JP2004149054A - Torque distribution control device for four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance safety and reduce fuel consumption by adequately distributing the torque to four wheels according to the traveling circumstances. <P>SOLUTION: The torque transmitted from an engine to drive wheels is distributed to driven wheels via a torque transmission clutch as necessary. The pre-torque is operated in a feed-forward manner based on the vehicle speed, the throttle opening degree and the gear shift step of a transmission. A compensation torque is determined in a feedback manner based on the vehicle speed and the rotational speed difference between the drive wheels and the driven wheels. A torque transmission clutch is controlled based on a command torque which is obtained by the addition of the pre-torque and the compensation torque, so that the command torque is distributed to the driven wheels. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a torque distribution control device that controls torque distribution to driven wheels of a four-wheel drive vehicle.
[0002]
[Prior art]
In a torque distribution control device for a four-wheel drive vehicle having a torque transmission clutch for distributing torque transmitted from an engine to a driven wheel to a driven wheel according to a rotational speed difference between the driven wheel and a driven wheel, the acceleration of the vehicle is controlled to a predetermined value. If the value is equal to or greater than the value, by selecting an acceleration mode map in which the rate of increase in the torque allocated to the driven wheels with respect to the increase in the rotational speed difference between the drive wheel and the driven wheel is increased, a large torque is provided for the rotational speed difference. If the torque is smaller than a predetermined value, the torque is distributed to the driven wheels. Japanese Patent Application Laid-Open No. 2001-71781 discloses that the wheels are distributed to driven wheels.
[0003]
[Patent Document 1]
JP 2001-71781 A (pages 4, 5; FIG. 3)
[0004]
[Problems to be solved by the invention]
According to the above-mentioned conventional method, stable acceleration and starting can be performed by distributing a large torque to driven wheels when accelerating or starting on a low μ road, and distributed to driven wheels during tight corner turning at low speed. Tight corner braking can be avoided by reducing the torque. However, merely determining whether or not the acceleration of the vehicle is equal to or higher than a predetermined value, for example, when cornering at a medium speed where the acceleration is equal to or lower than the predetermined value, distributes the torque necessary for improving stability to the driven wheels. I can't. As described above, according to the conventional method, it is not possible to sufficiently grasp the traveling state, and it is not possible to directly reflect the traveling state of the vehicle or the driver's intention to distribute the torque to the driven wheels.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is an object of the present invention to improve the stability and reduce the fuel consumption by appropriately distributing the torque to the four wheels according to the driving situation.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a structural feature of the invention according to claim 1 is a torque distribution of a four-wheel drive vehicle including a torque transmission clutch that distributes torque transmitted from an engine to drive wheels to driven wheels. A control device for calculating a pre-torque transmitted to a driven wheel based on a vehicle speed, a throttle opening and a gear position of a transmission, and a correction for calculating a correction torque based on a rotational speed difference between a driving wheel and a driven wheel; A torque calculating means, and a command torque calculating means for calculating a command torque by adding the pre-torque and the correction torque, wherein the torque transmission clutch is controlled based on the command torque input from the command torque calculating means. It is.
[0007]
According to a second aspect of the present invention, in the first aspect, the correction torque calculating means calculates the correction torque based on a rotational speed difference between a driving wheel and a driven wheel and a vehicle speed.
[0008]
According to a third aspect of the present invention, in the first or second aspect, the pre-torque calculating means includes a pre-torque map in which a pre-torque transmitted to a driven wheel is set according to a vehicle speed and a throttle opening. A plurality of pre-torque maps are provided for each shift speed, and a pre-torque map corresponding to the selected shift speed is selected to calculate the pre-torque.
[0009]
According to a fourth aspect of the present invention, in the first or second aspect, the pre-torque calculation means includes a pre-torque map in which a pre-torque transmitted to a driven wheel is set according to a vehicle speed and a throttle opening. At least one gear position is provided, and a pre-torque obtained from the pre-torque map according to the vehicle speed and the throttle opening is corrected and calculated according to the difference between the one gear position and the selected gear position.
[0010]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the pre-torque calculating means detects a vehicle speed calculated from a wheel speed detected by a wheel speed sensor and a vehicle speed detected by a throttle sensor. The pre-torque transmitted to the driven wheels is calculated based on the throttle opening and the gear position detected by the gear position sensor.
[0011]
A structural feature of the invention according to claim 6 is that, in any one of claims 1 to 5, the torque distribution device includes: an electromagnetic clutch that distributes torque transmitted from an engine to drive wheels to driven wheels; A current control circuit is provided for applying a command current required for the electromagnetic clutch to transmit the command torque to the driven wheels to an electromagnetic coil of the electromagnetic clutch.
