JP2008230553A - Understeer suppression unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an understeer suppression unit for accurately suppressing understeer by preventing the decrease of lateral force due to excess braking force in the case of detecting the understeer of a vehicle, and decelerating a vehicle by performing shift-down and prime mover output reduction. <P>SOLUTION: This understeer suppression unit is provided with an electric power steer control unit 1 for detecting understeer; a prime mover control unit 4 for controlling a prime mover output from a prime mover; and a transmission control unit 3 for controlling the transmission of the prime mover output to a wheel and a gear ratio. When the understeer of the vehicle is detected by the electric power steer control unit 1, a gear ratio by the transmission control unit 3 is changed to a low speed side, and the prime mover output by the prime mover control means is reduced. The prime mover control unit 4 and the transmission control unit 3 control the prime mover output or the transmission of the prime mover output so that the driving force deviation of the wheel or the wheel speed deviation of the wheel before and after the change of the gear ratio can be reduced when the gear ratio is changed by the transmission control unit 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  This invention detects understeer of the vehicle by detecting understeer of the vehicle (a phenomenon in which the lateral grip of the front tire reaches the limit and causes the vehicle to slip excessively) that occurs when the steering wheel is overcut on a slippery road surface. With regard to the device, in particular, understeering is performed by automatically changing the transmission gear ratio to the low speed side (hereinafter referred to as “shift down”) and reducing the motor output by the motor controller and decelerating the vehicle. It is related with the technique which suppresses.

  Conventionally, an understeer suppression device that detects understeer of a vehicle, automatically downshifts by a transmission controller and reduces motor output by a prime mover controller, and suppresses understeer by decelerating the vehicle has been proposed. (For example, refer to Patent Document 1).

  In general, the force that can be generated in a vehicle tire is expressed using a friction circle as shown in FIG. FIG. 9 is an explanatory diagram showing the force that can be generated in the tire. In FIG. 9, the horizontal axis indicates the lateral force, the vertical axis indicates the driving force, the negative axis indicates the braking force, and the radius of the friction circle. Indicates the maximum friction force (determined by the vertical load and the road surface friction coefficient) that can be generated between the tire and the road surface.

  As is clear from FIG. 9, the frictional force used while the vehicle is traveling is represented by the vector sum of the driving braking force along the traveling direction and the lateral force perpendicular to the traveling direction. However, when both the driving braking force and lateral force are large, the driving braking force has priority over the lateral force, and the vector sum is always within the friction circle (the maximum value of the vector sum is limited to the radius of the friction circle). )

On the other hand, FIG. 10 is an explanatory diagram showing a friction circle at the time of understeering, and shows a front wheel friction circle when the front wheel drive vehicle during cornering is understeering.
During turning, the driving force for forward movement and the lateral force for turning are generated at the same time. However, as described above, the driving braking force has priority over the lateral force, or the vector sum Because the maximum value is limited to the radius of the friction circle (that is, even if the driving braking force is zero, the maximum lateral force is limited to the radius of the friction circle), the lateral force required for turning is sufficient. It is in a state that has not occurred.

  In the above-described conventional device, understeer of the vehicle is detected, downshifting and motor output reduction are performed, and understeer is suppressed by decelerating the vehicle. However, if excessive braking force is generated from the state of FIG. Since the braking force is prioritized over the force, as shown in FIG. 11, the lateral force may further decrease, and as a result, understeer may be promoted. Although an example of a front-wheel drive vehicle is shown here, in the case of a rear-wheel drive vehicle as well, if excessive braking force is generated in the same manner, the lateral force of the rear wheel is reduced, and oversteer can be induced. There is sex.

  The above-described understeering and oversteering mainly occur during downshifting. Generally, at the time of downshifting, the prime mover rotational speed rapidly increases due to a change in the gear ratio, but the inertia torque when the prime mover rotational speed increases acts on the wheels as a rapid and large braking force. However, even if the prime mover output is reduced while the gear ratio is on the high speed side, sufficient braking force cannot be obtained. Therefore, it is necessary to reduce the prime mover output after changing the gear ratio to the low speed side.

JP 2003-31465 A

  In the conventional understeer suppression device, since understeer is detected by detecting the understeer of the vehicle, downshifting and reducing the motor output and decelerating the vehicle, for example, excessive braking force is generated from the state of FIG. Then, since the braking force has priority over the lateral force, the lateral force is further reduced as shown in FIG.

  The present invention has been made to solve the above-described problem, and detects the understeer of the vehicle and appropriately controls the transmission of the prime mover output or the prime mover output when the vehicle is decelerated by shifting down and reducing the prime mover output. Accordingly, an object of the present invention is to obtain an understeer suppressing device that can prevent a decrease in lateral force due to an excessive braking force and accurately suppress understeer.

