JP2012057654A - Control device of automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an automatic transmission that certainly determines a slip state of a wheel regardless of an anti-lock brake and avoids based on a slip determination an improper shift-down caused by vehicle speed misjudgement at wheel slip, and certainly prevents engine damage and inadequate vehicle behavior.SOLUTION: An ECU to perform shift control determines a slip state (full lock, half lock, and stick slip) of a wheel of a vehicle (S8). When "Yes" is judged, a shift-down prohibition flag F1 is set (S10) to prohibit shift-down based on a target gear ratio specified by a shift map.

Description

  The present invention relates to a control device for an automatic transmission, and more particularly, when a slip (including a full lock state) occurs on a wheel by a brake operation, the vehicle speed is erroneously recognized and an inappropriate shift down is executed. The present invention relates to a control device for an automatic transmission that can prevent troubles.

  2. Description of the Related Art In recent years, automatic transmissions that automatically switch gear positions according to the amount of accelerator operation by a driver, vehicle speed, and the like have become widespread not only in passenger cars but also in large vehicles such as trucks and buses. As this type of automatic transmission, for example, an automatic transmission in which a planetary gear mechanism is combined with a torque converter or a continuously variable transmission such as a belt type, a conventional manual transmission is used as a base for shifting operation and shifting. There are also automatic transmissions and the like in which the clutch operation associated with is automated by an actuator. In any automatic transmission, the target shift speed is determined from a preset shift map based on the accelerator opening, the vehicle speed, and the like, and the actual shift speed is controlled so as to achieve the target shift speed.

However, when the driver's brake operation causes slipping on the vehicle wheel, the vehicle speed decreases rapidly even though the vehicle speed has not decreased so much. The control device misrecognizes. For this reason, the shift stage on the low gear side is set as the target shift stage based on the incorrect vehicle speed, and the downshift is performed according to the target shift stage. When the slip is resolved, the wheel speed recovers and rises rapidly, making it inadequate at the gear position on the low gear side after the downshift, causing damage due to engine overspeeding or disturbance in vehicle behavior due to sudden increase in torque of the drive wheels. May cause.
As a technique paying attention to such a problem, a control device for an automatic transmission described in Patent Document 1 can be cited. In the technique of Patent Document 1, when an operation signal is input from the antilock brake device side to the transmission control device side and the antilock brake device is in an operating state, that is, as described above, the vehicle wheel is in a slipping state. Sometimes the setting of the target gear position is stopped to avoid the above-described inappropriate shift down.

JP-A-7-305762

  As described above, in the technology of Patent Document 1, since the slip determination is performed on the shift control device side based on the operation signal from the antilock brake device side, the technology is not implemented unless the vehicle is equipped with the antilock brake device. Can not. However, the anti-lock brake device is not always installed in the vehicle. For example, in order to give priority to the specification for the country where the manufacturing cost of the vehicle needs to be reduced as much as possible due to price competition or the driver's brake operation. In the case of specifications for countries where there is a tendency to dislike brake control intervention by the antilock brake device, the installation of the antilock brake device may be omitted.

Therefore, in a vehicle that does not include an anti-lock brake device for such a reason, the technology of Patent Document 1 cannot execute wheel slip determination, resulting in inappropriate downshifting when the vehicle speed is erroneously recognized due to wheel slip. It was not possible to eliminate the above-mentioned defects.
The present invention has been made to solve such problems. The object of the present invention is to reliably determine the slip state of the wheel regardless of the presence or absence of the antilock brake device, and to determine the wheel based on the slip determination. It is an object of the present invention to provide a control device for an automatic transmission that can avoid an inappropriate shift down due to erroneous recognition of the vehicle speed at the time of a slip and thus reliably prevent engine damage or vehicle behavior disturbance. .

  In order to achieve the above object, according to the first aspect of the present invention, the target shift speed is determined from the shift map by the target shift speed determining means according to the accelerator opening and the vehicle speed, and the automatic transmission is determined by the shift control means based on the target shift speed. In a control device for an automatic transmission that switches the shift speed of the vehicle, when the braking force of the vehicle is increased by a brake operation, the rotation of the wheel of the vehicle stops almost completely, and between the full lock and the grip state Slip determination means for determining the half-lock state of the wheel and the occurrence of stick-slip where the wheel acceleration periodically increases or decreases, and the shift control means generates either full lock, half-lock or stick-slip by the slip determination means. When it is determined that the target gear position is determined, the target gear position determining means determines the target gear position on the lower gear side than the current gear position. Even if that is to maintain the current speed stage regardless of the target gear position.

