JP2004114918A - Steering assist force controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a steering assist force in such a way that a driver can perform steering operation comfortably if tire pneumatic pressure is within a proper range and can recognize the reduction of pneumatic pressure if tire pneumatic pressure is reduced exceeding the proper range. <P>SOLUTION: A steering assist force controller 15 is constituted in such a manner that an assist coefficient K is set to a large value if tire pneumatic pressure P is within the proper range and is low and the assist coefficient is quickly reduced and a steering assist force is quickly reduced if tire pneumatic pressure is reduced exceeding the proper scope. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vehicle provided with a power steering device that generates a steering assist force, and more particularly, when a tire air pressure falls outside an appropriate range, the steering assist force is suddenly reduced to notify a driver of a decrease in tire air pressure. The present invention relates to a steering assist force control device.
[0002]
[Related background art]
The power steering device generates a steering assist force for assisting a driver to operate a steering wheel. Generally, the steering assist force is variably controlled according to a steering torque or a vehicle speed input by operating the steering wheel. Such a steering assist force control is generally performed without considering the level of the tire air pressure. However, Patent Literature 1 discloses that the steering assist force is reduced when the tire air pressure decreases in order to improve the running stability of the vehicle. There has been proposed a steering assist force control device that lowers the steering assist force to make it difficult to be in a steering state.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-251751
[Problems to be solved by the invention]
The steering assist force control described in Patent Literature 1 is useful for stably running the vehicle when the tire air pressure is within a certain range, but is useful when the tire air pressure falls outside an appropriate range. There is a lack of attention to the dangers of continuing driving.
[0005]
In addition, run-flat tires that enable the vehicle to run when the tire air pressure drops have been put into practical use.Vehicles equipped with such run-flat tires can run, for example, up to a specified mileage even when the tire is punctured. It can be carried out. Therefore, in the case of a vehicle equipped with run flat tires, it is not necessary to stop the vehicle immediately when the tire air pressure decreases, but it is dangerous to run the vehicle beyond the specified traveling distance.
[0006]
Therefore, the present invention makes the steering reaction force constant irrespective of the tire air pressure if the tire air pressure is within the appropriate range so that the driver can operate the steering wheel comfortably, while the tire air pressure exceeds the appropriate range. It is an object of the present invention to provide a steering assist force control device that controls a steering assist force so that a driver notices an excessive decrease in tire air pressure when the tire pressure decreases.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a vehicle having a steering torque detecting means for detecting a steering torque of a driver, a power steering device for generating a steering assist force according to the steering torque, and an air pressure detecting means for detecting a tire air pressure. In the steering assist force control device, if the tire air pressure is within an appropriate range, the steering assist force is changed so as to increase as the tire air pressure decreases, and if the tire air pressure falls outside the appropriate range, the steering assist force is rapidly increased. It is characterized by being reduced to.
[0008]
According to the first aspect of the present invention, when the tire air pressure is within an appropriate range, the steering assist force is increased as the tire air pressure is lower. Therefore, the power steering is performed even when the tire air pressure is low and the required steering force is increased. Not only can the required steering force be easily generated with the assistance of the device, but also the steering reaction force characteristic becomes constant regardless of the tire air pressure, so that the driver can comfortably operate the steering wheel. On the other hand, when the tire pressure falls outside the appropriate range, the steering assist force is suddenly reduced and the steering wheel operation is suddenly heavier, giving a sense of incompatibility. In this case, it is determined that the continuation of the running of the vehicle should be abandoned, thereby avoiding a danger caused by a decrease in tire pressure.
[0009]
According to a second aspect of the present invention, there is provided a steering assist force control device for a vehicle including a run flat tire, a steering torque detecting unit, a power steering device, and a tire air pressure detecting unit that allow the vehicle to travel with a reduced tire air pressure. When the tire pressure is within the appropriate range, the steering assist force is changed so as to increase as the tire pressure decreases, and the steering assist force sharply decreases when the running of the vehicle with run-flat tires becomes unacceptable. It is characterized by.
