JPH10184904A - Fail-safe device of creep prevention apparatus for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To guarantee that friction elements remain secured to each other even when a creep prevention apparatus in which the working pressure applied to the friction elements is controlled by a pressure control valve in such a way as to allow slipping of the friction elements, fails. SOLUTION: From time t1 when N is shifted to D onward, a pressure control valve for creep prevention gradually builds up a forward clutch oil pressure Pc and a revolving speed N of a turbine drops when the relevant clutch is engaged. It is evaluated as normal if a torque converter slip amount ΔNA at time t2 following a set time interval Δts becomes larger than an instantaneous torque converter slip amount ΔN1 at the time t1 by a set value or more, and if not it is deemed abnormal. If the case is normal, the gradual increase of the pressure Pc is continued, and if abnormal, an instruction to maximize the pressure Pc is issued to the pressure control valve to prevent the transmission of power from being disabled. As apparent from the comparison with a slip amount ΔNB during high idling shown by a broken line, the instantaneous slip amount ΔNA at the time t2 is not affected by an increase in idling speed and the evaluation of anomalies is accurate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a creep preventing device for an automatic transmission, and more particularly to a fail-safe device for preventing a creep phenomenon of an automatic transmission caused by drag transmission of a fluid transmission device.

[0002]

2. Description of the Related Art In an automatic transmission, since the engine rotation is input via a fluid transmission, the drag torque of the fluid transmission is stopped during a stop in a state where the power can be transmitted with the automatic transmission in a travel range. Causes a so-called creep phenomenon that causes the vehicle to run at a low speed. The driver operates the brakes to prevent this very slow running, but during this time,
Fuel economy is likely to deteriorate and vibration problems are likely to occur.

[0003] Therefore, by lowering the operating oil pressure of the hydraulically operated friction element to bring the automatic transmission into a state in which power can be transmitted in the traveling range, the operating friction element is brought into a slip state. There has been proposed a creep preventing device that reduces transmission of creep torque by a fluid transmission device.

In order to lower the operating oil pressure of the friction element as described above, a pressure control valve such as a solenoid valve is used. This pressure control valve controls the slipping friction element in a creep prevention control accompanying a start operation or the like. When the automatic transmission is re-engaged at the end of, or when the automatic transmission is switched from the neutral (N) range to the traveling (D) range to engage the friction element, the engagement shock of the friction element is reduced. It is also used to gradually increase the operating oil pressure.

[0005] By the way, if the creep prevention device fails and the operation oil pressure increase control via the pressure control valve cannot be performed as instructed, and the friction element cannot be engaged,
Since the power transmission of the automatic transmission itself becomes impossible, a fail-safe measure at the time of the failure is required.

[0006] As a conventional fail-safe device, there is the following device as described in JP-A-6-174079.

Here, when the automatic transmission is switched from the neutral (N) range to the traveling (D) range, the input speed (engine speed N _e ) of the fluid transmission device (torque converter).
The change tendency of the output rotation speed (turbine rotation speed) _Nt with respect to the following will be described with reference to FIG. FIG.
In thigh when switching from the neutral (N) range to the traveling (D) range to the instant t _1, as described above in the pressure control valve showing the working oil pressure P _c of the friction elements in response to the range change by a solid line As a result, the friction element is fastened and coupled, and the output element (turbine) of the fluid transmission (torque converter) is gradually coupled to the stopped wheel with a large force, and the output speed of the fluid transmission (torque converter) ( Turbine speed)
It reduces to indicate N _t by the solid line. The turbine speed N _t instantaneously t ₃ when the friction element is completely engaged is zero.

[0008] The fail-safe device of the creep prevention device described in the above-mentioned document is an N → D select instant t _{1 in} FIG.
Deviation between the instantaneous value of the turbine speed N _t, the instantaneous value of the turbine speed N _t at the instant t ₂ has elapsed set time Delta] t _S from N → D select instant t ₁ in, i.e., N → D select by determining whether decrease .DELTA.N _a turbine rotation speed N _t at the set time in Delta] t _S from the instantaneous t ₁ is equal to or greater than a set value, was to determine whether normal or not.

