JPH06107014A - Controller for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To reduce rattling noise during conversion from engine drive to engine driven or during reverse conversion by constructing a device so as to increase an engaging force during an engine low load so as to maintain a high engaging force even after the engine load is increased. CONSTITUTION:A controller 100 takes in such signals as vehicle speed, throttle opening, steering angle, yaw rate, front and rear wheels rotational frequency, and the like from each kinds of sensors 101, 102,.... In the controller 100, when the difference between a rotation speed of the front wheels and that of the rear wheels is less than the predetermined value, it is determined that any different diameter tire is not mounted, and only in this case, an engaging force for a center differential clutch 90 is controlled so as to be increased when a load of an engine 10 is low. During the predetermined duration, the high engaging force for the center differential clutch 90 is maintained even after the load of the engine 10 is increased to a high load from a low load. Therefore, when an accelerator is stepped on a low mu road, the stability is increased, while the rattling noise, which is caused when the engine 10 is converted from drive condition to driven condition or converted reversely, is reduced effectively.

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 a four-wheel drive vehicle.

[0002]

2. Description of the Related Art Conventionally, a frictional engagement means is provided in a torque transmission path for transmitting a torque from an engine to each of the front and rear wheels, and the engagement force of the frictional engagement means is changed to allow differential front and rear wheels. A four-wheel drive vehicle whose state can be controlled has been proposed (for example, JP-A-61-4403).
1).

Further, in such a four-wheel drive vehicle, when the throttle opening (engine load) becomes equal to or less than a preset opening, the engaging force of the friction engaging means is increased to, for example, a part-time type. In a four-wheel drive vehicle, switching from two-wheel drive to four-wheel drive, and in a full-time four-wheel drive vehicle, switching to direct-coupling four-wheel drive, the differential between the front and rear wheels is controlled in a more restricted direction. The technology described above has also been proposed (for example, Japanese Patent Laid-Open No. 63-61635).

As described above, when the throttle opening is low (when the engine load is low), the engaging force of the friction engaging means is increased to directly connect the drive systems of the front and rear wheels, thereby driving and driving. It is said that rattling noise of the drive system due to switching of can be reduced.

[0005]

However, in the prior art, the tire diameter difference between the front and rear wheels is not particularly taken into consideration, and therefore, it is considered that the diameter of the mounted tire, especially the effective radius of the mounted tire is different between the front and rear wheels. However, it was designed to control the direct connection side without considering it. However, even if the effective radii of the mounted tires are different between the front and rear wheels, if the control to the direct connection side is performed as it is, the following problems may occur.

1) Internal circulation torque acts on the drive system, resulting in poor exercise performance.

2) In some cases, the internal circulation torque acts on the drive system, and a force larger than the original transmission torque acts on each member of the drive system, which lowers the durability of each member and increases the amount of heat generation. .

3) Despite the fact that the hydraulic pressure for direct connection to the friction engagement means is acting, relative rotation of the friction plate occurs, so that the durability of the friction engagement means deteriorates.

The present invention has been made in order to solve the above-mentioned conventional problems, and has a favorable rattling noise and rattling shock when the drive system is switched between the driving state and the driven state. It is an object of the present invention to provide a control device for a four-wheel drive vehicle, which is capable of effectively reducing the above-mentioned new problems due to the execution of the control. .

[0010]

As shown in FIG. 1, the present invention is provided with friction engagement means in the torque transmission paths for transmitting torque from an engine to front and rear wheels, respectively. In a four-wheel drive vehicle control device capable of controlling the differential allowable state of the front and rear wheels by changing the engagement force of the coupling means, means for detecting an engine load,
When the engine load is low, the engagement force of the friction engagement means is increased, and even after the engine load is increased from the low load to the high load, the engagement force of the friction engagement means is increased for a predetermined period. By providing an engaging force control means, a means for detecting the mounting of the different diameter tire, and a means for inhibiting the increase control of the engaging force by the engaging force control means when the mounting of the different diameter tire is detected, It is a solution to the problem.

[0011]

When the engine load becomes low, the technical idea of reducing rattling noise and rattling shock at the time of switching between driving and driven by increasing the engaging force of the frictional engaging means. Is basically the above-mentioned JP-A-63-61.
Although it is similar to the technical idea disclosed in No. 635, in the present invention, this high engaging force state is maintained for a predetermined period even after the engine load is increased.

