JP4207457B2 - Front and rear wheel torque distribution control device for four-wheel drive vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of a front and rear wheel torque distribution control device applied to a four-wheel drive vehicle that variably controls drive torque distribution to front and rear wheels by controlling the engagement torque of a control clutch.
[0002]
[Prior art]
Conventionally, in a four-wheel drive vehicle having an electronically controlled clutch that controls the distribution of torque transmitted to the front and rear wheels, when the drive torque is transmitted from the drive wheel to the driven wheel, Those that activate protection control are known.
[0003]
Among these electronically controlled clutches, like a hydraulic clutch (see Japanese Patent Application Laid-Open No. 04-103433, etc.) that is fastened by a control hydraulic pressure created by an electromagnetic valve employed in a four-wheel drive vehicle based on a rear wheel drive vehicle When a large driving force distribution actuator is used, the drive torque has a margin with respect to the clutch transmission limit torque. Don't be.
[0004]
[Problems to be solved by the invention]
However, when a torque that exceeds a certain value continues for a certain period of time, the protection control operation starts. For example, when using a small and lightweight driving force distribution actuator, such as an electromagnetic clutch that is engaged using a solenoid force. In this case, the drive torque has no margin with respect to the transmission limit torque of the clutch, and as described below, control in consideration of protection by temperature assurance of the electromagnetic clutch is required.
[0005]
In particular, when an electromagnetic clutch is used in a drive system such as a sports utility vehicle (SUV), driving torque transmission in the limit torque range of the electromagnetic clutch in a driving scene that runs through low μ roads such as deserts and snowy roads. Must be done frequently.
[0006]
(1) When the torque threshold value for protection control is set to a small value, the protection control is activated when a small torque continues for a certain time or longer. Nevertheless, protection control is entered early. Therefore, the driving torque cannot be sufficiently transmitted due to excessive control over protection by temperature guarantee.
[0007]
(2) When the torque threshold value for protection control is set to a large value, the protection control is activated when a large torque continues for a certain time or more, so the timing for entering protection control is delayed. .
[0008]
(3) Since the estimated clutch temperature is reset when the command torque falls below a certain value, the estimated clutch temperature is reset when the command torque falls below the threshold value. If the situation where the command torque exceeds the threshold value immediately after that and the command torque falls below the threshold value immediately after that is repeated, the temperature will not fall between the actual clutch temperature and the estimated clutch temperature. A big divergence occurs.
[0009]
(4) As protection control by guaranteeing the temperature of the control clutch, when the mode is automatically switched to the engagement mode (= LOCK mode) in which the control clutch is strongly engaged, the current command value when switching to the LOCK mode with the mode selector switch When the same current value is applied to the control clutch, clutch slippage occurs due to the temperature effect of the control clutch, and the protection function of the control clutch may not be achieved. That is, the friction coefficient of the friction material of the control clutch decreases when the temperature becomes high, and in addition, when the solenoid becomes high temperature, the electric current increases and the flowing current decreases.
[0010]
The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to travel with frequent transmission of torque in the limit region while ensuring the improvement of the durability of the drive system provided with the control clutch. An object of the present invention is to provide a front and rear wheel torque distribution control device for a four-wheel drive vehicle that can reliably achieve clutch protection by preventing slippage of a control clutch in a scene.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, in a four-wheel drive vehicle having a control clutch for controlling torque distribution transmitted from a drive source to front and rear wheels,
The input energy applied to the control clutch is calculated based on the clutch rotational speed difference and the clutch transmission torque, and the fluctuation of the clutch temperature that rises or falls over time is predicted according to the calculated magnitude of the input energy. When the estimated clutch temperature calculated based on the temperature fluctuation prediction is equal to or higher than the clutch protection judgment temperature, it automatically switches to an engagement mode that suppresses slippage of the control clutch, and the command current value to the control clutch is engaged by driver selection. Clutch protection control means for setting the current value higher than the current value when switching to the mode is provided.
[0012]
Here, the setting to “high current value” may be set to a fixed current value obtained by adding a constant current value to the current value when switching to the fastening mode by driver selection, or fastening by driver selection. A variable current value obtained by adding a correction current value according to the estimated clutch temperature to the current value when switching to the mode may be set.
[0013]
"Clutch protection control means", TightenIf the estimated clutch temperature rises despite automatic switching to the engagement mode, the clutch protection control is performed by “automatic switching to engagement mode” + “control clutch release”.The.