According to a second aspect of the present invention, in the first aspect, when the shift control means continues to stop the foot brake operation for a predetermined time, or the vehicle speed is substantially zero and the foot brake operation stop continues for the predetermined time. When the brake hydraulic pressure reduction continues for a predetermined time, the maintenance of the current shift speed is stopped and the shift speed is switched based on the target shift speed.
According to a third aspect of the present invention, in the first or second aspect, the shift control means is configured such that when the difference between the vehicle body acceleration and the output shaft acceleration of the automatic transmission is equal to or greater than a predetermined half-lock determination value, the half-lock Is determined to have occurred.
According to a fourth aspect of the present invention, in the first to third aspects, when the shift control means periodically increases or decreases the output shaft acceleration of the automatic transmission over a predetermined number of times within a preset stick-slip determination time. It is determined that stick-slip has occurred.

  As described above, according to the vehicle transmission control apparatus of the first aspect of the present invention, when the occurrence of full lock, half lock, or stick slip is determined by the slip determination means, and it is determined that any one of the slip states has occurred, Even when the target gear position on the lower gear side than the current gear position is determined, the shift control means maintains the current gear position regardless of the target gear position. Therefore, inappropriate shift down due to erroneous recognition of vehicle speed at the time of wheel slip can be avoided in advance to prevent engine damage and vehicle behavior disturbance, etc., and based on the operation signal from the anti-lock brake device Since the shift control means performs the slip determination without any problem, it can be applied to a vehicle not equipped with an anti-lock brake device, and the applicable vehicle types can be greatly expanded.

According to the vehicle transmission control device of the second aspect of the invention, in addition to the first aspect, the continuation of the foot brake operation stop for a predetermined time or the continuation of the foot brake operation stop for a predetermined time when the vehicle speed is substantially zero. If the brake oil pressure continues to drop, the maintenance of the current gear position is stopped, so that inappropriate downshifts during pumping brakes can be prevented, and downshifts with unstable vehicle behavior can be prevented. Can be prevented.
According to the vehicle shift control device of the invention of claim 3, in addition to claim 1 or 2, the half lock of the wheel can be reliably determined based on the difference between the vehicle body acceleration and the output shaft acceleration of the automatic transmission. it can.
According to the vehicle shift control device of the invention of claim 4, in addition to claims 1 to 3, it is possible to reliably determine the stick-slip of the wheel based on the periodic increase / decrease state of the output shaft acceleration.

1 is an overall configuration diagram showing a track drive system to which an automatic transmission control device of an embodiment is applied. It is a flowchart which shows the downshift prohibition routine which ECU performs. It is a flowchart which shows the full lock determination routine which ECU performs. It is a flowchart which shows the half-lock determination routine which ECU performs. It is a flowchart which shows the stick slip determination routine which ECU performs. It is a flowchart which shows the stick-slip detection start / stop routine which ECU performs. It is a flowchart which shows the stick-slip detection routine which ECU performs. It is a time chart which shows the fluctuation state of the output-axis acceleration when stick-slip occurs.

Hereinafter, an embodiment of a control device for an automatic transmission embodying the present invention will be described.
FIG. 1 is an overall configuration diagram showing a track drive system to which an automatic transmission control device of this embodiment is applied. However, the application target of the automatic transmission control device of the present invention is not limited to a truck, and may be applied to, for example, a bus or a passenger car.

A vehicle is equipped with a diesel engine (hereinafter referred to as an engine) 1 as a driving power source. The engine 1 is configured as a so-called common rail type engine that supplies high-pressure fuel accumulated in a common rail by a pressurizing pump to the fuel injection valve of each cylinder and injects the fuel into the cylinder as the fuel injection valve opens.
The type of the engine 1 is not limited to this, and may be a conventional type diesel engine that controls fuel injection to each cylinder according to the operation of the control rack, or may be a gasoline engine.

  An input shaft 3a of an automatic transmission (hereinafter simply referred to as a transmission) 3 is connected to an output shaft 1b of the engine 1 via a clutch device 2. The rotation of the engine 1 is transmitted to the transmission 3 when the clutch device 2 is connected. It has come to be. The transmission 3 is based on a manual transmission having 12 forward speeds (1st to 12th speeds) and 1 reverse speed. As described below, the transmission 3 is associated with the speed change operation and the speed change. The connection / disconnection operation of the clutch device 2 is automated. Needless to say, the gear position of the transmission 3 is not limited to the above and can be arbitrarily changed.