Therefore, for example, the stability and power performance of the vehicle can be maintained high when the accelerator is suddenly depressed from the fully closed state on a low μ road or the like, and at this time ( The rattling noise and the like (when switching from driven to driving) can be absorbed well.

Further, in the present invention, the tire diameter difference between the front and rear wheels is detected, and when it is detected that there is a tire diameter difference between the front and rear wheels, this control is prohibited. as a result,
The internal circulation torque acts on the drive system to deteriorate the motion performance, or a force exceeding the original transmission torque acts on each member of the drive system to reduce their durability and generate a large amount of heat. It will be possible to prevent it.

Further, if the friction engagement means is directly connected in a state where there is a difference in tire diameter, relative rotation will occur despite the hydraulic pressure for direct connection being applied. Therefore, the durability of the friction plate is reduced, but such a situation can be prevented.

In the present invention, the "tire diameter" means the effective radius of the tire. Therefore, this tire diameter is the case when the tire with the same diameter is installed in addition to the case where the tire itself being installed has changed, such as when using a tempered tire or installing a chain. However, due to changes in the number of passengers, loading heavy items in the rear trunk, or changes in the loads acting on the front and rear wheels, such as when the vehicle is traveling on a steep slope, Even when the effective radius changes, the tires having different diameters are substantially mounted.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 is a skeleton diagram showing an embodiment of a four-wheel drive system for a vehicle to which the present invention is applied.

In the drawing, reference numeral 10 is an engine, 20 is an automatic transmission, 30 is a planetary gear type center differential device, 40 is a rear propeller shaft, 50 is a chain, 60 is a front propeller shaft, 70 is a front differential, and 80 is a front differential. Front drive shaft,
90 is a center differential clutch (friction engagement means), 1
00 is a control device (computer).

The engine 10 is installed vertically at the front of the vehicle. The output of the engine 10 is transmitted to the automatic transmission 20.

The automatic transmission 20 is provided with a fluid torque converter 21 and an auxiliary transmission unit 22, and has a well-known structure for automatically switching between four forward gears and one reverse gear by a hydraulic control device (not shown). ing. Of the four forward speeds, the highest speed (fourth speed) is the overdrive speed. The power that has passed through the automatic transmission 20 is transmitted to the center differential device 30 via the output gear 24.

The center differential device 30 includes a sun gear 31, a planetary pinion 32 that meshes with the sun gear 31, a carrier 33 that rotatably supports the planetary pinion 32 around the sun gear 31, and a ring gear 34 that meshes with the planetary pinion 32. Have.

The power transmitted to the output gear 24 of the automatic transmission 20 is transferred to the center differential device 3.
0 carrier 33, part of which is ring gear 34
Is transmitted to the rear propeller shaft 40 via the sun gear 31, and a part of the sun gear 31 is transmitted to the chain 50.

The power transmitted to the rear propeller shaft 40 side is transmitted to the left and right rear wheels via a rear differential and a rear drive shaft (not shown). On the other hand, the power transmitted to the chain 50 side is transmitted to the left and right front wheels (not shown) via the front propeller shaft 60, the front differential 70, and the front drive shaft 80.

The center differential clutch 90 connects the carrier 33 of the center differential device 30 and the sun gear 31 in a torque transmitting relationship. The center differential clutch 90 has a wet multi-plate clutch, and is well known in itself. That is, the solenoid (not shown) is driven at a predetermined duty ratio in response to a command from the control device 100, and the clutch pressure Pga of the center differential clutch 90 is controlled to an arbitrary value by using the hydraulic pressure generated thereby as a pilot pressure. The engagement force is generated according to the clutch pressure Pga.

When the carrier 33 of the center differential device 30 and the sun gear 31 are connected in a torque transmitting relationship by the center differential clutch 90, the center differential device 30 comes to integrally rotate as a whole.
The differential between the two is limited, and power is transmitted to the front side and the rear side at a torque distribution ratio according to the load distribution ratio. On the other hand, when the carrier 33 and the sun gear 31 are rotatably connected to each other, torque distribution according to the tooth ratio (radius ratio) of the ring gear 34 and the sun gear 31 is performed on the front side and the rear side.

