JP4110703B2 - Power distribution control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a power distribution control device that distributes power of a vehicle to a plurality of drivable wheels, and more particularly to a means for determining a torque distribution ratio to driven wheels in a four-wheel drive vehicle of an on-demand 4WD mechanism. However, the “driven wheel” mentioned here is a drivable wheel that can temporarily set the torque distribution ratio of the power (driving force) of the vehicle supplied from the engine or motor to 0 or relatively small. The “main drive wheel” referred to here is a drivable wheel to which relatively large power (driving force) is constantly transmitted during traveling or acceleration.
[0002]
[Prior art]
  As an apparatus for controlling the torque distribution ratio for each drivable wheel by electronic control, for example, Japanese Patent Application Laid-Open No. 7-40753: Driving force distribution integrated control apparatus for left and right wheels and front and rear wheels (hereinafter referred to as “Prior Art 1” And those described in the published patent publication “Japanese Patent Laid-Open No. 7-25258: Differential Limit Control Device” (hereinafter referred to as “Prior Art 2”). Are known.
[0003]
  In these conventional technologies, in a so-called on-demand 4WD mechanism four-wheel drive vehicle in which the torque distribution ratio between the front wheels and the rear wheels is variable, for example, the torque distribution ratio r to the driven wheels is “0 ≦ r ≦ r._max<1 (r_maxIs a predetermined constant) ”, the differential rotational speed ΔN between the front wheel and the rear wheel is monitored, and the torque distribution ratio r to the driven wheel is increased as the differential rotational speed ΔN increases. Increasing the size is a general control theory. That is, the torque distribution ratio r to the driven wheel is equal to a certain saturation point (upper limit value: r_maxIn general, the control is performed so as to be substantially proportional to the differential rotational speed ΔN between the front wheels and the rear wheels.
[0004]
  In addition, as a clutch mechanism of a coupling device, a large number of clutch mechanisms using an electromagnetic clutch having higher responsiveness than a hydraulic clutch are now widely used.
  FIG. 13 ((a), (b)) is a block diagram illustrating a logical configuration of a conventional power distribution control device. For example, the calculation of the torque distribution ratio r as described above is specifically executed by the “torque distribution ratio calculation unit 202” in FIG.
  However, the definition of each variable in FIG. 13 is as follows.
[0005]
(Variable definition)
    n: A general term for the rotational speed (n1, n2,...) of each drivable wheel
  ΔN: Differential rotation speed between front and rear wheels
    r: Torque distribution ratio to the driven wheel
    I_n: Coil current command value
    V_n: Coil voltage command value
    V_cc: Power-supply voltage
    λ: Duty ratio in chopper control (PWM control)
[0006]
  Further, in these prior arts, for example, as shown in FIG. 13B, the coil current of the electromagnetic clutch is actually measured, and this measured value I_aAnd coil current command value I_nCurrent deviation ΔI (≡I_n-I_a) Based on PID control (proportional integral differential control executed by “PID210” in the figure), there is a type that controls the coil current I more accurately.
[0007]
  In the proportional-integral-derivative control executed by “PID210” in FIG. 13B, for example, the coil voltage command value V based on the following equation (1):_nMethods such as determining the value of have been taken.
[Expression 1]
  V_n= Λ'V_CC+ G₁ΔI + g₂∫ΔIdt + g_ThreedΔI / dt (1)
[Expression 2]
  λ = V_n/ V_CC                                              ... (2)
[0008]
  Here, λ ′ is the duty ratio (or provisional initial value of the duty ratio λ) obtained in the previous PWM control obtained in the previous control cycle, and the gain g₁, G₂, G_ThreeAre appropriate constants.
  Expression (2) is a calculation expression for the duty ratio λ, which is executed by the “duty ratio calculation unit 205” in FIG.
[0009]
[Problems to be solved by the invention]
  FIG. 14 is a graph showing problems of the prior art, in which time values of the state variables of the throttle valve opening m, the torque distribution ratio r to the driven wheel, and the differential rotational speed ΔN between the main driving wheel and the driven wheel are plotted. Each change is illustrated. More specifically, this graph shows the result of simulating the driving state (slip / stop state) of a four-wheel drive vehicle at the time of “a sudden start of a low friction road” on a frozen road surface, for example, when there is snow. From this graph, it can be seen that the clutch mechanism is chattering.