The clutch device 2 is configured as a friction clutch that is connected to the flywheel 4 by press-contacting the clutch plate 5 with a pressure spring 6 and is disconnected by separating the clutch plate 5 from the flywheel 4. An air cylinder 8 is connected to the clutch plate 5 via an outer lever 7, and an air tank 11 filled with compressed air is connected to the air cylinder 8 via an air passage 10 in which an electromagnetic valve 9 is interposed.
When the electromagnetic valve 9 is opened, compressed air is supplied from the air tank 11 to the air cylinder 8 via the air passage 10, and the air cylinder 8 is activated to separate the clutch plate 5 from the flywheel 4 via the outer lever 7. Thus, the clutch device 2 is switched from the connected state to the disconnected state. On the other hand, when the solenoid valve 9 is closed, the air cylinder 8 stops operating due to the stop of the supply of compressed air, so that the clutch plate 5 is pressed against the flywheel 4 by the pressure spring 6, and thereby the clutch device 2 is released from the disconnected state. Switch to connected state. As described above, the air cylinder 8 is operated in accordance with the opening and closing of the electromagnetic valve 9 so that the clutch device 2 can be automatically connected and disconnected.

  The transmission 3 is provided with a gear shift unit 14 for switching the gear stage. Although not shown, the gear shift unit 14 includes a plurality of air cylinders that operate shift forks corresponding to the respective gear stages in the transmission 3, and It incorporates multiple solenoid valves that actuate the air cylinder. The gear shift unit 14 is connected to the above-described air tank 11 through the air passage 12, and compressed air from the air tank 11 is supplied to the corresponding air cylinder according to opening and closing of each solenoid valve, and the air cylinder is operated. When the corresponding shift fork is switched, the gear position of the transmission 3 is switched according to the switching operation. As described above, the air cylinder is operated in accordance with the opening / closing of the electromagnetic valve of the gear shift unit 14, and the transmission 3 can be automatically operated for shifting.

In the passenger compartment, an input / output device (not shown), a storage device (ROM, RAM, etc.) for storing control programs and control maps, an ECU (control unit) equipped with a central processing unit (CPU), a timer counter, etc. 21 is installed, and comprehensive control of the engine 1, the clutch device 2, and the transmission 3 is performed.
On the input side of the ECU 21, an engine rotation speed sensor 22 that detects the rotation speed Ne of the engine 1, a clutch rotation speed sensor 23 that detects the rotation speed (clutch rotation speed) of the input shaft 3a of the transmission 3, and a driver seat The lever position sensor 24 for detecting the change position of the change lever 13, the gear position sensor 25 for detecting the gear position of the transmission 3, the accelerator sensor 27 for detecting the operation amount Acc of the accelerator pedal 26, and the output of the transmission 3 A vehicle speed sensor 28 provided on the shaft 3b for detecting an output shaft rotational speed Vss (correlating with the vehicle speed V), a foot brake switch 30 for detecting an operation of the foot brake 29, and a vehicle longitudinal acceleration G (hereinafter referred to as a vehicle body acceleration). Sensors such as an acceleration sensor 31 for detecting the sensor are connected.

Further, the electromagnetic valve 9 of the clutch device 2 and the electromagnetic valves of the gear shift unit 14 are connected to the output side of the ECU 21, and although not shown, a pressure pump for common rail pressure accumulation and fuel for each cylinder are not shown. An injection valve is connected.
In addition, you may make it provide ECU for engine control separately from ECU21, for example, without controlling comprehensively by single ECU21 in this way.

For example, the ECU 21 determines the rail pressure of the common rail accumulated by the pressure pump from a map (not shown) based on the engine speed Ne detected by the engine speed sensor 22 and the accelerator operation amount Acc detected by the accelerator sensor 27. The fuel injection amount to each cylinder is calculated, and the fuel injection timing is calculated from a map (not shown) based on the engine speed Ne and the fuel injection amount Q. The pressurizing pump is driven and controlled based on these calculated values, and the engine 1 is operated while driving and controlling the fuel injection valves of the respective cylinders.
Further, the ECU 21 executes the automatic transmission mode when the lever position sensor 24 detects that the change lever 13 is switched to the D range, and based on the accelerator operation amount Acc and the vehicle speed V detected by the vehicle speed sensor 28, the ECU 21 The target shift speed is calculated from the shift map that is not (target shift speed determining means). Then, while opening and closing the electromagnetic valve of the clutch device 2 and operating the clutch device 2 with the air cylinder 11, the predetermined shift valve for the gear shift unit 14 is opened and closed and the corresponding shift fork is switched with the air cylinder. The target shift speed is achieved (shift control means), and thus the vehicle is always driven with an appropriate shift speed.

