JP4281312B2 - Driving force distribution control device for four-wheel drive vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a driving force distribution control device for a four-wheel drive vehicle.
[0002]
[Prior art]
Conventionally, the driving force transmission ratio of the driving force transmission device is variably controlled based on the vehicle speed and the acceleration operation amount (for example, throttle opening in a gasoline engine vehicle), thereby distributing the driving force between the front wheel side and the rear wheel side. 2. Description of the Related Art A driving force distribution control device for a four-wheel drive vehicle that is variably controlled is known. Specifically, the driving force (transmission torque) corresponding to the vehicle speed and the acceleration operation amount is obtained with reference to a predetermined torque characteristic map, and the four-wheel drive is performed so that this torque is transmitted to the front wheel side or the rear wheel side. The vehicle driving force distribution control device controls the frictional engagement force of the electromagnetic clutch constituting the driving force transmission device. This torque characteristic map is a table map of transmission torque with the vehicle speed and the amount of acceleration operation as parameters, and is obtained in advance by experimental data using a vehicle model and well-known theoretical calculations.
[0003]
[Problems to be solved by the invention]
However, the driving force distribution control device for the conventional four-wheel drive vehicle has the following problems. For example, in an automatic vehicle (hereinafter referred to as “AT vehicle”), when the gear stage is in the D range and in an idling state, the driver does not perform an acceleration operation (accelerator pedal operation) due to a creep phenomenon. But the car moves forward. This is because the driving force of the engine in the idling state is transmitted to the driving wheel through an AT (automatic transmission) torque converter.
[0004]
And even during creep running and low acceleration running at the time of starting, on the extremely low μ road (road surface with extremely small road surface friction coefficient and slippery road) such as ice burn, the driving wheel (the front wheel in the front wheel drive base car) ) May slip. For example, when the vehicle is stopped on an uphill where an ice burn is formed, there is a possibility that the front wheels may slip at the moment when the driver shifts to the D range. In such a case, the amount of distribution of driving force to the driven wheel (rear wheel) side may be increased according to the differential rotation speed between the front wheel and the rear wheel.
[0005]
However, in general, for example, tight corner braking phenomenon when entering a garage or the like (for example, when a large amount of driving force is distributed to the rear wheels during turning, braking torque is generated on the front wheels due to the difference in the average turning radius between the front and rear wheels. In order to avoid the occurrence of phenomenon, the amount of distribution of driving force to the driven wheel is often limited. Therefore, it is not possible to increase the amount of driving force distributed to the rear wheel (driven wheel) based on the differential rotational speed between the front wheel and the rear wheel, and the front wheel (drive) when starting on an extremely low μ road surface. It was difficult to suppress the slip of the ring).
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a driving force distribution control device for a four-wheel drive vehicle capable of suppressing idling of the drive wheels at the time of starting. is there.
[0007]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the vehicle speed obtained by the vehicle speed detection means, the acceleration operation amount obtained by the acceleration operation amount detection means,The differential rotational speed between the driving wheel and the driven wheel obtained by the differential rotational speed detecting meansIn the driving force distribution control device for a four-wheel drive vehicle, the driving force distribution ratio of the driving force transmission device is variably controlled to control the amount of driving force distribution to the driven wheel side. Traveling state determining means for determining whether the state is a start timeAnd a correction amount calculation means for obtaining a correction driving force distribution amount based on the acceleration operation amount and the differential rotational speed;WithAboveWhen it is determined by the traveling state determination means that the vehicle is starting,The driving force distribution amount to the driven wheel side is smaller than the normal value of the driving force distribution amount obtained based on the vehicle speed, the acceleration operation amount, and the differential rotation speed.To be biggerAdd the corrected driving force distribution amount to the normal valueControl the driving force transmission rate of the driving force transmission deviceRukoAnd the gist.
[0008]
According to a second aspect of the present invention, in the first aspect of the invention, the traveling state determination unit includes a first comparison unit that compares the vehicle speed with a preset vehicle speed determination threshold, and the acceleration operation amount and the predetermined amount. Second comparing means for comparing the set acceleration operation amount determination threshold value, and determining whether or not the vehicle is starting based on a comparison result between the first comparing means and the second comparing means. This is the gist.
[0010]
  Claim3The invention described in claim1 or claim 2In the invention described inThe acceleration operation amount and theA characteristic map for determining the corrected driving force distribution amount based on the differential rotational speed is stored in the storage means in advance, and when the traveling state determining means determines that the vehicle is starting, the correction amount calculating means The gist is that the corrected driving force distribution amount is obtained based on the characteristic map stored in the storage means.