[0014]
【The invention's effect】
In the present invention, if a high current value is always applied, including the case of the fastening mode by selection operation, the durability of the drive system is affected, so when the mode is switched to the fastening mode by driver selection. Keeps the current value low. By applying a high current value only when the estimated clutch temperature needs to be equal to or higher than the clutch protection judgment temperature, the temperature effect of the control clutch (decrease in friction coefficient and solenoid current) is eliminated, and the control clutch is engaged without slipping. Is secured.
[0015]
Therefore, it is possible to reliably achieve clutch protection by preventing slippage of the control clutch in a traveling scene where torque transmission in the limit region is frequently performed while ensuring improvement in durability of the drive system provided with the control clutch. it can.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment for realizing a front and rear wheel torque distribution control device for a four-wheel drive vehicle according to the present invention will be described with reference to the drawings..
[0017]
(referenceExample)
First, the configuration will be described. Figure 1reference1 is an overall system diagram showing a front and rear wheel torque distribution control device of a four-wheel drive vehicle in an example, wherein 1 is an engine, 2 is a transmission, 3 is a front differential, 4 and 5 are front side drive shafts, and 6 and 7 are left and right front wheels. , 8 is a transfer, 9 is a propeller shaft, 10 is an electromagnetic clutch (control clutch), 11 is a rear differential, 12 and 13 are rear drive shafts, and 14 and 15 are left and right rear wheels.
[0018]
That is, based on an FF vehicle (front engine / front drive vehicle) that transmits the drive torque that has passed through the engine and transmission 2 to the front wheels 6 and 7, the engine drive torque is applied to the rear wheels 14 and 15 via the electromagnetic clutch 10. The driving force distribution ratio (%) is a front wheel driving distribution ratio of front wheels: rear wheels = 100: 0 (%) when the electromagnetic clutch 10 is in the engaged and released state. When the electromagnetic clutch 10 is in the fully engaged state, the front wheel: rear wheel = 50: 50 (%) front / rear wheel distribution ratio, and the rear wheel distribution ratio is 0% to 50% depending on the degree of engagement of the electromagnetic clutch 10. Controlled in stages.
[0019]
The electromagnetic clutch 10 is controlled by a drive current from the 4WD controller 16, and the 4WD controller 16 includes a mode switch signal from the mode changeover switch 17, an engine speed signal from the engine speed sensor 18, and an accelerator opening. Accelerator opening signal from sensor 19, left front wheel speed signal from left front wheel speed sensor 20, right front wheel speed signal from right front wheel speed sensor 21, and left rear wheel speed signal from left rear wheel speed sensor 22 The right rear wheel speed signal from the right rear wheel speed sensor 23 is input, and the 4WD controller 16 outputs a drive current to the solenoid 24 of the electromagnetic clutch 10 and also outputs a display command to the indicator 25. A lighting warning command is output to the warning light & alarm 26.
[0020]
FIG. 2 is a schematic view showing the electromagnetic clutch 10, and FIG. 3 is a perspective view and an operation explanatory view showing a cam mechanism of the electromagnetic clutch 10.
2 and 3, 24 is a solenoid, 27 is a clutch input shaft, 28 is a clutch output shaft, 29 is a clutch housing, 30 is an armature, 31 is a control clutch, 32 is a control cam, 33 is a main cam, 34 is a ball, 35 is a main clutch, and 36 is a cam groove.
[0021]
The clutch input shaft 27 has one end connected to the propeller shaft 9, the other end fixed to the clutch housing 29, and the clutch output shaft 28 fixed to the input gear of the rear differential 11.
[0022]
The control clutch 31 is a clutch interposed between the clutch housing 29 and the control cam 32, and the main clutch 35 is a clutch interposed between the clutch housing 29 and the clutch output shaft 28.
[0023]
As shown in FIG. 3, a cam mechanism is constituted by the control cam 32, the main cam 33, and the balls 34 sandwiched between the cam grooves 36 and 36 formed in the both cams 32 and 33.
[0024]
Here, the fastening operation of the electromagnetic clutch 10 will be described.
First, when a current is passed through the solenoid 24 according to a command from the 4WD controller 16, a magnetic field is generated around the solenoid 24, and the armature 30 is drawn toward the control clutch 31 side. The friction torque generated by the control arm 31 is pushed by the attracted armature 30 and the friction torque generated by the control clutch 31 is transmitted to the control cam 32 of the cam mechanism. The torque transmitted to the control cam 32 is amplified and converted into torque in the axial direction via the cam grooves 36 and 36 and the ball 34, and presses the main cam 33 in the front direction. The main cam 33 pushes the main clutch 35, and a friction torque proportional to the current value is generated in the main clutch 35. Torque generated in the main clutch 35 passes through the clutch output shaft 28 and is transmitted to the rear differential 11 as drive torque.
