JP2005096565A - Driving force distribution control device for four-wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving force distribution control device for a four-wheel drive vehicle suppressing racing of a driving wheel at rapid starting and realizing rapid starting intended by a driver. <P>SOLUTION: A torque correction requirement determination part 58 determines whether or not the four-wheel drive vehicle is in the rapid starting preparation state. When it is determined that the four-wheel drive vehicle is in the rapid starting preparation state, a micro-computer controls a distribution amount of driving force toward a direction that the distribution amount of driving force to a front wheel side and a rear wheel side becomes equal (that is, so as to strengthen tightening force in a solenoid clutch mechanism 21). That is, correction ΔN torque T3 is added to a pre-torque T1 in addition to ΔN torque T2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a driving force distribution control device for a four-wheel drive vehicle.

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. A driving force distribution control device for a four-wheel drive vehicle that is variably controlled is known (see, for example, Patent Documents 1, 2, and 3). Specifically, a 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 vehicle is transmitted so that this torque is transmitted to the front wheel side or the rear wheel side. The 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.
JP-A-5-338459 JP-A-5-238280 JP-A-9-136554

  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”), the driver intends to start suddenly, the gear stage is in the N range (neutral), and the engine speed is increased, the D range (drive), etc. When the vehicle is switched to this travel range, excessive torque is applied to the drive wheels (or front wheels in the case of an FF-based four-wheel drive vehicle) when starting. For this reason, the driving force applied to the drive wheels exceeds the frictional force with the road surface, causing the vehicle to become unstable as well as not being able to start suddenly as intended by the driver. In a manual transmission vehicle (hereinafter referred to as “MT vehicle”), the same problem occurs when the clutch is suddenly engaged from a state where the engine speed is increased.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to suppress the idling of the drive wheels at the time of a sudden start and enable a sudden start intended by the driver. A driving force distribution control device is provided.

  According to the first aspect of the present invention, the amount of driving force distribution to the front wheel side and the rear wheel side is variable 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. The driving force distribution control device for a four-wheel drive vehicle to be controlled includes a starting state determining means for determining (predicting) a starting state of the vehicle, and the vehicle speed detected by the vehicle speed detecting means is preset. When the acceleration operation amount detected by the acceleration operation amount detection means is less than a vehicle speed determination threshold and is greater than or equal to a preset acceleration operation amount determination threshold, the start state determination means determines that it is a sudden start preparation state, The gist of the invention is that when the sudden start preparation state is determined, the driving force distribution amount is controlled in a direction in which the driving force distribution amounts to the front wheel side and the rear wheel side become equal.

  According to a second aspect of the present invention, in the first aspect of the invention, the engine speed detecting means for detecting the engine speed is the acceleration operation amount detecting means, the engine speed is the acceleration operation amount, and the engine speed is The engine speed detected by the engine speed detection means after the start state determination means determines that the sudden start preparation state is set to be greater than the engine speed determination threshold. When the sub engine speed determination threshold value is less than the small value, the start state determination means determines that the start state is a sudden start state, and when the determination of the sudden start state is made, until a predetermined time elapses thereafter, The gist is that the driving force distribution amount is controlled in a direction in which the driving force distribution amount to the front wheel side and the rear wheel side becomes equal.

  According to a third aspect of the present invention, in the invention according to the second aspect, the engine speed detected by the engine speed detecting means after the start state determining means determines that it is in the sudden start preparation state is the engine speed. When the time that is less than the rotation speed determination threshold value and equal to or greater than the auxiliary engine rotation speed determination threshold value continues for a preset time determination threshold value, the drive force distribution amount to the front wheel side and the rear wheel side is directed to be equal. The gist is that the state of controlling the amount of distribution of driving force is released.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, when the start state determination means determines that the sudden start preparation state or the sudden start state, driving to the front wheel side and the rear wheel side is performed. The gist is to distribute the power distribution evenly.

(Function)
In the first aspect of the invention, the fact that the amount of driving force distribution to the front wheel side and the rear wheel side is equal means that the driving force distribution ratio for the front wheel side and the rear wheel side is 50:50. When the driving force distribution ratio for the front wheel side and the rear wheel side is 100: 0, or when the driving force distribution ratio for the front wheel side and the rear wheel side is 0: 100, only one of the front wheels and the rear wheels is driven. 2 wheel drive mode.

  Controlling the driving force distribution amount in the direction in which the driving force distribution amount to the front wheel side and the rear wheel side becomes equal means that the driving force distribution ratio for the front wheel side and the rear wheel side is 50:50. It is to control the amount of power distribution.