[0009]

However, there are concerns about the following problems in such a fail-safe device. That also is shown in FIG. 6, when in response to such operation of the engine driven accessory in the above set time Delta] t _S is idle-up control of the engine is made, the engine speed N _e is increased as indicated by a broken line also in this case the turbine speed N _t increases as indicated by a broken line by dragging action of the fluid transmission device.

[0010] In this case, N → D select the instant t decreased amount of turbine speed N _t during ₁ from the set time Delta] t _S is as shown in .DELTA.N _b, turbine speed decrease amount in the absence of the idle-up control .DELTA.N _a Thus, it is erroneously determined that an abnormality has occurred, and it is not possible to completely eliminate the concern of taking unnecessary fail-safe measures.

According to the first aspect of the present invention, as is apparent from the comparison between ΔN _A and ΔN _{B when} the input / output rotation speed of the fluid transmission device is different, this is not significantly affected by the presence / absence of the idle-up control. It is an object of the present invention to propose a fail-safe device of a creep prevention device that determines an abnormality based on the degree of fastening progress relatively accurately.

Further, the invention according to claim 2 is based on the viewpoint that the speed ratio of the fluid transmission device is relatively accurately represented by the degree of engagement of the friction element without being greatly affected by the presence or absence of the idle-up control. It is an object of the present invention to propose a fail-safe device of a creep prevention device that determines an abnormality based on the abnormality.

According to a third aspect of the present invention, the operating oil pressure P of the friction element
_c is has a rise delay as shown by the one-dot chain line in FIG. 6 as at low temperatures, N between instant t ₁ ~t ₃ by fastening delay friction element
→ from the D selection time becomes longer, that is because the reduction in the turbine speed N _t is slightly delayed, delaying the abnormality determination instantly with this much low temperature, and aims to improve the determination accuracy at low temperatures Is what you do.

A fourth object of the present invention is to propose an abnormality process at the time of the above-described abnormality determination.

[0015]

According to the first aspect of the present invention, there is provided a fail-safe device for a creep preventing device for an automatic transmission according to the first aspect of the present invention, which receives rotation of an engine through a fluid transmission device. Is used in an automatic transmission that shifts and outputs the engine rotation at a speed selected by a selective hydraulic operation of a plurality of friction elements, and reduces the transmission of creep torque by the fluid transmission during the operation. In a creep prevention device of an automatic transmission in which the operating oil pressure of the friction element is reduced by a pressure control valve to bring the friction element into a slip state, the friction element includes re-fastening from the slip state. The slip amount represented by the input / output rotation speed difference of the fluid transmission at the moment when the engagement is commanded, and the hydraulic pressure of the friction element in When the slip amount deviation between the slip amount of the fluid transmission device and the slip amount when the set time elapses from the instant of the engagement command among the slip amounts of the fluid transmission device that is changed by gradually increasing the pressure control valve is abnormal when the slip amount deviation is less than the set value. It is characterized in that it is configured to judge.

According to a second aspect of the present invention, there is provided a fail-safe device for a creep preventing device for an automatic transmission, wherein the rotation of an engine is input via a fluid transmission device.
It is used in an automatic transmission that shifts and outputs the engine rotation at a speed selected by a selective hydraulic operation of a plurality of friction elements, and in order to reduce transmission of creep torque by the fluid transmission, In a creep preventing device for an automatic transmission in which the operating oil pressure of a friction element is reduced by a pressure control valve to bring the friction element into a slip state, the engagement of the friction element including re-fastening from the slip state A speed ratio represented by a ratio of an output rotation speed to an input rotation speed of the fluid transmission device at the moment when the command is issued, and gradually increasing the operating oil pressure of the friction element by the pressure control valve in response to the engagement command. The speed ratio deviation between the speed ratio of the fluid transmission device and the speed ratio at the time when the set time has elapsed from the instant of the engagement command is not less than the set value. It is characterized in that it has configured to determine an abnormality with the absence.

