JP2012126241A - Driving power distribution control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving power distribution control device capable of improving vehicle running stability by avoiding immediate switching from 4WD control to 2WD control, and maintaining 4WD performance even when a failure of a temperature sensor for measuring an ambient temperature of a switching element is detected while a vehicle is moving.SOLUTION: Even when a failure of a temperature sensor for measuring an ambient temperature of a switching element is detected, a PWM frequency for PWM control of a switching element is lowered and 4WD control is continued if the temperature detected by a temperature sensor for measuring a vehicle interior temperature is below a predetermined value.

Description

  The present invention relates to a driving force distribution control device.

  Conventionally, there is a driving force distribution control device capable of changing the driving force distribution between the main driving wheel and the auxiliary driving wheel. Many of these driving force distribution control 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 are The driving force distribution is controlled.

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.
The current applied to the electromagnetic coil can be excited and demagnetized by on / off control (PWM control) of the switching element (FET).
Thus, the clutch mechanism is connected by the excitation of the electromagnetic coil, and the control is switched to the control (4WD control) for distributing the driving force between the main driving wheel and the auxiliary driving wheel.

  In the PWM control of the FET, for example, when the vehicle is in an uphill state, a large current is applied to the electromagnetic coil in order to connect the clutch mechanism and perform 4WD control. If this climbing state continues for a long time, the temperature of the FET increases, and in the worst case, the FET may be burned out. In order to prevent such FET burnout, a temperature sensor is provided in the vicinity of the FET, and when the temperature measured by the temperature sensor exceeds a predetermined temperature, the relay that turns on and off the electromagnetic coil is turned off. Thus, a control for immediately stopping the current applied to the electromagnetic coil is performed. This prevents burning due to the temperature rise of the FET.

In such a driving force distribution control device, failure detection of the temperature sensor is performed. This failure detection of the temperature sensor is executed, for example, when an ignition switch (IG, power switch) is turned on or at a predetermined timing during traveling.
The temperature sensor failure includes a temperature sensor short-circuit failure in which the input terminal and the output terminal of the temperature sensor are short-circuited, and a substrate temperature sensor open failure in which the detection value of the temperature sensor is not output.

  When a temperature sensor failure is detected by such a temperature sensor failure detection, the temperature rise of the FET cannot be monitored, so the relay that turns on and off the electromagnetic coil is turned off (relay on prohibition process) The energization to the FET was immediately stopped. For this reason, the control is immediately switched from the control for distributing the driving force between the main driving wheel and the auxiliary driving wheel (4WD control) to the control for distributing the driving force only to the main driving wheel (2WD control).

As described above, when a failure of the temperature sensor that measures the ambient temperature of the switching element (FET) is detected, even when the vehicle is running, the relay is immediately turned on prohibition control to switch from 4WD control to 2WD control. Will be executed.
As a result, the performance as 4WD cannot be maintained, and the vehicle traveling may become unstable depending on the road surface condition.

  The present invention has been made to solve the above-described problems, and its purpose is to immediately detect a failure of a temperature sensor that measures the ambient temperature of a switching element (FET) while traveling. It is another object of the present invention to provide a driving force distribution control device that maintains the performance as 4WD without switching from 4WD control to 2WD control and improves the stability of vehicle travel.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided in a driving force transmission system of a vehicle and transmits from the input side to the output side according to the current supplied to the electromagnetic clutch mechanism (8). Torque coupling (7) for controlling the driving force distribution between the main driving wheel and the auxiliary driving wheel by changing the torque, and switching elements (FET, 35) for supplying current to the electromagnetic clutch mechanism (8) And a PWM control means (microcomputer, 30) for changing the driving force distribution by PWM control (microcomputer, 30) of the switching element (FET, 35), and a driving force distribution control device (ECU, 12). The temperature sensor 1 (36) for measuring the ambient temperature of the switching element (FET, 35), the temperature sensor 2 (13) for measuring the room temperature of the vehicle, and the temperature sensor 1 (36). Temperature sensor failure detection means (microcomputer, 30) for detecting a failure, the temperature sensor failure detection means (microcomputer, 30) detects a failure of the temperature sensor 1 (36), and the temperature sensor 2 (13) When the temperature measured in step (b) is equal to or lower than a predetermined value, the PWM frequency of the PWM control (microcomputer, 30) is lowered and the PWM control (microcomputer, 30) is continued.