Therefore, when the vehicle decelerates, the gear position on the low gear side is set as the target gear position, and the downshift is executed according to the above procedure so as to achieve this target gear position. However, in addition to such a normal downshift, as described in [Background Art], an inappropriate downshift may be performed based on an incorrect vehicle speed V when the wheel slips. When recovered, the engine 1 may be damaged due to excessive rotation or the vehicle behavior may be disturbed. Moreover, in the technique of patent document 1 proposed as a countermeasure, since the operation signal from the anti-lock brake device side is used, the implementation is limited to a vehicle equipped with the anti-lock brake device.
And since the track | truck of this embodiment is not equipped with the anti-lock brake device, the technique of patent document 1 cannot be applied. In view of such problems, in the present embodiment, wheel slip determination is executed based on detection information from existing sensors connected to the ECU 21 (slip determination means), and inappropriate shift down is performed based on the determination result. Hereinafter, the processing executed by the ECU 21 will be described in detail.

FIG. 2 is a flowchart showing a downshift prohibition routine executed by the ECU 21. The ECU 21 executes the routine at a predetermined control interval when the automatic transmission mode is selected by switching the change lever 13 to the D range. Yes.
First, in step S2, it is determined whether or not the foot brake 29 is currently being operated based on the detection information from the foot brake switch 30, and if the determination is No (No), the process proceeds to step S4, where a shift down prohibition flag F1 is determined. After resetting (= 0), the routine is temporarily terminated. While the vehicle is being decelerated by a brake operation in the automatic shift mode, the target gear position on the low gear side is appropriately set from the shift map according to the decrease in the vehicle speed V, and the shift down is executed. The function of inhibiting the downshift at this time is exhibited. In this case, since the shift down prohibition flag F1 is reset, the shift down is permitted and executed based on the shift map as usual.

When the determination in step S2 is Yes (positive), the process proceeds to step S6, and it is determined whether or not the vehicle speed V calculated based on the output shaft rotational speed Vss from the vehicle speed sensor 28 is equal to or higher than the vehicle speed determination value V0. Since a sharp increase in wheel speed due to slip recovery after an inappropriate downshift occurs more significantly in the higher vehicle speed range, the vehicle speed judgment value V0 is set as a value near the lower limit of the vehicle speed V that needs to be countered. Has been.
When the determination in step S6 is No, the process proceeds to step S4. When the determination is Yes, the process proceeds to step S8, and it is determined whether or not the vehicle wheel has reached a slip state due to an increase in the braking force accompanying the brake operation. As will be described in detail later, the slip state includes a full lock in which the rotation of the wheel stops almost completely, a half lock between the full lock and the grip state (non-slip state), and a stick slip in which the wheel acceleration periodically increases and decreases. These three types are determined individually.

When the determination in step S8 is No, the process proceeds to step S4. When the determination is Yes, the process proceeds to step S10 and the shift down prohibition flag F1 is set (= 1). Accordingly, in this case, even if the target gear position on the low gear side is set from the shift map, the downshift based on the target gear position is prohibited by the shift down prohibition flag F1, and as a result, the current gear position is maintained. It will be.
In subsequent steps S12 and S14, it is determined whether or not to prohibit the downshift. In step S12, it is determined whether or not the operation of the foot brake 29 has been stopped for a predetermined time. When the determination is No, an inappropriate downshift due to wheel slip may still occur, and if the determination is Yes, it can be considered that an inappropriate downshift can no longer occur.

When the determination in step S12 is No, the process proceeds to step S14, and it is determined whether any of the following requirements 1) and 2) is satisfied.
1) The vehicle speed V = 0 and the foot brake operation stop being continued for a predetermined time.
2) A decrease in brake hydraulic pressure to a vehicle speed V = 0 and less than a predetermined pressure is continued for a predetermined time.
Basically, as in the case of stopping the brake operation in step S12, an inappropriate downshift caused by wheel slip cannot occur if the vehicle speed V = 0 and the vehicle has stopped. However, since the vehicle speed V may be zero even though the vehicle is not stopped due to the full lock of the wheel, in the requirement 1), in order to exclude such a full lock, the condition for stopping the foot brake operation is Have been added. Accordingly, since the foot brake 29 is released, the vehicle speed V = 0 means a complete stop of the vehicle.