  When the detected vehicle speed is less than the vehicle speed determination threshold value and the detected acceleration operation amount is greater than or equal to the acceleration operation amount determination threshold value, it is determined that there is a sudden start preparation state. Therefore, sudden start from a state in which the vehicle is stopped or moving forward or backward at a slow speed is predicted in advance, and the driving force distribution is directed in the direction in which the driving force distribution amount to the front wheel side and the rear wheel side becomes equal. The amount can be controlled. That is, for example, when starting normally, the driving force is distributed only to the driving wheels (one of the front wheels or the rear wheels) to start with good fuel efficiency, and when starting quickly, the driven wheels (the other of the front wheels or the rear wheels) In addition, by distributing the driving force, it is possible to suppress idling and perform a stable sudden start. As the vehicle speed determination threshold, for example, about 10 km / h is desirable.

  The acceleration operation amount includes an engine speed, a throttle opening, and the like, and the acceleration operation amount detection means includes an engine rotation sensor, a throttle opening sensor, and the like. When the engine speed is used as the acceleration operation amount, it is desirable that the acceleration operation amount determination threshold (engine rotation speed determination threshold) is the minimum engine rotation speed when the driver is about to start suddenly. For example, in a general passenger car, it is desirable that the engine speed determination threshold value be about 3000 rpm. At lower speeds, the drive wheels are less likely to run idle during start-up even during normal start-up, and there is also a risk of misrecognizing a high-speed state due to idling up after engine startup at low temperatures. It is.

Appropriate values may be adopted for the vehicle speed determination threshold value and the acceleration operation amount determination threshold value depending on the type of vehicle, the exhaust amount, and the like.
According to the second aspect of the present invention, if the detected engine speed is less than the sub engine speed determination threshold after the determination of the sudden start preparation state is made, the determination of the sudden start state is made. Is made. After that, until the predetermined time elapses, the state in which the driving force distribution amount is controlled in the direction in which the driving force distribution amount to the front wheels and the rear wheels becomes equal is maintained, so that idling during sudden start can be suppressed. . For example, when the gear speed of an AT car is shifted from the N range to a driving range such as the D range with the engine speed increased, or when the clutch of the MT car is suddenly engaged with the engine speed increased. The engine speed temporarily decreases due to an increase in engine load. It is considered that the engine is in a sudden start state for a while after the engine speed is temporarily reduced, and the idling during the sudden start can be suppressed by controlling the driving force distribution amount according to this situation.

  Note that the value of the sub engine speed determination threshold value may be an engine speed that temporarily decreases when the engine starts suddenly while the engine is rotating at the engine speed determination threshold value. The sub engine speed determination threshold value is preferably a value lower by about 500 to 1000 rpm, for example, than the engine speed determination threshold value. Specifically, when the engine speed determination threshold is set to 3000 rpm, the sub engine speed determination threshold is preferably 2000 to 2500 rpm.

  According to the third aspect of the present invention, after the determination of the sudden start preparation state is made, the time during which the detected engine speed is less than the engine speed determination threshold and greater than or equal to the sub engine speed determination threshold is set in advance. If it continues for the time determination threshold or more, the state in which the driving force distribution amount is controlled in the direction in which the driving force distribution amounts to the front wheel side and the rear wheel side become equal is released. Therefore, the engine speed has decreased due to a sudden start operation (shift from N range to D range at high engine speed or sudden clutch operation), or the driver has released the accelerator pedal. It can be determined whether or not the engine speed has decreased. When a sudden start operation is performed, the engine speed decreases from the engine speed determination threshold value to less than the sub engine speed determination threshold value in a short time due to a rapid increase in the engine load. When the engine speed decreases due to the loosening of the engine, etc., the engine speed gradually decreases due to the inertia of the rotating part of the engine. Based on this difference, it is possible to determine whether or not a sudden start operation has been performed. Accordingly, the sudden start state can be accurately detected. When the engine speed decreases due to the driver loosening the accelerator pedal or the like, there is a state in which the driving force distribution amount is controlled in a direction in which the driving force distribution amount to the front wheel side and the rear wheel side becomes equal. Canceled.

  Note that the time threshold determination threshold value should be a value suitable for the above-described determination, and should be determined according to engine characteristics and drive system characteristics. In a general passenger car, it is desirable to set the time determination threshold to about 0.5 to 1 second.

  According to the fourth aspect of the present invention, it is possible to start without idling using both the traction (the force with which the wheel grips the road surface) of the front wheel and the rear wheel.

  The present invention has an excellent effect of suppressing idling of the drive wheels during sudden start and enabling sudden start intended by the driver.

A first 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 below with reference to FIGS.
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.

  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 is a driving wheel, and the rear wheel 20 is a driven wheel.

  The driving force transmission device 17 includes a wet multi-plate electromagnetic clutch mechanism 21, and 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 an electromagnetic coil 22 (see FIG. 2) built in the electromagnetic clutch mechanism 21, the clutch plates are frictionally engaged with each other, and torque (driving force) is transmitted to the rear wheels 20, 20. Is done. 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 to the rear wheels 20 and 20 is cut off.

