JPH06323426A - Shift controller for automatic transmission - Google Patents

Abstract

PURPOSE:To provide constitution which can prevent over rotation of an engine at low-speed stage engine braking in a shift controller not having a shift valve. CONSTITUTION:Among pressures put out to circuits 16 and 18 in one range, a pressure for the circuit 16 actuates a forward clutch F/C, while a pressure for the circuit 18 is led to a cut-off valve 23. A controller 50 turns on a solenoid 24 in the one range, switches the cut-off valve 23 from a shown position, prohibits a gear speed over the second speed by draining a circuit 33 through a port 23a and engages a low-reverse brake LR/B by the pressure of the circuit 18 by making the circuit 18 communicate with a circuit 34. Thus, engine braking of a first speed can be obtained, but the controller 50 does not turn on the solenoid 24 while a car speed VSP detected by a sensor 52 is a car-speed value generating over rotation of an engine so as to prevent the over rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for reliably preventing an engine from over rotating in a low speed engine braking state of an automatic transmission.

[0002]

2. Description of the Related Art An automatic transmission selects a corresponding shift speed by selectively hydraulically operating (engaging) various friction elements (friction clutches and friction brakes), and changes the operating friction element to shift to another shift speed. Configure to do.

In the meantime, when changing gears, the applicant of the present invention is developing and using the method described in "NISSAN Maxima New Model Car Manual J".
Introducing the changes in the 30-series cars ”issued in August 1991 (FOO
No. 7671), the shift valve is made to respond to the gear shift command to distribute the forward shift stage selection pressure from the manual valve to the corresponding traveling friction element, and the traveling friction element is operated. Therefore, it has been customary to perform a predetermined gear shift.

However, if the gear shift is performed via the shift valve in this way, a valve for appropriately controlling the operating pressure of the traveling frictional element that has been actuated in response to the gear shift to reduce gear shift shock. And a circuit, and a valve and a circuit for appropriately controlling the operation timing of the traveling friction element to be actuated in order to reduce the shift shock, are separately required, and the shift control hydraulic circuit of the automatic transmission is required. It was inevitably complicated and expensive.

In order to solve this problem, in US Pat. No. 4,935,872, a shift valve is not used at all while the manual valve is set in the forward automatic shift range.
The forward speed selection pressure output from this manual valve is
By supplying / discharging to / from each traveling friction element under pressure regulation by an individual pressure regulating valve, and selectively activating the traveling friction element,
A shift control device for an automatic transmission has been proposed which is capable of selecting a predetermined shift speed.

According to such a proposed technique, it is possible to arbitrarily control the time-dependent change in the operating pressure of the traveling friction element and the rising timing thereof by means of the individual pressure regulating valves, and a gear shift shock can be obtained only by appropriately controlling the pressure regulating valves. It is possible to surely reduce the pressure, and it is not necessary to separately add a valve or a circuit for reducing the shift shock, and the structure of the automatic transmission can be made simple and inexpensive.

[0007]

However, the automatic transmission described in the above-mentioned "NISSAN Maxima New Vehicle Manual, Introduction of Changes to J30 Type Cars", issued in August 1991 (FOO7671). The following problems occur when it is used in the gear shift mechanism.

That is, in this automatic transmission, the low speed stage (first
(Speed) is performed via a one-way clutch (low one-way clutch), and upshifting from a low-speed stage to a high-speed stage is completed by the overrun of the one-way clutch. We are making it easier to take measures against shocks.

However, since the above-mentioned one-way clutch renders the engine brake ineffective in the low speed stage, in case this engine braking is required, the one-way clutch is provided with a friction element for engine braking in parallel. Is activated when the engine brake is requested to disable the above one-way clutch overrun.