[0010]
  When the clutch mechanism of the coupling device is configured by an electromagnetic clutch, the response (speed response) of the clutch mechanism is extremely high. For this reason, in an on-demand 4WD system using an electromagnetic clutch, for example, when starting or accelerating on a low friction road as described above, for example, chattering or slip / stop phenomenon as shown in FIG. 14 may be caused. is there. Further, when the responsiveness of the clutch mechanism is high, for example, the coupling device may chatter even at a sudden start on a road surface having a relatively high friction coefficient.
  That is, in these cases, there is a risk that stable and reliable traction (driving force) cannot be obtained sufficiently, or the ride comfort is reduced due to chattering noise or vibration.
[0011]
  However, if the responsiveness of the clutch mechanism (mainly electromagnetic clutch) has been lowered uniformly (entirely) as a countermeasure, reliable and stable traction (acceleration performance) by four-wheel drive is immediately required. In the event of an emergency, there is a risk that sufficiently high responsiveness (rapid response) cannot be obtained for traction.
[0012]
  The present invention has been made to solve the above-described problems, and has as its purpose high response to required acceleration performance (traction) and no chattering or slip / stop phenomenon. An object is to provide a power distribution control device that is excellent in both of the speed response and damping (convergence).
[0013]
[Means for Solving the Problems]
  In order to solve the above problems, the following means are effective.
  That is, the first means applies the power to the driven wheel when distributing the power of the vehicle supplied from the engine or the motor to a plurality of drivable wheels.torqueDistribution ratio rBy coupling deviceIn the power distribution control device to be controlled, the upper limit value r of the torque distribution ratio r_maxSmaller than that and once reached a suitable value r0 within a range where a reliable driving force without slip phenomenon can be obtained.Torque distributionThe residual time control means for controlling the residual time T in which r remains in the vicinity of the preferred value r0 thereafter, the residual time control means,The current deviation between the current command value determined by the differential rotation speed ΔN, which is the difference between the rotation speed of the main drive wheel and the rotation speed of the driven wheel, and the current measurement value of the control current of the control current I for the coupling device Proportional control, proportional-integral control, or proportional-integral-derivative control related to ΔI is performed, and in a region where the amount of change dΔN within a predetermined minute time of the differential rotational speed ΔN satisfies dΔN ≦ 0, the accelerator pedal depression amount θ, the engine The time constant τ is determined so as to increase as the acceleration operation-related value related to the driver's acceleration operation at the rotational speed p or the throttle valve opening m increases, and proportional control and proportional integration are performed according to the time constant τ. The power distribution control device is characterized in that the remaining time T is increased as the time constant τ increases by changing the gain of the control or proportional-integral-derivative control.
[0014]
  However, here, the acceleration operation related value A may be a set of parameters composed of a plurality of parameters. The acceleration operation-related value A may be anything as long as it reflects the driver's intention to operate the vehicle, and may be, for example, an accelerator pedal depression amount, an engine speed, or the like. The acceleration operation-related value A of the present invention can be configured by a variable (acceleration operation parameter) that can take at least two values.
[0015]
  Note that each function such as f1 described above used in the present invention is generally an arbitrary data map (table), polynomial, or predetermined algorithm, for example, by a known information processing technique. It can be specifically configured by means. That is, all functions used in the present invention can be anything as long as they are composed of real-to-real (more specifically, rational-to-rational) one-to-one or many-to-one mappings. Well, the specific implementation method is not limited.
[0016]
  The second means is:An upper limit value r of the torque distribution ratio r in a power distribution control device that controls the torque distribution ratio r to the driven wheels when the power of the vehicle supplied from the engine or the motor is distributed to a plurality of driveable wheels. _max A residual time control means for controlling the residual time T once the torque distribution r that has once reached a suitable value r0 within a range in which a reliable driving force that does not generate a slip phenomenon is smaller than the preferred value r0. The remaining time control means includes a current command value determined by a differential rotation speed ΔN which is a difference between the rotation speed of the main drive wheel and the rotation speed of the driven wheel of the control current I for the coupling device, and a control In a region where the variation dΔN within a predetermined minute time of the differential rotation number ΔN satisfies dΔN ≦ 0 by performing proportional control, proportional integral control, or proportional integral differential control on the current deviation ΔI of the current with respect to the current measurement value. The time constant τ is determined so as to increase as the acceleration operation-related value related to the acceleration operation of the driver, which is the accelerator pedal depression amount θ, the engine speed p or the throttle valve opening m, increases. The absolute value of the lower limit value of the fluctuation amount Δr per unit time of the torque distribution ratio r is set so as to decrease as the time constant τ increases, and the change amount of the absolute value of the torque distribution ratio r is the absolute value of the lower limit value. The power distribution control device is characterized in that the residual time T is increased as the time constant τ increases by controlling the current command value in accordance with the torque distribution ratio r determined in this way by making it smaller than the value. It is.