[0011]
  (Function)
  According to the first aspect of the present invention, the vehicle speed obtained by the vehicle speed detection means, the acceleration operation amount obtained by the acceleration operation amount detection means,The differential rotational speed between the driving wheel and the driven wheel obtained by the differential rotational speed detecting meansBased on the above, the driving force transmission rate of the driving force transmission device is variably controlled, so that the driving force distribution amount to the driven wheel side is variably controlled. And when it determines with the driving | running | working state of a vehicle being the time of start, the driving force transmission ratio of a driving force transmission device is controlled so that the amount of driving force distribution to a driven wheel side becomes larger than a normal value. For this reason, idling (slip) of driving theory at the time of start is suppressed.
Further, the corrected driving force distribution amount is obtained based on the acceleration operation amount and the differential rotation speed. When it is determined that the vehicle is starting, the corrected driving force distribution amount is added to the normal value. For this reason, at the time of start, the corrected driving force distribution amount corresponding to the differential rotation speed, in other words, the idling amount (slip amount) of the drive wheel is added to the normal value.
[0012]
According to the invention described in claim 2, in addition to the operation of the invention described in claim 1, a comparison result between the vehicle speed and a preset vehicle speed determination threshold value, and the acceleration operation amount and a preset acceleration operation are provided. It is determined whether or not the vehicle is starting based on the comparison result with the amount determination threshold. For this reason, it is accurately determined whether or not the vehicle is starting.
[0014]
  Claim3According to the invention described in claim1 or claim 2In addition to the operation of the invention described in the above, when it is determined that the vehicle is at the start,The acceleration operation amount and theThe corrected driving force distribution amount is obtained based on a characteristic map for obtaining the corrected driving force distribution amount based on the differential rotation speed. For this reason,Acceleration operation amount andAn appropriate correction driving force distribution amount corresponding to the differential rotational speed is obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is embodied in a driving force distribution control device for a four-wheel drive vehicle based on a front wheel drive will be described with reference to FIGS.
[0016]
(overall structure)
As shown in FIG. 1, the four-wheel drive vehicle 11 includes an engine 12 and a transaxle 13 that constitute an internal combustion engine. The transaxle has a transmission and a transfer. A pair of front axles 14 and 14 and a propeller shaft 15 are connected to the transaxle 13. Front wheels 16 and 16 are connected to both front axles 14 and 14, respectively. A driving force transmission device (coupling) 17 is connected to the propeller shaft 15, and a rear differential 18 is connected to the driving force transmission device 17 via a drive pinion shaft (not shown). Rear wheels 20 and 20 are connected to the rear differential 18 via a pair of rear axles 19 and 19.
[0017]
The driving force of the engine 12 is transmitted to the front wheels 16 and 16 via the transaxle 13 and the front axles 14 and 14. Further, when the propeller shaft 15 and the drive pinion shaft are coupled by the driving force transmission device 17 so as to be able to transmit torque, the driving force of the engine 12 causes the propeller shaft 15, the drive pinion shaft, the rear differential 18, and both the rear axles 19, 19. To the two rear wheels 20, 20. The front wheel 16 constitutes a driving wheel, and the rear wheel 20 constitutes a driven wheel.
[0018]
(Driving force transmission device)
The driving force transmission device 17 includes a wet-type multi-plate electromagnetic clutch mechanism 21. The electromagnetic clutch mechanism 21 has a plurality of clutch plates (not shown) that are frictionally engaged with or separated from each other. When a predetermined current is supplied to the electromagnetic coil 22 (see FIG. 2) built in the electromagnetic clutch mechanism 21, the clutch plates are frictionally engaged with each other, and between the front wheels 16, 16 and the rear wheels 20, 20. Torque (driving force) is transmitted. When the supply of current to the electromagnetic clutch mechanism 21 is cut off, the clutch plates are separated from each other, and the transmission of torque between the front wheels 16 and 16 and the rear wheels 20 and 20 is also cut off.
[0019]
The frictional engagement force of each clutch plate increases or decreases in accordance with the amount of current supplied to the electromagnetic coil 22 (current intensity). By controlling the amount of current supplied to the electromagnetic coil 22, the transmission torque between the front wheels 16, 16 and the rear wheels 20, 20, that is, the restraining force between the front wheels 16 and the rear wheels 20 can be arbitrarily adjusted. It has become. As the frictional engagement force of each clutch plate increases, the transmission torque between the front wheels 16, 16 and the rear wheels 20, 20 also increases. Conversely, when the frictional engagement force of each clutch plate decreases, the transmission torque between the front wheels 16 and 16 and the rear wheels 20 and 20 also decreases.