  An understeer suppressing device according to the present invention includes an understeer detecting means for detecting understeer of a vehicle, a prime mover control means for controlling a prime mover output from the prime mover of the vehicle, and a transmission for controlling transmission of the prime mover output to the wheels of the vehicle and a transmission gear ratio. And an understeer suppression device that changes the gear ratio by the transmission control means to a low speed side when the understeer of the vehicle is detected by the understeer detection means, and reduces the prime mover output by the prime mover control means, The prime mover control means or the transmission control means controls the prime mover output so that the wheel driving force deviation or the wheel speed deviation before and after the change of the speed ratio is reduced or the prime mover is changed when the speed ratio is changed by the transmission control means. To output wheel And it controls the transmission.

  According to the present invention, it is possible to prevent the occurrence of excessive braking force at the time of downshifting and accurately suppress understeer.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a schematic configuration of an understeer suppressing device according to Embodiment 1 of the present invention.
In FIG. 1, the understeer suppression device includes an electric power steering controller (understeer detection means) 1, an understeer suppression controller 2, a transmission controller (transmission control means) 3, and a prime mover controller (prime mover control means) 4. It has. Each of the controllers 1 to 4 is connected to a communication bus (for example, CAN), and can perform message communication with each other.

  An electric power steering controller (hereinafter abbreviated as “electric power steering controller”) 1 detects understeer of a vehicle (not shown). The prime mover controller 4 controls the prime mover output from the prime mover of the vehicle, and the transmission controller 3 controls the transmission of the prime mover output to the wheels of the vehicle and the gear ratio.

The understeer suppression controller 2 that constitutes the main part of the understeer suppression device changes the gear ratio by the transmission controller 3 to the low speed side when the electric power steering controller 1 detects understeer of the vehicle. 4 to reduce the motor output.
The prime mover controller 4 or the transmission controller 3 controls the prime mover output so that the wheel driving force deviation or the wheel speed deviation before and after the change of the gear ratio is reduced when the gear ratio is changed by the transmission controller 3. Or control the transmission of prime mover output.

Next, the operation according to the first embodiment of the present invention shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a timing chart for explaining the operation procedure according to the first embodiment of the present invention. The understeer suppression controller 2, the transmission controller 3 and the prime mover controller 4 according to the detection result of the electric power steering controller 1 are shown in FIG. The operation flow is shown.
In the first embodiment of the present invention, the electric power steering controller 1, the understeer suppression controller 2, the transmission controller 3, and the prime mover controller 4 operate according to the timing chart shown in FIG.

In FIG. 2, first, the electric power steering controller 1 determines whether or not the vehicle is understeered, and the determination result is transmitted via the communication bus to the understeer suppression controller 2, the transmission controller 3, and the prime mover controller. 4 (step ST-1).
The understeer suppression controller 2 does not execute any processing until the electric power steering controller 1 transmits an understeer signal, and the transmission controller 3 performs normal processing (accelerator pedal depression amount, vehicle speed, etc.). And the prime mover controller 4 performs normal processing (primary motor output control according to the amount of depression of the accelerator pedal, the state of the prime mover, etc.).

When it is detected from the electric power steering controller 1 that understeer has been detected, the processing of the understeer suppression controller 2, the transmission controller 3, and the prime mover controller 4 is switched to deceleration processing for understeer suppression.
First, the transmission controller 3 transmits the current shift speed (gear ratio) Gr to the understeer suppression controller 2 (step ST-2), and the prime mover controller 4 sets the current prime mover rotational speed Ne to the understeer suppression controller. 2 (step ST-3).

  When receiving the current gear ratio Gr and prime mover rotational speed Ne, the understeer suppression controller 2 determines whether it is necessary to perform a downshift. For example, when the gear ratio Gr exceeds a predetermined value G1 (Gr> G1), the shift down to the predetermined value G2 is performed, and when the gear ratio Gr is equal to or less than the predetermined value G1 (Gr ≦ G1), the shift down is performed. Is determined to be unnecessary (step ST-4). Here, the transmission gear ratio Gr is the output rotational speed Ne2 / input rotational speed Ne1 of the transmission as viewed from the prime mover side, and becomes a smaller value as the speed decreases.

  If it is determined in step ST-4 that a downshift is to be performed, the understeer suppression controller 2 proceeds to step ST-5 and calculates the target rotational speed Neo of the prime mover. If it is determined not to execute, the process proceeds to step ST-15, where an output reduction instruction is transmitted to instruct only reduction of the motor output.

The understeer suppression controller 2 controls the rotational speed of the prime mover, for example, in order to reduce the change in the wheel driving force and the wheel speed before and after the downshift is performed when it is determined that the downshift is executed in step ST-4. .
Normally, at the time of downshifting, the prime mover rotational speed Ne rapidly increases due to the change in the gear ratio Gr, and the inertia torque at this time acts on the wheels as a large braking force. Therefore, before the downshift (after disengaging the transmission and before re-engaging), the prime mover rotation after the downshift is performed (after the transmission is re-coupled) by increasing the prime mover rotational speed in advance. The increase in speed Ne is prevented.