According to a third aspect of the present invention, in the fail-safe device for a creep preventing device for an automatic transmission according to the third aspect of the present invention, the set time is set according to the operating oil temperature of the automatic transmission. The longer the operating oil temperature, the longer the operating oil temperature.

According to a fourth aspect of the present invention, there is provided a fail-safe device for a creep preventing device for an automatic transmission according to any one of the first to third aspects of the present invention. A command to the pressure control valve to supply the operating oil pressure to the friction element.

[0019]

According to the first aspect of the present invention, the automatic transmission operates at a shift speed selected by selective hydraulic operation of a plurality of friction elements.
The rotation of the engine from the fluid transmission is shifted and output.

The creep preventing device, when reducing the transmission of creep torque by the fluid transmission device, lowers the operating oil pressure of the operating friction element by means of a pressure control valve, thereby bringing the friction element into a slip state.

In the first invention, the slip amount represented by the input / output rotational speed difference of the fluid transmission at the moment when the engagement of the friction element is commanded including the re-fastening from the slip state, and Of the slip amount of the fluid transmission device that changes by gradually increasing the operating oil pressure of the friction element in response to the engagement command by the pressure control valve, the slip amount when the set time has elapsed from the instant of the engagement command. An abnormality is determined when the slip amount deviation between the intervals is less than the set value.

Incidentally, as described above, the slip amount deviation relatively accurately represents the degree of engagement of the friction element without being significantly affected by the presence or absence of the idle-up control. According to the first aspect of the present invention in which an abnormality is determined when the value is less than the value, the problem of the conventional device that erroneously determines that the output rotational speed of the fluid transmission device has changed due to an increase in the engine rotational speed in idle-up control. Can be eliminated.

In the second invention, a speed ratio represented by a ratio of an output rotation speed to an input rotation speed of the fluid transmission device at the moment of the engagement command of the friction element, and a speed ratio of the friction element in response to the engagement command. Among the speed ratios of the fluid transmission device that are changed by gradually increasing the operating oil pressure by the pressure control valve, the speed ratio deviation between the speed ratio when the set time has elapsed from the instant of the engagement command is equal to or greater than the set value. It is judged abnormal when it does not become necessary.

By the way, the speed ratio deviation also relatively accurately represents the degree of engagement of the friction element without being greatly affected by the presence or absence of the idle-up control. When the speed ratio deviation does not exceed the set value, According to the second aspect of the present invention, it is possible to eliminate the problem of the conventional device that erroneously determines that the output speed of the fluid transmission device has changed due to an increase in the engine speed due to the idle-up control. .

In the third aspect of the present invention, since the set time is set longer as the operating oil temperature of the automatic transmission becomes lower, the operating oil pressure of the friction element at the time of low temperature causes a large rise delay, thereby increasing the engagement delay of the friction element. It is possible to prevent erroneous determination that the change has occurred as an abnormality, and it is possible to increase the determination accuracy at low temperatures.

In the fourth invention, when the abnormality is determined,
By instructing the pressure control valve to supply the operating oil pressure of the pressure adjustment upper limit value to the friction element, the friction element can be securely engaged even in the event of an abnormality, thereby preventing the automatic transmission from becoming unable to transmit power. Can be prevented.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system diagram showing a creep preventing device for an automatic transmission having a fail-safe device according to an embodiment of the present invention. In the present embodiment, the anti-creep device 10 of the automatic transmission includes a forward clutch (start clutch) 11, which is a starting friction element to be engaged in the first forward speed of the automatic transmission, in a semi-engaged state (slip state). To prevent creep.

In FIG. 1, reference numeral 12 denotes a torque converter (fluid transmission), which comprises a pump impeller 12p, a turbine runner 12t, and a stator 12s.
The torque converter 12 is provided with a pump impeller 12p.
To the engine crankshaft 13, the turbine runner 12 t to the input shaft 14 of the automatic transmission, and the stator 12 s to the one-way clutch 1 on the transmission case 15.
It is a normal one that is put into practical use by putting it through 2o.

