive and highly accurate differential limiting control can be performed.

(Example) Hereinafter, the present invention will be explained based on the drawings.

2 to 5 are diagrams showing an embodiment of the present invention. First, the configuration will be explained. In Figure 2, 1
1 is a final reduction gear (power distribution means) installed in the power transmission system between a transmission (not shown) and the left and right rear wheels that are drive wheels, and the final reduction gear 1 is an engine that is transmitted through the transmission. The differential mechanism 2 includes a differential mechanism 2 that distributes power to the left and right rear wheels while allowing differential movement, and a differential limiting means 3 that limits the differential movement in the differential mechanism 2.

The differential mechanism 2 receives power from the transmission with an input shaft 5 rotatably supported by a gear housing 4, and transmits the power to a differential case 7 via a driven gear 6. Drive shafts 10L and 10R are rotated through side gears 9 by rotating pinion mate shafts 8 provided in a direction substantially perpendicular to the rotational center axis of 7.
to drive. The drive shafts 10L and 10R are connected to the left and right rear wheels, and receive engine power to rotate the rear wheels.

On the other hand, the differential limiting means 3 has a multi-plate clutch 11 interposed between a differential case 7 and a side gear 9 arranged on the left and right sides of the pinion mate shaft 8 in the figure. 11 is fastened by the pressing force of a hydraulic piston 12 that moves in response to hydraulic pressure supplied from the outside, and connects the side gear 9 to the differential case 7 to limit differential movement. The differential limit amount is determined by the magnitude of the hydraulic pressure Pa supplied to the hydraulic piston 12, and this hydraulic pressure
Pa is the hydraulic pressure from the hydraulic source 13, which is the electromagnetic proportional pressure reducing valve 1.
4 and is supplied through the hydraulic passage 15.
These hydraulic power source 13, electromagnetic proportional pressure reducing valve 14, and hydraulic passage 15 constitute command means 16.

The electromagnetic proportional pressure reducing valve 14 regulates the hydraulic pressure Pa supplied to the hydraulic piston 12 based on the magnitude of the command current i output from the controller 20, and the controller 20 adjusts the command current according to the rotational speed difference between the front and rear wheels. Output i.

The key point of the present invention lies in the method of calculating this rotational speed difference, and this will be explained in detail using the block diagram of FIG.

The controller 20 has functions as a speed difference calculation means and a target value setting means, and as shown in FIG.
7. Consists of a function generation circuit 28 and a current generation circuit 29.

The F/V converters 21 and 22 receive signals from speed sensors 31 and 32 that detect the left and right rotational speeds of the front wheels, which are driven wheels, respectively, and the F/V converters 23 and 24 receive signals from the left and right rotational speeds of the front wheels, which are driven wheels. Signals from speed sensors 33 and 34 that detect the left and right rotational speeds of a certain rear wheel are input.

As an example, focusing on the speed sensor 31 that detects the left rotation speed N ₁ of the front wheel, this speed sensor 31 is arranged opposite to the speed detection gear 31a attached to the front wheel and the speed detection gear 31a. Rotation speed V ₁ due to magnetic action as the gear rotates
and an electromagnetic pickup 31b that generates an electromotive force having a frequency _f1 corresponding to the frequency f1.

F/V converters 21 to 24 are each speed sensor 3
Frequency signals f ₁ to _{f 4} from 1 to 34 are converted to voltage signals V ₁ to V ₄ , respectively, and those corresponding to the front wheels are outputted to the average value calculation circuit 25, and those corresponding to the rear wheels are outputted to the high select circuit 26. Output. The average value calculation circuit 25 calculates the average value (V _f ) _M of the signals V ₁ and V ₂ and outputs it to the difference value calculation circuit 27, and the high select circuit 26 selects the higher voltage value of the signals V ₃ and V ₄ . The difference value calculation circuit 27 selects the signal with (V _r ) _H .
Output to. The difference value calculation circuit 27 calculates the difference value ΔV according to the following equation and outputs it to the function generation circuit 28.

ΔV=(V _r ) _H − (V _f ) _M ...The function generating circuit 28 outputs a current command value i* having characteristics as shown in FIG. 4 for the difference value ΔV to the current generating circuit 29, The current generating circuit 29 outputs a command current i as an actual current to the electromagnetic proportional pressure reducing valve 14 based on the current command value i*. When the command current i is input to the electromagnetic proportional pressure reducing valve 14, the solenoid 1
4a is excited to generate a hydraulic pressure Pa having characteristics as shown in FIG. Note that 35 is a reservoir tank.

