JP2007161059A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device to certainly control a necessary flow rate even when a pump assembly PA has an individual I-Q characteristic. <P>SOLUTION: A controller C is furnished with a correction commanding part 22 to correct a logical value computed by a computing part 21. This correction commanding part 22 memorizes a correction table 23 formed in accordance with a relative relation of a logical electric current command value TI and a logical control flow rate QP' and a relative relation of a control flow rate QP and a corrected electric current command value SI specified for each of real machines, and the correction commanding part 22 also specifies the corrected electric current command value SI from the logical electric current command value TI in accordance with the correction table 23, and controls an exciting electric current of a solenoid SOL of a variable orifice (a) in accordance with this corrected electric current command value SI. <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.

A conventional power steering apparatus will be described with reference to FIGS.
A pump assembly PA shown in FIG. 6 is one in which a pump P is integrated into a main body together with a spool 1 of a 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 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 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.

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, but the tank port 11 is opened at the balanced position. The degree is decided.
When the pump P is driven from the normal position in FIG. 6 and pressure oil is supplied to the pump port 4, a flow is 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.

  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 flow rate supplied 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 flow rate 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 required (required) flow rate QM of the power cylinder 8 determined by the steering torque and the control flow rate QP determined by the flow 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.

As described above, in order to make the control flow rate QP as close as possible to the necessary flow rate QM of the power cylinder 8, the opening of the variable orifice a is controlled by the excitation current for the solenoid SOL, 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.

  Reference numeral 19 denotes a driver connected between the controller C and the solenoid SOL. Reference numeral 12 denotes a power source, reference numerals 13 and 14 denote orifices provided in the flow path 10, and reference numeral 15 denotes a relief valve.

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. The controller C calculates the steering angle θ and the steering angular velocity ω from the steering angle signal, and controls the solenoid current command value I based on the steering angle θ and the steering angular velocity ω. I controls the excitation current of the solenoid SOL.
The steering angle θ and the solenoid current command value I1 value I1 in FIG. 7 are determined based on theoretical values in 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 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 value I1 values I1 and I2I2 are set to output zero. That is, when the steering wheel is neutral or in the vicinity thereof, the command value I1 value I1 and I2I2 are set to zero.
The solenoid current command value I1 value I1 for the steering angle θ and the solenoid current command value I2 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 value I3 and the steering angular velocity current command value I4 value I4 based on the output signal of the vehicle speed sensor 17, and these steering angle currents are output. The command value I3 value I3 and the steering angular velocity current command value I4 value I4 are stored in the controller C in advance as table values.

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.
Then, the solenoid current command value I1 based on the steering angle θ is multiplied by the steering angle current command value I3 value I3 corresponding to the vehicle speed V. Therefore, the higher the vehicle speed V is, the smaller the output value that is the multiplication result, that is, the steering angle system current command value I5 value I5.
On the other hand, for the solenoid current command value I2 value I2 based on the steering angular velocity ω, the steering angular velocity current command value I6 value I6 is output with the steering angular velocity current command value I4 value I4 corresponding to the vehicle speed as a limit value. Yes.

The steering angle system current command value I5 value I5 and the steering angular velocity system current command value I6 value I6 are compared in magnitude, and the larger current command value I5 value I5 or current command value is compared. The I6 value I6 is adopted.
The standby current command value I7 value I7 is added to the current command value I5 value I5 or I6I6 selected as described above.
This standby current command value I7 value I7 is for always supplying a predetermined current to the solenoid SOL of the variable orifice a. Thus, the variable orifice a to which the standby current command value I7 value I7 is supplied has its 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, a constant standby flow rate QS is secured.

According to the power steering device configured as described above, the solenoid current command value I is controlled based on the steering angle θ, the steering angular velocity ω, and the vehicle speed V, and the excitation current of the solenoid SOL is controlled by the solenoid current command value I. ing.
As described above, when the solenoid SOL is in the non-excited state, the opening of the variable orifice a is kept to a minimum, and if the exciting current of the solenoid SOL increases according to the vehicle speed and the steering situation, Opening is increased. Thus, by controlling the opening degree of the variable orifice a, it is possible to reduce the energy loss and to control the control flow rate QP according to the traveling state.
JP 2001-260917 A

According to the above-described conventional power steering apparatus, if the solenoid current command value I is calculated, the optimal control flow rate QP can be controlled theoretically in accordance with the traveling situation.
However, the pump P currently has slightly different characteristics for each pump P, such as variations in dimensional accuracy, and the solenoid SOL also has slightly different characteristics. Thus, since the pump assembly PA is configured by combining the pump P having individual characteristics and the solenoid SOL, the correspondence relationship between the solenoid current command value I and the control flow rate QP The IQ characteristics, which are pump output characteristics, are not always the same in all actual machines, and variations occur among the actual machines.

