JPH0257431A - Device for controlling speed change of automatic transmission of four-wheel-drive vehicle - Google Patents

Abstract

PURPOSE:To reduce a sense of slowness at the time of starting by determining the execution/non-execution of squat control in accordance with the permissions/ restriction of differential motion between front/rear wheels when rapid starting is required a the time of shifting to a traveling range. CONSTITUTION:A speed change control device has a means A for detecting a shift range and, when the shift range is switched over to a traveling range, the device carries out control so as to engage a frictional engaging unit for temporarily forming a high speed stage by a means E while permitting or restricting the differential motion between front/rear wheels. In this case, whether rapid starting is required or not is detected by a means B. The permitted/restricted condition of the differential motion between front/rear wheels is detected by a means C. When rapid starting is required, it is determined by a means D whether a control for temporarily forming a high speed stage is to be executed or not, in accordance with the permitted/restricted condition on the differential motion between front/rear wheels.

Description

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

The present invention relates to an improvement in a shift control device for an automatic transmission for a four-wheel drive vehicle, which is configured to improve shift control of an automatic transmission, and in particular, to improve durability of a drive system when switching from a non-driving range to a driving range. Regarding. (Prior Art) Japanese Patent Publication No. 50-709 discloses that in an electronically controlled automatic transmission, in order to reduce the shock when shifting from neutral range to drive range (N-)D shift),
A technique (sufauto control) for temporarily passing through a gear other than the first gear (R low gear) is disclosed. This auto control is a command to engage a frictional engagement device for forming a gear other than the first gear for a predetermined period of time (for example, about 0.8 seconds) after the N→D shift. , and then issues a command to establish the first gear. For example, to explain with reference to the engagement diagram shown in FIG. 5, when an N-D shift is performed, the shift would normally be completed by simply engaging the clutch C1, but in this case First, a command to engage clutch C+ and brake B2 is issued to temporarily establish second gear, and then brake B2 is released to return to first gear. As a result, the shock at the time of the N-+D shift can be alleviated to the extent that the gear ratio does not suddenly change, and the so-called suffocation phenomenon in which the tail portion of the vehicle sinks can be reduced. Further, Japanese Patent Application Laid-open No. 116160/1983 discloses a technique for executing this automatic control only when the vehicle speed is zero and the engine rotational speed is above a predetermined value. This is done considering that the N-D shift performed at high engine speeds generates a particularly large shock, and other N-D shifts are
-D shift is based on the design concept that it is better to give priority to quick start.

[Problem to be solved by the invention]

By the way, a so-called four-wheel drive drive system, in which the driving force of the engine is distributed to the four wheels to drive the vehicle, is becoming popular, but vehicles with this type of drive system have problems when starting suddenly. However, since the driving force is distributed to the four wheels, it is possible to start the vehicle without losing much more engine driving force than with conventional two-wheel drive. Therefore, since the driving force of the engine is not lost, in a 4-wheel drive vehicle, the shocking load torque that was avoided due to slip (drive loss) caused by exceeding the grip limit of the tires in a 2-wheel drive vehicle is directly transferred to the automatic transmission. As a result, the durability of these drive systems has become more of an issue than ever before. In this case, it is conceivable to detect whether or not a sudden start is requested and execute the above-mentioned quick auto control accordingly, but if the quick start control is simply executed together with the sudden start request detection, Some problems will arise. That is, when a sudden start is requested by the driver, the driver naturally requests quick start acceleration performance. However, since the SF auto control does not directly form the first gear, but instead passes through the high gear where the torque is reduced, the starting acceleration performance is sacrificed accordingly. Therefore, the automatic control needs to be performed within the minimum necessary range. (Objective of the Invention 1) The present invention has been made in view of such problems, and when the driver requests a sudden start when shifting from the non-driving range to the driving range, the automatic control is reduced to the minimum necessary level. The purpose is to provide a shift control device similar to automatic shifting for four-wheel drive vehicles, which is capable of improving the durability of the drive system and reducing the feeling of sluggishness when starting. do.

