JPH09193685A - Lsd controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform control without any hunting by finding a differential rotation difference from a difference between a rotation difference between left and right driving wheels based on the detection value from a rotational speed sensor and a rotation difference between the left and the right driving wheels based on the detection value from a yaw rate sensor and deciding a connecting force for a clutch. SOLUTION: A driving force from an engine 1 is distributed by means of a differential mechanism 4, and a differential in the differential mechanism 4 is controlled with the differential mechanism 4 in compliance with a connecting force for a clutch 7. An oil pressure is fed to the clutch 7 from an oil pressure generating device 9, and a control signal for increasing/reducing the oil pressure is outputted from a controller 10. In this case, signals from a rotational speed sensor 11 and a yaw rate sensor 12 are inputted to the controller 10. From a difference between a rotation difference between driving wheels 6, 6 based on the detection value from the rotational speed sensor 11 and a rotation difference between the driving wheels 6, 6 base on the detection value from the yaw rate sensor 12, a differential rotational difference is found, and from its integration value and the differential rotational difference, a connecting force for the clutch 7 is decided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the differential limiting force of an LSD (limited slip differential).

[0002]

2. Description of the Related Art In general, an LSD distributes and transmits a driving force from an engine to left and right driving wheels, and when a differential occurs due to a slip in the driving wheels, the differential is limited to allow the driving wheels to idle. And attempts to reliably transmit the driving force to the road surface. In recent years, there is an LSD which has a friction multi-plate clutch inside and can control a differential limiting force by controlling a fastening force of the clutch. In this case, the clutch engagement force is electronically controlled according to the running state of the vehicle, and conventionally, the clutch engagement force is controlled based on the rotation difference between the left and right drive wheels (Japanese Patent Laid-Open No. 4-5128, etc.). ),
For example, there is one that controls the clutch engagement force based on the lateral G and the accelerator opening (Japanese Patent Laid-Open No. 4-5131).

[0003]

In the former case, when the frictional force between the tire and the road surface is different between the left and right wheels, the driving force escapes to the driving wheel with the lower frictional force, causing slipping and idling. Is to prevent. This is particularly effective for securing the driving force to the inner wheels during turning, and for starting the vehicle on the split μ road.

In this case, the clutch engagement force control method detects the rotational difference between the left and right drive wheels and determines from the detected value that the driving force has escaped, and according to the rotational difference (for example, proportionally). Then, the clutch engaging force and the differential limiting force are increased.

However, this control method has the following problems. When the rotation difference occurs, the clutch engagement force increases and the rotation difference becomes zero. However, when this occurs, the clutch engagement force becomes zero and the rotation difference occurs again. Then, the clutch engaging force is increased again, and as a result, this process is repeated and hunting occurs. This problem remarkably occurs especially on low μ roads and the like.

In the latter case, this problem does not occur, but if this is done, control is carried out independently of the rotational difference of the drive wheels, so differential rotation due to the rotational difference between the inner and outer wheels will occur during steady turning, The vehicle tends to understeer or the inner wheels of the vehicle are dragged.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an LSD having a clutch for limiting the differential between the left and right drive wheels, and a controller for controlling the engagement force of the clutch. A first sensor for detecting the rotational speeds of the left and right driving wheels, a second sensor for detecting the yaw rate of the vehicle, and an actual rotation difference between the left and right driving wheels based on the detection values of the first sensor. In addition to the calculation, the rotation difference between the left and right drive wheels based on the turning of the vehicle is calculated based on the detected value of the second sensor, and the differential rotation difference based on slip or the like is calculated from the difference between these rotation differences. The difference is integrated to obtain the integrated value,
And a controller that determines the engagement force of the clutch based on the differential rotation difference and the integral value.

In this case, the differential rotation difference is the difference between the actual rotation difference of the left and right drive wheels and the theoretical rotation difference based on turning. Therefore, the differential limitation corresponding to the rotation difference between the inner and outer wheels during turning is not performed, but only the rotation difference due to slip is limited.

Particularly, since the integral value of the differential rotation difference is added as a correction term, even if the clutch engaging force is increased or decreased, the integral value still remains and the clutch engaging force does not become zero. Since the integrated value cumulatively increases, the clutch engaging force gradually converges to a desired value by repeatedly increasing and decreasing the clutch engaging force. As a result, the problem of hunting is solved and the driving force can be reliably transmitted to the road surface even on a low μ road.

[0010]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 2 shows a vehicle equipped with an LSD control device according to the present invention, and the direction of the arrow indicates the front of the vehicle. In this vehicle, the driving force generated by the engine 1 is transmitted to the differential mechanism 4 via the transmission 2 and the propeller shaft 3, and the driving force is distributed to the left and right drive shafts 5 in the differential mechanism 4. The left and right drive wheels 6 are driven. Here, the vehicle is an FR vehicle that has the engine 1 in the front and uses rear wheels as drive wheels 6.