In this embodiment, a center differential device having a planetary gear structure is adopted, and the carrier and the sun gear can be differentially limited by a center differential clutch, so that the torque distribution ratio to the front and rear wheels can be positively increased. Although the mechanism can be changed, the present invention is applied. 4
The wheel drive vehicle does not have to be of a type in which the torque distribution ratio is positively changed in this way. For example, a center differential device basically distributes front: rear = 5: 5, and a center differential clutch is used. A so-called diff lock (rigid connection) type is also applicable. Further, by not controlling the engagement force of the center differential clutch without having a center differential device, an arbitrary driving state (differential state) between the two wheels and four wheels can be set in multi-steps or stepless (non-steps). The present invention can be applied to a four-wheel drive vehicle that is continuously obtained.
Further, it is also applicable to a so-called part-time type four-wheel drive vehicle, which has only two stages of pure two-wheel and directly-connected four-wheel.

Returning to FIG. 2, the control device 100 takes in various signals indicating the traveling state via various sensors 101, 102, 103, ... Based on these signals, the engine 10 and the automatic transmission 20. And the clutch hydraulic pressure Pga of the center differential clutch 90 are controlled depending on the fluctuation state of the engine load.

The signals taken in are vehicle speed V, throttle opening θ, steering angle δ, yaw rate γ, lateral acceleration (lateral G),
Longitudinal acceleration (longitudinal G), front wheel speed Nf, rear wheel speed N
r, idle contact signal Idl, etc. are included.

First, FIG. 3 shows a flowchart for determining whether or not a tire having a different diameter is mounted.

In step 202, the vehicle speed V, the yaw rate γ, the oil pressure Pcd of the center differential clutch 90, the throttle opening θ, the rotational speeds Nf and Nr of the front and rear wheels, the shift position and the like are read. The oil pressure Pcd of the center differential clutch 90
Can obtain the data directly in the control device 100.

Next, at step 204, the running state of the vehicle is judged. That is, the vehicle speed V is not less than the lower limit vehicle speed V1 and not more than the upper limit vehicle speed V2, the absolute value of the yaw rate γ is not more than a predetermined reference value γ1, and the engagement hydraulic pressure Pcd of the center differential clutch 90 is a predetermined reference value. It is determined whether or not all the conditions of being equal to or less than the hydraulic pressure Po and being equal to or less than the reference opening degree θi set for each shift speed are satisfied.

The reason why the vehicle speed V is set within the above vehicle speed range is to avoid the influence of relatively large noise of the wheel speed in the low speed region and the high speed region. Further, the reason why the yaw rate γ is judged to be equal to or less than the reference value γ1 is to avoid the influence of the inner ring difference between the front and rear wheels. Further, the reference oil pressure Po is a predetermined oil pressure close to 0, and the engagement oil pressure Pcd.
Is to be confirmed to be below the reference oil pressure Po in order to avoid the influence of the differential limitation.
And, the judgment about the throttle opening θ is
This is because the wheels will slip if the driving force is large, and the limit of the driving force differs depending on the shift speed. Therefore, the reference opening θi is set for each shift speed.

When all of the above conditions are satisfied, that is, when the results of the determination in step 204 are all YES, the vehicle is in a state in which the differential between the front and rear wheels is free, and the vehicle is on a substantially straight line at a medium vehicle speed and the engine is Since it can be determined that the vehicle is traveling in a stable state in which the driving force from the vehicle is hardly received, the routine proceeds to step 206, where the ratio of the effective radii of the front and rear wheels, that is, the different diameter ratio K is calculated. The different diameter ratio K is obtained as a ratio (Nr / Nf) of the front wheel rotational speed Nf and the rear wheel rotational speed Nr, and is calculated every time the condition of step 204 is satisfied.

Next, a guard for removing noise is applied to the obtained different diameter ratio K. That is, it is determined whether the different diameter ratio K is lower than the lower limit A (step 208) or higher than the upper limit B (step 210). If the different diameter ratio K is smaller than the lower limit value A, the lower limit value A is adopted as the value of the different diameter ratio K (step 212). Conversely, if the different diameter ratio K exceeds the upper limit value B, the upper limit thereof is set. The value B is adopted as the value of the different diameter ratio K (step 214).

Following the above steps 208 to 214, in step 216, noise is removed by a filter. Here, if the different diameter ratio obtained in step 206 is Ko and the different diameter ratio obtained one cycle before the cycle in which the judgment is made is Kn-1,

## EQU1 ## Noise is removed by the calculation of Kn = (15.times.Kn-1 + Ko) / 16 (1).

Next, in order to judge the magnitude of the deviation of the front and rear wheels, in other words, the magnitude of the deviation of the number of revolutions, when there is no difference between the value Kn obtained in step 216 and the front and rear wheels. The absolute value .DELTA.Kn of the difference from the value "1" which is the value of is obtained (step 218).

