Method and device for controlling load of generator

Abstract

To suppress a fluctuation in the idle speed of an internal combustion engine caused by a transient increase in a generated current that occurs when the control mode is switched.SOLUTION: When an internal combustion engine is idling, the generator control mode is field current limit control, and by reducing a field current command value C1, the generator torque corresponds to the allowable torque. When there is a voltage request at a time t1 due to a drop in the battery SOC, for example, a voltage command value C2 gradually changes to the target value for voltage limit control while the field current command value C1 is held at the value at the time t1. When the voltage command value C2 reaches the target value (time t2), the field current command value C1 starts to be changed. Between the times t1 and t2, the generated current is limited by the field current command value C1, such that there is no transient increase in the generator torque.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method and device for load control of a generator driven by the power of an internal combustion engine, and more particularly to control during switching between two control modes, namely, field current limit control and voltage limit control. [Background technology]

[0002] Patent Document 1 describes that the control modes of a generator (so-called alternator) provided as an auxiliary device in a vehicle internal combustion engine include a voltage control mode in which the output voltage of the generator is controlled to a command voltage, and a current control mode in which the output current of the generator is controlled to a command current, and that the current control mode is used when the rotation speed of the internal combustion engine is low, and the voltage control mode is used when the vehicle decelerates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-74815 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when switching from the current control mode to the voltage control mode, the value of the command current changes from the value in the current control mode to the value in the voltage control mode, and at the same time, the value of the command voltage changes from the value in the current control mode to the value in the voltage control mode, thereby switching the control mode. During this switching transition, the amount of change in the generator output current accompanying the change in the command current value is not necessarily equal to the amount of change in the generator output current accompanying the change in the command voltage value. Therefore, a temporary increase in the generator output current, that is, a temporary increase in the generator torque (torque required to drive the generator), may occur. For example, if the target rotation speed of the internal combustion engine is constant, such as during idling operation of the internal combustion engine, a fluctuation (temporary drop) in the rotation speed occurs due to the temporary increase in the generator torque. The same applies when switching from the voltage control mode to the current control mode. [Means for solving the problem]

[0005] The present invention relates to a load control method for a generator driven by the power of an internal combustion engine, which has, as control modes, a field current limiting control for limiting a field current in accordance with a field current command value and a voltage limiting control for limiting a voltage in accordance with a voltage command value, and switches between the two control modes according to requirements, comprising the steps of: When switching from field current limit control to voltage limit control, the field current command value is held at the value immediately before the switchover while the voltage command value is gradually changed to the target value in the voltage limit control, and when the target value is reached, change of the field current command value begins.

[0006] In another aspect of the invention, When switching from voltage limiting control to field current limiting control, the voltage command value is held at the value immediately before the switchover while the field current command value is gradually changed to the target value in the field current limiting control, and when the target value is reached, change of the voltage command value begins. Effect of the Invention

[0007] According to this invention, when switching from field current limiting control to voltage limiting control, or conversely, when switching from voltage limiting control to field current limiting control, it is possible to suppress fluctuations in output current and therefore fluctuations in internal combustion engine speed caused by simultaneous changes in both the field current command value and the voltage command value. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an embodiment of the present invention. [Diagram 2] 5 is a flowchart showing a process flow when switching a control mode. [Diagram 3] 5 is a time chart showing an operation when switching from field current limit control to voltage limit control. [Figure 4] 5 is a time chart showing an operation when switching from voltage limit control to field current limit control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the configuration of a power generating device according to an embodiment in which a generator 2 is driven by the power of an internal combustion engine 1 that serves as a driving source for a vehicle. The internal combustion engine 1 is, for example, a spark ignition type internal combustion engine, a so-called gasoline engine, and may be a diesel engine that performs compression ignition. The generator 2 is a three-phase AC generator, a so-called alternator, and is driven by the crankshaft of the internal combustion engine 1 via, for example, a belt transmission mechanism 3. The electric power generated by the generator 2 is supplied to an electric load such as a battery 4 and various electric components (not shown). The battery 4 is, for example, a general lead-acid battery with a nominal voltage of 12V. The output current of the generator 2 is the sum of the current flowing through the electric load and the charging and discharging current of the battery 4.