  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 to the rear wheels 20, 20, that is, the restraining force on the rear wheel 20 (friction engagement force in the electromagnetic clutch mechanism 21) can be arbitrarily adjusted. . When the frictional engagement force of each clutch plate increases, the transmission torque to the rear wheels 20, 20 increases. Conversely, when the frictional engagement force of each clutch plate decreases, the transmission torque to the rear wheels 20, 20 decreases. That is, if the frictional engagement force of each clutch plate is increased and the current supply amount to the electromagnetic coil 22 is controlled in the direction in which the propeller shaft 15 and the drive pinion shaft are directly connected, the driving force distribution to the front wheel side and the rear wheel side is achieved. The amount is controlled in the same direction.

The supply and interruption of current to the electromagnetic coil 22 and adjustment of the current supply amount are referred to as 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.

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.
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 is a storage means.

  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.

  In the microcomputer 32, a wheel speed sensor 33, an engine speed sensor 34 as an engine speed detection means, a relay 35, a current detection circuit 36, a drive circuit 37, and an engine control device (not shown) are respectively input / output interfaces (not shown). ) Is connected through.

  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.

The engine speed sensor 34 detects the speed N of the engine 12. The engine speed N is sent to the microcomputer 32.
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.

  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.

  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 engine speed sensor 34 and supplies them to the electromagnetic coil 22. The amount of current (command current value) is calculated.

  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.

When the ignition switch 40 is turned off (opening operation), power supply to the microcomputer 32 is cut off.
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, engine speed N, and differential speed ΔN are used as meanings of corresponding signals.

  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.

  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 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.

  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.

  Information on the engine speed N detected by the engine speed sensor 34 is sent to the pre-torque calculator 53 and the ΔN torque calculator 54. Information on the engine speed N detected by the engine speed sensor 34 is sent to a correction ΔN torque calculation unit 57 and a torque correction necessity determination unit 58.

  The pre-torque calculation unit 53 receives the vehicle speed V from the vehicle speed calculation unit 52 and the engine speed N from the engine speed sensor 34. The pre-torque calculation unit 53 calculates a pre-torque T1 corresponding to the engine speed N and the vehicle speed V with reference to the pre-torque characteristic map M (N, V). The pre-torque characteristic map M (N, V) indicates the pre-torque T1 with the engine speed and the vehicle speed as variables, 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.

  The ΔN torque calculator 54 receives the vehicle speed V from the vehicle speed calculator 52, the differential rotation speed ΔN from the ΔN calculator 50, and the engine speed N detected by the engine speed sensor 34. The ΔN torque calculator 54 calculates a ΔN torque T2 corresponding to the vehicle speed V, the engine speed N, and the differential speed ΔN with reference to the ΔN torque characteristic map M (ΔN, N, V). The ΔN torque characteristic map M (ΔN, N, V) shows ΔN torque T2 with the differential rotation speed, the engine rotation speed, and the vehicle speed as variables, and is stored in the ROM 32a in advance. The ΔN torque calculator 54 sends the calculated ΔN torque T2 to the adder 56.

The engine speed N and the differential speed ΔN are input to the correction ΔN torque calculation unit 57, and the engine speed N and the vehicle speed V are input to the torque correction necessity determination unit 58.
The correction ΔN torque calculator 57 calculates a correction ΔN torque T3 with reference to the correction ΔN torque characteristic map M (ΔN, N). The corrected ΔN torque characteristic map M (ΔN, N) is a map that shows torque with the differential rotational speed ΔN of the front and rear wheels and the engine rotational speed N as variables. The correction ΔN torque T3 is set so as to increase as the differential rotational speed ΔN increases.

  The torque correction necessity determination unit 58 determines whether or not the correction ΔN torque T3 needs to be added to the pre-torque T1 based on the engine speed N and the vehicle speed V, that is, whether torque correction is necessary. When it is determined that torque correction is necessary, the torque correction necessity determination unit 58 causes the correction ΔN torque calculation unit 57 to calculate the correction ΔN torque T3 and sends the calculated correction ΔN torque T3 to the adder 56. . The torque correction necessity determination unit 58 does not send the correction ΔN torque T3 to the adder 56 when determining that the torque correction is unnecessary.

  The adder 56 obtains the 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 necessity determination unit 58, the adder 56 adds the ΔN torque T2 and the correction ΔN torque T3 to the pre-torque T1, respectively, so that the command torque T ( T = T1 + T2 + T3) is obtained. The adder 56 sends the calculated command torque T to the command current calculation unit 59.

  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 Io”) 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 Io, 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 Io based on a correction coefficient corresponding to the vehicle speed V, and sends the corrected basic command current Io to the subtractor 60.

  In addition to the basic command current Io from the command current calculation unit 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 = | Io−Ic |) between the basic command current Io 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.

  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.