  That is, even when a failure of the temperature sensor 1 that measures the ambient temperature of the switching element is detected, if the temperature sensor 2 that measures the room temperature of the vehicle is equal to or less than a predetermined value, the PWM control means that changes the driving force distribution The PWM frequency of the PWM control of the switching element is lowered.

  According to the above configuration, even when a failure of the temperature sensor 1 that measures the ambient temperature of the switching element is detected, if the temperature measured by the temperature sensor 2 that measures the room temperature of the vehicle is equal to or less than a predetermined value, the PWM Since the PWM frequency of control can be lowered and 4WD control can be continued, the stability of vehicle travel can be improved.

  According to the present invention, even when a failure of the temperature sensor that measures the ambient temperature of the switching element is detected during traveling, the performance as 4WD can be maintained without immediately switching from 4WD control to 2WD control. In addition, it is possible to provide a driving force distribution control device with improved vehicle running stability.

The schematic block diagram of the four-wheel drive vehicle in this embodiment. The block diagram which shows the electrical connection of the drive transmission apparatus in this embodiment. The flowchart figure which shows the process sequence of substrate temperature sensor abnormality in this embodiment. The map which determines PWM frequency (low frequency) f0 in this embodiment.

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 four-wheel drive vehicle 1 includes an engine 2 and a transaxle 3 which are internal combustion engines. A pair of front axles 4 and 4 and a propeller shaft 5 are connected to the transaxle 3. Front wheels 6 and 6 as main drive wheels are connected to both front axles 4 and 4 respectively. A torque coupling 7 is connected to the propeller shaft 5, and a rear differential 9 is connected to the torque coupling 7 via a drive pinion shaft (not shown). The rear differential 9 is connected to both rear wheels 11 and 11 as auxiliary drive wheels via a pair of rear axles 10 and 10.

  The driving force of the engine 2 is transmitted to both front wheels 6 and 6 via the transaxle 3 and both front axles 4 and 4. In addition, when the propeller shaft 5 and the drive pinion shaft are coupled so that torque can be transmitted by the torque coupling 7, the driving force of the engine 2 is the propeller shaft 5, the drive pinion shaft, the rear differential 9, and the rear axles 10, 10. Is transmitted to both rear wheels 11, 11. The driving force of the engine 2 rotates a generator (not shown) and supplies power to the battery 20 (see FIG. 2).

  The torque coupling 7 includes a wet multi-plate electromagnetic clutch mechanism 8, and the electromagnetic clutch mechanism 8 has a plurality of clutch plates (not shown) that are frictionally engaged with or separated from each other. When a driving force distribution control device (ECU) 12 supplies a current corresponding to a current command value to an electromagnetic coil L0 (see FIG. 2) built in the electromagnetic clutch mechanism 8, the clutch plates are frictionally engaged with each other, Torque is transmitted to the rear wheel 11 to achieve 4WD control that distributes the driving force between the main driving wheel and the auxiliary driving wheel. When the ECU 12 cuts off the supply of current according to the current command value to the electromagnetic clutch mechanism 8, the clutch plates are separated from each other, the transmission of torque in the rear wheels 11 is also cut off, and the front wheels that distribute the driving force only to the main driving wheels. Drive (2WD control).

