JP6420685B2 - Electronic control unit - Google Patents

Description

  The present invention relates to an electronic control device that controls a current to be controlled with a duty ratio.

  As described in JP 2009-180348 A (Patent Document 1), as an electronic control device that controls a current to be controlled with a duty ratio, a duty ratio set according to a target current and a power supply voltage is controlled. A technique has been proposed in which correction is performed according to a deviation between a current that actually flows (actual current) and a target current.

JP 2009-180348 A

  A solenoid mentioned as an example of a control target has a characteristic that the load resistance changes according to the ambient temperature. For this reason, at low temperatures when the load resistance of the solenoid is low, the actual current cannot follow the change in the target current immediately after the target current changes. There was a risk of impacting.

  Accordingly, an object of the present invention is to provide an electronic control device that has little influence on responsiveness and controllability even when the target current changes.

The electronic control unit sets the duty ratio based on the target current and the power supply voltage changes stepwise with time, the control object and a current controlled in accordance with the duty ratio, the actual current actually flowing to the control target And the duty ratio are corrected in accordance with the deviation from the target current. At this time, the electronic control unit latches the duty ratio immediately before the change of the target current, and when the target current changes, if the target current decreases and the target current is less than the actual current, the latched duty ratio and the target If the smaller duty ratio set based on the current and power supply voltage is selected and the target current decreases and the target current is greater than the actual current or the target current increases, the latched duty ratio and the target current Then, the larger duty ratio set based on the power supply voltage is selected .

  According to the present invention, even if the target current changes, the influence on the responsiveness and controllability can be reduced.

It is a schematic diagram showing an example of a power transmission system of a four-wheel drive vehicle. It is an internal block diagram which shows an example of a diff lock control unit. It is a time chart which shows an example of the setting method of target current. It is a flowchart which shows an example of the electricity supply control to a solenoid. It is a figure which shows an example of the map which calculates | requires basic duty ratio. It is a figure which shows an example of the map which calculates | requires a correction coefficient. It is a time chart explaining an example of an effect | action when a target electric current falls. It is a time chart explaining the other example of an effect | action when a target electric current falls. It is a time chart explaining an example of an effect | action when a target electric current rises. It is a flowchart which shows the other example of the electricity supply control to a solenoid. It is a time chart explaining an example of an effect | action when a target electric current changes stepwise. It is a time chart explaining the other example of an effect | action in case a target electric current changes stepwise.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of a power transmission system of a four-wheel drive vehicle. The four-wheel drive vehicle 50 includes a rear differential device 1 that can lock the differential mechanism between the rear wheels 2 and 3, and a front differential device 4 that cannot lock the differential mechanism between the front wheels 5 and 6.

Torque is input from the engine 7 to the rear differential device 1 through the transmission 8, the transfer 9, the propeller shaft 10, the drive pinion shaft 11, and the drive pinion gear 12, and the left and right axle shafts 13 and 14 are moved from the rear differential device 1. Torque is transmitted to the left and right rear wheels 2, 3 through the vias.
Torque is input to the front differential device 4 from the engine 7 through the transmission 8, the transfer 9, and the propeller shaft 15. From the front differential device 4 to the front wheels 5 and 6 through the left and right axle shafts 16 and 17, respectively. Torque is transmitted.

The rear differential device 1 includes a differential case 21, and a drive pinion gear 12 meshes with a ring gear 22 of the differential case 21.
Left and right side gears 23 and 24 are rotatably supported in the differential case 21, and a pinion gear 25 is engaged with the side gears 23 and 24, and the pinion gear 25 is rotatably supported by the differential case 21 by a pinion shaft 26. The left and right side gears 23 and 24 are connected to the axle shafts 13 and 14.

  A plunger 27 is disposed on the back side of one side gear 24 so as to be movable in the axial direction of the axle shaft 14, and a dog clutch 28 is provided on the opposing surface of the side gear 24 and the plunger 27. Between the side gear 24 and the plunger 27, a return spring (not shown) that elastically biases the plunger 27 in a direction away from the side gear 24 is interposed.

  The plunger 27 moves in the direction of the side gear 24 by excitation of the solenoid 29 (control target), and the plate 30 moves as the plunger 27 moves. The differential lock detection switch 45 detects locking and release of the differential mechanism of the rear differential device 1 by detecting the movement position of the plate 30.