[0012]
Function and Effect of the Invention
In the invention according to claim 1 configured as described above, the torque transmitted from the engine to the drive wheels is distributed to the driven wheels via the torque transmission clutch as necessary. The pre-torque is calculated on a feed-forward basis based on the vehicle speed, the throttle opening, and the transmission gear. The correction torque is calculated in a feedback manner based on the rotational speed difference between the driving wheel and the driven wheel. The torque transmission clutch is controlled based on the command torque obtained by adding the pre-torque and the correction torque, and the command torque is distributed to the driven wheels. As a result, torque is distributed to the four wheels to improve stability when starting at low speeds or when cornering at medium speeds, and in running conditions such as cruising when selecting high speeds. Fuel efficiency can be reduced without distributing much torque to the driving wheels. In this way, it is possible to directly reflect the driver's intention and transmit an appropriately distributed torque to the driven wheels.
[0013]
In the invention according to claim 2 configured as described above, the correction torque is calculated in a feedback manner based on the rotational speed difference between the drive wheel and the driven wheel and the vehicle speed. It is possible to distribute the torque to the driven wheels reflecting the driver's intention.
[0014]
In the invention according to claim 3 configured as described above, a plurality of pre-torque maps in which the pre-torque distributed to the driven wheels is set in accordance with the vehicle speed and the throttle opening are provided for each transmission gear, and the selected gear is selected. Since the pre-torque is calculated from the pre-torque map corresponding to the gear, an optimum pre-torque map that directly reflects the driver's intention indicated by the gear is provided for each gear. Can be set.
[0015]
In the invention according to claim 4 configured as described above, a pre-torque map in which the pre-torque transmitted to the driven wheels is set according to the vehicle speed and the throttle opening is provided corresponding to at least one shift speed of the transmission. A pre-torque is obtained from the pre-torque map according to the vehicle speed and the throttle opening, and the pre-torque is corrected and calculated according to the difference between the selected shift speed and one shift speed. Thus, in addition to the effect of the first aspect, an appropriate torque can be distributed to the driven wheels based on one pretorque map by directly reflecting the driver's intention indicated by the gear position. .
[0016]
In the invention according to claim 5 configured as described above, the vehicle speed calculated from the wheel speed of the driven wheel detected by the wheel speed sensor, the throttle opening detected by the throttle sensor, and the vehicle speed calculated by the gear position sensor Since the pre-torque to be transmitted to the driven wheels is calculated based on the gear position, the driving condition can be reliably detected by each sensor, and the torque suitable for the driving condition can be distributed to the driven wheels.
[0017]
In the invention according to claim 6 configured as described above, by applying the command current to the electromagnetic coil, the electromagnetic clutch transmits the command torque according to the traveling condition to the driven wheels, so that a proper configuration can be achieved with a simple configuration. The torque can be transmitted to the driven wheels to improve stability and fuel efficiency.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram conceptually showing a configuration of a four-wheel drive vehicle equipped with a four-wheel drive vehicle torque distribution control device according to an embodiment of the present invention. In FIG. 1, a transaxle 11 is attached to an output side of an engine 10. The transaxle 11 includes a transmission 12, a transfer, and a front differential 13 integrally. The transaxle 11 outputs the output torque of the engine 10 to the front axle shaft 14 via the front differential 13 to drive the left and right front wheels Wfl and Wfr, which are driving wheels, and to output to the first propeller shaft 15. The first propeller shaft 15 is connected to a second propeller shaft 20 via an electromagnetic clutch 16. The electromagnetic clutch 16 is controlled based on the command torque calculated by the electronic control device 17 according to the running condition of the vehicle, and distributes the command torque to the rear wheels Wrl and Wrr, which are driven wheels, via the second propeller shaft 20. I do. The current control circuit 18 applies a command current corresponding to the command torque calculated by the control device 17 to the exciting coil 19 of the electromagnetic clutch 16, and the electromagnetic clutch 16 presses a plurality of clutch plates according to the command current. The command torque is transmitted from the first propeller shaft 15 to the second propeller shaft 20. The torque transmitted to the second propeller shaft 20 is transmitted to the rear differential 21, output from the rear differential 21 to the rear axle shaft 22, and distributed to the left and right rear wheels Wrl and Wrr that are driven wheels. The current control circuit 18, the electromagnetic clutch 16, and the like constitute a torque distribution device 23 that distributes the torque transmitted from the engine 10 to the drive wheels Wfl, Wfr to the driven wheels Wrl, Wrr.
