JP2000205395A - Neutral controller for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutral controller for automatic transmission for vehicle capable of suppressing fluctuation of engine rotation speed when neutral control is started. SOLUTION: In a neutral controller for automatic transmission provided with an automatic transmission transmitting a driving force from an engine to a drive wheel and a main control part 1 controlling the operation of the engine and the automatic transmission, a neutral control means 1a neutral- controlling the automatic transmission under a predetermined condition, an ISC control means 1c controlling an idle rotation speed of the engine by adjusting a flow rate of air so that it becomes a predetermined target value, and a neutral control permission means 1b permitting the start of neutral control for the neutral control means 1a in accordance with rotation speed of the engine are provided in the main control part 1. The neutral control permission means 1b is provided with a rotation speed judging function permitting neutral control when rotation speed of the engine drops below a predetermined value in the vicinity of the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutral control device for an automatic transmission for a vehicle, and more particularly to a neutral control device for an automatic transmission for a vehicle capable of maintaining a constant engine speed in response to various conditions. It relates to a control device.

[0002]

2. Description of the Related Art Conventionally, as a control device for an automatic transmission, Japanese Patent Publication No. 63-33024 and Japanese Patent Publication No. 63-35
As disclosed in Japanese Patent Application Laid-Open No. 869 and Japanese Patent Publication No. 63-33585, there is a neutral control device that automatically sets a neutral state when an accelerator is off and a vehicle stops.

[0003] The prior art aims to reduce the load applied to the engine and to improve the fuel economy as a whole by automatically setting the neutral state when the vehicle stops with the accelerator off in the D range. In general, in an automatic transmission, the operation state of a brake is added to one of the conditions for setting a neutral state in order to enable creep running (low-speed running when the accelerator is off). The neutral control is performed only when the brake is operated.

[0004] As described above, the conditions for starting the neutral control include a shift position in the D range, an accelerator off, a vehicle stop, and a brake operation. In general, even if all of these conditions are satisfied, neutral control is not started within a predetermined time. The reason is to reliably detect that all of these conditions are satisfied, and to confirm that the operation is not a temporary operation by the driver so that control is not started carelessly.

On the other hand, if one of the conditions for starting the neutral control is not satisfied, the neutral control is immediately released. As a result, the vehicle is controlled so as to be able to quickly accelerate as intended by the driver.

[0006] In addition to the neutral control, a device (ISC) for controlling an idle rotation speed by adjusting a flow rate of air introduced into an engine is generally known. In some ISCs, an air passage that bypasses a throttle valve of an engine is provided, and the throttle of the air passage is adjusted by an actuator. In the above-described ISC control device, feedback control is performed to bring the idle rotation speed close to a predetermined target value, and the idle rotation speed can be maintained substantially constant.

In combination with an automatic transmission, a traveling range (R, D, 2, L) and a neutral range (P,
N), the driving load of the engine is different. For this reason, when switching between the traveling range and the neutral range, the driving load changes abruptly. At this time, fluctuations in the engine rotation speed and engine stall may occur only with the feedback control. This is because it is not possible to immediately supply the air flow rate required to maintain the idle rotation speed at the predetermined value, and it takes a certain time. For this reason, necessary air flow rates are set in advance in the travel range and the neutral range, and feedback is started based on the above set values when switching between the travel range and the neutral range.

The so-called learning control for reflecting and storing the result of the feedback is performed because the required air flow rate in the above-mentioned travel range and the neutral range changes due to individual differences between vehicles, changes over time, and the like. In order to prevent the idling air flow rate from being erroneously learned, a necessary condition for learning the idling air flow rate is that the rotational speed is stable near the target value for a predetermined period by feedback. With these ISC controls, it is possible to quickly supply an appropriate air flow rate and reduce fluctuations in the engine rotation speed in response to fluctuations in the engine drive load caused by switching between the running range and the neutral range.

In the case of a general automatic transmission, the driving load of the engine in the idle state is of two types, that is, a driving range and a neutral range. However, as disclosed in JP-B-63-35869, the driving load also differs during the neutral control. That is, in the neutral control, the forward running clutch is controlled to be in the slip state in the travel range at the time of idling, and thus the neutral control is not in the complete neutral state. As a result, the engine drive load is increased by the drag of the clutch, so that the engine drive load is intermediate between the neutral range and the travel range. For this reason, it is necessary to newly set a learning value of the idle air flow rate for the neutral control, and there are three learning values of the idle air flow rate: the traveling range, the neutral range, and the neutral control.