By the way, when the engine braking is applied in this way, when the vehicle speed is high, the engine is driven backward (over-rotated) by the wheels up to the permissible rotational speed because the vehicle is in the low speed stage, and the engine durability is increased. Sex is impaired.
In view of this problem, in the shift control hydraulic circuit described in the above document, the shift valve is provided with a function of preventing shifting to the low speed stage until the vehicle speed decreases to a rotational speed at which engine overspeed does not occur. It was

However, the forward gear selection pressure is supplied to and discharged from each traveling friction element under the pressure regulation by the individual pressure regulating valve, and the traveling friction element is selectively actuated to select the predetermined gear stage. When the above shift control device is used, it is not possible to take measures against the excessive rotation of the engine because there is no shift valve.

The present invention solves the above problems by constructing a shift control device capable of preventing engine over-rotation during engine braking even without a shift valve, that is, without relying on this. The purpose is to

[0013]

To this end, the present invention provides a forward gear selection pressure output from the manual valve to each traveling friction element while the manual valve is in the forward automatic shift range. By supplying / discharging under pressure regulation by the pressure regulating valve and selectively actuating the friction element for traveling, it is possible to select a predetermined gear stage, and while the manual valve is in the low speed engine brake range, Of the output forward speed selection pressure and engine brake range pressure, the forward speed selection pressure is used to operate the corresponding traveling friction element to select the low speed step, and the engine brake range pressure is used to select the engine braking friction element. In an automatic transmission that is operated so as to obtain engine braking at the low speed stage, when the low speed engine brake state is set, An engine overspeed determination means for determining whether or not the gin is in an overspeed vehicle range, and an engine from the manual valve to the engine brake friction element in the vehicle speed range in which the engine is overspeed in response to a signal from the engine overspeed determination means. And a shutoff valve for shutting off the brake range pressure circuit.

[0014]

Operation: With the manual valve in the forward automatic shift range, the automatic transmission supplies and discharges the forward shift speed selection pressure output from the manual valve to each traveling friction element under the pressure regulation by the individual pressure regulating valve. Then, the predetermined gear stage is selected by selectively operating the traveling friction element. Then, in the state where the manual valve is in the low speed engine brake range, of the forward speed selection pressure and the engine brake range pressure output from the manual valve, the corresponding traveling friction element is activated by the forward speed selection pressure. To select the low speed stage, and at the same time, activate the engine braking friction element by the engine brake range pressure to enable engine braking at the low speed stage.

By the way, the engine over-rotation determining means determines whether or not the engine speed is in a vehicle speed range in which the engine is over-rotated when the engine is braked at the low speed stage. The pressure circuit is shut off so that engine brake range pressure is no longer supplied from the manual valve to the engine brake friction element. Therefore,
The engine braking friction element is not engaged in the vehicle speed range, and the gear shift control device without the shift valve can prevent the engine from over-rotating.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a power transmission train and an engagement logic table of various friction elements of an automatic transmission to which the gear shift control device of the present invention is applied. This transmission train is the same as the gear transmission mechanism in the automatic transmission described in the above-mentioned document issued by the applicant of the present application, and rotational power from an engine crankshaft (not shown) is transmitted via the torque converter 1. An input shaft 2 and a first planetary gear set 4 and a second planetary gear set 5 which are coaxial with the input shaft 2 and are coaxially arranged on the input and output shafts;
It is composed of various friction elements described later.

The first planetary gear set 4 is a normal simple planetary gear set including a sun gear 4S, a ring gear 4R, a pinion 4P meshing with these, and a carrier 4C rotatably supporting the pinion 4P, and the second planetary gear set 5 is also included. Sun gear 5
A simple planetary gear set including S, a ring gear 5R, a pinion 5P and a carrier 5C.

