SYSTEM FOR CONTROLLING ENGINE TORQUE WHEN SHIFTING FROM
IDLE STATE
FIELD OF THE INVENTION
The present invention relates to an engine control system. More particularly, the present invention relates to a system for controlling engine torque when shifting from an idle state in an automatic transmission, in which engine torque control is performed to prevent shift shock.
BACKGROUND OF THE INVENTION
In an automatic transmission for a vehicle, when a desired shift range (for example, one of P.R.N.D.2,L ranges) is selected by driver manipulation of a shift lever, a manual valve undergoes port conversion such that hydraulic pressure generated by operation of a hydraulic pump forms line pressure through specific lines. As a result, shifting into the desired range is effected.
If shifting is performed into a range that has more than one speed (e.g., D and 2) and if driving conditions are changed as a result of variations in the driving speed, throttle opening, etc., a shift control system performs duty control of the hydraulic pressure through a plurality of solenoid valves to operate various operational elements of a gearshift mechanism. As a result, shifting is automatically controlled into a suitable speed, providing convenience to the driver.
In conventional schemes for controlling shifting in automatic transmissions, when shifting is initiated into a desired range using the shift lever, that is, shifting such as N, D, N, R, D, R, R, D, D, N, and R, N shifting,

if engine torque is altered, hydraulic pressure is controlled a second time (following the initial shifting into the desired range) by operation of the solenoid valves such that shift feel is maintained.
However, there are limitations to the amount of flexibility in control provided with such a conventional shift control scheme. As a result, the degree to which shift feel can be improved is restricted.
Further, if the accelerator pedal is operated before shifting into a desired range is completed (following driver manipulation of the shift lever), engine torque is abruptly increased. In such an instance, an attempt is made to quickly engage the required elements using line pressure and duty pressure that is substantially increased. However, if the accelerator pedal is depressed by a significant amount such that a correspondingly large throttle opening is effected, a substantial shift shock occurs. This decreases shift feel and may also damage clutches in the transmission.
SUMMARY OF THE INVENTION
The present invention provides a system for controlling engine torque when shifting from an idle state in an automatic transmission, in which an engine torque control time and engine torque levels for each shift range are used to construct a map table of engine torque and throttle opening, and engine torque is stably controlled on the basis of the map table when shifting is initiated by operation of the shift lever from an idle state such that the level of flexibility in shift control is enhanced and the generation of shift shock is prevented to improve shift feel.

In a preferred embodiment, the system of the present invention includes a shift range detector detecting a shift range selected by a shift lever; a throttle opening detector detecting an opening degree of a throttle valve; an engine speed detector detecting an engine speed; a vehicle speed detector detecting a speed at which a vehicle is traveling; an actuator controlling a hydraulic pressure in a transmission to realize shifting into a specific shift range; an engine control unit controlling an engine torque; and a transmission control unit controlling an operation of the actuator based on signals received from the detectors, and outputting an engine torque control signal to the engine control unit. If idle conditions are satisfied and a change in a shift range by the shift lever is detected, the transmission control unit calculates, after a throttle opening and an engine speed are detected, an engine torque control value corresponding to the throttle opening and the engine speed from a map table established with respect to the change in the shift range, then the transmission control unit outputs the engine torque control signal to the engine control unit.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention:
FIG. 1 is a block diagram of an engine torque control system according to a preferred embodiment of the present invention; and
FIG. 2 is a flow chart of an engine torque control process used in the system of FIG. 1 according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
With reference to FIG. 1, an engine torque control system according to a preferred embodiment of the present invention includes an inhibitor switch 10, a throttle opening detector 20, an engine speed detector 30, a vehicle speed detector 40, a transmission control unit (TCU) 50, an engine control unit (ECU) 60, and an actuator 70.
The inhibitor switch 10 detects a position of a shift lever in a specific range and outputs a corresponding signal. The throttle opening detector 20 detects changes in an opening of a throttle valve, which is linked to an accelerator pedal, and outputs a corresponding signal. The engine speed detector 30 detects an engine speed through calculations of a rotational speed of a crankshaft, and outputs a corresponding signal. The vehicle speed detector 40 detects a present vehicle speed through calculations of a speed of a transfer driven gear, and outputs a corresponding signal.
The TCU 50 constructs and stores a map table using an engine torque control time and engine torque levels at each shift range according to an engine speed and a throttle valve opening for each shift range. Also, if a change in the range position of the shift lever is detected, the TCU 50 calculates line pressures and duty pressures for performing shifting into the selected target range. Finally, the TCU 50 calculates an engine torque control value from the constructed map table, then performs engine torque control