[0017]
[0018]
[0019]
  Further, the third means is the residual time control means in the first or second means described above, wherein when the change amount dΔN satisfies dΔN> 0, the value of the time constant τ is independent of the change amount dΔN. This means that the variable B is determined by a monotone decreasing function f2 (B).
[0020]
  Here, B may be a set of parameters composed of a plurality of parameters. The function f2 is a monotonously decreasing function in a broad sense of “B1 <B2 => f2 (B1) ≧ f2 (B2)”. Therefore, the function f2 may be a constant function having a constant function value.
  The above-described problems can be solved by the above means.
[0021]
[Operation and effect of the invention]
  The “residual time T” in the present invention is a time required for reestablishing the vehicle when the vehicle falls into a slip / stop state. During this period, the drive performance is assured with all the drivable wheels as much as possible. Is preferably supplied. Conversely, the torque distribution to the driven wheels is at least until these slip states are reestablished (for example, the period from the slip stop state to the transition to a stable start state with a reliable driving force). The torque distribution ratio r is preferably maintained at a value in the vicinity of the preferred value r0.
[0022]
  FIG. 1 is a graph obtained by enlarging a part of FIG. 14 and shows a torque distribution ratio r to the driven wheels and changes with respect to time t of the differential rotational speed ΔN between the main driving wheel and the driven wheel.
  As can be seen from FIG. 1, in the driving state of the four-wheel drive vehicle at the time of this “low friction road sudden start”, a range of “r0−δ <r ≦ r0” is an appropriate range of the torque distribution ratio r. it is conceivable that. If the torque distribution ratio r is larger than necessary, the fuel consumption is not suppressed correspondingly, and if the torque distribution ratio r is smaller than the necessary amount, the differential rotational speed ΔN increases and a slip phenomenon occurs.
[0023]
  Therefore, for example, in the situation shown in FIGS. 1 and 14, if the time “r0−δ <r” or “r0−δ <r ≦ r0” is sufficiently secured, that is, the “residual time T” described above. ”Can be avoided, the above chattering and slip / stop phenomenon can be avoided.
  The residual time control means of the present invention controls this “residual time T” using one parameter (time constant τ), and this residual time T is approximately proportional to one time constant τ. Be controlled.
[0024]
  When the differential rotation speed ΔN is converging to 0 (when dΔN ≦ 0), in order to maintain this convergence (attenuation) and avoid chattering and the like, the remaining time T is 4 wheels. The longer the time when stable traction by driving is required, the better.
  The necessity (necessity) of the stable traction can be quantitatively read from the acceleration operation related value A. For example, as the differential rotational speed ΔN is larger and the accelerator pedal depression amount θ (or throttle valve opening m, etc.) is larger, the slip state is more severe and stable traction by four-wheel drive is required. You may judge that it is.
[0025]
  FIG. 2 shows the throttle valve opening m, the torque distribution ratio r to the driven wheel, and the main driving wheel when the above “residual time T” is lengthened under the condition “dΔN ≦ 0” by these means. 6 is a graph showing changes in time of each state variable of the differential rotational speed ΔN between the motor and the driven wheel. According to the above-mentioned means of the present invention, for example, the “necessity of stable traction” is quantitatively measured from the acceleration operation-related value A such as the throttle valve opening m, and the differential rotational speed ΔN converges to zero. In some cases (when dΔN ≦ 0), the value of the time constant τ is determined by the function f1 according to the necessity of this traction. By such optimization control of the remaining time T using the time constant τ as an adjustment parameter, the remaining time T required for each state is appropriately secured.
  Thus, the torque distribution ratio r is maintained in an appropriate range (“r0−δ <r” or “r0−δ <r ≦ r0”) until the slip state is reset.
[0026]
  Also,When the torque distribution ratio r is controlled, its speed response is secured, and after determining the time constant τ to a suitable value as described above,PBy adjusting a coefficient (gain G) such as a current deviation of the coil current of the ID-controlled electromagnetic clutch, the stability (convergence) of the torque distribution ratio r once reaching a suitable value is ensured.
