JP3947704B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus provided with a flow rate control valve for controlling a flow rate guided to a power cylinder side.
[0002]
[Prior art]
As a conventional flow control device, for example, a device described in Patent Document 1 is known. This conventional example is shown in FIG.
As shown, a pump P is connected to the flow control valve V.
The spool 1 of the flow rate control valve V has one end facing one pilot chamber 2 and the other end facing the other pilot chamber 3. The one pilot chamber 2 is always in communication with the pump P through the pump port 4. A spring 5 is interposed in the other pilot chamber 3. The pilot chambers 2 and 3 thus configured communicate with each other via a variable orifice a that controls the opening degree according to the excitation current I of the solenoid SOL.
[0003]
That is, one pilot chamber 2 communicates with the inflow side of the steering valve 9 that controls the power cylinder 8 via the flow path 6 → the variable orifice a → the flow path 7. The other pilot chamber 3 communicates with the inflow side of the steering valve 9 via the flow path 10 and the flow path 7.
Therefore, both the pilot chambers 2 and 3 communicate with each other through the variable orifice a, and the pressure on the upstream side of the variable orifice a acts on one pilot chamber 2 and the pressure on the downstream side is in the other pilot chamber. 3 will be affected.
[0004]
The spool 1 maintains a position where the acting force of one pilot chamber 2 and the acting force of the other pilot chamber 3 and the acting force of the spring 5 are balanced. In the balanced position, the spool port 11 is opened. The degree is decided.
Now, if the pump drive source 12 which consists of an engine etc. has stopped, pressure oil will not be supplied to the pump port 4. FIG. If no pressure oil is supplied to the pump port 4, no pressure is generated in the pilot chambers 2 and 3, so that the spool 1 maintains the illustrated normal position by the action of the spring 5.
[0005]
When the pump P is driven from the above state and pressure oil is supplied to the pump port 4, a flow can be made to the variable orifice a, and a differential pressure is generated there. Due to this differential pressure, a pressure difference is generated between the pilot chambers 2 and 3, and the spool 1 moves against the spring 5 in accordance with the pressure difference and maintains the balance position.
As the spool 1 moves against the spring 5 in this way, the opening degree of the tank port 11 is increased, but the control flow rate guided to the steering valve 9 side according to the opening degree of the tank port 11 at this time A distribution ratio between QP and the return flow rate QT returned to the tank T or the pump P is determined. In other words, the control flow rate QP is determined according to the opening degree of the tank port 11.
[0006]
The fact that the control flow rate QP is controlled according to the opening degree of the tank port 11 determined by the moving position of the spool 1 as described above means that the control flow rate QP is finally determined according to the opening degree of the variable orifice a. become. This is because the movement position of the spool 1 is determined by the pressure difference between the pilot chambers 2 and 3, and the opening of the variable orifice a determines this pressure difference.
[0007]
Therefore, in order to control the control flow rate QP according to the vehicle speed and the steering situation, it is only necessary to control the opening of the variable orifice a, that is, the excitation current of the solenoid SOL.
This is because the opening of the variable orifice a can be arbitrarily controlled from the maximum to the minimum depending on the magnitude of the excitation current of the solenoid SOL.
[0008]
The steering valve 9 controls the pressure of the power cylinder 8 in accordance with an input torque (steering torque) of a steering wheel (not shown). For example, if the steering torque is large, the supply amount to the power cylinder 8 is increased, and if the steering torque is small, the pressure of the power cylinder 8 is decreased accordingly. The switching amount of the steering torque and the steering valve 9 is determined by a torsional reaction force such as a torsion bar (not shown).
[0009]
If the switching amount of the steering valve 9 is increased when the steering torque is large as described above, the assist force by the power cylinder 8 is increased accordingly. On the contrary, if the switching amount of the steering valve 9 is reduced, the assist force is reduced.
If the necessary (required) flow rate QM of the power cylinder 8 determined by the moving speed of the piston and the control flow rate QP determined by the flow rate control valve V are made as equal as possible, the energy loss on the pump P side can be kept low. This is because the energy loss on the pump P side is caused by the difference between the control flow rate QP and the required flow rate QM of the power cylinder 8.