[0020]
Supply and interruption of current to the electromagnetic coil 22 and adjustment of the amount of current supply are controlled by an electronic control device for driving force distribution (hereinafter referred to as “driving force distribution control device 31 (4WD-ECU)”). That is, the driving force distribution control device 31 controls the friction engagement force of each clutch plate in the electromagnetic clutch mechanism 21 to select either the four-wheel driving state or the two-wheel driving state, and in the four-wheel driving state, the front wheel The driving force distribution ratio (driving force transmission ratio; torque distribution ratio) between the 16, 16 and the rear wheels 20, 20 is controlled.
[0021]
(Electrical configuration)
Next, the electrical configuration of the driving force distribution control device 31 of the four-wheel drive vehicle 11 will be described with reference to FIG.
[0022]
As shown in FIG. 2, the driving force distribution control device 31 of the four-wheel drive vehicle 11 includes a CPU (Central Processing Unit), a RAM (Write / Read Only Memory), a ROM (Read Only Memory) 32a, an input / output interface, and the like. And a microcomputer (hereinafter referred to as “microcomputer 32”). The ROM 32a constitutes storage means.
[0023]
The ROM 32a stores various control programs executed by the microcomputer 32, various data, various characteristic maps, and the like. Various characteristic maps are obtained in advance by experimental data based on vehicle models and well-known theoretical calculations. The RAM develops various control programs written in the ROM 32a, and a data work area for the CPU of the driving force distribution control device 31 to execute various arithmetic processes (for example, arithmetic processes for controlling energization of the electromagnetic coil 22). It is.
[0024]
The microcomputer 32 includes a wheel speed sensor 33, a throttle opening sensor 34 that constitutes an acceleration operation amount detection means, a relay 35, a current detection circuit 36, a drive circuit 37, and an engine control device (not shown). Abbreviation).
[0025]
The wheel speed sensors 33 are provided on the left and right front wheels 16 and 16 and the left and right rear wheels 20 and 20, respectively. The total four wheel speed sensors 33 are the wheel speeds (wheels of the front wheels 16 and 16 and the rear wheels 20 and 20). The number of rotations per unit time, that is, the rotation speed) is detected separately, and the detection results (wheel speed signals) are sent to the microcomputer 32.
[0026]
The throttle opening sensor 34 is connected to a throttle valve (not shown) of the engine 12, and detects the opening of the throttle valve (throttle opening θ), that is, the amount of depression of the driver's accelerator pedal (not shown). To do. The throttle opening θ is an acceleration operation amount indicating the driver's intention to move the four-wheel drive vehicle 11 forward or backward, and it is estimated that the driver is more eager to accelerate as the acceleration operation amount is larger. The throttle opening sensor 34 constitutes an acceleration operation amount detection means, and sends the detection result (depression operation amount signal) to the microcomputer 32.
[0027]
Further, the four-wheel drive vehicle 11 includes a battery 38, and a fuse 39, an ignition switch 40, a relay 35, a shunt resistor 41, an electromagnetic coil 22, and a field effect transistor (hereinafter referred to as “FET 42”) at both ends of the battery 38. ) Series circuit is connected.
[0028]
Both ends of the shunt resistor 41 are connected to the input side of the current detection circuit 36. The current detection circuit 36 detects the current flowing through the shunt resistor 41 based on the voltage across the shunt resistor 41 and sends it to the microcomputer 32. The microcomputer 32 calculates the current flowing through the electromagnetic coil 22 based on the current sent from the current detection circuit 36. A flywheel diode 43 is connected to both ends of the electromagnetic coil 22. The flywheel diode 43 is for releasing the counter electromotive force generated when the FET 42 is turned off, thereby protecting the FET 42. The gate G of the FET 42 is connected to the output side of the drive circuit 37, and the connection point between the source S of the FET 42 and the negative terminal of the battery 38 is grounded.
[0029]
When the ignition switch 40 is turned on (closed operation), electric power is supplied from the battery 38 to the microcomputer 32 via a power supply circuit (not shown). Then, the microcomputer 32 executes various control programs such as a driving force distribution control program on the basis of various information (detection signals) obtained from the wheel speed sensors 33 and the throttle opening sensor 34, and supplies them to the electromagnetic coil 22. The amount of current (command current value) is calculated.
[0030]
Then, the microcomputer 32 outputs the calculated command current value to the drive circuit 37. The drive circuit 37 performs on / off control (PWM control) of the FET 42 so that a current corresponding to the command current value is supplied to the electromagnetic coil 22. That is, the microcomputer 32 controls the amount of current supplied to the electromagnetic coil 22 to variably control the driving force distribution between the front wheel side and the rear wheel side.
[0031]
When the ignition switch 40 is turned off (opening operation), power supply to the microcomputer 32 is cut off.