Thus, even if the solenoid current command value I is controlled so as to control the optimum control flow rate QP according to the traveling situation, the pump assembly PA actually has IQ characteristics for each actual machine. The control flow rate QP cannot be accurately controlled, and the control flow rate QP varies.
If the control flow rate QP varies, there is a problem that it becomes impossible to realize an optimum steering feeling according to the traveling state.

  An object of the present invention is to provide a power steering device that reliably controls a required flow rate even when the pump assembly PA has individual IQ characteristics.

  The present invention incorporates a spool into 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 one 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 control flow that guides the pump discharge amount to the steering valve side according to the movement position while controlling the movement position of the spool by the pressure balance of the other pilot chamber, with the pressure on the side as the pilot pressure of the other pilot chamber The QP and the return flow rate QT to be returned to the tank or pump are distributed to The switch is a variable orifice that controls the opening according to the excitation current of the solenoid, and a controller that controls the excitation current of the solenoid is provided. This controller has a signal that corresponds to the running conditions such as the vehicle speed and steering angle. Is connected to a signal output unit, and based on the signal output from this signal output unit, a calculation unit is provided for calculating the theoretical value of the current supplied to the variable orifice, and the theoretical value calculated by this calculation unit Based on the above, a power steering device for controlling the variable orifice is assumed.

  The controller includes a correction command unit that corrects the theoretical value calculated by the calculation unit. The correction command unit includes a relative relationship between the theoretical current command value and the theoretical control flow rate QP ′, and control. The correction table created based on the relative relationship between the flow rate QP and the corrected current command value specified for each actual machine is stored, and the correction command unit is configured to change the corrected current from the theoretical current command value based on the correction table. A feature is that the command value is specified and the excitation current of the solenoid of the variable orifice is controlled in accordance with the corrected current command value.

According to the present invention, since the correction control is performed on the solenoid side that can be easily corrected, the variation in the control flow rate QP caused by the IQ characteristic of each pump assembly PA is almost different for each actual machine. It does not occur.
That is, the pump P causes dimensional variations individually, but the dimensional variations of the pump P cannot be substantially corrected. However, according to the present invention, the corrected current command value corresponding to the characteristics of each actual machine is specified from the theoretical current command value, and the solenoid of the variable orifice that can be easily corrected is controlled by this corrected current command value. ing. Therefore, the control flow rate QP of the pump assembly PA can be brought close to the theoretical control flow rate QP ′.
Since the control flow rate QP can be brought close to the theoretical control flow rate QP ′, an optimum steering feeling can be realized according to the traveling situation.

The power steering apparatus in this embodiment is demonstrated using FIGS.
The power steering device of this embodiment has the greatest feature in the control system in the controller C, and the other configurations are the same as those of the conventional power steering device. Therefore, here, the control system in the controller C will be mainly described, and the same components as those in the conventional power steering apparatus will be described with the same reference numerals.

The control system of the controller C in this embodiment is as shown in FIG. 1, but this controller C controls the opening of the variable orifice a by controlling the exciting current supplied to the solenoid SOL. .
The controller C is connected to the steering angle sensor 16 and the vehicle speed sensor 17 as in the conventional power steering device, and both the sensors 16 and 17 constitute the signal output unit 20 in the present invention. The signal output unit 20 in this embodiment includes the steering angle sensor 16 and the vehicle speed sensor 17, but the signal output unit 20 is not limited to these and controls the control flow rate QP. Therefore, an effective component may be added to the component.

The controller C includes a calculation unit 21 and a correction command unit 22, and a steering angle signal from the steering angle sensor 16 and a vehicle speed signal from the vehicle speed sensor 17 are input to the calculation unit 21. The computing unit 21 computes the steering angle θ and the steering angular velocity ω from the steering angle signal, and outputs a theoretical current command value TI based on the steering angle θ and the steering angular velocity ω.
The steering angle θ and the theoretical steering angle current command value T1 in FIG. 1 are determined on the basis of theoretical values in which the relationship between the steering angle θ and the control flow rate QP is linear. The relationship between the steering angular velocity ω and the theoretical steering angular velocity current command value T2 is also determined based on a theoretical value at which the steering angular velocity ω and the control flow rate QP have 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 T1 and T2 output zero. That is, when the steering wheel is neutral or in the vicinity thereof, the command values T1 and T2 are set to zero.
The theoretical steering angular current command value T1 for the steering angle θ and the theoretical steering angular velocity current command value T2 for the steering angular velocity ω are stored in the calculation unit 21 in advance as table values.