  Further, the frictional engagement force of each clutch plate increases or decreases in accordance with the amount of current (the strength of the current) corresponding to the current command value supplied to the electromagnetic coil L0 of the electromagnetic clutch mechanism 8, thereby transmitting to the rear wheel 11. The torque, that is, the restraining force on the rear wheel 11 (friction engagement force of the electromagnetic clutch mechanism 8) can be arbitrarily adjusted. As a result, the ECU 12 selects either 4WD control or 2WD control, and controls the driving force distribution rate (torque distribution rate) between the front and rear wheels 6 and 11 in the 4WD control. In the present embodiment, a vehicle interior temperature sensor 13 that measures the vehicle interior temperature is provided in the vehicle interior, and is connected to the ECU 12.

Next, the electrical configuration of the ECU 12 of the torque coupling 7 will be described with reference to FIG.
The ECU 12 is configured around a microcomputer 30 having a CPU, a RAM, a ROM, an I / O interface, and the like. The ROM stores various control programs executed by the ECU 12, various data, various maps, and the like. The map is obtained in advance by experimental data based on a vehicle model and well-known theoretical calculations. The RAM is a data work area for the CPU to execute various arithmetic processes by developing a control program including a relay failure detection program written in the ROM.

  Each wheel speed sensor (not shown) and throttle opening sensor (not shown) are connected to the input side of the ECU 12 (input terminal of the I / O interface). A torque coupling 7 and an engine control device (not shown) are connected to the output side of the ECU 12 (output terminal of the I / O interface).

  The wheel speed sensor is provided for each of the wheels 6 and 11 and detects the speed of each of the wheels 6 and 11 (hereinafter referred to as wheel speed). The throttle opening sensor is connected to a throttle valve (not shown), and detects the opening degree of the throttle valve, that is, the depression amount of the driver's accelerator pedal (not shown). Then, the microcomputer 30 of the ECU 12 determines whether or not the vehicle is in steady running based on detection signals from the sensors and calculates a current command value to be supplied to the electromagnetic clutch mechanism 8.

  As shown in FIG. 2, a series circuit of a fuse 21, a relay 31, a coil L of a noise removal filter 32, an electromagnetic coil L <b> 0, and an FET 35 is connected to the battery 20. The other end of the capacitor C, one of which is grounded, is connected to the connection point between the coil L and the electromagnetic coil L0. The capacitor C and the coil L constitute a noise removal filter 32. A flywheel diode 34 is connected to both ends of the electromagnetic coil L0.

  An ignition switch (IG) 22 as a power switch supplies the power of the battery 20 to the microcomputer 30. When the IG 22 is turned on and electric power is supplied, the microcomputer 30 processes various control programs.

  The microcomputer 30 outputs the current command value to a drive circuit 33 as PWM control means. The drive circuit 33 performs on / off control (PWM control) of the FET 35 to control the amount of current supplied to the electromagnetic coil L0 of the electromagnetic clutch mechanism 8 in accordance with the current command value. As a result, by controlling the amount of current corresponding to the current command value supplied to the electromagnetic coil L0 of the electromagnetic clutch mechanism 8, the driving force distribution between the front wheel side and the rear wheel side is changed. In the present embodiment, a substrate temperature sensor 36 that measures the ambient temperature of the FET 35 of the ECU 12 is provided in the ECU 12.

  Next, the operation of the ECU 12 of the four-wheel drive vehicle configured as described above will be described with reference to FIG. FIG. 3 is a flowchart of the substrate temperature sensor abnormality detection program executed in the ECU 12 when the IG 22 is turned on.

A control method of this embodiment will be described.
In the control of the present embodiment, first, it is determined whether or not the abnormality of the substrate temperature sensor 36 is stored in the nonvolatile memory (EEPROM) 23. This is because when the substrate temperature sensor abnormality indicating that the substrate temperature sensor 36 is abnormal is stored in the EEPROM 23, the vehicle interior temperature sensor 13 that measures the vehicle indoor temperature, not the substrate temperature sensor 36 of the FET 35. Change to temperature measurement by. When the vehicle interior temperature measured by the vehicle interior temperature sensor 13 is low, 4WD control, which is control for distributing the driving force between the main drive wheels and the auxiliary drive wheels, is continued.

