JPS63176727A - Control method for four-wheel-drive gear for vehicle - Google Patents

Abstract

PURPOSE:To prevent the generation of a tight corner braking phenomenon, by adjusting a transmission torque capacity by a friction engaging means in accordance with an obtained speed change pattern. CONSTITUTION:A control device 71 outputs a control signal, for select control of a speed change shift of a transmission 54 in accordance with a preset speed change pattern basically corresponding to a manual shift range, car speed V and a throttle opening theta, to a hydraulic control unit 56. While a pulse signal of predetermined duty ratio, for controlling a transmission torque capacity of a differential control clutch 69 in accordance with the speed change shift and the throttle opening theta, is output to a servo hydraulic control valve. Further in the time of non-steady operation of a turn and a slip or the like, a pulse signal of duty ratio corresponding to that non-steady condition is output to the servo hydraulic control valve.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a control method for a four-wheel drive system that can change the torque distribution ratio between front and rear wheels using a friction engagement means such as a wet multi-disc clutch. is.

BACKGROUND OF THE INVENTION Among this type of four-wheel drive systems, for example, a full-time four-wheel drive system has already been proposed by the present applicant in Japanese Patent Application No. 60-280662@. Its basic configuration is that the output shaft of the automatic transmission is connected to the planetary carrier of the planetary gear mechanism that constitutes the center differential device, and the ring gear, which is one output member, is connected to the rear wheel drive shaft. The output member Nangya is connected to the front export force shaft via a transmission means consisting of a chain and a sprocket, and the transmission torque is transmitted between the planetary carrier, the sun gear, and the back of the ring gear 7. It is equipped with a differential control clutch that allows the set to be changed.

Therefore, with such a configuration, by disengaging the differential control clutch, the center differential device performs complete differential operation, and by completely engaging and disengaging the differential control clutch, the center differential device operates. As a result, the rear wheel drive shaft and the front wheel drive shaft are in a so-called direct connection state, and for each of these states, the engagement force of the differential control clutch must be adjusted in a stopped state between fully engaged and fully disengaged. For example, the torque distribution ratio between the rear wheel drive shaft and the front wheel drive shaft can be set as appropriate.

Therefore, in the device of the above-mentioned Japanese Patent Application No. 60-280662,
By providing a control device that controls the transmission torque capacity by the differential control clutch according to the input torque, the transmission torque capacity increases as the accelerator is depressed and the throttle opening increases, that is, the differential limit is strengthened)
This improves drivability and handling stability in situations where high output is required.

Conventionally, as a method of controlling a four-wheel drive system that uses a differential limiting device that limits the differential of the center differential device described above, a method has been proposed that uses the input torque described above and the gear position of a transmission installed upstream of the transfer device. In addition to methods of controlling the differential limiting capacity ω by a differential limiting device based on downshifts, driving on rough roads, slippage of the front and rear wheels, and even steering angle, there are many other methods. Conventionally, a method has been considered in which the engagement and disengagement of the differential limiting device and the increase and decrease of the transmission torque capacity are controlled by setting priorities to the conditions under which the differential control should be performed.

Problems to be Solved by the Invention However, according to the above method of constantly limiting the differential, the differential limiting capacity is determined depending on the throttle opening and the gear position of the transmission during steady driving, and when braking or slipping. In unsteady situations such as when a problem occurs, the differential limiting capacity is determined according to the conditions, but since the differential limiting capacity is a constant capacity depending on each condition, it does not match the running performance or driving sensation required by the driver. did not necessarily match. In other words, driving conditions can be roughly divided into agile and sporty driving and smooth and easy so-called economical driving, and these driving modes are, for example, power shift patterns and economy driving in electronically controlled automatic transmissions. In the former case, the vehicle will accelerate to a relatively slow speed in a low gear, increasing the torque generated at the wheels, and in the latter case, the vehicle speed will increase. Accordingly, shift up quickly and carefully to avoid slipping and sudden acceleration. These driving conditions are ultimately determined by the driver's preference, but if a general differential restriction is applied during the power shift pattern, the differential restriction capacity will be insufficient and the torque distribution ratio to the front or rear wheels will be affected. This may cause a situation where steering stability deteriorates, and conversely, during economy shift patterns, differential limiting capacity may become excessive and tight corner braking may occur, which does not meet the driver's needs. There is a problem where it becomes running.

The present invention was made against the background of the above-mentioned circumstances, and it is an object of the present invention to provide a control method that can achieve a four-wheel drive state that matches the driving state preferred by the driver.