[0010]
According to the second aspect of the present invention, when the tire air pressure is within an appropriate range, the steering assist force increases as the tire air pressure decreases, so that the steering reaction force characteristic becomes uniform regardless of the tire air pressure, and When the vehicle can be comfortably steered and the vehicle is not allowed to run with the run flat tires, the steering assist force is sharply reduced. Therefore, the driver recognizes that the vehicle cannot travel.
[0011]
A third aspect of the present invention is characterized in that vibration is applied to the steering handle instead of the sharp decrease in the steering assist force according to the first and second aspects of the invention.
According to the third aspect of the present invention, when the tire pressure falls below an appropriate range or when the vehicle is not allowed to run with the run flat tire, vibration is applied to the steering wheel, whereby the driver can reduce the tire pressure. It is recognized that the vehicle has become excessively low or the vehicle cannot travel.
[0012]
According to a fourth aspect of the present invention, when the tire running pressure of the steered wheels is reduced beyond an appropriate range and the running of the vehicle by the run flat tire is allowed, the deflection of the vehicle due to the reduced tire pressure is suppressed. It is characterized by generating a steering assist force.
According to the fourth aspect of the invention, if the vehicle can be driven by the run flat tire when the tire air pressure is reduced, a steering assist force for suppressing the deflection of the vehicle is generated. Steering and steering of the vehicle are corrected, and the stability of the vehicle during driving is improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a steering assist force control device according to a first embodiment of the present invention will be described with reference to the drawings.
The vehicle equipped with the steering assist force control device according to the present embodiment includes a steering torque sensor 11 for detecting a driver's steering torque (a steering torque applied to a steering shaft), and a tire pressure built in each of the front, rear, left, and right wheels. Pressure sensor (pneumatic pressure detecting means) 12, a wheel speed sensor 13 mounted on each wheel, and a steering torque T detected by these sensors 11 to 13, a tire pressure P and a steering assist force according to the vehicle speed V. And a power steering device 13 for generating power.
[0014]
The power steering device 13 of the present embodiment is electrically driven, and includes a motor 14 connected to a steering mechanism 16 and a control unit 15 for controlling the output torque and the rotation direction of the motor 14. The control unit 15 includes, for example, a microprocessor and functions as a steering assist force control device that controls the steering assist force. A main part of the control unit 15 (a target torque setting unit, an assist coefficient setting unit, and the like, which will be described later) constitutes an adjusting unit that variably adjusts the steering assist force.
[0015]
The control unit 15 generates a target assist torque value (hereinafter referred to as a target torque value) corresponding to a steering torque (steering angle) T detected by the steering torque sensor 11 and a vehicle speed V detected based on an output of the wheel speed sensor 13. ) Includes a target torque setting unit 21 for obtaining Ttar1. The target torque setting unit 21 calculates a target torque value Ttar1 corresponding to the steering torque T, the steering direction, and the vehicle speed V based on the steering direction and the vehicle speed V determined from the steering torque T. To be set.
[0016]
FIG. 2 illustrates a map used for setting a target torque value Ttar1 at a certain vehicle speed. As is clear from FIG. 2, the target torque value Ttar1 increases as the steering torque T generated by the driver's steering operation increases, and if the value of the steering torque T is positive (corresponding to a right turn, for example). While taking a positive value, if the value of the steering torque T is negative, it takes a negative value. That is, the steering assist force corresponding to the target torque value Ttar1 acts in the same direction as the steering torque T to assist the steering operation, and acts to reduce the steering force of the driver.