Next, various friction elements that control the shift control will be described. The carrier 4C can be appropriately connected to the input shaft 2 via the high clutch H / C, the sun gear 4S can be appropriately fixed by the band brake B / B, and can be appropriately connected to the input shaft 2 by the reverse clutch R / C. To do. The carrier 4C can be further appropriately fixed by a multi-plate low reverse brake LR / B and prevents reverse rotation (rotation in the direction opposite to the engine) via the low one-way clutch LO / C. The ring gear 4R is integrally connected to the carrier 5C and drivingly connected to the output shaft 3, and the sun gear 5S is connected to the input shaft 2. Ring gear 5R is overrun clutch OR / C
In addition to being able to be appropriately coupled to the carrier 4C via the, the carrier is correlated with the carrier 4C via the forward one-way clutch FO / C and the forward clutch F / C. Forward one-way clutch FO / C is forward clutch F
In the coupled state of / C, the ring gear 5R is coupled to the carrier 4C in the reverse rotation direction (direction opposite to the engine rotation).

High clutch H / C, reverse clutch R
/ C, low reverse brake LR / B, overrun clutch OR / C, and forward clutch F / C, respectively.
The band brake B / B is actuated by the supply of hydraulic pressure to perform the above-described appropriate coupling and fixing, but the band brake B / B is particularly designed as shown in the table of FIG. 1 for the second speed servo apply chamber 2A, the third speed servo release chambers 3R and 4 It has a fast servo apply chamber 4A, which is opened in a normal state and is fastened by supplying pressure to only the chamber 2A. It is opened when pressure is supplied to the chamber 3R as well as the chamber 2A, and to the chamber 4A in addition to the chambers 2A and 3R. Shall be fastened when supplying pressure.

The power transmission train of FIG. 1 includes friction elements B / B and H.
/ C, F / C, OR / C, LR / B, R / C are engaged in various combinations as shown in the table in the figure (shown by a circle) to make friction elements FO / C, LO. Along with the appropriate operation (engagement) of / C, the rotational states of the elements constituting the planetary gear sets 4 and 5 are changed, thereby changing the rotational speed ratio of the output shaft 3 to the rotational speed of the input shaft 2. It is possible to obtain a shift speed of four forward speeds and one reverse speed. 1 also indicates the operation (hydraulic inflow), the Δ mark indicates the friction element for engine brake which should be operated when engine braking is required. Then, while the overrun clutch OR / C is operated as indicated by a triangle, the forward one-way clutch FO / C juxtaposed to this is kept unreleasable to enable the engine braking, and the low reverse brake LR.
Of course, the low one-way clutch LO / C juxtaposed with / B is kept non-releasable during engine operation to enable engine braking.

Further, the forward clutch F / in the table of FIG.
The dotted circle in C indicates that this clutch remains engaged for the convenience of the shift control hydraulic circuit even though it is not involved in power transmission at the fourth speed.

FIG. 2 shows a shift control hydraulic circuit of the gear shift mechanism. Reference numeral 11 denotes a regulator valve, which regulates the hydraulic oil from the oil pump 12 to a predetermined line pressure by a well-known action, and outputs this to the circuit 13 so as to be used as all the source pressures of the automatic transmission. The line pressure from this circuit 13 is supplied to the manual valve 14, the pilot valve 15 and the like.

The manual valve 14 is manually operated according to the traveling mode desired by the driver, and is set to P when the vehicle is parked (stopped).
(N) When the range is set, the line pressure of the circuit 13 is not supplied to any output circuit, and the entire line is drained. Manual valve 14
When the automatic forward shift (D) range is set for the desired automatic forward shift, the line pressure of the circuit 13 is changed to the circuit 16 as shown in the figure.
To the forward gear selection pressure (D range pressure), drain all other output circuits, and set the line pressure of the circuit 13 to the 2 range when the 2nd speed engine brake running is desired.
7 is also output as 2 range pressure, the other output circuits are drained, and the line pressure of the circuit 13 is set when the engine brake (1) range is set for the first speed engine brake running.
8 is also output as engine brake range pressure (1 range pressure), and the other output circuit is drained. However,
In this example, the two range pressures are not required, so the circuit 17 is closed. Further, the manual valve 14 outputs the line pressure of the circuit 13 as the reverse gear selection pressure (R range pressure) only to the circuit 19 when the reverse travel is desired and the R range is set, and the other output circuits are all drained. And

The D range pressure of the circuit 16 is applied to the operation of the forward clutch F / C via the one-way orifice 20, and the operation is gently performed by the one-way orifice 20 and the accumulator 21, whereby the forward clutch F / C is operated. The fastening shock, that is, the N → D select shock is alleviated.

