JP2009056884A - Vehicle driving force control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain driving force corresponding to drivability requested by a driver for every driving mode in a vehicle having a plurality of driving modes with different driving force characteristics. <P>SOLUTION: Based on a road surface friction coefficient μ and grounding load Fzi of each wheel, a standard friction circle limit value Sμ_Fzi of each wheel is set (S4). When the driving mode Dm is a normal mode Dn, a friction circle limit value μ_Fzi is set by the standard friction circle limit value Sμ_Fzi (S7). When the driving mode Dm is a save mode Ds, the standard friction circle limit value Sμ_Fzi is corrected with a correction value αs (where 0.5<αs<1.0) to set a reduced friction circle limit value μ_Fzi (S8). When the driving mode Dm is a power mode Dp, the standard friction circle limit value Sμ_Fzi is corrected with a correction value αp (where 1.0<αp<1.5) to set a magnified friction circle limit value μ_Fzi (S9). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle driving force control device capable of appropriately maintaining a wheel grip force for each of a plurality of driving modes having different driving force characteristics in a vehicle having a plurality of driving force characteristics.

  Conventionally, Patent Document 1 (Patent Document 1) includes a plurality of different driving force characteristics in a single vehicle, and one driving force characteristic can be selected according to the driver's preference from the plurality of driving force characteristics. No. 3930529).

In recent vehicles, various driving force control devices for suppressing excessive driving force have been developed and put into practical use in order to maintain the wheel grip force. For example, Patent Document 2 (Japanese Patent Laid-Open No. 10-310042) discloses a technique for obtaining a friction circle limit value of each wheel and controlling the driving force of the vehicle within a range not exceeding the friction circle limit value. Yes.
Japanese Patent No. 3930529 JP 10-310042 A

  By the way, in a vehicle having a plurality of operation modes having different driving force characteristics in one vehicle, the driver's requirements for drivability differ for each operation mode. For example, when a driving force characteristic that realizes powerful traveling is selected as in circuit traveling, there is a demand for setting the slip ratio of the wheels to be relatively high. Conversely, when driving force characteristics that enable economical driving are selected in a driving environment that does not require much power, such as on general roads and rainy weather, there is a demand to set the slip ratio relatively low. .

  However, the technique disclosed in the cited document 2 cannot cope with a vehicle having a plurality of driving modes having different driving force characteristics, and the driving force so as not to exceed the uniformly set friction circle limit value. Therefore, there is a problem that the slip ratio cannot be changed for each operation mode, and the drivability requested by the driver cannot be met.

  In view of the above circumstances, the present invention provides a vehicle driving force control capable of obtaining a driving force corresponding to the drivability requested by the driver for each driving mode in a vehicle having a plurality of driving modes having different driving force characteristics. An object is to provide an apparatus.

  In order to achieve the above object, a driving force control apparatus for a first vehicle according to the present invention includes a frictional circle limit value setting means for setting a frictional circle limit value based on a frictional force between a tire and a road surface, and a driving force characteristic. A request to set a required driving force based on one selected operation mode and an output request amount detected by an output request amount detecting means for detecting the driver's output request amount. Driving force setting means, tire resultant force setting means for setting tire resultant force based on the longitudinal force and lateral force of the wheel, and friction circle limit value for correcting the friction circle limit value according to the selected operation mode And a control amount setting means for setting a control amount for the drive system by limiting the required driving force set by the required driving force setting means based on the friction circle limit value set by the friction circle limit value correcting means. To have Features.

  The driving force control device for the second vehicle has friction circle limit value setting means for setting a friction circle limit value based on the friction force between the tire and the road surface, and a plurality of operation modes having different driving force characteristics. Request driving force setting means for setting a required driving force based on the selected one of the driving modes and an output request amount detecting means for detecting the output request amount of the driver; Tire resultant force setting means for setting tire resultant force based on force and lateral force; and a first-order lag time constant for converging the required driving force within the friction circle limit value when the tire resultant force exceeds the friction circle limit value The first-order lag time constant setting means for variably setting according to the selected operation mode, and the requested drive set by the requested drive force setting means based on the first-order lag time constant set by the first-order lag time constant setting means Limit power Characterized in that it comprises a control amount setting means for setting a control amount for the drive system.

  According to the present invention, in a vehicle having a plurality of operation modes having different driving force characteristics, one of the magnitude of the friction circle limit value and the length of the return time when the friction circle limit value is exceeded is variable for each operation mode. Since it is set, the driving force corresponding to the drivability requested by the driver can be obtained for each driving mode.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[First Embodiment]
1 to 7 show a first embodiment of the present invention. FIG. 1 is a configuration diagram of the driving force control device, and FIG. 2 is a functional block diagram of the engine control device. In the present embodiment, a four-wheel drive vehicle with a center differential is exemplified as the vehicle.

  As shown in FIG. 1, the vehicle is connected to a meter control device (meter_ECU) 21, an engine control device (E / G_ECU) 22, a transmission control device (through a vehicle communication line 16 such as CAN (Controller Area Network) communication. A control device as a calculation means for controlling the vehicle such as (T / M_ECU) 23 is connected so as to be able to communicate with each other. Each of the ECUs 21 to 23 is mainly composed of a computer such as a microcomputer, and has a well-known CPU, ROM, RAM, and nonvolatile storage means such as an EEPROM.