[0017]
In addition, the control unit 15 receives a tire pressure signal transmitted from a transmission circuit 12a built in each wheel together with the air pressure sensor 12 and a tire pressure signal of each wheel input from the reception circuit 31 based on the reception circuit 31. An air pressure determining unit 32 for determining the tire air pressure P of each wheel, and an assist coefficient setting unit for setting an assist coefficient K according to the tire air pressure P from the map shown in FIG. 3 based on the tire air pressure P determined by the air pressure determining unit 32 33.
[0018]
In the map of FIG. 3, the assist coefficient K decreases as the tire pressure P increases within its proper range (for example, 1.8 to 2.2 kg / cm ² ), and the tire pressure P exceeds the proper range. For example, it is set so that when it falls below 1.8 kg / cm ² , it suddenly drops in a step-like manner.
Further, the control unit 15 includes a multiplying unit 22 that inputs the target torque value Ttar1 set by the target torque setting unit 21 and the assist coefficient K set by the assist coefficient setting unit 33. The value Ttar1 is multiplied by the assist coefficient K, whereby the target torque value Ttar2 after the air pressure correction is obtained.
[0019]
The control unit 15 further includes a positive / negative determining unit 23 that determines whether the target torque value Ttar2 after the air pressure correction is positive or negative, a command current setting unit 24 that sets a command current Itar corresponding to the absolute value of the target torque value Ttar2, A current detection unit 25 for detecting an armature current I flowing through the motor 14, a duty ratio setting unit 26 for setting a duty ratio D such that the armature current I is equal to the command current Itar, and a motor drive unit for driving the motor 14. 27.
[0020]
The motor drive unit 27 switches the application direction (polarity) of the applied voltage E to the motor 14 according to the positive / negative of the target torque value Trar2, and varies the applied voltage E by performing duty control of the battery voltage based on the duty ratio D. This controls the rotation direction of the motor 14 and the magnitude of the output torque (steering assist force F).
[0021]
According to the steering assist force control device having the above configuration, when the tire pressures P of both the steered wheels are within an appropriate range, the assist coefficient K increases as the tire pressure P decreases, and the power steering device 13 is generated. The steering assist force F increases. As described above, the steering assist force F increases with a decrease in the tire pressure P, so that the driver can easily generate the required steering force that increases with a decrease in the tire pressure with the help of the steering assist force F. The steering reaction is constant regardless of the tire pressure P, so that comfortable steering can be performed.
[0022]
On the other hand, when the tire pressure P of one of the steered wheels falls outside the proper range, the assist coefficient K sharply decreases, the steering assist force F sharply decreases, and the steering operation becomes suddenly heavy. As a result, the driver recognizes that the tire pressure is excessively low and there is a risk of danger if the vehicle continues to travel, and determines that the continuation of the vehicle should be abandoned.
[0023]
Further, in the present embodiment, when the tire pressure P excessively decreases, the steering handle is vibrated to notify the driver of the decrease in tire pressure, and the state of the tire pressure of each wheel is always displayed. .
For this reason, the air pressure determination unit 32 of the control unit 15 sends the air pressure reduction signal S1 to the vibration device drive unit 34 and the display device drive unit 35 when the tire pressure P of any of the wheels is excessively reduced beyond the appropriate range. In response to the signal S1, the drive units 34 and 35 are operated, and the vibration device 17 provided in the steering handle is driven to vibrate the steering handle, and the tire pressure is reduced. Is displayed on the display device 18. In this way, the driver is reliably notified of the excessive tire pressure drop.
[0024]
Further, the air pressure determination unit 32 is configured to periodically transmit a tire pressure signal S2 indicating the tire pressure of each wheel to the display device driving unit 35, and the display device 19 is controlled by the driving unit 35 in response to the signal S2. The wheels are driven, and the state of the tire pressure of each wheel (whether or not it is within an appropriate range) is displayed.
Hereinafter, a steering assist force control device according to a second embodiment of the present invention will be described.
[0025]
The steering assist force control device according to the present embodiment is provided in a vehicle equipped with run flat tires. Here, the run-flat tire is not particularly limited as long as it allows the vehicle to continue running even when air bleeds due to puncture or the like. For example, it is possible to use a tire in which the side wall portion has increased bending resistance.
