JP4412111B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering apparatus.

  2. Description of the Related Art Conventionally, in a hydraulic power steering apparatus including a hydraulic pump and a power cylinder that applies assist force to a steering system based on the hydraulic pressure, a distribution ratio of fluid (pressure oil) returning to the hydraulic pump is changed. Some have a flow rate control valve (flow rate control device) that can change the flow rate (supply flow rate) of the pressure oil supplied to the power cylinder.

For example, the power steering device described in Patent Document 1 secures a necessary and sufficient supply flow rate according to the vehicle state by changing the supply flow rate according to the vehicle speed, the steering angle, and the steering speed (assist mode). In a state where the assist request is low, the supply flow rate is set smaller than the flow rate in the assist mode (standby mode). By adopting such a configuration, the steering system is given the optimum assist force according to the vehicle condition to improve the steering feeling, and the pressure loss during non-assist is suppressed to reduce the energy consumption. Can be planned.
JP 2001-163233 A

  By the way, in such a variable flow rate power steering apparatus, a value corresponding to a non-following region in the vehicle traveling direction with respect to steering, that is, a “dead zone” is set as a threshold value, and “assist” is set when the steering angle is larger than the threshold value when the vehicle travels. In general, the mode is switched based on the comparison between the steering angle and the threshold value, such as “standby” when the value is equal to or less than the threshold value.

However, the dead zone in the vicinity of the steering neutral changes in the angular range according to the vehicle speed, and is relatively wide in the low speed region and narrow in the high speed region.
Therefore, in the conventional method, the predetermined threshold is set to be smaller in the low speed region and larger in the high speed region than the ideal switching point (angle) of each mode, and as a result, in the low speed region. There is a problem that it is difficult to shift from the assist mode to the standby mode, and conversely, in the high speed region, it is difficult to shift from the standby mode to the assist mode.

  In particular, in a device provided with a transmission ratio variable device that varies the transmission ratio between the steering wheel and the steering wheel according to the vehicle state, the steering torque characteristic (MA-MT) with respect to the steering angle is controlled by the variable gear ratio control. Changes. For this reason, the ideal switching point of each mode also changes constantly, making it difficult to switch the standby / assist mode appropriately.

  The present invention has been made to solve the above-described problems, and the object thereof is to provide an optimal assist force according to the vehicle state and to more effectively reduce energy consumption. The object is to provide a power steering device.

  In order to solve the above problems, the invention according to claim 1 is directed to a hydraulic pump, a power cylinder that applies an assist force to a steering system based on the hydraulic pressure, and a distribution ratio of pressure oil that recirculates to the hydraulic pump. The power steering device includes a flow rate control device capable of changing the flow rate of the pressure oil supplied to the power cylinder by changing the flow rate, and a control means for controlling the flow rate control device. A transmission ratio variable device that varies a transmission ratio between the steering wheel and the steering wheel by adding a second steering angle of the steering wheel based on motor drive to a first steering angle of the steering wheel based on the steering wheel; Computing means for computing a target rudder angle of the steered wheel based on a control target amount of the second rudder angle, wherein the control means provides the flow for applying the assist force. And a standby mode in which the flow rate is smaller than the flow rate in the assist mode, and when the vehicle is traveling, the assist mode or the standby mode is determined based on a comparison between the target rudder angle and a threshold value. The gist is that the threshold value is increased as the vehicle speed becomes lower while switching.

  According to a second aspect of the present invention, a hydraulic pump, a power cylinder that applies an assist force to a steering system based on the hydraulic pressure, and a distribution ratio of the pressure oil that returns to the hydraulic pump are changed to the power cylinder. A power steering device comprising a flow rate control device capable of changing a flow rate of supplied pressure oil and a control means for controlling the flow rate control device, wherein the first steering angle of a steered wheel based on a steering angle of a steering wheel A transmission ratio variable device for varying a transmission ratio between the steering wheel and the steered wheel by adding a second steered angle of the steered wheel based on a motor drive to the steering wheel, based on the second steered angle Computation means for computing the actual steering angle of the steered wheel, the control means, assist mode for ensuring the flow rate for applying the assist force, and the flow rate A standby mode that is smaller than the flow rate in the cyst mode, and when the vehicle travels, the assist mode or the standby mode is switched based on a comparison between the actual steering angle and a threshold value, and the vehicle speed decreases as the vehicle speed decreases. The main point is to increase the threshold.