The pilot valve 15 reduces the line pressure from the circuit 13 to a constant pilot pressure, which is set in the circuit 22.
ON / OFF solenoid 24 of shutoff valve 23, ON / OFF solenoid 26 of switching valve 25, pressure regulating valve 27
Duty solenoid 28, pressure regulator 29 duty solenoid 30, pressure regulator 31 duty solenoid 3
2 shall be supplied.

Solenoids 24, 26, 28, 30, 32
When OFF, they do not apply the signal pressure to the corresponding valves 23, 25, 27, 29, 31 by draining the pilot pressure from the circuit 22, and keep these valves in the normal state,
At this time, the signal pressure is applied to the corresponding valves 23, 25, 27, 29, 31 using the pilot pressure from the circuit 22 as the original pressure. However, the duty solenoids 28, 30, 31
It is assumed that the pilot pressure from the circuit 22 is drained according to the drive duty, and the signal pressure applied to the corresponding valves 27, 29, 31 can be adjusted according to the drive duty.

The shutoff valve 23 turns off the solenoid 24.
At this time, the circuit 16 is connected to the circuit 33, the circuit 18 is connected to the drain port 23a, the circuit 34 is connected to the drain port 23b, and when the solenoid valve 24 is turned on, the circuit 16 is switched to the reverse position. The circuit 33 is cut off, the circuit 33 is connected to the drain port 23a, and the circuits 18 and 33 are connected to each other.

The circuit 33 is connected to the input ports of the pressure regulating valves 27, 29 and 31, and these pressure regulating valves are solenoids 28 and 3.
In response to the duty control pressure from 0, 32, the pressure from the circuit 33 is used as the original pressure to increase the pressure in the output circuits 35, 36, 37, and the excess pressure is used as the drain port 27a, 29a, 3
The output circuits 35, 36, and 3 can be eliminated by removing the output circuits from 1a.
It is assumed that the pressure of 7 is adjusted to a value corresponding to the drive duty of the solenoids 28, 30, 32.

The switching valve 25 is an OF of the solenoid 26.
At the time of F, it becomes the normal position shown in the figure, and the circuit 35 is connected to the drain port 25a, and the circuit 38 is connected to the drain port 25b
Although the circuit 39 branched from the circuit 16 is connected to the circuit 40,
When the solenoid 26 is turned on, it switches to the reverse position and the circuit 3
8 is connected to the circuit 35 and circuit 40 is connected to the drain port 25b.

The pressure of the circuit 38 is supplied to the 4-speed servo apply chamber 4A of the band brake B / B via the one-way orifice 41 to be used for the operation of the band brake B / B, and this operation is performed by the one-way orifice 41 and the accumulator 42. By gently performing with, the shift shock at the time of shifting performed by engaging the band brake B / B is mitigated.

The circuit 36 is connected to the third speed servo release chamber 3R and the high clutch H / C of the band brake B / B, and the circuit 37 is connected to the second speed servo apply chamber 2A of the band brake B / B. The circuit 40 is connected to the overrun clutch OR / C via an overrun clutch pressure reducing valve 43, and the pressure of the circuit 40 is reduced to a predetermined value by the overrun clutch pressure reducing valve 43 to reduce the overrun clutch OR.
/ C operation.

The circuit 34 is a low reverse brake L via a 1-range pressure reducing valve 44, a shuttle valve 45 and a circuit 46.
Connected to R / B, the pressure of circuit 34 is reduced to 1 range pressure reducing valve 44
Low pressure brake LR / B
Shall be provided for the operation of.