[Means for Solving the Problems] As shown in FIG. 1(A), the first invention includes means for detecting a shift range, and when the shift range is switched from a non-driving range to a driving range. An automatic transmission for a four-wheel drive vehicle configured to be able to engage a frictional engagement device for temporarily forming a high speed gear when the vehicle is in a high gear position, and to permit and limit differential movement between the front and rear wheels. In the speed change control WJ device, means for detecting whether or not a sudden start is requested; and means for detecting a differential permission/restriction state between the front and rear wheels;
means for determining whether or not to execute the temporary high-speed gear transition when it is detected that a sudden start is requested, depending on a permission or restriction state of a differential between the front and rear wheels; By preparing for this, the above objectives were achieved. The second invention, as summarized in FIG. In a shift control device for an automatic transmission of a four-wheel drive vehicle, which is configured to engage a frictional engagement device for forming a gear, and configured to allow and restrict differential movement between front and rear wheels, means for detecting whether or not the request has been made;
means for detecting permission or restriction state of differential movement between the front and rear wheels;
means for executing control for temporarily forming a high speed gear when it is detected that a sudden start is requested; By including means for changing the gear ratio of the stages, the above object is also achieved. In addition, in the present invention, "whether sudden start is requested or not"
The detection includes, for example, whether the accelerator opening is greater than a predetermined value, whether the throttle opening is greater than a predetermined value,
Alternatively, the determination can be made by detecting, for example, whether the engine speed has exceeded a predetermined value. [Function] In the first invention, a shift from a non-driving range to a driving range (for example, a shift from N-D, N→2, N→L, N-R, or P-+R; hereinafter, in this section, N-+0 If a sudden start is requested by the driver when a shift (represented by a shift) is performed, whether or not to perform automatic control is determined based on whether front and rear wheel differentials are permitted or restricted. ing. As a result, the automatic control can be executed only when a sudden start is requested when the differential between the front and rear wheels is limited. That is, for example, if the vehicle is a 4-wheel drive vehicle that allows you to select between a 2-wheel drive state and a 4-wheel drive state, in the 4-wheel drive state, the engine output is distributed to the four wheels, so the 2-wheel drive In this state, the driving force that would otherwise be lost due to slippage due to tires exceeding their grip limit is now used as driving force for the vehicle without being lost at all. In addition, when a sudden start occurs in a four-wheel drive state, a strong impact torque is applied due to the difference in load distribution between the front and rear wheels, resulting in strong power circulation, and this circulating torque causes However, each member of the drive system, including the automatic transmission, will be placed in a harsher condition. The first invention focuses on such points, detects the permission/restriction state of the differential between the front and rear wheels, and determines execution or non-execution of the auto control in accordance with this state. . As a result, the automatic control can be executed only when the drive system is in a truly severe condition, and good starting acceleration performance can be ensured at other times. In addition, in the first invention, due to its nature, it is premised that the "permission and restriction state of front and rear wheel differential" can be selected manually according to the driver's will or automatically by a signal reflecting the driving condition. . In this case, 4-wheel drive vehicles that can select the differential state of the front and rear wheels include those that can switch between 02-wheel drive state and 4-wheel drive state using a differential control clutch, 02-wheel drive state, 4-wheel drive state The drive state can be changed stepwise or continuously using a differential control clutch with variable transmission capacity. ■ A differential control clutch that has a center differential device between the front and rear wheels and either allows or prohibits the differential. ■A center differential device is provided between the front and rear wheels, and the differential permission/restriction (including prohibition) state can be changed stepwise or continuously using a differential control clutch with variable transmission capacity. However, the first invention is applicable to any of these types. That is, the first invention determines whether to execute the squat III control by paying attention to whether the differential between the front and rear wheels is permitted or restricted. In permanent four-wheel drive vehicles equipped with a center differential, the engine output is distributed to the four wheels, so the drive system is more durable than two-wheel drive vehicles due to less drive loss. You may be in a difficult situation. However, even with such a permanent four-wheel drive type vehicle, it is still necessary to select two-wheel drive or four-wheel drive depending on whether a differential between the front and rear wheels is permitted or not. The same "difference" occurs as with wheel drive vehicles. On the other hand, in the second invention, when a sudden start is requested by the driver during an N-D shift, the automatic control is basically executed, and at that time, it is determined which gear ratio the high speed stage is to be passed through. is changed depending on whether differential drive is permitted or restricted between the front and rear wheels. ``The meaning of the term ``permission of front and rear wheel differential, restriction state J'' is exactly the same as that in the first invention, and therefore the second invention also applies to a four-wheel vehicle equipped