JP2006264364A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the continuity of driving feeling when sudden deceleration occurs after high-speed traveling for a given time or more. <P>SOLUTION: A controller C comprises a function determining whether or not traveling is at a set speed or more, a function counting time of a traveling state at the set speed or more, a function determining whether the traveling state at the set speed or more continues for a set time or not, a function whether traveling speed is reduced by a set value or more after continuously traveling at the set speed or more for the set time or more, and a function controlling the exciting current I of a solenoid to decrease the restoring ratio of assisting force of a power cylinder returning from small to large when the speed is reduced by exceeding the set value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  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.

As this type of apparatus, one described in Patent Document 1 has been conventionally known, and FIGS. 6 and 7 show this conventional apparatus. First, the configuration of the entire power steering apparatus will be described with reference to FIG.
A pump P is integrally incorporated in the main body B together with the spool 1 of the flow control valve V.
The spool 1 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.

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 via the variable orifice a, and the pressure on the upstream side of the variable orifice a acts on one pilot chamber, and the pressure on the downstream side acts on the other pilot chamber 3. Will act.

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 are balanced. At the balanced position, the opening degree between the pump port 4 and the tank port 11 is maintained. 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.

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, so that a pressure loss occurs there. Due to this pressure loss, a pressure difference is generated between the pilot chambers 2 and 3, and the spool 1 moves against the spring 5 according to 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.

  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.

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 is kept to a minimum when the solenoid SOL is in a non-excited state, and the opening is increased as the exciting current is increased.

  The steering valve 9 controls the supply flow rate to 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 supply flow rate 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).

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 steering torque and the control flow rate QP determined by the flow rate control valve V are always equal, 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.

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 excitation current for the solenoid SOL that controls the opening of the variable orifice a, and this excitation current is controlled. , Controller C.
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.

In the figure, reference numeral 18 is a slit formed at the tip of the spool 1, and even when the spool 1 is at the position shown in the figure, one pilot chamber 2 always communicates with the flow path 7 via this slit 18. I am doing so. 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.
Although the flow rate is very small as described above, the pressure oil is supplied to the steering valve 9 side for the purpose of preventing seizure of the entire apparatus, preventing disturbance such as kickback, and ensuring responsiveness. Because. However, these objects can also be achieved by securing a standby flow rate QS, which will be described later, and detailed description will be given later.

  Reference numeral 19 denotes a driver connected between the controller C and the solenoid SOL.

  The control system of the controller C is as shown in FIG. In other words, the steering angle signal from the steering angle sensor 16 and the vehicle speed signal from the vehicle speed sensor 17 are input to the controller C. Then, the controller C calculates the steering angle θ and the steering angular velocity ω from the steering angle signal. The required flow rate QM is estimated based on the steering angle θ and the steering angular velocity ω.

  The steering angle θ and the solenoid current command value I1 in FIG. 7 are determined based on a theoretical value at which the relationship between the steering angle θ and the control flow rate QP becomes a linear characteristic. Further, the relationship between the steering angular velocity ω and the solenoid current command value I2 is also determined based on a theoretical value in which the steering angular velocity ω and the control flow rate QP are linear characteristics.

However, if the steering angle θ and the steering angular velocity ω do not become a certain set value or more, both the command values I1 and I2 are output as zero. That is, when the steering wheel is neutral or in the vicinity thereof, the command values I1 and I2 are set to zero.
The solenoid current command value I1 for the steering angle θ and the solenoid current command value I2 for the steering angular velocity ω are stored in advance in the controller C as table values.

  The controller C outputs the steering angle current command value I3 and the steering angular velocity current command value I4 based on the output signal of the vehicle speed sensor 17, and the steering angle current command value I3 and The steering angular velocity current command value I4 is stored in advance in the controller C as a table value.

The steering angle current command value I3 is set to 1 in the low speed range and, for example, 0.6 in the maximum speed range. Further, the steering angular velocity current command value I4 is set to 1 in the low speed range and to, for example, 0.8 in the maximum speed range.
That is, the steering angle current command value I3 is controlled in the range of 1 to 0.6, while the steering angular speed current command value I4 is controlled in the range of 1 to 0.8. Therefore, the gain from the low speed range to the maximum speed range is set to be larger for the steering angle current command value I3.