Energization of the solenoid 29 is controlled by a differential lock control unit 40 (electronic control device).
As shown in FIG. 2, the diff lock control unit 40 includes an input circuit 40a, a microcomputer 40b, a drive circuit 40c, a current monitor circuit 40d, and the like, and controls the locking / unlocking of the differential mechanism by the diff lock 41. To do.
Here, as described above, the differential lock 41 controls the energization of the solenoid 29 to move the plunger 27, and the differential mechanism of the rear differential device 1 is set to the locked state and the unlocked state depending on the movement position of the plunger 27. It is a switching device.

  In the diff lock control unit 40, an ON / OFF signal of a diff lock detection switch 45, an ON / OFF signal of a diff lock operation switch 42 arbitrarily operated by a driver, a vehicle speed signal of a vehicle speed sensor 43, and a shift position for detecting a gear position of the transmission 8 A shift position signal of the sensor 44, wheel speed information regarding the rear wheels 2 and 3 from the ABS control unit 35, engine torque information from the engine control unit 36, and the like are input to the microcomputer 40b via the input circuit 40a. The ABS control unit 35 inputs wheel speed signals from wheel speed sensors 31 to 34 provided on the wheels 2, 3, 5, and 6, respectively.

  When the diff lock operation switch 42 is turned on by the driver, the diff lock control unit 40 inputs the ON signal of the diff lock operation switch 42 as a lock operation command for the differential mechanism of the rear differential device 1, and each input signal And energization control (PWM control) of the solenoid 29 is performed based on the input information.

  As engine torque information, for example, information such as the fuel injection amount, the throttle opening degree, and the intake air amount can be used. The differential lock control unit 40 can directly input the detection outputs of the wheel speed sensors 31 and 32 without going through the ABS control unit 35.

FIG. 3 shows a process for setting the target current of the solenoid 29 during the differential lock operation by the differential lock control unit 40.
In FIG. 3, when the diff lock control unit 40 inputs an ON signal (lock operation command) of the diff lock operation switch 42 at time t1, the target current ECtg of the solenoid 29 is large enough to move the plunger 27 from 0A. Drive current EC1 (for example, EC1 = 4 A).

  After that, when the differential lock detection switch 45 is switched from OFF to ON at time t2, and it is detected that the differential mechanism of the rear differential device 1 is switched from the unlocked state to the locked state, at the subsequent time t3, the differential lock control unit 40 decreases the target current ECtg stepwise from the drive current EC1 to an intermediate current EC2 (for example, EC2 = 3A) lower than the drive current EC1.

  Note that time t3, which is the timing for lowering the target current ECtg from the drive current EC1 to the intermediate current EC2, is a predetermined time after the time t1, or a predetermined time after the diff lock detection switch 45 is switched from OFF to ON at the time t2. can do. Furthermore, the target current ECtg can be lowered from the drive current EC1 to the intermediate current EC2 at time t2 when the diff lock detection switch 45 is switched from OFF to ON.

At time t4 when a predetermined time has elapsed from time t3, the diff lock control unit 40 reduces the target current ECtg to a value lower than the intermediate current EC2 than the intermediate current EC2, and a holding current EC3 (for example, sufficient to hold the plunger 27 in the locked position). EC3 = 1A), and the target current ECtg is maintained at the holding current EC3 until a lock release command is input.
At time t5, an operation to turn off the diff lock operation switch 42 is performed. When this OFF signal (unlock command) is input to the diff lock control unit 40, the diff lock control unit 40 obtains the target current ECtg from the holding current EC3. Step down to 0A.
As a result, the energization of the solenoid 29 is interrupted, and the plunger 27 is moved to the unlock position by the urging force of the return spring. When the lock is released, the differential lock detection switch 45 is switched from ON to OFF.

That is, the target current ECtg rises from 0A to the drive current EC1 based on the lock command, and then decreases stepwise with time from the intermediate current EC2 to the holding current EC3.
In the example shown in FIG. 3, the target current ECtg is lowered stepwise in the order of the drive current EC1, the intermediate current EC2, and the holding current EC3. However, as the intermediate current EC2 that is lower than the drive current EC1 and higher than the holding current EC3. A plurality of types having different levels can be set and the target current ECtg can be switched to four or more types.
For example, the driving current EC1> the first intermediate current EC2a> the second intermediate current EC2b> the holding current EC3, and the target current ECtg is driven in the order of the driving current EC1, the first intermediate current EC2a, the second intermediate current EC2b, and the holding current EC3. The current EC1 can be lowered stepwise toward the holding current EC3.