[0025]
Next, the operation will be described.
[0026]
[Calculation of input energy]
FIG. 4A is a flowchart showing the flow of input energy calculation processing executed by the 4WD controller 16, and each step will be described below (corresponding to input energy calculation means).
[0027]
In step S1, the left front wheel speed VFL from the left front wheel speed sensor 20, the right front wheel speed VFR from the right front wheel speed sensor 21, the left rear wheel speed VRL from the left rear wheel speed sensor 22, and the right rear wheel speed sensor. The right rear wheel speed VRR from 23 and the drive current A output from the 4WD controller 16 to the solenoid 24 are read every 20 msec.
[0028]
In step S2, the unit input energy En is calculated by multiplying the clutch transmission torque TE and the front and rear wheel rotational speed difference ΔV (clutch rotational speed difference).
[0029]
Here, the clutch transmission torque TE is calculated by a function f (A) using the drive current A (clutch transmission torque estimating means).
[0030]
Further, the front-rear wheel rotational speed difference ΔV is calculated from the difference between the left and right front wheel speed average value and the left and right rear wheel speed average value (clutch rotation speed difference detecting means).
[0031]
In step S3, the unit input energy En calculated in step S2 is written in the memory (RAM).
[0032]
In step S4, 1 is added to the count value N to obtain N + 1.
[0033]
In step S5, it is determined whether or not the count value N is greater than or equal to a set count value N0 (for example, 32). If NO, the process returns to step S1, and if YES, the process proceeds to step S6.
[0034]
In step S6, the count value N is cleared to N = 0.
[0035]
In step S7, the input energy E is calculated by calculating the average value of the unit input energy En stored in memory. That is, when the set count value N0 is 32, the input energy E is an average value of the unit input energy En for 640 msec (= 20 msec × 32) (see FIG. 7).
[0036]
[Clutch protection control processing]
FIG. 4B is a flowchart showing the flow of the clutch protection control process executed by the 4WD controller 16, and each step will be described below. This process is executed at 640 msec / routine.
[0037]
In step S10, the input energy E and the vehicle speed V obtained in the flowchart of FIG.
[0038]
In step S11, it is determined whether or not the vehicle speed V is equal to or higher than the set vehicle speed VO. If YES, the process proceeds to step S12, the estimated clutch temperature T1 is set to the initial temperature T0, and the calculation of the estimated clutch temperature T1 is stopped and initial. Reset to state. Here, the set vehicle speed V0 is determined by an upper limit vehicle speed value that allows estimation of the clutch temperature. If NO in step S11, the process proceeds to step S13.
[0039]
In step S13, it is determined whether or not the input energy E is equal to or greater than the addition determination reference value E0. If YES, the process proceeds to the temperature rise side estimation process in steps S14 to S17, and if NO, the process proceeds from step S18 to step S21. The process proceeds to temperature decrease side estimation processing. Here, the addition determination reference value E0 is set as a determination threshold value of the input energy E in which the heat generation amount and the heat dissipation amount are substantially the same, and the clutch temperature becomes a substantially constant temperature. It shall be given as a value.
[0040]
In step S14, the temporary temperature increase ΔT1up obtained by converting the increase amount (= E−E0) of the input energy E with respect to the addition determination reference value E0 into the temperature increase amount is used as the estimated clutch temperature T1 (initial temperature T0 at the first estimation). ) And the provisional clutch estimated temperature T1z at that time is calculated.
[0041]
In step S15, the temperature increase coefficient Kup is set by the provisional clutch estimated temperature T1z at that time. That is, as shown in FIG. 5, when the provisional clutch estimated temperature T1z at that time is in the practical travel temperature range, the temperature increase coefficient Kup1 is gentler than the actual temperature gradient, and the clutch estimated temperature T1 at that time is in the high load temperature range. In some cases, the temperature rise coefficient Kup2 is steeper than the actual temperature gradient.
[0042]
In step S16, the temperature increase ΔTup is calculated from the product of the temperature increase coefficient Kup set in step S15 and the provisional temperature increase ΔT1up.
[0043]
In step S17, the current estimated clutch temperature T1n is calculated by adding the temperature increase amount ΔTup to the previous estimated clutch temperature T1.