  The solenoid current command value I1 based on the steering angle θ is multiplied by the steering angle current command value I3 corresponding to the vehicle speed signal V. Therefore, the higher the vehicle speed signal V, the smaller the output value that is the result of multiplication, that is, the current command value I5 of the steering angle system. In addition, since the gain of the steering angle current command value I3 is larger than the gain of the steering angular velocity current command value I4, the reduction rate increases as the speed increases.

  On the other hand, for the solenoid current command value I2 based on the steering angular velocity ω, the steering angular velocity current command value I6 is output with the steering angular velocity current command value I4 corresponding to the vehicle speed as a limit value. The current command value I6 is also decreased according to the vehicle speed, but the gain is made smaller than the gain of the steering angle current command value I3. It is smaller than the command value I5.

The steering angle system current command value I5 output as described above is compared with the steering angular velocity system current command value I6, and the larger current command value I5 or I6 is adopted.
The reason for adopting the larger one in this way is as follows. In other words, since the steering is rarely operated suddenly during high speed traveling, the steering angular velocity system current command value I6 is small and the steering angular system current command value I5 is larger when the steering operation is performed. It is normal.

  Therefore, when traveling at high speed, the larger current command value I5 is adopted while using the steering angle as a reference to improve the safety and stability of the steering operation. Moreover, by doing in this way, the higher the traveling speed, the higher the ratio of decreasing the control flow rate QP, and the more energy loss can be achieved.

On the other hand, when the vehicle is traveling at a low speed, the steering is often suddenly operated. Therefore, in many cases, the steering angular velocity is larger. Thus, when the steering angular velocity is large, responsiveness is important.
Therefore, when the vehicle is traveling at a low speed, the current command value I6 of the steering angular velocity system is adopted while using the steering angular velocity as a reference so as to improve the operability of the steering operation, that is, the responsiveness. In this way, even when the traveling speed is increased to some extent, when the steering is suddenly operated, the control flow rate QP can be sufficiently secured and priority can be given to responsiveness.

Even if the vehicle traveling speed is constant, the steering angle system current command value I5 may increase or the steering angular speed system current command value I6 may increase. For example, when the steering is steered at a certain angle and the steering is held at the position of the steering angle θ, the steering angular velocity ω becomes zero. In this case, although the vehicle speed is the same, the current command value I6 for the steering angular velocity system is initially large, and the current command value I5 for the steering angular system is greater after the steering is started.
However, in this conventional apparatus, since the larger one of the current command values I5 and I6 is selected, any current command value is output under any traveling condition.

  If neither of the current command values I5 and I6 is output at the time of steering as described above, the control flow rate QP cannot be secured. If the control flow rate QP cannot be secured, the power cylinder 8 will move at the time of steering while losing the drag due to the self-aligning torque of the vehicle. If the power cylinder 8 moves without maintaining its position in this way, it is impossible to maintain the steering itself.

  However, as described above, since either one of the current command values I5 and I6 is used, neither of them becomes zero during the steering operation. In other words, since the steering angle θ is maintained even during steering, the solenoid current command value I1 can be secured. Therefore, the power required for steering can be maintained at the current command value I1.

  On the other hand, the steering may be suddenly operated even when traveling at high speed. At this time, since the current command value I6 of the steering angular velocity system is increased, the current command value I6 is selected. However, since the current command value I6 is a value controlled within the range of the limit value of the steering angular velocity current command value I4, safety is sufficiently ensured.

Further, the standby current command value I7 is added to the current command value I5 or I6 selected as described above.
The standby current command I7 is for always supplying a predetermined current to the solenoid SOL of the variable orifice a. Thus, the variable orifice a supplied with the standby current command value I7 has a constant opening degree even if the solenoid current command value based on the steering angle θ, the steering angular velocity ω, and the vehicle speed is zero. While maintaining a constant standby flow rate QS.