Here, the torque converter 12 transmits the engine rotation (rotation speed _Ne ) from the crankshaft 13 to the input shaft 14 of the automatic transmission while increasing the torque via the internal working fluid. The input rotation speed to the machine is _Nt .

The automatic transmission includes a plurality of friction elements (not shown) including a forward clutch 11 and selectively operates (engages) the plurality of friction elements including the forward clutch 11 to a corresponding gear position. Is to select.

In this embodiment, the forward clutch 1 is engaged while the vehicle is stopped with the automatic transmission in the travel range to set the automatic transmission in the forward first speed selection state.
To a 1 to perform anti-creep in the semi-engaged state (slip state), providing the oil pressure modulator (pressure control valve) 16 that controls the hydraulic pressure P _C of the forward clutch 11.

The oil pressure modulator (hereinafter, referred to as OPM) 16 is used to control the line pressure P of the automatic transmission.
_L is supplied from the oil passage 17 to the input port 18, the output port 19 is connected to the operating hydraulic chamber 11 a of the forward clutch 11 via the oil passage 20, and has a drain port 21. ) 23 an electromagnetic force to act in the figure left by the output pressure of the port 19 via the port 22a to the chamber 24 facing the other end of the spool 22, i.e., is fed back to hydraulic pressure P _C of the forward clutch 11.

[0033] Such OPM16 as source pressure line pressure P _L to the input port 18, and functions as a linear solenoid valve which produces the hydraulic pressure P _C which corresponds to the electromagnetic force corresponding to the current value i _X to the solenoid 23, the the oil passage of the hydraulic pressure P _C 20
To the operating hydraulic chamber 11a of the forward clutch 11 as the operating pressure of the forward clutch. Here, the forward clutch 11 can generate the fastening force proportional to hydraulic pressure P _C.

The current value i _X to the solenoid 23 is controlled by a control unit 30, and a signal from an input sensor group 31 described later is supplied to the control unit 30.

The control unit 30 is a vehicle-mounted type using a microcomputer, and has an input circuit 151, a RAM 152, a ROM 153, a CPU 154,
It is assumed that the circuit includes a clock circuit 155 and an output circuit 156.

The input circuit 151 is a circuit that converts an input signal from each sensor of the sensor group 31 into a digital signal that can be processed by the CPU 154 and inputs the digital signal. RAM1
Reference numeral 52 denotes a readable and writable memory for writing an input signal from each sensor, writing information being calculated by the CPU 154, and reading the written information.
Further, the ROM 153 is a read-only memory,
Information and the like necessary for the arithmetic processing in U154 are stored in advance, and the information is read out by a command from the CPU 154 as necessary.

The CPU 154 is a device that performs arithmetic processing on various types of input information in accordance with predetermined processing conditions, and performs processing of input information in creep prevention control, forward clutch operation control including fail-safe measures according to the present invention, and the like. Further, the clock circuit 155 includes the CPU 154.
Is a circuit for setting the calculation processing time in. The output circuit 156 is a circuit for outputting a control current signal i _X to the solenoid 23 as an actuator on the basis of the calculation result signal from the CPU 154.

In the present embodiment, as sensors constituting the input sensor group 31, a select position switch 161,
Idle switch 162, oil temperature sensor 163, output shaft speed sensor 164, engine speed sensor 165, turbine speed sensor 166, and brake switch 167
Shall be used.

The select position switch 161 is a switch for outputting a signal corresponding to the selected range (selected position) of the automatic transmission. In the present embodiment, the switch is turned ON when the selected range is in the neutral range (N range). ,
The selected range is the driving range (drive range; D range)
It is assumed that the switch is turned off and the switch signal _PSW is output only when.

The switch signal _PSW output from the select position switch 161 indicates that the range has been switched from the N range to the D range (N → D select operation has been performed). It is used as a signal to perform

The idle switch 162 is a switch for detecting whether or not the throttle valve of the engine is in a fully closed state (idle state). The switch is turned off when the throttle valve is in an open state and is turned on only when the throttle valve is in a fully closed state. It outputs a switch signal Id. Note that a throttle sensor may be used instead of the idle switch 162.