Finally, the pressure of the circuit 19 is supplied to the reverse clutch R / C via the one-way orifice 47 to be used for the operation of the reverse clutch R / C, and this operation is gently performed by the one-way orifice 47 and the accumulator 48. By doing so, the engagement shock of the reverse clutch R / C, that is, the N → R select shock is alleviated.

Circuit 19 is further connected via circuit 49 to the remaining input port of shuttle valve 45, through which circuit 19 is also connected to the low reverse brake LR / B.

The ON / OFF control of the solenoids 24 and 26 and the duty control of the solenoids 28, 30 and 32 are executed by the controller 50 as the engine over-rotation determining means. A signal from the throttle opening sensor 51 that detects the opening TH, a signal from the vehicle speed sensor 52 that detects the vehicle speed VSP, and the manual valve 14
Signal R from the range sensor 53 for detecting the selected range of
Enter NG. Based on these input information, the controller 50 performs a normal gear shift for each selected range through the control of each solenoid according to the logic table of FIG. 3 and, according to the control program of FIG. It shall have a protective effect.

The operation of the above embodiment will be described below. When the manual valve 14 is set to the D range in the desire of the D range forward automatic shift, the manual valve 14 outputs the line pressure of the circuit 13 to the circuit 16 as the forward shift stage selection pressure. On the other hand, this pressure reaches the forward clutch F / C via the one-way orifice 20 and operates it, but at this time, the engagement of the forward clutch F / C is gently performed by the one-way orifice 20 and the accumulator 21, and the engagement shock is alleviated. To be done.

Here, the controller 50 includes the sensors 51,
A suitable shift stage is calculated from the engine throttle opening TH detected at 52 and the vehicle speed VSP, and when this is the first speed, only the solenoids 24 and 26 are turned on as shown in FIG.
To do.

Turning on the solenoid 24 switches the shut-off valve 23 from the illustrated position to the reverse position, shuts off the pressure reaching the shut-off valve 23 from the circuit 16 at this time, communicates the circuit 33 to the drain port 23a, and further connects the circuit 34 to the circuit. It leads to 18. Since the circuit 18 is drained in the D range of the manual valve 14, the circuit 34 is also drained, and the low reverse brake LR / B is not activated in this circuit. Also, since the circuit 33 is drained as described above,
All the rooms 2A, 3 of the band brake B / B related to the circuit 33
The R, 4A and the high clutch H / C are also drained, and the band brake B / B and the high clutch H / C are not operated.

When the solenoid 26 is turned on, the switching valve 25 is switched from the illustrated position to the reverse position to allow the circuits 35 and 38 to communicate with each other and the circuit 40 to the drain port 25b.
R / C to keep it inactive.

Since the circuit 19 is drained in the D range of the manual valve 14, the reverse clutch R / C is not activated in this circuit.

As described above, in the gear shift mechanism of FIG. 1, only the forward clutch F / C is operated, and the first forward movement is coupled with the engagement of the forward one-way clutch FO / C and the low one-way clutch LO / C. You can choose the speed.

The controller 50 controls the engine throttle opening TH detected by the sensors 51 and 52 and the vehicle speed VSP.
When it is calculated that the preferred gear position is the second speed, the solenoid 24 is turned off and the solenoid 32 is turned on even if the solenoid 26 is turned on as in the first speed as shown in FIG.
Is turned on under the duty control described later.

When the solenoid 24 is turned off, the shut-off valve 23 is set to the position shown in the figure, the pressure from the circuit 16 is output to the circuit 33, and the circuit 34 is connected to the drain port 23b to keep the low reverse brake LR / B in the inoperative state. . Circuit 33
Pressure reaches the pressure regulating valves 27, 29 and 31, but since the controller 50 keeps the drive duty of the solenoids 28 and 30 at 0%, the pressure is not output to the circuits 35 and 36, and the bands related to these circuits are controlled. The working pressure is not supplied to the chambers 4A, 3R of the brake B / B and the high clutch H / C. By the way, when turning on the solenoid 32, the controller 50 gradually increases the drive duty from 0%. As a result, the pressure in the circuit 37 also gradually increases, and this pressure reaches the second speed servo apply chamber 2A of the band brake B / B to gradually engage the band brake B / B.

