JP2009196522A - Control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce vibration by stick slip at a center differential. <P>SOLUTION: The ECU carries out a program including a step of detecting rotation speed of front wheels and rear wheels (S10), a step of detecting a steering angle of a steering wheel (S12), a step of detecting opening of an accelerator (S14), and a step of setting a rising ratio of engine output torque smaller when the rotation speed of the front wheels and the rear wheels is smaller than a first threshold value (S20: YES), with the steering angle of the steering wheel greater than a second threshold value (S22: YES), and the opening of the accelerator greater than a third threshold value (S24: YES)(S30). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle control device, and more particularly to a vehicle control device equipped with a center differential.

  Conventionally, in a four-wheel drive vehicle, the torque output from the engine is distributed to the front and rear wheels, and if a difference in rotation between the front and rear wheels occurs during turning, a center differential that absorbs the rotation difference has been installed. There is something. Some vehicles equipped with such a center differential have a differential restriction of the center differential by a clutch, and the torque distribution to the front and rear wheels is variable.

  Some planetary gear type center differentials limit differentials by the function of the center differential itself. For example, a center differential that employs torque-sensitive LSD (Limited Slip Differential) is a differential case, a differential carrier that meshes with the differential case, rotates with the differential case, a pinion gear that is held by the differential carrier, and a sun gear and a ring gear that mesh with the pinion gear. Including. The differential case has a cylindrical shape, and a differential carrier is fitted therein. The differential carrier holds a plurality of pinion gears. Helical teeth are formed on the surface of the pinion gear, and a ring gear is disposed outside the track on which the pinion gear is disposed. A sun gear is disposed inside the track on which the pinion gear is disposed. Helical teeth are formed on the surfaces of the ring gear and the sun gear, respectively, and the helical teeth mesh with the helical teeth of the pinion gear. Torque from the engine is input to the pinion gear through the differential case and the differential carrier. Torque input to the pinion gear is finally distributed to the front wheels and the rear wheels via the sun gear and the ring gear. The ratio of torque distribution to the front and rear wheels is changed by the frictional force of the sliding surface between the sun gear and the differential carrier and the frictional force of the sliding surface between the differential case and the ring gear.

  In the center differential employing the torque sensitive LSD, when traveling straight, a part of the torque input to the pinion gear via the sun gear is distributed to the front wheels. A part of the torque input to the pinion gear via the ring gear is distributed to the rear wheels. The ratio of torque distribution during straight traveling is 40 (front wheels) vs. 60 (rear wheels).

  During a turn in which a rotational difference occurs between the front and rear wheels, a thrust force is generated by the helical teeth of the pinion gear meshing with other helical teeth. With this thrust force, the sun gear is pressed against the differential carrier, and the ring gear is pressed against the differential case. Accordingly, the differential between the sun gear and the differential carrier is limited by the frictional force of the sliding surface between the sun gear and the differential carrier. Further, the differential force between the differential case and the ring gear is limited by the frictional force of the sliding surface between the differential case and the ring gear. Therefore, a part of the torque input to the sun gear is transmitted to the differential carrier, and finally transmitted to the ring gear through the differential case. As a result, the differential differential of the center differential is performed, and the torque distribution from the rear is further increased than the torque distribution at the time of straight traveling.

  In the center differential employing the torque sensitive LSD, for example, when starting in a high steering angle state, stick slip may occur on the friction sliding surface that performs differential restriction. Here, the stick slip refers to a phenomenon in which a sudden slip occurs instantaneously. When a stick-slip occurs, the torque distribution to the front and rear wheels changes abruptly, which induces torsional resonance of the drive system (such as a shaft that transmits torque). Thereby, the floor surface of the vehicle may vibrate. Therefore, a technique for reducing vibration due to stick-slip has been proposed.

