JPH0238144A - Variable speed controller of four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To prevent the resistance of specific portion from being deteriorated when differences arise between respective speeds of four wheels, by limiting the up-shift of an automatic transmission during idle running of the wheels, and also permitting said limitations in accordance with the types of the wheels under idle running conditions. CONSTITUTION:A four-wheel driving device including an engine 10, an automatic transmission 20 center diff.device 30, a front diff.device 40, a transfer device 50, a rear diff.device 60, a differential speed controlling device 70, a controller 80 and various types of input units 90 has a differential speed generating portion A to be protected, which corresponds to a portion at which the extending member 42A of a diff.case 42 and a differential speed side front wheel axle shaft48 are in sliding contact with each other. In this case, in the controller 80, idle running conditions of wheels are detected according to respective outputs of rotating number sensors 93-96, and the up-shift movement of the automatic transmission 20 is limited when idle running is detected. Also, the degree of limitation of the up-shift movement is varied in accordance with the types of wheels under idle running conditions.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a transmission control device for a four-wheel drive vehicle equipped with an automatic transmission and a differential device capable of allowing differential differential between front and rear wheels.

[Prior Art] The engagement state of a friction engagement device is selectively switched by operating a hydraulic control device, and one of a plurality of gears is automatically achieved depending on the running state of the vehicle. Automatic transmissions for vehicles configured as described above are already widely known. Conventionally, automatic gear shifting has been performed according to a gear shifting diagram predetermined based on engine load (for example, throttle opening) and vehicle speed. Detection of the vehicle speed at this time is generally performed by detecting the rotational speed of the driving wheels, specifically, the rotational speed of the output shaft of the automatic transmission. By the way, when the driving force from the engine cannot be fully utilized as driving force for the vehicle on a low μ road, that is, when the vehicle is stuck, the drive wheels spin violently. In this case, since the resistance of the road surface to the drive wheels is extremely small, the rotation of the drive wheels easily increases. Even in this state, the automatic transmission performs gear changes according to a predetermined shift diagram. However, since "vehicle speed" is detected by detecting the output shaft rotation speed of the automatic transmission (average rotation speed of the four wheels), even if the vehicle is actually stopped, As long as the drive wheels are rotating, it is assumed that "vehicle speed" is being generated and the automatic transmission continues to change gears (upshift). The rotation becomes higher and higher. Since the vehicle does not move, if the driver continues to press the accelerator strongly, the vehicle speed on the meter may become extremely high in a short period of time. By the way, when the drive wheels are idling in this way, the friction coefficient μ of the road surfaces that the drive wheels contact generally differs, and the loads applied to the drive wheels and the radii of the drive wheels also differ. There is a difference in the rotation speed of the left and right wheels. In the worst case, the number of rotations on either the left or right side will be zero, and only the opposite side will rotate. For example, when only one wheel is rotating and the vehicle speed is 50 km/h, the idling drive wheel is rotating at the same speed as when the vehicle speed is 200 km/h. (for wheel drive vehicles). Conventionally, in such cases, considering that the durability of the differential unit (differential device) for final deceleration photography decreases, if one of the left and right wheels is slipping, automatic transmission gear shifting has been carried out. (Problems to be Solved by the Invention) A technique has been proposed to suppress the upshift and ensure the durability of the differential section (Utility Model Application No. 61-173216). [Problems to be Solved by the Invention] However, this application 1986-1732'16 focused on the durability of the so-called differential device, and therefore, the speed change limit of the automatic transmission is executed depending on the differential state of the left and right wheels. However, in recent years, four-wheel drive vehicles have become popular, but in these four-wheel drive vehicles, there is a differential device between the left and right front wheels, a differential device between the left and right rear wheels, or a differential device between the front and rear wheels. In addition to the durability of the differential (differential device between the wheels), there are quite a few areas where durability is a problem due to the occurrence of differential motion.In other words, in the case of two-wheel drive, the occurrence of differential motion between the wheels The parts where relative rotation occurs are mainly limited to the differential device.However, in the case of a four-wheel drive vehicle, in addition to the members that rotate at the rotation speed of each wheel, for example, the parts that rotate at the average rotation speed of the four wheels, A member that rotates at the average rotation speed of the front wheels,
There are now parts that rotate at the average rotational speed of the rear wheels, and due to space issues or requests to reduce weight, bearings are not always used to connect the parts where these parts come into contact. There are things I can't do. In this case, these parts will be in so-called sliding contact. Even if it is a sliding contact, under normal conditions it is a "differential"
Since there is no relative rotation unless this occurs, there is no problem in terms of durability. However, when one wheel or two wheels are spinning violently, large relative rotation occurs in these parts as well, which poses a problem in terms of durability. However, these problems cannot always be solved by looking only at the differential between the left and right wheels. For example, if the two front wheels are both spinning at approximately circumferential speed, there will be little differential movement between the left and right front wheels, but the average rotation of the four wheels and the average rotation of the front wheels (or rear wheels) If there is a sliding contact with a rotating member, this part will be placed under severe conditions. However, this situation cannot be handled by detecting the differential movement between the left and right front wheels. [Object of the Invention] The present invention has been made in view of the above-mentioned problems, and is a problem in which one or two wheels of a four-wheel drive vehicle spins idle.