with a center differential device, for example. According to the second invention, when the differential between the front and rear wheels is limited, the high speed gear with a relatively small gear ratio (for example, third gear) is used as the high speed gear to pass through. As a result, the torque transmitted to the drive system becomes smaller, so that the harsh state of the drive system can be alleviated accordingly. According to the second invention, in cases where differential drive between the front and rear wheels is permitted, the drive system is not placed in such a severe condition that a gear with a relatively large gear ratio (e.g. 2nd gear) is selected.As a result, a relatively large torque is transmitted, so there is no need to reduce the vehicle's start acceleration performance too much, and it is possible to meet the driver's sudden start request as much as possible. (Embodiment) An embodiment of the present invention will be described in detail below based on the attached drawings. Fig. 2 is a skeleton diagram showing a four-wheel drive system for a vehicle to which an embodiment of the present invention is applied. This four-wheel drive device includes an engine 101, an automatic transmission 20,
Center differential device 30. Front differential device 401 transfer device 50, rear differential device 60. Differential control clutch 70. m control device 8
o, 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. The automatic transmission 20 includes a hydraulic torque converter 21 and an auxiliary transmission section 22, and has a well-known configuration in which a hydraulic control section 23 automatically switches between four forward speeds and one reverse speed. The highest speed (4th speed) of the four forward speeds is an overdrive speed. This automatic transmission 1120
The gear train is shown in Figure 4. Each gear stage is achieved by selectively engaging the brakes B0 to B3 and clutches C0 to C'2 shown in FIG. 4 by the hydraulic control section 23 as shown in FIG. The hydraulic control unit 23 is controlled by commands from the control device 80. The power that has passed through the automatic transmission 20 is transmitted via the output gear 24 to the input gear 31 of the center differential device 3o. 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 includes a binion shaft 33, two differential binions 34 and 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 and two differential pinions 44 and 4 with a well-known meshing configuration.
5. A left front wheel output side gear 46 and a right front output power 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 50 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. One 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 contact wheel output 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. Further, in accordance with an increase or decrease in the servo oil pressure supplied to the oil chamber 74, the transmission torque capacity is proportionally increased or decreased. The supply of servo hydraulic pressure to the oil chamber 74 of the hydraulic servo unit 73 is performed by the hydraulic control unit 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 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 throttle opening information from the throttle opening sensor 91, shift range information of the automatic shift 1120 from the manual shift position sensor 92,
Front wheel rotation speed information from front wheel rotation speed sensor 93, rear wheel rotation speed information from rear wheel rotation speed sensor 94, steering angle sensor 95
information on the steering angle of the vehicle from the vehicle, braking information from the brake sensor 96, information regarding the driver's permission to drive in overdrive (fourth gear) from the O/D switch 97, and information regarding the cooling water temperature from the engine cooling water temperature sensor 98. Information has been entered. When the O/D switch 97 is turned off or when the coolant temperature is low (during warm-up), the automatic transmission 20 is not shifted to the 4th gear, but is shifted between the 1st and 3rd gears. A gear shift is performed. In this embodiment, the slower one of the front wheel rotation speed and the contact wheel rotation speed is regarded as the vehicle speed. 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 and rAUTO. In the FREE mode, the clutch oil pressure of the differential control clutch 7o is set to rFREEJ, that is, zero (differential is permitted). In the AUTO mode, the clutch oil pressure is automatically switched and controlled as appropriate depending on the vehicle running condition. The control device 8o transmits manual shift range information and front wheel rotation speed information or rear wheel rotation speed information (
According to the vehicle speed information) and the throttle opening information, a control signal for controlling the gear position of the automatic transmission R20 is output to the hydraulic control unit 23 according to a predetermined shift pattern. In addition, the control unit @8o, depending on various running conditions of the vehicle,
Controls the clutch oil pressure of the differential control clutch 70. The configuration for arbitrarily controlling the clutch oil pressure of the differential control clutch 70 has already been described in detail. When the N-D shift is performed and the -shift auto control is not performed, hydraulic pressure is supplied only to clutch C+ in order to directly establish the first gear stage. However, if the execution conditions for the SAF auto control are satisfied, an engagement command to a higher gear (second gear or third gear) is issued, and then a command to the first gear is issued. In this case, the third gear, second gear, and first gear ( Auto control non-execution) is selected. In this embodiment, the conditions for executing the SF auto control are that, within a predetermined time T2p after shifting to the driving range, the vehicle speed V is below a predetermined value ■1, the throttle opening θ is above a predetermined value 61, and
It is assumed that all three conditions that the shift range is the travel range are satisfied. The reason is as follows. The condition that the vehicle speed ■ is less than the predetermined value v1 is as follows.