[0010]

However, each of the above-mentioned prior arts has the following disadvantages. That is, when the vehicle is stopped by releasing the accelerator from the normal running state,
In order to avoid engine stall, the idle air flow rate required for the ISC control is set to a relatively large value in advance. Then, the bypass air flow rate is reduced so that the engine rotation speed gradually decreases to the target idle rotation speed, and thereafter, feedback is started. When such control is performed, there is a possibility that the neutral control is started before the engine rotation speed decreases to the idling rotation speed, and there is the following problem.

That is, when the neutral control is started in a state where the actual engine rotation speed is higher than the target idle rotation speed, the rotation speed is greatly reduced immediately after the neutral control is started because of a large difference in the number of rotations. Control is performed. As a result, the engine rotation speed undershoots, causing a large fluctuation in the engine rotation speed. As a result, there is a problem that the driver feels strange.

As a countermeasure against such a problem, a method is conceivable in which, when neutral control is started in a state where the engine speed is higher than the idle speed, feedback is not immediately started but the speed is gradually reduced. Can be However, if the idle air flow rate at the time of starting the neutral control is not appropriately set, a fluctuation in the engine rotation speed is expected. In addition, the idle speed changes according to the running conditions and environmental changes, and is not necessarily a specific engine speed.
There has been an inconvenience that setting the air flow rate is complicated and difficult.

[0013]

An object of the present invention is to provide a neutral control device for an automatic transmission for a vehicle, which can solve the disadvantages of the prior art, and in particular, can suppress fluctuations in the engine speed when starting the neutral control. That is its purpose.

[0014]

In order to achieve the above object, the present invention provides an automatic transmission for transmitting a driving force from an engine to driving wheels, and a main control unit for controlling the operation of the engine and the automatic transmission. In the neutral control device for an automatic transmission, a neutral control means for neutrally controlling the automatic transmission under a predetermined condition in a main control unit, and a predetermined idle speed of the engine by adjusting an air flow rate to a predetermined speed. An ISC control unit that performs learning control so as to attain a target value, and a neutral control permission unit that permits the neutral control unit to start the neutral control in accordance with the rotation speed of the engine. The neutral control permission means has a rotation speed determination function for permitting the neutral control when the rotation speed of the engine becomes equal to or less than a predetermined value near the target value.

With the above configuration, for example,
When the vehicle shifts from the running state to the stopped state, the rotation speed of the engine gradually decreases. At this time, if the neutral control is started before the rotation speed of the engine has not completely decreased to near the target value, the rotation speed will rapidly decrease due to the feedback control. However, in the present invention, the neutral control is started by the neutral control permission means on condition that the rotation speed has been reduced to the predetermined rotation speed. For this reason, the fluctuation of the rotation speed described above does not occur.

[0016]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a system diagram of the present invention. The present invention has an automatic transmission 8 and an engine 2 and a main control unit 1 for controlling the operations of the automatic transmission 8 and the engine 2. Various signals are input to the main control unit l. Specifically, there are a throttle opening signal from a throttle opening sensor 3 for detecting a throttle opening (corresponding to a load) of the engine 2 and a vehicle speed signal from a vehicle speed sensor 4 for detecting a vehicle speed.
The signals input to the main control unit 1 include a shift position signal from a shift position switch 5 for detecting a shift position,
An oil temperature signal from an oil temperature sensor 10 for detecting the temperature of hydraulic oil, and an input shaft rotation sensor 11 for detecting a rotation speed of an input shaft
Input shaft rotation signal. Further, signals input to the main control unit 1 include a rotation speed signal from an engine rotation sensor (crank angle sensor) 13 for detecting a rotation speed of the engine 2 and a brake from a brake switch 14 for detecting an operation state of a brake. An operation signal is input.

On the other hand, a predetermined signal is output from the main control unit 1 to the first shift solenoid 6 and the second shift solenoid 7. Specifically, a shift control signal is output to each of the solenoids 6 and 7, whereby the shift solenoids 6 and 7 are output.
7, the frictional element of the automatic transmission 8 is selectively engaged to perform shift control. Here, at the time of the neutral control, the automatic transmission 8 is set to the second speed state in order to prevent backward running on an uphill road. The hydraulic pressure used for engaging the friction element is controlled by a so-called line pressure solenoid 9. Therefore, a line pressure control signal is output from the main control unit 1 to the line pressure solenoid 9. In an actual shift, a friction element is appropriately selected and controlled at each shift speed.