  As described above, the microcomputer 32 can change the basic command current Io according to the differential rotation speed ΔN, the vehicle speed V, and the engine rotation speed N (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.

  4 to 6 show flowcharts executed by the microcomputer 32 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). The torque correction control will be described below based on the flowcharts shown in FIGS.

  The torque correction necessity determination unit 58 reads the detected vehicle speed V and the detected engine speed N (step S1). After reading the vehicle speed V and the engine speed N, the torque correction necessity determination unit 58 determines whether or not a “sudden start determination” described later is stored (step S2). When [sudden start determination] is not stored (NO in step S2), the torque correction necessity determination unit 58 compares the detected vehicle speed V with a preset vehicle speed determination threshold V1 (step S3). ). The vehicle speed determination threshold value V1 is set to 10 km / h, for example.

  When the detected vehicle speed V is less than the vehicle speed determination threshold value V1 (YES in step S3), the torque correction necessity determination unit 58 determines whether the detected engine speed N and a preset engine speed determination threshold value N1. A size comparison is performed (step S4). The engine speed determination threshold N1 is set to a value (for example, 3000 rpm) that is considerably larger than the idling speed.

  When the detected engine speed N is equal to or greater than the engine speed determination threshold N1 (YES in step S4), the torque correction necessity determination unit 58 determines that N ≧ N1 (hereinafter referred to as [N ≧ N1]). Is stored, and a first timekeeping value to be described later is cleared (step S5). Then, the torque correction necessity determination unit 58 sends the correction ΔN torque T3 calculated by the correction ΔN torque calculation unit 57 to the adder 56. That is, the torque correction necessity determination unit 58 determines that the four-wheel drive vehicle 11 is in a sudden start preparation state, and calculates the correction ΔN torque T3 using the correction ΔN torque characteristic map M (ΔN, N). The correction ΔN torque calculation unit 57 performs the calculation, and sends the calculated correction ΔN torque T3 to the adder 56. Thus, the command torque T becomes a value obtained by adding the ΔN torque T2 and the correction ΔN torque T3 to the pre-torque T1 (T = T1 + T2 + T3). The correction ΔN torque T3 is a correction driving force distribution amount.

  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. That is, the microcomputer 32 determines that the four-wheel drive vehicle 11 is in a ready-for-start state and performs a quick start control (step S6).

After the process of step S6, the microcomputer 32 proceeds to step S1 of the next control cycle.
When the detected vehicle speed V is equal to or higher than the vehicle speed determination threshold value V1 (NO in step S3), the torque correction necessity determination unit 58 clears the storage of the determination result [N ≧ N1] and also performs a first timekeeping described later. The value is cleared (step S7). Then, the torque correction necessity determination unit 58 does not send the correction ΔN torque T3 to the adder 56. Thereby, the command torque T becomes a value (T = T1 + T2) obtained by adding the ΔN torque T2 to the pre-torque T1. 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. That is, the microcomputer 32 performs normal control (step S7).

After the process of step S7, the microcomputer 32 proceeds to step S1 of the next control cycle.
When the detected engine speed N is less than the engine speed determination threshold value N1 (NO in step S4), the torque correction necessity determination unit 58 determines the determination result [N ≧ N1] (that is, the sudden start preparation state). Is determined) (step S8). When the determination result [N ≧ N1] is stored (YES in step S8), the torque correction necessity determination unit 58 determines the magnitude of the detected engine speed N and a preset engine speed determination threshold N2. Comparison is performed (step S9). The engine speed determination threshold N2 is set to a value (for example, 2500 rpm) that is larger than the idling speed and smaller than the engine speed determination threshold N1.

  When the engine speed N is less than the engine speed determination threshold value N2 as the sub acceleration operation amount determination threshold value (YES in step S9), the torque correction necessity determination unit 58 indicates that the four-wheel drive vehicle 11 is in a sudden start state. Make a decision. The torque correction necessity determination unit 58 stores the determination result (represented as [abrupt start determination]) and clears the storage of the first time measurement value and the determination result [N ≧ N1] (step S10). Then, the microcomputer 32 performs sudden start control (step S6), and proceeds to step S1 of the next control cycle.

  When engine speed N is equal to or higher than engine speed determination threshold N2 (NO in step S9), torque correction necessity determination unit 58 determines that four-wheel drive vehicle 11 is not in a sudden start state. Then, the torque correction necessity determination unit 58 counts up the first time measurement value (step S11). The first timekeeping value is a time value that is counted and accumulated in units of control cycles. After the process of step S11, the torque correction necessity determination unit 58 compares the first time-measured value with a preset first time determination threshold t1 (step S12). If the first time measurement value is less than the first time determination threshold value t1 (YES in step S12), the microcomputer 32 performs the sudden start control (step S6). Then, the microcomputer 32 proceeds to step S1 of the next control cycle.

