JPS63116935A - Control device for four wheel drive vehicle - Google Patents

Abstract

PURPOSE:To simplify the control of a four wheel drive vehicle without the necessity of vehicle speed compensation, by controlling the vehicle in accordance with the rate of rotational speed between front and rear wheels, corresponding to the slip rate. CONSTITUTION:A pulse period detecting section 66 receives a pulse proportional to the rotational speed of front wheels, delivered from a front wheel rotational speed sensor 61, so as to detect a pulse period TF which is inverse of the front wheel rotational speed NF. A rotation pulse detecting section 67 receives an output signal from a rear wheel rotational speed sensor 62 so as to detect the number NR of pulses in a predetermined period. The detected values are delivered to a rotational speed ratio calculating section 68 which multiplies both values with each other to obtain the rotational speed ratio (e) between the front and rear wheels. If e < e0, where e0 is the rotational speed ratio between the front and rear wheels during full steering operation, it is judged that a slip occurs. The slip judging signal is delivered to a correcting rate setting section 70 to determine a correcting rate so that D* to be applied to the output side cf a duty ratio setting section 65 is corrected.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention is for automatic switching between two and four-wheel drive in a part-time or full-time four-wheel drive vehicle. The present invention relates to a control device that changes the capacity of a transfer clutch, and more specifically, to one that controls the slip rate based on the rotation ratio of front and rear wheels. 2. Description of the Related Art Conventionally, for example, there is a prior art related to automatic switching of a part-time four-wheel drive IJ width, as disclosed in Japanese Patent Application Laid-open No. 138020/1983. Here, if a rotation difference occurs between the front and rear wheels when turning, etc., compare the rotation difference with the set value and 2.
It is shown that four-wheel drive switching is performed.

[Problems to be solved by the invention]

By the way, in the control method based on the rotation difference in the prior art,
Correction based on vehicle speed is required. In other words, the rotational difference between the front and rear wheels is the slip during the sound of rain, and this slip rate S is calculated from the front wheel rotational speed NF and the rear wheel rotational speed NR as 5-NR/NF, and the rotational difference NF-NR. Considering the terms, we get the following. 5-NR/NF -1-(NF -NR) /NF As is clear from this equation, since the vehicle speed term of 1/NF is included, it is necessary to correct the rotational difference by the vehicle speed even if the slip ratio is the same. Therefore, there is a problem in that the computation of correction based on the vehicle speed and the map setting become complicated. The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for a four-wheel drive vehicle that performs control without increasing calculation processing time or program capacity due to vehicle speed correction. It is said that

[Another way to solve the problem]

In order to achieve the above object, the present invention focuses on the fact that the slip rate of the front and rear wheels is expressed by the rotation ratio of both wheels. Therefore, in a four-wheel drive vehicle that has a control element that performs disconnection, disconnection, and change in tl amount in the middle of the drive system of the front and rear wheels, it is necessary to have a sensor that detects the rotation speed of the front and rear wheels, respectively. The rotation ratio between the two is calculated from the rotation speed, and the above-mentioned series control element is controlled in accordance with the relationship between the above-mentioned rotation ratio and a set value.

[For production]

Based on the above configuration, the presence or absence of slip and its magnitude can be determined directly from the rotation ratio of the front and rear wheels, and by controlling the υ1111 element using this rotation ratio, four-wheel drive that does not cause slip can be achieved. In this way, the present invention makes it possible to eliminate the need for correction of vehicle speed by using a rotation ratio that corresponds to the slip ratio.