A transmission control system for four-wheel drive vehicles that can prevent the parts that generate differentials (including the differential device) from being subjected to severe conditions due to this idling, and the durability of the parts that generate differentials decreases. The purpose is to provide equipment. [Means for Solving the Problems] The present invention provides a speed change control device for a four-wheel drive vehicle equipped with an automatic transmission and a differential device capable of allowing differential movement between the front and rear wheels. As shown in the summary, there is a means for detecting wheel slippage, a means for limiting upshifting of the automatic transmission when the wheels are slipping, and a means for limiting the upshifting based on the type of wheel slipping (slipping). The above-mentioned object is achieved by providing means for carrying out the execution according to the number of wheels (including the concept of the number of wheels in the vehicle).

[Effect]

As described above, automatic transmissions generally regard the rotation of the drive wheels as generation of vehicle speed even when the vehicle is not moving, and perform gear changes according to a predetermined shift diagram. in general,
If the vehicle does not move, the driver will continue to press the accelerator,
The idling rotation speed of the idling drive wheels easily increases. Then, the automatic transmission determines that the vehicle speed has increased and continues shifting (upshifting), so the spinning drive wheels start rotating at higher speeds, and the rotation difference between them and the stopped wheels increases. A vicious cycle occurs. In the present invention, the speed change (upshift) of the automatic transmission is restricted by detecting such a state in which the wheels are idling, so that the speed of the wheel idling increases due to gear shifting. can be prevented. In addition, due to the restriction on gear shifting, the engine speed increases proportionally as the idling speed of the drive wheels increases.
This has the effect of suppressing the driver's depression of the accelerator pedal, and it becomes possible to prevent further high differential movement (or high sliding movement) in the differential generating portion. In this case, in the parts that are subjected to severe conditions due to this high differential (high sliding), the idling speed is the same depending on whether one or two wheels are idling, or whether the front or rear wheels are idling. Even if the average rotational speed of the four wheels is the same, the difference in the rotational speed of the differential generating portion will differ. This refers to the type of idle wheels (including the concept of the number of idle wheels)
This means that the severity of the durability of the part to be protected changes. In view of these points, the present invention detects the type of idling wheel,
Since the speed change of the automatic transmission is limited according to the type, appropriate control can be performed. In other words, when only the protection of the differential generating part is considered, the differential generating part is under the most severe condition (for example, when only one wheel is idling, the differential generating part is under the most severe condition). If only one wheel is idling), it would be a good idea to limit the upshifts of the automatic transmission to ensure safety.At least the purpose of limiting upshifts is to ensure durability. can be achieved. However, if consideration is given to protecting the differential-generating portion and escaping from a slip state, it may be more preferable to actively perform an upshift to reduce the torque that reaches the drive wheels. Therefore, as long as there is still some margin in the durability of the differential generating portion, it is desirable to not limit upshifting as much as possible. The present invention is adapted to limit upshifts according to the type of idling wheels, so it is well suited to this situation and maximizes the possibility of escaping from slipping while ensuring the durability of the differential generating part. It is maintained at a high level.