  When the first time measurement value is equal to or greater than the first time determination threshold value t1 (NO in step S12), the torque correction necessity determination unit 58 clears the storage of the determination result [N ≧ N1] and first The measured time value is cleared (step S14). Then, the torque correction necessity determination unit 58 performs normal control (step S7). That is, the microcomputer 32 shifts from the sudden start control in which the correction ΔN torque T3 is sent to the adder 56 to the normal control in which the correction ΔN torque T3 is not sent to the adder 56. The process repeated in the order of steps S1 to S4, S8, S9, S11, S12, and S6 is a process of continuing the sudden start control performed in the process order of steps S12 and S6 over the first time determination threshold value t1.

After the process of step S7, the microcomputer 32 proceeds to step S1 of the next control cycle.
If the torque correction necessity determination unit 58 does not store the determination result [N ≧ N1] in step S8 (NO in step S8), the torque correction necessity determination unit 58 clears the first timekeeping value ( Step S13). Then, the torque correction necessity determination unit 58 performs normal control (step S13). That is, the microcomputer 32 shifts from the sudden start control in which the correction ΔN torque T3 is sent to the adder 56 to the normal control in which the correction ΔN torque T3 is not sent to the adder 56.

After the process of step S13, the microcomputer 32 proceeds to step S1 of the next control cycle.
When [Sudden start determination] is stored in step S2 (YES in step S2), the torque correction necessity determination unit 58 sets the second time measurement value and a preset second time determination threshold value t2. A size comparison is performed (step S14). When the second time measurement value is less than the second time determination threshold t2 (YES in step S14), torque correction necessity determination unit 58 counts up the second time measurement value (step S15). The second time measurement value is a time value that is counted and accumulated in units of control cycles.

After the process of step S15, the microcomputer 32 proceeds to step S1 of the next control cycle.
When the second time measurement value is less than the second time determination threshold value t2 in step S14 (YES in step S14), the torque correction necessity determination unit 58 counts up the second time measurement value. That is, the process repeated in the order of steps S1, S2, S14, and S15 is a process of continuing the sudden start control performed in steps S10 and S6 over the second time determination threshold value t2.

  When the second time measurement value is equal to or greater than the second time determination threshold value t2 (NO in step S14), the torque correction necessity determination unit 58 clears the second time measurement value and stores [sudden start determination]. Is cleared (step S16). Then, the torque correction necessity determination unit 58 performs normal control (step S16). That is, the microcomputer 32 shifts from the sudden start control in which the correction ΔN torque T3 is sent to the adder 56 to the normal control in which the correction ΔN torque T3 is not sent to the adder 56.

After the process of step S16, the microcomputer 32 proceeds to step S1 of the next control cycle.
The torque correction necessity determination unit 58 is a start state determination unit that determines whether or not the vehicle is in a sudden start preparation state. When it is determined that the vehicle is not ready for sudden start, the microcomputer 32 controls the driving force transmission rate of the driving force transmission device using the normal driving force distribution amount. When the microcomputer 32 determines that the vehicle is ready for sudden start, the microcomputer 32 controls the driving force transmission rate of the driving force transmission device so that the amount of driving force distribution to the driven wheels is larger than the normal value. .

In the first embodiment, the following effects can be obtained.
(1-1) In the present embodiment, if the detected vehicle speed V is less than the vehicle speed determination threshold value V1 and the detected engine speed N is equal to or greater than the engine speed determination threshold value N1, whether or not torque correction is necessary The determination unit 58 determines that the four-wheel drive vehicle 11 is in a sudden start preparation state. In this case, a small vehicle speed determination threshold value V1 is adopted as the vehicle speed determination threshold value V1. That is, the vehicle speed of the four-wheel drive vehicle 11 traveling at the vehicle speed determination threshold value V1 is extremely low. Further, as the engine speed determination threshold value N1, a large engine speed determination threshold value is employed so that the engine speed is considerably larger than the idling speed.

  The state in which the vehicle speed V is less than the vehicle speed determination threshold value V1 and the engine speed N is equal to or greater than the engine speed determination threshold value N1 is, for example, when the accelerator pedal is depressed in the neutral state and the engine speed N is set to the engine speed determination threshold value N1. This corresponds to starting from the above state. Such a start is a sudden start, and slip is likely to occur between the drive wheel and the road surface.

  The detected vehicle speed V being less than the vehicle speed determination threshold value V1 includes the case where the detected vehicle speed V is zero (that is, the state where the four-wheel drive vehicle 11 is stopped). In the present embodiment, when the engine speed is set to the engine speed determination threshold value N1 or more while the four-wheel drive vehicle 11 is stopped, it is determined that the four-wheel drive vehicle 11 is in a sudden start. In other words, when the four-wheel drive vehicle 11 is stopped and the engine speed is set to the engine speed determination threshold value N1 or more, it is predicted that the four-wheel drive vehicle 11 will start suddenly. It takes place before 11 starts. Such a sudden start determination based on prediction is advantageous in properly performing slip suppression.