(Operation of the embodiment)
Next, various functions of the microcomputer 32 executed in accordance with various control programs stored in the ROM 32a will be described based on the functional block diagram shown in FIG. Various parameters such as wheel speeds Vfl, Vfr, Vrl, Vrr, throttle opening θ, and differential rotational speed ΔN are used as meanings of signals corresponding thereto.
[0032]
The driving force distribution control in the microcomputer 32 is performed as follows. That is, the wheel speeds Vfl, Vfr, Vrl, and Vrr of the left and right front wheels 16 and 16 and the left and right rear wheels 20 and 20 detected by the wheel speed sensor 33 are expressed by a differential rotation speed calculation unit (hereinafter referred to as “ΔN calculation unit 50”). And the vehicle speed calculation unit 52.
[0033]
(ΔN calculation unit)
The ΔN calculation unit 50 obtains the front wheel average rotation speed Nfn (= (Vfl + Vfr) / 2) based on the wheel speeds Vfl and Vfr of the left and right front wheels 16 and 16, and both the wheel speeds Vrl of the left and right rear wheels 20 and 20. , Vrr is determined to determine the average rear wheel speed Nrn (= (Vrl + Vrr) / 2). Further, the ΔN calculation unit 50 calculates a differential rotation speed ΔN (= | Nfn−Nrn |) from the front wheel average rotation speed Nfn and the rear wheel average rotation speed Nrn. The ΔN calculation unit 50 sends the calculated differential rotation number ΔN to the differential rotation number torque calculation unit (hereinafter referred to as “ΔN torque calculation unit 54”) and the torque correction unit 55, respectively. This ΔN calculation unit 50 constitutes a differential rotation speed detection means.
[0034]
(Vehicle speed calculator)
The vehicle speed calculation unit 52 calculates the vehicle speed V based on the fetched wheel speeds Vfl, Vfr, Vrl, Vrr. The vehicle speed calculation unit 52 sends the calculated vehicle speed V to the pre-torque calculation unit 53, the ΔN torque calculation unit 54, and the torque correction unit 55, respectively. The vehicle speed calculation unit 52 constitutes vehicle speed detection means.
[0035]
(Pre-torque calculator)
In addition to the vehicle speed V from the vehicle speed calculation unit 52, the pre-torque calculation unit 53 receives the throttle opening θ from the throttle opening sensor 34. The pre-torque calculation unit 53 calculates a transmission torque (hereinafter referred to as “pre-torque T1”) according to the throttle opening θ and the vehicle speed V with reference to the pre-torque characteristic map. The pre-torque characteristic map shows changes in the pre-torque T1 with respect to an increase in the throttle opening θ for each predetermined vehicle speed range, and is stored in the ROM 32a in advance. The pre-torque calculation unit 53 sends the calculated pre-torque T1 to the adder 56.
[0036]
(ΔN torque calculator)
In addition to the vehicle speed V from the vehicle speed calculation unit 52 and the differential rotational speed ΔN from the ΔN calculation unit 50, the throttle opening θ detected by the throttle opening sensor 34 is input to the ΔN torque calculation unit 54. The ΔN torque calculation unit 54 refers to a transmission torque (hereinafter referred to as “ΔN torque T2”) corresponding to the vehicle speed V and the differential rotational speed ΔN as a differential rotational speed torque characteristic map (hereinafter referred to as “ΔN torque characteristic map”). ) To calculate. The ΔN torque characteristic map shows changes in ΔN torque T2 with respect to an increase in the differential rotational speed ΔN of the front and rear wheels for each predetermined vehicle speed range, and is stored in the ROM 32a in advance. The ΔN torque calculator 54 sends the calculated ΔN torque T2 to the adder 56.
[0037]
(Torque correction part)
In addition to the vehicle speed V from the vehicle speed calculation unit 52 and the differential rotational speed ΔN from the ΔN calculation unit 50, the torque correction unit 55 receives the throttle opening θ detected by the throttle opening sensor 34. The torque correction unit 55 constitutes torque correction means, which calculates a transmission torque (hereinafter referred to as “correction ΔN torque T3”) according to the throttle opening θ and the differential rotational speed ΔN, as well as the throttle opening θ and the vehicle speed. Based on V, it is determined whether or not the correction ΔN torque T3 is added to the pre-torque T1.
[0038]
That is, the torque correction unit 55 includes a correction differential rotation speed torque calculation unit (hereinafter referred to as “correction ΔN torque calculation unit 57”) and a torque correction necessity determination unit 58. The correction ΔN torque calculation unit 57 includes The throttle opening θ and the differential rotational speed ΔN are input, and the throttle opening θ and the vehicle speed V are input to the torque correction necessity determination unit 58.