Next, the operation of the conventional apparatus will be described.
While the vehicle is running, a steering angle system current command value I5, which is a product of the solenoid current command value I1 based on the steering angle and the steering angle current command value I3, is output. At the same time, the solenoid current command value I2 based on the steering angular velocity is output with the steering angular velocity current command value I6 using the steering angular velocity current command value I4 as a limit value.

Then, the magnitude of the current command value I5 for the steering angle system and the current command value I6 for the steering angular velocity system is determined, and the standby current command value I7 is added to the larger command value I5 or I6. The solenoid excitation current I is determined.
The solenoid excitation current I is mainly based on the steering angle system current command value I5 when the vehicle is traveling at high speed, and is mainly based on the steering angle speed system current command value I6 when the vehicle is traveling at low speed.

However, even during low-speed running, the solenoid excitation current I is determined based on the steering angle system current command value I5 during steering.
Even when the vehicle is traveling at a high speed, when the steering is suddenly operated, the excitation current I of the solenoid is determined based on the current command value I6 of the steering angular velocity system.
JP 2001-260917 A

  In the conventional apparatus as described above, if the vehicle speed is determined, the assist force is all determined according to the vehicle speed at that time. For example, on a highway that runs at 80 km / h or more, if the vehicle speed is suddenly reduced after entering a interchange or service area after running for a certain period of time or longer, the assistance is made according to the suddenly slowed speed. Since the force is determined, the driver's steering feeling may be uncomfortable. In other words, when the vehicle speed is suddenly reduced as described above during high-speed traveling, the steering wheel operation may feel lighter than it actually is. However, as a driver, it is possible to drive smoothly if the continuity of the steering sensation is maintained. However, the conventional device has a problem that the continuity of the steering sensation may not be maintained. .

  An object of the present invention is to provide a device capable of maintaining continuity in a steering feeling even when the speed is suddenly reduced after traveling at a high speed on a highway for a certain time or more.

  The present invention is based on the following apparatus. That is, a spool is incorporated in the main body, one end of the spool faces one pilot chamber that is always in communication with the pump port, and the other end of the spool faces the other pilot chamber with a spring interposed therebetween. An orifice is provided on the downstream side of the pilot chamber, and pressure oil is guided to the steering valve that controls the power cylinder through the orifice, while the pressure upstream of the orifice is used as the pilot pressure of the one pilot chamber, The pressure is set as the pilot pressure of the other pilot chamber, and the movement position of the spool is controlled by the pressure balance of both pilot chambers, and the control flow rate QP for guiding the pump discharge amount to the steering valve side according to the movement position, And the return flow rate QT to be recirculated to the tank or pump, Is a variable orifice that controls the opening according to the excitation current I of the solenoid, and a controller that controls the excitation current I of the solenoid of this variable orifice is provided, and a steering angle sensor is connected to this controller. The controller calculates or stores the steering angle θ and the steering angular velocity ω corresponding to the steering angle from the steering angle sensor, while the controller outputs a solenoid current command value I1 corresponding to the steering angle θ and a solenoid corresponding to the steering angular velocity ω. It is assumed that the power steering device is configured to store or calculate the current command value I2 and to control the excitation current I of the solenoid of the variable orifice based on these current command values I1 and I2.

  On the premise of the above apparatus, the first invention provides a function for the controller to determine whether or not the vehicle is traveling at a set speed or higher, a function for counting a running state time exceeding the set speed, and a set speed. A function for determining whether or not the above driving state has continued for a set time or more, and a function for determining whether or not the driving speed has been decelerated by a set value or more after continuously driving for a set time or more. And a function of controlling the solenoid current command value I in order to reduce the rate of return when the assist force of the power cylinder returns from small to large when decelerated beyond the set value. Have.

  According to a second aspect of the invention, the controller stores at least two types of vehicle speed signal control characteristics, which are functions of the vehicle speed and a current command value related to the vehicle speed, and a normal speed control characteristic and a low gain control characteristic. It is determined whether or not the vehicle has continuously traveled for the set time or more, and when the travel speed is decelerated by more than the set value after continuously traveling for the set speed or more, the vehicle speed signal is set to low gain. Output based on the control characteristics, even if the speed is below the set speed or above the set speed, even if it is running within the set time, or even if it is continuously running for more than the set time, the subsequent deceleration value is set above When the speed is lower than the speed, the vehicle speed signal is output based on the normal control characteristics.