Means to solve the problem The torque generated by the wheels has a great influence on the driving sensation, and since 1 Herk between the front and rear wheels is affected by the torque distribution ratio of the four-wheel drive 1 to the front wheel, the driver's driving In order to create driving conditions that suit the user's senses, it is necessary to control the torque distribution ratio between the front and rear wheels.Therefore, in order to achieve the above object, this invention reduces the driving force output from the transmission. In addition to distributing torque to the front and rear wheels, in order to control the torque distribution rate to the front and rear wheels by changing the transmission torque capacity by the friction engagement means based on the driving conditions, it is necessary to control the vehicle speed or the transmission. A method characterized by determining a shift pattern performed by a transmission according to an output shaft rotation speed and a throttle opening, and changing the transmission torque capacity ω according to the obtained shift pattern. be.

Further, in the present invention, a shift pattern preset for electronic control equipment in an electronically controlled transmission can be used as a shift pattern that is the basis for increasing/decreasing the transmission torque capacity.

Further, according to the present invention, the transmission torque capacity can be increased in the case of a shift pattern in which the shift-up timing is shifted toward a higher vehicle speed.

Operation In this invention, first, a shift pattern during driving is determined. In electronically controlled automatic transmissions, this may be done by using a shift pattern selected by the driver from among preset shift patterns; in other cases,
For example, by detecting the throttle opening and vehicle speed, and comparing the gear position at that point with a predetermined reference gear position (by determining the gear shift pattern being executed). Then, the transmission torque capacity by the friction engagement means is increased or decreased depending on the obtained shift pattern.For example, in the case of a shift pattern in which a relatively low gear is accelerated to a high speed, the transmission torque capacity by the friction engagement means is In the case of a shift pattern in which the transmission torque capacity is increased to ensure stability in handling even if a certain degree of tight corner braking occurs, and on the other hand, in the case of a shift pattern in which upshifts are performed at a relatively early point in time, Friction 1g Torque transmitted by engagement means 8
This lowers the steering wheel to prevent tight corner braking from occurring.

Example Next, the method of the present invention will be explained based on examples.

FIG. 1 is a flowchart showing an example of the method of the present invention, and the method shown here is implemented, for example, with the apparatus shown in FIGS. 2 and 3.

That is, in FIG. 2, 1 indicates an internal combustion engine,
The internal combustion engine 1 is installed vertically at the front of a vehicle, and a vehicle automatic transmission 2 and a four-wheel drive transfer device 3 are connected in sequence to the rear of the internal combustion engine 1.

The automatic transmission 2 for a vehicle includes a hydraulic torque converter 5 of a general structure provided in a converter case 4 and a gear type transmission device 7 provided in a transmission case 6.
and an input member 8 of the hydraulic torque converter 5 provides an output +? of the internal combustion engine 1 (not shown). 1ull (
The internal combustion engine 1 is connected to the crankshaft (crankshaft) so that the rotational power of the internal combustion engine 1 is applied to the transmission 7 via the hydraulic torque converter 5.

The transmission 7 is a transmission configured with a planetary gear mechanism or the like, similar to those commonly used in the past, and
The hydraulic control device 9 is controlled by a control device 45, which will be described later, and is configured to shift to a plurality of gears according to a predetermined shift pattern.

The four-wheel drive transfer device 3 has a planetary gear type center differential device 10 for full-time 4WD (continuous four-wheel drive), and the center differential device 10 receives rotational power from the transmission 7. It has a sharp edge 11 as an input member, a planetary pinion 12 held by a carrier 11, a sun gear 13 and a ring gear 14 that mesh with the planetary pinion 12, and the ring gear 14 is connected to a rear wheel drive shaft 15. , the sun gear 13 is connected to a sleeve-shaped front wheel drive intermediate '11116 that is concentric with the rear wheel drive shaft 15.

The four-wheel drive transfer device 3 is provided with a front wheel drive shaft 17 parallel to the front wheel drive intermediate shaft 16. N116 and front wheel drive shaft 17 are connected by an endless chain 20 that meshes with sprockets 18, 19 attached to each.

The four-wheel drive transfer device 3 has a built-in hydraulically operated differential control clutch 21 as a differential limiting device that selectively connects the sun gear 13 and the ring gear 14. Wheel drive transfer device 3
It is operated by a hydraulic control device 22 provided in the.