[0044]
In step S18, the reduction amount of the input energy E with respect to the addition determination reference value E0 is set to a constant value, and the temporary temperature decrease amount ΔT1dn obtained by converting the constant value into the temperature decrease amount is set as the estimated clutch temperature T1 (initial value at the time of initial estimation). The provisional clutch estimated temperature T1z at that time is calculated by subtracting from the temperature T0).
[0045]
In step S19, the temperature decrease coefficient Kdn is set by the provisional clutch estimated temperature T1z at that time. That is, as shown in FIG. 5, when the estimated temporary clutch temperature T1z at that time is in the practical travel temperature range, the temperature drop coefficient Kdn1 is steeper than the actual temperature gradient, and the estimated clutch temperature T1 at that time is the high load temperature range. Is set to a temperature drop coefficient Kdn2 that is gentler than the actual temperature gradient.
[0046]
In step S20, the temperature decrease amount ΔTdn is calculated from the product of the temperature decrease coefficient Kdn set in step S19 and the provisional temperature decrease amount ΔT1dn (a constant value).
[0047]
In step S21, the current estimated clutch temperature T1n is calculated by subtracting the temperature decrease amount ΔTdn from the previous estimated clutch temperature T1.
[0048]
Steps S10 to S21 correspond to clutch estimated temperature calculation means.
[0049]
In step S22, it is determined whether or not the estimated clutch temperature T1n calculated in step S17 or step S21 is equal to or higher than the clutch protection determination temperature Tp. If NO, the process proceeds to END. If YES, the clutch after step S23 is determined. Transition to protection processing.
[0050]
In step S23, it is determined whether or not the mode selected by the mode changeover switch 17 is the AUTO mode (a mode in which the four-wheel engagement torque distribution is automatically switched according to the running state). If selected), the process proceeds to step S25, and if YES, the process proceeds to step S24.
[0051]
In step S24, the AUTO mode is automatically switched to the LOCK mode (four-wheel engagement torque fixing mode), and the process proceeds to step S25.
[0052]
In step S25, a required engagement torque Ta when the estimated clutch temperature T1n becomes equal to or higher than a predetermined value is set, and a fixed command current Ib for obtaining the required engagement torque Ta in a high temperature state is applied to the solenoid 24 of the electromagnetic clutch 10. .
[0053]
That is, as shown in FIG. 6, when the mode selected by the mode changeover switch 17 is the LOCK mode, the command current Ia for obtaining the required engagement torque Ta at normal temperature (for example, 50 ° C.) is supplied to the electromagnetic clutch 10. In contrast to being applied to the solenoid 24, a fixed command current Ib (= Ia + ΔI) that provides a required fastening torque Ta at a high temperature (for example, 140 ° C.) is applied to the solenoid 24 of the electromagnetic clutch 10.
[0054]
MaIn step S25, in order to notify the driver that clutch protection control is being performed, lamp lighting and an alarm may be used together (FIG. 7).
[0055]
[Electromagnetic clutch temperature estimation]
For example, when driving through a desert or the like, the relative rotational speed difference between the input and output shafts of the electromagnetic clutch 10 is calculated by the front and rear wheel rotational speed difference ΔV in step S2 of FIG. The transmitted clutch transmission torque TE is estimated based on the drive current A, and the unit input energy En applied to the electromagnetic clutch 7 is calculated by multiplying the clutch transmission torque TE and the front and rear wheel rotational speed difference ΔV, and step S7. The input energy E is calculated by calculating the average value of the unit input energy En stored.
[0056]
In the flowchart of FIG. 4 (b), a change in the clutch temperature that rises or falls with the passage of time is predicted according to the calculated magnitude of the input energy E. Based on this temperature fluctuation prediction, a step is performed. In S17 or step S21, the current estimated clutch temperature T1n is calculated.
[0057]
That is, as shown in the energy (ENERGY) of FIG. 7, 32 unit input energies are calculated every 20 msec, the input energy E is calculated by the average value of the unit input energies for 640 msec, and the temperature adjustment in FIG. As shown in the determination, the magnitude of the input energy E is such that the estimated temperature is increased when the input energy E is equal to or greater than the addition determination reference value E0, and the estimated temperature is decreased when the input energy E is less than the addition determination reference value E0. Is used to calculate the estimated clutch temperature.
[0058]
Therefore, since the method of estimating the clutch temperature by comparing the input energy E with the addition judgment reference value E0 determined by the temperature characteristic unique to the clutch is adopted, the fine influence of the heat balance can be ignored.