[0039]
The corrected ΔN torque calculation unit 57 calculates the corrected ΔN torque T3 with reference to a corrected differential rotational speed torque characteristic map (hereinafter referred to as “corrected ΔN torque characteristic map”). The corrected ΔN torque characteristic map is obtained by adding the throttle opening θ further as a parameter to the change in the corrected ΔN torque T3 corresponding to the increase in the differential rotational speed ΔN of the front and rear wheels for each predetermined vehicle speed range. The correction ΔN torque T3 is set so as to increase as the dynamic rotational speed ΔN increases.
[0040]
Based on the throttle opening θ and the vehicle speed V, the torque correction necessity determination unit 58 determines whether or not it is necessary to add the correction ΔN torque T3 to the pre-torque T1, that is, whether or not torque correction is necessary. In this embodiment, when it is estimated that the traveling state of the four-wheel drive vehicle 11 is at the time of starting, the torque correction necessity determination unit 58 determines that torque correction is necessary, and adds the corrected ΔN torque T3 to the adder 56. send. When it is estimated that the traveling state of the four-wheel drive vehicle 11 is not at the time of starting, the torque correction necessity determination unit 58 determines that the torque correction is unnecessary and does not send the correction ΔN torque T3 to the adder 56.
[0041]
The torque correction necessity determination processing by the torque correction unit 55 (strictly speaking, the torque correction necessity determination unit 58) will be described in detail later. The correction ΔN torque T3 constitutes a correction driving force distribution amount, and the correction ΔN torque calculation unit 57 constitutes a correction amount calculation means. The torque correction necessity determination unit 58 constitutes a first comparison unit, a second comparison unit, and a traveling state determination unit.
[0042]
(Adder)
The adder 56 obtains a command torque T (T = T1 + T2) by adding the ΔN torque T2 sent from the ΔN torque calculator 54 to the pre-torque T1 sent from the pre-torque calculator 53. Further, when the correction ΔN torque T3 is sent from the torque correction unit 55, the adder 56 adds the ΔN torque T2 and the correction ΔN torque T3 to the pre-torque T1, thereby giving the command torque T (T = T1 + T2 + T3). Ask for. The adder 56 sends the calculated command torque T to the command current calculation unit 59.
[0043]
(Command current calculation part)
The command current calculation unit 59 calculates a current corresponding to the command torque T sent from the adder 56 (hereinafter referred to as “basic command current I0”) with reference to the basic command current characteristic map. The basic command current characteristic map is for converting the command torque T into the basic command current I0, and shows the change in the command torque T with respect to the change in the current supplied to the electromagnetic coil 22. The command current calculation unit 59 corrects the basic command current I0 based on a correction coefficient corresponding to the vehicle speed V, and sends the corrected basic command current I0 to the subtractor 60.
[0044]
(Subtractor)
In addition to the basic command current I0 from the command current calculator 59, the coil current Ic of the electromagnetic coil 22 detected by the current detection circuit 36 is input to the subtractor 60. The subtractor 60 sends a current deviation ΔI (ΔI = | I0−Ic |) between the basic command current I0 and the coil current Ic to the PI (proportional integration) control unit 61. The PI control unit 61 calculates a PI control value based on the current deviation ΔI sent from the subtractor 60, and sends this PI control value to the PWM (pulse width modulation) output conversion unit 62.
[0045]
(PWM output converter)
The PWM output conversion unit 62 performs a PWM calculation according to the PI control value that has been sent, and sends the result of the PWM calculation to the drive circuit 37. The drive circuit 37 supplies a predetermined current to the electromagnetic coil 22 of the electromagnetic clutch mechanism 21 based on the result of the PWM calculation sent from the PWM output conversion unit 62. Each clutch plate of the electromagnetic clutch mechanism 21 is frictionally engaged with an engagement force corresponding to the supplied current.
[0046]
As described above, the microcomputer 32 varies the basic command current I0 according to the differential rotational speed ΔN, the vehicle speed V, and the throttle opening θ (acceleration operation amount), that is, according to the traveling state of the vehicle (four-wheel drive vehicle 11). By controlling, the transmission torque between the front wheel 16 and the rear wheel 20 is optimally controlled.
[0047]
(Torque correction necessity determination process)
Next, torque correction necessity determination processing in the torque correction unit 55 of the microcomputer 32 will be described in detail according to the flowchart shown in FIG. This flowchart is executed based on a torque correction control program stored in advance in the ROM 32a. This torque correction control program is repeated every predetermined control cycle (sampling cycle). In the present embodiment, the step is abbreviated as “S”.
