JP2007161058A - 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 computing part 21 and an electric current command value conversion part 22 are provided on a controller C, the computing part 21 memorizes a table specifying a control flow rate value TQ corresponding to a travelling state, the electric current command value conversion part 22 memorizes a conversion table 23 to specify a relative relation between the control flow rate value TQ and a solenoid electric current command value I for each of real machines to correspond to the control flow rate value TQ, the computing part 21 specifies the control flow rate value TQ in accordance with a signal output from a signal output part 20 and the electric current command value conversion part 22 specifies the solenoid electric current command value I for each of the real machines from the control flow rate value TQ in accordance with the conversion table 23 and controls an exciting electric current of a solenoid SOL of a variable orifice (a) in accordance with this solenoid electric current command value I. <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. 4 and 5.
The pump assembly PA shown in FIG. 4 is one in which the pump P is integrally incorporated in the main body 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 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. 4 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.

  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 in FIG. 5 are determined based on theoretical values that make the relationship between the steering angle θ and the control flow rate QP 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.

  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 the controller C in advance as a table value.

The steering angle current command value I3 is set to 1 in the low speed range and to 0.6, for example, in the maximum speed range. Further, the steering angular velocity current command value I4 is set to 1 in the low speed range, and for example, 0.8 in the maximum speed range.
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 V. Therefore, the higher the vehicle speed V is, the smaller the output value that is the multiplication result, that is, the current command value I5 of the steering angle system.
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 steering angle system current command value I5 outputted as described above is compared with the steering angular velocity system current command value I6, and the larger current command value I5 or current command value I6 is adopted. ing.
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 value 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.

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 different IQ characteristics for each actual machine. Therefore, 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 a calculation unit for calculating a solenoid current command value for outputting an excitation current to be supplied to the solenoid is provided based on a signal output from the signal output unit. A power steering device that controls the variable orifice based on the solenoid current command value calculated by the unit is assumed.

  The controller is provided with a current command value conversion unit together with the calculation unit, the calculation unit stores a table that defines control flow values corresponding to the travel conditions, and the current command value conversion unit is configured to control the control flow rate. A conversion table that identifies the relative relationship between the value and the solenoid current command value for each actual machine corresponding to the control flow value is stored, and the calculation unit specifies the control flow value based on the signal output from the signal output unit The current command value conversion unit specifies the solenoid current command value for each actual machine from the control flow rate value based on the conversion table, and controls the excitation current of the solenoid of the variable orifice based on the solenoid current command value. It is characterized in that it is configured as follows.

According to the present invention, the control flow rate value is calculated in the calculation unit, and the control flow rate value and the solenoid current command value are specified for each actual machine. Therefore, the control caused by the IQ characteristic that varies for each actual machine. Variations in flow rate do not become a problem, and a solenoid current command value corresponding to a required control flow rate can be specified.
Since the solenoid current command value corresponding to the required control flow rate can be specified as described above, the optimum steering feeling can be realized according to the traveling situation.

The power steering apparatus in this embodiment is demonstrated using FIGS. 1-3.
The power steering device of this embodiment has the greatest feature in the control system in the controller C, and the other configurations including the structure 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 current command value conversion 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 calculating unit 21 calculates the steering angle θ and the steering angular velocity ω from the steering angle signal, and outputs a theoretically determined control flow rate value TQ based on the steering angle θ and the steering angular velocity ω.
The relationship between the steering angle θ and the control flow rate value TQ1 in FIG. 1 is determined based on a theoretical value that becomes a linear characteristic. Further, the relationship between the steering angular velocity ω and the control flow rate value TQ2 is also determined based on a theoretical value that has a linear characteristic.

However, if the steering angle θ and the steering angular velocity ω do not become a certain set value or more, both the flow rate values TQ1 and TQ2 output zero. That is, when the steering wheel is neutral or in the vicinity thereof, the flow rate values TQ1 and TQ2 are set to zero.
The control flow rate value TQ1 with respect to the steering angle θ and the control flow rate value TQ2 with respect to the steering angular velocity ω are stored in advance in the calculation unit 21 as table values.

  The computing unit 21 outputs the steering angle gain command value TQ3 and the steering angular speed gain command value TQ4 based on the output signal of the vehicle speed sensor 17, and these steering angle gain command values TQ3. The steering angular velocity gain command value TQ4 is stored in advance in the calculation unit 21 as a table value.

The steering angle gain command value TQ3 is set to 1 in the low speed range and to 0.6, for example, in the maximum speed range. Further, the steering angular velocity gain command value TQ4 is set to output 1 in the low speed range and to output, for example, 0.8 in the maximum speed range.
Then, the control flow rate value TQ1 determined corresponding to the steering angle θ is multiplied by the steering angle gain command value TQ3 corresponding to the vehicle speed V. Therefore, the higher the vehicle speed V is, the smaller the output value as the multiplication result, that is, the control flow value TQ5 of the steering angle system becomes smaller.
On the other hand, for the control flow rate value TQ2 based on the steering angular velocity ω, the steering angular velocity system control flow rate value TQ6 is output with the steering angular velocity gain command value TQ4 corresponding to the vehicle speed as a limit value.