[0059]
Further, in estimating the clutch temperature, as shown in FIG. 5, when the estimated temporary clutch temperature T1z at that time is in the practical travel temperature range, the temperature rise coefficient Kup1 which is looser than the actual temperature gradient and the steeper than the actual temperature gradient. If the provisional clutch estimated temperature T1z at that time is in the high load temperature range, the temperature increase coefficient Kup2 is steeper than the actual temperature gradient and the temperature decrease coefficient Kdn2 is gentler than the actual temperature gradient.
[0060]
For this reason, when the temporary clutch estimated temperature T1z is in the high load temperature range when traveling on sandy roads or deep snow roads, the estimated temperature is higher than the actual temperature gradient by the temperature rise coefficient Kup2, and the actual temperature By setting the temperature decrease coefficient Kdn2 to be gentler than the gradient, the estimated temperature drop can be suppressed to a small level, so that the clutch temperature is estimated more strictly than in the vicinity of the limit use range.
[0061]
On the other hand, when the provisional clutch estimated temperature T1z is in the practical travel temperature range during normal travel, etc., the estimated temperature is continued to the estimated temperature in the high load temperature range with a temperature increase coefficient Kup1 that is gentler than the actual temperature gradient. Since the estimated temperature is lowered in the reset direction earlier by setting the temperature drop coefficient Kdn1 that is steeper than the actual temperature gradient, the clutch in the practical running temperature range that occurs due to the spread of the error between the estimated temperature and the actual temperature It is possible to prevent malfunction of the protection control.
[0062]
[Protection control action of electromagnetic clutch]
As described above, when the current estimated clutch temperature T1n is calculated accurately in step S17 or step S21 without using a temperature sensor, the calculated current estimated clutch temperature T1n is converted to clutch protection in the next step S22. It is determined whether the temperature is equal to or higher than the determination temperature Tp.
[0063]
When the temperature of the electromagnetic clutch 10 rises due to torque transmission accompanied by slipping in a low μ road traveling scene or the like, and it is determined in step S22 that the current estimated clutch temperature T1n calculated is equal to or higher than the clutch protection determination temperature Tp, As clutch protection control for lowering the temperature, in step S24, the mode is automatically switched from the AUTO mode to the LOCK mode. In step S25, the electromagnetic clutch 10 is strongly engaged by the fixed command current Ib.
[0064]
That is, FIG. 6 is a characteristic showing the relationship of the fastening torque T with respect to the command current I of the electromagnetic clutch 10, and in FIG.
Ta: Fastening torque upper limit value in AUTO mode (= Fastening value when LOCK mode is selected)
Tb: Engagement torque converted to normal temperature at high temperature command current Ib of electromagnetic clutch 10
Ta ': The engagement torque when the electromagnetic clutch 10 is at a high temperature when the command current is Ia
Ia: Upper limit of AUTO mode current at room temperature (= Current value when LOCK mode is selected)
Ib: Current value in LOCK mode for clutch protection control (= Ia + △ I)
It is.
[0065]
If a sudden start or the like is repeated in a scene traveling on a slippery road surface, a high load is continuously applied to the electromagnetic clutch 10, so that the clutch temperature rises and control for protecting the electromagnetic clutch 10 works. As this clutch protection control, even if the command current Ia is applied after switching from the AUTO mode to the LOCK mode, the engagement torque T decreases from Ta to Ta ′ at high temperatures compared to the engagement torque Ta at normal temperature. In the engine, slip occurs in the electromagnetic clutch 10 and the clutch temperature rises.
[0066]
On the other hand, by increasing the command current I from Ia to Ib at a high temperature, the fastening torque Ta for the command current Ia at the normal temperature can be secured.
In addition, even if the command current is the same, the fastening torque T is reduced when the electromagnetic clutch 10 becomes high temperature.
(1) When the friction material (the control clutch 31 and the main clutch 35) in the clutch portion in the electromagnetic clutch 10 becomes high temperature, the friction coefficient decreases.
(2) When the solenoid 24 in the electromagnetic clutch 10 reaches a high temperature, the electrical resistance increases and the actual current value decreases.
Is caused.
[0067]
On the other hand, there is a proposal that the fixed current value Ib is applied even in the LOCK mode by the selection operation to the mode switch 17 as in the LOCK mode at a high temperature. In this case, even in a large torque engine, it is possible to prevent the electromagnetic clutch 10 from slipping at a high temperature.
[0068]
However, if the fastening torque of the electromagnetic clutch 10 is increased in a situation where the temperature of the electromagnetic clutch 10 is not increased, the fastening torque Tb converted to room temperature with the fixed command current Ib corresponding to the high temperature of the electromagnetic clutch 10 is driven. As a result, the drive system transmission torque becomes high, which affects the durability of the drive system. On the other hand, in order to ensure the durability of the drive system even when the fastening torque Tb is transmitted, it is necessary to increase the strength of all the drive system components, which is disadvantageous in terms of cost and weight.
