JP2012121403A5 - - Google Patents

Description

Driving force distribution device

  The present invention relates to a driving force distribution device.

Conventionally, there is a driving force distribution device capable of changing the driving force distribution between main driving wheels and auxiliary driving wheels.
Many of these driving force distribution devices change the torque transmitted from the input side to the output side by a torque coupling provided in the middle of the driving force transmission system, so that the main driving wheel and the auxiliary driving wheel during that adapted to control the driving force distribution (for example, Patent Document 1).

  The torque coupling is mainly composed of a friction clutch and an electromagnetic coil, and the torque transmitted from the input side to the output side can be changed by controlling the coupling force of the friction clutch by the current value applied to the electromagnetic coil. It is configured as follows. Since the friction clutch generates heat due to friction, a temperature sensor is attached to the torque coupling in order to prevent the friction clutch from being seized due to the heat generation, and is applied to the electromagnetic coil according to the detected temperature. The current value is controlled.

  The temperature sensor has temperature sensor high temperature abnormality detection means for detecting an abnormality when the ambient temperature becomes a predetermined value or more. Moreover, it has the temperature sensor ground fault abnormality detection means which detects ground faults, such as a ground fault of temperature sensor itself, or wiring of a temperature sensor.

  When the value of the temperature sensor rises and exceeds a predetermined value, a temperature sensor high temperature abnormality alarm (for example, lamp lighting) is output, and the torque transmitted from the input side to the output side of the torque coupling is weakened. The current applied to the electromagnetic coil of the coupling is gradually decreased so as to weaken the coupling force. That is, the 4WD control is switched to the 2WD control. By doing so, seizure of the friction clutch is prevented.

  Also, when the temperature sensor itself has a ground fault, or when the temperature sensor wiring or the like has a ground fault, a temperature sensor short circuit abnormality alarm (for example, lamp lighting) is output and applied to the electromagnetic coil of the torque coupling. Cut off current. By doing so, the temperature sensor itself and its surroundings are prevented from being burned out.

Next, a general hardware configuration and software processing around the temperature sensor for detecting the temperature sensor high temperature abnormality and the temperature sensor short circuit abnormality will be described.
FIG. 5 shows a general hardware configuration for taking the output of the temperature sensor 18 into the ECU 12. A positive terminal A1 of the temperature sensor 18 is connected to one end of a filter 22 (capacitor C1, resistor R2) provided in the ECU 12 and a voltage divider 23 (resistors R1, R2) that divides the voltage of the battery 19, and the CPU 20 Is input.
The negative terminal A2 of the temperature sensor 18 is connected to GND together with the filter 22 (capacitor C1, resistor R2) provided in the ECU 12.

  Next, software processing will be described. FIG. 6 is a flowchart showing determination of the high temperature abnormality of the temperature sensor 18 and its processing. First, the temperature sensor voltage Vth is captured (step 301). Next, the temperature sensor voltage high temperature abnormality threshold value Vths1 is fetched (step 302). Then, it is determined whether or not the temperature sensor voltage Vth is smaller than the temperature sensor voltage abnormal temperature threshold Vths1 (step 303).

  If the temperature sensor voltage Vth is smaller than the temperature sensor voltage high temperature abnormality threshold Vths1 (Vth <Vths1, step 303: YES), it is determined that the temperature sensor is abnormally high temperature (step 304). Then, the lamp is turned on as a temperature sensor high temperature abnormality alarm (step 305), and control for distributing the driving force to the main driving wheel (2WD control) from the control for distributing the driving force for the main driving wheel and the auxiliary driving wheel (4WD control). Therefore, the current value to the friction clutch is gradually decreased (step 306), and the process is terminated.

  FIG. 7 is a flowchart showing determination of the ground fault abnormality of the temperature sensor 18 and its processing. First, the temperature sensor voltage Vth is captured (step 401). Next, the temperature sensor voltage ground fault abnormality threshold value Vths2 is fetched (step 402). Then, it is determined whether or not the temperature sensor voltage Vth is smaller than the temperature sensor voltage ground fault abnormality threshold value Vths2 (step 403).