The diff lock control unit 40 performs PWM control (duty control) of energization of the solenoid 29 so that the actual energization current follows the target current ECtg that is stepwise decreased from the drive current EC1 toward the holding current EC3. . Here, the actual energization current (current actually flowing through the solenoid 29) is detected by the current monitor circuit 40d.
Specifically, the diff lock control unit 40 sets a reference duty ratio based on the target current ECtg and the power supply voltage (battery voltage) VB, and current-controls the solenoid 29 according to the reference duty ratio. Further, the diff lock control unit 40 corrects the reference duty ratio (feedback control) according to the deviation between the actual energization current of the solenoid 29 and the target current ECtg.

At this time, the diff lock control unit 40 latches (holds) the reference duty ratio immediately before the change of the target current ECtg, and when the target current ECtg changes, the latched reference duty ratio, the target current ECtg and the power supply voltage VB. One of the reference duty ratios set based on is selected.
Hereinafter, the description of the energization control of the solenoid 29 by the differential lock control unit 40 will be continued with reference to flowcharts and the like.

FIG. 4 shows an example of energization control that the diff lock control unit 40 repeatedly executes at predetermined time intervals when the diff lock control unit 40 is activated by the operation of the ignition switch.
The differential lock control unit 40 performs energization control according to a control program stored in a nonvolatile memory such as a flash ROM (Read Only Memory), for example (the same applies hereinafter).

  In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the differential lock control unit 40 sets a reference duty ratio based on the target current ECtg and the power supply voltage VB. Specifically, as shown in FIG. 5, the diff lock control unit 40 refers to a map in which the target current and the basic duty ratio are associated with each other, and obtains a basic duty ratio corresponding to the target current ECtg. Further, as shown in FIG. 6, the diff lock control unit 40 refers to a map in which the power supply voltage and the correction coefficient are associated with each other, and obtains a correction coefficient corresponding to the power supply voltage VB. Then, the diff lock control unit 40 obtains a reference duty ratio by multiplying the basic duty ratio by the correction coefficient (reference duty ratio = basic duty ratio × correction coefficient).

Here, a method for obtaining the reference duty ratio will be described with a specific example.
When the target current ECtg is 2 A, the basic duty ratio is 50% from the map shown in FIG. Further, when the power supply voltage VB is 10.6 V (when charging is slightly insufficient), the correction coefficient is 1.4 from the map shown in FIG. The reference duty ratio is calculated as 50 (%) × 1.4 = 70 (%).

  In step 2, the diff lock control unit 40 determines whether or not the target current ECtg has changed. If the diff lock control unit 40 determines that the target current ECtg has changed (Yes), it proceeds to step 3. On the other hand, if the diff lock control unit 40 determines that the target current ECtg does not change (No), the process proceeds to step 8. In order to avoid erroneous determination due to noise superposition or the like, it can be determined that the target current ECtg has changed when the target current ECtg has changed by a predetermined value or more.

  In step 3, the differential lock control unit 40 latches the reference duty ratio immediately before the target current ECtg changes. In the following description, the latched reference duty ratio is referred to as “latch duty ratio”.

  In step 4, the diff lock control unit 40 determines whether or not the target current ECtg has decreased. When the diff lock control unit 40 determines that the target current ECtg has decreased (Yes), the process proceeds to step 5. On the other hand, if the diff lock control unit 40 determines that the target current ECtg has not decreased, that is, the target current ECtg has increased (No), the process proceeds to step 7.

  In step 5, the diff lock control unit 40 determines whether or not the target current ECtg is equal to or less than the actual energization current. If the differential lock control unit 40 determines that the target current ECtg is equal to or less than the actual energization current (Yes), the process proceeds to step 6. On the other hand, if the diff lock control unit 40 determines that the target current ECtg is not less than or equal to the actual energization current, that is, the target current ECtg is greater than the actual energization current (No), the process proceeds to Step 7.

  In step 6, the differential lock control unit 40 selects the smaller one of the reference duty ratio and the latch duty ratio as the final output duty ratio output to the solenoid 29 (output duty ratio = min (reference duty ratio, Latch duty ratio)).

  In step 7, the diff lock control unit 40 selects the larger one of the reference duty ratio and the latch duty ratio as the final output duty ratio to be output to the solenoid 29 (output duty ratio = max (reference duty ratio, Latch duty ratio)).