  Japanese Patent Laying-Open No. 2006-87763 (Patent Document 1) discloses that a limiting unit (clutch) for limiting differential of a differential device (center differential) that connects a first wheel and a second wheel, and a vehicle A determination unit for determining whether or not the vehicle is starting, a steering angle detection unit for detecting the steering angle of the vehicle, and an angle at which the vehicle is determined to be starting and the steering angle is predetermined. If larger, a control device is disclosed that includes a control unit for controlling the limiting unit to limit the differential of the differential device.

According to the control device described in this publication, when the vehicle is determined to be in a starting state and the steering angle is larger than a predetermined angle, the differential of the differential device is limited. Thus, if the differential of the differential device is limited before stick slip occurs, the occurrence of stick slip can be suppressed. Therefore, generation | occurrence | production of the vibration by a slick slip can be suppressed. Further, if the differential of the differential device is limited at the timing opposite to the vibration due to stick slip, the torque distribution to the first wheel and the second wheel is suddenly changed, and the vibration opposite to the vibration due to stick slip. Can be generated. Therefore, the vibration caused by the stick slip can be canceled by the vibration having the opposite phase, and the vibration caused by the stick slip can be suppressed. As a result, it is possible to suppress vibration at the time of starting in a high steering angle state.
JP 2006-88763 A

  However, in the control device described in Japanese Patent Application Laid-Open No. 2006-88763, since the operation of the center differential is limited by the clutch at the time of starting when the torque of the drive source rises, a large torque can be rapidly input to the clutch. Therefore, the durability of the clutch can be impaired.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a vehicle control device that can reduce vibration without impairing durability.

  A vehicle control device according to a first aspect of the present invention is a vehicle control device provided with a drive source and a differential mechanism that transmits torque output from the drive source to the first wheel and the second wheel. . The control device detects a rotational speed of at least one of the first wheel and the second wheel, a means for detecting a steering angle of the vehicle, and an accelerator opening. And output torque of the drive source when the vehicle speed is smaller than the first threshold, the steering angle of the vehicle is larger than the second threshold, and the accelerator opening is larger than the third threshold. And a means for controlling so that the rate of increase is small.

  According to this configuration, the rotational speed of at least one of the first wheel and the second wheel is smaller than the first threshold, the steering angle of the vehicle is larger than the second threshold, and When the accelerator opening is larger than the third threshold value, the rate of increase in the output torque of the drive source is controlled to be small. That is, when starting with a large steering angle, the rate of increase in the output torque of the drive source is reduced. Thereby, even if it does not restrict | limit the differential of a differential mechanism (for example, center differential) using a clutch etc., it can make it difficult to produce a stick slip. Therefore, it is possible to provide a vehicle control device that can reduce vibration without impairing durability.

  In the vehicle control apparatus according to the second invention, in addition to the configuration of the first invention, the first wheel is a front wheel. The second wheel is a rear wheel. The differential mechanism is a center differential.

  According to this configuration, vibration that can occur in the center differential that distributes torque to the front and rear wheels can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  A vehicle equipped with a control device according to an embodiment of the present invention will be described with reference to FIG. This vehicle is a four-wheel drive vehicle. Torque generated in engine 100 is input to center differential 300 through transmission 200. A motor may be used as a drive source instead of engine 100.

  Torque input to the center differential 300 is distributed to two paths. One is a route distributed to the front wheels 406 via the front propeller shaft 400, the front differential 402 and the front drive shaft 404. The other is a path distributed to the rear wheels 506 via the rear propeller shaft 500, the rear differential 502 and the rear drive shaft 504.

  The center differential 300 is a torque sensitive LSD. When the vehicle travels straight, center differential 300 distributes torque to the front and rear wheels at a predetermined ratio. When a difference occurs in the rotational speeds of the front and rear wheels during turning, the center differential 300 changes the ratio of torque distributed to the front and rear wheels. Further, the differential of the center differential 300 is limited by the control coupling 600.

  Engine 100, transmission 200, and control coupling 600 are controlled by an ECU (Electronic Control Unit) 700. In this embodiment, engine 100, transmission 200, and control coupling 600 are controlled by one ECU 700, but a plurality of ECUs may be provided.