  According to a third aspect of the present invention, the controller includes a normal control system and a special control system that reduces a return rate at which the assist force of the power cylinder returns from small to large, and continuously exceeds the set speed and for the set time. Judgment is made whether or not the vehicle has traveled, and after traveling continuously over the set speed and over the set time, when the travel speed is decelerated over the set value, the special control system is selected and the set speed is below or above the set speed. Even if it is running within the set time, or even if it is running continuously for more than the set time, the normal control system is selected if the subsequent deceleration value is less than the set speed Characterized by points.

  According to the first to third aspects of the present invention, even when the vehicle speed is suddenly lowered after entering the interchange or service area after traveling at a high speed for a certain time on the expressway, the steering wheel operation feels lighter than it actually is. Nothing will happen. In other words, the continuity of the steering feeling can be maintained even when the speed is suddenly lowered after traveling at a high speed for a certain time on the expressway.

  FIG. 1 shows the first embodiment. In the first embodiment, the overall structure is exactly the same as that of the conventional apparatus shown in FIG. Accordingly, detailed description of the overall structure shown in FIG. 6 is omitted, and in the following description, the description of FIG. 6 and the reference numerals used therein are all incorporated.

  In addition, as is apparent from FIG. 1, the first embodiment is different from the conventional method in which the vehicle speed signal V for calculating the current command values I3 and I4 is different. is there. However, in the following, each component in FIG.

  The control system of the controller C in the first embodiment is as shown in FIG. In other words, the steering angle signal from the steering angle sensor 16 and the vehicle speed signal from the vehicle speed sensor 17 are input to the controller C. Then, the controller C calculates the steering angle θ and the steering angular velocity ω from the steering angle signal. The required flow rate QM is estimated based on the steering angle θ and the steering angular velocity ω.

  The steering angle θ and the solenoid current command value I1 in FIG. 1 are determined based on a theoretical value at which the relationship between the steering angle θ and the control flow rate QP is linear. Further, the relationship between the steering angular velocity ω and the solenoid current command value I2 is also determined based on a theoretical value in which the steering angular velocity ω and the control flow rate QP are linear characteristics.

However, if the steering angle θ and the steering angular velocity ω do not become a certain set value or more, both the command values I1 and I2 are output as zero. That is, when the steering wheel is neutral or in the vicinity thereof, the command values I1 and I2 are set to zero.
The solenoid current command value I1 for the steering angle θ and the solenoid current command value I2 for the steering angular velocity ω are stored in advance in the controller C as table values. However, in the present invention, the controller C may calculate the current command values I1 and I2 each time.

  The controller C outputs the steering angle current command value I3 and the steering angular velocity current command value I4 based on the output signal of the vehicle speed sensor 17, and the steering angle current command value I3 and The steering angular velocity current command value I4 is stored in advance in the controller C as a table value.

The steering angle current command value I3 is set to 1 in the low speed range and, for example, 0.6 in the maximum speed range. Further, the steering angular velocity current command value I4 is set to 1 in the low speed range and to, for example, 0.8 in the maximum speed range.
That is, the steering angle current command value I3 is controlled in the range of 1 to 0.6, while the steering angular speed current command value I4 is controlled in the range of 1 to 0.8. Therefore, the gain from the low speed range to the maximum speed range is set to be larger for the steering angle current command value I3.

  The solenoid current command value I1 based on the steering angle θ is multiplied by the steering angle current command value I3 corresponding to the vehicle speed signal V. Therefore, the higher the vehicle speed signal V, the smaller the output value that is the result of multiplication, that is, the current command value I5 of the steering angle system. In addition, since the gain of the steering angle current command value I3 is larger than the gain of the steering angular velocity current command value I4, the reduction rate increases as the speed increases.

  On the other hand, for the solenoid current command value I2 based on the steering angular velocity ω, the steering angular velocity current command value I6 is output with the steering angular velocity current command value I4 corresponding to the vehicle speed as a limit value. The current command value I6 is also decreased according to the vehicle speed, but the gain is made smaller than the gain of the steering angle current command value I3. It is smaller than the command value I5.