At the time of neutral control, the hydraulic pressure reduced in accordance with the line pressure is supplied to the low clutch, and the low pressure is controlled by the line pressure solenoid 9 so as to maintain the low clutch in a slipping state. Further, the main control unit 1 outputs a torque converter direct connection clutch control signal to the lock-up solenoid 12. As a result, the torque converter is directly connected at the third speed and the fourth speed. On the other hand, in the first and second speeds, the hydraulic pressure supplied to the low clutch among the friction elements is controlled so as to be switched between the normal line pressure and the reduced hydraulic pressure.

The ISC control means 1c in the main control unit 1
Outputs an ISC control signal to ISC 15. With this ISC control signal, the air flow rate during idling is controlled, and the engine speed during idling is maintained near the target value. An air conditioner control signal is output from the air conditioner control means 1d in the main control unit 1 to the air conditioner compressor 16. The air conditioner compressor 16 is turned on / off by the air conditioner control signal signal.

FIG. 1 shows a block diagram of a main part of the present invention. Here, the air conditioner control means controls on / off of the air conditioner compressor based on a plurality of input signals (not shown). Specifically, the signal input to the air conditioner control means 1d includes, for example, a vehicle interior temperature signal and a vehicle exterior temperature signal.

The ISC control means 1c outputs a predetermined ISC control signal to the ISC 15. Specifically, when the idle state and the vehicle stop are detected by the throttle opening sensor 3 and the vehicle speed sensor 4, feedback control is performed so that the engine rotation speed detected by the engine rotation sensor approaches the target value. And outputs an ISC control signal.

The target value of the engine speed is
Different values are set depending on whether the air conditioner compressor 16 is on or off. This is because the engine drive load fluctuates depending on whether the air conditioner compressor is on or off. At this time, the initial value of the feedback control is
It is determined in advance by learning control. That is, it is set by the shift position switch 14 and the neutral control means 1a corresponding to the neutral range, the travel range, and the time of the neutral control, and is determined based on a learning value of a certain idle air flow rate. The learning value of the air flow rate is updated as a new learning value when the state in which the engine rotation speed is near the target value has continued for a predetermined time or more.

When the vehicle is stopped, the bypass air flow rate is set to a relatively large value. When the idle state of the vehicle is detected, the bypass air flow rate is reduced so that the engine speed gradually decreases to the idle speed, and then the feedback control is started. It is supposed to be.

In the main control section 1, a neutral control permission means 1b is provided. The neutral control permission means 1b outputs a neutral control permission signal for permitting the start of the neutral control to the neutral control means 1a when the engine rotation speed becomes equal to or less than the target value. The target value of the engine speed is set to a different value depending on whether the air conditioner compressor 16 is turned on or off.

The neutral control means 1a performs the following control when the neutral control permission means 1c determines that the neutral control permission is given. That is, it is determined whether the neutral control start condition is satisfied based on information such as the throttle opening (engine load), the vehicle speed, the brake operation state, and the shift position. And
If the neutral control start condition is satisfied and a predetermined delay time elapses after the start condition is satisfied, the neutral control is started.

When the neutral control is started, the first shift solenoid 6 and the second shift solenoid
A signal for setting the shift stage to the second speed state is output to the shift solenoid 7. The lock-up solenoid 12
, A pressure reduction control signal for switching the hydraulic pressure supplied to the low clutch from the normal line pressure to the reduced hydraulic pressure is output. Further, the engine rotation speed (input shaft rotation speed of the torque converter) detected by the engine rotation sensor (crank angle sensor) 13 and the input shaft rotation speed (output of the torque converter) detected by the input shaft rotation sensor (turbine rotation sensor) 11. A difference between the rotational speed and the rotational speed is calculated, and a control signal is output from the neutral control means 1a to the line pressure solenoid 12 so that the rotational speed difference approaches a predetermined value.

FIGS. 3, 4 and 5 show control flowcharts of the present invention. These processes start at regular intervals,
Each process is switched back.

First, in step S100, information on the throttle opening (engine load) is fetched from the throttle opening signal of the throttle opening sensor 3. Step S101
Then, the vehicle speed is acquired from the vehicle speed sensor 4. Step S10
In step 2, information on the operation state of the brake is fetched from the brake switch 14. In step S103, shift position information is fetched from the shift position switch 5. Step S1
In 04, the engine rotation sensor (crank angle sensor) 15
The engine speed is taken in from. In step S105, the input shaft rotation speed is fetched from the input shaft rotation sensor (turbine rotation sensor) 11.

In step S106, air conditioner control is performed, and an air conditioner compressor control signal is output. In step S107, ISC control, that is, output of an ISC control signal and learning of an idle air flow rate are performed. Step S1
At 08, it is determined whether the neutral control is currently being performed. This is because the engine speed described below is one of the conditions for starting the neutral control. That is, since the determination is performed near the target value of the idling rotational speed, otherwise, there is a problem that the neutral control ends because the engine rotational speed fluctuates due to disturbance during the neutral control. .