Therefore, in the gear shift mechanism of FIG. 1, the forward second speed can be selected by the operation of the forward clutch F / C and the band brake B / B together with the engagement of the forward one-way clutch FO / C. it can.

The controller 50 uses the engine throttle opening TH detected by the sensors 51 and 52 and the vehicle speed VSP.
When it is calculated from the above that the preferred gear is the third speed, the solenoid 30 is turned on under the duty control which will be described later in addition to the state of the second speed as shown in FIG. The drive duty of the solenoid 30 is gradually increased from 0%.
The pressure at 6 is also gradually increased. This pressure is the band brake B /
B 3rd servo release chamber 3R and high clutch H /
At C, the band brake B / B is released and the high clutch H / C is engaged.

Therefore, in the gear shift mechanism of FIG. 1, the forward third speed can be selected by the operation of the forward clutch F / C and the high clutch H / C together with the engagement of the forward one-way clutch FO / C. it can.

The controller 50 controls the engine throttle opening TH detected by the sensors 51 and 52 and the vehicle speed VSP.
When it is calculated from the above that the preferred gear position is the fourth speed (overdrive), the solenoid 28 is added to the state of the third speed as shown in FIG. The drive duty of the solenoid 28 is gradually increased from 0%, so that the pressure of the circuit 35 is gradually increased. This pressure reaches the fourth speed servo apply chamber 4A of the band brake B / B via the switching valve 25 and the circuit 38, and re-engages the band brake B / B. By the way, at this time, the one-way orifice 41 and the accumulator 42 of the circuit 38 can smoothly re-engage the band brake B / B to alleviate the engagement shock.

Therefore, the gear shift mechanism of FIG. 1 can select the fourth forward speed by operating the band brakes B / B and the high clutch H / C. Since the forward clutch F / C does not participate in power transmission at the fourth speed, it is decided to keep the engaged state for convenience of the hydraulic circuit.

When the driver issues a command to prohibit the fourth speed (overdrive) by an unillustrated OD (overdrive) prohibition switch, the controller 50 turns the solenoid 28 on from the fourth speed as shown in FIG. The solenoid 26 is also turned off together with turning off. Solenoid 2
When the switch 6 is turned off, the switching valve 25 is switched to the position shown in the figure, and the circuit 38 is connected to the drain port 25b to drain the 4th-speed servo apply chamber 4A of the band brake B / B, and the circuit 16 is connected between the circuits 39 and 40. Supply pressure to overrun clutch OR / C. The drain of the 4th-speed servo apply chamber 4A causes the gear brake mechanism of FIG. 1 to be downshifted to the 3rd speed by releasing the band brake B / B, and the pressure is supplied to the overrun clutch OR / C. Then, the gear shift mechanism of FIG. 1 is brought into a state where engine braking at the third speed is possible.

Manual valve 1 in the hope of running in the 2nd range 2nd speed engine brake
When 4 is set to the 2 range, the manual valve 14 outputs the line pressure of the circuit 13 to the circuit 16 as the forward speed selection pressure,
The line pressure of the circuit 13 is also output to the circuit 17. But,
Since the pressure to the circuit 17 is not used in this example, the manual valve 14 acts on the shift control hydraulic circuit in the same manner as in the D range.

On the other hand, in the two ranges, as shown in FIG. 3, the controller 50 turns on only the solenoid 32, and differs from the second speed in the D range in that the solenoid 26 is turned off.

ON of the solenoid 32 is band brake B
By engaging / B and engaging the forward clutch F / C, the transmission gear mechanism of FIG. 1 is set to the second speed selection state as in the D range second speed.