The meter_ECU 21 controls the entire display of a combination meter (not shown) provided on the instrument panel in front of the driver, and receives a parameter for detecting the driving state of the vehicle and temporarily stores it in the RAM. . On the input side of the meter_ECU 21, there is a mode selection switch 10, a yaw rate sensor 11 for detecting a yaw rate γ acting on the vehicle body, a lateral acceleration sensor 12 for detecting a lateral acceleration Gy (= d ² y / dt ² ) acting on the vehicle body, and the like. It is connected. Further, although not shown, well-known components disposed in the combination meter such as a tachometer, a speed meter, a water temperature meter, a fuel meter, and various warning lamps are connected to the output side. The mode selection switch 10 is an external operation switch for selecting the engine operation mode Dm, and can be arbitrarily operated by the driver. In the present embodiment, there are three types of operation modes Dm, a normal mode Dn, a save mode Ds, and a power mode Dp, corresponding to the operation mode Dm (= Dn, Ds, Dp) selected by the driver. An operation mode signal is output to the E / G_ECU 22. The engine output characteristics of each mode Dn, Ds, Dp will be described later.

  The E / G_ECU 22 mainly controls the operating state of the engine. On the input side, the E / G_ECU 22 is disposed on the input side, such as an engine speed sensor 29 that detects the engine speed Ne from the rotation of the crankshaft, the downstream of the air cleaner, and the like. An intake air amount sensor 30 for detecting an intake air amount Q, an accelerator opening sensor 31 as an output required amount detection means for detecting an accelerator opening θacc that is a driver's required output amount from a depression amount of an accelerator pedal, an intake air Sensors that detect vehicle and engine operating conditions, such as a throttle opening sensor 32 that detects the opening of an electronically controlled throttle valve (not shown) that adjusts the amount of intake air supplied to each cylinder that is interposed in the passage. Is connected. Further, on the output side of the E / G_ECU 22, an injector 36 for injecting a predetermined amount of fuel into the combustion chamber, a throttle actuator 37 for opening / closing an electronically controlled throttle valve, and an ignition plug disposed in each cylinder For example, an igniter 38 that outputs an ignition signal at a predetermined timing is connected to a drive system that controls engine drive.

  The E / G_ECU 22 sets a fuel injection timing and a fuel injection pulse width (pulse time) for the injector 36 and an optimum ignition timing for the igniter 38 based on detection signals from the input sensors. Further, a throttle opening signal is output to the throttle actuator 37 to control the opening of the electronically controlled throttle valve.

  By the way, a plurality of different engine output characteristics (driving force characteristics) are stored in a map format in the non-volatile storage means provided in the E / G_ECU 22. As each engine output characteristic, in this embodiment, there are three kinds of operation modes of a normal mode Dn, a save mode Ds, and a power mode Dp, and the nonvolatile storage means has modes corresponding to these operation modes Dn, Ds, and Dp. Maps Mpn, Mps, and Mpp are stored. As shown in FIG. 7, each of the mode maps Mpn, Mps, and Mpp is a three-dimensional map that stores the target engine torque at each lattice point with the accelerator opening θacc and the engine speed Ne as the lattice axes. Each mode map Mpn, Mps, Mpp is basically selected by operating the mode selection switch 10. That is, the required engine torque calculation unit (described later) of the E / G_ECU 22 selects the normal mode map Mpn when the normal mode Dn is selected as the operation mode Dm based on the mode selection signal output from the mode selection switch 10. When the save mode Ds is selected, the save mode map Mps is selected. When the power mode Dp is selected, the power mode map Mpp is selected.

  Here, engine output characteristics for each of the operation modes Dn, Ds, and Dp set in each mode map Mpn, Mps, and Mpp will be described. As shown in FIG. 7 (a), the normal mode map Mpn is set to a characteristic in which the target engine torque changes almost in proportion to the accelerator opening degree θacc, and the accelerator opening degree θacc is in the vicinity of all steps. The maximum target engine torque at which the electronically controlled throttle valve is fully opened is set.

  In addition, as shown in FIG. 5B, the save mode map Mps suppresses the increase in the target engine torque as compared with the engine output characteristics stored in the normal mode map Mpn described above, and the accelerator is opened. Even when the degree θacc is fully depressed, the electronically controlled throttle valve is not fully opened, and the maximum value of the target engine torque is suppressed. Therefore, when the operation mode Dm is set to the save mode Ds, an increase in engine torque is suppressed as compared with an increase in the accelerator opening θacc. As a result, it is possible to enjoy accelerator work such as depressing the accelerator pedal. In addition to being able to operate economically. Furthermore, since the increase in the target engine torque is suppressed as compared with the increase in the accelerator opening θacc, both easy drive performance and low fuel consumption can be achieved in a balanced manner.