Embodiment 1 An embodiment of the present invention will be described in detail below based on the accompanying drawings. FIG. 2 is a skeleton diagram showing a four-wheel drive system for a vehicle to which the present invention is applied. This four-wheel drive device includes an engine 10, an automatic transmission 20,
Center differential device 30. Front differential device 40, transfer device 50, rear differential device 60, differential control clutch 70. ! It is equipped with an IJ control device t801 and various input systems 90. The engine 10 is placed horizontally at the front of the vehicle. The output of engine 10 is transmitted to automatic transmission 20. Automatic transmission! 120 has a well-known configuration that includes a hydraulic torque converter 21 and an auxiliary transmission section 22, and automatically switches between four forward speeds and one penetration speed by a hydraulic control section 23. Highest speed of 4 forward speeds (4th speed)
is an overdrive stage. As will be described later, this gear change is performed according to a speed change map of the rotational speed of the output gear 24 of the automatic transmission and the accelerator opening as shown in FIG. 6(A). Hydraulic control section 2
3 is controlled by commands from the control 11 device 80 (speed commands according to the map). The power that has passed through the automatic transmission 1120 is transmitted to the input gear 31 of the center differential device 30 via the output gear 24. The center differential device 30 has this input gear 31
The differential case 32 is integrated with the differential case 32. The differential case 32 has a pinion shaft 33, two differential pinions 34, 35, a side gear 36 for rear export force, and a side gear 37 for front export force using a well-known meshing configuration.
is installed. The rear export force side gear 36 is connected to a transfer gear 51 of a transfer device 50. The front export force side gear 37 is connected to a hollow front wheel drive shaft 41. The front differential device 40 includes a differential case 42 that is integrated with the front wheel drive shaft 41. This differential case 42 has a pinion shaft 43, two differential pinions 44, 4, and
5. A left front wheel output side gear 46 and a right front wheel output side gear 47 are attached. A left front wheel axle 48 is connected to the left front wheel drive side gear 46, and a right front wheel axle 49 is connected to the right front wheel output side gear 47, respectively. On the other hand, the transfer device 150 includes a transfer gear 51 connected to the rear export force side gear 36 of the center differential device 30, a driven pinion 52 that meshes with the transfer gear 51, and a driven pinion 52 and a propeller shaft 53. A transfer output rotating gear 54 that rotates integrally is provided. The transfer output gear 54 is the rear differential device 6
Connected to 0. The rear differential device 60 includes a differential case 61 in which a ring gear that meshes with the transfer output gear 54 is integrally formed. This differential case 61 has a pinion shaft 62 and two differential pinions 63 and 64 with a well-known meshing configuration.
, a left rear wheel output side gear 65 and a right rear wheel output side gear 66 are attached. The left rear wheel output side gear 65 is connected to the left rear wheel axle 67, and the right side/rear output power side gear 66 is connected to the right rear wheel axle 68. The differential control clutch 70 is connected to a differential case 32 which is an input member of the center differential device 30.