The oil temperature sensor 163 detects the transmission operating oil temperature (A
TF temperature) _Tm is a sensor that detects the oil temperature signal T
_Atf is output, and the output shaft speed sensor 164 is a sensor for detecting the speed No of the transmission output shaft. A signal output from the output shaft speed sensor 164 is used as a signal representing the vehicle speed.

The engine speed sensor 165, the rotational speed of the crankshaft 13 is a sensor for detecting the (engine speed) N _e, the turbine speed sensor 166, the rotation speed of the transmission input shaft 14 (turbine speed) a sensor for detecting the N _t.

The brake switch 167 is disposed on a brake pedal or the like, and is a sensor for detecting the operation of a foot brake or a side brake, and outputs a brake operation signal B when the brake is operated.

The CPU 154 executes the main routine of FIGS. 2 and 3 based on the input information from the input sensor group 31 to perform the creep prevention control and the start control from the creep prevention as follows. The subroutine 5 is executed to perform the fail-safe processing targeted by the present invention as described below.

First, in step 50 of FIG. 2, the signals _PSW , Id, T
_m, N _o, B reads, in step 51,
Fail-safe processing at the time of N → D selection in which the range is switched from the neutral (N) range to the traveling (D) range is performed as described later with reference to FIG.

In the next step 52, it is determined whether or not the driving range (D range) _{exists based on} the presence or absence of the signal _PSW. If the driving range, the control proceeds to step 53; if not, the control proceeds to step 57. To perform normal traveling control.

In step 53, it is determined whether or not the idle switch is in the idle state based on the presence or absence of the signal Id.
If it is in the idle state, the control proceeds to step 54, and if it is not in the idle state, the control proceeds to step 57 to perform normal traveling control.

In step 54, it is determined whether or not the brake is ON based on the presence or absence of the signal B. If the brake is ON, the control proceeds to step 55, and if the brake is OFF, the control proceeds to step 57 to perform the normal traveling control. Do.

[0050] At step 55, the vehicle speed to determine whether the vehicle is stopped in (transmission output shaft speed) N _o is approximately 0, and starts the operation of the anti-creep control at step 56 if N _o approximately 0 performs normal running control complete the N _o almost not 0 control to step 57.

Eventually, the operation of the creep prevention control in step 56 is started only when all of the four conditions of "running range, idle state, brake ON, and vehicle speed are almost 0" are satisfied. In other cases, normal traveling control is performed.

[0052] The In anti-creep at step 56, first, the working oil pressure P _c of the forward clutch 11, so as to abruptly to the initial setting pressure determined within a range in which the clutch does not slide out, a current value i _X of the solenoid 23 determined, then working oil pressure P _c is determined current value i _X to the solenoid 23 so as to gradually decrease at a predetermined gradient until the slip start clutch, the instantaneous after is expressed as output rotational speed difference of the torque converter 12 torque converter slip amount determines the current values i _X to the solenoid 23 to control the hydraulic pressure P _c to be maintained at a constant value that.

As described above, the operating oil pressure _Pc is rapidly reduced to the initial set pressure, and then gradually reduced at a predetermined gradient until the forward clutch 11 starts to slip, so that the forward clutch 11 is quickly slipped without releasing shock. , The creep prevention can be started with a high response, and thereafter, the feedback control of the operating oil pressure _Pc so that the torque converter slip amount is maintained at a constant value can realize the reliable creep prevention. .

After executing step 56, the control proceeds to step 61 of the start control program in FIG. FIG.
At step 61, the signal from the idle switch 162 Id, signal N _o from the output shaft speed sensor 164, reads a signal B from a brake switch 167, the next step 62, the idle of whether the idle switch ON signal Id It is determined whether or not the vehicle is in the idle state (accelerator OFF). If the accelerator switch is in the idle state (accelerator OFF), the control proceeds to step 63; Of the forward clutch engagement control (start control).

In step 63, it is determined whether or not the brake is ON based on the presence / absence of the signal B. If the brake is ON, the control proceeds to step 64, and if the brake is OFF, the control proceeds to step 66 to execute the predetermined operation when the accelerator is OFF. Is performed.