  Further, as shown in FIG. 5C, the power mode map Mpp is set so that the target engine torque changes greatly with respect to the change of the accelerator opening in almost the entire operation region, and the accelerator opening θacc However, the maximum target engine torque at which the electronically controlled throttle valve is fully opened is set near the fully depressed position. Therefore, in the power mode Dp, the target engine torque with emphasis on power is set so as to maximize the potential of the engine in the entire operation region. The details of the engine output characteristics of each operation mode Dm (= Dn, Ds, Dp) are described in Patent Document 1 described above.

  Thus, in the engine torque setting means, when the driver operates the mode selection switch 10 to select one of the modes Dn, Ds, Dp, the corresponding mode maps Mpn, Mps, Mpp are selected and selected. A target engine torque is set based on the mode maps Mpn, Mps, and Mpp. Based on this target engine torque, the valve opening of the electronically controlled throttle valve is controlled to set the engine output as the driving force. Therefore, three different types of accelerator responses can be enjoyed with one vehicle.

  The operation mode Dm can be automatically switched according to the driving conditions of the vehicle. For example, the amount of change per unit time of the accelerator opening θacc during travel is learned, and in an operation region where the accelerator pedal changes greatly, such as uphill travel, the normal mode Dn is automatically switched to the power mode Dp, In an operation region where the amount of change in the accelerator opening θacc is small, such as in urban areas, the normal mode Dn is automatically switched to the save mode Ds.

  Further, the T / M_ECU 23 performs shift control of the automatic transmission. On the input side, the vehicle speed sensor 41 that detects the vehicle speed from the number of rotations of the transmission output shaft, and the inhibitor that detects the range in which the select lever 7 is set. A switch 42, a turbine rotation speed sensor 43 for detecting the rotation speed of the turbine shaft provided in the torque converter, and the like are connected, and a control valve 44 for performing shift control of the automatic transmission and a lock-up clutch are locked up on the output side. A lockup actuator 45 to be operated is connected. The T / M_ECU 23 determines the set range of the select lever based on the signal from the inhibitor switch 42. When the T / M_ECU 23 is set to the D range, the shift signal is output to the control valve 44 according to a predetermined shift pattern. Shift control is performed. This shift pattern is variably set corresponding to the operation modes Dn, Ds, Dp set by the E / G_ECU 22.

  When the lock-up condition is satisfied, a slip lock-up signal or lock-up signal is output to the lock-up actuator 45, and the input / output elements of the torque converter are changed from the converter state to the slip lock-up state or the lock-up state. Switch.

  Further, the operation mode Dm is read also in the driving force control executed by the E / G_ECU 22. In this driving force control, a frictional circle limit value μ_Fzi (where i = front right wheel fr, front left wheel fl, rear right wheel rr, rear left wheel rl) corresponding to the operation mode Dm is set for each wheel. .

  As shown in FIG. 2, the E / G_ECU 22 functions as an engine torque calculation unit 51, a required engine torque calculation unit 52 as a required drive force setting unit, a transmission output torque calculation unit 53, and a total drive as functions for executing driving force control. Force calculating section 54, front / rear ground load calculating section 55, left wheel load ratio calculating section 56, each wheel ground load calculating section 57, each wheel front / rear force calculating section 58, each wheel lateral force calculating section 59 as a lateral force estimating means, friction Each wheel friction circle limit value calculation unit 60 as a circle limit value setting means, each wheel tire resultant force calculation unit 61 as a tire resultant force setting means, each wheel over tire force calculation unit 62, over tire force calculation unit 63, over torque calculation And a control amount calculation unit 65 as a control amount setting means.

  The engine torque calculation unit 51 refers to or calculates the engine torque map with interpolation calculation based on the throttle opening degree θth detected by the throttle opening degree sensor 32 and the engine speed Ne detected by the engine speed sensor 29. Calculate engine torque Teg from the equation. For example, the map stores engine torque obtained in advance through experiments using the throttle opening θth and the engine speed Ne as parameters, and this map is stored as fixed data in the ROM of the E / G_ECU 22.

  Further, the requested engine torque calculation unit 52 reads the operation mode signal output from the meter_ECU 21, the accelerator opening θacc detected by the accelerator opening sensor 31, and the engine speed Ne. First, based on the operation mode signal, a mode map (any of Mpn, Mps, Mpp) corresponding to the selected operation mode Dm (= any of Dn, Ds, Dp) is selected, and the selected mode is selected. The map Mpn, Mps, or Mpp is referenced with interpolation calculation using the engine speed Ne and the accelerator opening θacc as parameters, the target engine torque is specified, and this target engine torque is set as the required engine torque Tdrv.

  The transmission output torque calculation unit 53 includes an engine speed Ne, a speed change signal output from the T / M_ECU 23 (a main speed gear ratio εi indicating the current speed ratio), and a turbine speed signal (turbine speed Nt). The engine torque Teg set by the engine torque calculation unit 51 is read. First, the rotational speed ratio εe of the torque converter is calculated from the ratio between the turbine rotational speed Nt and the engine rotational speed Ne (εe = Nt / Ne). Next, the torque ratio εt of the torque converter is set by referring to the map based on the rotational speed ratio εe and the torque ratio of the torque converter.