  When the temperature sensor voltage Vth is smaller than the temperature sensor voltage ground fault abnormality threshold value Vths2 (Vth <Vths2, step 403: YES), it is determined that the temperature sensor ground fault is abnormal (step 404). Then, the lamp is turned on as a temperature sensor ground fault alarm (step 405), and the current to the friction clutch is immediately cut off (step 406) to immediately switch from 4WD control to 2WD, and the process is terminated.

  Next, FIGS. 8 and 9 are diagrams for explaining temperature sensor voltage waveforms when the temperature sensor 18 is abnormally hot or when the ground fault is abnormal. FIG. 8 is a temperature sensor voltage waveform when a temperature sensor high temperature abnormality is detected. In general, the temperature sensor voltage (eg, thermistor) decreases as the temperature increases. As shown in FIG. 8, when the temperature sensor voltage Vth becomes smaller than the temperature sensor voltage high temperature abnormality threshold value Vths1, it is determined that the temperature sensor is high temperature abnormality (step 303 in FIG. 6).

FIG. 9 is a temperature sensor voltage waveform when the temperature sensor ground fault abnormality is detected. The temperature sensor voltage Vth is in the vicinity of the voltage V0 obtained by dividing the voltage of the battery 19 by the voltage divider 23 shown in FIG. When the temperature sensor 18 is grounded at the time t0, the temperature sensor voltage Vth rapidly decreases. As shown in FIG. 9, when the temperature sensor voltage Vth becomes lower than the temperature sensor voltage ground fault abnormality threshold value Vths2, it is determined that the temperature sensor ground fault is abnormal (step 403 in FIG. 7).

JP2003-136990

  In the conventional temperature sensor abnormality (high temperature abnormality, ground fault abnormality) detection method as described above, as is apparent from FIGS. 8 and 9, the temperature sensor voltage Vth (= temperature sensor) when the temperature sensor becomes high temperature. Voltage threshold value Vths1) at the time of voltage high temperature abnormality and temperature sensor voltage Vth (= temperature sensor voltage ground fault abnormality threshold value Vths2) when the temperature sensor has a ground fault abnormality, both voltage values are almost the same value. There is a case.

  Therefore, there is a case where the temperature sensor 18 is erroneously determined as a ground fault abnormality in spite of a case where the temperature sensor 18 is abnormally hot. If the temperature sensor ground fault abnormality is erroneously determined in this way, the 4WD control is immediately switched to the 2WD control. Therefore, when the low μ road curve is switched during traveling, the vehicle traveling becomes unstable. There was a problem.

  The present invention has been made to solve the above-described problems, and its purpose is to accurately determine a temperature sensor high temperature abnormality and a temperature sensor ground fault abnormality, and travel the vehicle when switching from 4WD to 2WD. An object of the present invention is to provide a driving force distribution device with improved stability.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a transmission torque that is provided in the middle of a driving force transmission system that transmits a driving force generated by a driving source to each driving wheel and is transmitted from the input side to the output side. A torque coupling (11) capable of changing the driving force distribution between the main driving wheel and the auxiliary driving wheel by changing the temperature, and a temperature sensor (18) for detecting a temperature change of the torque coupling (11), , Temperature estimation means (CPU, 20) for estimating a temperature change based on a transmission torque of the torque coupling (11), and a temperature sensor for determining abnormality of the temperature sensor based on the temperature change detected by the temperature sensor (18) Based on the determination by the abnormality determination means (CPU, 20) and the temperature sensor abnormality determination means (CPU, 20), the control means (control unit) controls the operation of the torque coupling (11). PU, 20), and the temperature sensor abnormality determining means (CPU, 20) is configured such that the temperature detection value detected by the temperature sensor (18) is a temperature sensor voltage threshold 1. If the temperature estimated value estimated by the temperature estimation means (CPU, 20) is smaller than the temperature sensor voltage threshold 2, it is determined that the temperature sensor (18) is abnormally hot, and the control means (CPU, The gist of 20) is that the driving force distribution is gradually switched from the distribution by the main driving wheel and the auxiliary driving wheel to the distribution by only the main driving wheel.