  The ECU 700 receives detection results from a throttle opening sensor 702, a steering angle sensor 704, a G sensor 706, a front wheel speed sensor 708, a rear wheel speed sensor 710, an accelerator opening sensor 712, a stop lamp switch 714, and a position sensor 716. The signal to represent is input.

  The throttle opening sensor 702 detects the opening of a throttle valve (not shown). The steering angle sensor 704 detects the steering angle of the steering wheel. The G sensor 706 detects the longitudinal acceleration of the vehicle. Front wheel speed sensor 708 detects the rotational speed of front wheel 406. Rear wheel speed sensor 710 detects the rotational speed of rear wheel 506. The accelerator opening sensor 712 detects the accelerator opening (the amount of depression of the accelerator pedal). The stop lamp switch 714 detects whether or not the brake pedal has been depressed. The position sensor 716 detects the position of the shift lever.

  ECU 700 performs arithmetic processing based on signals transmitted from these sensors and switches, a map and a program stored in a memory (not shown). Thereby, ECU 700 controls equipment mounted on the vehicle so that the vehicle is in a desired driving state. In the present embodiment, ECU 700 controls control coupling 600 by controlling the hydraulic pressure supplied to control coupling 600 by linear solenoid 800.

  The center differential 300 and the control coupling 600 will be further described with reference to FIG.

  The center differential 300 is composed of planetary gears. Center differential 300 includes a differential carrier 302, a pinion gear 304, a ring gear 306, a sun gear 308, and a differential case 310.

  The differential carrier 302 is connected to an input shaft 900 that is connected to the output shaft of the transmission 200. Further, the differential carrier 302 is fitted into the cylindrical differential case 310. Therefore, the differential carrier 302 rotates together with the input shaft 900 and the differential case 310.

  A plurality of pinion gears 304 are rotatably held in the internal space of the differential carrier 302. The torque of engine 100 transmitted through transmission 200 is input to pinion gear 304 through differential carrier 302. Helical teeth are provided on the surface of the pinion gear 304.

  A ring gear 306 is disposed outside the track on which the pinion gear 304 is disposed. A sun gear 308 is disposed inside the track on which the pinion gear 304 is disposed. Helical teeth are provided on the surfaces of the ring gear 306 and the sun gear 308. The helical teeth of the ring gear 306 and the helical teeth of the sun gear 308 mesh with the helical teeth of the pinion gear 304. Note that inclined teeth may be provided instead of helical teeth.

  Ring gear 306 is connected to rear output shaft 1000 for driving the rear wheels. Sun gear 308 is coupled to drive gear 1100. Drive gear 1100 is connected to driven gear 1102 via a chain. The driven gear 1102 is connected to a front output shaft 1104 for driving front wheels.

  When the vehicle travels straight, part of the torque input to the pinion gear 304 is distributed to the front wheels 406 via the sun gear 308. Further, part of the torque input to the pinion gear 304 is distributed to the rear wheel 506 via the ring gear 306. The ratio of torque distribution to the front and rear wheels is, for example, 40:60. The torque may be distributed at a ratio other than this.

  At the time of turning where a difference in rotation occurs between the front and rear wheels, a thrust force is generated by the helical teeth of the pinion gear 304 meshing with other helical teeth. Due to this thrust force, the sun gear 308 is pressed against the differential carrier 302. For this reason, the differential is limited so that the rotational difference among the differential carrier 302, the ring gear 306, and the sun gear 308 is reduced by the frictional force of the sliding surface.

  In this case, a part of the torque transmitted from the pinion gear 304 to the sun gear 308 is transmitted to the ring gear 306 via the differential carrier 302 and the differential case 310. As a result, the torque distribution is more deviated from the rear wheel than when traveling straight.

  The differential limitation is performed using the control coupling 600 in addition to the function of the center differential 300 itself. The control coupling 600 includes a control clutch 602 and an outer coupling 604. The control clutch 602 is provided between the rear output shaft 1000 and the outer coupling 604. The control clutch 602 is controlled by controlling the hydraulic pressure supplied to the piston of the control coupling 600 by the linear solenoid 800.