Based on these values, the transmission output torque Tt is calculated from the following equation.
Tt = Teg · εt · εi (1)
The total driving force calculation unit 54 reads the transmission output torque Tt obtained by the transmission output torque calculation unit 53 and calculates the total driving force Fx from the following equation.
Fx = Tt · η · if / Rt (2)
Here, η is drive system transmission efficiency, if is the final gear ratio, Rt is the tire radius, and these are all fixed values.

The front / rear ground load calculation unit 55 reads the total driving force Fx calculated by the total driving force calculation unit 54 and, based on the total driving force Fx, calculates the front / rear acceleration (d ² x / dt ² ) as (d ² x / Dt ² ) = (Fx / m). However, m is vehicle mass (fixed value). Based on this longitudinal acceleration (d ² x / dt ² ), the front wheel ground load Fzf and the rear wheel ground load Fzr are calculated from the following equations.
Fzf = Wf − ((m · (d ² x / dt ² ) · h) / L) (3)
Fzr = W−Fzf (4)
Wf is the front wheel static load, h is the height of the center of gravity, L is the wheel base, W is the vehicle weight (= m · G, where G is the gravitational acceleration), and these are fixed values.

The left wheel load ratio calculation unit 56 reads the lateral acceleration signal (lateral acceleration Gy) output from the T / M_ECU 23, and calculates the left wheel load ratio WR_l from the following equation.
WR_l = 0.5- (Gy / G). (H / Ltred) (5)
In addition, Ltred is a tread average value of the front wheel and the rear wheel, and is a fixed value.

Each wheel ground load calculation unit 57 reads the front wheel ground load Fzf, the rear wheel ground load Fzr obtained by the front and rear ground load calculation unit 55, and the left wheel load ratio WR_l calculated by the left wheel load ratio calculation unit 56, and then From the equation, the ground contact load Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) is calculated.
Fzf_l = Fzf · WR_l (6)
Fzf_r = Fzf · (1−WR_l) (7)
Fzr_l = Fzr · WR_l (8)
Fzr_r = Fzr · (1−WR_l) (9)
Each wheel longitudinal force calculation unit 58 reads an engagement torque TLSD for an LSD (Limited Slip Differential) clutch that limits the differential of the center differential set by a center differential device (not shown), and is obtained by the transmission output torque calculation unit 53. The transmission output torque Tt, the total driving force Fx obtained by the total driving force calculation unit 54, and the front wheel grounding load Fzf obtained by the front / rear grounding load calculation unit 55 are read.

Then, the longitudinal force Fxi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) is calculated. When calculating the longitudinal force Fxi of each wheel, first, the front wheel load distribution ratio WR_f is calculated from the following equation.
WR_f = Fzf / W (10)
Next, the minimum front wheel longitudinal torque Tfmin and the maximum front wheel longitudinal torque Tfmax are calculated from the following equations.
Tfmin = Tt · Rf_cd−TLSD (≧ 0) (11)
Tfmax = Tt · Rf_cd + TLSD (≧ 0) (12)
Rf_cd is the base torque distribution of the center differential device.

Next, the minimum front wheel longitudinal force Fxfmin and the maximum front wheel longitudinal force Fxfmax are calculated from the following equations.
Fxfmin = Tfmin · η · if / Rt (13)
Fxfmax = Tfmax · η · if / Rt (14)
Based on these values, state determination is performed as follows.
When WR_f ≦ Fxfmin / Fx, it is assumed that the differential limiting torque is increased on the rear wheel side, and the determination value I = 1.
When WR_f ≧ Fxfmax / Fx, it is assumed that the differential limiting torque is increased on the front wheel side, and the determination value I = 3.
In cases other than the above, it is determined as normal time, and the determination value I = 2.

  Next, the front wheel longitudinal force Fxf corresponding to the determination value I is calculated from the following equation.

When I = 1 Fxf = Tfmin · η · if / Rt (15)
When I = 2 Fxf = Fx.WR_f (16)
When I = 3 Fxf = Fxfmax · η · if / Rt (17)
Then, based on the front wheel longitudinal force Fxf calculated by the equations (15) to (17), the rear wheel longitudinal force Fxr is calculated from the following equation.
Fxr = Fx−Fxf (18)
Using the front wheel longitudinal force Fxf and the rear wheel longitudinal force Fxr, the longitudinal force Fxi of each wheel is calculated from the following equation.

Fxf_l = Fxf / 2 (19)
Fxf_r = Fxf_l (20)
Fxr_l = Fxr / 2 (21)
Fxr_r = Fxr_l (22)
Note that the calculation of the front-rear force of each wheel shown in the present embodiment is merely an example, and can be appropriately selected depending on the drive type / drive mechanism of the vehicle.

  Each wheel lateral force calculation unit 59 reads the lateral acceleration Gy, the yaw rate signal (yaw rate γ) output from the meter_ECU 21, and the left wheel load ratio WR_l obtained by the left wheel load ratio calculation unit 56. First, the front wheel lateral force Fyf and the rear wheel lateral force Fyr are calculated from the following equations.

Fyf = (Iz · (dγ / dt) + m · Gy · Lr) / L (23)
Fyr = (− Iz · (dγ / dt) + m · Gy · Lf) / L (24)
Here, Iz is the yaw moment of inertia of the vehicle, Lr is the distance between the rear axis and the center of gravity, and Lf is the distance between the front axis and the center of gravity, both of which are fixed values.