However, when the temperature of the vehicle interior temperature sensor 13 is used as the temperature of the FET 35 on the substrate, there is a large difference between the temperature measured by the vehicle interior temperature sensor 13 and the temperature of the FET 35.
Therefore, when the 4WD control is continued, the PWM frequency f of PWM control having a large contribution to the temperature rise of the FET 35 is changed to the PWM frequency (low frequency) f0 so that the temperature of the FET 35 does not rise greatly.

  On the other hand, if the vehicle interior temperature measured by the vehicle interior temperature sensor 13 is high, the FET 35 may burn out if the current continues to flow further through the FET. Therefore, the PWM control for the FET 35 is stopped, and the main drive wheel The 4WD control that distributes the driving force of the auxiliary driving wheel is switched to 2WD control that is a control that distributes the driving force only to the main driving wheel.

  Further, when the substrate temperature sensor abnormality is not stored in the EEPROM 23, the temperature sensor failure detection means determines whether or not the substrate temperature sensor is abnormal. If the substrate temperature sensor 36 is not abnormal, the PWM frequency f is not changed and the 4WD control is continued with the current PWM frequency (high frequency). If the substrate temperature sensor 36 is abnormal, the EEPROM 23 stores the substrate temperature sensor abnormality.

  More specifically, as shown in the flowchart of FIG. 3, the CPU 20 determines whether or not the substrate temperature sensor abnormality is stored in the EEPROM 23 (step 101). When the substrate temperature sensor abnormality is stored in the EEPROM 23 (FLG1 = 1, step 101: YES), it is determined whether or not the vehicle interior temperature Tr detected by the vehicle interior temperature sensor 13 is smaller than the threshold value Trs (step). 102).

  When the vehicle interior temperature Tr detected by the vehicle interior temperature sensor 13 is smaller than the threshold value Trs (Tr <Trs, Step 102: YES), the routine proceeds to Step 103, where the PWM frequency (low frequency) f0 is mapped (FIG. 4). Take in from reference, described later. Next, the process proceeds to step 104, where the PWM frequency f is changed to the PWM frequency (low frequency) f0, and the process ends.

  On the other hand, when the vehicle interior temperature Tr detected by the vehicle interior temperature sensor 13 is equal to or higher than the threshold value Trs (Tr ≧ Trs, Step 102: NO), the process proceeds to Step 105, and the PWM control is stopped. In other words, the 4WD control, which is the control for distributing the driving force between the main driving wheel and the auxiliary driving wheel, is switched to the 2WD control, which is a control for distributing the driving force only to the main driving wheel.

In step 101, if the substrate temperature sensor abnormality is not stored in the EEPROM 21 (FLG1 = 0, step 101: NO), it is determined whether or not the substrate temperature sensor 36 is abnormal (step 106). If the substrate temperature sensor 36 is abnormal (step 106: YES), the process proceeds to step 107, and the substrate temperature sensor abnormality is written in the EEPROM 21 (FLG1 = 1). And it returns to step 101 and repeats the same process.
On the other hand, if the substrate temperature sensor 36 is not abnormal (step 106: NO), the process is terminated.

Next, a PWM frequency (low frequency) f0 determination method will be described with reference to FIG. The horizontal axis of the map shown in FIG. 4 indicates the PWM frequency f. The vertical axis indicates the junction temperature of the FET 35 (the temperature of the connection portion between the lead wire inside the FET and the member constituting the FET element).
A method for obtaining the line L1 (experimental value) of this map will be described. First, assuming that the vehicle is in an uphill state, the load condition is that the PWM frequency on the horizontal axis is gradually increased and the surface temperature of the FET 35 is measured. However, since the junction temperature is not the surface temperature, it is obtained by calculation from the heat loss (calculation) and the thermal resistance (FET data) and plotted.