As shown in FIG. 3, the differential control clutch 21 is a hydraulic servo-type wet multi-disc clutch, and the hydraulic servo device 3
The center differential device 1 is moved to the right in the figure against the spring force of the servo piston 37 or the return spring 38 by the servo oil pressure supplied to the oil stop 36 of 5.
The sun gear 13 and the ring gear 14 are connected to each other, and the transmitted torque is proportionally increased in accordance with an increase in the servo oil pressure supplied to the oil shaft 36.

The hydraulic control device 22 includes a pressure regulator valve 40 which receives hydraulic pressure from an oil pump 39 incorporated in the vehicle automatic transmission 2 and regulates the pressure to a predetermined hydraulic pressure, and an electromagnetic pressure regulator valve 40 which receives hydraulic pressure from the pressure regulator valve 40. A servo hydraulic control valve 41 is provided. The servo hydraulic control valve 41 has a port a connected to the oil port 36 of the hydraulic servo device 35, a hydraulic boat b to which hydraulic pressure is supplied from the pressure regulator valve 40, and a drain boat C. Port a is communicated with hydraulic boat b, and port a is communicated with drain boat C when the power is not energized. The servo hydraulic control valve 41 is given a pulse signal with a predetermined duty ratio from the control device 45, whereby the servo hydraulic control valve 4
1 supplies large servo hydraulic pressure according to the duty ratio to the oil supply 36 of the hydraulic servo device 35.

One end of a rear propeller shaft 24 is connected to the rear wheel drive @15 by a universal joint 23.

One end of a front propeller shaft 26 is connected to the front wheel drive q1] 17 via a universal joint 25. The propeller @ 26 to the front 1 is arranged almost parallel to the III line of the vehicle automatic transmission number 2, and is connected to the input shaft of the front differential device fft 30 by the universal joint 27 and the intermediate connecting shaft 28 at the other end. The drive pinion shaft 31 is connected to one end of the drive pinion shaft 31. The drive pinion shaft 31 is rotatably supported by a differential case 32 integrally formed with an oil pan 29 made of U+ iron of the internal combustion engine 1.

A drive pinion 33 made of a bevel gear is provided at the end of the drive pinion shaft 31, and the drive pinion 33 meshes with a ring gear 34 of the front differential device 30.

The hydraulic control device 9.22 is an electric type IItlO device 4.
It operates based on a control signal from 5 to control the gear shift of the transmission 7 and control the transmission torque of the differential control clutch 21. The control device 45 includes a microcomputer with a general structure, and controls vehicle speed V, steering angle O,
Signals such as throttle opening degree 0, manual shift position, front wheel rotation speed, rear wheel rotation speed, and brake signal are inputted. Here, the vehicle speed V is a front wheel drive l1111 sensor that detects the rotation speed of the rear wheel drive shaft 15.
Sensor that detects rotation speed of 7 or intermediate 1 for front wheel drive
The output signal may be an output signal from any of the sensors for detecting the rotation speed of the 11116, and reliability will be higher if output signals from all of these sensors are employed.

The control device 45 basically hydraulically controls the control signal for controlling the gear shift of the transmission 7 according to a predetermined shift pattern according to the manual shift range, the vehicle speed V, and the throttle speed θ. A pulse signal of a predetermined duty ratio is outputted to the small hydraulic pressure control valve 41 for outputting it to the device 9 and controlling the transmission torque capacity of the differential control clutch 21 according to the gear position and throttle opening θ. Furthermore, when the vehicle is in an unsteady state such as turning or slipping, it is configured to output a pulse signal with a duty ratio corresponding to the unsteady condition to the servo hydraulic control valve 41.

Here, three types of shift patterns are preset: a power shift pattern, an economy shift pattern, and a normal shift pattern, and the B/F no shift 1~ pattern shifts up to accelerate to high speed in a relatively low gear, Therefore, it is a pattern that drives with high torque overall, and an economy shift pattern is a pattern in which shifts from 1 to 1 are carried out finely at relatively low vehicle speeds, and a normal shift pattern is a pattern in which shifts are performed at a relatively constant speed or at a relatively low speed. This is a pattern in which upshifts are performed in response to an increase in Furthermore, the transmission torque capacity of the differential control clutch 21 is controlled based on the above conditions, and its value is set larger in the power shift pattern than in other shift patterns.

More specifically, as shown in FIG. 4, at a predetermined throttle angle θ or more, the transmission torque capacity ff1Tc in the power shift pattern is set to be larger than the transmission torque capacity TC in the Tsukuda shift pattern. ing.