  The outer coupling 604 is connected to the differential case 310. That is, the outer coupling 604 is connected to the differential carrier 302 via the differential case 310.

  When hydraulic pressure is supplied to the piston of the control coupling 600 and the control clutch 602 is changed from the released state to the engaged state or the semi-engaged state, the differential between the rear output shaft 1000 and the outer coupling 604 is limited. As a result, the differential between the rear output shaft 1000 and the differential carrier 302 is limited.

  Here, the rear output shaft 1000 is connected to the ring gear 306. Therefore, the differential between the differential carrier 302 and the ring gear 306 is limited. As a result, the differential among the differential carrier 302, the ring gear 306, and the sun gear 308 is limited.

  The function of ECU 700 will be described with reference to FIG. It should be noted that the functions of ECU 700 described below may be realized by software, or may be realized by hardware.

  ECU 700 includes a wheel speed detection unit 720, a steering angle detection unit 722, an accelerator opening detection unit 724, and an increase rate control unit 726.

  The wheel speed detection unit 720 detects the rotational speeds of the front wheels 406 and the rear wheels 506 based on signals transmitted from the front wheel speed sensor 708 and the rear wheel speed sensor 710. Note that the rotational speed of one of the front wheel 406 and the rear wheel 506 may be detected.

  The steering angle detection unit 722 detects the steering angle of the steering wheel based on the signal transmitted from the steering angle sensor 704. The accelerator opening detector 724 detects the accelerator opening based on the signal transmitted from the accelerator opening sensor 712.

  Increase rate control unit 726 controls the increase rate of output torque of engine 100. More specifically, the rotational speeds of the front wheels 406 and the rear wheels 506 are smaller than the first threshold value (stopped), the steering angle of the steering wheel is larger than the second threshold value, and the accelerator opening is the first threshold value. When the threshold value is larger than 3, the control is performed so that the rate of increase of the output torque becomes small as shown by the solid line in FIG. That is, when the vehicle starts with a large steering angle, the rate of increase in the output torque of engine 100 is reduced. When the increase rate of the output torque is reduced, as shown in FIG. 4, the differential rotational speed of the center differential 300 (the difference between the rotational speed of the front propeller shaft 400 and the rotational speed of the rear propeller shaft 500) increases. The output torque at is reduced.

  A control structure of a program executed by ECU 700 will be described with reference to FIG. The program executed by ECU 700 may be recorded on a recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) and distributed to the market.

  In step (hereinafter step is abbreviated as S) 10, ECU 700 detects the rotational speeds of front wheel 406 and rear wheel 506. In S12, ECU 700 detects the steering angle of the steering wheel. In S14, ECU 700 detects the accelerator opening.

  In S20, ECU 700 determines whether or not the rotational speeds of front wheel 406 and rear wheel 506 are smaller than the first threshold value. That is, it is determined whether or not the vehicle is stopped. Note that it may be determined whether the rotational speed of one of the front wheel 406 and the rear wheel 506 is smaller than the first threshold value.

  If the rotational speeds of front wheel 406 and rear wheel 506 are smaller than the first threshold value (YES in S20), the process proceeds to S22. If not (NO in S20), the process returns to S10.

  In S22, ECU 700 determines whether or not the steering angle of the steering wheel is greater than the second threshold value. If the steering angle of the steering wheel is greater than the second threshold value (YES in S22), the process proceeds to S24. If not (NO in S22), the process returns to S10.

  In S24, ECU 700 determines whether or not the accelerator opening is larger than a third threshold value. If the accelerator opening is larger than the third threshold value (YES in S24), the process proceeds to S30. If not (NO in S24), the process returns to S10.

  In S30, ECU 700 performs control so that the rate of increase in output torque of engine 100 is reduced.

  An operation of the control device according to the present embodiment based on the above-described structure and flowchart will be described.