[0010] The generator 2 is integrally equipped with a regulator 5 that adjusts the output voltage to a constant value by controlling the field current. A field current command value C1 and a voltage command value C2 are provided to the regulator 5 from a controller 6, and the regulator 5 controls the field current based on these command values ​​C1 and C2. In detail, the field current is controlled according to the command value that relatively reduces the output current (driving torque) between the output current (driving torque) corresponding to the field current command value C1 and the output current (driving torque) corresponding to the voltage command value C2.

[0011] Therefore, if the field current command value C1 given from the controller 6 to the regulator 5 is relatively small and the voltage command value C2 is sufficiently high (e.g., the maximum value without any restriction), the control mode becomes field current limiting control, and the field current is limited according to the field current command value C1. On the other hand, if the field current command value C1 given from the controller 6 to the regulator 5 is sufficiently large (e.g., the maximum value without any restriction) and the voltage command value C2 is relatively low, the control mode becomes voltage limiting control, and the field current is controlled so as to limit the voltage to the voltage command value. In other words, the controller 6 determines whether the control mode is to be field current limiting control or voltage limiting control in response to a request, and changes the two command values ​​C1 and C2 given to the regulator 5, thereby substantially switching the control mode.

[0012] The controller 6 is connected to an engine controller (not shown) via an in-vehicle network (so-called CAN), and switches the control mode in response to a request from the engine controller, a request based on the battery voltage, etc. The controller 6 may be configured as a part of the functions of the engine controller.

[0013] In one embodiment, while the vehicle is traveling, power generation is basically performed by voltage limit control, that is, the output voltage of the generator 2 is adjusted to a target constant voltage.

[0014] On the other hand, during idling of the internal combustion engine 1, field current limiting control is performed preferentially in order to stably maintain a relatively low idle rotation speed. Then, if there is a voltage request due to, for example, a drop in the SOC of the battery 4 while the field current limiting control is being performed, the control is switched from the field current limiting control to the voltage limiting control.

[0015] 3 shows an operation when the internal combustion engine 1 is idling, field current limit control is performed initially, and then the control mode is switched from field current limit control to voltage limit control at time t1. From the top, (a) current limit prohibition request flag, (b) voltage command value C2, (c) field current command value C1, (d) power generation current (output current), and (e) rotation speed of the internal combustion engine 1 are shown.

[0016] The current limit prohibition request flag indicates that the field current limit control is prohibited when it is on and that the field current limit control is permitted when it is off, and indicates a control mode switching request from an engine controller, etc. Therefore, the current limit prohibition request flag is off until time t1, and turns on at time t1.

[0017] In the field current limit control up to time t1, the voltage command value C2 is the maximum value (e.g., 14 V) at which no limit is imposed. Note that this is merely a "command value," and the actual output voltage is at a lower level (e.g., less than 13 V). Essentially, the actual output voltage is relatively low in the field current limit control, and relatively high in the voltage limit control.

[0018] In the field current limit control up to time t1, the field current command value C1 is controlled to a relatively small limit value according to the allowable torque allowed for driving the generator 2. The allowable torque corresponds to the torque generated by the internal combustion engine 1 during idling minus the torque of the auxiliary devices such as the compressor for the air conditioner and the torque absorbed by the transmission side, in other words, it is a torque value that is allowed so as not to cause a drop in the idle speed. Under the field current limit control, the actual field current is basically obtained according to the field current command value C1. As a result of the field current being limited by the relatively small field current command value C1 in this way, the generated current shown in (d) is at a relatively low level. Note that the allowable torque repeatedly fluctuates within a relatively narrow range, and therefore the field current command value C1 also fluctuates slightly, but for the sake of explanation, it is drawn as a simple straight line in the figure.

[0019] When the field current limit control is prohibited at time t1, the control shifts to voltage limit control, and the voltage command value C2 gradually decreases toward a predetermined target value in the voltage limit control. The target value in the voltage limit control is a level at which the battery 4 can be charged or the SOC can be maintained, for example, around 13 V. Here, the controller 6 decreases the voltage command value C2 at a predetermined rate of change so that the torque of the generator 2 does not change suddenly. At time t2, the voltage command value C2 reaches the target value.