  Next, the lateral force Fyi of each wheel (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) is calculated from the following formula based on the front wheel lateral force Fyf and the rear wheel lateral force Fyr. To do.

Fyf_l = Fyf · WR_l (25)
Fyf_r = Fyf. (1-WR_l) (26)
Fyr_l = Fyr · WR_l (27)
Fyr_r = Fyr · (1-WR_l) (28)
Each wheel friction circle limit value calculation unit 60 calculates a friction circle limit value μ_Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r). The calculation of the friction circle limit value μ_Fzi of each wheel in each wheel friction circle limit value calculation unit 60 is obtained in the friction circle limit value calculation routine shown in FIG.

  In this routine, first, the road surface friction coefficient μ is read in step S1. The road surface friction coefficient μ is determined by a road surface μ calculation unit (not shown) provided in the E / G_ECU 22 and is output to each wheel friction circle limit value calculation unit 60 as a road surface friction coefficient signal. Here, a method of setting the road surface friction coefficient μ in the road surface μ calculation unit will be briefly described. The method of setting the road surface friction coefficient μ is performed based on the technique disclosed in Japanese Patent Laid-Open No. 8-2274 previously filed by the present applicant. That is, first, the cornering power of the front and rear wheels is extended to a non-linear range and estimated based on the equation of motion of the lateral movement of the vehicle based on the steering angle, the vehicle speed, and the actual yaw rate. Then, the road surface friction coefficient μ is set from the ratio of the estimated front and rear wheel cornering power to the front and rear wheel equivalent cornering power on the high μ road (μ = 1.0). The method for setting the road surface friction coefficient μ is not limited to the technique disclosed in the publication, but is disclosed in another method, for example, Japanese Patent Application Laid-Open No. 2000-71968 filed by the applicant. You may obtain | require by the method to disclose or may obtain | require for every wheel from the slip ratio generate | occur | produced in each wheel.

Next, the process proceeds to step S2, and the ground load Fzi (i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) output from each wheel ground load calculation unit 57 is read. . In step S3, based on the road surface friction coefficient μ and the contact load Fzi of each wheel, the standard friction circle limit value Sμ_Fzi of each wheel (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l) , Rear right wheel r_r) is set.
Sμ_Fzi = μ · Fzi (29)
Then, it progresses to step S4, the operation mode signal (operation mode Dm) output from meter_ECU21 is read, and the operation mode Dm currently set is investigated by step S5, S6. When the current operation mode of Dm = Dn is the normal mode Dn, the process proceeds from step S5 to step S7, and the standard friction circle limit value Sμ_Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, At the rear right wheel r_r), the friction circle limit value μ_Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) is set (μ_Fzi ← Sμ_Fzi), and the routine is exited. Note that the processing in step S7 corresponds to the frictional circle limit value correcting means of the present invention.

  Further, when the current operation mode of Dm = Ds is the save mode Ds, the process proceeds to step S8 through step S5 and step S6, and the save mode correction value αs (where 0.5 <αs <1.0 is added to the standard friction circle limit value Sμ_Fzi). ) Is set to the friction circle limit value μ_Fzi (μ_Fzi ← αs · Sμ_Fzi), and the routine is exited.

  Further, when the current operation mode of Dm = Dp is the power mode Dp, the process proceeds to step S9 through step S5 and step S6, and the power mode correction value αp (where 1.0 <αp <1.5 is set to the standard friction circle limit value Sμ_Fzi). ) Is set to the friction circle limit value μ_Fzi (μ_Fzi ← αp · Sμ_Fzi), and the routine is exited.

  As shown in FIG. 4, the friction circle limit value μ_Fzi is a radius of a circle representing a limit that can control the motion performance of the vehicle with the wheel holding the gripping force. The size of the friction circle limit value μ_Fzi is It represents the maximum value of the friction force generated between the road surface. The frictional force of the tire is a combined force of the force in the traveling direction (driving force or braking force) and the frictional force in the lateral direction (right direction or left direction), and the frictional force in either direction is 100%. That is, when it coincides with the size of the friction circle limit value μ_Fzi, the frictional force in the other direction becomes zero. The braking force is in the opposite direction to the driving force.

  In this embodiment, the friction circle limit value μ_Fzi is set for each operation mode Dm (= Dn, Ds, Dp), and the friction circle limit value μ_Fzi set when the normal mode Dn is selected is set as a standard value, and saved. The friction circle limit value μ_Fzi set when the mode Ds is selected is smaller than the standard value, and the friction circle limit value μ_Fzi set when the power mode Dp is selected is larger than the standard value. Further, as shown in FIG. 5, the frictional circle limit value μ_Fzi is set for each wheel, and, as will be described later, tire resultant force F_i for each wheel (where i = front left wheel fl, front right wheel fr, rear Compared with left wheel rl and rear right wheel rr).