[0026]
In the case of a vehicle equipped with run flat tires, even if the tire air pressure is excessively reduced due to tire puncture or the like, the vehicle travels at a specified vehicle speed (e.g., 80 to 100 km / h) or below a specified travel distance (e.g., several tens to several hundreds km). It is possible to run, and therefore it is not necessary to stop the vehicle immediately when the tire pressure falls below an appropriate range.
[0027]
Therefore, in the present embodiment, if the tire air pressure is within an appropriate range, the steering assist force is variably controlled according to the tire air pressure so that the driver can perform steering comfortably as in the first embodiment. When the tire air pressure of the wheel falls below the appropriate range, unlike the first embodiment, the steering assist force is not immediately reduced.
[0028]
That is, when the tire pressure is within the proper range, the target torque value Ttar1 is set according to the torque characteristic line Ct1 (corresponding to the characteristic line in FIG. 2) indicated by the solid line in the map of FIG. While the assist coefficient K is set in accordance with the assist coefficient characteristic line Ca1 (corresponding to the characteristic line in FIG. 3), when the tire air pressure falls outside an appropriate range, the target torque value Ttar1 and the assist coefficient K are set as described later. Like that.
[0029]
Referring to FIG. 4, in the control unit (steering assist force control device) 15 according to the present embodiment, the air pressure determination unit 32 outputs a tire air pressure signal S2 representing the tire air pressure of each wheel, as in the first embodiment. The tire pressure of each wheel is sent to the display device driving unit 35 and the state of the tire pressure of each wheel is displayed on the display device 18, and the tire pressure P of any of the wheels is within an appropriate range (for example, 1.8 to 2.2 kg / cm ² ). When the pressure falls below 1.8 kg / cm ^2, for example, the air pressure reduction signal S1 is output. However, the air pressure decrease signal S1 is not supplied to the vibration device driving unit 34 and the display device driving unit 35 as in the first embodiment, but is set to the target torque setting unit 21, the assist coefficient setting unit 33, and the excessive vehicle speed. It is supplied to the determination unit 41 and the excessive traveling distance determination unit 42. Here, the supply of the air pressure reduction signal S1 to the target torque setting unit 21 and the assist coefficient setting unit 33 is performed only when the tire air pressure of the steered wheels (front wheels) has decreased beyond an appropriate range.
[0030]
Upon receiving the air pressure reduction signal S1 sent from the air pressure determination unit 32, the target torque setting unit 21 sets a target torque value Ttar1 corresponding to the steering torque according to the torque characteristic line Ct2 or Ct3 in the map of FIG. That is, when the tire air pressure of the right front wheel is excessively decreased, the target torque value Ttar1 is set according to the torque characteristic line Ct2, thereby generating a steering assist force for deflecting the vehicle to the left, thereby causing a decrease in the air pressure of the right front wheel. Suppress rightward deflection of the vehicle. On the other hand, when the tire pressure of the front left wheel decreases, the target torque value Ttar1 is set according to the torque characteristic line Ct3, thereby generating a steering assist force for suppressing the leftward deflection of the vehicle due to the decrease of the front left wheel air pressure. Let it.
[0031]
On the other hand, the assist coefficient setting unit 33 that has received the air pressure decrease signal S1 determines that the tire air pressure has decreased beyond an appropriate range, but that the vehicle can run with the run flat tires, and the map of FIG. The assist coefficient K is set based on the assist coefficient characteristic line Ca2 indicated by a broken line. That is, if the vehicle can be driven by the run flat tire, the assist coefficient K is not suddenly reduced even when the tire air pressure decreases.