When the solenoid 26 is turned off, the switching valve 25 is set to the position shown in the figure, and the pressure in the circuit 16 is supplied to the overrun clutch OR / C through the circuits 39 and 40. As a result, the overrun clutch OR / C is engaged, and the gear shift mechanism of FIG. 1 can be brought into a state where engine braking at the second speed is possible, as in the case where the overdrive is prohibited.

Manual valve 1 in the hope of running in the 1st range 1st speed engine brake
When 4 is set to 1 range, the manual valve 14 outputs the line pressure of the circuit 13 to the circuit 16 as the forward speed selection pressure,
The line pressure of the circuit 13 is also output to the circuit 18.

On the other hand, as shown in FIG. 3, the controller 50 turns on only the solenoid 24 in this one range, and differs from the above-described first speed in the D range in that the solenoid 26 is turned off.

When the solenoid 24 is turned on, the shut-off valve 23 is set to the position opposite to the position shown in the figure, the pressure reaching the shut-off valve 23 from the circuit 16 is shut off here, the circuit 33 is connected to the drain port 23a, and the circuit 34 is further connected to the circuit. It leads to 18. The drain of the circuit 33 prevents the selection of gears of the second speed or higher,
Therefore, the transmission gear mechanism of FIG. 1 is brought into the first speed selection state.

Further, since the circuit 18 outputs the line pressure of the circuit 13 in the one range, the circuits 18 and 34 are connected to each other by engaging the low reverse brake LR / B. Becomes At this time, the low reverse brake LR / B changes its operating pressure to the 1-range pressure reducing valve 4
It goes without saying that the fastening capacity is appropriately adjusted by appropriately reducing the pressure by No. 4.

In this one range, the controller 50 turns off the solenoid 26 as shown in FIG.
The switching valve 25 is at the position shown, and the overrun clutch OR / C is engaged.

Therefore, the gear shift mechanism of FIG. 1 is in the same state as when the first speed in the D range is selected, in addition to the low reverse brake LR / B and the overrun clutch OR / C.
Thus, the engine braking in the first speed can be generated.

By the way, at the time of selecting to one range, the controller 50 sets the solenoid 24 to the O position as described above.
At the time of N, this is controlled based on the control program of FIG. That is, first, in step 61, the vehicle speed VSP and the selection range RNG are read, and in step 62 it is checked whether or not one range is being selected, and in step 63, the vehicle speed VSP is the first speed and the lower limit of the vehicle speed range in which engine over-rotation occurs. It is checked whether the value is Vs or more.

Since the control of the solenoid 24 in FIG. 4 is not required except for the 1 range, the control is ended as it is and the solenoid 24 is turned on and off according to the logic table of FIG. If .gtoreq.Vs, it means that the vehicle speed is in the range where the engine is over-rotated. Therefore, in this case as well, the control is terminated and the solenoid 24 is kept off. As a result, the shut-off valve 23 is maintained at the position shown in FIG. 2, the low reverse brake LR / B is not operated, and the gear transmission mechanism of FIG. Can be avoided.

However, if the vehicle speed VSP is less than the set vehicle speed Vs at the time of selecting one range, or if the initial vehicle speed VSP is equal to or higher than the set vehicle speed Vs and then drops below the set vehicle speed Vs, the engine brakes the engine. Since there is no excessive rotation, the solenoid 24 is immediately turned on in step 64 to bring the gear shift mechanism of FIG.

When the manual valve 14 is set to the R range in order to drive the R range backward, the manual valve 14 changes the line pressure of the circuit 13 to the circuit 19
It is output as the reverse gear selection pressure. On the other hand, this pressure reaches the reverse clutch R / C via the one-way orifice 47 and operates it. At this time, the engagement of the reverse clutch R / C is gently performed by the one-way orifice 47 and the accumulator 48, and the engagement shock is generated. Will be alleviated. The pressure in circuit 19, on the other hand, is circuit 49,
The low reverse brake LR / B is reached via the shuttle valve 45 and the circuit 46 and is activated.