  According to the above configuration, when the temperature detection value detected by the temperature sensor is smaller than the temperature sensor voltage threshold value 1 and the estimated temperature value estimated by the temperature estimation means is larger than the temperature sensor voltage threshold value 2, the temperature sensor is abnormally hot. It can be judged accurately. In such a high temperature abnormality of the temperature sensor, since the driving force distribution is gradually switched to only the main driving wheel, the main driving wheel and the auxiliary driving wheel are controlled to distribute the driving force without making the vehicle running unstable. It is possible to switch to control that distributes the driving force only to the driving wheels.

  The temperature sensor abnormality determining means (CPU, 20) is characterized in that the temperature detection value detected by the temperature sensor (18) is smaller than the temperature sensor voltage threshold 1 and the temperature estimating means (CPU 20), when the estimated temperature value is smaller than the temperature sensor voltage threshold 2, it is determined that the temperature sensor (18) has a ground fault, and the control means (CPU, 20) determines the distribution of the driving force. The gist is to immediately switch to the distribution of only the main drive wheels.

  According to the above configuration, the temperature sensor abnormality determination unit is configured such that the temperature detection value detected by the temperature sensor is smaller than the temperature sensor voltage threshold value 1 and the temperature estimation value estimated by the temperature estimation unit is smaller than the temperature sensor voltage threshold value 2. Determines that the temperature sensor ground fault is abnormal. In such a ground fault abnormality of the temperature sensor, it is possible to immediately switch to the driving force distribution of only the main driving wheels.

  According to the present invention, the temperature sensor abnormality (high temperature abnormality, ground fault abnormality) can be accurately determined, so that the control for distributing the driving force only to the main driving wheel is controlled from the control for distributing the driving force to the main driving wheel and the auxiliary driving wheel. It is possible to provide a driving force distribution device that improves the stability of vehicle travel when switching.

1 is a schematic configuration diagram of a vehicle including a driving force distribution device according to an embodiment of the present invention. The flowchart figure which shows the process sequence which memorize | stores temperature when the ignition switch (IG) of the temperature sensor of embodiment of this invention is OFF. The flowchart figure which shows the process sequence which determines the high temperature abnormality and ground fault abnormality of the temperature sensor of embodiment of this invention. The flowchart figure which shows the process sequence which determines the high temperature abnormality and ground fault abnormality of the temperature sensor of embodiment of this invention. The hardware block diagram of a temperature sensor. The flowchart figure which shows the process sequence of temperature sensor high temperature abnormality. The flowchart figure which shows the process sequence of temperature sensor ground fault abnormality. The temperature sensor voltage waveform figure at the time of temperature sensor high temperature abnormality. The temperature sensor voltage waveform figure at the time of temperature sensor ground fault abnormality.

Hereinafter, an embodiment in which the present invention is embodied in a driving force distribution device for a four-wheel drive vehicle will be described with reference to the drawings.
As shown in FIG. 1, the vehicle 1 is a four-wheel drive vehicle based on a front-wheel drive vehicle, and a pair of front axles 4 are connected to a transaxle 3 assembled to the engine 2. Further, a propeller shaft 5 is connected to the transaxle 3 together with the front axles 4, and the propeller shaft 5 is connected to a pinion shaft (drive pinion shaft) 7. The pinion shaft 7 is connected to a pair of rear axles 9 via a rear differential 8 as a differential.

  That is, the driving force of the engine 2 is transmitted from the transaxle 3 to the front wheels 10f via the front axle 4. Then, the power is transmitted from the transaxle 3 to the rear wheel 10r through the propeller shaft 5, the pinion shaft 7, the rear differential 8, and the rear axles 9.

  Further, the vehicle 1 of the present embodiment is provided in the middle of the driving force transmission system configured as described above, and changes the transmission torque transmitted from the input shaft to the output shaft, thereby changing the front wheels 10f that are the main driving wheels. A torque coupling 11 capable of changing the driving force distribution with respect to the rear wheel 10r, which is the auxiliary driving wheel, and an ECU 12 as control means for controlling the operation thereof are provided. In this embodiment, the torque coupling 11 and the ECU 12 constitute a driving force distribution device 13.