[0020] On the other hand, the field current command value C1 is maintained at the value immediately before the control mode is switched, that is, the value at time t1, until the voltage command value C2 reaches the target value in the voltage limit control. When the voltage command value C2 reaches the target value at time t2, the limit value in the field current limit control starts to be changed to the maximum value without any limit. In other words, the field current command value C1 gradually increases at a predetermined rate of change so that the torque of the generator 2 does not change suddenly, and reaches the maximum value without any limit at time t3. Note that the field current command value C1 is merely a command value given by the controller 6 to the regulator 5, and the actual field current after time t3 is adjusted by the regulator 5 to realize the voltage command value C2.

[0021] Between times t1 and t2, the actual field current continues to be limited by the relatively small field current command value C1 at time t1, so the generated current is not affected by changes in the voltage command value C2. Then, between times t2 and t3, the generated current gradually increases as the field current command value C1 gradually increases, and finally changes smoothly to the value of the generated current under voltage limit control.

[0022] Therefore, as shown in (e), the rotation speed of the internal combustion engine 1, that is, the idle rotation speed, does not fluctuate.

[0023] If the change (decrease) of the voltage command value C2 and the change (increase) of the field current command value C1 are started simultaneously at time t1, the limitation of the generated current by the voltage command value C2 cannot be kept up, and the generated current will increase excessively once and then decrease to the final level under voltage limit control. In this case, the torque of the generator 2 may temporarily exceed the allowable torque, causing the idle speed to fluctuate.

[0024] In the above embodiment, the torque fluctuation of the generator 2, and therefore the fluctuation of the rotation speed of the internal combustion engine 1, can be reliably suppressed when the control mode is switched.

[0025] Next, the time chart of Fig. 4 shows the operation when the control temporarily shifts from the voltage limit control to the field current limit control at time t11 during the idling operation of the internal combustion engine 1. For example, after the control is switched to the voltage limit control as shown in Fig. 3 due to a drop in the SOC of the battery 4, the control is switched to the field current limit control when the SOC of the battery 4 recovers to a predetermined level. In this case, the same switching control as the control mode switching in Fig. 3 is performed.

[0026] In the voltage limiting control up to time t11, the voltage command value C2 is at a predetermined target value (for example, 13 V), and the field current command value C1 is at a maximum value for which no limit is imposed.

[0027] When a command is issued to switch from voltage limit control to field current limit control at time t11, the field current command value C1 starts to change to the limit value at a predetermined rate of change. That is, the field current command value C1 gradually decreases at a predetermined rate of change so as not to cause a sudden change in the torque of the generator 2, and at time t12, it reaches a relatively small limit value according to the allowable torque.

[0028] The voltage command value C2 maintains the value immediately before the control mode is switched, that is, the value at time t11, until the field current command value C1 reaches the target limit value. When the field current command value C1 reaches the target limit value at time t12, the voltage command value C2 starts to be changed from the target value in the voltage limit control to the maximum value without imposing any limit.

[0029] Between times t11 and t12, the actual field current is adjusted according to the voltage command value C2 at time t11, and when the field current command value C1 becomes smaller than the actual field current, the generated current gradually decreases accordingly, and finally changes smoothly to the value of the generated current under field current limit control. Then, between times t12 and t13, the actual field current continues to be limited by the relatively small field current command value C1 at time t12, so it is not affected by changes in the voltage command value C2.

[0030] Therefore, as shown in (e), the rotation speed of the internal combustion engine 1, that is, the idle rotation speed, does not fluctuate.

[0031] FIG. 2 is a flowchart showing the flow of processing executed by the controller 6 when switching control modes to realize the above-mentioned operation. In step 1, it is determined whether or not there is a voltage request during the current field current limit control. If the result is YES, the process proceeds to step 2, where the control is switched to voltage limit control while the field current command value C1 is maintained at the previous value. In other words, the change of the voltage command value C2 is started. In the next step 3, it is determined whether the voltage command value C2 has reached the target value, and the process returns to step 2 to continue changing the voltage command value C2 until the target value is reached. When the voltage command value C2 has reached the target value, the process proceeds to step 4, where the change of the field current command value C1 is started.

