Method for controlling electric oil pump

Abstract

The present disclosure provides a method for controlling the electric oil pump for a vehicle having an idle stop and go system. The system includes a control device for controlling the operation of the electric oil pump when the vehicle is stopped and restarted again. In the system, the operation of the electric oil pump is performed by an actual RPM control applying a target RPM of the electric oil pump and a torque or a current value of the electric oil pump.

Claims

1. A method for controlling an electric oil pump for a vehicle by using a control device in the electric oil pump for the vehicle having an engine, the method for controlling the electric oil pump comprising steps of: (A) determining whether the vehicle is stopped; (B) deciding a target RPM of the electric oil pump; (C) controlling an actual RPM at which the electric oil pump is actually driven based on the target RPM; (D) controlling the actual RPM based on a torque or a current value of the electric oil pump; and (E) stopping the electric oil pump based on the target RPM; wherein the step (D) comprises a step of determining whether the torque or the current value is reduced when a difference between the target RPM and the actual RPM is equal to or smaller than a predetermined error value.

2. The method for controlling the electric oil pump of claim 1, further comprising step of determining whether a RPM of the engine is equal to or smaller than a predetermined reference stop value when the vehicle has been stopped, wherein the step (B) determines the target RPM of the electric oil pump when the RPM of the engine is equal to or smaller than the reference stop value.

3. The method for controlling the electric oil pump of claim 1, wherein the step (C) comprises a step of maintaining the actual RPM at a maximum value of a reference RPM range when the target RPM is equal to or greater than a minimum value of the predetermined reference RPM range.

4. The method for controlling the electric oil pump of claim 3, wherein the step (C) further comprises a step of maintaining the actual RPM at the target RPM after a predetermined reference time has elapsed.

5. The method for controlling the electric oil pump of claim 1, wherein the step (D) further comprises steps of: determining whether the torque or the current value is reduced to a value smaller than a predetermined reference input/output value when the torque or the current value reduces; and increasing the actual RPM in proportion to the reducing level in the torque or the current value when the torque or the current value reduces to a value smaller than the reference input/output value.

6. The method for controlling the electric oil pump of claim 5, wherein the step (D) further comprises a step of determining whether the target RPM is smaller than a minimum value of a predetermined reference RPM range, and wherein the step (E) comprises a step of stopping a driving of the electric oil pump when the target RPM is smaller than the minimum value of the reference RPM range.

7. The method for controlling the electric oil pump of claim 1, wherein the target RPM of the electric oil pump is decided in an inverse proportion to a temperature of an oil sucked by the electric oil pump.

Description

DRAWINGS

(1) In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

(2) FIG. 1 is a diagram illustrating that a transmission supply pressure reduction phenomenon of the oil occurs by controlling an electric oil pump according to the conventional method in an idle stop and go provided with a mechanical oil pump and an electric oil pump;

(3) FIG. 2 is a block diagram of an idle stop and go with a mechanical oil pump and an electric oil pump including a control device for controlling the electric oil pump according to a form of the present disclosure;

(4) FIGS. 3 and 4 are flowcharts illustrating a method for controlling the electric oil pump according to the form of the present disclosure; and

(5) FIG. 5 is a diagram illustrating that the transmission supply pressure reduction phenomenon of the oil is avoided by controlling the electric oil pump according to the form of the present disclosure.

(6) The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

(7) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

(8) Referring to FIG. 2, an idle stop and go 10 includes a Mechanical Oil Pump (MOP) 2 connected to an engine 1 and driven by the power of the engine, and an Electric Oil Pump (EOP) 3 driven by electric power through a control device 3-1 separated from the engine 1, and each of the oil pumps independently supplies oil to a transmission 4, respectively.

(9) When a vehicle is stopped, the mechanical oil pump 2 is stopped because the engine 1 is stopped, and the electric oil pump 3 is operated to supply the oil to the transmission 4 instead of the mechanical oil pump 2. On the contrary, when the vehicle starts again, the electric oil pump 3 is stopped, and the engine 1 and the mechanical oil pump 2 connected to the engine 1 are operated again to supply the oil to the transmission 4.