【Example】

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, in Fig. 1, a transmission system with an automatic transmission as a four-wheel drive vehicle to which the present invention is applied will be explained.
is a crankshaft from an engine E, this crankshaft 1 is connected to a turbine shaft 3 via a torque converter 2, and is transmitted to an automatic transmission 4 by the turbine shaft 3. The automatic transmission 4 includes a planetary gear 5. turbine shaft 3
Clutch θ selectively inputs the power of 7 to the input element of the planetary gear 5, and a one-way clutch 8 that selectively locks each element of the planetary gear 5. It is equipped with a brake 9 and a brake band 10, and the shifted power from the automatic transmission 4 is taken out forward by an output shaft 11 and transmitted to a transmission drive gear 12. It is transmitted to the shaft 16 by the reduction driven gear 13. Further, a front wheel final reduction gear e114 is arranged at the lower part between the torque converter 2 and the automatic transmission 4, and this front wheel final reduction gear f! A drive pinion 17 formed at one end of a shaft 16 integral with the reduction driven gear 13 meshes with the crown gear 15 of 14, so that 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 the transfer drive shaft 119 of the transfer equipment W119 mounted at the rear of the automatic transmission 4. Drive gear 20. It is connected to the transfer driven gear 21. The transfer driven gear 21 is connected to a rear drive shaft 23 via a hydraulic clutch 22, and is configured to transmit power from the rear drive shaft 23 to a rear wheel final reduction gear 25 via a propeller shaft 24. In this way, power is transmitted to the rear wheels according to the clutch torque of the hydraulic clutch 22,
It is configured to run in four-wheel drive. Next, to explain the hydraulic control system, the automatic transmission 4
The transmission has an oil pump 26 mounted directly in front of the engine and constantly driven by the engine, and an oil passage 27 from the oil pump 26 communicates with a transmission III control circuit 28. Depending on each driving condition, the transmission control circuit 28 controls the clutches 6 and 7. Brake 9. The brake band 10 is oiled and drained to automatically shift gears. The oil passage 27 also communicates with a hydraulic clutch control circuit 30. and will be explained below. First, this oil passage 27 communicates with a pressure regulating valve 40 that always regulates the pressure to a constant reducing pressure, and an oil passage 31 branching from the oil passage 27 communicates with a transformer 77 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 connects to the piston chamber 22a of the hydraulic clutch 22. It's communicating. The pressure regulating valve 40 has a valve body 41. Spool 42. Spool 4
A hydraulic chamber 43 communicating with one of the reducing pressure oil passages 32 of 2. An oil passage 44 that guides the reduced hydraulic pressure to the oil passage 32 consists of a spring 45 biased against the other side of the spool 42. Then, the spool 42 is moved 8 times based on the balanced relationship between the force applied to the hydraulic pressure v43 on one side of the spool 42 and the force of the spring 45, and the line pressure of the oil passage 27 is derived from the boat 41a, or 1: The line pressure of the oil path 27 is derived from the boat 41a. The pressure is adjusted by draining the oil from the oil passage 44, and the oil pressure is guided to the reducing pressure oil passage 32 and the oil pressure chamber 43 through the oil passage 44. In this way, a constant reducing pressure is always generated in the reducing pressure oil passage 32. That is, if the land pressure receiving area in the hydraulic chamber 43 is S, the reducing pressure is PR, and the spring force is F, then R-8-F is obtained, and a constant reducing pressure of PR-F/S is always generated. Based on the duty signal from the control unit 60, the solenoid valve 33 opens the drain boat 33a, controls the reducing pressure PR by the line pressure regulating valve 40 to generate a control pressure pc, and transfers this to the transfer control valve 5.
Acts on 0. The transformer 77IllID valve 50 has a valve body 51. Spools 52 with different land pressure receiving areas. Hydraulic chamber 53. into which the control pressure pc of one side of the spool 52 is introduced. The other side of the spring 54 is biased, and controls the line pressure of the oil passage 31 introduced from the boat 51a to generate clutch pressure PT.
Take it out at 4. That is, the force due to the clutch pressure PT due to the land pressure receiving area difference of the spool 52 and the control pressure Pc of the hydraulic chamber 53.
The force of the spring 54 acts downwardly, and the opposing force of the spring 54 acts upwardly. When the control pressure pc increases, the spool 52 is moved upward to close the boat 51a, and the clutch pressure PT is lowered by listening to the drain boat 51c. 51a is increased by 171 degrees to operate so as to exceed the clutch pressure of 2 clutches. As a result, the control pressure Pc, the clutch pressure Pc, the spring force F, and the spool large diameter area 81. The following equation holds true between the small diameter area St. pc 6 St + PT (St St ) = FP
T= (F-Pc-8z)/(StSz)
Here 81. Since Sz and F are constant, clutch pressure 2
The pressure is controlled in inverse proportion to the duty-controlled control pressure pc. To explain this with reference to FIG. 2, when the duty ratio of the solenoid valve 33 is 0%, no pressure is discharged, and the control pressure Pc
becomes the highest value, which is equal to the reducing pressure PR of the pressure regulating valve 40, and from this state, as the duty ratio increases and the pressure is exhausted, the control pressure Pc decreases, resulting in a characteristic as shown by the broken line. On the other hand, in relation to the control pressure Pc, the two clutch pressures are zero in a region smaller than the duty ratio D1, and increase proportionally after the duty ratio D1, resulting in a characteristic as shown by the solid line. Referring to FIG. 3, an electric control system including a control unit 60 will be explained. First, it has sensors 61 and 62 that detect the rotational speed of the front and rear wheels, and a throttle opening degree hinge 63 that detects the accelerator depression state. Here, the transmission system of the embodiment is based on FF, and when front wheel slip is taken into consideration, the rear wheels detect the vehicle speed more accurately. Therefore, the rear wheel rotation speed NR of the sensor 62 and the throttle opening θ of the throttle opening sensor 63 are input to the clutch torque calculating section 64 of the control unit 60, and the lζ clutch torque Tc is calculated according to the driving condition using the map of NR-0. search for. That is, the clutch torque Tc is set to be large in a high-load running state such as starting or climbing a hill, and conversely, the clutch torque Tc is set to be small in a light-load running state. The clutch torque TO signal is input to the duty ratio setting section G5 to determine the duty ratio according to the clutch torque Tc, but due to the characteristics shown in FIG.