through the ECU 60. Based on an engine torque control signal received from the TCU 50, the ECU 60 calculates an amount of fuel required for injection into a combustion chamber, and required ignition timing, then performs fuel injection and ignition using the calculated values to control engine torque. The TCU 50 and the ECU 60 may be realized through microprocessors that operate using programs for performing the functions as described above.
The actuator 70 regulates the supply of hydraulic pressure in a transmission to enable shifting into the shift range selected by the shift lever. The actuator 70 performs this function using a line pressure control signal and a duty pressure control signal received from the TCU 50. The actuator 70 may be configured in a variety of different ways depending on transmission type. Since such different configurations are well know to those skilled in the art, a detailed description will not be provided.
An engine torque control process according to a preferred embodiment of the present invention will now be described. The process is applied to the engine torque control system described above.
In a state where the engine is started, the TCU 50 reads vehicle state information in step S101. The vehicle state information includes shift lever position information, throttle opening information, engine speed information, and vehicle speed information. Next, it is determined by the TCU 50 if the vehicle speed is zero, and if the throttle valve opening and the engine speed satisfy engine idle conditions, that is, if the throttle valve opening and engine speed are within predetermined ranges, in step S102.

If the vehicle speed is zero and the idle conditions are satisfied, the signal of the inhibitor switch 10 is detected in step S103 to determine if there has been a change in the shift range by the shift lever in step S104. In step S104, if there has been no change in the shift range by operation of the shift lever, a present control state is maintained.
However, in step S104, if it is determined that the shift range has been changed by shift lever operation, for example, if it is determined that the shift lever has been re-positioned from one range into another range such as N, D, N, R, D, R, R, D, D' N, or R, N, the TCU 50 determines a line pressure and a duty pressure resulting from port conversion of a manual valve and performs shifting into the selected range through the actuator 70. In addition to such normal operation, the TCU 50 also detects changes in the throttle opening and engine speed in step S105, and calculates an engine torque control value with respect to the detected range from the established map table in step S106.
Next, the TCU 50 outputs an engine torque control signal based on the engine torque control value to the ECU 60 using CAN (Computer Area Network) communications, then after the ECU 60 calculates a fuel injection quantity and ignition timing using the calculated control value, the ECU 60 increases or decreases engine torque using the calculated fuel injection quantity and ignition timing in step S107.
Although the TCU 50 may output the engine torque control signal as soon as a change in the position of the shift lever is detected, it is preferable that the engine torque control signal is output by the TCU 50 after a

predetermined time has elapsed after such a detection is made.
Since the manner in which engine torque is increased and decreased to a predetermined level by varying fuel injection amounts and varying ignition timing are well known to those skilled in the art, a detailed description thereof will not be provided.
Subsequently, it is determined if a duration during which engine torque is increased or decreased has surpassed a predetermined time in step S108. If the predetermined time has elapsed, it is determined that shifting into the shift range selected by the shift lever is completed in step S109. Engine torque control is then discontinued in step S110.
The determination of whether shifting into the selected range is completed need not necessarily be performed by checking whether a predetermined time has elapsed (since engine torque control is started) as described above. For example, this may be performed by calculating a turbine speed at the end of synchronization, and determining if a present turbine speed falls within a predetermined speed range, which includes the calculated turbine speed when synchronization is completed. If such a determination is made, it is determined that shifting into the selected shift range is completed.
In the present invention structured and operating as in the above, a map table is constructed at each shift range for engine torque control with respect to a selected shift range, an engine speed, and throttle opening. If it is determined that the shift lever has been re-positioned into another range from an idle state, control is performed to minimize variations in engine torque using

an engine torque control value of the map table. As a result, the flexibility in the amount of control is increased and shift feel is improved in a simple manner. In addition, shift shock and the damage to clutches resulting from the occurrence of shift shock are prevented.
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.

We Claim:
1. A system for controlling engine torque when shifting, comprising:
a shift range detector detecting a shift range selected by a shift lever;
a throttle opening detector (20) detecting an opening degree of a throttle valve;
an engine speed detector (30) detecting an engine speed;
a vehicle speed detector (40) detecting a speed at which a vehicle is traveling;
an actuator (70) controlling a hydraulic pressure in a transmission to realize shifting into a specific shift range;
an engine control unit (60) controlling an engine torque; and
a transmission control unit (50) controlling an operation of the actuator based on signals received from the detectors, and outputting an engine torque control signal to the engine control unit;
wherein if idle conditions are satisfied and a change in a shift range by the shift lever is detected, the transmission control unit calculates, after a throttle opening and an engine speed are detected, an engine torque control value corresponding to the throttle opening and the engine speed from a map table established with respect to the change in the shift range, then transmission control unit outputs the engine torque control signal to the engine control unit.
2. The system as claimed in claim 1, wherein the engine control unit controls engine torque by regulating fuel injection and ignition timing based on the engine torque control signal received from the transmission control unit.
3. The system as claimed in claim 1, wherein the map table is established based on a throttle opening and an engine speed with respect to each shift range change by the shift lever.

4. The system as claimed in claim 1, wherein the idle conditions include a vehicle speed of zero, and a throttle opening and an engine speed of an idle range.
5. The system as claimed in claim 2, wherein the engine control unit controls engine torque until a turbine speed reaches a predetermined speed range that includes a target turbine speed.
6. A system for controlling engine torque when shifting substantially as herein described with reference to the accompanying drawings.