  More specifically, in this embodiment, the torque coupling 11 is interposed between the propeller shaft 5 and the pinion shaft 7. That is, in this embodiment, the rear differential 8 is interposed between the torque coupling 11 and the rear wheel 10r that is the auxiliary drive wheel, and the transaxle 3 is connected between the engine 2 that is the drive source and the torque coupling 11. It is provided in between.

  In this embodiment, the torque coupling 11 is housed in the differential carrier 14 together with the pinion shaft 7 and the rear differential 8.

  The torque coupling 11 of the present embodiment is an electromagnetic clutch in which the frictional engagement force between the clutch plates provided on the propeller shaft 5 side and the pinion shaft 7 side changes according to the amount of current supplied to the electromagnetic coil. 15, and transmits torque based on the frictional engagement force from the input-side propeller shaft 5 to the output-side pinion shaft 7.

  The ECU 12 controls the operation of the torque coupling 11 through the current supply to the electromagnetic clutch 15, that is, its transmission torque, thereby driving between the front wheel 10f as the main driving wheel and the rear wheel 10r as the auxiliary driving wheel. Control power distribution.

  More specifically, in this embodiment, the ECU 12 is connected to a throttle opening sensor 16 and wheel speed sensors 17fl, 17fr, 17rl, 17rr, and a temperature sensor 18 attached to the torque coupling 11, and the ECU 12 Based on the output signals of these sensors, the throttle opening Ra, the vehicle speed V, the wheel speed difference Wdiff between the front wheels 10f and the rear wheels 10r, and the temperature of the torque coupling 11 are detected. The detected value of the temperature sensor 18 is such that the voltage decreases as the temperature changes from low to high.

  Then, the ECU 12 determines the driving force distribution based on the vehicle speed V, the throttle opening Ra, and the wheel speed difference Wdiff, and the torque so that the transmission torque becomes a value corresponding to the determined driving force distribution. The operation of the coupling 11 is controlled.

Next, the control method of this embodiment will be described.
First, when an unillustrated ignition switch (IG) is turned off, the temperature sensor voltage value at that time is stored in the nonvolatile memory 21 (EEPROM) shown in FIG. The stored temperature sensor voltage value is used as a determination whether or not the temperature around the coupling 11 at the time when the IG is turned off is high when the IG is turned on next time.

  Specifically, as shown in the flowchart of FIG. 2, the ECU 12 first determines whether or not the ignition switch (IG) is off (step 101). If IG is off (step 101: YES), the temperature sensor voltage Vth is stored in the nonvolatile memory 21 (step 102, storage voltage, Vthm), and the process is terminated.

  Next, when IG is turned on, the temperature sensor voltage value Vthm stored at the time of IG off, the four-wheel wheel speed values Vfl, Vfr, Vrl, Vrr, and the temperature sensor voltage value used for the abnormality determination process are stored. Vth and temperature sensor voltage threshold 1Vths3 are taken in. The temperature sensor voltage value Vth stored at the time when the IG is turned off is used as a judgment as to whether or not the temperature around the coupling 11 at the time when the IG is turned off.

  The four-wheel wheel speed values Vfl, Vfr, Vrl, and Vrr are used to determine whether the vehicle is operating or stopped. When the vehicle is stopped, it is used to determine that the temperature around the coupling 11 is low. Further, when the temperature sensor voltage value Vth is smaller than the temperature sensor voltage threshold value 1Vths3, the temperature sensor voltage value Vth and the temperature sensor voltage threshold value 1Vths3 indicate that the temperature around the coupling 11 is abnormally high or the temperature sensor 18 and It is used to determine that the wiring or the like has a ground fault abnormality.

Next, when the temperature sensor voltage value Vth is smaller than the temperature sensor voltage threshold 1Vths3,
Whether the temperature sensor abnormality is high temperature abnormality or ground fault abnormality cannot be determined. In this case, a temperature estimation calculation is performed to determine whether there is a high temperature abnormality or a ground fault abnormality.
As the temperature estimation formula, for example, formula (1) of publicly known (Japanese Patent Laid-Open No. 2007-38798) is used.
H (n) = K1 × Σ (K2 × transmission torque × rotational speed−K3 × H (n−1)) (1)
In the above equation (1), H (n-1) is the previous calculation value, K1, K2, and K3 are constants, and the temperature H of each heat generation point is the K1, K2, and K3 at each heat generation point. It is estimated individually by calculating as a corresponding value. The “rotation speed” is obtained based on the front wheel speed Vf and the rear wheel speed Vr detected by the wheel speed sensors 17f and 17r.