It is an increasing function with respect to C. A signal corresponding to this duty ratio is output to the solenoid valve 33. Next, the clutch torque correction system will be described. The front wheel rotation speed sensor 61 outputs a pulse proportional to the front wheel rotation speed by turning on and off a reed switch. (1/Nr-) is detected. The output of the rear wheel rotation speed sensor 62 is sent to the rotation pulse detection section 6.
7 and detect the number of pulses nR (kNR) for a certain period of time. Then, these are input to the rotation ratio extraction section 68, and the front and rear wheel rotation ratio e (nR-TE) is extracted by the steering wheel of both sides, and the rotation ratio eQ in the case of full steering is determined by the slip i section 69. On the other hand, if O<e □, it is determined that there is a slip. The slip determination signal is inputted by the correction factor setting section 10 to determine the correction factor α (α〉1〉), and the correction section 71 added to the output side of the duty ratio setting section 65 corrects D.α. Next, the operation of the control t2'11 device configured in this way will be explained. First, the engine power is transferred to the torque converter 2, the turbine shaft 3, and the clutch 6 in the case of forward movement. The power input to the brane gear 175 of the automatic transmission 4 and shifted here is:
It is directly transmitted from the output shaft 11 to the front wheels via the front wheel final reduction gear 14. In addition, the transmission power is transferred from the transfer drive shaft 1.
8 and onwards, and the torque corresponding to the clutch torque of the hydraulic clutch 22 is transmitted to the propeller shaft 24. It is also transmitted to the rear wheels via the rear wheel final reduction gear 25, resulting in four-wheel drive driving. On the other hand, during such driving, the clutch torque calculating section G4 of the control unit 60 searches for clutch torque TO according to the driving state based on the rear wheel rotational speed NR and throttle opening degree θ corresponding to the vehicle speed, and a duty signal corresponding to this is searched. is input to the solenoid valve 33. Therefore, the hydraulic clutch control circuit 3
0, the constant reducing pressure from the pressure regulating valve 40 is drained by the solenoid valve 33 to generate a control pressure, and this control pressure operates the transformer 77 control valve 50 to supply oil to the hydraulic clutch 22, and the clutch torque is calculated as described above. A torque equal to the clutch torque TC of section 64 is generated. Therefore, the larger the load, the larger the clutch torque TC, which increases the torque transmitted to the rear wheels and improves the performance as a four-wheel drive. Further, when the hydraulic clutch 22 is torque-controlled according to the driving state as described above, the torque is further corrected depending on the slip state of the front and rear wheels, and this operation will be explained with reference to the flowchart in FIG. 4. First, every time a rear wheel pulse is input, an interrupt routine is executed and a counter nR is incremented. Further, in a timer routine executed at fixed time intervals, the value of the counter nR is latched in the register NR at every set time TR, and at the same time, the counter rl is cleared. When the front wheel pulse changes from the L level to the H level, the period TF is determined from the difference between the previous and current values of a free running counter (a counter that increments at regular intervals). In this way, the front wheel pulse period TF and the rear wheel pulse number nR are always
is updated and detected, and using these, the rotation ratio e(rN2・TF > is calculated in the main routine. If e<eo, the duty ratio is increased by the correction factor α. Therefore, the hydraulic clutch 22 This increases the torque capacity of the transfer clutch and increases the torque transmitted to the rear wheels.In this way, slippage between the front and rear wheels does not occur.The torque control of the transfer clutch has been described as an embodiment of the present invention. automatic switching of
It can also be applied to Afro-tsuku, etc. with a center differential. Further, the set rotation ratio e may change depending on the steering angle. (Effect of the invention 1 As described above, according to the present invention, control is performed in accordance with the slip ratio based on the rotation ratio of the front and rear wheels, so vehicle speed correction is not necessary and control is simplified. Front wheel rotation speed Find the reciprocal pulse period for , and multiply this by the number of rear wheel pulses to calculate the rotation ratio in the cylinder.By simplifying calculations in this way, the processing time and program capacity can be reduced. The amount of operation is corrected by the control using the duty ratio, so it is easy to control the operating amount.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the control device of the present invention, Fig. 2 is a characteristic diagram of duty control, Fig. 3 is a block diagram of the control unit, and Fig. 4 is a flow chart diagram explaining the operation. It is. 15... Front wheel final reduction device, 25... Rear wheel final reduction device, 19... Transfer device, 22... Hydraulic clutch, 30... Hydraulic clutch control circuit, 60... Control unit, 61 ...Front wheel rotation speed sensor, 62...Rear wheel rotation speed sensor, 68...Rotation ratio calculation unit, 69...
Slip determination section, 71... correction section. Patent Applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney Makoto Kobashi Patent Attorney Mura 11 Susumu No. 4

Claims (1)

[Scope of Claims] A four-wheel drive vehicle having a control element that performs disconnection, disconnection, capacity change, etc. in the middle of the drive system of the front and rear wheels, comprising a sensor that detects the rotation speed of the front and rear wheels, respectively, and the above-mentioned sensor Calculate the rotation ratio between the front and rear wheels from the rotation speed of the front and rear wheels, and control the above control elements based on the relationship between the rotation ratio and the set value.
Control device for wheel drive vehicles.