[0019]
Wheel speed sensors Sfl, Sfr, Srl, Srr for detecting the wheel speeds of the drive wheels Wfl, Wfr and the driven wheels Wrl, Wrr are provided for each wheel. Each wheel speed sensor also serves as a wheel speed sensor for an antilock brake system (ABS) that independently controls each wheel brake Bfl, Bfr, Brl, Brr that brakes each wheel. Further, the throttle body of the intake system of the engine 10 is provided with a throttle opening sensor Sth for detecting the throttle opening θ of the throttle valve 24 for adjusting the intake air amount in accordance with the accelerator pedal depression amount. The transmission 12 is provided with a gear position sensor Sg that detects the position of a shift lever that performs a gear change to establish each gear stage G.
[0020]
As shown in FIG. 2, the electronic control unit 17 is connected to the wheel speed sensors Sfl, Sfr, Srl, Srr and the throttle opening sensor Sth, and is also connected to the current control circuit 18 of the torque distribution unit 23. The electronic control unit 17 includes a CPU 25 that performs various arithmetic processes for controlling the torque distribution device 23, a ROM 26 in which a torque distribution control program shown in FIG. The CPU 25 receives a wheel speed signal, a throttle opening signal, and a gear position signal from a RAM 27 in which necessary data is read and written as needed, and wheel speed sensors Sfl, Sfr, Srl, Srr, a throttle opening sensor Sth, and a gear position sensor Sg. And an input / output circuit 28 that outputs a command current I, which is a result of the calculation according to the above, to the current control circuit 18.
[0021]
As shown in FIG. 3, the electronic control unit 17 calculates a command current I which must be applied to the electromagnetic coil 19 in order for the electromagnetic clutch 16 to transmit the calculated command torque T to the driven wheels Wrl and Wrr. Output to the control circuit 18. The relationship between the command torque T transmitted by the electromagnetic clutch 16 and the command current I is stored in the ROM 26 as a torque current map 29, and the command current corresponding to the command torque is read from the torque current map 29. Note that the command current may be obtained from a calculation formula indicating the relationship between the command torque and the command current.
[0022]
The current control circuit 18 detects the actual current Ir flowing through the electromagnetic coil 19 of the electromagnetic clutch 16 by the current detection unit 30 and subtracts the difference between the command current I input from the electronic control unit 17 and the actual current Ir from the current detection circuit 30. , And a voltage amplified by the PI control unit 32 and pulse width modulated by the PWM output conversion unit 33 is applied from the output drive unit 34 to the base of the switching transistor 35. Since the switching transistor 35 is connected to the battery B in series with the electromagnetic coil 19, the command current I is applied to the electromagnetic coil 19.
[0023]
The electronic control unit 17 calculates a pre-torque Tff to be transmitted to the driven wheels Wrl, Wrr based on the vehicle speed V, the throttle opening θ, and the gear stage G of the transmission 12, a pre-torque calculating unit 36, the vehicle speed V, the driving wheels, and the driven wheels. And a correction torque calculating means 37 for calculating the correction torque Tfb based on the rotational speed difference ΔN with respect to the above, and an adding means 38 for calculating the command torque T by adding the pre-torque and the correction torque.
[0024]
The vehicle speed V is calculated from the average value of the rotation speeds of the driven wheels Wrl and Wrr detected by the wheel speed sensors Srl and Srr, and the throttle opening θ is obtained by fully opening the throttle valve 24 detected by the throttle sensor Sth. The gear ratio is expressed as a percentage with respect to the state, and the shift speed is obtained from the position of the shift lever of the transmission 12 detected by the gear position sensor Sg. The shift speed G may be calculated from the vehicle speed V and the engine speed, or in the case of a vehicle with an automatic transmission, the shift speed calculated by the ECU for controlling the automatic transmission may be used.
[0025]
The pre-torque calculating means 36 stores in the ROM 26 a plurality of pre-torque maps MTff1, MTff2, MTff3... In which pre-torques Tff transmitted to the driven wheels Wrl and Wrr are set for each transmission speed G according to the vehicle speed V and the throttle opening θ. The pre-torque map MTff corresponding to the shift speed is selected by executing the registered torque distribution control program, and the pre-torque Tff is calculated from the vehicle speed V and the throttle opening θ. In the pre-torque map MTff1 at the first speed shown in FIG. 4, as a whole tendency, the pre-torque Tff is large near the vehicle speed V of zero, decreases as the vehicle speed increases to a predetermined speed, and increases the throttle opening θ. The rate of increase is large. When the vehicle speed becomes equal to or higher than the predetermined speed, the pre-torque Tff is small, and the rate of increase with the increase in the throttle opening θ is small.