[0010]
In order to make the control flow rate QP as close as possible to the required flow rate QM of the power cylinder 8 as described above, it is the solenoid current command value SI for the solenoid SOL that controls the opening of the variable orifice a. The controller C controls the SI.
A steering angle sensor 16 and a vehicle speed sensor 17 are connected to the controller C, and the excitation current of the solenoid SOL is controlled based on the output signals of both sensors.
[0011]
In the figure, reference numeral 18 denotes a slit formed at the tip of the spool 1, and one pilot chamber 2 is always in communication with the flow path 7 through the slit 18 even when the spool 1 is at the position shown in the figure. ing. In other words, even when the spool 1 is in the illustrated state and the flow path 6 is closed, the oil discharged from the pump P is supplied to the steering valve 9 side through the slit 18. ing.
[0012]
Although the flow rate is very small as described above, the pressure oil is supplied to the steering valve 9 because the purpose is to prevent disturbance such as kickback and to ensure responsiveness.
Reference numeral 19 denotes a drive device for the solenoid SOL connected between the controller C and the solenoid SOL.
Reference numerals 13 and 14 are throttles, and reference numeral 15 is a relief valve.
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-260917 (pages 3 to 6, FIG. 1)
[0014]
[Problems to be solved by the invention]
In the conventional apparatus as described above, a vehicle speed sensor is connected to the controller C, and the excitation current of the solenoid SOL is controlled based on the output signal of this sensor. That is, as the vehicle speed increases, the basic solenoid current command value Ib output from the controller C decreases. If the basic solenoid current command value Ib is small, the opening of the variable orifice a is kept small, and the supply flow rate to the power cylinder is reduced.
However, when trying to avoid sudden obstacles and try to steer suddenly in a high-speed running state where the flow rate supplied to the power cylinder is small, the steering of the tire is delayed due to insufficient output of the power cylinder. There was a problem that occurred. The reason is as follows.
[0015]
If the vehicle is suddenly braked by stepping on a sudden brake during the high speed traveling, the front wheel axle load of the vehicle increases. If the front wheel axle load increases, a larger force than usual is required to steer the front wheel. However, since the supply flow rate to the power cylinder is reduced during the high-speed traveling, the assist force by the power cylinder is also reduced.
[0016]
In other words, when trying to steer the front wheels while braking suddenly during the above high-speed running, a large assist force of the power cylinder is required, but the supply flow rate to the power cylinder is reduced. Insufficient output of the power cylinder occurs, and a delay occurs in the turning of the tire.
In addition, the case where the driver tries to steer suddenly by stepping on the brake while driving at a high speed is when trying to avoid an obstacle. If a delay occurs in the steering of the tire when trying to avoid an obstacle, there is a possibility that an avoidance delay will occur.
[0017]
SUMMARY OF THE INVENTION An object of the present invention is to provide a power steering device capable of solving a shortage of output of a power cylinder when sudden braking is attempted during high-speed traveling and sudden steering is attempted.
[0018]
[Means for Solving the Problems]
A first invention includes a steering valve that controls a power cylinder, a variable orifice provided upstream of the steering valve, a solenoid that controls the opening of the variable orifice, a controller that controls the solenoid exciting current, A flow rate control valve that distributes a flow rate supplied from the pump to a control flow rate that leads to the steering valve according to the opening of the variable orifice and a return flow rate that is circulated to the tank or the pump, a vehicle speed sensor that detects the vehicle speed, Sudden braking detecting means for detecting sudden braking, the controller outputs a basic solenoid current command value Ib that is a basis of solenoid exciting current based on the vehicle speed, and sudden braking is performed by a signal from the sudden braking detecting means. If it is determined, the solenoid current command value Ia at the time of sudden braking is output and the variable Characterized by relatively increasing the opening degree of the orifice.
[0019]
According to a second aspect of the invention, a vehicle speed sensor is used as the sudden braking detection means, and the controller determines sudden braking when the vehicle speed reduction rate within a predetermined time is equal to or greater than a reference value.
According to a third aspect of the present invention, the sudden braking detecting means detects the amount of movement of the brake pedal within a predetermined time, and the controller determines that sudden braking is performed when the amount of movement is equal to or greater than a reference value.