  The logic for specifying the vehicle speed signal V for specifying the current command values I3 and I4 as described above will be described next. In this first embodiment, the logic for specifying the vehicle speed signal V is different from the conventional one. To do.

  First, the structure of the controller that is different from the conventional one will be described. That is, the controller C is configured to output a vehicle speed signal from the calculation unit shown in FIG.

  The calculation unit stores in advance a set speed for specifying high-speed driving. The set speed is set to 80 km / h as an example in the first embodiment on the premise of driving on a highway. is doing. The calculation unit thus configured has a function of determining whether or not the current vehicle speed is 80 km / h or more, and a function of counting the travel time when traveling at 80 km / h or more. .

  Furthermore, although the said calculating part has memorize | stored the setting time for determining how long driving | running | working continued at 80 km / h or more, in this 1st Embodiment, the setting time is defined as 10 minutes. This time of 10 minutes assumes that the driver's feeling of speed will be dulled, for example, if he / she continuously travels on an expressway for 10 minutes or more. Further, the arithmetic unit thus configured stores two types of control characteristics shown in the graph of FIG.

  The graph of FIG. 2 shows the vehicle speed signal characteristic that is a function of the vehicle speed and the current command value related to the vehicle speed, and specifies two types of the normal control characteristic A and the low gain control characteristic B. is there. That is, in FIG. 2, the actual vehicle speed is divided into 40 km / h or less and 80 km / h or more as an example. A vehicle speed signal V that outputs a constant high current command value when it is 40 km / h or less. Is output, and when it is 80 km / h or higher, a vehicle speed signal V that outputs a constant low current command value is output. The range from 40 km / h to 80 km / h is divided into a normal control characteristic A and a low gain control characteristic B. In addition, even if the low gain control characteristic B is controlled between 80 km / h and 40 km / h, when reaching 40 km / h, as shown by the characteristic line C in FIG. A vehicle speed signal V from which a value is obtained is output.

  Further, the calculation unit is configured to determine whether or not the vehicle has continuously traveled at a set speed of 80 km / h or more for 10 minutes or more as a set time. Furthermore, this calculation unit determines whether the deceleration speed is equal to or higher than the set speed when the travel speed is decelerated after continuously traveling for more than the set speed and for the set time or longer. The deceleration set value is stored in advance. And in this 1st Embodiment, the said deceleration setting value is set to 40 km / h as an example. The reason why the deceleration set value is increased to 40 km / h in this way is that when the speed is reduced by 40 km / h, the speed difference is too large, and it is thought that the speed difference does not give a driving feeling. Therefore, if the deceleration setting value is a value that does not give a sense of driving to the speed difference, a specific numerical value does not matter.

  When the normal control characteristic A is selected, the arithmetic unit configured as described above outputs a vehicle speed signal V that matches the control characteristic, and when the low gain control characteristic B is selected, the vehicle speed that matches the control characteristic. The signal V is output. Then, the current command value I3 or I4 is specified according to the vehicle speed signal V.

  Next, the function of the controller C including the calculation unit will be described based on the flowchart shown in FIG. In the normal traveling of the vehicle, it is rare that the vehicle travels at 80 km / h or more for 10 minutes or more and suddenly decelerates by 40 km / h. Therefore, in the flowchart shown in FIG. The stage in which the normal control characteristic A at the time of traveling is selected is started as step S1. Thus, in the state where the normal control characteristic A is selected, the vehicle speed signal V is output based on the normal control characteristic A.

  The controller C always checks whether the vehicle speed is 80 km / h or more, which is the set speed, with the normal control characteristic A selected as described above, and normal control is performed unless the vehicle speed is 80 km / h or more. Control based on the characteristic A is continued (step S2). And if the said vehicle speed exceeds 80 km / h, it will be determined whether the vehicle speed continued for 10 minutes or more which is setting time.

