JP2676340B2 - Control device for four-wheel drive vehicle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for automatically switching between 2 and 4 wheel drive and changing the capacity of a transfer clutch in a part-time or full-time four-wheel drive vehicle. More specifically, the present invention relates to the one controlled by the slip ratio according to the rotation ratio of the front and rear wheels. 2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 58-138020 discloses a prior art regarding automatic switching of a part-time four-wheel drive vehicle. Here, it is shown that when a rotation difference occurs between the front and rear wheels during turning, etc., the rotation difference is compared with a set value to switch between 2 and 4 wheel drive. [Problems to be Solved by the Invention] By the way, in the control method based on the rotation difference of the above-mentioned prior art, the correction based on the vehicle speed is required. That is, the rotation difference between the front and rear wheels is a slip between the two, and this slip ratio S is calculated by S = N _R / N _{F from the} front wheel rotation speed N _F and the rear wheel rotation speed N _R , and the rotation difference N _F Considering the term −N _R , it becomes as follows. S = N _R / N _F = 1- (N _F −N _R ) / N _F As is clear from this equation, the term 1 / N _F of the vehicle speed is included, so the rotation difference is corrected by the vehicle speed even with the same slip ratio. There is a need to. Therefore, there is a problem that the calculation of the correction based on the vehicle speed and the map setting become complicated. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for a four-wheel drive vehicle that is controlled without increasing the calculation processing time and the program capacity by correcting the vehicle speed. I am trying. In order to achieve the above object, the present invention controls a clutch torque of the hydraulic clutch by interposing a transfer device having a hydraulic clutch in the middle of a drive system of front and rear wheels. In a control device for a four-wheel drive vehicle that cuts off transmission torque to one of the front wheels or rear wheels or changes the capacity, the front and rear wheels that output pulses proportional to the rotational speeds of the front and rear wheels, respectively. Rotation speed sensor, and a pulse cycle detection unit that obtains the pulse cycle of the reciprocal of the rotation speed from the output of either one of the front and rear wheel rotation speed sensors, and the rotation from the output of the other rotation speed sensor. Number of pulses for a certain period of time, the pulse number output from the pulse period detector, and the pulse number output from the pulse detector. A rotation ratio calculation unit that calculates the rotation ratio of the other rotation speed to one rotation speed of the front wheel or the rear wheel, and a slip determination unit that makes a slip determination based on the rotation ratio and a predetermined rotation ratio. ,
The clutch torque of the hydraulic clutch is increased based on the output of the slip determination unit to increase the clutch torque. Based on the above configuration, in the case of four-wheel drive based on FF, for example, when there is a rotation difference between the front and rear wheels, the front wheel rotation speed N _F is determined from the outputs of the front wheel and rear wheel rotation speed sensors. The reciprocal pulse period T _F (= 1 / N _F ) and the pulse number n _R (= k · N _R ) of the rear wheel rotation speed N _{R for} a certain period of time are obtained, and these are multiplied to obtain the front wheel rotation speed N _R. The rotation ratio e of the rear wheel rotation speed N _R with respect to _F is calculated, the slip is determined based on this rotation ratio e, and when the slip is determined, the drive torque of the rear wheel is increased. Therefore, as compared with the conventional case where the front-rear wheel rotation ratio is obtained from the difference between the front wheel rotation speed N _F and the rear wheel rotation speed N _R , the slip is stabilized, and the correction calculation by vehicle speed and map setting are performed. Since it is unnecessary, the calculation time can be shortened and the increase of programs can be eliminated. Then, the presence / absence of the slip and the magnitude thereof are immediately known from the rotation ratios of the front and rear wheels, and control is performed to increase the driving torque of the rear wheels by using this rotation ratio, whereby the four-wheel drive without slip is achieved. EXAMPLES Hereinafter, one example of the present invention will be specifically described with reference to the drawings. First, referring to FIG. 1, a transmission system with an automatic transmission will be described as a four-wheel drive vehicle to which the present invention is applied.