[0056] At step 64, it is determined whether or not the vehicle speed N _o is approximately 0, the control if N _o approximately 0 back after the step 61, the control When larger than N _o approximately 0 Step Proceeding to 66, the forward clutch engagement control at the time of accelerator OFF is performed.

After all, it is the case that “the creep prevention control is in operation and the idle state”, and the “brake OF
F or N _o > 0 ”, step 6
In step 6, the forward clutch engagement control is performed when the accelerator is off. In this forward clutch engagement control, the forward clutch 11 is slowly engaged.

This forward clutch engagement control is repeated until it is determined in the next step 67 that the engagement of the forward clutch has been completed. The determination of the forward clutch engagement completion, for example turbine speed and vehicle speed rotational speed difference with time became (Nt-N _o) is approximately 0, so as to determine the engagement completion.

At step 68, which is performed when the forward clutch engagement is completed, for which the determination at step 67 is YES, and after step 65, at which the forward clutch engagement control is performed when the accelerator is turned on, the creep prevention control is activated. End (OFF).

Next, the step shown in FIG. 2 according to the gist of the present invention will be described.
The fail-safe processing performed in step 51 will be described. This process
Is as shown in FIG. 4 and in step 71
Switching from N range to D range (N → D select operation)
Instant t in FIG. ₁Control
By proceeding to step 72 or later, fail-safe processing
If there is no N → D select operation, the
The control is performed without performing the fail-safe processing after step 72.
The process returns to step 52 in FIG.

[0061] In step 72, N → D select the engine speed during the operation N _e and the turbine speed N _t
Is read, and in step 73, the deviation ΔN between these two
₁ (see FIG. 6), and this is stored in memory. The rotational speed difference .DELTA.N _1, the engine speed N _e is the torque converter input rotational speed, because the turbine speed N _t is the torque converter output speed, the torque converter input rotational speed difference, i.e. the torque converter slip Express the amount.

At step 74, the set time Δ shown in FIG. 6 is _calculated from the transmission operating oil temperature Tm based on the map corresponding to FIG.
Search for and find t _S. Here, the set time Δt _S is N →
In time to set whether based on the D selection operation instant t ₁ is determined where the abnormality determination instantaneously longer the lower the transmission hydraulic oil temperature T _m, the length is forward at a low temperature even increased late in the clutch hydraulic pressure P _c (decrease delay of turbine speed N _t) increases to correspond to the time required for the turbine speed N _t is reduced to the abnormality determination can extent.

[0063] In step 75, a timer TM is started to measure the elapsed time from the N → D selection operation instant t _1. In the following, this elapsed time is referred to as a timer TM for convenience.
It is represented by TM using the same reference numeral.

Next, at step 76, the operating oil pressure _Pc of the forward clutch 11 is changed from N → as shown in FIG.
The OPM current i _X such as to jump to the initial set pressure P _S to D selection operation instant t ₁ is output to the solenoid 23, in the subsequent step 77, as shown the working oil pressure P _c of the forward clutch 11 in FIG. 6, the solid lines of The OPM current i _X is determined so as to increase at a predetermined gradient, and is output to the solenoid 23.

At step 78, the timer TM is started.
Set time Δt set in step 74 _SShows the above
Or not, that is, N → D select operation instant t₁From
Fixed time Δt_SHas elapsed and the instant t in FIG._TwoWhether or not
Is determined. Instant t_TwoIf not, step 77
Is repeatedly executed.
Clear TM to 0 and start up at step 75
Make the timekeeping described above possible.

[0066] At step 80, reads the engine speed N _e and the turbine speed N _t at the instant t ₂ in FIG. 6, in the next step 81, the deviation .DELTA.N _A between these two
(See FIG. 6), and this is stored in memory. The rotational speed difference .DELTA.N _A, a torque converter output rotational speed difference at the instant t _2, that is representative of the torque converter slip amount.