  When the temperature estimation current value H (n) is equal to or higher than the temperature sensor estimated voltage threshold 2Vths4, it is determined that the temperature sensor is abnormally hot, the alarm lamp is turned on, and the driving force is distributed between the main driving wheel and the auxiliary driving wheel. The current value at the time of 4WD control, which is the control, is gradually reduced, and the control is switched to 2WD control, which is control for distributing the driving force only to the main drive wheels. Also, if the temperature estimate current value H (n) is smaller than the temperature sensor voltage threshold 2Vths4, it is determined that the temperature sensor ground fault is abnormal, the alarm lamp is turned on, and the current value during 4WD control is immediately cut off. Switch to 2WD control.

  More specifically, as shown in the flowcharts of FIGS. 3 and 4, when the engine 2, which is a driving source, is started (IG on) (step 201), the CPU 20 is stored in the nonvolatile memory 21 when the IG is off. The temperature sensor voltage (memory voltage, Vthm) is read (step 202). Subsequently, the four wheel speeds (Vfl, Vfr, Vrl, Vrr) are taken in (step 203). Further, the temperature sensor voltage (Vth) is captured (step 204).

  Next, the temperature sensor voltage threshold value 1Vths3 is taken in (step 205). Then, it is determined whether or not the temperature sensor voltage Vth is smaller than the temperature sensor voltage threshold value 1Vths3 (step 206). When the temperature sensor voltage Vth is smaller than the temperature sensor voltage threshold value 1Vths3 (Vth <Vths3, step 206: YES), it is determined whether or not the four-wheel wheel speed value is zero and the storage voltage Vthm is normal from IG on ( Step 207).

  If the four-wheel wheel speed value is zero and the stored voltage Vthm is not normal after IG is turned on (step 207: NO), it is determined whether or not the temperature sensor voltage Vth is smaller than the temperature sensor voltage threshold value 1Vths3 (step 207). 208). When the temperature sensor voltage Vth is smaller than the temperature sensor voltage threshold value 1Vths3 (Vth <Vths3, Step 208: YES), the temperature estimation current value H (n) is calculated from the temperature estimation formula (Step 209).

  Next, the temperature sensor estimated voltage threshold value 2Vths4 is fetched (step 210). Then, it is determined whether or not the temperature estimated current value H (n) is equal to or higher than the temperature sensor estimated voltage threshold value 2Vths4 (step 211).

  When the temperature estimation current value H (n) is equal to or higher than the temperature sensor estimated voltage threshold 2Vths4 (H (n) ≧ Vths4, Step 211: YES), it is determined that the temperature sensor is abnormally high (Step 212). The lamp is turned on as a high temperature abnormality alarm (step 213).

Next, the current value at the time of 4WD control is gradually decreased to switch to 2WD control, and 2WD control is executed (control means, step 214). Further, it is determined whether or not IG is off (step 215). If IG is off (step 215: YES), the process ends.
If IG is not off (step 215: NO), the process returns to step 208.

  If the temperature estimation current value H (n) is smaller than the temperature sensor estimated voltage threshold 2Vths4 (H (n) <Vths4, step 211: NO), it is determined that the temperature sensor ground fault is abnormal (step 216), and the temperature The lamp is turned on as a sensor ground fault alarm (step 217).

  Next, the current value at the time of 4WD control is immediately cut off, switching to 2WD control is performed, and 2WD control is executed (control means, step 218). Further, it is determined whether or not IG is off (step 215). If IG is off (step 215: YES), the process ends. If IG is not off (step 215: NO), the process returns to step 208.