Requirement 2) assumes that the foot brake switch 30 is broken and is set on condition that the brake hydraulic pressure is reduced instead of the foot brake operation stop of Requirement 1), and the brake hydraulic pressure is reduced. A vehicle speed V = 0 means a complete stop of the vehicle.
If NO is also determined in step S14 following step S12, there is a possibility that an inappropriate shift down due to wheel slip may still occur. Therefore, the process returns to step S10 and the shift down prohibition flag F1 is set. to continue. If the determination in any of steps S12 and S14 is Yes, it is determined that an inappropriate downshift can no longer occur, and the downshift prohibition flag F1 is reset in step S4.
On the other hand, the ECU 21 performs the full lock determination routine shown in FIG. 3, the half lock determination routine shown in FIG. 4, and the stick-slip determination routine shown in FIG. 5 at predetermined control intervals for the slip state determination processing in step S8. Hereinafter, the processing contents of each routine will be sequentially described.

First, in step S22 of the full lock determination routine of FIG. 3, it is determined whether or not the state where the output shaft acceleration Vss_G is less than the preset full lock determination value THDfull has continued for a predetermined time. The output shaft acceleration Vss_G is obtained by differentiating the output shaft rotation speed Vss detected by the vehicle speed sensor 28 according to the following equation (1) to calculate the acceleration dVss / dt and dividing the acceleration dVss / dt by the gravitational acceleration g. Calculated.
Vss_G = (dVss / dt) / g (1)
For example, as the full lock determination value THDfull, a value corresponding to a full lock state in which the rotation of the wheel stops almost completely is set. For this reason, when the determination in step S22 is No, it is considered that the wheel is not fully locked, and after determining that the full lock has not been detected in step S24, the routine is terminated. When the determination in step S22 is Yes, it is considered that the wheel is fully locked, and the determination of full lock detection is made in step S26.

Further, in step S32 of the half-lock determination routine of FIG. 4, the failure determination of the acceleration sensor 31 is executed. If the failure is detected, the determination of Yes is made and the process proceeds to step S34. In step S34, it is determined that half-lock is not detected, and the routine is terminated. As described below, in order to determine half-lock, the vehicle body acceleration G detected by the acceleration sensor 31 is required. Therefore, when half-lock cannot be determined due to a sensor failure, the handling is the same as when half-lock is not detected. It is.
If it is determined that the acceleration sensor 31 has not failed and No is determined in step S32, the process proceeds to step S36, and a slip index Sidx representing the slip state of the wheel during half-lock is calculated. The calculation process is based on the following knowledge applying the principle of the road surface gradient calculation process.

As is well known, the principle of the road surface gradient calculation process is to determine the discrepancy between the vehicle body speed and the wheel speed from the comparison between the vehicle body acceleration G and the output shaft acceleration Vss_G. That is, the following equations (2) and (3) are established from the balance of forces acting on the vehicle body.
F = mgsinθ + m (dVss / dt) (2)
F = Gmg (3)
Here, m is the vehicle weight, and θ is the road gradient.
From these equations (2) and (3), the road surface gradient θ can be calculated by the following equation (4).
sinθ = G− (dVss / dt) / g (4)

Thus, although the original equation (4) is used to calculate the road surface gradient θ, the present inventor has found that the solution of the equation (4) is in the slip state of the wheel at the time of half-lock. It was also found that there was a correlation. In other words, when the wheel starts to slip due to a foot brake operation on a low μ road and reaches half-lock, the wheel speed rapidly decreases with respect to the vehicle speed, and the acceleration dVss / dt of the output shaft 3b increases to the negative side. This also increases the solution of equation (4). Therefore, the solution of the equation (4) represents the road surface gradient θ when the road surface is inclined, and represents the slip state of the wheel during the half lock caused by the brake operation. In the following explanation, the solution of the equation (4) is Thus, the slip index Sidx is used to indicate the slip state.
When the slip index Sidx is calculated in step S36, the process proceeds to step S38, and it is determined whether or not the slip index Sidx is equal to or greater than a preset half lock determination value THDhalf. For example, as the half lock determination value THDhalf, a value when a slight slip in the vicinity of the grip state is set is set. In the case where the wheel slips slightly, it is not considered as a half lock in view of the fact that an adverse downshift due to inappropriate shift down does not occur as in the grip state.