Is a crankshaft from the engine E. The crankshaft 1 is connected to a turbine shaft 3 via a torque converter 2 and is configured to be transmitted to the automatic transmission 4 by the turbine shaft 3. The automatic transmission 4 includes clutches 6 and 7 that selectively input the power of the planetary gear 5 and the turbine shaft 3 to the input elements of the planetary gear 5, and a one-way clutch 8 that selectively locks each element of the planetary gear 5, a brake 9 and a brake. The band 10 is provided, and the power that has been shifted from the automatic transmission 4 is taken out forward by the output shaft 11 to reduce the reduction drive gear 12 and the reduction driven gear 1.
Transmitted to axis 16 by 3. A front wheel final reduction gear 14 is arranged below the torque converter 2 and the automatic transmission 4, and the reduction driven gear is attached to the crown gear 15 of the front wheel final reduction gear 14.
Drive pinion 17 formed at one end of shaft 16 integral with 13
By engaging with each other, the power is directly transmitted to the front wheels. The other end of the shaft 16 is extended rearward by a transfer drive shaft 18 and is connected to a transfer drive gear 20 and a transfer driven gear 21 of a transfer device 19 mounted on the rear portion of the automatic transmission 4. The transfer driven gear 21 is connected to the rear drive shaft 23 via a hydraulic clutch 22, and the rear drive shaft 23 is further connected to the propeller shaft 23.
It is configured to be transmitted to the rear wheel final reduction gear 25 via 24. In this way, power is transmitted to the rear wheels in accordance with the clutch torque of the hydraulic clutch 22 and the vehicle is driven by four wheels. Next, the hydraulic control system will be described. The hydraulic control system has an oil pump 26 that is mounted immediately after the automatic transmission 4 and is constantly driven by the engine.
Communicate with the shift control circuit 28. Then, according to each traveling condition, the shift control circuit 28 supplies and drains the clutches 6 and 7, the brake 9, and the brake band 10 to automatically shift. The oil passage 27 also communicates with the hydraulic clutch control circuit 30. The hydraulic clutch control circuit 30 will be described below. First, the oil passage 27 communicates with a pressure regulating valve 40 that regulates a constant reducing pressure, and an oil passage branched from the oil passage 27.
31 communicates with the transfer control valve 50. Further, the reducing pressure oil passage 32 from the pressure regulating valve 40 communicates with the duty solenoid valve 33 via the control side of the control valve 50, and the clutch pressure oil passage 34 from the control valve 50 is connected to the piston chamber 22a of the hydraulic clutch 22.
Is in communication with The pressure regulating valve 40 includes a hydraulic chamber 43 and an oil passage 32 that communicate with the valve body 41, the spool 42, and one reducing pressure oil passage 32 of the spool 42.
It is composed of an oil passage 44 that guides the reduced hydraulic pressure to a spring, and a spring 45 that is biased to the other side of the spool 42. Then, the spool 42 is moved by the equilibrium relationship between the force of the one hydraulic chamber 43 of the spool 42 and the force of the spring 45, so that the oil passage 27 from the port 41a is moved.
The line pressure is derived, or the pressure is adjusted by draining from the drain port 41b, and the oil pressure is guided to the reducing pressure oil passage 32 and the hydraulic chamber 43 by the oil passage 44, and thus, in the reducing pressure oil passage 32, A constant reducing pressure is constantly generated. That is, the land pressure receiving area in the hydraulic chamber 43
If S, the reducing pressure is P _R and the spring force is F, then P _R · S = F, and a constant reducing pressure due to P _R = F / S is constantly generated. Based on the duty signal from the control unit 60, the solenoid valve 33 opens the drain port 33a to control the reducing pressure P _R by the line pressure regulating valve 40 to generate a control pressure P _C , which is transfer-controlled. Acts on valve 50. The transfer control valve 50 includes a valve body 51, a spool 52 having different land pressure receiving areas, a hydraulic chamber 53 into which one control pressure P _C of the spool 52 is introduced, and a spring 54 biased to the other side.
The clutch pressure P _T is generated by controlling the line pressure of the oil passage 31 introduced from the port 51a.