[0067] In step 82, with respect to N → D selection operation instant t torque converter slip amount .DELTA.N ₁ of ₁ obtained in step 73, the torque converter slip amount .DELTA.N _A at the instant t ₂ is over a predetermined value or more α It is determined whether or not the forward clutch 11 has become large, and if it has become large, there is no abnormality, and the forward clutch 11 can be engaged.
In step 83, the operating oil pressure P of the forward clutch 11
_c continue beyond the instant t determine the OPM current i _X to increase at a predetermined gradient as shown by the solid line in FIG. 6 outputs to the solenoid 23.

In step 84, the turbine speed N_tBut
The instant t in FIG._ThreeWhether or not
That is, whether the forward clutch 11 is completely engaged or not is determined.
Judge and repeat step 83 until the moment.
return. And the instant t_ThreeStep 85 when it reaches
At the operating hydraulic pressure P_cTo OPM16 as shown in FIG.
Pressure adjustment upper limit value (line pressure P which is the source pressure)_LSame value as
OPM current i _XIs output to the solenoid 23.

In step 82, even when the set time Δt _S has elapsed from the N → D select operation instant t ₁ to the instant t ₂ , the torque converter slip amount ΔN _A remains at the N → D select operation instant t _1. ΔN
_If it is determined that the value of the forward clutch 1 has not become larger than the predetermined value α, the program proceeds to step 86 where the forward clutch 1
It is determined that an abnormality of the control system that cannot make 1 engage has occurred.

In this case, in step 87,
Operate hydraulic clutch P _cOf OPM16
Pressure upper limit (line pressure P which is the original pressure)_LThe same value)
Una OPM current i_XIs output to the solenoid 23,
Line clutch P to line pressure P_LStronger by the same maximum pressure as
Systematically concluded. Therefore, even at the time of the abnormality
The forward clutch 11 remains unengaged
That the automatic transmission cannot transmit power.
The evil can be eliminated.

By the way, as in this embodiment, N
→ D select operation instant t₁The torque converter slip
Quantity ΔN₁And the set time Δt from the instant_SSoon after
Time t _TwoConverter slip amount ΔN at_AWith
It is considered abnormal when the deviation does not exceed the specified value α.
When determining, the instant t_TwoTorque converter slip amount
ΔN_AIs the engine speed N due to idle up etc.
_eAlso rises when ΔN_BAs is clear from the comparison with
The engine speed N_eChange due to the rise of
Since the above-mentioned abnormality judgment is performed accurately,
Therefore, fail-safe processing is performed despite unnecessary
It is possible to avoid the adverse effects such as

Further, as shown in FIG. 5, the set time Δt _S for determining the timing for performing the abnormality determination is increased as the oil temperature _Tm is lower, that is, the lower the oil determination _Tm is, the lower the oil determination _Tm becomes. it is so arranged delay from D selection operation instant t _1, engagement of the forward clutch 11 hydraulic pressure P _c at a low temperature is caused to rise delay as shown by the one-dot chain line in FIG. 6 (decrease in turbine speed N _t) Is delayed, it is possible to prevent the erroneous determination that the torque converter slip amount ΔN _A does not reach the predetermined value (ΔN ₁ + α) as an abnormality even at the instant t ₂ , and the abnormality determination accuracy at low temperature Can be increased.

In the above embodiment, the end
Gin rotation speed N_eAnd turbine speed N _tWith the rotation speed deviation
The expressed torque converter slip amount is equal to the set time Δt._S
Is normal or abnormal depending on whether it has increased by more than the specified value α
However, instead of this, the engine speed N_e
Turbine speed N with respect to_tTorque control expressed by the ratio
Speed ratio of the barter (e = N_t/ N_e) Based on normal or abnormal
May be determined.

[0074] That is, although not shown in the Figure 6, the speed ratio e ₁ of the torque converter in the N → D selection operation instant t _1, as shown in FIG. 5 in accordance with a set time from the instant Delta] t _S (oil temperature T _m the deviation between the speed ratio e _a of the torque converter, is determined to be normal if equal to or greater than a predetermined value, it is determined as abnormal unless equal to or larger than a predetermined value at the instant t ₂ of changing) has elapsed The same fail-safe processing as in the embodiment is performed.