For this reason, when the determination in step S38 is No, it is considered that the wheel is not half-locked. In step S34, it is determined that half-lock is not detected, and the routine is terminated. If the determination in step S38 is Yes, it is considered that the wheel is half-locked, half-lock detection is determined in step S40, and the routine is terminated.
Further, the stick-slip determination routine of FIG. 5 is executed based on the stick-slip detection result. For this reason, stick slip detection processing will be described first.
The ECU 21 executes a stick-slip detection start / stop routine shown in FIG. 6 at predetermined control intervals in parallel with the routine of FIG. In step S52, it is determined whether or not the output shaft acceleration Vss_G is less than a preset decrease determination value GHLneg (Vss_G <GHLneg). ) And once complete the routine. When the determination in step S52 is Yes, the process proceeds to step S56 to execute stick-slip detection processing. Since stick-slip starts with a drop to the vicinity of the full lock of the wheel, in step S52, it is determined whether or not there is such a sign of stick-slip start.

Although details of the stick-slip detection process in step S56 will be described later, after the process is executed, the process proceeds to step S58 to determine whether or not the foot brake 29 is operated. While the determination in step S56 is Yes, the processes in steps S56 and 58 are repeated, and when the determination in step S58 is No, the process proceeds to step S54.
When the stick-slip detection process is executed in step S56, the ECU 21 starts a stick-slip detection routine shown in FIG. First, in step S62, the current timer value Ta is stored, and in subsequent step S64, whether or not the output shaft acceleration Vss_G (correlated with the wheel acceleration) is equal to or greater than a preset increase determination value GHLpos (Vss_G ≧ GHLpos). Determine. While the determination is No, the process of step S64 is repeated, and when the determination of step S64 is Yes, the process proceeds to step S66. In step S66, the first increase / decrease time T1 is calculated according to the following equation (5).

T1 = Tb-Ta (5)
Here, Tb is the current timer value. Therefore, the first increase / decrease time T1 represents the time required from when the output shaft acceleration Vss_G decreases to less than the decrease determination value GHLneg until the output shaft acceleration Vss_G becomes greater than the increase determination value GHLpos.
When the first increase / decrease time T1 is obtained as the required time in the increasing direction of the output shaft acceleration Vss_G as described above, in the subsequent steps S68 to 72, the second increase / decrease is set as the required time in the decreasing direction of the output shaft acceleration Vss_G. Time T2 is calculated. That is, the current timer value Ta is stored in step S68, and in the subsequent step S70, it is determined whether or not the output shaft acceleration Vss_G is less than the decrease determination value GHLneg. If the determination becomes Yes, the above formula ( The second increase / decrease time T2 is calculated from 5). As a result, the second increase / decrease time T2 is calculated as the required time from when the output shaft acceleration Vss_G increases to the increase determination value GHLpos or more to the decrease direction and to become less than the decrease determination value GHLneg.

In the following steps S74 to 78, the third increase / decrease time T3 is calculated as the required time in the increasing direction of the output shaft acceleration Vss_G in the subsequent steps S74 to 66, and in steps S80 to 84, the steps S68 to S84 are omitted. Similarly to 72, the fourth increase / decrease time T4 is calculated as the required time in the decreasing direction of the output shaft acceleration Vss_G. At the same time, in step S84, the stick-slip determination flag F2 is set (= 1), and then the routine ends.
Accordingly, the stick-slip determination flag F2 indicates that the determination in step S52 is No and there is no sign of stick-slip start, or even if stick-slip is started, the series of stick-slip detection processes described based on FIG. 7 is completed. When it was interrupted before, for example, when it was interrupted due to slip cancellation or shifting to full lock when the brake operation is stopped, it is reset at step S54. On the other hand, when the stick-slip detection process is completed before the brake operation is stopped In step S84 of FIG.

In parallel with the stick-slip detection process described above, the ECU 21 executes the stick-slip determination routine of FIG. 5 and first determines whether or not the stick-slip determination flag F2 is set in step S92. When the determination is No, that is, when the stick-slip detection process is not started, or when the stick-slip detection process is started but is not completed, it is considered that no stick-slip has occurred in the wheel, and the stick is detected in step S94. It is determined that no slip has been detected, and the routine is terminated.
When the determination in step S92 is Yes, that is, when the stick-slip detection process is completed, the process proceeds to step S96 to determine whether or not the following equation (6) is satisfied.