  In this embodiment, when it is grasped that the vehicle speed V is less than the vehicle speed determination threshold value V1 and the engine speed N is equal to or higher than the engine speed determination threshold value N1, the sudden start of sending the correction ΔN torque T3 to the adder 56. Control is performed. Therefore, the driving force distribution amount to the driven wheel side becomes larger than the normal value (T = T1 + T2), and the slip between the driving wheel and the road surface is suppressed.

  (1-2) The situation in which the detected vehicle speed V is smaller than the vehicle speed determination threshold value V1 having a small value and the detected engine speed N is greater than or equal to the engine speed determination threshold value N1 having a considerably large value is a sudden start preparation. The state is accurately reflected. Therefore, in the present embodiment in which it is determined that the vehicle is ready for sudden start when V <V1 and N ≧ N1, the sudden start prediction determination is accurately performed.

  (1-3) In this embodiment, when V <V1 in the current control cycle, N ≧ N1 in the previous control cycle, and N <N2 in the current control cycle, the vehicle is in a sudden start state. Is determined. This determination assumes a situation in which the engine speed rapidly decreases due to sudden start of the four-wheel drive vehicle 11. This situation accurately reflects the sudden start state. Therefore, in this embodiment in which it is determined that the vehicle is suddenly started when V <V1 in the current control cycle, N ≧ N1 in the previous control cycle, and N <N2 in the current control cycle. Start determination is performed accurately.

  (1-4) After the determination of the sudden start preparation state is made, when the detected engine speed N becomes less than the sub engine speed determination threshold N2, the determination of the sudden start state is made. Thereafter, until the time (predetermined time) indicated by the second time determination threshold t2 has elapsed, the driving force distribution amount is controlled in a direction in which the driving force distribution amounts to the front wheels 16 and the rear wheels 20 become equal. Since it is continued, idling during sudden start can be suppressed. For example, when the gear of an AT car is shifted from a N range to a driving range such as a D range while the engine speed is high, or when the clutch of an MT car is suddenly connected while the engine speed is high. The engine speed temporarily decreases due to an increase in the load on the engine 12. It is considered that the engine is suddenly started for a while after the engine speed is temporarily reduced, and by controlling the driving force distribution amount according to this situation, idling during the sudden start can be suppressed.

  (1-5) First time determination when the detected engine speed N is less than the engine speed determination threshold value N1 and greater than or equal to the auxiliary engine speed determination threshold value N2 after the determination of the sudden start preparation state is made When the threshold value t1 or more continues, the state in which the driving force distribution amount is controlled in the direction in which the driving force distribution amount to the front wheel 16 side and the rear wheel 20 side becomes equal is released. Therefore, the engine speed has decreased due to a sudden start operation (shift from N range to D range at high engine speed or sudden clutch operation), or the driver has released the accelerator pedal. It can be determined whether or not the engine speed has decreased. When a sudden start operation is performed, the engine speed N decreases from the engine speed determination threshold value N1 to less than the sub engine speed determination threshold value N2 in a short time due to a rapid increase in the load of the engine 12, In the case where the engine speed decreases due to the user loosening the accelerator pedal or the like, the engine speed N gradually decreases due to the inertia of the rotating portion of the engine 12. In the present embodiment, it is determined whether or not a sudden start operation has been performed based on this difference. Accordingly, the sudden start state can be accurately detected.

Next, a second embodiment of FIG. 7 will be described. The same reference numerals are used for the same components as those in the first embodiment.
In the second embodiment, the correction ΔN torque calculation unit 57 and the torque correction necessity determination unit 58 in the first embodiment are eliminated, and a start determination unit 64 and a torque are used instead of the pre-torque calculation unit 53 in the first embodiment. A microcomputer 32 </ b> B including the calculation unit 65 is configured. The start determination unit 64 has the same function as the torque correction necessity determination unit 58 in the first embodiment, and performs a sudden start determination similar to the sudden start determination shown in the flowcharts of FIGS. That is, the start determination unit 64 is a start state determination unit.

  When it is determined that the vehicle is not ready for sudden start, the start determination unit 64 causes the torque calculation unit 65 to calculate the pre-torque T1. The torque calculator 65 calculates a pre-torque corresponding to the detected engine speed N and the detected vehicle speed V with reference to the torque characteristic map. The torque characteristic map shows the pre-torque with the engine speed and the vehicle speed as variables, and is stored in the ROM 32a in advance. The torque calculator 65 sends the calculated pre-torque T1 to the adder 56.