and the front wheel drive shaft 41, which is the output member of the center differential device 30, are connected in a torque transmission relationship. The differential control clutch 70 is mainly composed of a wet multi-disc clutch section 71 and a hydraulic control section 72 that controls the wet multi-disc clutch section 71. As shown in FIG. 3, a hydraulic servo section 73 is attached to the multi-disc clutch section 71. This hydraulic servo section 73
When servo oil pressure (clutch oil pressure) is supplied to the oil chamber 74, the servo piston 75 moves to the right in the figure against the spring force of the return spring 76. As a result, the multi-plate clutch section 71 is pressed, and the differential case 32 and the front wheel drive shaft 41 are connected in a torque transmission relationship via the multi-disc clutch section 71. Furthermore, the transmission torque capacity is proportionally increased or decreased in accordance with an increase or decrease in the servo oil pressure supplied to the oil chamber 74. The supply of servo hydraulic pressure to the oil chamber 74 of the hydraulic servo section 73 is performed by the hydraulic control section 72. The hydraulic control unit 72 includes a line pressure control valve 77 that adjusts the hydraulic pressure of an oil pump 74 incorporated in the automatic transmission 20 to a hydraulic pressure according to the engine load, and an electromagnetic servo hydraulic control valve 78. The servo hydraulic control valve 78 includes a boat a connected to the oil chamber 74, a hydraulic boat b supplied with line hydraulic pressure from the line hydraulic control valve 77, and a drain boat C. This servo hydraulic control valve 78 connects boat a to hydraulic boat B and b when energized, and connects boat a to drain boat C when not energized. The servo hydraulic control valve 78 is controlled by the control device 80 applying a pulse signal with a predetermined duty ratio. As a result, servo oil pressure having a magnitude corresponding to this duty ratio is supplied to the oil chamber 74, and a differential limiting force corresponding to this duty ratio is generated. The control device 80 controls the hydraulic pressure control sections 23 and 72 according to each input signal from the input system 90. This control device 80 includes information on the off-accelerator opening from the throttle opening sensor 91, manual shift range information of the automatic transmission 20 from the manual shift position sensor 92, and information on the left and right front wheels from the front wheel rotation speed 93.94. Rotation speed information, left and right rear wheel rotation speed information from rear wheel rotation speed sensors 95 and 96, and vehicle steering angle information from a steering angle sensor 97 are input. The control device 80 also receives vehicle speed information (rotational speed information of the output gear 24: average rotational speed information of the four wheels) from the vehicle speed sensor 98.
Information is also entered. Furthermore, information regarding the driver's request for a differential control state is also input to the control device 80 from the differential select switch 99. The differential select switch 99 allows selection of two modes: rFREE (free) and rAUTo (auto). In the FREE mode, the clutch oil pressure pc of the differential control clutch 70 is rFREE.
J, that is, zero (differential permission allowed). In the AUTO mode, the clutch oil pressure is automatically changed depending on the vehicle driving condition. The control device 80 operates the automatic transmission 20 according to the shift pattern shown in FIG. A control signal for gear position control is output to the hydraulic control unit 23.Due to the nature of the map, when the accelerator opening θ^ is θA1, the slip becomes intense and the (apparent) vehicle speed V changes from, for example, V to V2. If this happens, the automatic transmission 20 is shifted from the first gear to the second gear because the vehicle running state has changed from point P to point Q. FIG. 4 shows the skeleton of FIG. 2. This figure shows the actual structure near the front wheel differential device 40, and the reference numerals in the figure are the same as those in FIG. 2. The part indicated by the symbol A corresponds to the differential generation part to be protected in this embodiment.This part A is the part where the extension member 42A of the differential case 42 and the left front wheel axle 48 slide. This differential generation portion A is 3・N A / 4 when only the front left wheel is idling, when the number of rotations of the idling wheels is N^.
■When two front wheels or two rear wheels are idling at N p, N^/2, ■When only one rear wheel or right front wheel is idling, N
A relative rotation (differential) of ^/4 is generated. Therefore, even if the idling rotation speed NA is the same (or even if the four wheels have the same average rotation speed), the severity of the durability in this differential generation portion A will be different. Therefore, when restricting the upshift of the automatic transmission, the degree (content) of the restriction on the upshift is changed depending on the type of wheel that is spinning. FIG. 5 shows the control flow. In the control flow shown in FIG. 5, the present invention is activated only when the accelerator opening θ^ is greater than or equal to the predetermined value 61, braking is not applied, and the vehicle speed (average of four wheels) is less than or equal to the predetermined value V1. is now applicable. The purpose of executing this control only when the accelerator opening degree θ^ is equal to or greater than the predetermined value 61 is to execute this control only when the accelerator is depressed. Therefore, the predetermined value θ1 is set to a value near zero. This is because it is considered that when the accelerator is released, there will be no state where this control is applied. Furthermore, the reason why the condition is that the vehicle is not in a braking state is to prevent the present invention from being applied in cases where the wheels are locked during braking. The condition that the vehicle speed V is less than or equal to the predetermined value V1 is to prevent this control from being applied when the vehicle temporarily goes off the rails at a high vehicle speed. However, these conditions are not essential conditions of the present invention, and therefore can be omitted. If these conditions are satisfied, the process proceeds to step 108, where the rotational speed of each of the four wheels is input. Thereafter, in step 110, it is determined whether only the left front wheel is idling. This judgment can be made, for example, by checking whether only the rotation speed of the left front wheel is greater than or equal to a predetermined value M1, and the rotation speeds of all the other three wheels are less than or equal to a predetermined value M2 (M2≦M1). can. When it is determined that only the left front wheel is idling, the differential generating portion A is placed in the most severe condition as described above, so the process proceeds to step 112 and the idling rotation speed N^ is set to the predetermined value N1.