[0026]
Even at the same vehicle speed V and the same throttle opening θ, the appropriate torque transmitted to the driven wheels varies depending on the driving conditions in order to improve the running stability of the vehicle or improve the fuel efficiency. That is, at the time of starting when the low gear is selected, at the time of cornering at the medium gear, and the like, it is necessary to surely distribute torque to the four wheels to improve stability. Conversely, when cruising at a high speed, for example, it is not necessary to distribute much torque to the driven wheels, and it is desirable to reduce the torque distribution to the driven wheels to improve fuel efficiency. In order to reflect such characteristics in the pre-torque map, as the shift speed increases, the pre-torque Tff when the vehicle speed V is low is small, the increasing rate of the pre-torque Tff with respect to the increase in the throttle opening θ is small, and the vehicle speed is a predetermined speed. The above pre-torque Tff is also set small. Since the pre-torque map MTff set in this manner is registered in the ROM 26 for each shift speed, an appropriate torque for the driven wheels Wrl, Wrr is directly reflected by the driver's intention indicated by the selected shift speed. An allocation can be made.
[0027]
It should be noted that a plurality of pretorque maps MTff are not provided for each shift speed, but a reference, for example, one pretorque map for the third speed is prepared, and for the first speed, one pretorque Tff obtained from the reference pretorque map is used. The speed may be 0.5 times or 0.5 times at the 5th speed. Further, the pre-torque Tff may be calculated from the vehicle speed V and the throttle opening θ by a predetermined formula, instead of being calculated from the pre-torque map MTff.
[0028]
In the correction torque calculating means 37, a correction torque map MTfb in which the correction torque Tfb for the rotational speed difference ΔN between the driving wheel and the driven wheel is set using a plurality of vehicle speeds V as parameters is registered in the ROM 26, and the torque distribution control program is executed. Then, based on the correction torque map MTfb, the correction torque Tfb is calculated from the rotation speed difference ΔN between the driving wheel and the driven wheel and the vehicle speed V. In the correction torque map MTfb shown in FIG. 5, as a general tendency, when the rotation speed difference ΔN between the driving wheel and the driven wheel is zero, the correction torque Tfb is zero, and the correction torque Tfb increases as the rotation speed difference ΔN increases. It increases with a constant slope in proportion, and decreases when the slope exceeds a predetermined value. The correction torque Tfb is set to increase as the vehicle speed V decreases, and to decrease as the vehicle speed V increases.
[0029]
Next, the operation of the torque distribution control device for a four-wheel drive vehicle according to the above embodiment will be described. The CPU 25 executes the torque distribution program of FIG. 6 at minute time intervals, and first takes in various signals from the wheel speed sensors Sfl, Sfr, Srl, Srr, the throttle sensor Sth, and the gear position sensor Sg (step 41). ). The vehicle speed V is calculated based on the average value of the rotation speeds of the driven wheels Wrl and Wrr detected by the wheel speed sensors Srl and Srr (step 42). The average rotation speed of the driven wheels Wrl, Wrr is subtracted from the average rotation speed of the driven wheels Wfl, Wfr detected by the wheel speed sensors Sfl, Sfr, and the rotation speed difference ΔN between the driven wheel and the driven wheel is calculated. Is performed (step 43). The pre-torque map TM corresponding to the gear position G detected by the gear position sensor Sg is selected, and the pre-torque Tff corresponding to the vehicle speed V and the throttle opening θ detected by the throttle sensor Sth is calculated in a feedforward manner ( Step 44). Based on the corrected torque map MTfb, the corrected torque Tfb corresponding to the rotation speed difference ΔN and the vehicle speed V is calculated in a feedback manner (step 45). In step 46 constituting the torque calculating means 38, the pre-torque Tff and the correction torque Tfb are added to calculate the command torque T. A command current I that must be applied to the electromagnetic coil 19 in order for the electromagnetic clutch 16 to transmit the command torque T is read from the torque current map 29 storing the command current I for the command torque T (step 47). Output to the current control circuit 18. (Step 48). The current control circuit 18 amplifies the difference between the command current I and the actual current Ir flowing through the electromagnetic coil 19 of the electromagnetic clutch 16 to perform pulse width modulation, outputs the result to the switching transistor 35, and outputs the command current I to the electromagnetic coil 19. Apply. Thus, the electromagnetic clutch 16 transmits the command torque T from the first propeller shaft 15 to the second propeller shaft 20 and distributes the command torque T to the rear wheels Wrl, Wrl, which are driven wheels.