[0048]
As shown in FIG. 4, during the torque correction necessity determination process, the torque correction necessity determination unit 58 of the torque correction unit 55 performs the throttle opening detected by the vehicle speed V calculated by the vehicle speed calculation unit 52 and the throttle opening sensor 34. The degree θ is read (S101), and the process proceeds to S102.
[0049]
In S102, the torque correction necessity determination unit 58 determines whether or not the read vehicle speed V is smaller than a preset vehicle speed determination threshold value V0.
When it is determined that the vehicle speed V is greater than the preset vehicle speed determination threshold value V0 (NO in S102), the torque correction necessity determination unit 58 estimates that the four-wheel drive vehicle 11 is not at the start and does not require torque correction. If there is, the process ends. As a result, the command torque T becomes a value obtained by adding the ΔN torque T2 calculated by the ΔN torque calculation unit 54 to the pre-torque T1 calculated by the pre-torque calculation unit 53 (normal value; T = T1 + T2), and normal torque is not corrected. Torque distribution control is performed.
[0050]
When it is determined that the vehicle speed V is smaller than the preset vehicle speed determination threshold value V0 (YES in S102), the torque correction necessity determination unit 58 proceeds to S103.
In S103, the torque correction necessity determination unit 58 determines whether or not the read throttle opening θ is smaller than a preset throttle opening determination threshold θ0 (acceleration operation amount determination threshold).
[0051]
When it is determined that the throttle opening θ is larger than the preset throttle opening determination threshold θ0 (NO in S103), the torque correction necessity determination unit 58 estimates that the four-wheel drive vehicle 11 is not at the time of start and torque. The process ends with no correction required. As a result, the command torque T becomes a value obtained by adding the ΔN torque T2 calculated by the ΔN torque calculation unit 54 to the pre-torque T1 calculated by the pre-torque calculation unit 53 (normal value; T = T1 + T2), and normal torque is not corrected. Torque distribution control is performed.
[0052]
When it is determined that the throttle opening θ is smaller than the preset throttle opening determination threshold θ0 (YES in S103), the torque correction necessity determination unit 58 determines that the running state of the four-wheel drive vehicle 11 is a start time and torque Judge that correction is necessary. In general, the vehicle speed V and the throttle opening θ are extremely small during creep running or low acceleration operation when the four-wheel drive vehicle 11 is started, and thus the four-wheel drive vehicle 11 is controlled based on the vehicle speed V and the throttle opening θ. It can be estimated whether or not the driving vehicle 11 is starting. Then, the torque correction necessity determination unit 58 applies the correction ΔN torque characteristic map (S104), and sends the correction ΔN torque T3 calculated by the correction ΔN torque calculation unit 57 to the adder 56.
[0053]
As a result, the command torque T is a value obtained by adding the ΔN torque T2 and the corrected ΔN torque T3 to the pre-torque T1 (T = T1 + T2 + T3). The microcomputer 32 controls the frictional engagement force of the electromagnetic clutch mechanism 21 constituting the driving force transmission device 17 so that the command torque T is transmitted to the rear wheel 20 side. Since the correction ΔN torque T3 increases as the differential rotational speed ΔN increases, torque correction, that is, an increase in the torque distribution amount (driving force distribution amount) to the rear wheel 20 is performed according to the slip amount (idle amount). .
[0054]
Thus, when the vehicle speed V and the throttle opening θ are sufficiently small (“V <V0”, “θ <θ0”), if the differential rotational speed ΔN is generated, the four-wheel drive vehicle 11 This means that the front wheel 16 is slipping when starting, and a correction ΔN torque T3 corresponding to the differential rotation speed ΔN is added to the pre-torque T1.
[0055]
Therefore, the slip of the front wheels 16 (driving wheels) is suppressed (reduced) when starting (during creep travel or low acceleration travel) on an extremely low μ road such as an ice burn (road surface with a very small road friction coefficient). For example, during creep running or low acceleration running, the throttle opening θ and the engine torque transmitted to the front wheels 16 are very small values. However, if the front wheel 16 is on an extremely low μ road even with such a small torque at the time of starting, the front wheel 16 may slip. In the present embodiment, the amount of torque distribution to the rear wheel 20 side is increased in consideration of traveling on an extremely low μ road where the front wheel 16 slips even with such a small torque. Therefore, even if not only the front wheel 16 side but also the rear wheel 20 side is on the low μ road, the torque transmitted to the front wheel 16 is reduced by the amount of torque transmitted to the rear wheel 20 side. As a result, the slip of the front wheel 16 is suppressed.
[0056]
(Effect of embodiment)
Therefore, according to the present embodiment, the following effects can be obtained.