The control flow value TQ5 of the steering angle system output as described above is compared with the control flow value TQ6 of the steering angular velocity system, and the larger control flow value TQ5 or TQ6 is adopted.
Further, the standby flow rate command value TQ7 is added to the control flow rate value TQ5 or TQ6 selected as described above.
This standby flow rate command value TQ7 is for always guiding a predetermined flow rate to the steering valve side via the variable orifice a. Thus, the variable orifice a supplied with the standby flow rate command value TQ7 ensures a constant standby flow rate QS even if the control flow rate value based on the steering angle θ, the steering angular velocity ω, and the vehicle speed is zero. To do.
Note that the table values, calculation methods, and the like stored in advance in the calculation unit 21 in this embodiment are only one embodiment.

As described above, the control flow rate value TQ output from the calculation unit 21 is the required flow rate QM itself that is necessary for realizing an optimum steering feeling under various traveling conditions. Is also the control flow rate QP itself supplied to the steering valve side via the variable orifice a.
In order to actually lead the control flow rate value TQ (control flow rate QP) from the variable orifice a to the steering valve side, the opening degree of the variable orifice a must be adjusted. It is the solenoid SOL that does it. As described above, 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.

That is, in order to control the control flow rate value TQ calculated by the calculation unit 21, a predetermined excitation current is supplied to the solenoid SOL, and the opening degree of the variable orifice a is adjusted to the opening degree for controlling the control flow rate value TQ. It will be. Thus, the current command value conversion unit 22 provided in the controller C outputs the solenoid current command value I for supplying a predetermined excitation current to the solenoid SOL.
The current command value conversion unit 22 converts the control flow rate value TQ calculated by the calculation unit 21 into a solenoid current command value I and outputs it. The control system is as follows.

As shown in FIG. 2, the pump assembly PA has slightly different IQ characteristics for each actual machine. That is, even if the same solenoid current command value I is supplied to the solenoids SOL of the X machine, the Y machine, and the Z machine, the control flow rate QP differs depending on the IQ characteristic. Note that the control flow rate QP here is not different from the control flow rate value TQ, and the IQ characteristic can be grasped by a test or the like when shipping the pump assembly PA. That is, at the time of shipment, the diagram shown in FIG. 2 is held for each actual machine.
Further, for example, in FIG. 2, the coordinate conversion of the solenoid current command value I and the control flow rate QP is performed in FIG. 3, but as is apparent from this figure, it is necessary to control the control flow rate QP. The solenoid current command value I can be specified.

  The current command value conversion unit 22 stores, as the conversion table 23, information that can specify the relative relationship between the control flow rate QP and the solenoid current command value I for each actual machine. The conversion table 23 may be a graph as shown in FIG. 3 or a numerically converted table. In any case, the conversion table 23 may be anything as long as it can identify the relative relationship between the control flow rate QP and the solenoid current command value I for each actual machine.

Next, the operation of the power steering apparatus in this embodiment will be described.
Now, as shown in FIG. 1, as a result of the calculation by the calculation unit 21 receiving the signal from the signal output unit 20, the control flow rate value TQ is specified, and the specified control flow rate value TQ is the current command value. It is sent to the conversion unit 22. The current command value conversion unit 22 checks the control flow value TQ (control flow rate QP) in the conversion table 23 stored in advance, and specifies the solenoid current command value I corresponding to the control flow value TQ in the actual machine. To do.

In other words, the current command value conversion unit 22 converts the control flow rate value TQ based on the conversion table 23 to specify the solenoid current command value I, and the specified solenoid current command value I is supplied to the solenoid SOL. The
In this way, a solenoid current command value I which is necessary for controlling the control flow rate value TQ and is slightly different for each actual machine is supplied to the solenoid SOL, and the variable orifice corresponding to the control flow value TQ for each actual machine. The opening degree of a is controlled.

  According to the power steering device of this embodiment, the control flow rate value TQ is calculated in the calculation unit 21, and the control flow rate value TQ and the solenoid current command value I are specified for each actual machine. Therefore, variations in the control flow rate QP caused by individual IQ characteristics in the actual machine do not matter, and the control flow rate QP controlled by the variable orifice a can be reliably matched with the control flow rate value TQ. Therefore, an optimal 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 figure which shows the IQ characteristic for every real machine. It is a figure which shows the QI characteristic which coordinate-transformed the IQ characteristic of X machine. 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 Current command value conversion part 23 Conversion table C Controller P Pump a Variable orifice TQ Control flow rate value QP Control flow rate QT Return flow rate 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 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 according to the excitation current of the noid and a controller that controls the excitation current of the solenoid are provided, and this controller outputs a signal that corresponds to the driving situation such as the vehicle speed and steering angle. In addition to connecting the output unit, a calculation unit for calculating a solenoid current command value for outputting the excitation current supplied to the solenoid is provided based on the signal output from the signal output unit. In the power steering apparatus that controls the variable orifice based on the solenoid current command value, the controller is provided with a current command value conversion unit along with the calculation unit, and the calculation unit controls the control flow rate value TQ corresponding to the travel situation. The current command value conversion unit stores a control flow value TQ and an actual value corresponding to the control flow value TQ. A conversion table for specifying a relative relationship with each solenoid current command value is stored, and the calculation unit specifies a control flow value TQ based on a signal output from the signal output unit, and the current command value conversion unit is A power steering device configured to identify a solenoid current command value for each actual machine from the control flow rate value TQ based on the conversion table and to control the excitation current of the solenoid of the variable orifice based on the solenoid current command value.

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