  According to a third aspect of the present invention, a hydraulic pump, a power cylinder that applies an assist force to a steering system based on the hydraulic pressure, and a distribution ratio of the pressure oil that returns to the hydraulic pump are changed to the power cylinder. A power steering apparatus comprising a flow rate control device capable of changing a flow rate of pressure oil to be supplied and a control means for controlling the flow rate control device, wherein the control means provides the flow rate for applying the assist force. And a standby mode in which the flow rate is smaller than the flow rate in the assist mode. When the vehicle is traveling, the assist mode or standby mode is based on a comparison between the steering angle of the steering wheel and a threshold value. The gist is that the threshold is increased as the vehicle speed decreases.

  According to each of the above configurations, the threshold used for the standby / assist mode switching determination during vehicle travel increases as the vehicle speed decreases. Therefore, in the low speed range where the dead zone range is relatively wide, the switching determination is performed. In a high-speed region where the threshold value is large and the dead zone range is relatively narrow, the switching determination threshold value is small. As a result, in the dead zone where the assist request is low, the flow control mode can be accurately switched to the standby mode, and as a result, an optimum assist force according to the vehicle state is applied to the steering system to improve the steering feeling. At the same time, it is possible to reduce energy consumption by suppressing pressure loss during non-assist.

  In particular, in the configuration according to claim 1 or 2, the switching determination of the standby / assist mode is performed based on the angle of the steering wheel, not the angle of the steering hole. Therefore, regardless of the change in the transmission ratio between the steering wheel and the steered wheels, the flow rate control modes can be switched at an appropriate timing, and as a result, energy consumption can be more effectively reduced. become.

  Furthermore, in the configuration of claim 1, since the variable flow rate control is performed using the target steering angle instead of the actual steering angle of the steered wheels, the variable flow rate control can be performed at an earlier timing. Feeling can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, while providing the optimal assist force according to a vehicle state, the power steering apparatus which can aim at reduction of energy consumption more effectively can be provided.

Hereinafter, an embodiment in which the present invention is embodied in a power steering apparatus including a transmission ratio variable device will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a power steering apparatus 1 of the present embodiment. As shown in the figure, a steering shaft 3 to which a steering wheel (steering) 2 is fixed is connected to a rack 5 via a rack and pinion mechanism 4. It is converted into a reciprocating linear motion of the rack 5 by the and pinion mechanism 4. Then, by changing the rudder angle of the steered wheels 6, that is, the tire angle, by the reciprocating linear motion of the rack 5, the traveling direction of the vehicle is changed.

  The power steering device 1 according to the present embodiment is a hydraulic power steering device including a hydraulic pump 11 and a power cylinder 12 that applies an assist force to a steering system based on the hydraulic pressure, and is pumped from the hydraulic pump 11. The fluid (pressure oil) is introduced into the power cylinder 12 provided in the rack 5 via the control valve 13. Then, the rack 5 is pressed in the moving direction by the fluid pressure flowing into the power cylinder 12 so that an assist force is applied to the steering system.

  The control valve 13 is provided on a pinion shaft (not shown) to which the steering shaft 3 is connected, and the control valve 13 twists a torsion bar (not shown) accompanying the application of steering torque to the steering system. Based on the above, the direction of fluid introduction to the power cylinder 12 and the flow rate thereof are controlled. When no assist force is applied to the steering system, the fluid does not flow into the power cylinder 12 but returns to the hydraulic pump 11 from the control valve 13 via a reservoir tank (not shown). Yes.

  Further, the power steering device 1 of the present embodiment includes a flow rate control valve 15 as a flow rate control device capable of changing the fluid flow rate supplied to the power cylinder 12, and a first control means as a control means for controlling the operation of the flow rate control valve 15. 1 ECU (VFC ECU) 16.