[0027]
  In addition, the above-mentioned present inventionSecondThe means secures the quick response when controlling the torque distribution ratio r, determines the time constant τ to a suitable value as described above, and then determines the subsequent torque distribution ratio r according to the value of τ. By restricting the fluctuation amount, the stability (convergence) of the torque distribution ratio r once reaching a suitable value is ensured.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
(First embodiment)
  FIG. 3 is a schematic system configuration diagram of the power distribution control device 100 according to this embodiment mounted on a four-wheel drive vehicle.
  This four-wheel drive vehicle has an FF-based so-called on-demand 4WD mechanism, and the torque distribution ratio between the front wheels and the rear wheels is suitably controlled by this mechanism.
[0029]
  The transaxle 40 is integrally provided with a transmission and a transfer. The driving force (torque) supplied from the engine 30 is selected by the transaxle 40 and the front differential gear (differential differential) is selected. Device) 25. Thereafter, the torque transmitted to the front differential gear (differential device) 25 is distributed to the front wheel axles 27, 27 and the propeller shaft 20, and the main drive wheels (front wheels) 1, 2 are driven.
  A coupling (clutch mechanism) 50 is connected to one end of the propeller shaft 20 at the rear.
[0030]
  The torque transmitted to the coupling 50 via the propeller shaft 20 is sequentially transmitted to the rear wheel drive shaft 24, the rear differential gear 26, and the rear wheel axle 28, and driven wheels (rear wheels) 3, 4 are sequentially transmitted. Drive. However, when the torque distribution ratio r to the driven wheels (3, 4) is 0, the clutch mechanism of the coupling 50 is controlled to the released state (non-coupled state), and therefore the driven wheel (rear wheel) 3 , 4 are not driven. In general, the clutch mechanism of the coupling 50 may be a mechanism based on electromagnetic operation (electromagnetic clutch) or a mechanism based on hydraulic pressure (hydraulic clutch).
[0031]
  However, in the first embodiment, the clutch mechanism of the coupling 50 is constituted by an electromagnetic clutch. By this clutch mechanism, the torque distribution ratio r to the driven wheels (3, 4) is within a predetermined range (0 ≦ r ≦ r_max<1) is realized. Maximum value r of this torque distribution ratio r_maxIs about 1/2. For example, if “0 ≦ r ≦ 1/2”, “r = 1/2 (= r_max) ", The clutch mechanism is directly connected, and at this time, substantially the same torque is distributed to the front wheels and the rear wheels.
Further, the operation of the electromagnetic clutch is performed by the current I flowing through the coil C in FIG. 4 (or the current I in FIG._n). That is, the target value (command current) I of the current I flowing through the coil C according to the target value of the torque distribution ratio r._nIs determined.
[0032]
  Wheel speed signals n1, n2, n3, and n4 (hereinafter may be collectively referred to as “driveable wheel rotation speed n” or simply “n”, etc.) may be output from the rotation sensors 5 to 8, respectively. The data is coincident with or proportional to the rotational speed [rpm] of the drivable wheels 1, 2, 3, and 4. Further, the throttle valve opening sensor 10 outputs the value of the throttle valve opening m. And these output data are input into the power distribution control apparatus 100 of FIG.
[0033]
  FIG. 4 is a hardware configuration diagram of the power distribution control device 100 according to the first embodiment. The coil C that operates the electromagnetic clutch that constitutes the coupling 50 has a DC drive power supply (power supply voltage V_CC) Get more power. The magnitude I of the direct current is controlled by chopper control using an electronic control switch SW constituted by a power MOS • FET, a PMOS drive circuit 108, and a PWM converter 105.
  The CPU 101 is a program described later stored in the ROM 102 and the RAM 103, and the above numerical values (m, n, V_CC, I) and the like are used to calculate the duty ratio λ to be output to the PWM converter 105.
[0034]
  A resistor 110 having a resistance value r [Ω] is connected in series with the coil current path (that is, on the coil current path) on the lower voltage side (0 ground side) of the electronic control switch SW. The negative terminal of the current detector 109 is connected to the lower voltage side of the resistor 110, and the positive terminal of the current detector 109 is connected to the upper voltage side. The current detector 109 receives the potential difference v [V] across the resistor 110 to detect the current i flowing through the resistor 110 and outputs it to the A / D converter 106. The CPU 101 determines the value of the coil current I [A] (coil current measurement value I_a) Is calculated from the current i input from the A / D converter 106. As this calculation method, for example, there is a method of taking an average of several values measured within a predetermined period of the current i.