It is determined whether or not the above is satisfied. If the idling rotation speed N8 is smaller than the predetermined value N1, there is no particular problem in terms of durability, so after performing the reset operation in step 119, the process proceeds to step 126 and the normal shift pattern, that is, as shown in FIG. The gear position is determined according to the shift pattern of A), and the process returns. On the other hand, if the idle rotation speed NA is equal to or greater than the predetermined value N1, the process proceeds to step 114, where the value of the flag F1 is determined. This flag F1 is set to 1 when only the left front wheel is rotating at a rotation speed higher than a predetermined value, and is set to 0 otherwise. If F+-0, the process advances to step 116 and the count of timer T^ reaches star 1.
~ and Fl is set to 1. This timer T^ is a timer for counting the duration of a state in which only the left front wheel is idling at a rotation speed of a predetermined value N1 or more. Once the flag F1 is set to 1, the flow proceeds from step 114 to step 120, where it is determined whether the timer TA is longer than the predetermined time T1. Predetermined time T
If it has not reached 1, it is returned as is. If only the left front wheel is idling at a rotational speed equal to or higher than the predetermined value N1 for a predetermined time T1 or longer, the process proceeds to step 122 and the gear position is changed according to pattern C, that is, the shift map pattern shown in FIG. 6(C). It is determined. This C pattern is
Since the pattern is such that the first gear is fixed regardless of the vehicle speed V and the accelerator opening θ^, no gear shifting is actually executed. Thereafter, the flag F1 is reset to zero (step 124), and the process returns. Before the timer 18 reaches the predetermined time T1, only the left front wheel is no longer idling (No determination in step 110), or the idling rotation speed N^ is lower than the predetermined rotation speed N.
If it is smaller than 1, the process does not proceed to step 114 and subsequent steps, so that the gear position determination based on the C pattern, that is, the execution of the strongest gear change restriction, is avoided. On the other hand, if it is determined in step 110 that only the front left wheel is not spinning, the process proceeds to step 210, where it is determined whether the two front wheels or the two rear wheels are spinning. If fL is disconnected because only the front two wheels or the rear two wheels are idling, the process advances to step 212 and the front two wheels are idle.
It is determined whether the rotational speed N of the wheel or the wheel that is spinning faster among the two rear wheels is greater than or equal to N2. Here, as will be described later, the set value of N2 differs depending on what kind of state is considered as the two-wheel idling state. When the rotation speed N day of the one with the faster idling width is N2 or higher, the process proceeds to step 214 and after, and when this state continues for a predetermined period of time or more, the B pattern is selected, which has a lower degree of shift restriction than the C pattern, i.e. The gear position is determined by a gear shift map pattern as shown in FIG. 6(B). The flow after this step 214 is the previous step 114.