  When it is determined that the vehicle is ready for sudden start, the start determination unit 64 causes the torque calculation unit 65 to calculate the correction torque T4. The torque calculator 65 calculates a correction torque T4 according to the detected engine speed N and the detected vehicle speed V with reference to the correction torque characteristic map. The correction torque characteristic map shows the correction torque with the engine speed and the vehicle speed as variables, and is stored in the ROM 32a in advance. The correction torque T4 is a value larger than the pre-torque T1. The torque calculator 65 sends the calculated correction torque T4 to the adder 56.

  Similarly to the first embodiment, the ΔN torque calculation unit 54 calculates ΔN torque T2 corresponding to the vehicle speed V and the differential rotation speed ΔN with reference to the ΔN torque characteristic map M (ΔN, V). The ΔN torque calculator 54 sends the calculated ΔN torque T2 to the adder 56. The adder 56 outputs the sum of the ΔN torque T2 and the pre-torque T1, or the sum of the ΔN torque T2 and the correction torque T4.

  In the second embodiment, the sum of the ΔN torque T2 and the pre-torque T1 is a normal torque when not in the sudden start preparation state, and the sum of the ΔN torque T2 and the correction torque T4 is the normal value. It is a torque with a larger value. In this way, when the start determination unit 64 as the start state determination means determines the sudden start level state, the second value is provided with the microcomputer 32B that performs the sudden start control by changing the pre-torque T1 of the normal value to a large value. Also in this embodiment, the same effect as in the first embodiment can be obtained.

In the present invention, the following embodiments are also possible.
(1) The present invention may be applied to a driving force distribution control device for a parallel hybrid vehicle including two power sources, an engine and a motor. This parallel system is a system in which wheels are driven by both an engine and a motor. Driving force for the hybrid vehicle to travel is mainly supplied from the engine. The motor is driven at the time of starting or acceleration when a load is applied to the engine, and the driving force of the engine is assisted by the driving force of the motor. Also in this embodiment, the same effect as that of the first embodiment can be obtained.

  (2) The present invention may be applied to a driving force distribution control device for a series-type hybrid vehicle provided with two power sources of an engine and a motor. 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 is used only to drive a generator (not shown). The AC power generated by the generator is converted to DC power by the inverter and charged to the battery. 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 increases or decreases as the operation amount of the operation pedal increases or decreases. The operation amount of the operation pedal indicates an acceleration operation amount indicating the driver's willingness to accelerate. Also in this embodiment, the same effect as that of the first embodiment can be obtained.

  (3) You may apply this invention to the electric vehicle which drives a wheel only with the drive force of a motor. 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. Also in this embodiment, the same effect as that of the first embodiment can be obtained.

(4) The present invention may be embodied in a driving force distribution control device for a four-wheel drive vehicle based on a rear wheel drive.
(5) In the first embodiment, the start determination is performed by the torque correction necessity determination unit 58, and the correction ΔN torque calculation unit 57 calculates the correction ΔN torque. Instead, when the ΔN torque calculation unit 54 makes a start determination and determines that it is in a sudden start preparation state or a sudden start state, the ΔN torque calculation unit 54 performs a calculation to correct the ΔN torque, The correction necessity determination unit 58 and the correction ΔN torque calculation unit 57 may be omitted.

(6) In the first and second embodiments, the ΔN torque calculation unit 54 calculates the ΔN torque, but the ΔN torque calculation unit 54 may be omitted.
(7) In the first embodiment, the engine speed sensor 34 is used as the acceleration operation amount detection means. However, it is determined only whether or not it is in a sudden start preparation state and not in a sudden start state. In this case, a throttle opening sensor or a sensor that detects the depression angle of the accelerator pedal may be used as the acceleration operation amount detection means.

  (8) In the first embodiment, when it is determined that the vehicle is not in the sudden start preparation state and is not in the sudden start state, the driving force distribution amount to the front wheel side and the rear wheel side is distributed equally. It may be. In this way, at the time of a normal start, the driving force is distributed only to the drive wheels (one of the front wheels or the rear wheels) to start with good fuel efficiency, and when starting quickly, the driven wheels (front wheels or rear wheels) By distributing the driving force also to the other of the above, it is possible to suppress idling and perform a stable sudden start.

  (9) When it is determined that the vehicle is ready for sudden start, or when it is determined that the vehicle is suddenly started, the driving force distribution amount to the front wheel side and the rear wheel side is equally distributed. You may do it. If it does in this way, it can start without idling using any of the traction (force in which a wheel grips a road surface) of a front wheel and a rear wheel.

  (10) The present invention may be applied to a four-wheel drive control device as disclosed in Patent Document 2 and Patent Document 3. That is, the present invention may be applied to a driving force distribution control device that can change the driving force distribution ratio for the front wheel side and the rear wheel side from 100: 0 to 0: 100.