Further, each wheel tire resultant force calculation unit 61 includes the wheel longitudinal force Fxi obtained by each wheel longitudinal force calculation unit 58 and the wheel lateral force Fyi obtained by each wheel lateral force calculation unit 59 (however, i = Front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r), the tire resultant force F_i of each wheel is calculated from the square sum square root expressed by the following equation (see FIG. 6).
F_i = (Fxi ² + Fyi ² ) ^1/2 (30)
Further, each wheel over-tyre force calculating unit 62 includes the friction circle limit value μ_Fzi of each wheel obtained by each wheel friction circle limit value calculating unit 60 and the tire resultant force F_i of each wheel obtained by each wheel tire resultant force calculating unit 61. Based on the above, the over-tyre force ΔF_i of each wheel is calculated from the following equation.
ΔF_i = F_i−μ_Fzi (31)
As shown in FIG. 5, the over-tyre force ΔF_i is a simple difference between the tire resultant force F_i and the friction circle limit value μ_Fzi, and therefore when the tire resultant force F_i is within the friction circle limit value μ_Fzi, in other words, the friction circle When the tire resultant force F_i has a margin with respect to the limit value μ_Fzi, the value is negative. Since the friction circle limit value μ_Fzi at this time is set for each operation mode Dm (= Dn, Ds, or Dp), as shown in FIG. 6, for example, the friction circle limit in the normal mode Dn is used. Even if the overtire force ΔF_i is a positive value (F_i> μ_Fzi) at the value μ_Fzi, the overtire force ΔF_i may be a negative value (F_i <μ_Fzi) at the friction circle limit value μ_Fzi in the power mode Dp. Alternatively, even if the overtire force ΔF_i is a negative value (F_i <μ_Fzi) in the friction circle limit value μ_Fzi in the normal mode Dn, the overtire force ΔF_i is a positive value (F_i) in the friction circle limit value μ_Fzi in the save mode Ds. > Μ_Fzi).

Further, the over-tyre force calculating unit 63 calculates the over-tyre force ΔF_i of each wheel obtained by each wheel over-tyre force calculating unit 62 (where i = front left wheel fl, front right wheel fr, rear left wheel rl, rear right wheel rr ), And this value is set as the overtire force Fover.
Fover = ΔF_fl + ΔF_fr + ΔF_rl + ΔF_rr (32)
For example, when the average over tire force ΔF_i of all the wheels is a negative value, the over tire force Fover is a negative value. When the average is a positive value, the over tire force Fover is a positive value. In this case, the over tire force ΔF_i (i = front left wheel fl, front right wheel fr, rear left wheel rl, rear right wheel rr) having the largest value is set as the over tire force Fover. You may make it do. Alternatively, the average value of the over tire force ΔF_i of each wheel may be set as the over tire force Fover.

The overtorque calculator 64 calculates the overtorque Tover from the following equation based on the overtire force Fover obtained by the overtire force calculator 63.
Tover = Fover · Rt / εt / εi / η / if (33)
Here, η is drive system transmission efficiency, if is the final gear ratio, Rt is the tire radius, and these are all fixed values. Further, εt is the torque ratio of the torque converter, and is obtained by referring to the map based on the rotational speed ratio e (= Nt / Ne) of the torque converter and the torque ratio of the torque converter. When the overtorque Tover is a positive value (negative value), the overtire force Fover is also a positive value (negative value).

The control amount calculation unit 65 is a new driving force control amount based on the required engine torque Tdrv calculated by the required engine torque calculation unit 52 and the overtorque Tover calculated by the overtorque calculation unit 64 from the following equation. The output torque Treq is calculated.
・ Tover <0, that is, when the tire resultant force F_i is smaller than the friction circle limit value μ_Fzi,
Treq = Tdrv (34)
・ Tover ≧ 0, that is, when the tire resultant force F_i is larger than the friction circle limit value μ_Fzi,
Treq = (Tdrv−Tover) (35)
The output torque Treq is output to a throttle actuator that drives an electronically controlled throttle valve. As a result, the required engine torque Tdrv is always limited to be within the friction circle limit value μ_Fzi. At this time, when the operation mode Dm is set to the save mode Ds, the friction circle limit value μ_Fzi is smaller than the friction circle limit value μ_Fzi in the normal mode Dn as shown by the broken line in FIG. It is reduced in appearance by the proportion. Therefore, even if the driver prefers the save mode Ds in which the driving force is suppressed, even if the accelerator pedal is fully depressed, the grip force of the wheel is sufficiently maintained and no slipping occurs, so the drivability according to the driver's request is provided. Obtainable.

  On the other hand, when the operation mode Dm is set to the power mode Dp, the friction circle limit value μ_Fzi is greater than the friction circle limit value μ_Fzi in the normal mode Dn, as shown by a one-dot chain line in FIG. Since it is enlarged by the proportion, it is possible to obtain drivability according to the demand of the driver who prefers driving with emphasis on power, although some slip occurs.

[Second Embodiment]
8 to 11 show a second embodiment of the present invention. FIG. 8 is a functional block diagram of the engine control apparatus. In the first embodiment described above, the friction circle limit value μ_Fzi is variably set according to the engine operation mode Dm. However, in this embodiment, the friction circle limit value μ_Fzi is a standard value, and the tire resultant force F_i is the friction circle. The required engine torque Tdrv is not limited until the limit value μ_Fzi is exceeded, and is set for each engine operation mode Dm (= Dn, Ds, Dp) from when the tire resultant force F_i exceeds the friction circle limit value μ_Fzi. The tire resultant force F_i is returned to the friction circle limit value μ_Fzi with the first-order lag time constant T (= Tn, Ts, Tp).