(10) Meanwhile, the electric oil pump 3 is operated based on a target RPM value calculated based on the shift state of the vehicle received from a Transmission Control Unit (TCU). Since the discharge pressure of the mechanical oil pump 2 driven by the power of the engine 1 is generally higher than the discharge pressure of the electric oil pump 3 driven by the rotation of a motor, the oil pressure supplied to the transmission 4 is reduced (e.g., the oil pressure at the point X in FIG. 2) when it is switched from the mechanical oil pump 2 to the electric oil pump 3.

(11) According to a form of the present disclosure, the idle stop and go 10 implements the control of the electric oil pump 3 as shown in FIGS. 3 and 4 through a control device 3-1 for controlling the phenomenon such as a1, a2, a3 and a4 as shown in FIG. 1 in a conventional electric oil pump.

(12) The method for controlling the electric oil pump 3 as shown in FIGS. 3 and 4 is characterized that the actual RPM control is applied to the method for controlling the electric oil pump 3 for the vehicle by using the control device 3-1 of the electric oil pump 3, and the actual RPM control is characterized that the actual RPM control applying the target RPM of the electric oil pump 3 and the torque or the current value of the electric oil pump 3 is applied to the operation of the electric oil pump 3.

(13) Accordingly, as described above, the actual RPM control is implemented in the order of controlling the actual RPM based on the target RPM, and then controlling the actual RPM based on the torque or the current value.

(14) In addition, the actual RPM control implements the stop of the electric oil pump based on the target RPM.

(15) Hereinafter, as shown in FIGS. 3 and 4, the control process for operating the electric oil pump 3 according to a form of the present disclosure is specifically as follows. In this case, for example, it is described that the actual RPM control is divided into individual steps.

(16) First, the control device 3-1 of the electric oil pump 3 for the vehicle first detects the vehicle speed S110, and determines whether the vehicle is stopped S120.

(17) Then, the control device 3-1 detects the RPM of the engine 1 or the mechanical oil pump (MOP) 2 S130 when it is determined that the vehicle has been stopped, and determines whether the RPM of the engine 1 or the mechanical oil pump 2 is equal to or smaller than a predetermined reference stop value S140.

(18) At this time, the reference stop value corresponds to a reference RPM value of the engine 1 capable of determining that the engine has been stopped in the idle stop and go 10, and when the RPM of the engine 1 is equal to or smaller than the reference stop value, the control device 3-1 determines that the engine 1 has been stopped. For example, the reference RPM value of the engine 1 may apply about 500 RPM or less as an idle Revolution Per Minute (RPM).

(19) Then, the control device 3-1 determines the target RPM of the electric oil pump 3 S150. Herein, the target RPM may be decided in inverse proportion to the temperature of the oil sucked from an oil tank 6 by the electric oil pump 3, and the temperature of the oil sucked from the oil tank 6 may be confirmed by the detected value of a temperature sensor installed in the oil tank 6.

(20) The reason for this is that the oil sucked by the electric oil pump 3 is supplied to the portion with which the mechanical devices of the transmission 4 are engaged to be used to lubricate and cool the corresponding portion. Therefore, the higher the temperature of the oil sucked by the electric oil pump 3, the smaller the amount of oil supplied to the transmission 4, such that the target RPM is decided by being inversely proportional to the temperature of the oil sucked by the electric oil pump 3. At this time, the control device 3-1 may calculate the RPM value corresponding to the temperature of the sucked oil based on the previously stored reference table, and determine it as the target RPM.

(21) After determining the target RPM, the control device 3-1 determines whether the target RPM is equal to or greater than a minimum value of the predetermined reference RPM range S160.

(22) In this case, the reference RPM range indicates a range of the RPM value at which the electric oil pump 3 is driven, and the minimum value of the reference RPM range is a minimum RPM value for driving the electric oil pump 3.

(23) Then, the control device 3-1 maintains the actual RPM at which the electric oil pump 3 is actually driven at the maximum value of the reference RPM range when the target RPM is equal to or greater than the minimum value of the reference RPM range S170.