[0035]
  FIG. 5 is a block diagram showing a logical configuration of the power distribution control device 100 in the first embodiment. This configuration is obtained by adding a remaining time control unit 300 to the conventional configuration shown in FIG.
  The remaining time control unit 300 includes a time constant calculation unit 301 that calculates the time constant τ and a gain compensation unit 302 that calculates a gain G in PID control based on the time constant τ.
[0036]
  The operation of each block in FIG. 5 will be described below with reference to FIG.
  FIG. 6 is a flowchart of a program executed by the CPU 101 (FIG. 4) of the power distribution control device 100 according to the first embodiment. In this program, first, in step 605, the current i, the throttle valve opening m, the rotation speed n (n1, n2, n3, n4) of each drivable wheel and the power supply voltage V in FIG._ccEnter each.
  However, the power supply voltage V_ccIs a physical quantity whose change with time is relatively small, and therefore it is not always necessary to input every control period.
[0037]
  Next, in step 610 (differential rotation speed calculation unit 201), the differential rotation speed ΔN between the front wheels and the rear wheels is obtained by the following equation (3).
[Equation 3]
  ΔN = c1 (n1 + n2-n3-n4) / 2 (3)
  Here, c1 is an appropriate proportionality constant. However, when the inputs n1, n2, n3, and n4 from the respective rotation sensors (5 to 8) coincide with the rotation speeds of the respective driveable wheels, c1 = 1 may be set.
[0038]
  Next, in step 615 (torque distribution ratio calculation unit 202), the torque distribution ratio r (0 ≦ r ≦ r) to the driven wheel is determined from the differential rotational speed ΔN._max). Here, the upper limit value r of r_maxFor example, the value of ½ is set to ½, which means that the coupling device 50 is directly connected. Further, the value of r is determined so as to be substantially proportional to ΔN as in the known prior art.
[0039]
  Further, the remaining time control unit 300 is specifically realized by a group of steps from step 620 to step 650 described below. That is, in step 620, an increment dΔN from the previous control cycle of the differential rotational speed ΔN obtained in step 615 is obtained. If this value is 0 or less, the process proceeds to step 625, and if this value is positive, the process proceeds to step 630. Transfer.
[0040]
  In step 625, the value of the time constant τ is determined by the monotonic increasing function f1 shown in FIG. As a result, even if the differential rotational speed ΔN tends to decrease (or remain unchanged), the greater the value of the throttle valve opening m, that is, the stronger the driver is willing to accelerate, the four-wheel drive The time during which stable traction is maintained, that is, the “residual time T” is increased.
[0041]
  In step 630, the value of the time constant τ is determined by the monotone decreasing function f2 shown in FIG. As a result, the time constant τ is set smaller as the increment dΔN is larger, that is, as the slip state is rapidly worsening or intensifying, such as in an emergency where stable traction by four-wheel drive is required. High speed response in terms of driving performance can be obtained. The time constant calculation unit 301 is configured by the above steps 620 to 630.
[0042]
  Further, in step 650 (gain compensation unit 302), the gain G is obtained by the function g (the following equation (4)) shown in FIG. 9 based on the time constant τ, thereby the proportional term ΔI of the equation (1). Coefficient g₁To compensate.
  That is, in the first embodiment, PID control is performed using the following equation (5) based on this gain compensation in place of equation (1) in the processing described later.
[0043]
[Expression 4]
  G = g (τ) (4)
[Equation 5]
  V_n= Λ'V_CC+ GΔI + g₂∫ΔIdt + g_ThreedΔI / dt (5)
[0044]
  In step 660 (coil current calculation unit 203), the coil current command value I is calculated from the torque distribution ratio r obtained in step 615 (torque distribution ratio calculation unit 202)._nTo decide. In step 670, the coil current measurement value I is calculated from the average value of the current i shown in FIG._aIs calculated.
[0045]
  In step 680 (PID control unit 210), current deviation ΔI (≡I_n-I_a) And the gain G of equation (4), as shown in equation (5), the coil voltage command value V_nAsk for.
  However, the gain g of the integral term is obtained by substantially the same means.₂Or the gain g of the differential term_ThreeCompensation for the above may be performed simultaneously or independently. Further, instead of the function g, the dependent variable (function value G) decreases exponentially with respect to the independent variable (time constant τ), for example, as in the function h shown in FIG. A monotonically decreasing function that is inversely proportional can also be used.