  In the functional block diagram of the engine control device shown in FIG. 8, the calculation units that perform processing different from the processing of the first embodiment described above are each wheel friction circle limit value calculation unit 60 and the control amount calculation unit 65, and others In the calculation units 51 to 59 and 61 to 64, processing common to the first embodiment is executed. Therefore, the description about the calculating part which performs the process common to 1st Embodiment is abbreviate | omitted.

  The friction circle limit values μ_Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) calculated by the wheel friction circle limit value calculation unit 60 are shown in FIG. It is obtained according to the friction circle limit value calculation routine.

  In this routine, first, the road surface friction coefficient μ is read in step S11. Since the method for obtaining the road surface friction coefficient μ has already been described, the description thereof will be omitted.

Next, in step S12, the ground load Fzi (i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, rear right wheel r_r) output from each wheel ground load calculation unit 57 is read. In step S13, based on the road surface friction coefficient μ and the contact load Fzi of each wheel, the friction circle limit value μ_Fzi (where i = front left wheel f_l, front right wheel f_r, rear left wheel r_l, Set the rear right wheel (r_r) and exit the routine.
μ_Fzi = μ · Fzi (29 ′)
Further, the control amount calculator 65 calculates the engine output torque Treq according to the control amount calculation routine shown in FIG. In this routine, first, in step S21, it is checked whether or not the overtorque Tover obtained by the overtorque calculator 64 indicates a positive value. If the overtorque Tover is negative (Tover <0), the process branches to step S22. The requested engine torque Tdrv obtained by the requested engine torque calculation unit 52 is used to set the output torque Treq (Treq ← Tdrv), and the routine is exited.

  If the overtorque Tover shows a positive value (Tover ≧ 0), the process proceeds to step S23, and the currently set engine operation mode Dm (= Dn, Ds, or Dp) is read. In step S24, a first-order lag time constant T corresponding to the set operation mode Dm (= Dn, Ds, or Dp) is set. As shown in FIG. 11, the first-order lag time constant T has the normal mode time constant Tn when the operation mode Dm is set to the normal mode Dn as a standard value, and the operation mode Dm is set to the save mode Ds. The save mode time constant Ts is set shorter than the normal mode time constant Tn, and the power mode time constant Tp when the operation mode Dm is set to the power mode Dp is smaller than the normal mode time constant Tn. It is set long (Ts <Tn <Tp).

Thereafter, the process proceeds to step S25, and the output torque Treq is calculated from the following equation.
Treq ← (k / (1 + T · s)) · (Tdrv−Tover) (35 ′)
Here, K is a proportionality constant and is set to K = 1 in this embodiment. S is a Laplace operator. The processes in steps S24 and S25 correspond to the first-order lag time constant setting means of the present invention.

  The output torque Treq is output to a throttle actuator that drives an electronically controlled throttle valve. As a result, as shown in FIG. 11, when the tire resultant force F_i exceeds the frictional circle limit value μ_Fzi, and the engine operating mode Dm at that time is set to the normal mode Dn, The tire resultant force F_i is converged to the frictional circle limit value μ_Fzi with a delay according to the time constant Tn. Further, when the operation mode Dm is set to the save mode Ds, as shown by the alternate long and short dash line, the save mode time constant Ts is set shorter than the normal mode time constant Tn of the normal mode Dn. Is quickly converged to the friction circle limit value μ_Fzi. When the operation mode Dm is set to the power mode Dp, as indicated by the broken line, the power mode time constant Tp is set to be longer than the normal mode time constant Tn of the normal mode Dn. Is gradually converged with respect to the friction circle limit value μ_Fzi.

  As a result, when the engine operation mode Dm is set to the save mode Ds, when the tire resultant force F_i exceeds the friction circle limit value μ_Fzi, the tire resultant force F_i is relatively early with respect to the friction circle limit value μ_Fzi. In other words, since the engine output is limited before slip actually occurs, slip does not occur and drivability according to the request of the driver who prefers the save mode Ds can be obtained. On the other hand, when the driving mode Dm is set to the power mode Dp, when the tire resultant force F_i exceeds the friction circle limit value μ_Fzi, compared to the case where the driving mode Dm is set to the normal mode Dn, this tire resultant force Since F_i converges relatively gently with respect to the frictional circle limit value μ_Fzi, although some slip occurs, drivability according to the demands of the driver who prefers driving with emphasis on power can be obtained.

The present invention is not limited to the above-described embodiments. For example, the operation mode of the engine is not limited to the three modes described above, and may have two modes or four or more modes. In the first embodiment, the friction circle limit value μ_Fzi corresponding to each mode is set with the friction circle limit value μ_Fzi of a mode suitable for normal operation (normal mode Dn) as a standard. In the second embodiment, the first-order delay time constant T corresponding to each mode is set as a standard, and the time constant T (normal mode time constant Tn) in the operation mode (normal mode Dn) suitable for normal operation is set as a standard.