If the vehicle speed V is greater than or equal to a certain speed v1, or a certain speed V
If the value is 1 or more, there is no need to carry out SAF auto control, as the shock caused by the N-D shift and the durability of the drive system caused by the N-D shift are not so much of a problem. This is because it is better to form steps. Further, the reason why the throttle opening degree θ is set to a predetermined value of 61 or more is to execute the quick auto control only when a so-called sudden start is requested. That is, when the throttle opening degree θ is low, the vehicle does not start suddenly, so the shock at the time of N→D shift is small, and the durability of the drive system is not a problem. In this way, if there is not much benefit from executing the automatic control, it would be better to shift directly to the first gear without executing the automatic control to get the vehicle ready to start more quickly. Furthermore, the condition that the shift range be the driving range is because when the driver actually operates the shift lever, operations such as N-+D4N or N-+R→P are often performed. It is from. In such a case, even if the vehicle speed V is detected to be less than the predetermined value ■1 and the throttle opening θ is greater than the predetermined value θ, if the shift range is returned to the non-driving range at that stage, then For example, it is meaningless to perform auto control during N-4D shift. The condition that this shift range is the driving range is that this embodiment does not execute the auto control by considering only the state at the moment when the N-+D shift is performed, but rather the condition that the shift range is the driving range. This is a condition where MH occurs because the focus is on the current state. Further, if even one of the predetermined conditions does not hold, the first gear is immediately returned to. For the reasons mentioned above, if even one of the predetermined conditions does not hold, there is no point in further executing the auto control, so it is better to immediately establish the first gear. This is because it allows for a smoother start. A specific flowchart of this sudden start control is shown in FIG. 6 below. First, in step 101, the value of flag F2 is determined. This flag F2 is a flag that becomes 1 when the main control starts reducing the driving force due to the high-speed gear transit control, and becomes 0 otherwise. Initially, it is F2-〇, so the process advances to step 102. In step 102, the value of flag F1 is determined. This flag F+ indicates the state of the shift lever, and becomes F1=1 when there is a shift from the non-driving range to the driving range (D range, L range, and 2 range). In the initial state, F+-〇, so step 1
Proceed to 03 and check the state of the vehicle speed V. When the vehicle speed (2) is less than the vehicle speed V1, which is close to stopping, the process proceeds to step 104, where it is determined whether there has been a shift to the driving range, and the process proceeds to N-4D. Or if there is a shift such as N-jL, step 1
The program proceeds to step 05 to start counting the timer T^, sets Fl to 1 in step 106, and returns. This timer is used to detect the elapsed time since the shift to the driving range. Next, since F+=1, the process proceeds from step 102 to step 110 and subsequent steps. In steps 110 and 111, it is determined whether the state of the vehicle speed (2) has changed or the vehicle has been shifted to the non-driving range again before the start of the high speed gear shift under this control. When it is determined that the vehicle speed ■ has exceeded the predetermined value V1,
Proceeding to step 115, the first gear is directly established as usual. That is, control via the high speed stage is not executed. Thereafter, the count of timer T^ is reset in step 116, Fl is reset to zero in step 117, and the process returns. Further, when it is determined in step 111 that the gear has been shifted to the non-driving range again, the process proceeds to step 116, where the count of timer T^ is reset, and in step 117, the timer T^ is reset.
is reset to zero and then returned. That is, if the shift is from non-driving range to driving range to non-driving range in a short time, steps 111 to 116 are performed.
, and this control ends immediately. Note that the automatic transmission is in the non-driving range. Next, if YES is determined in both steps 110 and 111, the state of the throttle opening (corresponding to the accelerator opening) θ is checked, and the throttle opening θ is set to a predetermined value of 81.