Even when the abnormality is determined in this manner, the speed ratio e _A of the torque converter at the instant t ₂ is obtained.
(Not shown), since it is rarely changes under the influence of the increase in the engine speed N _e with such idle-up, as well as according to the embodiment, be performed accurately abnormality determination It is possible to achieve an operation and effect that it is possible to avoid the harmful effect of performing the fail-safe process although it is unnecessary.

The abnormality determination and fail-safe processing according to each of the above-described embodiments is not limited to the N → D select operation, but is performed again at step 65 or 66 in FIG. Needless to say, the same can be applied to such a case.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram showing a creep preventing device of an automatic transmission including a fail-safe device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a first half of a shift control program of the automatic transmission including a creep prevention control and a fail-safe process, which is executed by a control unit in the embodiment.

FIG. 3 is a flowchart showing a latter half of the transmission control program.

FIG. 4 is a flowchart showing a subroutine relating to a fail-safe process in the transmission control program.

FIG. 5 is a characteristic diagram of a set time used to determine a timing at which a fail-safe process should be performed based on an N → D select operation instant;

FIG. 6 is a time series change time chart of forward clutch operating oil pressure, engine speed, and turbine speed during an N → D select operation.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Creep prevention device of automatic transmission 11 Forward clutch (friction element during operation) 12 Torque converter (fluid transmission) 12 _p pump impeller 12 _t turbine runner 12 _S stator 13 crankshaft 14 transmission input shaft 16 oil pressure modulator ( Pressure control valve) 23 solenoid 30 control unit 31 input sensor group 161 select position switch 162 idle switch 163 oil temperature sensor 164 output shaft speed sensor 165 engine speed sensor 166 turbine speed sensor 167 brake switch

Claims (4)

[Claims] 1. An automatic transmission which receives the rotation of an engine via a fluid transmission device and shifts and outputs the engine rotation at a speed selected by a selective hydraulic operation of a plurality of friction elements. In order to reduce the transmission of creep torque by the fluid transmission device, the operating oil pressure of the friction element during operation is reduced by a pressure control valve to prevent the friction element from slipping, thereby preventing creep of the automatic transmission. In the device, a slip amount represented by a difference between input and output rotation speeds of the fluid transmission device at the moment when the engagement of the friction element is commanded including re-fastening from the slip state, and Of the slip amount of the fluid transmission device that is changed by gradually increasing the operating oil pressure of the friction element by the pressure control valve, a set time has elapsed from the instant of the engagement command. A fail-safe device for a creep preventing device for an automatic transmission, wherein an abnormality is determined when a slip amount deviation from the slip amount at the time is less than a set value. 2. The automatic transmission according to claim 2, wherein the rotation of the engine is input via a fluid transmission, and the engine rotation is shifted and output at a speed selected by a selective hydraulic operation of a plurality of friction elements. In order to reduce the transmission of creep torque by the fluid transmission device, the operating oil pressure of the friction element during operation is reduced by a pressure control valve to prevent the friction element from slipping, thereby preventing creep of the automatic transmission. In the device, a speed ratio represented by a ratio of an output rotation speed to an input rotation speed of the fluid transmission device at the moment when the engagement of the friction element is commanded including re-fastening from the slip state; In response to the speed ratio of the fluid transmission device, which changes by gradually increasing the operating oil pressure of the friction element by the pressure control valve, A failure safe device for a creep prevention device for an automatic transmission, wherein an abnormality is determined when a speed ratio deviation between the speed ratio and the speed ratio when the elapsed time does not exceed a set value. 3. The anti-creep device for an automatic transmission according to claim 1, wherein the set time is set longer according to the operating oil temperature of the automatic transmission as the operating oil temperature decreases. Fail-safe device. 4. The pressure control valve according to claim 1, wherein when the abnormality is determined, the pressure control valve is instructed to supply an operating oil pressure of a pressure adjustment upper limit value to the friction element. A fail-safe device for creep prevention devices for automatic transmissions.