This absolute value (hereinafter referred to as different diameter width) Δ
Kn has a difference in the effective radius of tires when tires of different sizes are attached to the front wheels and the rear wheels, chains are attached to either one of them, or extremely heavy luggage is accommodated in the trunk. In some cases, it will be greater than the predetermined value. Therefore, when the different diameter width ΔKn is equal to or less than the predetermined value C in the traveling state satisfying the condition of step 204, it can be determined that there is no difference in diameter between the front and rear wheels. Therefore, in step 220, it is judged whether or not the different diameter width ΔKn is less than or equal to a predetermined value C, that is, whether or not it is within a range having a width of C,
If the result is found to be C or less, the different diameter difference flag KF is reset to 0 (step 222).

On the other hand, if the different diameter width ΔKn is larger than the predetermined value C, the different diameter difference flag KF = 1 is set because the different diameter tire is mounted (step 224).

As a result of each judgment in step 204, when it is found that even one of them is not satisfied, the routine proceeds to step 226, where the value Kn obtained in the previous cycle as the different diameter ratio K is obtained. -1 is adopted, and then the process proceeds to step 220. Note that when this routine first starts, the initial value of the different diameter ratio K is set to 1.

Considering the mounting information of the different-diameter tires thus obtained, the control device 100 follows the flowchart shown in FIG. 4 and follows the flowchart of FIG. To execute.

This control flow is shown in FIG.

First, in step 300, various signals are captured.

In step 301, it is judged whether or not the three conditions of V3≤V≤V4│δ│≤δoKF = 0 are satisfied.

The rattling prevention control according to the present invention is based on this 3
It is executed only when all the conditions are met. The purpose of the vehicle speed V being between the predetermined values V3 and V4 is that if the vehicle speed V is too high, the adverse effect of limiting the differential will occur, and the vehicle speed V will be too low. This is because there is no point in executing this control because it enters the drive region (even when the accelerator pedal is released) and there is a high possibility that separate differential control is performed in this region.

Further, the absolute value of the steering angle δ is smaller than the predetermined value δo, because the tight braking phenomenon occurs unless the differential between the front and rear wheels is allowed when the steering angle δ is large. Is.

The condition that the different diameter difference flag KF is 0 is as already described in detail, and if the differential is limited under the condition that the different diameter tires are mounted, the internal circulation torque This is because various problems may occur depending on the occurrence and the like.

When all of the three conditions in step 301 are satisfied, the flow proceeds to 302 and the throttle opening θ
And the opening / closing speed Δθ thereof are determined.
This determination is because it is necessary to promptly raise the engaging force of the center differential clutch 90 when the throttle is returned quickly and the opening is low.

That is, when it is determined that the throttle opening θ is smaller than the predetermined value θ1 and the closing speed Δθ of the throttle opening θ is smaller than the predetermined value −θ2, step 3
After proceeding to 03, the flag Fg indicating that this control is being executed is set to 1, and in step 304 the clutch pressure Pga of the center differential clutch 90 is suddenly increased to the maximum pressure Pga max.
And the engaging force is rapidly increased.

On the other hand, when it is determined that at least one of θ <θ1 and Δθ <−θ2 is not established, the routine proceeds to step 305, where it is determined whether or not the idle contact signal Idl is on, that is, the accelerator pedal is fully released. It is determined whether or not it is closed.

If it is determined that the idle contact is on, then the routine proceeds to step 306, where the flag Fg indicating that this control is being executed is set to 1, and step 307
Thus, the clutch pressure Pga is gently increased by Pga1.

In step 308, it is determined whether or not the clutch pressure Pga has reached the maximum value Pga max as a result, and when it reaches the maximum value, the routine proceeds to step 309, where the maximum value Pga is reached.
ga max is maintained.

On the other hand, if NO in step 301, and if it is determined in step 305 that the idle contact signal Idl is off, step 31
Control for reducing the clutch pressure Pga after 0 is started.

First, at step 310, it is judged if the flag Fg is 1. If it is determined to be 1, it means that the control for increasing the clutch pressure Pga has been executed up to that point, and therefore the routine proceeds to step 311, and the clutch pressure Pga is reduced by a predetermined value Pga2 (gradually). Is done.