The technical idea that can be grasped from the above-described embodiment will be described below.
[1] 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, the amount of driving force distribution to the front wheel side and the rear wheel side is variably controlled. In a driving force distribution control method for a wheel drive vehicle,
When the vehicle speed detected by the vehicle speed detection means is less than a preset vehicle speed determination threshold and the acceleration operation amount detected by the acceleration operation amount detection means is greater than or equal to a preset acceleration operation amount determination threshold, When the sudden start preparation state is determined, and the determination of the sudden start preparation state is made, the driving force distribution amount is controlled in a direction in which the driving force distribution amount to the front wheel side and the rear wheel side becomes equal. A driving force distribution control method for a four-wheel drive vehicle.

[2] Based on the vehicle speed obtained by the vehicle speed detecting means and the engine speed obtained by the engine speed detecting means, the driving force distribution amount to the front wheel side and the rear wheel side is variably controlled. In the driving force distribution control device for wheel drive vehicles,
A starting state determining means for predicting and determining a starting state of the vehicle, wherein the vehicle speed detected by the vehicle speed detecting means is less than a preset vehicle speed determining threshold, and the engine speed detected by the engine speed detecting means; Is greater than a predetermined engine speed determination threshold value, the start state determination means determines that it is in a sudden start preparation state. A driving force distribution control device for a four-wheel drive vehicle, wherein the driving force distribution amount is controlled in a direction in which the driving force distribution amounts become equal to each other.

The schematic block diagram of the four-wheel drive vehicle in 1st Embodiment. The circuit diagram which shows the electric constitution of the driving force distribution control apparatus in 1st Embodiment. The functional block diagram of the microcomputer in 1st Embodiment. The flowchart which shows the torque correction necessity determination process in 1st Embodiment. The flowchart which shows the torque correction necessity determination process in 1st Embodiment. The flowchart which shows the torque correction necessity determination process in 1st Embodiment. The circuit diagram which shows the electric constitution of the driving force distribution control apparatus in 2nd Embodiment.

Explanation of symbols

  11: Four-wheel drive vehicle constituting the vehicle. 17 ... Driving force transmission device. 20: Rear wheel as a driven wheel. 31 ... Driving force distribution control device. 32, 32B... Microcomputer as starting state determination means. 33: Wheel speed sensor constituting vehicle speed detection means. 34. An engine speed sensor as acceleration operation amount detection means (engine speed detection means). 52. A vehicle speed calculation unit constituting vehicle speed detection means. 58... A torque correction necessity determination unit as a starting state determination unit. 64: A start determination unit as start state determination means. V ... Vehicle speed. V1: Vehicle speed determination threshold value. N: Engine speed as an acceleration operation amount. N1... Engine speed determination threshold value as an acceleration operation amount determination threshold value. N2 ... Engine speed determination threshold value as a sub acceleration operation amount determination threshold value. t1 is a first time determination threshold value. t2 is a second time determination threshold value as a predetermined time.

Claims (4)

A four-wheel drive vehicle that variably controls the amount of driving force distribution to the front wheel side and the rear wheel side 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 device of
A starting state determining means for predicting and determining a starting state of the vehicle, wherein the vehicle speed detected by the vehicle speed detecting means is less than a preset vehicle speed determining threshold and the acceleration operation amount detected by the acceleration operation amount detecting means; Is greater than a predetermined acceleration operation amount determination threshold value, the start state determination means determines that it is in a sudden start preparation state, and when the determination of the sudden start preparation state is made, the front wheel side and the rear wheel side are determined. A driving force distribution control device for a four-wheel drive vehicle, wherein the driving force distribution amount is controlled in a direction in which the driving force distribution amounts become equal to each other.   The engine speed detection means for detecting the engine speed is the acceleration operation amount detection means, the engine speed is the acceleration operation amount, the engine speed determination threshold is the acceleration operation amount determination threshold, and the start state determination means is When the engine speed detected by the engine speed detection means becomes less than the sub engine speed determination threshold value that is smaller than the engine speed determination threshold value after determining the sudden start preparation state, The starting state determining means determines that the state is a sudden starting state, and when the sudden starting state is determined, the driving force distribution amount to the front wheel side and the rear wheel side becomes equal until the predetermined time elapses thereafter. The driving force distribution control device for a four-wheel drive vehicle according to claim 1, wherein the driving force distribution amount is controlled.   After the start state determination means determines that the sudden start preparation state, a time during which the engine speed detected by the engine speed detection means is less than the engine speed determination threshold and greater than or equal to the sub engine speed determination threshold The state of controlling the driving force distribution amount in a direction in which the driving force distribution amounts to the front wheel side and the rear wheel side become equal when the time determination threshold value set in advance is exceeded. 4. A driving force distribution control device for a four-wheel drive vehicle according to 2.   4. The four-wheel drive vehicle according to claim 2, wherein when the start state determination means determines that it is the sudden start preparation state or the sudden start state, the driving force distribution amount to the front wheel side and the rear wheel side is equally distributed. Driving force distribution control device.

Images