  Here, the target rotational speed Neo is calculated as shown in the following equation (1) using the transmission gear ratio Gr, the prime mover rotational speed Ne, and the downshift destination transmission gear ratio (predetermined value) G2 (step ST-5). .

Next, the understeer suppression controller 2 transmits an instruction to disengage the transmission (transmission disengagement instruction) to the transmission controller 3 (step ST-6).
The engaged / disengaged state of the transmission is a state whether or not the motor output is transmitted to the wheels. For example, whether or not a clutch installed between the motor and the transmission is released. Alternatively, it is determined by whether or not a general automatic transmission mechanism is in a state called neutral. When the transmission is engaged, the prime mover output is transmitted to the wheels, and when the transmission is disengaged, the prime mover output is not transmitted to the wheels.

  When the transmission controller 3 receives the transmission non-engagement instruction, the transmission controller 3 performs a process of bringing the transmission into a non-engagement state (step ST-7). The transmission disengagement completion is transmitted (step ST-8).

When the understeer suppression controller 2 receives the transmission disengagement completion, the understeer suppression controller 2 transmits the target rotational speed Neo to the prime mover controller 4 to instruct the prime mover rotational speed Ne to coincide with the target rotational speed Neo (step). ST-9).
Thus, the prime mover controller 4 performs a Ne matching process for matching the prime mover rotational speed Ne with the target rotational speed Neo (step ST-10), and the rotational speed deviation ΔNe between the prime mover rotational speed Ne and the target rotational speed Neo is predetermined. If it falls within the range, the coincidence of the motor rotational speed Ne is transmitted to the understeer suppression controller 2 (step ST-11).
Since the transmission is in the disengaged state in the above-described step ST-7, the wheel driving force and the wheel speed are not changed by the change in the rotational speed of the prime mover here.

  When the understeer suppression controller 2 receives the coincidence of the prime mover rotational speed Ne with the target rotational speed Neo, the understeer suppression controller 2 instructs the transmission controller 3 to shift down (step ST-12). The transmission controller 3 changes the gear ratio to a predetermined value G2, and further performs a process for bringing the transmission into an engaged state (step ST-13), and transmits a downshift completion to the understeer suppression controller 2 (step ST-). 14).

Upon receiving the downshift completion from the transmission controller 3, the understeer suppression controller 2 instructs the prime mover controller 4 to reduce the prime mover output (step ST-15).
At this time, if the prime mover is an internal combustion engine, the prime mover controller 4 reduces the output by suppressing the supply air amount and the fuel amount or changing the ignition timing. If the prime mover is an electric motor, The output is reduced by, for example, suppressing the supply current to (step ST-16).
The above steps ST-1 to ST-16 are deceleration processing for suppressing understeer.

  In addition, in the middle of steps ST-1 to ST-16, or in step ST-17 after step ST-16, when transmitting that the electric power steering controller 1 is not understeer, the understeer suppression controller 2 performs processing. The transmission controller 3 and the prime mover controller 4 return to normal processing.

  Next, the electric power steering controller (understeer detection means) 1 used in Embodiment 1 of the present invention will be described in detail with reference to FIGS. Since the transmission controller 3 and the prime mover controller 4 are mounted on a general vehicle, a detailed description thereof will be omitted.

FIG. 3 is a block diagram showing a specific example of the electric power steering controller 1 used in Embodiment 1 of the present invention, and FIG. 4 is a flowchart showing the operation of the electric power steering controller 1. Here, only the portion related to understeer detection is shown, and the portion related to general steering assist torque control is not shown.
FIG. 5 is an explanatory diagram showing the relationship between the steering angle θh and the understeer state (horizontal axis), the standard road surface reaction torque Torig_ref, the road surface reaction torque and the yaw rate (vertical axis).

  In FIG. 3, the electric power steering controller 1 includes various sensors including a steering angle sensor 11, a vehicle speed sensor 12, a steering torque sensor 13, a motor current sensor 14, and a motor rotation speed sensor 15, a standard road surface reaction force torque calculator (standard). A road surface reaction force torque calculation means) 16, an estimated road surface reaction torque calculator (estimated road surface reaction torque calculation means) 17 and an understeer determination unit 18, and an electric motor of a steering assist torque control system (electric power steering). (Not shown). The various sensors 11 to 15 are provided in association with a vehicle steering system (not shown) including an electric power steering device.

A steering angle sensor 11 detects a steering angle θh of a handle (not shown) operated by a driver of the vehicle, and a vehicle speed sensor (vehicle speed detection means) 12 detects a vehicle speed V of the vehicle, and a steering torque sensor (steering). (Torque detection means) 13 detects a steering torque Ts applied to the steering wheel by the driver.
A motor current sensor (motor current detection means) 14 detects a motor current Imtr flowing in the electric motor, and a motor rotation speed sensor (motor rotation speed detection means) 15 detects a motor rotation speed ωmtr of the electric motor.