Further, in step 312, the clutch pressure Pga is consequently 0 (or a predetermined value determined for another purpose).
It is determined whether or not the flag Fg has been reached, and when it is determined that the flag has reached 0, the process proceeds to step 313, and the flag Fg is set to 0.

On the other hand, when it is determined in step 310 that the flag Fg is not 1, it is recognized that this control has not been executed until then, so the routine proceeds to step 314, where the clutch pressure Pga is maintained at 0. It is like this.

According to this control flow, when the accelerator pedal is rapidly released to a low opening degree, the engaging force of the center differential clutch 90 is rapidly increased, so that rattling noise is prevented from occurring and The stability of the vehicle can be ensured, and on the other hand, when the accelerator pedal is fully closed slowly, the engagement force of the center differential clutch 90 is slowly increased, so that there is no sudden change in the torque distribution ratio and the driver does not have to change rapidly. It is possible to prevent the rattling sound from being generated without giving a feeling of strangeness.

That is, for example, when the engine load suddenly decreases, the behavior of the vehicle also suddenly changes originally. Therefore, rather, the rattling noise of the drive system is more surely raised by rapidly increasing the engaging force of the frictional engaging means. It is possible to reduce it to a lower level and it is preferable in terms of operating performance. Further, since the driver can predict to some extent that the behavior of the vehicle changes when the accelerator pedal is suddenly operated, the driver does not feel a sense of discomfort.

On the other hand, for example, when the engine load is gently reduced, there is a margin until the normal rattling noise is generated, and even if it is generated, the noise is small, so that the frictional engagement means operates. It is preferable that the engagement force is gradually increased because the torque distribution ratio does not suddenly change more than necessary and the driver does not feel uncomfortable.

Further, in this embodiment, the increase of the engaging force is
The idle contact signal Idl is maintained until it is turned off, and is slowly lowered after the detection, so that the engagement force is maintained high for a predetermined period immediately after the accelerator pedal is depressed. As a result, it is possible to effectively prevent rattling noise when the driven state is reversed to the driven state. For example, stable acceleration such as sudden start from the state where the accelerator is fully closed. It will also be possible to greatly improve the sex.

[0060]

As described above, according to the present invention, it is first confirmed that a tire having a different diameter is not mounted,
When the engine has a low load, the engagement force of the friction engagement means is always increased, and since the high engagement force is maintained for a while even after the engine load increases, especially when the accelerator is depressed on a low μ road or the like. The stability of the engine can be increased, and rattling noise when the engine is switched from driving to driven or from driven to driving can be effectively reduced without making the driver feel uncomfortable. The excellent effect of becoming

Further, when it is detected that the tires of different diameters are mounted, their control is prohibited, so that the internal circulation torque acts on the drive system to impair the exercise performance, or It is possible to prevent the occurrence of problems such as a decrease in the durability of each member or an abnormal increase in the amount of heat generated due to a force greater than the transmission torque. Further, despite the fact that the hydraulic pressure in the direct coupling direction acts on the friction engagement means, relative rotation of the friction plate occurs,
The problem that the durability of the friction plate is lowered can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the gist of the present invention.

FIG. 2 is a skeleton diagram showing a configuration of a vehicle four-wheel drive vehicle to which the present invention is applied.

FIG. 3 is a flowchart showing a control flow for detecting a mounting state of a tire having a different diameter, which is executed in the apparatus of the embodiment.

FIG. 4 is a flowchart showing engagement force increase control executed in the apparatus of the above embodiment.

[Explanation of symbols]

 10 ... Engine 20 ... Automatic Transmission 30 ... Center Differential Device 40 ... Rear Propeller Shaft 50 ... Chain 60 ... Front Propeller Shaft 70 ... Front Differential 80 ... Front Drive Shaft 90 ... Center Differential Clutch 100 ... Control Device

Claims (1)

[Claims] 1. A friction engagement means is provided in a torque transmission path for transmitting torque from an engine to each of the front and rear wheels, and an engagement force of the friction engagement means is changed so that a differential allowable state of the front and rear wheels is changed. In a control device for a four-wheel drive vehicle that is controllable, when the engine load is low and the engine load is low, the engaging force of the friction engagement means is increased and the engine load is increased from low load to high load. Even after the load is increased, the engagement force control means for increasing the engagement force of the friction engagement means for a predetermined period, the means for detecting the attachment of the different diameter tires, and the attachment of the different diameter tires are detected. A control device for a four-wheel drive vehicle, comprising: means for prohibiting an increase control of the engagement force by the resultant force control means.