[0032]
Excessive vehicle speed judging section 41 which has started operation in response to air pressure decrease signal S1 monitors whether vehicle speed V from wheel speed sensor 13 (FIG. 1) exceeds a prescribed vehicle speed, for example, 80 km / h, and determines whether vehicle speed V is within the prescribed range. When the vehicle speed exceeds the vehicle speed, an excessive vehicle speed signal S3 is transmitted to the vibration device driving unit 34 and the display device driving unit 35. Then, the vibrating device 17 (FIG. 1) is driven by the vibrating device driving unit 34 responding to the excessive vehicle speed signal S3, and the steering handle vibrates, and the display device 18 (FIG. 1) is driven by the display device driving unit 35. For example, a message such as "excessive vehicle speed (runnable)" or the like is displayed on the display device 18, thereby informing the driver that the running speed should be reduced.
[0033]
On the other hand, the excessive traveling distance determination unit 42 that has started operating in response to the air pressure reduction signal S1 from the air pressure determination unit 32 periodically calculates the traveling distance after the input of the air pressure reduction signal S1. That is, the travel distance per calculation cycle is calculated based on the vehicle speed V from the wheel speed sensor 13, and this is added to the travel distance up to the previous cycle to update the travel distance. Then, the excessive mileage determination unit 42 monitors whether the updated mileage exceeds a specified mileage, for example, 10 km. If the mileage exceeds the specified mileage, the vehicle cannot be continued to run with the run flat tires. The traveling impossibility signal S4 indicating the presence is sent to the assist coefficient setting unit 33, the driving device driving unit 34, and the display device driving unit 35.
[0034]
The assist coefficient setting unit 33 sets the assist coefficient K based on the assist coefficient characteristic line Ca3 indicated by the two-dot chain line in the map of FIG. Accordingly, if the tire pressure of any of the left, right, front and rear wheels becomes excessively low and the running of the vehicle using the run flat tires cannot be continued, the assist coefficient K suddenly decreases in a step-like manner, and the steering wheel operation becomes suddenly heavy, and the running becomes impossible. Notify the driver that the condition has been reached. At the same time, the vibration device drive unit 34 and the display device drive unit 35 operate to vibrate the vibration device 17 and display a message such as “impossible to run” on the display device 18 on the display device 18. Notify that it has become.
[0035]
This concludes the description of the preferred embodiment of the present invention, but the present invention is not limited to the first and second embodiments, and can be variously modified.
For example, in the above-described embodiment, when the tire air pressure is excessively reduced or when it becomes impossible to continue running the vehicle with the run flat tire, the steering assist force is suddenly reduced, the steering handle is vibrated, and a message is displayed. However, it is not essential to perform steering wheel vibration and message display.
[0036]
Further, in the embodiment, an electric power steering device for generating a steering assist force is used, but a hydraulic power steering device or a steering-by-wire power steering device may be used. It is not essential to use an air pressure sensor built in the wheel. For example, the air pressure may be detected from a vibration component received by the vehicle from the road surface using a wheel speed sensor. The assist coefficient setting maps shown in FIGS. 3 and 6 are examples, and can be variously changed. For example, in an air pressure region where the tire air pressure slightly decreases from an appropriate range, the assist coefficient is not suddenly reduced but is maintained at a value corresponding to the assist coefficient within the appropriate range, and the assist is performed when the tire air pressure falls beyond the region. The coefficient may be rapidly reduced. In addition, the present invention can be variously modified.
[0037]
【The invention's effect】
According to the first aspect of the present invention, if the tire air pressure is within an appropriate range, the steering assist force is changed so as to increase as the tire air pressure decreases, and if the tire air pressure falls outside the appropriate range, the steering assist force increases. When the tire pressure is within the appropriate range, the steering reaction force can be kept constant regardless of the tire pressure, and the driver can perform comfortable steering with the assistance of the power steering device. Can be. On the other hand, if the tire air pressure falls below an appropriate range, the steering wheel operation is suddenly heavier, and the driver can be surely aware that the tire air pressure has dropped excessively, thus avoiding the dangers associated with the tire air pressure drop. be able to.