The steering angle θh and the vehicle speed V from the steering angle sensor 11 and the vehicle speed sensor 12 are input to the reference road surface reaction force torque calculator 16.
The vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr from the vehicle speed sensor 12, the steering torque sensor 13, the motor current sensor 14, and the motor rotation speed sensor 15 are input to the estimated road surface reaction force torque calculator 17. .

The reference road surface reaction torque calculator 16 calculates a reference road surface reaction torque Talign_ref based on the steering angle θh and the vehicle speed V, and inputs it to the understeer determination unit 18.
The estimated road surface reaction force torque calculator 17 calculates an estimated road surface reaction force torque Talign_est based on the vehicle speed V, the steering torque Ts, the motor current Imtr, and the motor rotation speed ωmtr and inputs the calculated road surface reaction force torque Talign_est to the understeer determination unit 18.

The road surface reaction force torque is a torque that attempts to return the tire in a straight direction when the steering wheel is steered.
The understeer determination unit 18 determines whether or not the vehicle is understeer based on a comparison between the reference road surface reaction force torque Talign_ref and the estimated road surface reaction force torque Talign_est, and outputs an understeer determination result.

Hereinafter, the operation of the electric power steering controller 1 will be described with reference to FIGS. 4 and 5. The electric power steering controller 1 periodically executes the operation flow of FIG.
In FIG. 4, first, the steering angle sensor 11 detects the steering angle θh (step S1), the vehicle speed sensor 22 detects the vehicle speed V (step S2), and the steering torque sensor 13 detects the steering torque Ts (step S3). ), The motor current sensor 14 detects the motor current Imtr (step S4), and the motor rotation speed sensor 15 detects the motor rotation speed ωmtr (step S5).

  Next, the reference road surface reaction force torque calculator 16 calculates the reference road surface reaction force torque Talign_ref based on the steering angle θh and the vehicle speed V as shown in the following equation (2) (step S6).

However, in Equation (2), Kalign is a ratio of the road surface reaction force torque to the steering angle θh in a traveling region where the road surface reaction force torque is not saturated, and is a unique value for each vehicle.
Further, since the value of the ratio Kalign differs depending on the vehicle speed V, it is obtained in advance as a table value Kalign (V) corresponding to each vehicle speed V.

Next, the estimated road surface reaction torque calculator 17 calculates the estimated road surface reaction torque Talign_est based on the steering torque Ts, the motor current Imtr, the motor rotation speed ωmtr, and the vehicle speed V (step S7).
The specific calculation processing of the estimated road surface reaction torque Talign_est is not described here, but a known method (for example, Japanese Patent No. 3353770, Japanese Patent Application Laid-Open No. 2003-312521, Japanese Patent Application Laid-Open No. 2005-324737). Reference) can be used.

  Next, the understeer determination unit 18 calculates the understeering degree US_Index based on the road surface reaction force torque deviation between the reference road surface reaction force torque Talign_ref and the estimated road surface reaction force torque Talign_est (Equation 3) ( Step S8).

  The understeering degree US_Index obtained from Expression (3) indicates that the larger the value, the stronger the understeering of the vehicle.

Here, the relationship between the steering angle θh and the understeer state (refer to the horizontal axis), the normative road surface reaction force torque Talign_ref, the road surface reaction force torque and the yaw rate (refer to the vertical axis) will be described with reference to the explanatory diagram of FIG. .
FIG. 5 shows the relationship between the reference yaw rate and the actual yaw rate when the steering angle θh is increased from zero in constant vehicle speed driving on a low friction coefficient road surface (see the upper stage), the reference road surface reaction force torque Talign_ref, and It shows the relationship with the road surface reaction torque (see the lower part).

In FIG. 5, when the steering angle θh is increased, the reference road surface reaction force torque Talign_ref and the reference yaw rate (see solid line) increase linearly with the increase of the steering angle θh.
On the other hand, the road surface reaction torque (see the two-dot chain line) saturates away from the value of the reference road surface reaction torque Talign_ref when the steering angle θh is equal to or greater than the first steering angle θh1, and the road surface reaction force between the two torques. The torque deviation (understeering degree US_Index = | Talign_ref−road surface reaction torque |) increases.

  When the steering angle θh further increases and becomes a region greater than or equal to the second steering angle θh2 (> θh1), the actual yaw rate (see the one-dot chain line) saturates away from the reference yaw rate value, and the yaw rate deviation between both yaw rates (Standard yaw rate-actual yaw rate) increases. That is, as the steering angle θh increases, the degree of understeer US_Index increases and the understeer of the vehicle becomes stronger.

As shown in FIG. 5, the road surface reaction torque saturation occurs earlier by “θh2−θh1” than the saturation of the actual yaw rate. This is, for example, known from “Nakajima et al., A Vehicle ST-ate”. Detection Method Based on EST-imimated Aligning Torque using EPS, 05AC-46, 2005 SAE ". Therefore, in the first embodiment of the present invention, this phenomenon is used to detect the degree of understeer.
Further, the saturation mechanism of the road surface reaction torque is also described in the paragraphs “0006 to 0009” of the above-mentioned Patent Document 1 and is omitted (the road surface reaction torque in the first embodiment of the present invention is described in Patent Document 1). 1 is the same as the self-aligning torque described in 1).