Therefore, the gear shift mechanism of FIG. 1 can select the reverse shift speed by operating the reverse clutch R / C and the low reverse brake LR / B.

The pressure regulating valve 27 and the duty solenoid 28 in the above example can be omitted when the relationship of the pressure receiving areas among the chambers 2A, 3R, 4A of the band brake B / B is appropriately determined. , In this case the circuit 35 is directly connected to the circuit 33.

[0066]

As described above, the shift control device of the present invention is defined by claim 1.
In the vehicle speed range where the engine is excessively rotated at the time of engine braking at the low speed stage (first speed in the illustrated example), the means for determining this (the controller 5 in the illustrated example
0), a shut-off valve (shut-off valve 23 in the illustrated example) is provided to prevent the operating pressure from being supplied to the friction element for engine braking. Is supplied to and discharged from each traveling friction element under pressure regulation by individual pressure regulating valves (pressure regulating valves 27, 29, 31 in the illustrated example), and the traveling friction element is selectively operated,
Even when using the shift control device capable of selecting the predetermined shift speed without the shift valve, it is possible to reliably prevent the engine from being excessively rotated during engine braking at the low speed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a power transmission train of an automatic transmission to which a gear shift control device of the present invention is applied together with a fastening logic table of various friction elements.

FIG. 2 is a hydraulic circuit diagram showing an embodiment of a shift control device of the present invention applied to a shift control hydraulic circuit of the transmission train.

[Fig. 3] O of a solenoid in the shift control hydraulic circuit
7 is a logical table showing a relationship between N, OFF and a selected shift stage.

FIG. 4 is a flowchart showing a control program for a shutoff valve solenoid that is executed by the controller in the same example when one range is selected.

[Explanation of symbols]

1 torque converter 2 input shaft 3 output shaft 4 first planetary gear set 5 second planetary gear set F / C forward clutch (travel friction element) B / B band brake (travel friction element) FO / C forward one-way clutch H / C High clutch (friction element for running) OR / C Overrun clutch R / C Reverse clutch LR / B Low reverse brake (friction element for engine brake) 11 Regulator valve 12 Oil pump 14 Manual valve 15 Pilot valve 23 Shut-off valve 24 Shut-off valve Solenoid 25 Switching valve 26 Switching valve solenoid 27 Pressure regulating valve 28 Pressure regulating valve Duty solenoid 29 Pressure regulating valve 30 Pressure regulating valve Duty solenoid 31 Pressure regulating valve 32 Pressure regulating valve Duty solenoid 45 Shuttle valve 50 Controller (Engine overspeed discrimination means) 51 Throttle opening Sensor 52 Vehicle speed sensor 5 3 range sensor

Claims (1)

[Claims] 1. While the manual valve is in the forward automatic shift range, the forward shift speed selection pressure output from the manual valve is supplied to and discharged from each traveling friction element under pressure regulation by an individual pressure regulating valve, and traveling is performed. By selectively actuating the friction element for use, a predetermined gear can be selected. While the manual valve is in the low speed engine brake range, the forward gear selection pressure and the engine brake range output from the manual valve can be selected. Of the pressures, the forward traveling gear selection pressure is used to operate the corresponding traveling friction element to select the low speed gear, and the engine braking range pressure is used to operate the engine braking friction element to operate the engine brake at the low speed gear. In the automatic transmission thus obtained, it is determined whether or not the vehicle is in the vehicle speed range in which the engine is excessively rotated when the engine is in the low-speed engine brake state. An engine overspeed determination means and a shutoff valve for shutting off the engine brake range pressure circuit from the manual valve to the friction element for engine braking in a vehicle speed range in which the engine overspeeds in response to a signal from the means are provided. A shift control device for an automatic transmission characterized by the above.