  In step 8, the differential lock control unit 40 feedback-controls the output duty ratio according to the deviation between the target current ECtg and the actual energization current. In short, the diff lock control unit 40 feedback-controls the output duty ratio by, for example, known PI control (proportional integral control) so that the actual energization current approaches (converges) the target current ECtg.

According to such energization control, the reference duty ratio is set based on the target current ECtg and the power supply voltage VB every predetermined time after the activation of the differential lock control unit 40.
In a steady state where the target current ECtg does not change, the output duty ratio is feedback-controlled so that the actual energization current approaches the target current ECtg.

When the target current ECtg changes, the reference duty ratio immediately before the target current ECtg changes is latched.
When the target current ECtg decreases, if the actual energization current reaches the target current ECtg at the time when the target current ECtg decreases, there is no need to increase the output duty ratio. The smaller one is selected from the latch duty ratios. In this way, when the target current ECtg decreases, the reference duty ratio is not selected as the output duty ratio, and the output duty ratio does not increase rapidly as shown by the broken line in FIG. For this reason, as shown by a broken line in FIG. 7, an increase in the actual energization current due to a sudden increase in the output duty ratio is avoided, and overshoot can be suppressed.

  Further, when the target current ECtg is decreased, it is not necessary to decrease the output duty ratio unless the actual energization current reaches the target current ECtg at the time when the target current ECtg decreases. The larger one is selected from the latch duty ratios. In this way, when the target current ECtg decreases, the reference duty ratio is not selected as the output duty ratio, and the output duty ratio does not rapidly decrease as shown by the broken line in FIG. For this reason, as shown by a broken line in FIG. 8, a decrease in the actual energization current due to a sudden decrease in the output duty ratio is avoided, and undershoot can be suppressed.

  On the other hand, when the target current ECtg rises, it is not necessary to lower the output duty ratio, so the larger one is selected from the reference duty ratio and the latch duty ratio as the output duty ratio. In this way, when the target current ECtg increases, the latch duty ratio is not selected as the output duty ratio, and the output duty ratio does not rapidly decrease as shown by the broken line in FIG. For this reason, as shown by a broken line in FIG. 9, a decrease in the actual energization current due to a sudden decrease in the output duty ratio is avoided, and undershoot can be suppressed.

  Therefore, even if the target current ECtg changes, undershoot or overshoot is unlikely to occur, and the influence on the response, controllability, etc. of the solenoid 29 to be controlled can be suppressed.

  FIG. 10 shows another example of energization control that the diff lock control unit 40 repeatedly executes at predetermined time intervals when the diff lock control unit 40 is activated by the operation of the ignition switch. It is assumed that the target current ECtg changes stepwise as shown in FIG. In addition, about the process which is common with an example of previous electricity supply control, in order to avoid duplication description, the description will be simplified.

In step 11, the differential lock control unit 40 sets a reference duty ratio based on the target current ECtg and the power supply voltage VB.
In step 12, the diff lock control unit 40 determines whether or not the target current ECtg has changed. If the diff lock control unit 40 determines that the target current ECtg has changed (Yes), it proceeds to step 13. On the other hand, if the diff lock control unit 40 determines that the target current ECtg does not change (No), the process proceeds to step 21.

  In step 13, the differential lock control unit 40 determines whether the target current ECtg after the change is the same as the previous target current ECtg, for example, the target current ECtg is 4A (previous) → 3A (previous) → 4A (current) ). If the differential lock control unit 40 determines that the target current ECtg after the change is the same as the previous target current ECtg (Yes), the process proceeds to step 14. On the other hand, if the differential lock control unit 40 determines that the changed target current ECtg is not the same as the previous target current ECtg (No), the process proceeds to step 15.

  In step 14, the differential lock control unit 40 determines whether or not the value of the counter that measures the elapsed time (reset to 0 in the initial state) has reached a predetermined value. It is determined whether or not it has elapsed. Here, the predetermined value is a threshold value for determining whether or not the temperature of the solenoid 29 has changed due to a change in the target current ECtg and the load resistance of the solenoid 29 has changed. It can be appropriately set in consideration of characteristics and the like. The predetermined value can also be set dynamically according to the target current ECtg, for example. If the differential lock control unit 40 determines that the value of the counter has reached a predetermined value (Yes), the process proceeds to step 15. On the other hand, if the differential lock control unit 40 determines that the value of the counter has not reached the predetermined value (No), the process proceeds to step 18.