(24) The reason for this is that when the actual RPM at which the electric oil pump 3 is actually driven is maintained at the maximum value of the reference RPM range as indicated by as the b1 in FIG. 5, it is possible to inhibit the pressure of the oil supplied to the transmission 4 (the pressure at the point X in FIG. 1) as indicated by the b2 in FIG. 5 from being sharply reduced, thereby stably supplying the oil to the transmission 4 while the engine 1 is stopped.

(25) In particular, the control device 3-1 maintains the actual RPM at the maximum value of the reference RPM range during a predetermined reference time. At this time, the reference time is a time until when the operation of the mechanical oil pump 2 is fully stopped, the electric oil pump 3 is fully driven, and the pressure of the oil supplied to the transmission 4 is stabilized. For example, the full-stop of the mechanical oil pump 2 may be set as a state where the rotation does not occur due to rotational inertia, the full drive of the electric oil pump 3 may be set as a state where the pumped and discharged pressure reaches a predetermined oil pressure, and the stabilizing the pressure of the oil supplied to the transmission 4 may be applied as a state where the oil flow rate is supplied without the pulsation phenomenon or the swirl of the supply oil.

(26) Subsequently, after the reference time has elapsed, the control device 3-1 reduces the actual RPM by the target RPM so that the actual RPM is maintained at the target RPM originally targeted S180. At this time, the control device 3-1 determines whether the difference between the target RPM and the actual RPM is equal to or smaller than a predetermined reference error value S190. In this case, the reference error value means a minimum error value capable of determining that the actual RPM has reached the target RPM.

(27) Therefore, when the difference between the target RPM and the actual RPM is determined S190, if the difference between the target RPM and the actual RPM exceeds the reference error value, it is determined that the actual RPM has not reached the target RPM and the control device 3-1 continuously reduces the actual RPM value.

(28) On the other hand, when the difference between the target RPM and the actual RPM is determined S190, if the difference between the target RPM and the actual RPM is equal to or smaller than the reference error value, the control device 3-1 determines whether the torque or the current value of the electric oil pump 3 is reduced S210. Herein, the torque of the electric oil pump 3 means a torque of the motor of the electric oil pump 3 or a rotor coupled to the motor, and the current of the electric oil pump 3 means a current applied to the motor of the electric oil pump 3.

(29) Then, in the determining whether the torque or the current value of the electric oil pump 3 reduces S210, when the torque or the current value reduces, the control device 3-1 determines whether the torque or the current value is reduced to a value smaller than a predetermined reference input/output value S211. Herein, the reference input/output value means the allowable minimum value of the torque or the current value, and when the torque or the current value is reduced to a value smaller than the reference input/output value, the control device 3-1 determines that the pressure of the oil supplied to the transmission 4 is below the standard.

(30) Therefore, the control device 3-1 increases the actual RPM in proportion to the reducing level in the torque current value S212 as indicated by the b3 in FIG. 5. Then, as indicated by the b4 in FIG. 5, it is possible to inhibit the pressure of the oil supplied to the transmission 4 from being sharply reduced as the gear is shifted.

(31) Thereafter, the control device 3-1 determines whether the target RPM is smaller than the minimum value of the reference RPM range S220. Then, when the target RPM is smaller than the minimum value of the reference RPM range, it is determined that the driver starts the vehicle so that the idle stop and go system 10 stops the driving of the electric oil pump 3 and starts the mechanical oil pump 2 S230.

(32) As described above, according to the method for controlling the electric oil pump in the present disclosure, it is possible to maintain the actual RPM of the electric oil pump 3 at the maximum value of the reference RPM range, and then to maintain it at the target RPM, thereby inhibiting the pressure of the oil supplied to the transmission 4 from being sharply reduced when it is switched from the mechanical oil pump 2 to the electric oil pump 3. In addition, according to the method for controlling the electric oil pump in the present disclosure, when the torque or the current value of the electric oil pump 3 is reduced, it is possible to increase the actual RPM in proportion thereto, thereby inhibiting the pressure of the oil supplied to the transmission 4 from being sharply reduced upon gear shift.

(33) While this present disclosure has been described in connection with what is presently considered to be practical exemplary forms, it is to be understood that the present disclosure is not limited to the disclosed form, but, on the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the present disclosure.