[0046]
  Further, in step 690 (duty ratio calculation unit 205), the duty ratio λ is calculated by the equation (2), and in step 695, the duty ratio λ is output to the PWM control unit 206 in FIGS.
[0047]
  It should be noted that monotonically decreasing functions such as the above-described function g and function h may be selected empirically suitable in accordance with the characteristics of the coil C, the coupling device 50, etc. in FIG.
  For example, a sudden decrease in the torque distribution ratio r can be suppressed by the action of the gain compensator 302 (step 650). That is, by the gain compensation control, the remaining time T can be maintained appropriately as shown in FIG.
[0048]
(Second embodiment)
  FIG. 10 is a hardware configuration diagram of the power distribution control device 400 in the second embodiment. The power distribution control device 400 can be mounted on the 4WD system of FIG. 3 instead of the power distribution control device 100 (FIG. 4) of the first embodiment.
  The only difference between the power distribution control device 400 and the power distribution control device 100 is that the A / D converter 106 and the current detector 109 are present. That is, the power distribution control device 400 does not have a feedback loop for the coil current I.
[0049]
  FIG. 11 is a block diagram showing a logical configuration of the power distribution control device 400 in the second embodiment. This configuration is an improvement of the conventional logical configuration of FIG. 13A, and a remaining time control unit based on the means of the present invention is provided between the torque distribution ratio calculation unit 202 and the coil current calculation unit 203. The most important feature is that 500 is provided.
[0050]
  The remaining time control unit 500 includes a time constant calculating unit 501 that calculates a time constant τ, and a lower limit value kD () of a variation Δr per unit time s of the torque distribution ratio r to the driven wheel based on the time constant τ. a torque fluctuation limiting unit 502 for controlling k = ± 1).
[0051]
  The operation of each block in FIG. 11 will be described below with reference to FIG.
  FIG. 12 is a flowchart of a program executed by the CPU 101 (FIG. 10) of the power distribution control device 400 in the second embodiment. In this program, first, in step 805, the throttle valve opening m in FIG. 10, the number of rotations n (n1, n2, n3, n4) of each driveable wheel, and the power supply voltage V_ccEnter each.
  However, the power supply voltage V_ccIs a physical quantity whose change with time is relatively small, and therefore it is not always necessary to input every control period.
[0052]
  Steps from step 610 to step 625 operate in the same manner as in the first embodiment. That is, for example, in step 620, an increment dΔN from the previous control period of the differential rotation number ΔN obtained in step 615 is obtained. If this value is 0 or less, the process proceeds to step 625, and if this value is positive, the process proceeds to step 830. Move processing.
  The remaining time control unit 500 in the second embodiment includes steps 620, 625, and steps 826 to 855.
[0053]
  In step 826, -1 is substituted into a variable k representing a sign.
  On the other hand, in step 830, as indicated by a broken line in FIG. 8, the value of the time constant τ is set to a predetermined appropriate constant τ regardless of the fluctuation amount of the differential rotational speed ΔN.₀To decide. In step 835, +1 is substituted for the variable k representing the sign.
  The processing of the time constant calculation unit 501 is executed by the processing from step 620, step 625, and steps 826 to 835 described above.
[0054]
  Hereinafter, the operation of the torque fluctuation limiting unit 502 that controls the lower limit value kD of the fluctuation amount Δr will be described. The torque fluctuation limiting unit 502 includes steps from step 840 to step 855.
  In step 840, a fluctuation amount Δr of the torque distribution ratio r to the driven wheel is obtained by the following equation (6). Here, r is the value obtained in step 615 (torque distribution ratio calculation unit 202) this time, and r ′ is output from the remaining time control unit 500 to the coil current calculation unit 203 last time (in the previous control cycle). Is the command value of the torque distribution ratio.
[Formula 6]
  Δr = r−r ′ (6)
[0055]
  Next, in step 845, the absolute value D of the lower limit value of the fluctuation amount Δr of the torque distribution ratio r is obtained by the following equation (7). Here, δ (> 0) is the width of the appropriate range of the torque distribution ratio r under the current situation as shown in FIGS. 1 and 2, for example, and s (> 0) is the length of each of the above control cycles. , Τ (> 0) is a time constant obtained by the current time constant calculation unit 501 (step 625 or step 830). However, appropriate constants may be used for δ and s.