Next, an example of the control method of the present invention for the above-mentioned apparatus will be described. As shown in FIG. 1, first, it is determined whether the shift pattern is a shift pattern or a power shift 1-pattern (step 100). In the case of an electronically controlled automatic transmission, this can be done by determining whether the shift pattern selected by the driver or the power shift pattern is selected. It is sufficient to judge the timing of the upshift based on the relationship between the throttle opening degree and the vehicle speed at that time, and to determine whether or not the power shift pattern is adopted. If the result of this judgment is "yes", it is determined whether the transmission torque capacity by the differential control clutch 21 has reached C or the transmission torque capacity according to the power shift pattern =]-cp ( Step 101). If the judgment result is "yes", the control is terminated, and if the judgment result is "no", the transmission torque capacity ff1Tc is set to the transmission torque capacity Tcp according to the power shift pattern (step 102)
. In other words, the transmission torque capacity is increased. Specifically, this can be done by changing the pulse signal output to the servo hydraulic control valve 41 to increase the duty ratio.

On the other hand, if the determination result in step 100 is "no", that is, if the power shift pattern is not established,
It is determined whether the transmission torque capacity ff1Tc is equal to the transmission i to torque capacity ff1Tce corresponding to the economy shift pattern (step 103).

If the judgment result is "yes", the control is terminated, and if the judgment result is "no", the transmission 1 to
1Tc is set to the transmission torque capacity ω-1ce according to the economy shift pattern (step 104). This operation may be performed by changing the pulse signal to the servo hydraulic control valve 41 to reduce its duty ratio.

Therefore, according to the above method, in the case of a power shift pattern in which the vehicle is driven with high torque, the differential control clutch 21
As a result, the transmission torque capacity ff1Tc becomes larger and the differential restriction is strengthened, that is, the torque distribution ratio to each of the front and rear wheels becomes close to the dynamic distribution within the vehicle, and as a result, tight corner braking phenomenon may occur, but the operation is improved. Safety is improved and the driving performance required by the driver can be met. On the other hand, in the case of the economy shift pattern, the torque capacity Φ transmitted by the differential control clutch 21 becomes smaller and the differential restriction becomes weaker, that is, the center differential device approaches a free state, and as a result, tight corner braking occurs. This ensures that the smooth and easy driving conditions desired by the driver are achieved.

The embodiments described above are taken as examples of four-wheel drive devices based on FR vehicles (front engine rear wheel drive vehicles), or this invention is based on FF vehicles (front engine front wheel drive vehicles). The present invention can also be applied to a four-wheel drive device, and an example thereof will be explained with reference to FIG. In FIG. 5, the internal combustion engine 50 is placed horizontally at the front of the vehicle.
A vehicular automatic transmission 51 and a four-wheel drive transfer device 52 are connected to the vehicle 0 in this order. Automatic gear shift I for vehicles
a51 is a general @-made fluid type 1 to lux converter 53
and a transmission 18.

The hydraulic torque converter 53 is connected to the output shaft 55 of the internal combustion engine 50 by an input member 53a, and
Rotational driving force is applied from the output member 53b.
is connected to a transmission 54.

Transmission 54 may be of any conventional construction, including a planetary gear arrangement, and is adapted to change between a plurality of forward gears and at least one reverse gear.

The speed change control of the transmission device 54 is performed using hydraulic pressure by a hydraulic control device 56.

The four-wheel drive transfer device 52 has a hint differential device 57. The center differential device 57 is rotatably held by a differential case 60 integrally provided with an input gear 59 that meshes with an output gear 58 of the transmission 54, and a pinion shaft 61 provided in the differential case 60, and is opposed to each other. It has a pair of disposed differential pinions 62, and a side gear 63 for rear export force and a side gear 64 for front wheel output that mesh with these differential pinions 62.

A rear export force gear 65 is connected to the rear export force side gear 63, and the rear export force gear 65 has a rear wheel drive 1fI11.
166 rear wheel drive gears 67 are in mesh.

A hollow front wheel drive lN16 is installed in the front wheel output night drive 64.
8 are directly connected.

A differential case 60, which is an input member of the center differential device 57, and a front wheel drive @68, which is one output member of the center differential device 57, are connected to the four-wheel drive transfer device 52 so as to selectively transmit torque. A hydraulically operated differential control clutch 69 is provided as a differential limiting device. The differential control clutch 69 is a hydraulic multi-plate wet type clutch, and proportionally increases the amount of transmitted torque B in accordance with an increase in the hydraulic pressure supplied to a hydraulic servo device (not shown). It is supposed to be done.