  Returning to FIG. 4, following step S8, the understeer determiner 18 determines whether the vehicle is understeered by determining whether the understeering degree US_Index exceeds a predetermined threshold Th (step S9), and step S9. Is transmitted to the understeer suppression controller 2, the transmission controller 3, and the prime mover controller 4 (steps S10 and S11).

That is, if it is determined in step S9 that US_Index ≦ Th (that is, NO), a determination result indicating that there is no understeer is transmitted (step S10), and the processing routine of FIG. 4 ends.
On the other hand, if it is determined in step S9 that US_Index> Th (that is, YES), a determination result indicating understeer is transmitted (step S11), and the processing routine of FIG. 4 ends.

  As described above, according to the first embodiment of the present invention, the electric power steering controller (understeer detecting means) 1 for detecting the understeer of the vehicle, the prime mover controller 4 for controlling the prime mover output from the prime mover of the vehicle, A transmission controller 3 for controlling the transmission of the motor output to the wheels of the vehicle and the transmission ratio, and when the electric power steering controller 1 detects understeer of the vehicle, the transmission ratio Gr by the transmission controller 3 is set to the low speed side. The understeer suppression device reduces the prime mover output by the prime mover controller 4, and the prime mover controller 4 or the transmission controller 3 changes the speed ratio before and after the change of the speed ratio Gr. To reduce the driving force deviation or wheel speed deviation at Gosuru or controls the transmission to the wheels of the prime mover output.

  Further, when the transmission gear ratio Gr is changed by the transmission controller 3, the prime mover controller 4 determines the target of the prime mover based on the prime mover rotational speed Ne and the transmission gear ratio Gr before the change of the transmission gear ratio and the change destination gear ratio G2. The rotational speed Neo is calculated, and the prime mover output is temporarily controlled so that the rotational speed deviation ΔNe between the rotational speed of the prime mover after changing the gear ratio and the target rotational speed Neo becomes small.

  Further, when the transmission gear ratio Gr is changed by the transmission controller 3, the prime mover controller 4 determines the target rotational speed of the prime mover based on the wheel speed and the transmission gear ratio Gr before the change of the transmission gear ratio and the change destination gear ratio G2. Neo is calculated, and the prime mover output is temporarily controlled so that the rotational speed deviation ΔNe between the prime mover rotational speed after the change of the gear ratio and the target rotational speed Neo becomes small.

  Further, when the transmission gear ratio Gr is changed by the transmission controller 3, the prime mover controller 4 feeds back the calculated value or detected value of the wheel driving force so that the wheel driving force deviation before and after the change of the gear ratio is reduced. In addition, the motor output is temporarily controlled.

  Further, when the transmission gear ratio Gr is changed by the transmission controller 3, the prime mover controller 4 feeds back the calculated value or detected value of the wheel speed so that the wheel speed deviation of the wheel before and after the change of the gear ratio is reduced. , Temporarily control the motor output.

  Thus, when the vehicle is decelerated by detecting the understeer of the vehicle and performing the downshift by the transmission controller 3 and the reduction of the prime mover output by the prime mover controller 4, first, the transmission controller 3 outputs the prime mover output. Is temporarily transmitted to the wheels, and during that time, the prime mover rotational speed Ne is increased, and then the downshift is performed. Therefore, it is possible to realize an understeer suppressing device that prevents the occurrence of braking force and suppresses understeer accurately.

  In the first embodiment, the understeer suppression controller 2 is provided to transmit an instruction from the understeer suppression controller 2 to the transmission controller 3 and the prime mover controller 4. However, the present invention is not limited to this. . For example, the function of the understeer suppression controller 2 may be incorporated in any of the electric power steering controller 1, the transmission controller 3, and the prime mover controller 4.

Further, the processing of the understeer suppression controller 2 may be distributed to the transmission controller 3 and the prime mover controller 4.
In this case, if the process is executed as shown in the timing chart of FIG. 6, for example, the understeer suppression controller 2 can be eliminated.
In FIG. 6, steps ST-21 to ST-29 are the steps (ST-1, ST-3, ST-4, ST-5, ST-7, ST-9, ST-) described above (see FIG. 2), respectively. 11 and ST-13. Steps ST-210 to ST-212 in FIG. 6 correspond to the above-described steps ST-15, ST-16, and ST-17, respectively.

  Further, in the first embodiment, in order to reduce the change in the wheel driving force and the wheel speed before and after execution of the downshift, the target rotational speed Neo is calculated by the equation (1), and the prime mover rotational speed Ne is calculated as the target rotational speed. Although the downshift is executed after making it coincide with Neo, the method of reducing the change in the wheel driving force and the wheel speed (driving force deviation or wheel speed deviation) before and after the downshifting is not limited to this.

For example, instead of the prime mover rotational speed Ne, the target rotational speed Neo may be computed using the wheel speed (the prime mover rotational speed Ne can be computed from the wheel speed and the gear ratio).
Also suitable for reducing changes in wheel driving force and wheel speed before and after execution of downshifting with respect to the transmission ratio Gr before downshifting, the downshifting speed ratio G2, prime mover rotational speed Ne, and wheel speed. Alternatively, the motor rotational speed and the motor torque may be obtained in advance by a test and provided with a table, and the motor output may be controlled by determining the target rotational speed Neo and the target motor torque according to this table.
Further, the wheel drive force and the wheel speed may be always calculated or detected by a known method and fed back, and the prime mover output may be controlled so as not to change before and after execution of the shift down.

Embodiment 2. FIG.
Although not particularly mentioned in the first embodiment, the speed ratio Gr when the understeer is detected may be changed more slowly than when the understeer of the vehicle is not detected. .
FIG. 7 is a block diagram showing a schematic configuration of the second embodiment of the present invention in which the gear ratio Gr is gradually changed when understeer is detected.

  7, the understeer suppressing device according to the second embodiment of the present invention includes an electric power steering controller (understeer detecting means) 201, a transmission controller 203, and a prime mover controller 204. Each controller 201, 203, 204 is connected to the communication bus in the same manner as each controller 1, 3, 4 described above (see FIG. 1), and can perform message communication with each other. Yes.

The transmission controller 203 changes the speed ratio Gr when the vehicle understeer is detected by the electric power steering controller 201, compared to the case where the vehicle understeer is not detected by the electric power steering controller (understeer detection means) 201. Is configured to be performed gently.
In this case, it is assumed that the functions of the understeer suppression controller 2 (see FIG. 1) described above are included in the controllers 201, 203, and 204.

Next, the operation of the second embodiment of the present invention shown in FIG. 7 will be described with reference to the timing chart of FIG. Steps ST-301, ST-302, ST-303, and ST-305 in FIG. 8 respectively correspond to steps ST-1, ST-16, ST-4, and ST-17 described above (see FIG. 2). .
In the understeer suppressing device according to Embodiment 2 of the present invention, electric power steering controller 201, transmission controller 203, and prime mover controller 204 operate according to the timing chart shown in FIG.

In FIG. 8, first, the electric power steering controller 201 determines whether or not the vehicle is understeer, and transmits the determination result to the transmission controller 203 and the prime mover controller 204 (step ST−). 301).
In the same manner as described above, the transmission controller 203 and the prime mover controller 204 are performing normal processing until it is transmitted from the electric power steering controller 201 that it is understeer.

When the understeer is received from the electric power steering controller 201, the processing of the transmission controller 203 and the prime mover controller 204 is switched to the deceleration processing for suppressing understeer.
At this time, if the prime mover is an internal combustion engine, the prime mover controller 204 reduces the output by, for example, suppressing the supply air amount and the fuel amount, changing the ignition timing, and the prime mover is an electric motor. If there is, the output is reduced by suppressing the current supplied to the motor (step ST-302).

  Further, the transmission controller 203 determines whether or not to perform a gear ratio shift down (step ST-303), and when it is determined that the shift down needs to be performed, the shift in the case of not understeering is performed. Shift down processing that is gentler than down is executed (step ST-304).

  Note that the gradual shift down means that if the transmission is a general stepped transmission, the process of changing the gear ratio by disengaging the transmission and then changing the gear ratio to the engaged state. Do it slowly over time. This process can be realized by a known control such as temporarily lowering the hydraulic pressure of a hydraulic friction engagement device (not shown).

  If the transmission is a CVT (Continuously Variable Transmission), the speed ratio is gradually changed over time from the current speed ratio to the target speed ratio. Steps ST-301 to 304 described above are deceleration processing for suppressing understeer.

  In the middle of steps ST-301 to 304, or after step ST-304, if transmission of electric power steering controller 201 is not understeer, transmission controller 203 and prime mover controller 204 return to normal processing (step ST -305).

  As described above, according to the second embodiment of the present invention, the transmission controller 3 uses the understeer detection unit to detect the vehicle understeer compared to the case where the electric power steering controller 201 (understeer detection unit) does not detect the vehicle understeer. The gear ratio is gradually changed when understeer is detected.

  That is, when the vehicle is decelerated by detecting the understeer of the vehicle and performing the downshift by the transmission controller 203 and the reduction of the prime mover output by the prime mover controller 204, the downshift is performed more slowly than usual. Thus, it is possible to realize an understeer suppression device that prevents the occurrence of “excessive braking force during downshifting” and suppresses understeer accurately.

  In the first and second embodiments, the control for reducing the change (deviation) in the wheel driving force and the wheel speed before and after the shift down is performed. It is not always necessary to control the change in wheel speed to zero, and it may be reduced within a range that does not deteriorate the vehicle behavior.

  When the prime mover output is reduced, if the prime mover is an internal combustion engine, the output is reduced by suppressing the supply air amount or the fuel amount, changing the ignition timing, etc. If so, the output was reduced by suppressing the current supplied to the motor. At this time, the vehicle deceleration amount suitable for understeer suppression was calculated each time, and the vehicle deceleration amount was calculated appropriately. If the supply air amount, the fuel amount, the supply current to the motor, etc. are determined based on the above, the reliability of the understeer suppression control can be further improved.

  In addition, when understeer is detected, if the gear ratio Gr exceeds the predetermined value G1, a downshift to a predetermined value G2 (the gear ratio to which the shift is down) is executed, and the gear ratio Gr is less than or equal to the predetermined value G1. In this case, it is determined not to perform the downshift, but the vehicle deceleration amount suitable for understeer suppression is calculated each time, and whether or not the shift down is performed based on the appropriate calculation value of the vehicle deceleration amount, Alternatively, the reliability of the understeer suppression control can be further improved by determining the gear ratio G2 to be shifted down.

  Further, in the electric power steering controllers 1, 201, the reference road surface reaction torque Talign_ref and the estimated road surface reaction torque Talign_est are calculated. However, the understeer detection method is not limited to this.

  For example, the electric power steering controllers (understeer detection means) 1,201 include road surface reaction force torque reference change rate calculation means for calculating a road surface reaction force torque reference change rate Talign_rate_ref based on the motor rotational speed ωmtr and the vehicle speed V. Understeer of the vehicle may be detected based on a comparison between a road surface reaction torque reference change rate Talign_rate_ref and a differential value of the estimated road surface reaction torque Talign_est.

  In this case, first, the estimated road surface reaction torque Talign_est calculated in the same manner as described above is differentiated to obtain the “estimated road surface reaction torque torque change rate Talign_rate_est”. The reference change rate Talign_rate_ref ”is calculated.

However, in Formula (4), ωh is a steering wheel steering speed, which is a value obtained by multiplying the motor rotation speed ωmtr by a gear ratio. Further, Kalign (V) is a table value similar to that in Expression (2).
In this case, the understeering degree US_Index is expressed by the following equation (5).

As a result, understeer can be detected based on the road surface reaction torque saturation phenomenon, as described above. This is because, when the road surface reaction torque is saturated, a difference occurs between the road surface reaction torque standard change rate Talign_rate_ref and the estimated road surface reaction torque change rate Talign_rate_est.
In addition, according to this method, since a steering angle sensor becomes unnecessary, the manufacturing cost of an understeer suppression device can be reduced.

Further, a reference road reaction force torque Talign_ref is calculated from detection signals from a yaw rate sensor, a lateral G sensor, a four-wheel wheel speed sensor, and the like attached to the vehicle, and a comparison between the reference road reaction force torque Talign_ref and the estimated road reaction force torque Talign_est is performed. Understeer may be detected based on the above.
Alternatively, understeer is detected by comparing a standard yaw rate calculated from the steering wheel angle and the vehicle speed V with an actual yaw rate detected by a yaw rate sensor using a known technique (for example, see Japanese Patent Application Laid-Open No. 6-99800). May be.

  Furthermore, the electric power steering controllers 1 and 201 according to the first and second embodiments periodically determine whether or not understeering is performed, and based on the determination result, deceleration control for suppressing understeering, The transmission control and the prime mover control are switched immediately, but the period during which the understeer can be determined by the electric power steering controllers 1 and 201 may be only the period from the initial period to the middle period when the vehicle behavior is unstable. It is done. Therefore, when safety is important, for example, after determining that the electric power steering controllers 1, 201 are understeer, the deceleration control may be continued over a period until a predetermined time elapses, or The deceleration control may be continued until the traveling speed of the vehicle (vehicle speed V) drops below a predetermined value.

It is a block diagram which shows schematic structure of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a timing chart for demonstrating operation | movement of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a block block diagram which shows the specific example of the electric power steering controller used for Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the electric power steering controller used for Embodiment 1 of this invention. It is explanatory drawing which shows the relationship between the steering angle by this Embodiment 1, a reference | standard road surface reaction torque, a road surface reaction torque, a yaw rate, and an understeer. It is a timing chart for demonstrating operation | movement of the understeer suppression apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows schematic structure of the understeer suppression apparatus which concerns on Embodiment 2 of this invention. It is a timing chart for demonstrating operation | movement of the understeer suppression apparatus which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve. It is explanatory drawing which shows the general friction circle for demonstrating the subject which this invention tends to solve.