  The computing unit 21 outputs the steering angle current command value T3 and the steering angular speed current command value T4 based on the output signal of the vehicle speed sensor 17, and these steering angle current command values T3. The steering angular velocity current command value T4 is stored in advance in the calculation unit 21 as a table value.

The steering angle current command value T3 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 T4 is set to output 1 in the low speed range and to output, for example, 0.8 in the maximum speed range.
The theoretical steering angle current command value T1 based on the steering angle θ is multiplied by the steering angle current command value T3 corresponding to the vehicle speed V. Therefore, the higher the vehicle speed V is, the smaller the output value, that is, the steering angle system current command value T5, which is the multiplication result.
On the other hand, for the theoretical steering angular velocity current command value T2 based on the steering angular velocity ω, the steering angular velocity current command value T6 is output with the steering angular velocity current command value T4 corresponding to the vehicle speed as a limit value.

The steering angle system current command value T5 output as described above is compared with the steering angular velocity system current command value T6, and the larger current command value T5 or T6 is adopted.
The standby current command value T7 is added to the current command value T5 or T6 selected as described above.
The standby current command value T7 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 T7 has its opening degree even if the theoretical current command value based on the steering angle θ, the steering angular velocity ω, and the vehicle speed is zero. While maintaining a constant, a constant standby flow rate QS is secured.
Note that the table values, calculation methods, and the like stored in advance in the calculation unit 21 in this embodiment are merely one embodiment.

  As described above, when the opening degree of the variable orifice a is controlled using the theoretical current command value TI output from the calculation unit 21 as the excitation current of the solenoid SOL, the theoretical current command value as shown in FIG. The relationship between TI and the theoretical control flow rate QP ′ is established. Here, the numerical value of the theoretical control flow rate QP 'is shown as an integer so that the correlation between the theoretical control flow rate QP' and the theoretical current command value TI can be easily understood. According to FIG. 2, for example, when the theoretical current command value TI is output at 0.5 ampere, it means that the theoretical control flow rate QP ′ is controlled to 5 L. This theoretical control flow rate QP 'Is equal to the required flow rate QM.

  Further, α in FIG. 2 represents a so-called actual use range, and represents a range in which the theoretical current command value TI is calculated in an actual power steering apparatus. That is, in the calculation unit 21, since the standby current command value T7 is added, the theoretical current command value TI is calculated to be at least 0.2 amperes. Further, in the power steering device of this embodiment, for example, the required flow rate QM does not become 11L or more, and therefore, the theoretical current command value TI is not calculated exceeding 1.0 ampere. In this embodiment, 0.2 to 1.0 ampere is the actual usage range α. Thus, the theoretical current command value TI includes the actual usage range α and the theoretical current command value. The TI is not calculated outside the actual use range α.

On the other hand, as already described, since the pump assembly PA has characteristics for each actual machine, even if the theoretical current command value TI is supplied as the exciting current of the solenoid SOL, the control flow rate QP is theoretically controlled. It does not agree with the flow rate QP ′, and varies depending on the actual machine.
FIG. 3 shows the relationship between the excitation current of the solenoid SOL and the actual control flow rate QP measured for each actual machine. FIG. 3 shows actual measurement of each control flow rate QP when, for example, the excitation current for the solenoid SOL of the actual machines X, Y, and Z is changed. For example, when an excitation current of 0.6 amperes is supplied to each solenoid SOL, it means that the control flow rate QP of 7L is controlled in the real machine X, 5L in the real machine Y, and 6L in the real machine Z.
As described above, the relationship between the excitation current of the solenoid SOL and the actual control flow rate QP, that is, the IQ characteristic is peculiar to each actual machine, but this IQ characteristic ships the pump assembly PA. It can be grasped by a test. In other words, at the time of shipment, the table shown in FIG. 3 is held for each real machine.

Now, as shown in FIG. 4, in the real machine X, it is assumed that the calculation unit 21 that has received the signal from the signal output unit 20 calculates the theoretical current command value TI to 0.6 amperes according to a predetermined rule. . At this time, the theoretical control flow rate QP ′ is 6L, but since this value is equal to the required flow rate QM, it is desirable that the control flow rate QP in the actual machine X is also 6L.
However, in the actual machine X, in order to control the control flow rate QP to 6 L, the excitation current 0.5 amperes of the solenoid SOL must be supplied. Similarly, when the theoretical current command value TI is calculated as 0.7 amperes, the theoretical control flow rate QP ′ is 7 L. In order to control the control flow rate QP to 7 L in the actual machine X, the solenoid SOL Excitation current of 0.6 amps must be supplied. At this time, the current that the actual machine X outputs to control the control flow rate 7L, that is, the current that should be supplied to control the control flow rate QP of the same amount as the theoretical control flow rate QP ′ in the actual machine X, This is referred to as a corrected current command value SI.