The supply of servo hydraulic pressure to the hydraulic servo device is performed by the hydraulic control unit 1ff70.

The hydraulic control device 70 is provided with a pulse signal having a predetermined duty ratio from the control device 71, and supplies servo hydraulic pressure having a size corresponding to the duty ratio of the pulse signal.

The front wheel drive shaft 68 is a front differential device 72
The differential case 73 is connected to the differential case 73. The front differential device 72 has a pinion @11
It has two differential pinions 75 which are rotatably held in the differential case 73 by 74 and are arranged opposite to each other, and a right side gear 76 and a left side gear 77 that are meshed with these differential pinions 75. A right side axle 78 is connected to the left side axle 78, and one end of a left side axle 79 is connected to the left side gear 77, respectively.

The hydraulic control devices 56 and 70 operate based on control signals from an electric control device 71. As in the embodiment described above, signals such as vehicle speed V, steering angle e, throttle opening θ, manual shift position, front wheel rotation speed, rear wheel rotation speed, brake signal, etc. are input to the control device 71, respectively. There is.

The control device 71 basically hydraulically controls a control signal for controlling the gear shift of the transmission 54 according to a predetermined shift pattern according to the manual shift range, the vehicle speed V, and the throttle opening θ. Output to the device 56,
It also outputs a pulse signal with a predetermined duty ratio to the servo hydraulic control valve to control the transmission torque capacity of the six differential control clutches according to the gear position and throttle opening θ, and furthermore, it outputs a pulse signal with a predetermined duty ratio to the servo hydraulic control valve, and also During steady state, it is configured to output a pulse signal with a duty ratio corresponding to the unsteady condition to the servo hydraulic control valve.

Three types of shift patterns are preset: a power shift pattern, an economy shift pattern, and a normal shift pattern.
The economy shift pattern is a pattern in which the vehicle is shifted up to accelerate to a high speed in a relatively low gear, and therefore runs with high torque overall.An economy shift pattern is a pattern in which the vehicle is shifted up finely at relatively low speeds. Further, the normal shift pattern is a pattern in which an upshift is performed in response to an approximately constant increase in vehicle speed. Further, the transmission torque capacity of the differential control clutch 69 is controlled based on the above conditions, and its value is set to be larger in the power shift pattern than in other shift patterns.

Even a four-wheel drive vehicle configured as described above can be controlled in the same manner as in the embodiment described above.

Note that each of the above embodiments is intended for a full-time four-wheel drive vehicle equipped with a center differential device, but the method of the present invention is capable of switching between four-wheel drive and two-wheel drive by engaging and disengaging the tardge. The present invention can also be applied to a part-time four-wheel drive system in which the clutch is slip-controlled to control the torque distribution ratio between the front and rear wheels.

As described in detail, according to the method of the present invention, by controlling the degree of differential restriction in accordance with the shift pattern, the driving condition can be established in accordance with the driver's requirements, and the driving stability can be ensured. It is possible to improve fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the method of the present invention;
Figure 2 is a simplified diagram of the equipment targeted by this method, Figure 3 is a simplified diagram of the differential control clutch control system, and Figure 4 shows the change in transmitted torque capacity according to the throttle opening in an economy shift pattern. FIG. 5, which is a diagram showing the case of the above case and the case of the power shift mill pattern, is a simplified diagram of another four-wheel drive device targeted by the method of the present invention. 3.52... Four-wheel drive transfer, 10,57
...Center diff 7 ratio A full device, 21,69
... Differential control clutch, 41 ... Servo hydraulic control valve, 45.71 ... Control device.

Claims (3)

[Claims] (1) The driving force output from the transmission is distributed to the front and rear wheels, and the torque distribution ratio to the front and rear wheels is changed by changing the torque capacity transmitted by the frictional engagement means based on the driving conditions. In order to control the vehicle speed, the pattern of gear changes performed by the transmission according to the speed of the transmission output shaft and the throttle opening is determined.
A method for controlling a four-wheel drive device for a vehicle, characterized in that the transmission torque capacity is changed in accordance with the obtained shift pattern. (2) The transmission is an electronically controlled transmission controlled based on an output signal from an electronic control device, and the electronic control device has a plurality of selectable shift patterns. A method for controlling a four-wheel drive device for a vehicle according to claim 1, wherein the four-wheel drive device for a vehicle is set. (3) The transmission torque capacity is increased in the case of a second shift pattern in which the upshift timing is shifted to a higher vehicle speed side than in the first shift pattern. The method for controlling the four-wheel drive device for a vehicle described above.