[0020]
According to a fourth aspect of the present invention, the sudden braking detecting means detects the pressure increase rate of the brake booster within a predetermined time, and the controller determines that sudden braking is performed when the pressure increase rate is equal to or higher than a reference value. To do.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of the present invention shown in FIG. 1 is characterized in that the emergency braking solenoid current command value Ia is selected during sudden braking and the basic solenoid current command value Ib is selected during normal braking. This is the same as the conventional example shown in FIG.
Hereinafter, the controller C will be described in detail, and the same constituent elements as those in the related art will be denoted by the same reference numerals and description thereof will be omitted.
[0022]
The controller C includes a sudden braking circuit system A and a basic circuit system B. The sudden braking circuit system A outputs a sudden braking solenoid current command value Ia, and the basic circuit system B outputs a basic solenoid current command. The value Ib is output.
Further, the controller C is provided with a sudden braking determination means 20, and the switching means 21 is switched by a signal from the sudden braking determination means 20. By switching the switching means 21, either the sudden braking solenoid current command value Ia or the basic solenoid current command value Ib is selected.
In this embodiment, the switching means 21 outputs the normal basic solenoid current command value Ib, and outputs the sudden braking solenoid current command value Ia when the switching means 21 is switched.
[0023]
Further, a steering angle sensor 16 and a vehicle speed sensor 17 are connected to the controller C, and a steering angle signal θ, a steering angular velocity signal ω, and a vehicle speed signal v are input to the controller C.
The steering angle signal θ is calculated based on the steering angle detected by the steering angle sensor 16, and the vehicle speed signal v is calculated based on the vehicle speed detected by the vehicle speed sensor 17. The steering angular velocity signal ω is calculated by differentiating the steering angle signal θ. However, the steering angular velocity signal ω may be obtained directly by a steering angular velocity sensor provided separately.
[0024]
The sudden braking determination means 20 detects a reduction rate of the vehicle speed within a predetermined time from the vehicle speed signal v in order to determine sudden braking, and determines whether this reduction rate is equal to or higher than a reference value. For example, when the vehicle speed is decelerated from 100 km / h to 40 km / h, the decrease rate within the predetermined time is determined to be equal to or higher than the reference value. If the decrease rate is equal to or greater than the reference value, it is determined that the braking is sudden, and the switching means 21 is switched to select the solenoid current command value Ia for sudden braking.
On the other hand, when the decrease rate is smaller than the reference value, the sudden braking determination means 20 determines that the vehicle is running normally without sudden braking, and the basic solenoid current command is switched without switching the switching means 21. The value Ib is output. The reference value for the reduction rate can be set according to the characteristics of each vehicle.
[0025]
In the basic circuit system B, the basic solenoid current command value Ib is determined as follows.
As shown in FIG. 1, the steering angle signal θ, the steering angular velocity signal ω, and the vehicle speed signal v are input to the controller C. The controller C determines the solenoid current command value Iθ based on the steering angle signal θ. The solenoid current command value Iθ is a theoretical value that makes the relationship between the steering angle signal θ and the control flow rate QP linear. Based on. Further, the solenoid current command value Iω is determined based on the steering angular velocity signal ω. The solenoid current command value Iω is also determined based on a theoretical value in which the steering angular velocity signal ω and the control flow rate QP are linear characteristics.
[0026]
However, the solenoid current command value Iθ and the solenoid current command value Iω are both set to output zero if the steering angle signal θ and the steering angular velocity signal ω do not exceed a certain set value. That is, when the steering wheel is neutral or in the vicinity thereof, the solenoid current command values Iθ and Iω are set to zero.
[0027]
Further, the solenoid current command values Iθ and Iω may be stored in advance in the controller C as table values, or may be calculated by the controller C each time based on the steering angle signal θ or the steering angular velocity signal ω. It may be.
In any case, when the solenoid current command value Iθ and the solenoid current command value Iω are determined, both are added.
[0028]
When both solenoid current command values Iθ and Iω are added as described above, the added value (Iθ + Iω) is multiplied by the solenoid current command value Iv based on the vehicle speed signal v.