If the above is the case, the process proceeds to step 113 and subsequent steps. In steps 113 and 114, the differential limiting force Fc between the front and rear wheels is used to change the content of the driving force reduction control by changing the gear ratio (changing the gears to be passed through) in steps 115, 119, or 125, respectively. Case classification is performed. That is, when the differential limiting force Fc is greater than the predetermined value Fc+ and θ≧θ1, the process proceeds to step 125 and the gear ratio is set to 1+ (for example, third gear). As a result, if a sudden start is requested when the differential between the front and rear wheels is strongly restricted, a shift to third gear is executed temporarily, so the torque increases by the smaller gear ratio. The durability of the drive system can be ensured. If Fc + <Fc≦FC2, the process proceeds to step 119 and sets the gear ratio to 12 (for example, second gear), which is closer to the a-gear than 11. This makes it possible to start the vehicle more quickly than by switching to the third gear while ensuring the durability of the drive system. Next, if FC<FC2, step 11
5, the first gear is directly established, and no control via the higher gear is executed. This is because even if the engine output is distributed to the four wheels, if a differential between the front and rear wheels is allowed, each wheel can slip even if a strong driving force is applied. This is because it is thought that the generation of circulating torque can be prevented to some extent and the drive system will not be in a particularly severe condition. Therefore, in this case, by directly establishing the first gear stage, it is possible to start the vehicle quickly. If the high speed stage control is not executed, the count of the timer T^ is reset in step 116, and set to Fl-0 in step 117, and this control is ended. On the other hand, if the process proceeds to the above-mentioned step 119 or 125, after setting F1=O in step 120, setting F2=1 in step 121, and then proceeding to the flowchart for determining whether to cancel this control. That is, after reaching F2-1, since the determination in step 101 is YES, the process proceeds to steps 126 and 127, and in step 126, the value of the throttle opening θ is set such that the durability of the drive system is not a problem. If it is determined that the value is θ2 or less, or if it is determined in step 127 that the vehicle is out of the driving range, the process proceeds to step 129 and subsequent steps to immediately end this control. In step 129, the gear ratio is returned to the normal state, ie, the first gear. In step 130, the count of the timer TΔ is reset, and in step 131, it is determined that the main control has ended, so F2 is reset to zero and the process returns. If YES in both steps 126 and 127, the process proceeds to step 128, where it is determined whether a predetermined time T3 has elapsed since the timer T^ started counting. Until the predetermined time T3 is not determined, the process returns as is, and the gear position of the gear ratio set in step 119 or 125 is maintained as it is. After that, when the timer T^ reaches the predetermined value 13 or more, step 12
9 to return to the normal gear, that is, the first gear. Thereafter, the count of the timer T^ is reset in step 130, and in step 131, it is determined that the main control has ended, so F2 is reset to zero and the process returns. According to this control flow, when a sudden start is requested,
If the restriction of the differential between the front and rear wheels is strong, the control is executed via the third gear, if it is relatively weak, the control is executed via the second gear, and if it is sufficiently weak, control is executed that omits the via the high gear. and second
Combination implementation of the invention) It is obvious that the present invention can be applied not only to the N-+D shift but also to other shifts from the non-driving range to the forward range. Also, for example, during NOR shift, high-speed reverse can be achieved by temporarily engaging the overdrive planetary gear mechanism 3 (brake Bo engagement and clutch Co release). It is also possible to apply the present invention. FIG. 7 shows a control flow according to the second embodiment. This control flow is an application of the first invention to a four-wheel drive vehicle that can selectively switch between two-wheel drive and four-wheel drive. In this type of 4-wheel drive vehicle, when the 2-wheel drive mode is selected, a differential between the front and rear wheels is completely allowed; Wheel differentials are completely prohibited. Therefore, the automatic control is executed only when four-wheel drive is selected. That is, in this control flow, first step 200
It is determined whether or not the vehicle is in four-wheel drive mode. As a result, only when it is determined that the vehicle is in a four-wheel drive state, the flow from step 201 onwards is entered. As for step 201Q and subsequent steps, since the configuration is almost the same as in the previous embodiment, the same steps will be given the same reference numerals, and redundant explanation will be omitted. However, in this control flow, steps 213 and 214 are slightly different in character from steps 113 and 114 in the previous control flow. 11 in the previous control flow
In No. 3 and No. 114, cases of high-speed gear selection were performed in these two steps based on the differential limiting force between the front and rear wheels. On the other hand, steps 213 and 214 in the control flow of FIG.
Depending on the elapsed time until the value becomes 1, high-speed stage selection is performed in different cases. The purpose of this is as follows. That is, in general, the friction engagement device in the hydraulic control unit 23 cannot be engaged at the same time as the shift to the drive range, and therefore, for a while after the shift to the drive range is performed.