  The allowable junction temperature t0 of the FET 35 is determined in consideration of the heat dissipation effect of the heat sink of the FET 35. Next, an intersection point Q is obtained by drawing a line from the junction temperature t0 of the FET 35 to the line L1, and a PWM frequency (low frequency) f0 obtained by perpendicularly drawing from the intersection point Q is obtained. This PWM frequency (low frequency) f 0 is used in step 104.

  As described above, according to the present embodiment, even when a failure of the substrate temperature sensor 36 that measures the ambient temperature of the FET 35 is detected, the performance as 4WD can be maintained without immediately switching from 4WD control to 2WD control. Therefore, it is possible to provide a driving force distribution control device with improved vehicle running stability.

  Further, when the temperature of the vehicle interior temperature sensor 13 is used as the temperature of the FET 35 on the substrate, an error occurs between the temperature of the vehicle interior temperature sensor 13 for measuring the vehicle interior temperature and the ambient temperature of the FET 35. The PWM frequency that causes the temperature rise of the FET 35 is lowered to suppress the temperature rise of the FET 35.

  As a result, even when a failure in the vehicle interior temperature sensor 13 that measures the ambient temperature of the FET 35 is detected, if the temperature detected by the vehicle interior temperature sensor 13 that measures the vehicle interior temperature is equal to or less than a predetermined value, the PWM Since PWM control, that is, 4WD control can be continued by lowering the PWM frequency of control, the stability of vehicle travel can be improved.

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 the present embodiment, when the vehicle interior temperature Tr is lower than the threshold value Trs, the PWM frequency is immediately changed to the PWM frequency (low frequency) f0 and the 4WD control is continued. Instead, the PWM frequency may be gradually decreased as the vehicle interior temperature Tr increases.

  -In this embodiment, the temperature sensor is installed in the passenger compartment, but the position of the temperature sensor is not limited to this, and the temperature estimated from the intake air temperature sensor provided in the intake pipe of the engine is used. Also good.

1: Four-wheel drive vehicle, 2: Engine, 3: Transaxle, 4: Front axle,
5: Propeller shaft, 6: Front wheel, 7: Torque coupling, 8: Electromagnetic clutch mechanism, 9: Rear differential, 10: Rear axle, 11: Rear wheel,
12: Driving force distribution control device (ECU), 13: Interior temperature sensor,
20: battery, 21: fuse, 22: ignition switch (IG),
23: non-volatile memory (EEPROM), 30: microcomputer, 31: relay,
32: Noise removal filter, 33: Drive circuit, 34: Flywheel diode,
35: switching element (FET), 36: substrate temperature sensor, L0: electromagnetic coil,
Tr: passenger compartment temperature, Trs: threshold,
f: PWM frequency, f0: PWM frequency (low frequency), t0: junction temperature,
FLG1: Substrate temperature sensor abnormality memory confirmation flag

Claims (1)

It is provided in the vehicle's driving force transmission system and changes the transmission torque transmitted from the input side to the output side according to the current supplied to the electromagnetic clutch mechanism, thereby distributing the driving force between the main driving wheel and the auxiliary driving wheel. Torque coupling to control,
A switching element for supplying a current to the electromagnetic clutch mechanism;
In a driving force distribution control device comprising PWM control means for changing the driving force distribution by PWM controlling the switching element,
A temperature sensor 1 for measuring the ambient temperature of the switching element;
A temperature sensor 2 for measuring a room temperature of the vehicle;
A temperature sensor failure detection means for detecting a failure of the temperature sensor 1;
When the temperature sensor failure detection means detects a failure of the temperature sensor 1 and the temperature measured by the temperature sensor 2 is equal to or lower than a predetermined value, the PWM frequency of the PWM control is lowered and the PWM control is continued. thing,
A driving force distribution control device characterized by the above.

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