The solenoid current command value Iv based on the vehicle speed signal v outputs 1 when the vehicle speed is in the low speed range and outputs zero when the vehicle speed is high. Further, in the medium speed range between the low speed range and the high speed range, a value after the decimal point from 1 to zero is output.
[0029]
Therefore, if the added value (Iθ + Iω) is multiplied by the solenoid current command value Iv based on the vehicle speed signal v, (Iθ + Iω) is output as it is in the low speed range, and (Iθ + Iω) becomes zero in the high speed range.
In the middle speed range, a value that is inversely proportional to the speed increases as the speed increases.
The basic circuit system B outputs (Iθ + Iω) × Iv as the basic solenoid current command value Ib.
[0030]
On the other hand, when the vehicle speed reduction rate is greater than or equal to a certain value, the determination means 20 selects the sudden braking solenoid current command value Ia from the sudden braking circuit system A. The sudden braking solenoid current command value Ia is selected. Is set to a value that allows the tire to be steered immediately even during sudden braking. That is, the sudden braking solenoid current command value Ia is set so that the command value is at least larger than the basic solenoid current command value Ib during high-speed traveling.
[0031]
When the switching means 21 selects either the basic solenoid current command value Ib or the sudden braking solenoid current command value Ia, the selected solenoid current command value Ia, Ib includes the standby solenoid current command value Is. Is added. This is output from the controller C as a solenoid current command value I, and the solenoid excitation current is controlled based on the solenoid current command value I.
[0032]
The standby solenoid current command value Is is for always supplying a predetermined current to the solenoid SOL that controls the opening of the variable orifice a. That is, even when the solenoid current command value based on the steering angle signal θ, the steering angular velocity signal ω, and the vehicle speed signal v is all zero, the standby orifice current command value Is maintains the constant opening of the variable orifice a so that a predetermined standby The flow rate QS is always supplied to the steering valve 9 side.
[0033]
The reason for securing the constant standby flow rate QS in this way is as follows. That is, when a drag due to kickback or other disturbances or self-aligning torque acts on the tire, it acts on the rod of the power cylinder 8, but even in such a case, the standby flow rate QS should be secured. This is because the tire can be prevented from wobbling. Moreover, if the standby flow rate QS is secured, the response can be improved as much as the target control flow rate can be reached in a shorter time than when there is no standby flow rate QS.
Moreover, since the standby flow rate is always ensured in any case, it is possible to counter disturbance due to kickback or the like even during straight traveling in a low speed region, and it is possible to maintain good responsiveness during steering.
[0034]
In the embodiment as described above, the solenoid current command value Ia at the time of sudden braking is set to a value larger than the basic solenoid current command value Ib output at the time of high speed traveling, so that the opening degree of the variable orifice a is kept correspondingly. And the output of the power cylinder can be increased.
Therefore, even during sudden braking, it is possible to prevent a delay in steering due to insufficient output of the power cylinder.
[0035]
Furthermore, although the vehicle speed sensor 17 is used as the sudden braking detection means, sudden braking can be detected based on the vehicle speed signal v of the existing vehicle speed sensor 17 in this way, so that sudden braking can be detected. There is no need to provide a special sensor or the like. Since it is not necessary to provide a special sensor or the like, it is possible to detect the sudden braking without significantly increasing the cost.
[0036]
Further, in the above embodiment, the case where the braking is suddenly performed at the time of high speed traveling has been described. However, if this reference value is set to a case where the vehicle is decelerated from 70 km / h to 30 km / h, for example, only at the time of high speed traveling. This can be detected even when the vehicle is suddenly braked during medium-speed running.
[0037]
The sudden braking is detected based on the rate of decrease of the vehicle speed within a predetermined time. However, detecting the rate of decrease of the vehicle speed means that the acceleration of the vehicle is detected. It is. Therefore, an acceleration sensor may be separately provided as the sudden braking detection means. When the acceleration sensor is used in this way, it is determined that the state is a sudden braking state when the acceleration is greater than a certain value.
When the acceleration sensor is used, since the acceleration can be directly measured, the responsiveness can be further improved.
[0038]
Further, as the sudden braking detection means, the amount of movement of the brake pedal within a predetermined time may be detected. When the amount of movement is larger than the reference value, it is determined that the braking is sudden.