THDstick> T1 + T2 + T3 + T4 (6)
Here, THDstick is a stick-slip determination time set in advance as a predetermined time. Stick-slip is a phenomenon in which the output shaft acceleration Vss_G repeatedly increases and decreases with a certain large amplitude and with a certain short period. Therefore, the former requirement is determined based on the decrease determination value GHLneg and the increase determination value GHLpos, and the latter requirement is determined based on Expression (6). For this reason, the stick-slip determination time THDstick is set as the longest required time in which the increase / decrease (T1 to T4) of two cycles of the output shaft acceleration Vss_G can be recognized as a stick-slip. This is to prevent stick slip because the output shaft acceleration Vss_G increases and decreases slowly.
When the determination in step S96 is No, it is considered that no stick slip has occurred on the wheel, and in step S94, it is determined that stick slip has not been detected, and the routine is terminated. If the determination in step S96 is Yes, it is determined that stick slip has occurred on the wheel, and in step S98, determination of stick slip detection is made, and the routine is terminated.

FIG. 8 is a time chart showing the fluctuation state of the output shaft acceleration Vss_G when stick-slip occurs. The stick-slip detection process will be described more specifically with reference to this figure.
First, when the brake operation is started (point a in the figure), the output shaft acceleration Vss_G decreases according to the brake pedal force and falls below the decrease determination value GHLneg (point b in the figure), and step S52 in FIG. Is determined as Yes, and the stick-slip detection process is started. Thereafter, the output shaft acceleration Vss_G turns in the increasing direction and exceeds the increase determination value GHLpos (point c in the figure), and the required time in the increasing direction from this point b to point c is the first increase / decrease time in step S66 of FIG. Calculated as T1.

If stick-slip continues further, the output shaft acceleration Vss_G turns in the decreasing direction and falls below the decrease determination value GHLneg (point d in the figure), and the required time in the decreasing direction from this point c to point d is step S72 in FIG. Is calculated as the second increase / decrease time T2. The same applies thereafter, and the required time in the increasing direction of the output shaft acceleration Vss_G from point d to point e is calculated as the third increase / decrease time T3, and the required time in the decreasing direction from point e to point f is the fourth increase / decrease time. Calculated as T4, the stick-slip determination flag F2 is set at the point f. In response to the setting of the stick-slip determination flag F2, the establishment of equation (6) is determined in step S96 of FIG. 5, and in the example of FIG. 8, the stick-slip detection determination is made based on the establishment of equation (6).
The above is the case where the stick-slip detection process is completed, but when the slip is canceled by stopping the brake operation while the output shaft acceleration Vss_G is increasing or decreasing, or when the shift to full lock is performed by increasing the brake pedal force, Since the stick-slip detection process is not completed, it is determined that the stick-slip is not detected based on the reset of the stick-slip determination flag F2. Even if the stick-slip detection process is completed, if the equation (6) is not satisfied because the increase / decrease in the output shaft acceleration Vss_G during the detection process is gradual, it is determined that the stick-slip is not detected.

In this way, full lock, half lock, and stick slip of the wheel are respectively determined, and when any slip state is detected, the shift down prohibition flag F1 is set in step S10 in FIG. Shift down is prohibited. Therefore, an inappropriate downshift due to erroneous recognition of the vehicle speed V at the time of wheel slip can be avoided in advance, and troubles that occur when the wheel speed is recovered by subsequent slip cancellation, for example, damage due to engine overspeeding. Alternatively, it is possible to reliably prevent troubles such as disturbance in vehicle behavior due to a sudden increase in torque of the drive wheels.
As is apparent from the above description, the wheel slip determination is performed by the ECU 21 itself that executes the shift control without being based on the operation signal from the antilock brake device. Therefore, even when applied to a vehicle not equipped with an anti-lock brake device such as the truck of this embodiment, the above-mentioned effect can be obtained by accurately prohibiting downshifting based on slip determination. Can be greatly expanded.

On the other hand, in this embodiment, the output shaft rotational speed Vss, the presence / absence of the operation of the foot brake 29, and the vehicle body acceleration G are used as information for determining full lock, half lock, and stick-slip. Sensors that are originally used for shift control of the transmission 3 and inevitably detect each information are existing.
That is, since the output shaft rotational speed Vss (vehicle speed V) is used to calculate the target shift speed from the shift map in the automatic shift mode, the vehicle speed sensor 28 for detecting the output shaft rotational speed Vss is an existing one. Is. Further, when the vehicle decelerates, downshifting is automatically performed in order to enhance the engine braking action. Since such a deceleration state is determined based on the footbrake operation, the footbrake switch 30 that detects the footbrake operation is used. Is an existing one. Furthermore, in the automatic shift mode, the shift timing is changed in accordance with the road surface gradient θ. As described above, the road surface gradient θ is calculated based on the comparison between the vehicle body acceleration G and the output shaft acceleration Vss_G. The acceleration sensor 31 for detecting G is an existing one.