FIG. 5 shows the theoretical current command value TI and the corrected current command value SI in association with each other based on the theoretical control flow rate QP ′ (actual control flow rate QP).
The table shown in FIG. 5 is the correction table 23 in this embodiment, and this correction table 23 is stored in the correction command unit 22 provided in the controller C.

Now, as shown in FIG. 1, the calculation unit 21 of the controller C receives the signal output from the signal output unit 20, calculates and calculates the theoretical current command value TI according to a predetermined rule, The calculated theoretical current command value TI is transmitted to the correction command unit 22. The correction command unit 22 that has received the theoretical current command value TI corrects the theoretical current command value TI to the corrected current command value SI based on the stored correction table 23. For example, as shown in FIG. 5, when the theoretical current command value TI is 0.4 amperes, the corrected current command value SI = 0.3, and when the theoretical current command value TI is 0.7 amperes, the correction is made. Outputs the current command value SI = 0.6.
As described above, the correction command unit 22 corrects the theoretical current command value TI calculated and calculated by the calculation unit 21 to the corrected current command value SI based on the correction table 23 stored in advance for each actual machine. Output.
Then, the solenoid SOL of the variable orifice a is controlled in accordance with the corrected current command value SI output from the correction command unit 23.

  Note that the actual use range α in this embodiment is the theoretical current command value TI = 0.2 to 1.0 amperes, and thus is essentially out of 0.2 to 1.0 amperes and the solenoid SOL. The exciting current is not supplied. However, since the theoretical current command value TI is corrected to the corrected current command value SI in accordance with the IQ characteristic for each actual machine and is output, in this embodiment, the solenoid SOL outside the actual use range α. The exciting current is supplied.

According to the power steering device of this embodiment, since the correction control is performed on the solenoid SOL side that can be easily corrected, the control flow rate QP caused by the IQ characteristic of each pump assembly PA is controlled. There is almost no variation.
That is, the pump P causes dimensional variations individually, but the dimensional variations of the pump P cannot be substantially corrected. However, according to the present invention, the corrected current command value SI corresponding to the characteristics of each actual machine is specified from the theoretical current command value TI, and the variable orifice solenoid that can be easily corrected by the corrected current command value SI. SOL is controlled. Therefore, the control flow rate QP of the pump assembly PA can be brought close to the theoretical control flow rate QP ′.
Since the control flow rate QP can be brought close to the theoretical control flow rate QP ′, an optimum steering feeling can be realized according to the traveling situation.

It is a figure which shows the control system of the controller C in the power steering apparatus of this embodiment. It is a table | surface which shows the relationship between theoretical electric current command value TI and theoretical control flow volume QP '. It is the table | surface which showed the relationship between the exciting current of solenoid SOL, and the actual control flow volume QP measured for every real machine. It is a figure which shows the flow which converts theoretical electric current command value TI into correction electric current command value SI. It is a table | surface which shows the correction table in this embodiment. It is a figure which shows the structure of the power steering apparatus in the past and this embodiment. It is a figure which shows the control system of the controller C in the conventional power steering apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spool 2 Pilot chamber 3 Pilot chamber 4 Pump port 5 Spring 8 Power cylinder 9 Steering valve 20 Signal output part 21 Calculation part 22 Correction command part 23 Correction table C Controller P Pump a Variable orifice TI Theoretical current command value SI Correction current command Value QP Control flow QP 'Theoretical control flow SOL Solenoid

Claims (1)

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 Or it is configured to distribute to the return flow rate QT to be returned to the pump,
The orifice is a variable orifice that controls the opening degree according to the excitation current of the solenoid, and a controller that controls the excitation current of the solenoid is provided, and this controller has a signal that corresponds to the traveling situation such as the vehicle speed and the steering angle. Is connected to a signal output unit, and based on the signal output from this signal output unit, a calculation unit is provided for calculating the theoretical value of the current supplied to the variable orifice, and the theoretical value calculated by this calculation unit In the power steering apparatus that controls the variable orifice based on the above, the controller includes a correction command unit that corrects the theoretical value calculated by the calculation unit, and the correction command unit includes the theoretical current command value and the theoretical value. It was created based on the relative relationship between the control flow rate QP ′ and the relative relationship between the control flow rate QP and the corrected current command value specified for each actual machine. A correction table is stored, and the correction command unit specifies a correction current command value from a theoretical current command value based on the correction table, and the excitation current of the solenoid of the variable orifice is determined according to the correction current command value. Power steering device configured to control the motor.

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