The movement amount of the brake pedal within a predetermined time is large when the brake pedal is depressed instantly. In other words, when sudden braking is applied. Therefore, sudden braking can be determined by detecting the amount of movement of the brake pedal.
[0039]
Further, as the sudden braking detection means, an increase in the pressure of the brake booster within a predetermined time may be detected. When the rate of pressure increase is larger than the reference value, it is determined that the braking is sudden.
The time when the pressure increase rate of the brake booster is large is when the brake pedal is instantly depressed and when the brake is suddenly depressed. When the brake is stepped on in this manner, the pressure of the brake booster increases rapidly.
Therefore, sudden braking can be detected by detecting the pressure increase rate of the brake booster.
[0040]
By detecting the amount of movement of the brake pedal or the pressure increase rate of the brake booster, the responsiveness to sudden braking can be further improved. This is because the act of stepping on the brake is the first action at the time of sudden braking, and since this first action can be directly detected, sudden braking can be detected more quickly.
[0041]
【The invention's effect】
According to the first invention, when it is determined that sudden braking is performed based on a signal from the sudden braking detection means, the solenoid current command value Ia during braking is output so that the opening of the variable orifice is relatively increased. As a result, there is no shortage of power cylinder flow even during sudden braking. Therefore, an obstacle avoidance delay can be prevented.
[0042]
According to the second invention, the vehicle speed sensor is used as the sudden braking detection means, and when the rate of decrease in the vehicle speed within a predetermined time is equal to or greater than the reference value, the controller determines that sudden braking is performed. There is no need to provide. Therefore, the cost can be reduced accordingly.
[0043]
According to the third invention, the sudden braking detection means detects the amount of movement of the brake pedal within a predetermined time, and when the amount of movement is equal to or greater than a reference value, the controller determines that sudden braking is performed. Therefore, it is possible to determine sudden braking more quickly. Therefore, the responsiveness can be kept good.
[0044]
According to the fourth invention, the sudden braking detection means detects the pressure increase rate of the brake booster within a predetermined time, and when the pressure increase rate is equal to or greater than a reference value, the controller determines that the braking is sudden. Therefore, it is possible to determine sudden braking more quickly. Therefore, the responsiveness can be kept good.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a control system for normal control of a controller according to an embodiment.
FIG. 2 is a circuit diagram of a conventional example.
[Explanation of symbols]
8 Power cylinder 9 Steering valve 17 Vehicle speed sensor V Flow rate control valve P Pump a Variable orifice QP Control flow rate QT Return flow rate C Controller v Vehicle speed signal Ia Quick braking solenoid current command value Ib Basic solenoid current command value

Claims (4)

Steering valve for controlling the power cylinder, a variable orifice provided upstream of the steering valve, a solenoid for controlling the opening of the variable orifice, a controller for controlling the solenoid exciting current, and a flow rate supplied from the pump In accordance with the opening of the variable orifice, a flow rate control valve that distributes the control flow rate to the steering valve and the return flow rate that is circulated to the tank or pump, a vehicle speed sensor that detects the vehicle speed, and a sudden flow rate that detects sudden braking of the vehicle Braking controller, and the controller outputs a basic solenoid current command value Ib that is the basis of the solenoid excitation current based on the vehicle speed, and when it is determined that sudden braking is performed by a signal from the sudden braking detector, The solenoid current command value Ia at the time of sudden braking is output to open the variable orifice. Power steering apparatus according to claim relatively larger that the. 2. The power steering apparatus according to claim 1, wherein a vehicle speed sensor is used as the sudden braking detection means, and the controller determines that the braking is sudden when the rate of decrease in the vehicle speed within a predetermined time is equal to or greater than a reference value. 2. The power according to claim 1, wherein the sudden braking detecting means detects the amount of movement of the brake pedal within a predetermined time, and the controller determines that sudden braking is performed when the amount of movement is equal to or greater than a reference value. Steering device. The sudden braking detection means detects the pressure increase rate of the brake booster within a predetermined time, and the controller determines that the braking is sudden when the pressure increase rate is equal to or higher than a reference value. Power steering device.

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