Next, the action will be explained.

Now, when a vehicle is traveling at high speed on a high μ road,
When one of the rear wheels, which is the driving wheel, generates a slight drive slip, the speed sensors 33 and 34 detect the rotational speed of the rear wheel, and the high select circuit 26 selects the higher value of these. A difference value calculation circuit 27 calculates a difference value ΔV from the front wheel average value.

That is, in a situation where one of the rear wheels that has slipped has a higher rotational speed, by using this as input information, unilateral slip of the rear wheel can be detected with higher accuracy than in the past. At this time, the magnitude of the command current i is set according to the magnitude of the difference value ΔV, in other words, the magnitude of the slip, and the hydraulic pressure Pa is supplied to the final reduction gear device 1. Therefore, the differential of the final reduction gear 1 is limited depending on the slip situation, and the rear wheels are prevented from spinning, allowing stable running.

On the other hand, the above-mentioned one-wheel slip condition can be detected accurately even on a high μ road, so that the differential limiting action can be performed with good responsiveness. Moreover, such an effect means that there is no need to supplement the information with other sensor information, which has been pointed out as a problem in the conventional method.

It should be noted that the differential control amount of the final reduction gear 1 depends on the difference value ΔV when it is positive, and becomes zero when it is negative (see FIG. 4). Instead of setting it to zero when it is negative, it may be set to an appropriate minimum value.

Furthermore, the present invention is not limited to the application of the mechanism shown in Fig. 2 to the power distribution means, but can be applied to all other structures as far as differentials and their limitations are concerned. It is. For example, the differential control may be performed electromagnetically or mechanically instead of hydraulically.

Furthermore, those with four-wheel drive (e.g. 4WD
Of course, it can also be applied to center differential clutches, etc.).

In this case, since both the front and rear wheels become driving wheels, the wheel speed difference calculation means for detecting the slip state of the wheels has two functions: one to detect one-wheel slip in the rear wheel, one to detect one-wheel slip in the front wheel. Calculation for detecting is performed at the same time.

In other words, by comparing the average value of the left and right rotational speeds of the front wheels with the higher value of the left and right rotational speeds of the rear wheels, it is possible to detect the slip condition of the rear wheels, and also to detect the left and right rotational speeds of the rear wheels. The slip state of the front wheels can be detected by comparing the average value with the higher value of the left and right rotational speeds of the front wheels. If it is detected through the above calculation that one of the front and rear wheels is slipping, the center differential, which is a differential limiting device, may be locked.

Note that the present invention is not limited to the wire logic circuit as in the above embodiment, but can also be implemented using, for example, specific software.

(Effect) According to the present invention, the rotational speed difference between the driving wheel and the driven wheel is calculated based on the average value of the left and right rotational speeds of the driven wheel and the higher value of the left and right rotational speeds of the driving wheel. However, since the differential amount is controlled according to this rotational speed difference, differential limiting control is performed with the intention of preventing stuckness on low μ roads (preventing one-wheel slippage of the drive wheel) and high-speed straight-ahead driving. It is possible to achieve compatibility with differential limiting control, which is performed with the intention of improving stability, and improve the control accuracy and responsiveness of both, thereby improving the vehicle's driving performance. .

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 5 are diagrams showing an embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, Fig. 3 is a block diagram of its main parts, and Fig. 3 is a diagram showing an embodiment of the present invention. Figure 4 shows the relationship between the difference value and the current command value.
FIG. 5 is a diagram showing the relationship between the command current and oil pressure. 1... Final reduction gear (power distribution means), 16...
Command means, 20...controller (speed difference calculation means, target value setting means), 31-32...speed sensor (speed detection means).

Claims (1)

[Claims] 1 Distributes the engine power to the drive wheels, driven wheels, and the drive wheels while allowing the differential between the left and right wheels, and when a command to limit the differential is issued, generates a target differential resistance force to increase the differential amount. a power distribution means for limiting, a first speed detection means for detecting the rotational speed of the driving wheel, and a second speed detection means for detecting the rotational speed of the driven wheel;
speed difference calculation means for calculating a rotational speed difference between a driving wheel and a driven wheel based on an average value of left and right rotational speeds of the driven wheel and a higher value of the left and right rotational speeds of the driving wheel; a target value setting means for setting a target differential resistance force between the left and right drive wheels according to the speed difference; a command means for instructing the power distribution means to limit the differential so as to generate a target differential resistance force; A vehicle differential control device characterized by comprising: