JP4459030B2 - Understeer warning device for vehicles - Google Patents

Description

  The present invention relates to an understeer alarm device for a vehicle, and more particularly to an understeer alarm device for a vehicle that changes an alarm amount set by the degree of understeer according to a road surface condition.

  There is a case where the steering state of the vehicle is “understeer”, which is a steering state in which the direction of the vehicle is insufficient with respect to the cutting amount of the steering wheel even though the steering wheel is cut.

As a method of determining understeer in a conventional vehicle, a yaw rate deviation (γ _ref −γ _real) which is a difference between a standard yaw rate γ _ref calculated from a steering angle and a vehicle speed and an actual yaw rate γ _real measured by a yaw rate sensor or the like. ). In this determination method, when the yaw rate deviation exceeds a positive reference value, it is determined as understeer, and the magnitude of the yaw rate deviation can be referred to as the degree of understeer.

  In Patent Document 1, the front wheel slip angle αF and the rear wheel slip angle αR calculated by the wheel slip angle calculation means based on the side slip angle of the vehicle body, the vehicle body speed detected by the vehicle body speed detection means, and the friction coefficient estimation means. The turning behavior state of the vehicle is determined by comparing the front wheel slip angle limit value αFLMT and the rear wheel slip angle limit value αRLMT determined on the basis of the friction coefficient estimated in step (1). That is, when the front wheel slip angle αF is larger than the front wheel slip angle limit value αFLMT and the rear wheel slip angle αR is equal to or less than the rear wheel slip angle limit value αRLMT, it is determined that the vehicle is in an understeer state. At this time, the degree of understeer is given by lαF−αFLMT1 + lαR−αRLMT1.

As an alarm device, there is a road slip alarm device that issues a warning when it is determined that the road surface condition is slippery as disclosed in Patent Document 2, but there is no device that issues an alarm depending on the degree of understeer.
Japanese Patent No. 3304776 Japanese Patent No. 3388861

  In the past, there was no device to inform the driver when the vehicle was understeered. Therefore, there is a problem that it is difficult to make an appropriate determination that the vehicle is in an understeer state.

  In view of the above problems, an object of the present invention is to provide an understeer warning device for a vehicle that appropriately notifies a driver when the vehicle is understeered.

  In order to achieve the above object, a vehicle understeer warning device according to the present invention is configured as follows.

  An understeer warning device for a first vehicle (corresponding to claim 1) includes an understeering degree detecting means for detecting an understeering degree, a road surface state detecting means for detecting a traveling road surface state, and an understeering degree being a predetermined value or more. And a warning means for warning the driver, and when the road surface state detection means determines that the road surface friction coefficient is low, it is characterized by increasing the predetermined value.

  According to the present invention, there is provided an understeer degree detecting means for detecting an understeer degree, a road surface state detecting means for detecting a traveling road surface condition, and an alarm means for warning a driver when the understeer degree is a predetermined value or more. When the road surface state detecting means determines that the road surface friction coefficient is low, the predetermined value is increased, so that the driver can be notified when the understeer state is appropriately obtained according to the road surface state.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of a vehicle according to an embodiment of the present invention. This vehicle is, for example, a front wheel drive vehicle, and includes a pair of left and right drive wheels 11 and 12 driven by the engine 10 and a pair of left and right driven wheels 13 and 14.

  The steering wheel 15 is provided with a steering angle detection unit 16 for detecting the steering angle δ, a road surface friction coefficient detection device (road surface μ detection device) 17 used as a road surface state detection device, and a vehicle speed sensor for detecting the vehicle speed. 18 and a yaw rate sensor 19 for detecting the actual yaw rate are provided. An understeer alarm 21 is provided in the vehicle. The steering angle detector 16, the road surface μ detector 17, the vehicle speed sensor 18, the yaw rate sensor 19, and the understeer alarm device 21 are connected to a controller 23 having a microcomputer. Reference numerals 11A, 12A, 13A, and 14A are strain gauges for detecting the road surface μ.

  FIG. 2 is a block diagram of the control device 23. The control device 23 includes an understeer level detection unit 24, an alarm amount increase unit 25, an offset amount setting unit 26, a subtraction unit 27, and an alarm drive unit 28. Reference numeral 16 indicates a steering angle detector, reference numeral 17 indicates a road surface μ detector, reference numeral 18 indicates a vehicle speed sensor, reference numeral 19 indicates a yaw rate sensor, and reference numeral 21 indicates an understeer alarm. The alarm amount increasing unit 25, the offset amount setting unit 26, the subtracting unit 27, the alarm device driving unit 28, and the understeer alarm device 21 constitute an alarm means. Here, the amount of alarm means the frequency and volume of the sound when the alarm is sound, and the frequency of the vibration when the alarm is vibration of a handle or the like, and the alarm is a plurality of LED indications. In this case, it refers to the number of lighting LEDs.

The understeer degree detection unit 24 includes a reference yaw rate calculation unit 29 and a subtraction unit 30, a signal related to the steering angle δ output from the steering angle detection unit 16, a signal related to the vehicle speed V output from the vehicle speed sensor 18, Based on the signal related to the actual yaw rate γ _real output from the yaw rate sensor 19, the degree of understeer of the vehicle is determined, and a signal D related to the determination result is output to the alarm amount increasing unit 25.

The reference yaw rate calculation unit 29 calculates a reference yaw rate γ _ref from a signal related to the vehicle speed V output from the vehicle speed sensor 18 and a signal related to the steering angle δ output from the steering angle detection unit 16, and subtracts the calculation result. Output to 30.

The subtracting unit 30 obtains a deviation (yawdev) between the reference yaw rate γ _ref output from the reference yaw rate calculation unit 29 and the actual yaw rate γ _real output from the actual yaw rate sensor, and alerts the deviation as a signal D related to understeer. It outputs to the quantity increase part 25.

  The warning amount increasing unit 28 sets a first warning amount based on the signal D related to the degree of understeer. The alarm amount used here is an alarm sound frequency.

  FIG. 3 shows a map for determining the frequency of the alarm sound according to the degree of understeer (here, actual-standard yaw rate deviation). The horizontal axis indicates the degree of understeer (here, actual-standard yaw rate deviation), and the vertical axis indicates the alarm sound frequency. A curve C10 is a graph showing the relationship between the degree of understeer and the alarm sound frequency. According to the curve C10, when the understeer level D increases from zero, the alarm sound frequency also increases, and when the understeer level D is equal to or greater than the value DM, the alarm sound frequency is constant. This map is searched for the degree of understeer (actual-standard yaw rate deviation), and the frequency of the alarm sound to be generated is determined. Normally, it is considered that the greater the actual-standard yaw rate deviation, that is, the greater the degree of understeer, the lower the driving stability. Therefore, the alarm sound frequency is set higher, and the warning to the driver is further strengthened.

  The offset amount setting unit 26 is a device that sets an offset amount that increases with a decrease in the road surface friction coefficient detected by the road surface friction coefficient detection device 17 that is a road surface state detection device. This device is provided for the following reasons. When an appropriate alarm sound frequency is set on a high μ road, an actual-normative yaw rate deviation easily occurs on a low μ road, so that the driver emits an alarm sound at a higher frequency and the alarm sound feels annoying. It can be considered. Therefore, in the situation where understeer is occurring, in the case of a low μ road, the offset amount is increased to make it difficult to sound an alarm sound. Conversely, if there is a deviation on the high μ road, the offset amount is reduced to make it easy to sound an alarm sound.

  As the device 17 for detecting the road surface μ, for example, a device as disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2002-2472) may be used. That is, the strain gauges 11A, 12A, 13A, and 14A (FIG. 1) attached to the inner surface of the tire width direction groove of the tire tread main groove portion continuously measure the inner circumferential strain in the tire circumferential direction, and calculate the strain displacement not shown. After calculating the strain displacement amount that is the difference between the inner surface strain on the tire road surface and the baseline strain value that is the average value of the tire circumferential inner surface strain outside the tire road surface by the device, the road surface friction coefficient detection device 17 The road surface friction coefficient is estimated from the calculated maximum value of the strain displacement amount using a map showing the relationship between the calculated maximum value of the strain displacement amount and the road surface friction coefficient.

  FIG. 4 is a map of the offset amount with respect to the road surface friction coefficient. Here, in the map, the horizontal axis is the estimated road surface μ, and the vertical axis is the alarm sound frequency offset amount. The warning sound frequency offset amount takes a value fH in the range where the estimated road surface μ is from zero to μ1, and in the range where the estimated road surface μ is smaller than μ1 and smaller than μ2, the alarm sound frequency offset amount increases from the value fH along the line segment L11 as the estimated road surface μ increases. It decreases to the value fL and takes the value fL when the estimated road surface μ is not less than μ2. Thus, when the road surface μ decreases, the frequency offset amount increases. As a result, the offset amount increases when turning on a low μ road, and the occurrence of frequent alarm sounds is suppressed.

  The subtracting unit 27 subtracts the offset amount output by the offset amount setting unit 26 from the alarm amount output from the alarm amount increasing unit 25, and outputs an alarm sound frequency that is an alarm amount. Then, the alarm device 21 is driven by the alarm device driving unit 28, and an alarm sound is emitted at a corresponding frequency.

  FIG. 5 is a graph showing the relationship of the alarm sound frequency with respect to the degree of understeer corresponding to the output from the subtractor 27. The horizontal axis indicates the degree of understeer D, and the vertical axis indicates the alarm sound frequency. A curve C20 indicates the alarm sound frequency with respect to the degree of understeer D when the estimated road surface μ is equal to or larger than the value μ2. The alarm sound frequency is negative on the graph when the degree of understeering D is less than the predetermined value DL from zero, so no alarm sound is emitted. When the degree of understeer exceeds a predetermined value DL, the alarm sound frequency increases from zero according to the curve C20, and becomes constant above a certain value. As the estimated road surface μ (road surface friction coefficient) becomes lower than μ2, the predetermined value of the degree of understeer in which the alarm sound frequency increases from zero increases from DL to DH. If the estimated road surface μ is smaller than μ1, the alarm sound frequency changes according to the curve C21 with respect to the degree of understeer D. When the degree of understeer is from zero to the predetermined value DH, the warning sound frequency is negative on the graph, so no warning sound is generated. When the degree of understeer is equal to or higher than the predetermined value DH, the warning sound frequency increases according to the curve C21. Above the value, the alarm sound frequency is constant.

  Accordingly, the driver can be notified when the understeer state is appropriately achieved.

  Next, a second embodiment will be described. In this embodiment, steering torque is used instead of the road surface μ detection device 17 as the road surface state detection device. The steering torque increases on a high μ road and decreases on a low μ road. Therefore, the road surface μ detector 17 shown in FIG. 2 is replaced with a steering torque detector.

  At this time, a map shown in FIG. 6 is used as a map used in the offset amount setting unit 26. Here, in the map, the horizontal axis represents the steering torque T, and the vertical axis represents the alarm sound frequency offset amount. The alarm sound frequency offset amount takes a value fH when the steering torque is in the range from zero to T1, and when the steering torque T is less than T1 and smaller than T2, the value fH to fL is increased along the line segment L12 as the steering torque T increases. When the steering torque T is T2 or more, the value fL is taken. In this way, the amount of frequency offset is increased by decreasing the steering torque T. As a result, the offset amount increases when turning on a low μ road, and the occurrence of frequent alarm sounds is suppressed. The other components in FIG. 2 are the same as those in the first embodiment.

  FIG. 7 is a graph showing the relationship of the alarm sound frequency with respect to the degree of understeer corresponding to the output from the subtractor 27. The horizontal axis indicates the degree of understeer D, and the vertical axis indicates the alarm sound frequency. A curve C30 indicates an alarm sound frequency with respect to the degree of understeer D when the steering torque T is equal to or greater than the value T2. The alarm sound frequency is negative on the graph when the degree of understeering D is less than the predetermined value DL from zero, so no alarm sound is emitted. When the degree of understeer exceeds a predetermined value DL, the alarm sound frequency increases from zero according to the curve C20, and becomes constant above a certain value. As the steering torque T becomes lower than T2, the predetermined value of the degree of understeer in which the alarm sound frequency increases from zero increases from DL to DH. When the steering torque T becomes smaller than T1, the alarm sound frequency changes according to the curve C31 with respect to the degree of understeer D. When the degree of understeer is from zero to a predetermined value DH, the warning sound frequency is negative on the graph, so no warning sound is emitted. When the degree of understeer is equal to or higher than the predetermined value DH, the warning sound frequency increases according to curve C31. Above the value, the alarm sound frequency is constant.

  With the apparatus having this configuration, the driver can be notified when the understeer state is appropriately achieved.

  Next, a third embodiment will be described. In this embodiment, lateral acceleration is used instead of the road surface μ detection device 17 as the road surface state detection device. Lateral acceleration increases with a high μ filter, and decreases with a low μ road. Therefore, the road surface μ detector 17 shown in FIG. 2 is replaced with a lateral acceleration detector.