[Expression 7]
  D = δs / τ (7)
[0056]
  In step 850, substitution calculation processing for resetting the value of the variation Δr of the torque distribution ratio r by the following equation (8) is executed.
[Equation 8]
  Δr = MAX (Δr, kD) (8)
  Here, MAX (a, b) is a function that selects a smaller one from a and b.
[0057]
  In step 855, the substitution calculation process for resetting the torque distribution ratio command value r ′ output to the coil current calculation unit 203 this time is executed according to the following equation (9).
[Equation 9]
  r ′ = r ′ + Δr (9)
  Here, r ′ on the left side is the current command value to be updated, and r ′ on the right side is the command value used in the previous control cycle.
[0058]
  In step 860 (coil current calculation unit 203), the command value I of the coil current I (FIG. 10) to be passed through the coil C is determined based on the torque distribution ratio command value r 'obtained in step 855._nTo decide.
  In step 880 (coil voltage calculation unit 204), the command value I of the coil current obtained in step 860 is obtained._nFrom the coil voltage command value V_nTo decide.
[0059]
  Further, in step 690 (duty ratio calculation unit 205), the duty ratio λ is calculated by the equation (2), and in step 695, the duty ratio λ is output to the PWM control unit 206 in FIGS.
[0060]
  Even with such a method, it is possible to achieve a torque distribution ratio that guarantees high speed response and stable damping (convergence), so the responsiveness to the required acceleration performance (traction) is high, In addition, it is possible to obtain an excellent power distribution control device in which chattering and slip / stop phenomenon do not occur.
[0061]
  The acceleration operation-related value (A) of the present invention related to the driver's acceleration operation may be anything that reflects the driver's intention to operate the vehicle, such as an accelerator pedal depression amount or an engine. The number of revolutions may be used. The acceleration operation-related value (A) of the present invention can be constituted by a variable that can take at least two values.
[0062]
  Further, for example, the related value such as the throttle valve opening m may be a transmission gear for transmitting the engine output to the drivable wheels, the rotational speed of the shaft, or the like. It is also possible to detect the driver's intention to operate the vehicle based on these numerical values or the amount of change thereof.
[0063]
  In each of the above embodiments, it is assumed that the resistance value r of the resistor 110 or the resistance value γ when the switch SW (power MOS • FET) is conductive is sufficiently small. Although the duty ratio λ is obtained, when the magnitudes of r and γ cannot be ignored, the duty ratio λ is obtained by the following equation (10).
[Expression 10]
  λ = V_n/ {V_CC−I (r + γ)} (10)
  Here, I is the coil current described in FIG. 4 or FIG. 10, and this value is a command value I of the coil current._nOr measured value I of coil current_aShall be used.
[0064]
  Each function such as f1, f2, g and the like is specifically configured by a generally known information processing technique using, for example, an arbitrary method such as a predetermined data map (table), a polynomial, an algorithm, or the like. Can do.
[Brief description of the drawings]
FIG. 1 is a graph illustrating changes in torque distribution ratio r to driven wheels, and changes in differential rotational speed ΔN between main drive wheels and driven wheels with respect to time t, for explaining the operation of the present invention.
FIG. 2 is a graph illustrating a change in a throttle valve opening m, a torque distribution ratio r to a driven wheel, and a differential rotation speed ΔN between the main driving wheel and the driven wheel with respect to time t, for explaining the effect of the present invention.
FIG. 3 is a system configuration diagram of a vehicle equipped with a power distribution control device 100 according to the present invention.
FIG. 4 is a hardware configuration diagram of the power distribution control device 100 according to the first embodiment.
FIG. 5 is a block diagram showing a logical configuration of a power distribution control device 100 in the first embodiment.
FIG. 6 is a flowchart of a program executed by the CPU 101 of the power distribution control device 100 in the first embodiment.
FIG. 7 is a graph showing the relationship (monotonically increasing function f1) of the time constant τ to the throttle valve opening m.
FIG. 8 is a graph showing the relationship (monotonically decreasing function f2) of the time constant τ with respect to the increment dΔN of the differential rotation speed ΔN.
FIG. 9 is a graph showing the relationship (monotonic decrease) of gain G to time constant τ.
FIG. 10 is a hardware configuration diagram of a power distribution control device 400 according to the second embodiment.
FIG. 11 is a block diagram showing a logical configuration of a power distribution control device 400 in the second embodiment.
FIG. 12 is a flowchart of a program executed by the CPU 101 of the power distribution control device 400 in the second embodiment.