(1) When it is determined that the traveling state of the four-wheel drive vehicle 11 is a start time, the drive force transmission of the drive force transmission device 17 is performed so that the drive force distribution amount to the rear wheel 20 side becomes larger than the normal value. The ratio was controlled. That is, a correction ΔN torque T3 is added to the pre-torque T1 in addition to the ΔN torque T2. Therefore, idling (slip) of the front wheels 16 at the start can be suppressed. In addition, in the initial stage of the start, too much driving force distribution to the driven wheel side is avoided to avoid the occurrence of tight corner braking, and startability at low acceleration (that is, during low acceleration operation) is ensured. Is done.
[0057]
(2) When the vehicle speed V is smaller than the vehicle speed determination threshold value V0 and the throttle opening degree θ is smaller than the throttle opening degree determination threshold value θ0, it is determined that the traveling state of the four-wheel drive vehicle 11 is a start time. . For this reason, it is possible to accurately determine whether or not the four-wheel drive vehicle 11 is starting.
[0058]
(3) The correction ΔN torque T3 is obtained based on the differential rotation speed ΔN. That is, the correction ΔN torque T3 is obtained according to the slip amount of the front wheel 16. When the four-wheel drive vehicle 11 is started, the correction ΔN torque T3 is added to the normal value (T1 + T2). For this reason, a correction ΔN torque T3 that can avoid slipping of the front wheels 16 is added to the normal value. Accordingly, it is possible to avoid the torque distribution amount to the rear wheel 20 being insufficient or conversely excessive, and to ensure the running stability of the four-wheel drive vehicle 11 at the start.
[0059]
(4) A correction ΔN torque characteristic map for obtaining the correction ΔN torque T3 based on the differential rotational speed ΔN is stored in the ROM 32a in advance. When the four-wheel drive vehicle 11 is started, the correction ΔN torque T3 is obtained by referring to the correction ΔN torque characteristic map based on the differential rotation speed ΔN. Therefore, it is possible to obtain an appropriate correction ΔN torque T3 corresponding to the differential rotation speed ΔN (that is, the slip amount).
[0060]
(5) The correction ΔN torque T3 is added to the pre-torque T1 only when starting. For this reason, there is little influence on the control for avoiding the tight corner braking phenomenon.
[0061]
(Another example)
In addition, you may implement the said embodiment by changing into the following other examples.
In the present embodiment, the four-wheel drive vehicle 11 may be any type of automatic transmission vehicle (AT vehicle) and manual transmission vehicle (MT vehicle). In any type of four-wheel drive vehicle 11, slip of the front wheels 16 (drive wheels) at the time of start can be suppressed. However, in the case of MT cars, it is not considered during creep driving.
[0062]
In the present embodiment, the present invention is embodied in the driving force distribution control device 31 of the four-wheel drive vehicle 11 that includes the engine 12 (internal combustion engine) as a power source. However, the engine 12 and the motor (not shown) You may make it materialize in the driving force distribution control apparatus of the parallel type hybrid vehicle provided with the motive power source. This parallel system is a system in which wheels are driven by both the engine 12 and the motor. The driving force for the hybrid vehicle to travel is mainly supplied from the engine 12. The motor is driven at the time of start or acceleration when a load is applied to the engine 12, and the driving force of the engine 12 is assisted by the driving force of the motor. Even if it does in this way, the effect similar to this embodiment can be acquired.
[0063]
In the present embodiment, the present invention is embodied in the driving force distribution control device 31 of the four-wheel drive vehicle 11 that includes the engine 12 (internal combustion engine) as a power source. However, the engine 12 and the motor (not shown) You may make it materialize in the driving force distribution control apparatus of the series system hybrid vehicle provided with the motive power source. This series system is a system in which the wheels are driven only by the driving force of the driving motor. The driving force of the engine 12 is used only to drive a generator (not shown). The AC power generated by the generator is converted to DC power by an inverter (not shown) and charged to a battery (not shown). The DC power from this battery is converted to AC power by the inverter and supplied to the motor. In this series-type four-wheel drive vehicle, when accelerating, for example, the operation amount of the operation pedal is increased. As a result, the amount of DC power supplied to the motor increases. That is, the amount of DC power supplied to the motor is increased or decreased by increasing or decreasing the operation amount of the operation pedal. The operation amount of the operation bedal indicates an acceleration operation amount indicating the driver's willingness to accelerate. Even if it does in this way, the effect similar to this embodiment can be acquired. However, the throttle opening θ (acceleration operation amount) in the present embodiment is read as the operation amount of the operation bed that adjusts the increase or decrease in the amount of DC power supplied to the motor.