If the neutral control is not being performed, it is determined in steps S109 to S111 that the neutral control is started based on the engine speed. If the neutral control is being performed, the process proceeds directly to step S112. In step S109, the air conditioner compressor 16 is turned on / off.
Off is determined, and if on, the process proceeds to step S110; if off, the process proceeds to step S111.

In step S110, it is determined whether or not the engine speed is less than NE1 which is set near the idle speed when the air conditioner compressor 16 is on. If the engine speed is lower than NE1, the process proceeds to step S112. If the engine speed is equal to or higher than NE1, the process proceeds to step S117. In step S111, it is determined whether or not the engine speed is less than NE2 which is set near the idle speed when the air conditioner compressor 16 is off. If the engine speed is less than NE2, the process proceeds to step S112, where N
If it is equal to or greater than E2, the process proceeds to step S117.

In steps S112 to S115, it is determined whether all the neutral control conditions are satisfied. When the engine 2 is idle, the vehicle is stopped, the brakes are applied, and the shift position is in the D range, it is determined that the neutral control start condition is satisfied,
Otherwise, it is determined that the condition is not satisfied. Here, the idle state is determined when the throttle opening (engine load) is equal to or less than a predetermined value near the fully closed state. In the vehicle stop state, it is determined that the vehicle is stopped when the vehicle speed is equal to or less than a predetermined value near 0 km / h.

If the neutral control start condition is satisfied, the process proceeds to step S116, in which the time during which the condition is satisfied, that is, the continuation time is counted, and the process proceeds to the next step. In other words, the continuation time can be said to be a delay time from when the neutral control start condition is satisfied to when the neutral control is actually started.

If the neutral control condition is not satisfied, the process proceeds to step S117, where the duration is reset and the process returns. In step S118, it is determined whether or not the duration exceeds a preset delay time. If the duration has exceeded, the process proceeds to step S119 to execute neutral control, and if not, the process returns.

In step S119, the first shift solenoid 6 is turned off, the second shift solenoid 7 is turned on, and the transmission gear mechanism is set to the second speed state. This prevents the output shaft from rotating in the reverse direction due to the action of the one-way clutch, and prevents the vehicle from moving backward on an uphill road even if the creep torque is reduced by the neutral control.

In step S120, a pressure reduction control signal having a duty ratio of 95% is output to the lock-up solenoid 12, and the hydraulic pressure supplied to the low clutch is switched from the normal line pressure to the reduced hydraulic pressure.

In steps S121 to S125, control of the line pressure solenoid is performed. First, in step S121, it is determined whether the difference between the engine rotation speed and the input shaft rotation speed of the transmission gear mechanism (input / output rotation speed difference of the torque converter) is greater than a target value or not. And
If the rotational speed difference is larger than the target value, the supply pressure to the low clutch is too high, and the process proceeds to step S122 to reduce the supply pressure to the low clutch, and the control value of the line pressure is decreased. On the other hand, if the rotational speed difference is smaller than the target value, the supply pressure to the low clutch is too low, and the process proceeds to step S123 to increase the supply pressure to the low clutch, and the control value of the line pressure is increased.

In this way, the line pressure is fed back so that the input / output rotational speed difference of the torque converter approaches the target value, and the low clutch is maintained in a sliding state. In step S124, the line pressure control value is converted into a control duty ratio according to the relationship shown in FIG. This is for the following reason. That is, as shown in FIG. 6, there is a region where the relationship between the line pressure and the control duty ratio is not completely linear but non-linear. For this reason, if the control duty ratio is directly fed back, the actual fluctuation of the line pressure with respect to the change in the duty ratio differs depending on the region. As a result, it is difficult to adjust the gain of the feedback control in all regions.

In step S125, a control signal is output to the line pressure solenoid according to the control duty ratio. When the neutral control is not performed, each control (shift, lock-up, line pressure, etc.) is performed according to other control (not shown).

Next, the operation will be described with reference to the time chart shown in FIG. Until time T5, the air conditioner compressor 16 is in the off state, and thereafter is in the on state. Note that this time chart is an example of a traveling state of a certain vehicle, and various situations other than this time chart can be considered in practice.

First, at time T0, the vehicle is in a running state in which the air conditioner compressor 16 is off. Thereafter, deceleration is started, and the vehicle is stopped at time T1. At this time, engine 2
Is in an idle state. However, the engine speed is higher than a predetermined value NE2 near the idle speed when the air conditioner compressor is off. Therefore, the condition for starting the neutral control has not been satisfied yet.