When the temperature sensor voltage Vth is equal to or higher than the temperature sensor voltage threshold value 1Vths3 (Vth ≧ Vths3, step 208: NO), 4WD control is executed (step 219).
Next, when the four-wheel wheel speed is zero and the stored voltage Vthm is normal after IG is turned on (step 207: YES), it is determined that the temperature sensor ground fault is abnormal (step 216), and the temperature sensor ground fault abnormality alarm is detected. The lamp is turned on (step 217).

  Next, the current value at the time of 4WD control is immediately cut off, switching to 2WD control is performed, and 2WD control is executed (control means, step 218). Further, it is determined whether or not IG is off (step 215). If IG is off (step 215: YES), the process ends. If IG is not off (step 215: NO), the process returns to step 208.

As described above, according to this embodiment, the following operations and effects can be obtained.
As described above, if the output voltage of the temperature sensor is simply monitored, the temperature sensor high temperature abnormality and the temperature sensor ground fault abnormality occur at the same time when the temperature sensor output voltage is reduced. May be determined as a temperature sensor ground fault abnormality even when the temperature sensor becomes abnormal in high temperature. If it is determined that the temperature sensor ground fault is abnormal, the current during 4WD control is immediately cut off, and switching to 2WD control may result in unstable vehicle travel.

  In this regard, the CPU of this embodiment performs a temperature estimation calculation when a temperature sensor high temperature abnormality and a temperature sensor ground fault abnormality occur simultaneously in a state where the output voltage of the temperature sensor is lowered. Determine if there is an abnormality. That is, when the temperature sensor voltage estimated value calculated from the temperature estimation calculation is equal to or greater than the threshold, it is determined that the temperature sensor is abnormally high temperature, and when the temperature sensor voltage estimated value calculated from the temperature estimation calculation is smaller than the threshold, It can be determined that the temperature sensor ground fault is abnormal.

  With such a configuration, even when the temperature sensor originally becomes a high temperature abnormality, even if it is determined that the temperature sensor has a ground fault abnormality, or conversely, if the temperature sensor has a ground fault abnormality, Regardless, it can be prevented that the temperature sensor is determined to be abnormally hot.

  As a result, although the temperature sensor temperature should be smoothly switched to 2WD control by gradually decreasing the current value during 4WD control, it is determined that the temperature sensor ground fault is abnormal, and the current during 4WD control is Since the vehicle is immediately shut off and switched to 2WD control, it is possible to prevent the vehicle from becoming unstable.

In addition, you may change this embodiment as follows.
In the present embodiment, the present invention is embodied in a vehicle driving force distribution device having a front wheel as a main driving wheel, but may be embodied in a vehicle driving force distribution device having a rear wheel as a main driving wheel.

  -In this embodiment, although the temperature sensor was attached to the periphery of a torque coupling, the attachment position of a temperature sensor is not restricted to this, The thing which attached the temperature sensor in ECU may be used.

1: Vehicle, 2: Engine, 3: Transaxle, 4: Front axle,
5: Propeller shaft, 7: Pinion shaft, 8: Rear differential,
9: Rear axle, 10f: Front wheel, 10r: Rear wheel, 11: Torque coupling,
12: ECU, 13: driving force distribution device, 14: differential carrier,
15: electromagnetic clutch, 16: throttle opening sensor,
17fl, 17fr, 17rl, 17rr: Wheel speed sensor,
18: temperature sensor, 19: battery, 20: CPU,
21: Nonvolatile memory (EEPROM), 22: Filter, 23: Voltage divider,
A1: Positive terminal of temperature sensor, A2: Negative terminal of temperature sensor Ra: Throttle opening, V: Vehicle speed, Vfl, Vfr, Vrl, Vrr: Four-wheel wheel speed value,
Wdiff: Wheel speed difference, IG: Ignition switch,
Vth: temperature sensor voltage,
Vths1: Temperature sensor voltage high temperature abnormal threshold,
Vths2: Temperature sensor voltage ground fault abnormality threshold,
Vths3: Temperature sensor voltage threshold 1 Vths4: Temperature sensor estimated voltage threshold 2
Vthm: memory voltage,
H (n): Temperature estimation current value, H (n-1): Temperature estimation previous value,
V0: Voltage divided by the voltage divider, t0: Temperature sensor ground fault point,