The differential mechanism (differential) 4 has a general structure having a plurality of differential gears in a differential case, and distributes and transmits the driving force to the left and right drive shafts 5, while at the same time, Allows free differential or relative rotation. The differential of the differential mechanism 4 is appropriately limited according to the engaging force of the clutch 7. The clutch 7 is a friction multi-plate clutch in which a fastening force is controlled by receiving a hydraulic pressure. A combination of the differential mechanism 4 and the clutch 7 is an LSD (limited slip differential) 8.
The LSD 8 has the same structure as in Japanese Patent Laid-Open No. 4-5128 and is illustrated separately in the figure, but the clutch 7 and the differential mechanism 4 are integrated and housed in the same housing.

To control the engagement force of the clutch 7, a hydraulic pressure is supplied to the clutch 7 from a hydraulic pressure generator 9. The controller 10 outputs a control signal for increasing or decreasing the hydraulic pressure. The controller 10 is an electronic control unit that inputs signals from various sensors, performs predetermined calculations, and outputs control signals to the hydraulic pressure generator 9. Here, the controller 10 is an ECU and simultaneously executes fuel injection control of the engine 1 and the like. As the sensor, a rotation speed sensor 11 (first sensor) provided on each drive wheel 6 for detecting a rotation speed, and a yaw rate sensor 12 for detecting a yaw rate of the vehicle during traveling are used.
A (second sensor) and a lateral G sensor 13 (third sensor) for detecting a lateral G (lateral acceleration) of the vehicle are provided.

FIG. 1 is a flowchart of control executed by the controller 10.

First, after the memory is initialized in step 101, detection signals are input from the rotation speed sensor 11, the yaw rate sensor 12, and the lateral G sensor 13 in step 102. Referring also to the schematic diagram of FIG. 3, the rotation speed sensor 11
From the detection signal of, the rotation speeds NL, NR (m /
s) is read. Further, the yaw rate Δφ (rad / s, left rotation is positive) of the vehicle is read from the detection signal of the yaw rate sensor 12, and the lateral GYg (m / s ² , left direction of the vehicle is detected from the detection signal of the lateral G sensor 13. (Correct) is read.

Next, at step 103, the actual rotational difference between the left and right drive wheels 6 is calculated using NL and NR. This rotation difference is expressed by the following equation.

ΔN = NL-NR (1) Then, in step 104, a theoretical rotation difference based on the turning of the vehicle is calculated. This rotation difference is expressed by the following equation. Note that l (m) is the distance between the drive wheels 6.

ΔNc = 2πlΔφ (2) Here, when the vehicle turns, a difference in rotation occurs between the left and right drive wheels 6 due to the difference in the running loci. In such a device, the difference in rotation is indirectly calculated from the yaw rate Δφ. I am trying.

Thereafter, in step 105, ΔN and ΔNc
Is calculated by the following equation.

E = ΔNc-ΔN (3) This e is a differential rotation difference caused by a slip occurring on the inner wheel during turning and on the driving wheels on the low μ road side due to the start of the split μ road, etc., and the engagement of the clutch 7 It is a basic value for force control.

Particularly in this apparatus, in the next step 106,
The integral value integral (k) of the differential rotation difference e is calculated by the following equation.

Integral (k) = integral (k-1) + eτ (4) Here, τ is the control sampling time, and k and k-1 are the current and previous control. By adding eτ to the previous integral value, the present integral value is obtained, and the integral value is cumulatively increased with time.

This integrated value in
tegral (k) is effective in preventing hunting in controlling the clutch engagement force.

Next, at step 107, the turning direction dir (k) of the vehicle is determined from the value of Yg as follows (see FIG. 4). Note that Ygl and Ygr are threshold values.

If Ygl>Yg> Ygr, then dir (k)
= N (straight ahead) If Ygr> Yg, dir (k) = L (turn left) If Yg> Ygl, dir (k) = R (turn right) Then, in step 108, these dir (k) Based on the sign, the target engagement force T of the clutch 7 is calculated by the following equation.

If dir (k) = N, T = | gn1e + gn2 integral (k) | ... (5) If dir (k) = L, T = max (0, gl1e + gl2 integral (k)) ... ( 6) If dir (k) = R, T = max (0, -gr1 e-gr2 integral (k)) (7) gn1, gn2, gl1, gl2, gr1, and gr2 are gains set by the vehicle. And is a constant. The display of max (x, y) means that the larger value of x or y is adopted. When the target engagement force T is calculated, a control signal corresponding to the target engagement force T is sent to the hydraulic pressure generation device 9 to obtain a clutch engagement force corresponding to the target engagement force T, and to execute the differential limiting control of the LSD 8. Can be.

However, although the reason will be described later, in this apparatus, after this, in step 109, the initialization of the integrated value is determined. That is, if dir (k) = dir (k-1), the process returns to step 102 and follows the control flow described above, but if dir (k) ≠ dir (k-1), the process proceeds to step 110, and the integrated value Reset integral (k) to initial value 0. After this, the process returns to step 102 and the above control is repeated.

The clutch engaging force is controlled in this way, and FIG. 5 is a graph showing the state of the control.