[0069]
Next, the effect will be described.
[0070]
(1) In a four-wheel drive vehicle having an electromagnetic clutch 10 that controls the distribution of torque transmitted from the engine 1 to the front and rear wheels 6, 7, 14, and 15, the electromagnetic clutch is generated by the front and rear wheel rotational speed difference ΔV and the clutch transmission torque TE. 10 is calculated, the fluctuation of the clutch temperature that rises and falls over time is predicted according to the magnitude of the calculated input energy E, and is calculated based on this temperature fluctuation prediction. When the estimated clutch temperature T1n becomes equal to or higher than the clutch protection determination temperature Tp, the mode is automatically switched to the LOCK mode that suppresses slipping of the electromagnetic clutch 10, and the command current value I to the electromagnetic clutch 10 is switched to the engagement mode by driver selection. In order to perform clutch protection control to set the fixed current value Ib higher than the current value Ia in the case,
(1) Clutch slippage due to the temperature characteristics of the electromagnetic clutch 10 can be prevented, and clutch protection against clutch temperature rise can be reliably implemented.
(2) As the protection control for the electromagnetic clutch 10, automatic switching to the LOCK mode was adopted instead of releasing the clutch, so the four-wheel drive state will be maintained even after entering the clutch protection control, and the vehicle will travel on slippery road surfaces. Can be secured for a long time.
(3) The influence on the durability of the drive system can be suppressed without increasing the strength of the drive system.
The advantages are also obtained.
[0071]
(2) The command current value I to the electromagnetic clutch 10 at the time of clutch protection control is a fixed current value Ib obtained by adding a constant current value ΔI to the current value Ia when switching to the engagement mode by driver selection. By simply setting two values Ia and Ib as the command current values in the above, clutch protection control that achieves the effect (1) can be easily executed.
[0072]
(No.1Example)
This first1In the embodiment, as clutch protection control, when the clutch estimated temperature T1n becomes equal to or higher than the clutch protection determination temperature Tp, the electromagnetic clutch 10 is strongly engaged according to the magnitude of the clutch estimated temperature T1n in the LOCK mode, and further switched to the LOCK mode. However, when the estimated clutch temperature T1n is equal to or higher than the clutch limit determination temperature Tc, control (2WD) for releasing the electromagnetic clutch 10 is performed.
[0073]
The configuration shown in FIGS.referenceSince it is the same as the example, illustration and description are omitted.
[0074]
Next, the operation will be described.
[0075]
First1The input energy calculation process executed by the 4WD controller 16 of the embodiment is shown in FIG.referenceSince this is done by the flowchart of the example, illustration and description are omitted.
[0076]
[Clutch protection control processing]
Figure 8 shows the first1Each step will be described below with reference to a flowchart showing a flow of clutch protection control processing executed by the 4WD controller 16 of the embodiment. This process is executed at 640 msec / routine. Further, steps S30 to S44 are the same as steps S10 to S24 in the flowchart of FIG.
[0077]
In step S45, it is determined whether or not the current estimated clutch temperature T1n calculated in step S37 or step S41 is equal to or higher than the clutch limit determination temperature Tc. If YES, the process proceeds to step S46. If NO, step S46 is performed.S42 (clutch limit determination means).
[0078]
In step S46, based on the determination that the estimated clutch temperature T1n is equal to or higher than the clutch limit determination temperature Tc in step S45, 4WD torque = 0 (command current value I = 0) is set as clutch protection processing, and the electromagnetic clutch 10 is The state is released, and the process proceeds to step S47.1Clutch protection control means).
[0079]
In step S47, the driver is informed of the protection control mode by clutch release by blinking the lamp and operating the alarm for the warning lamp & alarm 26.
[0080]
In step S48, a required engagement torque (Ta1 to Ta2) when the estimated clutch temperature T1n becomes equal to or higher than the clutch protection determination temperature Tp is set according to the estimated clutch temperature T1n, and the estimated clutch temperature T1n is set to the clutch protection determination temperature Tp. A variable command current Ib ′ for obtaining the required engagement torque (Ta1 to Ta2) in a high temperature state within the range of the clutch limit determination temperature Tc is applied to the solenoid 24 of the electromagnetic clutch 10.