In step 15, the differential lock control unit 40 latches the reference duty ratio immediately before the target current ECtg changes.
In step 16, the differential lock control unit 40 resets the counter to 0 in order to start measuring the elapsed time after latching the reference duty ratio.
In step 17, the differential lock control unit 40 selects a reference duty ratio from the reference duty ratio and the latch duty ratio as the output duty ratio.

In step 18, the differential lock control unit 40 selects a latch duty ratio as an output duty ratio from the reference duty ratio and the latch duty ratio.
In step 19, the differential lock control unit 40 latches the reference duty ratio immediately before the target current ECtg changes.
In step 20, the differential lock control unit 40 resets the counter to 0 in order to start measuring the elapsed time after latching the reference duty ratio.

In step 21, the diff lock control unit 40 increments the counter, that is, adds 1 to the counter.
In step 22, the diff lock control unit 40 feedback-controls the output duty ratio according to the deviation between the target current ECtg and the actual energization current.

According to such energization control, the reference duty ratio is set based on the target current ECtg and the power supply voltage VB every predetermined time after the activation of the differential lock control unit 40.
In a steady state where the target current ECtg does not change, the counter that measures the elapsed time after latching the reference duty ratio is incremented and the output duty ratio is set so that the actual energization current approaches the target current ECtg. Feedback controlled.

  When the target current ECtg changes, the target current ECtg after the change is the same as the target current ECtg the previous time, and if the predetermined time has not elapsed since the reference duty ratio was latched, the latch duty ratio is output as the output duty ratio. (The reference duty ratio of the previous cycle) is selected. In addition, after the selection of the latch duty ratio, the reference duty ratio immediately before the target current ECtg changes is latched and the counter is reset to 0 in order to update it. In this way, when the target current ECtg changes, the reference duty ratio is not selected as the output duty ratio, and the output duty ratio does not change suddenly (for example, rapidly increase) as shown by the broken line in FIG. For this reason, as shown by a broken line in FIG. 11, a change (for example, an increase) in the actual energization current due to a sudden change in the output duty ratio is avoided, and an overshoot or the like can be suppressed.

  However, even if the target current ECtg after the change is the same as the target current ECtg the last time, if the predetermined time has elapsed since the reference duty ratio was latched, for example, the solenoid 29 is caused by the change in the target current ECtg. The temperature may have changed. In this case, it is possible to suppress the solenoid 29 from being controlled with an uncertain output duty ratio by selecting the reference duty ratio instead of the latch duty ratio at the time when the target current ECtg changes. When the target current ECtg changes, the output duty ratio may temporarily increase as shown by the broken line in FIG. 12, but as shown by the broken line in the figure due to the load resistance change of the solenoid 29. The overshoot of the actual energizing current is reduced. Also in this case, the reference duty ratio immediately before the target current ECtg changes is latched and the counter is reset to 0 in order to update the latch duty ratio.

  Accordingly, similarly to the previous energization control, even if the target current ECtg changes, undershoot or overshoot is unlikely to occur, and the influence on the responsiveness and controllability of the solenoid 29 which is an example of the control target is suppressed. Can do.

  In the above embodiment, the solenoid 29 of the rear differential device 1 is the control target. However, the present invention is not limited to this, and for example, a solenoid that controls the wet multi-plate clutch of the transfer 9 can also be the control target.

29 Solenoid (control target)
40 Differential lock control unit (electronic control unit)

Claims (3)

A duty ratio is set based on a target current and a power supply voltage that change stepwise as time elapses, and the current to be controlled is controlled according to the duty ratio, and the actual current actually flowing to the control target and the target An electronic control device that corrects the duty ratio according to a deviation from a current,
Means for latching the duty ratio immediately before the change of the target current;
When the target current is changed, if the target current is reduced and the target current is equal to or less than the actual current, the latched duty ratio, the duty ratio set based on the target current and the power supply voltage are set. If the smaller one is selected and the target current is reduced and the target current is greater than the actual current or the target current is increased, then based on the latched duty ratio, the target current and the power supply voltage Means for selecting a larger duty ratio, and
An electronic control device comprising: It means for selecting the duty ratio, when the target current is changed to the same value as before last, selecting a duty ratio latched at that time,
The electronic control device according to claim 1. The means for selecting the duty ratio prohibits selection of the duty ratio latched by the change in the target current when a predetermined time has elapsed since the change in the target current.
The electronic control device according to claim 1 or 2, characterized by the above.