  If traveling at 80 km / h or more does not continue for 10 minutes or more, the vehicle speed signal V is output again based on the normal control characteristic A. However, when traveling at 80 km / h or more continues for 10 minutes or more, the process proceeds to step S4 to check whether or not the vehicle has been decelerated by 40 km / h or more from the traveling at 80 km / h or more. If there is no deceleration of 40 km / h, the process proceeds to step S3 again, and it is checked whether traveling at 80 km / h or more has continued for 10 minutes or more. If it is determined in step S4 that the vehicle has decelerated at 40 km / h or more, the process proceeds to step S5 where the low gain control characteristic B is selected and whether or not the vehicle speed has reached 40 km / h or less is checked. (Step S6) If the vehicle speed is 40 km / h or less, the vehicle returns to the normal control characteristic A along the return characteristic line C shown in FIG.

  However, if the vehicle speed does not reach 40 km / h or less, the process returns to step S5, and the vehicle speed signal V based on the low gain control characteristic B is output. In the low gain control characteristic B, as is apparent from FIG. 2, the vehicle speed signal V at that time is smaller than that in the normal control characteristic A even if the actual vehicle speed is the same. When the controller C specifies the vehicle speed signal V in this way, current command values I3 and I4 are calculated based on the vehicle speed signal V.

  Based on the vehicle speed signal V calculated as described above, the controller C calculates current command values I3 and I4. As described above, the solenoid current command value I1 based on the steering angle θ includes the vehicle speed signal V1. The current command value I5 is output by multiplying the steering angle current command value I3 corresponding to the signal V, and the steering angular velocity current command value I4 corresponding to the vehicle speed is a limit value for the solenoid current command value I2 based on the steering angular velocity ω. The steering angular velocity system current command value I6 is output.

  The steering angle system current command value I5 output as described above is compared with the steering angular velocity system current command value I6, and the large current command value I5 or I6 is adopted. In this way, the larger one is adopted, and the reason is as described above.

Further, the standby current command value I7 is added to the current command value I5 or I6 selected as described above.
The standby current command I7 is for always supplying a predetermined current to the solenoid SOL of the variable orifice a. Thus, the variable orifice a supplied with the standby current command value I7 has a constant opening degree even if the solenoid current command value based on the steering angle θ, the steering angular velocity ω, and the vehicle speed is zero. While maintaining a constant standby flow rate QS.

Next, the operation of the first embodiment will be described.
Now, during the traveling of the vehicle, the controller C detects the vehicle speed input from the vehicle speed sensor 17 and specifies the control characteristics based on the flowchart shown in FIG. That is, it is determined whether or not the vehicle has continuously traveled on an expressway at 80 km / h for 10 minutes or more. Then, after the high-speed traveling of 80 km / h or more is continued for 10 minutes or more, for example, when the vehicle is greatly decelerated between the expressway and the interchange toll gate, the following problem occurs.

  As described above, during high-speed traveling, the assist force of the power steering device is reduced and the steering feeling of the steering wheel is increased. In this way, after continual operation with a heavy steering feeling, if the above-mentioned assist force is controlled in accordance with the actual vehicle speed, the continuity of the steering feeling is interrupted even if there is a sudden deceleration as described above. It will be.

  Therefore, in the first embodiment, the assist force is not suddenly increased when the vehicle is decelerated by 40 km / h or more, which is the set speed, after continuously traveling at 80 km / h or more for 10 minutes or more. That is, in this case, the vehicle speed signal V is output based on the low gain control characteristic B described above. If the vehicle speed signal V is output based on the low gain control characteristic B as described above, the vehicle speed signal V is smaller than that in the case of the normal control characteristic A even though the actual vehicle speed is the same.

  However, even if the vehicle is traveling at 80km / h or more, if it is not continued for more than 10 minutes, which is the set time, it is assumed that there will be no significant shift in steering feeling even if the vehicle is decelerated greatly. Thus, the controller C outputs the vehicle speed signal V based on the normal control characteristic A. Accordingly, the vehicle speed signal V in this case is larger than the low gain control characteristic B. In any case, in the first embodiment, when there is a sudden deceleration after continuous high-speed running, the vehicle speed signal V is made smaller than when there is no sudden deceleration.