  In each of the above-described embodiments, when the tire resultant force F_i exceeds the frictional circle limit value μ_Fzi, the opening of the electronically controlled throttle valve that is the drive system is controlled to limit the engine output. The engine output may be limited by fuel cut or ignition timing control. Further, the driving force characteristic is not limited to the engine output characteristic, and may be a shift characteristic of an automatic transmission.

1 is a configuration diagram of a driving force control apparatus according to a first embodiment. Same as above, functional block diagram of engine control device The flowchart showing the friction circle limit value calculation routine Explanatory drawing of friction circle limit value Same as above, explanatory diagram of friction circle limit value set for each wheel Explanatory drawing showing the relationship between tire resultant force and friction circle limit value (A) is a conceptual diagram of a normal mode map, (b) is a conceptual diagram of a save mode map, and (c) is a conceptual diagram of a power mode map. Functional block diagram of an engine control apparatus according to the second embodiment The flowchart showing the friction circle limit value calculation routine The flowchart showing the control amount calculation routine Same as above, explanatory diagram showing first-order lag time constant set for each operation mode

Explanation of symbols

10: Mode selection switch,
11 ... Yaw rate sensor,
12 ... Lateral acceleration sensor,
31 ... accelerator opening sensor,
52 ... Requested engine torque calculation unit,
57: Each wheel ground load calculation unit,
60: Each wheel friction circle limit value calculation unit,
61. Each wheel tire resultant force calculation unit,
63: Over-tyre force calculator,
64 ... Overtorque calculation unit,
65 ... control amount calculation unit,
Teg ... engine torque,
Treq ... Output torque,
αp: power mode correction value,
αs: Save mode correction value,
μ_Fzi ... Friction circle limit value,
μ: Road friction coefficient,
Dn ... Normal mode
Dp ... Power mode,
Ds ... save mode,
F_i ... tire resultant force,
Fxi ... longitudinal force,
Fyi ... Lateral force,
Fzi ... contact load,
Gy ... Lateral acceleration,
Mpn ... Normal mode map,
Mpp ... Power mode map,
Mps ... Save mode map,
Sμ_Fzi ... Standard friction circle limit value,
T: Time constant,
Tdrv: Required engine torque,
Treq: Output torque,
Tn: Normal mode time constant,
Tp: Power mode time constant,
Ts ... Save mode time constant

Claims (6)

Friction circle limit value setting means for setting a friction circle limit value based on the frictional force between the tire and the road surface;
It has a plurality of operation modes having different driving force characteristics, and the required driving force is calculated based on the selected one operation mode and the output request amount detected by the output request amount detection means for detecting the driver's output request amount. Required driving force setting means to be set;
Tire resultant force setting means for setting the tire resultant force based on the longitudinal force and lateral force of the wheel;
Friction circle limit value correcting means for correcting the friction circle limit value according to the selected operation mode;
Control amount setting means for setting a control amount for the drive system by limiting the required driving force set by the required driving force setting means based on the friction circle limit value set by the friction circle limit value correcting means. A vehicle driving force control device. Friction circle limit value setting means for setting a friction circle limit value based on the frictional force between the tire and the road surface;
It has a plurality of operation modes having different driving force characteristics, and the required driving force is calculated based on the selected one operation mode and the output request amount detected by the output request amount detection means for detecting the driver's output request amount. Required driving force setting means to be set;
Tire resultant force setting means for setting the tire resultant force based on the longitudinal force and lateral force of the wheel;
At the time of the primary delay, the primary delay time constant for converging the required driving force within the friction circle limit value when the tire resultant force exceeds the friction circle limit value is variably set according to the selected operation mode. Constant setting means;
Control amount setting means for limiting the required driving force set by the required driving force setting means based on the first order delay time constant set by the first order delay time constant setting means and setting a control amount for the drive system. A vehicle driving force control device. The operation mode has at least a normal mode suitable for normal operation and a save mode suitable for economical operation,
When the normal mode is selected as the operation mode, the friction circle limit value correcting means sets the friction circle limit value set by the friction circle limit value setting means as a current friction circle limit value, and 2. The vehicle driving force control apparatus according to claim 1, wherein when the save mode is selected as the operation mode, the friction circle limit value set by the friction circle limit value setting means is corrected to a small value. The operation mode has at least a normal mode suitable for normal operation and a power mode suitable for operation focusing on power,
When the normal mode is selected as the operation mode, the friction circle limit value correcting means sets the friction circle limit value set by the friction circle limit value setting means as a current friction circle limit value, and 4. The vehicle driving force control according to claim 1, wherein when the power mode is selected as the operation mode, the friction circle limit value set by the friction circle limit value setting means is corrected to a large value. apparatus. The operation mode has at least a normal mode suitable for normal operation and a save mode suitable for economical operation,
The first-order lag time constant setting means sets a first-order lag time constant shorter than the first-order lag time constant set in the normal mode when the save mode is selected as the operation mode. 3. The vehicle driving force control device according to 2. The operation mode has at least a normal mode suitable for normal operation and a power mode suitable for operation focusing on power,
The first-order lag time constant setting means sets a first-order lag time constant longer than the first-order lag time constant set in the normal mode when the power mode is selected as the operation mode. The vehicle driving force control device according to 2 or 5.

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