In the present embodiment, the present invention is embodied in the driving force distribution control device 31 of the four-wheel drive vehicle 11 provided with the engine 12 (internal combustion engine) as a power source. However, the electric power that drives the wheels only by the driving force of the motor. You may make it materialize in a motor vehicle. In this electric vehicle, for example, the amount of DC power supplied to the motor is increased or decreased by increasing or decreasing the operation amount of the operation pedal. Even if it does in this way, the effect similar to this embodiment can be acquired. However, the throttle opening θ (acceleration operation amount) in the present embodiment is read as the operation amount of the operation bed that adjusts the increase or decrease in the amount of DC power supplied to the motor.
[0064]
In the present embodiment, the present invention is embodied in the driving force distribution control device 31 of the four-wheel drive vehicle 11 based on the front wheel drive, but is specifically applied to the drive force distribution control device 31 of the four-wheel drive vehicle 11 based on the rear wheel drive base. You may make it make it. In this case, the driving force distribution control device 31 controls the amount of torque distribution to the front wheel 16 side.
[0065]
(Appendix)
Next, a technical idea that can be grasped from the embodiment and another example will be added below.
The driving force toward the driven wheel by variably controlling the driving force transmission rate of the driving force transmission device based on the vehicle speed obtained by the vehicle speed detecting means and the acceleration operation amount obtained by the acceleration operation amount detecting means In the driving force distribution control method for a four-wheel drive vehicle in which the distribution amount is variably controlled, it is determined whether or not the vehicle is in a starting state and the vehicle is in a starting state. A driving force distribution control method for a four-wheel drive vehicle in which the driving force transmission ratio of the driving force transmission device is controlled so that the driving force distribution amount to the driven wheel side is larger than the normal value.
[0066]
【The invention's effect】
According to the present invention, since the driving force distribution amount to the driven wheel side is made larger than the normal value at the time of starting, it is possible to suppress idling of the driving wheel at the time of starting.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle in the present embodiment.
FIG. 2 is a circuit diagram showing an electrical configuration of a driving force distribution control device according to the present embodiment.
FIG. 3 is a functional block diagram of a microcomputer according to the present embodiment.
FIG. 4 is a flowchart showing torque correction necessity determination processing in the present embodiment.
[Explanation of symbols]
11 ... Four-wheel drive vehicle constituting the vehicle,
17 ... Driving force transmission device,
20 ... the rear wheel constituting the driven wheel,
31 ... Driving force distribution control device,
32a ... ROM 32a constituting storage means,
34. Throttle opening sensor constituting acceleration operation amount detection means,
52... A vehicle speed calculation unit constituting vehicle speed detection means,
57... Correction ΔN torque calculation unit constituting correction amount calculation means,
58... Torque correction necessity determination unit constituting the first comparison unit, the second comparison unit, and the traveling state determination unit,
V ... Vehicle speed,
V0: vehicle speed judgment threshold,
ΔN: Differential rotation speed,
θ: throttle opening that constitutes the acceleration operation amount,
θ0 is a throttle opening degree determination threshold value that constitutes an acceleration operation amount determination threshold value.

Claims (3)

Based on the vehicle speed obtained by the vehicle speed detection means, the acceleration operation amount obtained by the acceleration operation amount detection means, and the differential rotation speed between the driving wheel and the driven wheel obtained by the differential rotation speed detection means , In the drive force distribution control device for a four-wheel drive vehicle in which the drive force distribution amount to the driven wheel is variably controlled by variably controlling the drive force transmission ratio of the drive force transmission device.
A correction amount computing means for running state of the vehicle calculates the correction driving force distribution amount based on the acceleration operating amount and the differential speed and determines the traveling state determining means for determining whether or not a time of start, the travel When it is determined by the state determination means that the vehicle is starting , the driving force on the driven wheel side than the normal value of the driving force distribution amount obtained based on the vehicle speed, the acceleration operation amount, and the differential rotation speed the correction driving force of the four-wheel-drive vehicle that controls the driving force transmission ratio of the distribution amount of the addition to the driving force transmitting device driving force distribution control apparatus to the normal value so that the amount of allocation increases. The travel state determination means includes first comparison means for comparing the vehicle speed with a preset vehicle speed determination threshold value, and second comparison means for comparing the acceleration operation amount with a preset acceleration operation amount determination threshold value. Prepared,
The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein it is determined whether or not the vehicle is starting based on a comparison result between the first comparison means and the second comparison means. A characteristic map for obtaining a corrected driving force distribution amount based on the acceleration operation amount and the differential rotation speed is stored in a storage unit in advance, and when the traveling state determination unit determines that the vehicle is starting, 3. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the correction amount calculating means obtains a corrected driving force distribution amount based on a characteristic map stored in the storage means .

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