The engine is still almost under no load. Therefore, if a sudden start is requested immediately after a shift to the driving range (if θ≧θ holds), the engine will be in an extremely high rotational state by the time the frictional engagement device engages. When the engagement of the SM engagement device is completed, the output of the engine in this high rotation state is transmitted to the drive system of the vehicle all at once. This condition is extremely severe in terms of the durability of the drive system. Therefore, in the control flow shown in Fig. 7, if a sudden start is requested immediately after a shift to the driving range, the gear is temporarily shifted to the 3rd or 4th gear with a small gear ratio. This reduces the torque applied to the drive system. On the other hand, if a sudden start is requested some time after the shift to the driving range is performed (if θ≧81 holds),
Since the frictional engagement device has already been engaged, the engine cannot rev up rapidly, and therefore a large output of the engine is not suddenly transmitted to the drive system. Therefore, in the control flow shown in FIG. 7, in such a case, the gear stage with a large gear ratio (for example, the second gear stage) is used to obtain better starting acceleration. In other words, the control flow shown in FIG. 7 determines whether or not to execute the auto control during a sudden start depending on the differential permission and restriction state of the front dominant wheels (2-wheel drive state or 4-wheel drive state). decided,
When the instant automatic control is executed, the high speed gear to be passed through is changed depending on how long it takes for θ≧θ1 to be satisfied after the shift to the driving range is performed. In addition, when a shift to a high speed gear is executed, a timer T^ that is started when a shift to a driving range is executed.
Since the gear is returned to the first gear when T reaches a predetermined value T3, the faster the SAF auto control condition is satisfied, the longer the transit time through the high gear. This effect is well suited to the fact that the faster the SAF auto control conditions are met, the more the engine revs up. Note that this effect was also obtained in the above-mentioned embodiment. [Effects of the Invention] As explained above, according to the present invention, when a sudden start is requested when shifted from the non-driving range to the driving range, the front and rear wheel differentials are permitted or restricted according to the By changing the execution/non-execution of the auto control, or changing the details when it is executed, it is possible to improve the durability of the drive system and minimize the feeling of sluggishness when starting. Excellent effects can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the gist of the present invention, and FIG. 2 is a block diagram showing the gist of the present invention.
A skeleton diagram showing a power transmission system of a four-wheel drive vehicle to which an embodiment of the present invention is applied, FIG. 3 is a skeleton diagram of a differential control clutch, and FIG. 4 is a skeleton diagram showing a gear train of an automatic transmission. Fig. 5 is a diagram showing the switching state of the solenoid valve and the engagement/action state of the WJ friction engagement device when each shift range is achieved; Fig. 6 is a diagram showing the control executed by the above embodiment device. Flow Chart Showing Procedures FIG. 7 is a flow chart showing another control procedure. 30... Center differential device, 70... Differential control clutch, 80... Control device, 91... Throttle opening sensor (accelerator opening sensor), 92... Manual shift position sensor, Fc・
...Differential limiting force.

Claims (2)

[Claims] (1) A means for detecting a shift range is provided, so that when the shift range is switched from a non-driving range to a driving range, a friction engagement device for temporarily forming a high speed gear can be engaged. In a shift control device for an automatic transmission of a four-wheel drive vehicle, the shift control device is configured to allow or restrict differential shift between the front and rear wheels, comprising means for detecting whether a sudden start is requested; means for detecting a motion permission or restriction state; and means for detecting whether or not the control for temporarily forming a high speed gear is executed when it is detected that a sudden start is requested; A speed change control device for an automatic transmission of a four-wheel drive vehicle, comprising: means for determining according to a restriction state; (2) A means for detecting a shift range is provided, so that when the shift range is switched from a non-driving range to a driving range, a friction engagement device for temporarily forming a high speed gear can be engaged. In a shift control device for an automatic transmission of a four-wheel drive vehicle, the shift control device is configured to allow or restrict differential shift between the front and rear wheels, comprising means for detecting whether a sudden start is requested; means for detecting a state in which differential movement of the front and rear wheels is permitted or restricted; means for executing control for temporarily forming a high speed gear when a sudden start is detected as being requested; and permission or restriction for differential movement of the front and rear wheels A shift control device for an automatic transmission for a four-wheel drive vehicle, comprising: means for changing the gear ratio of the temporarily formed high speed gear depending on the state.