FIG. 13 is a block diagram showing a logical configuration of a conventional power distribution control device.
FIG. 14 shows changes in the throttle valve opening m, the torque distribution ratio r to the driven wheel, and the differential rotational speed ΔN between the main driving wheel and the driven wheel with respect to time t, showing problems (chattering) of the prior art. Graph showing.
[Explanation of symbols]
  100, 400 ... Power distribution control device
  300, 500 ... Residual time control unit
  301, 501 ... Time constant calculation unit
          302 ... Gain compensation section
          502 ... Torque fluctuation limiter
          101 ... CPU (Central Processing Unit)
            50 ... Coupling (clutch mechanism)
            10 ... Throttle valve opening sensor
              C ... Coil
            SW: Switch (Power MOS / FET)
              r ... Torque distribution ratio to the driven wheel
            r0 ... preferred value of r
            ΔN ... Differential rotation speed between main drive wheel and driven wheel
              δ ... The width of the appropriate range of r
              T… remaining time
              τ… Time constant for residual time control
              I ... Coil current of electromagnetic clutch
              G ... Gain of control term (proportional term, etc.) for proportionally controlling I
              A ... Acceleration operation related value (θ, p, or m, etc.)
              θ… accelerator pedal depression
              p… engine speed
              m ... throttle valve opening
            f1 ... monotonically increasing function with A as an independent variable
            f2 ... Monotonically decreasing function

Claims (3)

In the power distribution control device for controlling the torque distribution ratio r to the driven wheels when the power of the vehicle supplied from the engine or the motor is distributed to a plurality of drivable wheels by the coupling device ,
Smaller than the upper limit value r _max of the torque distribution ratio r, in the vicinity of the torque distribution r is then also the preferred value r0 which once reached the suitable value r0 within the range obtained a reliable driving force slip phenomenon does not occur A residual time control means for controlling the residual time T remaining;
The remaining time control means includes
A current command value determined by a differential rotation speed ΔN, which is a difference between the rotation speed of the main drive wheel and the rotation speed of the driven wheel, of the control current I for the coupling device; and a current measurement value of the control current; Proportional control, proportional integral control, or proportional integral derivative control for current deviation ΔI of
In a region where the change amount dΔN of the differential rotation speed ΔN within a predetermined minute time satisfies dΔN ≦ 0, the acceleration operation of the driver having the accelerator pedal depression amount θ, the engine rotation speed p, or the throttle valve opening m is performed. The time constant τ is determined so as to increase as the related acceleration operation related value increases.
According to the time constant τ, the remaining time T is increased as the time constant τ increases by changing the gain of the proportional control, proportional integral control, or proportional integral derivative control. Control device. In the power distribution control device for controlling the torque distribution ratio r to the driven wheels when the power of the vehicle supplied from the engine or the motor is distributed to a plurality of drivable wheels by the coupling device,
The torque distribution r, which is smaller than the upper limit value r _max of the torque distribution ratio r and has once reached a suitable value r0 within a range in which a reliable driving force without slip phenomenon is obtained, is thereafter in the vicinity of the suitable value r0. A residual time control means for controlling the residual time T remaining;
The remaining time control means includes
A current command value determined by a differential rotation speed ΔN, which is a difference between the rotation speed of the main drive wheel and the rotation speed of the driven wheel, of the control current I for the coupling device; and a current measurement value of the control current; Proportional control, proportional integral control, or proportional integral derivative control for current deviation ΔI of
In a region where the change amount dΔN of the differential rotation speed ΔN within a predetermined minute time satisfies dΔN ≦ 0, the acceleration operation of the driver having the accelerator pedal depression amount θ, the engine rotation speed p, or the throttle valve opening m is performed. The time constant τ is determined so as to increase as the related acceleration operation related value increases.
The absolute value of the lower limit value of the fluctuation amount Δr per unit time of the torque distribution ratio r is set so as to decrease as the time constant τ increases, and the change amount of the absolute value of the torque distribution ratio r is set to the lower limit value. The residual time T is increased as the time constant τ increases by controlling the current command value in accordance with the torque distribution ratio r determined in this way by making it smaller than the absolute value of the value. Power distribution control device. When the change amount dΔN satisfies dΔN> 0 , the remaining time control means determines the value of the time constant τ by a monotonically decreasing function f2 (B) having the change amount dΔN as an independent variable B. power distribution control apparatus for placing serial to claim 1 or claim 2, characterized.

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