  At this time, the map shown in FIG. 8 is used as the map used in the offset amount setting unit 26. Here, in the map, the horizontal axis represents the lateral acceleration G, and the vertical axis represents the alarm sound frequency offset amount. The alarm sound frequency offset amount takes the value fH when the lateral acceleration G is in the range from zero to G1, and from the value fH along the line segment L13 as the lateral acceleration G increases in the range where the lateral acceleration G is greater than or equal to G1 and less than G2. When the lateral acceleration G decreases to the value fL and the lateral acceleration G is G2 or more, the value fL is taken. In this way, the amount of frequency offset is increased as the lateral acceleration G decreases. As a result, the frequency offset amount is lowered according to the road surface μ. Also, when turning on a low μ road, the offset is large and the occurrence of frequent alarm sounds is suppressed. The other components in FIG. 2 are the same as those in the first embodiment.

  FIG. 9 is a graph showing the relationship of the alarm sound frequency with respect to the degree of understeer corresponding to the output from the subtractor 27. The horizontal axis indicates the degree of understeer D, and the vertical axis indicates the alarm sound frequency. A curve C40 indicates the alarm sound frequency with respect to the degree of understeer D when the lateral acceleration G is greater than or equal to the value G2. The alarm sound frequency is negative on the graph when the degree of understeering D is less than the predetermined value DL from zero, so no alarm sound is emitted. When the degree of understeer exceeds a predetermined value DL, the alarm sound frequency increases from zero according to the curve C40, and becomes constant above a certain value. Further, when the lateral acceleration G becomes lower than G2, the predetermined value of the degree of understeer in which the alarm sound frequency increases from zero increases from DL to DH. If the lateral acceleration G becomes smaller than G1, the alarm sound frequency changes according to the curve C41 with respect to the degree of understeer D. When the degree of understeer is from zero to the predetermined value DH, the warning sound frequency is negative on the graph, so no warning sound is emitted. When the degree of understeer is equal to or higher than the predetermined value DH, the warning sound frequency increases according to the curve C41. Above the value, the alarm sound frequency is constant.

  With the apparatus having this configuration, the driver can be notified when the understeer state is appropriately achieved.

  In the embodiment described above, the sound frequency is used as the alarm amount. However, the volume may be a volume, and the vibration of the handle is used as an alarm, and the vibration frequency is used as the alarm amount. Can be displayed, the amount of alarm can be the number of lighting LEDs.

  In the above embodiment, the understeer degree detection unit is set to the understeer degree based on the deviation between the standard yaw rate and the actual yaw rate. However, in the wheel slip angle calculation means disclosed in Patent Document 1, the side slip angle of the vehicle body is set. The front wheel slip angle αF and the rear wheel slip angle αR calculated based on the vehicle body speed detected by the vehicle body speed detecting means and the friction coefficient estimated by the friction coefficient estimating means αFLMT The degree of understeer may be determined by comparison with the rear wheel slip angle limit value αRLMT.

  The present invention is used as an understeer warning device that informs a driver of the degree of understeer of a vehicle.

1 is a schematic diagram of a vehicle according to an embodiment of the present invention. It is a block diagram of a control apparatus. It is a map for determining the alarm sound frequency with respect to a real-standard yaw rate deviation. It is a map for determining the amount of frequency offset with respect to the road surface μ detection value. 6 is a graph showing a relationship of an alarm sound frequency with respect to an understeer degree corresponding to an output from a subtracting unit 27. It is a map for determining the amount of frequency offset with respect to steering torque. 6 is a graph showing a relationship of an alarm sound frequency with respect to an understeer degree corresponding to an output from a subtracting unit 27. It is a map for determining the amount of frequency offset with respect to lateral acceleration. 6 is a graph showing a relationship of an alarm sound frequency with respect to an understeer degree corresponding to an output from a subtracting unit 27.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 11, 12 Drive wheel 13, 14 Drive wheel 15 Steering wheel 16 Steering angle detection part 17 Road surface friction coefficient detection apparatus 18 Vehicle speed sensor 19 Yaw rate sensor 21 Understeer alarm device 23 Control apparatus 24 Understeer degree detection part 25 Alarm amount increase part 26 Offset amount setting unit 27 Subtraction unit 28 Alarm drive unit

Claims (1)

An understeer level detecting means for detecting an understeer level;
Road surface condition detecting means for detecting the traveling road surface condition;
Alarm means for warning the driver when the degree of understeer is a predetermined value or more,
An understeer warning device for a vehicle, wherein the predetermined value is increased when the road surface state detection means determines that the road surface friction coefficient is low.

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