  Then, the controller C calculates current command values I3 and I4 according to the vehicle speed signal V described above. The controller C outputs a steering angle system current command value I5 that is a product of the solenoid current command value I1 based on the steering angle and the steering angle current command value I3, and the solenoid current command value I2 based on the steering angular velocity is The steering angular velocity system current command value I6 is output with the fast steering angular velocity current command value I4 as a limit value.

Then, the magnitude of the current command value I5 for the steering angle system and the current command value I6 for the steering angular velocity system is determined, and the standby current command value I7 is added to the larger command value I5 or I6. The solenoid excitation current I is determined.
The solenoid excitation current I is mainly based on the steering angle system current command value I5 when the vehicle is traveling at high speed, and is mainly based on the steering angle speed system current command value I6 when the vehicle is traveling at low speed.

However, even during low-speed running, the solenoid excitation current I is determined based on the steering angle system current command value I5 during steering.
Even when the vehicle is traveling at a high speed, when the steering is suddenly operated, the excitation current I of the solenoid is determined based on the current command value I6 of the steering angular velocity system.

  According to the first embodiment as described above, when the vehicle is decelerated greatly after continuous high speed running, the calculation unit corrects and outputs the vehicle speed signal V so that it is greater than the vehicle speed before the calculation. The current command values I3 and I4 output based on the vehicle speed signal are reduced. If the current command values I3 and I4 are thus reduced, the excitation current I of the solenoid specified thereafter is calculated based on the current command values I3 and I4. Therefore, the excitation current I that is the calculation result is also calculated. Get smaller. Thus, if the excitation current I of the solenoid is reduced, the assist force is also reduced accordingly, so that the continuity of driving feeling due to the difference in travel speed is not interrupted.

  In the second embodiment shown in FIG. 4, the current command values I3 and I4 are calculated according to the actual vehicle speed, and the controller C returns to the normal control system and the assist force of the power cylinder returns from small to large. This is different from the first embodiment in that it includes a special control system that reduces the ratio. That is, as shown in FIG. 4, a switch SW for switching is provided in the process from the identification of the standby flow rate QS to the solenoid SOL, and this switch SW is normally connected to the position shown in FIG. To keep the position. A special control system can be selected by switching the switch SW.

  When the switch SW as described above is maintained at the position shown in the figure, which is the normal control system, the value obtained by adding the current command value I7 specifying the standby flow rate QS to the current command value I5 or I6 is directly used as the solenoid excitation. It becomes the current I. However, when the switch SW is switched to a position that becomes a special control system opposite to the illustrated position, the current command value of the special control system output unit is output. This special control system output unit outputs a current command value that is decelerated step by step at a constant deceleration value, for example, every 20 km / h.

  Although the said calculating part is provided with the function which calculates the change of the vehicle speed input from the vehicle speed sensor 17, other than that is the same as 1st Embodiment. Therefore, the second embodiment is also controlled based on the flowchart shown in FIG. That is, in step S1, the controller C causes the switch SW to select the normal control system, and in this state, always checks whether the vehicle speed exceeds the set speed of 80 km / h. Unless the speed becomes 80 km / h or higher, the switch SW is kept in the normal control system shown in the figure (step S2). When the vehicle speed reaches 80 km / h or higher, it is determined whether or not the vehicle speed has continued for 10 minutes or more, which is a set time.

  If traveling at 80 km / h or more does not continue for 10 minutes or more, the normal control system is continued. However, when the travel of 80 km / h or more continues for 10 minutes or more, the process proceeds to step S4 to check whether or not the travel of 80 km / h or more has been decelerated by 40 km / h. If there is no deceleration of 40 km / h, the process proceeds to step S3 again, and it is checked whether traveling at 80 km / h or more has continued for 10 minutes or more. When it is determined in step S4 that there has been a deceleration of 40 km / h, the process proceeds to step S5, and the switch SW is switched to the special control system. Further, it is checked whether or not the vehicle speed has reached 40 km / h or less (step S6). If the vehicle speed is 40 km / h or less, the switch SW is switched to the normal control system again.

  However, if the vehicle speed does not reach 40 km / h or less, the process returns to step S5 and the special control system is maintained. Therefore, in this case, a current command value that is decelerated stepwise is output from the special control system output unit every 20 km / h, which is a constant deceleration value. Since the current command value that is decelerated step by step is output in this way, even if there is a sudden deceleration from high-speed traveling, the continuity of driving feeling is maintained as in the first embodiment. Become.