_T is taken out from the port 51h to the oil passage 34. That is, the force due to the clutch pressure P _T due to the land pressure receiving area difference of the spool 52 and the force due to the control pressure P _C of the hydraulic chamber 53 act downward,
The force of 54 acts upwards against it. And control pressure
When P _C becomes higher, the spool 52 is moved downward and the port 51a
And the drain port 51c is opened to reduce the clutch pressure P _T and the control pressure P _C becomes lower, conversely the spool 52 moves upward to increase the opening of the port 51a and increase the clutch pressure P _T. Works like. As a result, control pressure P _C , clutch pressure P _T , spring force F,
The following formula is established between the spool large diameter area S ₁ and the spool small diameter area S ₂ . P _C · S ₂ + P _T (S ₁ −S ₂ ) = F P _T = (F−P _C · S ₂ ) / (S ₁ −S ₂ ), where S ₁ , S ₂ , and F are constant , The clutch pressure P _T is controlled in an inversely proportional relationship with the duty-controlled control pressure P _C. This will be described with reference to FIG. 2. When the duty ratio of the solenoid valve 33 is 0%, the pressure is not exhausted at all, and the control pressure P _C becomes the highest value equal to the reducing pressure P _{R of the} pressure regulating valve 40. The control pressure P _C decreases as the ratio gradually increases and the pressure is exhausted, and the characteristic becomes as shown by the broken line. On the other hand, in relation to the control pressure P _C , the clutch pressure P _T is zero in a region smaller than a certain duty ratio D ₁ , and after that duty ratio D ₁ becomes proportionally larger, and has a characteristic as shown by the solid line. Become. An electric control system including the control unit 60 will be described with reference to FIG. First, the sensors 61 and 62 for detecting the rotational speeds of the front and rear wheels and the throttle opening sensor 63 for detecting the accelerator pedal depression state.
Having. Here, in the transmission system of the embodiment, the FF base is used, and considering the front wheel slip, the rear wheel more accurately detects the vehicle speed. Therefore, the rear wheel rotation speed N _{R of the} sensor 62
And the throttle opening θ of the throttle opening sensor 63 are input to the clutch torque calculation unit 64 of the control unit 60, and the clutch torque T _C according to the traveling state is searched from the map of N _R −θ. That is, the clutch torque T _C is increased in a high load traveling state such as starting and climbing, and conversely, the clutch torque T _C is set small in a light load traveling state. Clutch torque
The signal of T _C is input to the duty ratio setting unit 65 to determine the duty ratio D according to the clutch torque T _C , but the duty ratio D becomes an increasing function with respect to the clutch torque T _C due to the characteristic of FIG. ing. Then, the signal of the duty ratio D is output to the solenoid valve 33. Next, the clutch torque correction system will be described. Front wheel speed sensor 61 is for outputting pulses proportional to wheel rotational speed by a lead switch on and off, which is input to the pulse period detector 66, a pulse period of the reciprocal of the front wheel rotation number N _F T _F (1 / N _F ) is detected. Rear wheel speed sensor
The output of 62 is input to the rotation pulse detection unit 67, and the number of pulses n _R (kN _R ) in a fixed time is detected. Then, these are input to the rotation ratio calculation unit 68, and the slip ratio indicating the deviation of the rotation speed of the rear wheels from the rotation speed of the front wheels is calculated by multiplying both by the rotation ratio e (= n _R · T _F ) of the front and rear wheels. In the slip determination unit 69,
For example, when e <e ₀ with respect to the rotation ratio e _{0 in} the case of full steering, the slip is determined. The slip determination signal is the correction factor setting section
The correction ratio α (α> 1) is input to the 70, and the correction unit 71 added to the output side of the duty ratio setting unit 65 corrects D · α. Next, the operation of the control device thus configured will be described. First, the engine power is input to the planetary gear 5 of the automatic transmission 4 via the torque converter 2, the turbine shaft 3, and the clutch 6 in the case of forward movement, and the power changed here is transmitted from the output shaft 11 to the front wheel final reduction gear unit 14. Directly to the front wheels via. Further, the speed change power is also transmitted to the transfer drive shaft 18 and thereafter, and a portion corresponding to the clutch torque of the hydraulic clutch 22 is also transmitted to the rear wheels via the propeller shaft 24 and the rear wheel final reduction gear 25 to drive the four-wheel drive. Becomes On the other hand, the clutch torque calculation unit 64 of the control unit 60 searches the clutch torque T _C according to