[0032] On the other hand, if the judgment in step 1 is NO, the process proceeds to step 5, where it is judged whether or not voltage limit control is currently in progress and there is a request to limit the field current. If it is NO, the routine ends. If it is YES, such as due to SOC recovery, the process proceeds to step 6, where control is switched to field current limit control while maintaining the voltage command value C2 at the previous value. In other words, the change in the field current command value C1 begins. In the next step 7, it is judged whether the field current command value C1 has reached the target value, and the process returns to step 6 to continue changing the field current command value C1 until the target value is reached. Once the field current command value C1 has reached the target value, the process proceeds to step 8, where the change in the voltage command value C2 begins.

[0033] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the control mode switching during idling operation of the internal combustion engine 1 has been described, but the present invention can be similarly applied to control mode switching during other than idling operation, and rotation fluctuations of the internal combustion engine caused by a temporary increase in generator torque can be suppressed in the same way as in the above embodiment. Furthermore, the present invention is not limited to a power generation circuit including a battery with a nominal voltage of 12V, and the above-mentioned voltage values ​​are merely examples. [Explanation of symbols]

[0034] 1. Internal combustion engine 2. Generator 4. Battery 5. Regulator 6…Controller

Claims

1. A load control method for a generator driven by the power of an internal combustion engine has, as control modes, a field current limiting control for limiting a field current in accordance with a field current command value and a voltage limiting control for limiting a voltage in accordance with a voltage command value, and switches between the two control modes according to requirements, When switching from the field current limit control to the voltage limit control, the voltage command value is gradually changed to a target value in the voltage limit control while the field current command value is held at the value immediately before the switching, and when the target value is reached, the change of the field current command value is started. A method for controlling the load of a generator.

2. A load control method for a generator driven by the power of an internal combustion engine has, as control modes, a field current limiting control for limiting a field current in accordance with a field current command value and a voltage limiting control for limiting a voltage in accordance with a voltage command value, and switches between the two control modes according to requirements, When switching from voltage limit control to field current limit control, the field current command value is gradually changed to a target value in the field current limit control while the voltage command value is held at the value immediately before the switching, and when the target value is reached, the change of the voltage command value is started. A method for controlling the load of a generator.

3. The internal combustion engine is an internal combustion engine that drives a vehicle, During idling of the internal combustion engine, the field current limiting control is given priority, and when there is a voltage request, the control is switched to the voltage limiting control. The method for controlling a load of a generator according to claim 1.

4. In the field current limit control, the field current command value is controlled to a limit value corresponding to an allowable torque allowed for driving the generator, and in the voltage limit control, the field current command value is set to a relatively large predetermined maximum value.

3. A method for controlling a load of a generator according to claim 1 or 2.

5. In the voltage limit control, the voltage command value is controlled to a target value according to a request, and in the field current limit control, the voltage command value is set to a relatively high predetermined maximum value.

3. A method for controlling a load of a generator according to claim 1 or 2.

6. A generator driven by the power of the internal combustion engine; A controller having control modes of the generator including a field current limiting control for limiting a field current in accordance with a field current command value and a voltage limiting control for limiting a voltage in accordance with a voltage command value, and switching between the two control modes according to requirements; A load control device for a generator comprising: The above controller is When switching from the field current limit control to the voltage limit control, the voltage command value is gradually changed to a target value in the voltage limit control while the field current command value is held at the value immediately before the switching, and when the target value is reached, the change of the field current command value is started. Generator load control device.

7. A generator driven by the power of the internal combustion engine; A controller having control modes of the generator including a field current limiting control for limiting a field current in accordance with a field current command value and a voltage limiting control for limiting a voltage in accordance with a voltage command value, and switching between the two control modes according to requirements; A load control device for a generator comprising: The above controller is When switching from voltage limit control to field current limit control, the field current command value is gradually changed to a target value in the field current limit control while the voltage command value is held at the value immediately before the switching, and when the target value is reached, the change of the voltage command value is started. Generator load control device.

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