It is explanatory drawing which shows the control system of the controller in 1st Embodiment. It is a graph which shows the control characteristic of 1st Embodiment. It is a flowchart of the control system of 1st Embodiment. It is explanatory drawing which shows the control system of the controller in 2nd Embodiment. It is a flowchart of a 2nd embodiment. It is explanatory drawing which shows the whole structure of the conventional power steering apparatus. It is explanatory drawing which shows the control system of the controller of the conventional power steering apparatus.

Explanation of symbols

I Solenoid current command value I1 Solenoid current command value based on steering angle θ I2 Solenoid current command value based on steering angular velocity ω I3 Steering angle current command value I4 Steering angular velocity current command value QP Control flow rate QT Return flow rate QM Required flow rate (required flow rate)
QS standby flow rate B body 1 spool 2 one pilot chamber 3 other pilot chamber 4 pump port P pump SOL solenoid a variable orifice 8 power cylinder 9 steering valve C controller 16 steering angle sensor 17 vehicle speed sensor T tank

Claims (3)

  A spool is incorporated in the main body, one end of this spool faces one pilot chamber that is always in communication with the pump port, and the other end of the spool faces the other pilot chamber with a spring interposed therebetween. An orifice is provided on the downstream side of the cylinder, and pressure oil is guided to the steering valve that controls the power cylinder through the orifice, while the pressure on the upstream side of the orifice is used as the pilot pressure of the one pilot chamber, and the pressure on the downstream side is set. The control position of the spool is controlled by the pilot pressure of the other pilot chamber, and the movement position of the spool is controlled by the pressure balance between the two pilot chambers, and the pump discharge amount to the steering valve side according to the movement position, and the tank Alternatively, the flow rate is distributed to the return flow rate QT to be returned to the pump, and the orifice is A variable orifice that controls the opening degree according to the exciting current I of the noid is provided, and a controller that controls the exciting current I of the solenoid of the variable orifice is provided, and a steering angle sensor is connected to the controller, and the steering While calculating or storing the steering angle θ and the steering angular velocity ω corresponding to the steering angle from the angle sensor, the controller calculates the solenoid current command value I1 corresponding to the steering angle θ and the solenoid current command value corresponding to the steering angular velocity ω. In the power steering apparatus configured to store or calculate I2 and control the exciting current I of the solenoid of the variable orifice based on the current command values I1 and I2, the controller determines whether or not the vehicle is traveling at a set speed or higher. A function to judge, a function to count the running state time above the set speed, and the set speed A function for determining whether or not the running state has continued for a set time or more, and a function for determining whether or not the running speed has been reduced by a set value or more after continuously running for a set time or more and a set time or more; And a function of controlling the excitation current I of the solenoid in order to reduce the rate of return when the assist force of the power cylinder returns from small to large when the power cylinder is decelerated beyond a set value.   The controller stores at least two types of vehicle speed signal control characteristics, which are functions of the vehicle speed and a current command value related to the vehicle speed, a normal control characteristic and a low gain control characteristic. Judgment is made whether or not the vehicle has traveled continuously, and after the vehicle has continuously traveled for more than the set speed and for more than the set time, the vehicle speed signal is output based on the low gain control characteristics when the travel speed is decelerated by more than the set value. However, if the vehicle is traveling within the set time even if it is below the set speed, or above the set speed, or if it continues running for more than the set time, and the subsequent deceleration value is below the set speed, The power steering apparatus according to claim 1, wherein the vehicle speed signal is output based on normal control characteristics.   The controller is equipped with a normal control system and a special control system that reduces the rate of return when the assist force of the power cylinder returns from small to large. Judgment is made, and after running continuously over the set speed and over the set time, when the running speed is decelerated over the set value, the special control system is selected and the set time even if it is below the set speed or over the set speed 2. The power according to claim 1, wherein the normal control system is selected when the value of the subsequent deceleration is equal to or lower than the set speed even when the vehicle is traveling within a predetermined time or is continuously running for a set time or longer. Steering device.

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