[0030]
At this time, for example, when the first speed is selected and the vehicle starts, the first pre-torque map TMff1 selected corresponding to the first speed shows a large pre-torque Tff1 when the vehicle speed V is small and the throttle opening θ is large. Since it is set, a large torque is also distributed to the driven wheels at the time of starting, and the vehicle can start without slipping. In the pre-torque map TM selected at the middle speed, the pre-torque Tff is generally set to a medium level when the vehicle speed V is the middle speed regardless of the throttle opening θ. Appropriate torque distribution is performed on the driven wheels, and the four wheels can reliably grip the road surface and perform stable cornering. In the pre-torque map TM selected at the high speed stage, when the vehicle speed V is high, the pre-torque Tff is set to be small even if the throttle opening θ is considerably large, so that it is possible to improve fuel efficiency during cruising traveling at the high speed stage. it can. In this way, in other words, the pre-torque map MTff that directly reflects the driver's intention to select the gear is set for each gear, and the pre-torque is calculated from the pre-torque map MTff corresponding to the gear. It is possible to distribute the torque optimal for the driving situation to the driven wheels Wrl and Wrr.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a torque distribution control device for a four-wheel drive vehicle according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an electronic control device.
FIG. 3 is a block diagram showing functions of each unit of the torque distribution control device for a four-wheel drive vehicle according to the embodiment of the present invention.
FIG. 4 is a diagram showing an example of a first pretorque map selected at a first speed.
FIG. 5 is a view showing a correction torque map.
FIG. 6 is a diagram showing a torque distribution program.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Transaxle, 12 ... Transmission, 13 ... Front differential, 14 ... Front axle, 15 ... First propeller shaft, 16 ... Electromagnetic clutch, 17 ... Electronic control device, 18 ... Current control circuit, 19 ... Electromagnetic Coil, 20 second propeller shaft, 21 rear differential, 22 rear axle, 23 torque distribution device, 29 torque current map, 36 pre-torque calculation means, 37 correction torque calculation means, 38 addition means, Wfl , Wfr: front wheels (drive wheels), Wrl, Wrr: rear wheels (driven wheels), Sfl, Sfr, Srl, Srr: wheel speed sensors, Sth: throttle opening sensors, Sg: gear position sensors.

Claims (6)

In a torque distribution control device for a four-wheel drive vehicle having a torque transmission clutch for distributing torque transmitted from an engine to drive wheels to driven wheels, the torque is transmitted to driven wheels based on a vehicle speed, a throttle opening, and a transmission gear position. Pre-torque calculation means for calculating pre-torque, correction torque calculation means for calculating correction torque based on a rotational speed difference between a driving wheel and a driven wheel, and command torque calculation for calculating command torque by adding the pre-torque and correction torque And a torque distribution control device for a four-wheel drive vehicle, wherein the torque transmission clutch is controlled based on the command torque input from the command torque calculation means. 2. The torque distribution control device for a four-wheel drive vehicle according to claim 1, wherein the correction torque calculation means calculates a correction torque based on a rotational speed difference between a driving wheel and a driven wheel and a vehicle speed. 3. The pre-torque calculating means according to claim 1, wherein the pre-torque calculating means provides a plurality of pre-torque maps in which the pre-torque transmitted to the driven wheels is set in accordance with the vehicle speed and the throttle opening for each transmission speed. A torque distribution control device for a four-wheel drive vehicle, wherein a pre-torque is calculated by selecting a corresponding pre-torque map. The pre-torque calculating means according to claim 1 or 2, wherein a pre-torque map in which a pre-torque transmitted to a driven wheel is set in accordance with a vehicle speed and a throttle opening is provided corresponding to at least one shift speed of the transmission. A torque distribution control device for a four-wheel drive vehicle, wherein a pre-torque obtained from the pre-torque map according to a degree is corrected and calculated according to a difference between the one shift speed and a selected shift speed. The vehicle according to any one of claims 1 to 4, wherein the pre-torque calculating means includes a vehicle speed calculated from a wheel speed detected by a wheel speed sensor, a throttle opening detected by a throttle sensor, and a shift detected by a gear position sensor. A torque distribution control device for a four-wheel drive vehicle, wherein a pre-torque transmitted to the driven wheels is calculated based on a gear. The torque distribution device according to any one of claims 1 to 5, further comprising: an electromagnetic clutch that distributes torque transmitted from the engine to the drive wheels to driven wheels; and an electromagnetic clutch that transmits the command torque to driven wheels. A torque distribution control device for a four-wheel drive vehicle, comprising a current control circuit for applying a required command current to an electromagnetic coil of the electromagnetic clutch.

Images