[0038]
According to the second aspect of the present invention, when the air pressure of the run flat tire is within an appropriate range, the steering assist force is changed so as to increase as the tire air pressure decreases, and vehicle running by the run flat tire is not allowed. In such a case, the steering assist force is rapidly reduced, so that the driver's steering can be made comfortable when the tire air pressure is within an appropriate range, and when the vehicle traveling with the run flat tire is not allowed. Can suddenly reduce the steering assist force so that the driver can recognize that the vehicle cannot travel.
[0039]
According to the third aspect of the invention, since the vibration is applied to the steering wheel instead of the sharp decrease in the steering assist force in the first and second aspects of the invention, the tire air pressure is excessively reduced, or the vehicle runs on the run flat tire. Can be recognized by the driver.
The invention according to claim 4 suppresses the deflection of the vehicle due to a decrease in tire air pressure when the tire air pressure of the steered wheels is reduced beyond an appropriate range and the running of the vehicle by the run flat tire is permitted. Since the steering assist force is generated, it is possible to correct the deflection of the vehicle due to a decrease in the tire air pressure and to remove the steering wheel, thereby improving the stability of running the vehicle.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a steering assist force control device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of a map used for setting a target torque value in the steering assist force control device shown in FIG.
FIG. 3 is a diagram exemplifying a map used for setting an assist coefficient in the steering assist force control device shown in FIG. 1;
FIG. 4 is a schematic block diagram showing a steering assist force control device according to a second embodiment of the present invention.
FIG. 5 is a diagram illustrating a map used for setting a target torque value in the steering assist force control device shown in FIG. 4;
FIG. 6 is a diagram illustrating a map used for setting an assist coefficient in the steering assist force control device shown in FIG. 4;
[Explanation of symbols]
11 Steering torque sensor (steering torque detecting means)
12. Air pressure sensor (air pressure detection means)
13 Power steering device 15 Control unit (steering assist force control device)
21 Target torque setting section (adjustment means)
33 Assist coefficient setting unit (adjustment means)
43 Unavailable state determination unit

Claims (4)

A steering assist force control device for a vehicle, comprising: a steering torque detecting unit that detects a steering torque of a driver; a power steering device that generates a steering assist force according to the steering torque; and an air pressure detecting unit that detects a tire air pressure. ,
Adjustment means for variably adjusting the steering assist force according to the steering torque detected by the steering torque detection means and the tire pressure detected by the air pressure detection means,
The adjusting means changes the steering assist force so as to increase as the tire air pressure is lower if the tire air pressure is within an appropriate range, and performs the steering when the tire air pressure is lower than the appropriate range. A steering assist force control device characterized by rapidly reducing the assist force. A run-flat tire that allows the vehicle to travel with reduced tire air pressure, steering torque detecting means for detecting a driver's steering torque, a power steering device that generates a steering assist force in accordance with the steering torque, and a tire air pressure. A steering assist force control device for a vehicle, comprising:
Adjustment means for variably adjusting the steering assist force according to the steering torque detected by the steering torque detection means and the tire pressure detected by the air pressure detection means,
The adjusting means changes the steering assist force such that the lower the tire air pressure, the greater the steering assist force when the tire air pressure is within an appropriate range. A steering assist force control device characterized in that the force is rapidly reduced. Further provided with a vibration device for imparting vibration to the steering handle,
3. The steering assist force control device according to claim 1, wherein the vibration device is operated instead of a sudden decrease in the steering assist force by the adjustment unit. 4. The adjusting means is configured to deflect the vehicle due to a decrease in tire air pressure of the steered wheels when the tire air pressure of the steerable wheels of the vehicle decreases beyond an appropriate range while the running of the vehicle by the run flat tire is permitted. The steering assist force control device according to claim 2, wherein the steering assist force is generated such that the steering assist force is suppressed.

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