  When ECU 700 is activated, the rotational speeds of front wheel 406 and rear wheel 506 are detected (S10). The steering angle of the steering wheel is detected (S12). Further, the accelerator opening is detected (S14).

  The rotational speeds of front wheel 406 and rear wheel 506 are smaller than the first threshold value (YES in S20), the steering angle of the steering wheel is larger than the second threshold value (YES in S22), and the accelerator opening is the first threshold value. If greater than 3 threshold values (YES in S24), the rate of increase in output torque of engine 100 is reduced (S30).

  That is, when the vehicle starts with a large steering angle, the rate of increase in the output torque of engine 100 is reduced. Accordingly, stick slip can be made difficult to occur without limiting the differential of the center differential 300 using the control clutch 602 of the control coupling 600. Therefore, vibration can be reduced without impairing the durability of the control clutch 602.

  As described above, according to the control device of the present embodiment, the rotational speeds of the front wheels and the rear wheels are smaller than the first threshold value, the steering angle of the steering wheel is larger than the second threshold value, and the accelerator is opened. If the degree is larger than the third threshold value, the rate of increase in engine output torque is reduced. This makes it possible to prevent stick-slip from occurring even without using the control coupling control clutch to limit the differential of the center differential. Therefore, vibration can be reduced without impairing durability.

  In the embodiment described above, the center differential 300 and the control coupling 600 are arranged in series. However, as shown in FIG. 6, the center differential 300 and the control coupling 600 may be arranged in parallel. Good.

  In FIG. 6, an intermediate gear 1106 is provided so as to mesh with the drive gear 1100 and the driven gear 1102. A differential between the inner shaft 606 connected to the intermediate gear and the outer coupling 608 connected to the differential case 312 of the center differential 300 is limited by the control clutch 602. Thereby, the rotation difference between the front and rear wheels is limited.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic block diagram of the vehicle carrying the control apparatus which concerns on this Embodiment. It is sectional drawing which shows the center differential and control coupling which are arrange | positioned in series. It is a functional block diagram of ECU. It is a timing chart which shows transition of engine output torque etc. It is a flowchart which shows the control structure of the program which ECU performs. It is sectional drawing which shows the center differential and control coupling which are arrange | positioned in parallel.

Explanation of symbols

  100 engine, 200 transmission, 300 center differential, 302 differential carrier, 304 pinion gear, 306 ring gear, 308 sun gear, 310, 312 differential case, 400 front propeller shaft, 402 front differential, 404 front drive shaft, 406 front wheel, 500 rear propeller shaft , 502 Rear differential, 504 Rear drive shaft, 506 Rear wheel, 600 Control coupling, 602 Control clutch, 604, 608 Outer coupling, 606 Inner shaft, 702 Throttle opening sensor, 704 Rudder angle sensor, 706 G sensor, 708 Front wheel speed sensor, 710 Rear wheel speed sensor, 7 2 Accelerator opening sensor, 714 Stop lamp switch, 716 Position sensor, 720 Wheel speed detector, 722 Steering angle detector, 724 Accelerator opening detector, 726 Lift rate controller, 800 Linear solenoid, 900 Input shaft, 1000 Rear Output shaft, 1100 drive gear, 1102 driven gear, 1104 front output shaft, 1106 intermediate gear.

Claims (2)

A vehicle control device provided with a drive source and a differential mechanism that transmits torque output from the drive source to a first wheel and a second wheel,
Means for detecting the rotational speed of at least one of the first wheel and the second wheel;
Means for detecting a steering angle of the vehicle;
Means for detecting the accelerator opening;
The rotational speed of at least one of the first wheel and the second wheel is smaller than a first threshold, the steering angle of the vehicle is larger than a second threshold, and the accelerator opening Means for controlling so that the rate of increase of the output torque of the drive source is reduced when the value is larger than a third threshold value.   The vehicle control device according to claim 1, wherein the first wheel is a front wheel, the second wheel is a rear wheel, and the differential mechanism is a center differential.

Images