Explanation of symbols

  1,201 Electric power steering controller (understeer detection means), 2 Understeer suppression controller, 3,203 Transmission controller, 4,204 Motor controller, 11 Steering angle sensor (steering angle detection means), 12 Vehicle speed sensor (vehicle speed detection) Means), 13 steering torque sensor (steering torque detection means), 14 motor current sensor (motor current detection means), 15 motor rotation speed sensor (motor rotation speed detection means), 16 reference road surface reaction force torque calculator (reference road surface reaction) Force torque calculation means), 17 estimated road surface reaction force torque calculator (estimated road surface reaction force torque calculation means), 18 understeer determiner, Imtr motor current, Ne prime mover rotation speed, Neo target rotation speed, Ts steering torque, Talign_est estimated road surface Reaction torque, Talign_ref Standard road surface Torque, US_Index understeer degree, V vehicle speed, [theta] h the steering angle, Omegamtr motor speed.

Claims (10)

Understeer detecting means for detecting understeer of the vehicle;
Prime mover control means for controlling the prime mover output from the prime mover of the vehicle;
Transmission control means for controlling transmission and gear ratio of the motor output to the wheels of the vehicle,
When the understeer of the vehicle is detected by the understeer detection means, the understeer suppression device that changes the gear ratio by the transmission control means to a low speed side and reduces the prime mover output by the prime mover control means,
The prime mover control means or the transmission control means,
When the transmission gear ratio is changed by the transmission control means, the prime mover output is controlled so that the driving force deviation of the wheel before and after the change of the transmission gear ratio is reduced, or the transmission of the prime mover output to the wheels is transmitted. An understeer suppressing device characterized by controlling the understeer. Understeer detecting means for detecting understeer of the vehicle;
Prime mover control means for controlling the prime mover output from the prime mover of the vehicle;
Transmission control means for controlling transmission of the prime mover output to the wheels of the vehicle and a transmission gear ratio;
When the understeer of the vehicle is detected by the understeer detecting means, the gear ratio by the transmission control means is changed to a low speed side, and the understeer suppressing device reduces the prime mover output by the prime mover control means,
The prime mover control means or the transmission control means,
When the transmission ratio is changed by the transmission control means, the prime mover output is controlled so that the wheel speed deviation of the wheel before and after the change of the transmission ratio is reduced, or the transmission of the prime mover output to the wheels is controlled. An understeer suppressing device characterized by controlling the understeer. The prime mover control means includes
When changing the gear ratio by the transmission control means, the target rotational speed of the prime mover is calculated based on the rotational speed and gear ratio before the change of the gear ratio, and the speed ratio of the change destination,
3. The motor output is temporarily controlled so that a rotational speed deviation between the motor rotational speed after the change of the gear ratio and the target rotational speed becomes small. 4. Understeer suppression device. The prime mover control means includes
When changing the speed ratio by the transmission control means, the target rotational speed of the prime mover is calculated based on the wheel speed and speed ratio before the speed ratio change, and the speed ratio to be changed,
3. The motor output is temporarily controlled so that a rotational speed deviation between the motor rotational speed after the change of the gear ratio and the target rotational speed becomes small. 4. Understeer suppression device. The prime mover control means includes
When changing the gear ratio by the transmission control means, the calculated value or detected value of the wheel driving force is fed back,
The understeer suppressing device according to claim 1, wherein the motor output is temporarily controlled so that a driving force deviation of the wheel before and after the change of the gear ratio is reduced. The prime mover control means includes
When the transmission ratio is changed by the transmission control means, the calculated value or detected value of the wheel speed is fed back,
The understeer suppressing device according to claim 2, wherein the motor output is temporarily controlled so that a wheel speed deviation of the wheel before and after the change of the gear ratio is reduced.   The transmission control means gradually changes the speed ratio when the understeer of the vehicle is detected by the understeer detection means, compared to a case where the understeer of the vehicle is not detected by the understeer detection means. The understeer suppressing device according to claim 1 or 2, wherein The understeer detecting means includes
Vehicle speed detecting means for detecting the vehicle speed of the vehicle;
Steering torque detection means for detecting steering torque by the driver of the vehicle;
An electric motor for assisting the steering torque;
Motor current detecting means for detecting a motor current of the electric motor;
Motor rotation speed detection means for detecting the motor rotation speed of the electric motor;
Estimated road surface reaction force torque calculating means for calculating an estimated road surface reaction torque based on the vehicle speed, the steering torque, the motor current and the motor rotation speed,
The understeer suppressing device according to any one of claims 1 to 7, wherein understeer of the vehicle is detected based on the estimated road surface reaction force torque. The understeer detecting means includes
Steering angle detection means for detecting a steering angle by the driver of the vehicle;
Reference road surface reaction force torque calculating means for calculating a reference road surface reaction torque based on the steering angle and the vehicle speed,
The understeer suppressing device according to claim 8, wherein understeer of the vehicle is detected based on a comparison between the reference road surface reaction torque and the estimated road surface reaction torque. The understeer detecting means includes
Road surface reaction force torque reference change rate calculating means for calculating a road surface reaction force torque reference change rate based on the motor rotation speed and the vehicle speed;
9. The understeer suppression device according to claim 8, wherein understeer of the vehicle is detected based on a comparison between the road surface reaction torque standard change rate and a differential value of the estimated road surface reaction torque.

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