the traveling state by the rear wheel rotation speed N _R and the throttle opening θ corresponding to the vehicle speed during such traveling, and the duty corresponding to this is searched. The signal is input to the solenoid valve 33. Therefore, in the hydraulic clutch control circuit 30, a constant reducing pressure by the pressure regulating valve 40 is drained by the solenoid valve 33 to generate control pressure, and the transfer control valve 50 is operated by this control pressure to supply oil to the hydraulic clutch 22. A torque equal to the clutch torque T _C of the clutch torque calculation unit 64 is generated. Therefore, as the load increases, the clutch torque T _C also increases, and the torque transmitted to the rear wheels increases, improving the performance as a four-wheel drive. Further, as described above, when the torque of the hydraulic clutch 22 is controlled by the traveling state, the hydraulic clutch 22 is further corrected by the slip state of the front and rear wheels. This action will be described with reference to the flowchart of FIG. First, for the rear wheel pulse, an interrupt routine is executed every time a pulse is input, and the counter n _R is incremented. Further, the timer routine executed at predetermined time intervals, latches the value of the counter n _R every predetermined time T _R to register N _R, clears the counter n _R simultaneously. For the front wheel pulse, when the pulse changes from the L level to the H level, the cycle T _F is obtained from the difference between the values of the previous free running counter (the counter that increments at regular intervals). In this way, the front wheel pulse period T _F and the rear wheel pulse number n _R are constantly updated and detected, and the rotation ratio e (n _R · T _F ) is calculated in the main routine using these, and when e <e ₀ , Correction factor α
The duty ratio D is increased and corrected by. Therefore, the torque capacity of the hydraulic clutch 22 is increased and the rear wheel transmission torque is increased, so that the front and rear wheels do not slip. The torque control of the transfer clutch has been described above as the embodiment of the present invention. However, automatic switching of 2 and 4 wheel drive,
It can also be applied to diff locks with a center diff. The set rotation ratio e may change depending on the turning angle. As described above, according to the present invention, since the slip ratio is controlled according to the rotation ratios of the front and rear wheels, the vehicle speed correction is unnecessary and the control is simplified. For the front wheel speed, find the pulse period of its reciprocal,
The rotation ratio is easily calculated by multiplying this by the number of rear wheel pulses. By facilitating calculations, etc., the processing time,
The program capacity is small. Since the duty ratio D of the operation amount is corrected by the control based on the duty ratio, the control is easy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram showing an embodiment of a control device of the present invention, FIG. 2 is a characteristic diagram of duty control, FIG. 3 is a block diagram of a control unit, and FIG. [Fig. 7] is a flow chart for explaining the operation. 15 …… Front wheel final reducer, 25 …… Rear wheel final reducer, 19 ……
Transfer device, 22 ... Hydraulic clutch, 30 ... Hydraulic clutch control circuit, 60 ... Control unit, 61 ... Front wheel speed sensor, 62 ... Rear wheel speed sensor, 68 ... Rotation ratio calculation unit, 69 ... … Slip bottom, 71 …… Correction part.

Claims (1)

(57) [Claims] By interposing a transfer device equipped with a hydraulic clutch in the middle of the drive system for the front and rear wheels and controlling the clutch torque of the hydraulic clutch, the transfer torque to the drive system of either the front wheel or the rear wheel is interrupted or the capacity is changed. In a control device for a four-wheel drive vehicle that performs the following, the rotational speed of either the front or rear wheel rotation speed sensor or the front or rear wheel rotation speed sensor that outputs a pulse proportional to the front and rear wheel rotation speed, respectively. A pulse cycle detection unit that obtains the pulse cycle of the reciprocal number of revolutions from the output of the sensor, a rotation pulse detection unit that obtains the number of pulses of the revolution speed for a fixed time from the output of the other revolution speed sensor, and an output from the above pulse period detection unit And the number of pulses output from the rotation pulse detector is multiplied to obtain the rotation ratio of one of the front wheels and the rear wheel to the other rotation speed. And a slip determination unit that makes a slip determination based on the rotation ratio and a predetermined rotation ratio, and increases the clutch torque of the hydraulic clutch based on the output of the slip determination unit. A four-wheel drive vehicle control device characterized by increasing the clutch torque.