In the figure, the horizontal axis represents time t, and the vertical axis represents the target fastening force T (corresponding to the actual fastening force). Especially T ₀
Is the value of the target fastening force T that matches the current running state of the vehicle.

As shown in the figure, the target fastening force (hereinafter simply referred to as fastening force) T repeatedly increases and decreases at every sampling time τ. That is, even if a rotation difference occurs in the drive wheels 6, T = T ₀
As a result, there is no difference in rotation, slippage or idling of one drive wheel 6 is prevented, and both drive wheels 6 rotate at appropriate equal rotational speeds. Then, the above-described differential rotation difference e becomes zero. Then, the first term multiplied by e in equations (5) to (7) becomes 0, and the value of T becomes integral.
As a result of the reduction of the fastening force by reducing the value of only the second term (the value on the alternate long and short dash line) multiplied by (k) to reduce the engaging force, the drive wheel 6 becomes differential. In addition, the increase / decrease of the fastening force is repeated.

However, here, the differential rotation difference e is 0.
However, since the second term is an addition term and remains, the fastening force T does not become zero. Since the second term is an integral term, the second term cumulatively increases with time, gradually approaches T _{0 as} shown by a dashed line, and instead, the increase / decrease width of the first term decreases with time, and T It gradually increases and decreases near ₀ .

Conventionally, since there is no additional term based on the integral value integral (k), the fastening force T becomes completely 0 when it is reduced, and there is a problem of hunting in which the fastening force T increases or decreases in a large width. there were. In this device, the fastening force is determined based on the differential rotation difference e and the integral value integral (k), and the integral value integral
Since the value by gral (k) is added as an additional term, the fastening force T converges (closes) to the desired fastening force T ₀ with time.
Therefore, hunting can be prevented by minimizing the range of increase or decrease in the fastening force T. As a result, even on a low μ road such as a snow road, the driving force can be reliably transmitted to the road surface by both drive wheels 6, and the steering stability can be greatly improved.

Since the sampling time τ is extremely short and the gains gn1 ... Can be set freely, the time required for the fastening force T to converge to the desired fastening force T ₀ is extremely short. There is no delay in limiting the differential.

By the way, in the present apparatus, as described above, the initialization judgment of the integral value integral (k) is performed in step 109,
If the sign of dir (k) has changed, the integrated value in step 110
Integral (k) is initialized or reset.

This is because the integrated values are accumulated over time and the value increases to the plus side or the minus side depending on the measurement error or the driving condition, and if this is not done, the value will become enormous. . In this way, if the integral value is initialized when the sign of dir (k) changes or when the turning direction changes, the integral value can be initialized at appropriate time intervals while the vehicle is running. It is possible to prevent the force T from becoming an excessive value on the plus side or the minus side. Here, the initial value is set to 0, but another relatively small value can be set.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and other embodiments can be adopted. In addition, the present invention is applicable to not only FR vehicles but also FF vehicles, 4WD vehicles and the like.

[0037]

The present invention exhibits the following excellent effects.

(1) Hunting can be prevented during clutch engagement force control, and steering stability can be improved.

(2) By initializing the integral value, it is possible to prevent the initial value of the clutch engaging force from becoming excessive.

[Brief description of the drawings]

FIG. 1 is a flowchart of control by a control device according to the present invention.

FIG. 2 is a configuration diagram showing a vehicle provided with a control device according to the present invention.

FIG. 3 is a schematic diagram for explaining each value.

FIG. 4 is a graph showing a relationship between Yg and dir (k).

FIG. 5 is a graph showing a state of control by a control device according to the present invention.

[Explanation of symbols]

 6 Drive Wheel 7 Clutch 8 LSD 10 Controller 11 Rotation Speed Sensor (First Sensor) 12 Yaw Rate Sensor (Second Sensor) NL, NR Drive Wheel Rotational Speed ΔN Actual Rotational Difference of Drive Wheel ΔNc Based on Vehicle Turning Rotational difference of drive wheel T Clutch engagement force e Differential rotational difference integral (k) Integral value Δφ Yaw rate

Claims (2)

[Claims] 1. An LSD having a clutch for limiting the differential between the left and right drive wheels, wherein the LSD is a control device for controlling the engagement force of the clutch. A first sensor for detecting the yaw rate of the vehicle, a second sensor for detecting the yaw rate of the vehicle, and an actual rotation difference between the left and right drive wheels based on a detection value of the first sensor. Calculate the rotation difference between the left and right drive wheels based on the turning of the vehicle based on the detected value of
A controller for determining a differential rotation difference based on a slip or the like, integrating the differential rotation difference to obtain an integrated value, and determining the engaging force of the clutch based on the differential rotation difference and the integrated value. LSD control device characterized by: 2. A third sensor for detecting a lateral G of the vehicle is further provided, wherein the controller determines a turning direction of the vehicle based on a detection value of the third sensor, and the turning direction is changed. The LSD control device according to claim 1, wherein the integral value is initialized at that time.