[0081]
That is, as shown in FIG. 9, when the estimated clutch temperature T1n is in a high temperature state within the range of the clutch protection determination temperature Tp to the clutch limit determination temperature Tc, the clutch limit is determined from the required engagement torque Ta1 at the clutch protection determination temperature Tp. The required engagement torque T is determined in proportion to the clutch estimated temperature T1n up to the required engagement torque Ta2 at the determination temperature Tc, and the variable command current Ib ′ for obtaining the determined required engagement torque T is calculated (or the TI map is The variable command current Ib ′ is applied to the solenoid 24 of the electromagnetic clutch 10. In addition, step S42, step S43, step S44, and step S48 are claimed.2This corresponds to the clutch protection control means.
[0082]
[Protection control action of electromagnetic clutch]
First1In the clutch protection control of the embodiment, when the estimated clutch temperature T1n becomes equal to or higher than the clutch protection determination temperature Tp when the AUTO mode is selected, step S45 → step S42 → step S43 → step S44 → step S48 in the flowchart of FIG. In step S43, the mode is switched from the AUTO mode to the LOCK mode. In step S48, the variable command current Ib ′ corresponding to the estimated clutch temperature T1n is applied to the solenoid 24 of the electromagnetic clutch 10.
[0083]
That is, as the clutch temperature is higher, even when the same command current is applied, the engagement torque decreases. As a result, the variable clutch current Ib ′ corresponding to the estimated clutch temperature T1n can stably engage the electromagnetic clutch 10 without slipping. Secured.
[0084]
However, even if the first stage clutch protection control by automatic switching to the LOCK mode is performed, if a driving torque exceeding the required fastening torque T is transmitted to the electromagnetic clutch 10 in a vehicle equipped with a large torque engine, the electromagnetic clutch 10 The clutch 10 slips, and the estimated clutch temperature T1n gradually increases and may reach the clutch limit determination temperature Tc set to a temperature higher than the clutch protection determination temperature Tp.
[0085]
As described above, when the estimated clutch temperature T1n becomes equal to or higher than the clutch protection determination temperature Tp, the flow proceeds from step S45 to step S46 to step S47 in the flowchart of FIG. 8. In step S46, the electromagnetic clutch 10 is released, and step S47 is performed. Then, the warning light & alarm 26 is informed to the driver that the protection control mode is based on the clutch release by blinking the lamp and operating the alarm.
[0086]
That is, when the rising gradient of the estimated clutch temperature T1n is steep, if the clutch protection determination temperature Tp is exceeded, the clutch engagement force is increased and the clutch rotational speed difference is suppressed to be small, and the rising gradient of the estimated clutch temperature T1n is moderated. In the four-wheel drive state, the travel distance and the travel time are ensured as long as possible. However, if the estimated clutch temperature T1n further increases in the clutch protection control in the first stage, the second stage for releasing the electromagnetic clutch 10. By performing the clutch protection control, it is possible to avoid the electromagnetic clutch 10 from being in a high temperature state exceeding the temperature guarantee limit.
[0087]
Next, the effect will be described. This first1In the front and rear wheel torque distribution control device of the four-wheel drive vehicle of the embodiment,referenceIn addition to the effect of the example (1), the following effect can be obtained.
[0088]
(3) The variable current value Ib ′ obtained by adding the correction current value corresponding to the estimated clutch temperature T1n to the current value Ia when the command current value I to the electromagnetic clutch 10 during clutch protection control is switched to the engagement mode by driver selection. Therefore, a constant clutch engagement torque can be obtained regardless of changes in the estimated clutch temperature T1n during the LOCK mode in the clutch protection control.
[0089]
(4) The clutch limit judgment temperature Tc is set as a temperature higher than the clutch protection judgment temperature Tp, the clutch estimated temperature T1n becomes equal to or higher than the clutch protection judgment temperature Tp, and the clutch estimated temperature T1n is not changed despite automatic switching to the LOCK mode. When the estimated clutch temperature T1n rises and reaches the clutch limit judgment temperature Tc, the clutch protection control is performed to release the electromagnetic clutch 10. Therefore, the electromagnetic distance is reliably ensured while ensuring the travel distance (time) in the four-wheel drive state. Protection by guaranteeing the temperature of the clutch 10 can be achieved.
[0090]
The first embodiment of the front and rear wheel torque distribution control device for the four-wheel drive vehicle of the present invention has been described above.For exampleBased on the explanation above,FirstThe present invention is not limited to the embodiments, and design changes and additions are permitted without departing from the spirit of the invention according to each claim of the claims.