Since these steps are exactly the same as the subsequent steps, similar steps will only be given the same reference numerals with the same last two digits, and redundant explanation will be omitted. Note that N2 is set to a value close to N1, for example, when considering a state in which the front two wheels are idling and the left front wheel is rotating at a much higher rotational speed than the right front wheel. However, when considering more general conditions, N2 was set to a value slightly larger than N1 because the durability of part A would be lower than when only the front left wheel is spinning. It's better. The reason for this is, for example, when both the left and right front wheels are rotating at N^ and the rear wheel is stationary, the relative rotation speed at part A is N^/2, which is 3N^ when only the left front wheel is spinning. This is because it is more relaxed than /'4. Furthermore, for example, if the left front wheel is rotating at N^, the right front wheel is rotating at 3N^, and the two wheels are stopped, the relative rotation speed at part A will be zero, so there will be no problem in terms of durability. do not have. In this embodiment, the power is applied when only the left front wheel is rotating, when only the front two wheels or the rear two wheels are rotating, and at other times. Change the degree of change (change the pattern of the shift map adopted)
As a result, the durability of part A can be improved, and while the durability is not a problem, the gear change (upshift) is performed as normally as possible, and the driving condition is such that it is as easy to escape from the slip state as possible. can be maintained. In addition, in this embodiment, 3
Two shift patterns were selectively adopted. However, for example, as shown by the broken line in FIG. 5, it is possible to detect only whether or not only the left front wheel, where the durability of part A is the most severe, is rotating, and based on this, it is possible to limit the speed change. It may also be possible to decide whether Furthermore, in this embodiment, two special shift patterns are selectively adopted depending on the type of slip width, but only one type of special shift pattern is used, and this special shift pattern is Two or more threshold values may be provided for selection, and the threshold value may be selected depending on the type of slip width. Furthermore, in this embodiment, attention was paid to portion A in FIGS. 2 and 4 to ensure its durability.
The present invention does not limit the differential generation portion to be protected. This is because the parts that are exposed to severe conditions in terms of durability differ depending on the vehicle. In this case, it goes without saying that specific speed change restrictions will be implemented depending on how the relative rotation occurring in the part to be protected changes depending on the type of wheel that is spinning. For example, in FIGS. 2 and 4, the differential control clutch 7
0 corresponds to the part where the member that rotates at the average rotational speed of the four wheels and the member that rotates at the average rotational speed of the front two wheels are connected, so only one of the four wheels is idling. than,
The condition where the front two wheels or the rear two wheels are not rotating is more severe in terms of durability. Therefore, when focusing on the durability of the differential control clutch 7o, it is better to have the two front wheels or two front wheels idling than to have only one of the four wheels idling. This results in a configuration in which the degree of speed change restriction is increased. Effects of the Invention As explained above, according to the present invention, by limiting the speed change of the automatic transmission, even if a differential occurs between the four wheels, the durability of specific parts is reduced. You will be able to prevent this from happening. In addition, since the speed change is limited according to the type of wheel that is spinning, it is possible to avoid limiting the speed change as much as possible as long as it does not cause problems in terms of durability, and upshifts can be performed as usual. By executing this, an excellent effect can be obtained in that it becomes possible to maintain a state in which it is easier to escape from the slip state.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the gist of the present invention. Figure 2 is a skeleton diagram showing the power transmission system of a four-wheel drive vehicle to which the present invention is applied. Figure 3 is a diagram of a center differential device. A skeleton diagram of a differential control clutch for limiting the differential. FIG. 4 is a sectional view showing the vicinity of the front wheel differential device. FIG. 5 is a flowchart showing the control procedure adopted in the above embodiment device. , FIGS. 6(A) to 6(C) are diagrams showing shift map patterns selectively adopted depending on the type of slip width. 10... Engine; 20... Automatic transmission; 30... Center differential device, 40... Front wheel differential device, 50... Transfer device, 60... Rear wheel differential device, 70... Differential control clutch, 80... Control device , 90...Input system, A...Differential generating part, 93.94...(Left and right) front wheel rotation speed sensor, 95.9
6... (left and right) rear wheel rotation speed sensor, 98... vehicle speed (
4-wheel average rotation speed) sensor.

Claims (1)

[Claims] (1) In a shift control device for a four-wheel drive vehicle equipped with an automatic transmission and a differential device capable of allowing differential movement between the front and rear wheels, there is provided a means for detecting wheel slip; A shift control device for a four-wheel drive vehicle, comprising: means for restricting upshifts of an automatic transmission; and means for restricting said upshifts according to the type of wheels that are spinning. .