Therefore, there is no need to add a new sensor in order to perform the slip determination on the ECU 21 side, and it is possible to cope with it simply by changing the processing content of the ECU 21, so that it can be carried out without requiring a large burden in terms of cost. .
On the other hand, the set shift-down prohibition flag F1 is reset based on the determination in any one of steps S12 and S14 in FIG. 2, and the continuation of a predetermined time is conditioned in any determination. Therefore, even if the foot brake operation is stopped or the brake hydraulic pressure is lowered, if it is instantaneous, the determination of No is made in steps S12 and S14 and the shift down prohibition flag F1 is continuously set, and these states are predetermined. Only when the time continues, the determination of Yes is made in steps S12 and S14, and the shift down prohibition flag F1 is reset.
For example, when a pumping brake that turns on and off the foot brake 29 in a short cycle is performed, the brake operation is periodically stopped for a very short time and the brake hydraulic pressure is lowered during the pumping brake. However, in this embodiment, even in such a case, the shift down prohibition flag F1 is continuously set, so that inappropriate shift down during the pumping brake can be prevented.

Further, when the wheel reaches a slip state, the vehicle behavior becomes unstable, and the vehicle behavior is not stable until the vehicle body speed and the wheel speed match even after the foot brake operation is stopped. However, in this embodiment, downshifting is prohibited because the predetermined time has not elapsed at this time, and therefore downshifting in a state where the vehicle behavior is unstable can be reliably prevented. Further, if the automatic shift mode is selected at this time, when the shift down prohibition is canceled, the optimum shift stage is switched, so that rapid acceleration can be realized.
This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above embodiment, the transmission 3 is used in which the shifting operation and the connecting / disconnecting operation of the clutch device 2 associated with the shifting are automated based on the manual transmission, but the type of the transmission 3 is not limited thereto. . For example, the present invention may be applied to a so-called dual clutch transmission, an automatic transmission in which a planetary gear mechanism is combined with a torque converter, or a continuously variable transmission such as a belt type.
Further, in the above embodiment, the stick-slip detection determination is performed based on the increase / decrease (T1 to T4) of the output shaft acceleration Vss_G for two periods. However, the present invention is not limited to this. For example, the determination may be made based on the increase / decrease (1.5 cycles) for two increases and the decrease of the output shaft acceleration Vss_G, or may be made based on the increase / decrease for three cycles of the output shaft acceleration Vss_G.

3 Transmission 21 ECU (Target gear stage determination means, transmission control means, slip determination means)

Claims (4)

A control apparatus for an automatic transmission that determines a target shift stage from a shift map by a target shift stage determining means in accordance with an accelerator opening and a vehicle speed, and switches and controls the shift stage of the automatic transmission by a shift control means based on the target shift stage. In
When the braking force of the vehicle increases due to the brake operation, the wheel lock of the vehicle stops almost completely, the half lock state between the full lock and the grip state, and the wheel acceleration periodically increases or decreases Slip judging means for judging the occurrence of stick slip, respectively,
The shift control means, when it is determined by the slip determination means that any one of the full lock, half lock, and stick slip has occurred, the target shift stage determination means sets a target on the lower gear side than the current shift stage. A control device for an automatic transmission, characterized in that, even when a shift speed is determined, the current shift speed is maintained regardless of the target shift speed.   The shift control means is configured such that when the foot brake operation is stopped for a predetermined time, or when the vehicle speed is substantially zero and the foot brake operation is stopped for a predetermined time, or the brake hydraulic pressure decreases for a predetermined time. 2. The automatic transmission control device according to claim 1, wherein when the operation is continued, the maintenance of the current shift speed is stopped and the shift speed is switched based on the target shift speed.   The shift control means determines that the half lock has occurred when the difference between the vehicle body acceleration and the output shaft acceleration of the automatic transmission is equal to or greater than a preset half lock determination value. The control device for an automatic transmission according to claim 1 or 2.   The shift control means determines that the stick slip has occurred when the output shaft acceleration of the automatic transmission is periodically increased or decreased over a predetermined number of times within a preset stick-slip determination time. The control device for an automatic transmission according to any one of claims 1 to 3.

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