[0091]
For example,1 fruitIn the embodiment, an example of a front and rear wheel torque distribution control device using a front wheel drive base was shown, but a front and rear wheel torque distribution control device using a rear wheel drive base, and front and rear wheel drive systems are provided with control clutches respectively. The present invention can also be applied to a device that controls the torque distribution of the wheels.
[0092]
The second1 fruitIn the example, an electromagnetic clutch was used as the control clutch.TheIt may be a hydraulic clutch or the like that is fastened by a control hydraulic pressure created by an electromagnetic valve provided at a position where it can be easily received.
[Brief description of the drawings]
[Figure 1]referenceIt is a whole system figure showing the front-and-rear wheel torque distribution control device of the four-wheel drive vehicle in an example.
FIG. 2 is a schematic diagram showing an electromagnetic clutch used in a front and rear wheel torque distribution control device for a four-wheel drive vehicle.
FIG. 3 is a perspective view showing a cam mechanism of an electromagnetic clutch used in a front and rear wheel torque distribution control device for a four-wheel drive vehicle.
FIG. 4 is a flowchart showing a flow of an input energy calculation process and a clutch protection control process performed by a 4WD controller used in a front and rear wheel torque distribution control device for a four-wheel drive vehicle.
FIG. 5 is a diagram showing a comparison characteristic between an estimated clutch temperature and an actual clutch temperature based on a temperature gradient coefficient used in calculating a temperature increase amount and a temperature decrease amount.
FIG. 6 is a comparison characteristic diagram showing a fastening torque characteristic with respect to a solenoid current to the electromagnetic clutch at a normal temperature and a fastening torque characteristic with respect to a solenoid current to the electromagnetic clutch at a high temperature.
[Fig. 7]referenceIt is a time chart which shows the input energy calculation in the front-and-rear wheel torque distribution control device of the four-wheel drive vehicle in the example, temperature adjustment determination, temperature fluctuation amount calculation, estimated temperature calculation, and clutch protection flag.
FIG. 81It is a flowchart which shows the flow of the clutch protection control process performed with the 4WD controller used for the front-and-rear wheel torque distribution control apparatus of the four-wheel drive vehicle of an Example.
FIG. 91ExampleofIt is a required torque characteristic figure with respect to the clutch estimated temperature of the high temperature range which requires the clutch protection control in an apparatus.

Claims (2)

In a four-wheel drive vehicle having a control clutch for controlling torque distribution transmitted from the drive source to the front and rear wheels,
Clutch rotational speed difference detecting means for detecting a relative rotational speed difference between input and output shafts of the control clutch;
Clutch transmission torque estimating means for estimating a driving torque transmitted through the control clutch;
Input energy calculating means for calculating input energy applied to the control clutch based on the clutch rotational speed difference and clutch transmission torque;
Clutch estimated temperature calculation means for predicting a clutch temperature fluctuation that rises or falls with the passage of time according to the calculated input energy, and calculates a clutch estimated temperature based on the temperature fluctuation prediction;
When the calculated estimated clutch temperature is less than the clutch protection determination temperature, an engagement control means for controlling the engagement state of the control clutch by outputting a command current so that the engagement torque of the control clutch is less than or equal to a predetermined upper limit value. When,
Clutch protection control means for performing clutch protection control for lowering the clutch temperature when the calculated estimated clutch temperature is equal to or higher than the clutch protection determination temperature ;
Clutch limit determination means for determining whether the estimated clutch temperature is higher than the clutch protection determination temperature or higher than the clutch limit determination temperature ;
The clutch protection control means includes
When the estimated clutch temperature is equal to or higher than the clutch protection determination temperature, the command current value to the control clutch is set to a high current value such that the engagement torque becomes the upper limit value even at the clutch protection determination temperature or higher .
When the estimated clutch temperature becomes equal to or higher than the clutch protection determination temperature, the estimated clutch temperature rises despite the command current being output to the control clutch, and the estimated clutch temperature reaches the clutch limit determination temperature, the control clutch A front and rear wheel torque distribution control device for a four-wheel drive vehicle, wherein the fastening is released .   The front and rear wheel torque distribution control device for a four-wheel drive vehicle according to claim 1, wherein the clutch protection control means sets a command current value to the control clutch when the estimated clutch temperature is equal to or higher than a clutch protection determination temperature. A front and rear wheel torque distribution control device for a four-wheel drive vehicle, wherein a variable current value obtained by adding a correction current value corresponding to an estimated clutch temperature to a current value at which an engagement torque is lower than a determination temperature and the upper limit value is set.

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