Thereafter, the engine speed gradually decreases and the time T
2, the condition for starting the neutral control is satisfied.
Therefore, the counting of the duration time is started. And
Neutral control is started at time T3 when the duration has exceeded the predetermined value. At time T4 during the neutral control,
The air conditioner compressor 16 is turned on, and the ISC control is performed so as to increase the engine speed. At time T5, the brake is released and the accelerator is depressed, the neutral control ends, and then the vehicle enters the running state.

At time T6, the vehicle stops again and becomes idle, but the engine speed is higher than the value NE1 near the idle speed when the air conditioner compressor is on. Therefore, the condition for starting the neutral control has not been satisfied yet. Thereafter, the condition that the engine speed gradually decreases and the neutral control is started at time T7 is satisfied. And
The counting of the duration is started. Then, the neutral control is restarted at time T8 when the duration has exceeded the predetermined value.

In the above embodiment, the condition of the neutral control has been described by taking an air conditioner compressor, which is one of the accessories, as an example. However, the same control can be applied to other auxiliary machines. For example, an electric load (alternator), a power steering pump, or the like can be considered. Instead of setting the engine speeds (NE1 and NE2) for the neutral control start determination, a value obtained by adding a predetermined value to the target rotation speed during idling is used as the initial value of the engine speed for the control start determination. It may be.

[0046]

As described above, the engine speed is used as the condition for starting the neutral control. Therefore, when the vehicle shifts from the idle state in the running state to the idle state in the vehicle stopped state, the neutral control is started after the engine rotation speed becomes close to the idle rotation speed. For this reason, it is possible to prevent a large fluctuation of the engine rotation speed from occurring.

Further, even when the idle speed is set to a high value while driving an auxiliary machine such as an air conditioner compressor, the engine speed at which the neutral control is permitted to start can be set separately. The optimal value can be set in such a case.

[Brief description of the drawings]

FIG. 1 shows a block diagram of a neutral control means of the present invention.

FIG. 2 shows a schematic diagram of a system including a neutral control device of the present invention.

FIG. 3 shows a flowchart of a part of a neutral control start determination in the present invention.

FIG. 4 shows a flowchart of a part of a neutral control start determination according to the present invention.

FIG. 5 shows a flowchart of line pressure control in the present invention.

FIG. 6 is a diagram illustrating a relationship between a duty ratio signal to a line pressure solenoid and a line pressure.

7 is a diagram showing a time chart relating to an example of the neutral control of the present invention. FIG. 7 (A) shows a change in throttle opening (corresponding to engine load), and FIG. 7 (B) shows a change in vehicle speed. 7 (C) shows a change in engine rotation speed, FIG. 7 (D) shows a change in brake operation, FIG. 7 (E) shows a change in shift position, and FIG. 7 (F) shows an air conditioner compressor. FIG.
FIG. 7G shows a change in the duration of the neutral control start condition, and FIG. 7H shows a change in the control and non-control of the neutral control.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main control part 1a Neutral control means 1b Neutral control permission means 1c ISC control means 1d Air conditioner control means 2 Engine 3 Throttle opening sensor 4 Vehicle speed sensor 5 Shift position switch 8 Automatic transmission 15 ISC 16 Air conditioner compressor

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) FB01 FB02 FB04 3J052 AA14 CA31 CB06 EA02 EA04 EA06 GB01 GC13 GC23 GC44 GC46 GC64 GC73 KA01 LA01

Claims (3)

[Claims] 1. A neutral control device for an automatic transmission, comprising: an automatic transmission that transmits a driving force from an engine to driving wheels; and a main control unit that controls operations of the engine and the automatic transmission. A control unit configured to neutralize the automatic transmission under a predetermined condition under neutral conditions, and an ISC control unit that controls an idle rotation speed of the engine to a predetermined target value by adjusting an air flow rate. Neutral control permitting means for permitting the neutral control means to start neutral control in accordance with the rotational speed of the engine, wherein the neutral control permitting means is configured to determine whether the rotational speed of the engine is close to the target value. A neutral speed control function for permitting the neutral control when the value becomes equal to or less than a value. The control device. 2. The neutral control device according to claim 1, wherein the neutral control permitting means has different target values of the rotational speed depending on whether or not a load is applied to the engine by a predetermined auxiliary device. . 3. The apparatus according to claim 2, wherein the auxiliary device is an air conditioner, an alternator, or a power steering pump.
A neutral control device for an automatic transmission according to the above.