  As shown in FIG. 2, in this embodiment, the hydraulic pump 11 includes a pump port 22 for pumping the fluid discharged from the pump body 21 to the control valve 13, and a return for introducing the fluid into the pump body 21. The flow control valve 15 is incorporated in the hydraulic pump 11. Then, the flow rate control valve 15 changes the fluid flow rate fed back from the pump port 22, that is, the fluid flow rate supplied to the power cylinder 12, by changing the distribution ratio of the fluid returning from the pump port 22 to the return port 23. To do.

  Specifically, the flow control valve 15 includes a variable orifice 24 provided in the pump port 22, a first pressure chamber 25 a communicating with the pump port 22 on the upstream side of the variable orifice 24, and the pump port 22 on the downstream side thereof. A second pressure chamber 25b communicated with the spool 26 is provided that moves in the axial direction (left-right direction in the figure) in accordance with the pressure difference between the two pressure chambers.

  In the present embodiment, the spool 26 is urged toward the first pressure chamber 25 a by a spring 27 disposed in the second pressure chamber 25 b, and the spool 26 is urged toward the first pressure chamber by the resistance of the variable orifice 24. When the pressure of 25a becomes larger than the sum of the pressure of the 2nd pressure chamber 25b and the elastic force of the spring 27, it moves to the position according to the pressure difference.

  The flow control valve 15 has a return flow path 28 that allows the first pressure chamber 25a and the return port 23 to communicate with each other. In the return flow path 28, the spool 26 moves to the second pressure chamber 25b side. The opening area to the first pressure chamber 25a, that is, the flow path cross-sectional area is set to be large. Based on the movement of the spool 26, the flow control valve 15 recirculates the fluid having a flow rate corresponding to the movement position from the pump port 22 to the return port 23.

  On the other hand, a solenoid 29 that is a drive source of the variable orifice 24 is connected to a first ECU (VFCUCU) 16, and the first ECU (VFCECU) 16 controls the voltage applied to the solenoid 29 to thereby change the variable orifice. The opening degree (throttle amount) of 24 is controlled. Then, the spool 26 moves to a position corresponding to the opening of the variable orifice 24, and the distribution ratio of the fluid returned to the pump body 21 changes, so that the fluid flow rate pumped from the hydraulic pump 11 to the control valve 13 is reached. Is controlled (variable flow control).

  As shown in FIG. 1, the power steering device 1 according to the present embodiment has a ratio of a steering angle (tire angle) of the steered wheels 6 to a steering angle (steering angle) of the steering wheel 2, that is, a transmission ratio (gear ratio). And a second ECU (IFSECU) 31 for controlling the operation of the variable gear ratio actuator 30. In this embodiment, the gear ratio variable actuator 30 constitutes a transmission ratio variable device.

  More specifically, the steering shaft 3 includes a first shaft 32 to which the steering 2 is connected and a second shaft 33 connected to the rack and pinion mechanism 4. The gear ratio variable actuator 30 includes the first shaft 32 and the first shaft 32. A differential mechanism 34 for connecting the two shafts 33 and a motor 35 for driving the differential mechanism 34 are provided. The gear ratio variable actuator 30 adds the rotation driven by the motor to the rotation of the first shaft 32 accompanying the steering operation and transmits the rotation to the second shaft 33, so that the steering shaft input to the rack and pinion mechanism 4. The rotation of 3 is increased (or decelerated).

  That is, as shown in FIGS. 3 and 4, the gear ratio variable actuator 30 is configured such that the steered angle (ACT angle θta) of the steered wheels based on the motor drive is changed to the steered angle (steer steered angle θts) of the steered wheels 6 based on the steering operation. ) Is added, the gear ratio of the steered wheels 6 with respect to the steering angle θs is varied. The second ECU (IFSECU) 31 controls the gear ratio variable actuator 30 by controlling the operation of the motor 35. That is, the second ECU (IFSECU) 31 varies the gear ratio by controlling the ACT angle θta (gear ratio variable control).

  In this case, “addition” is defined to include not only addition but also subtraction, and so on. Further, when the “gear ratio of the steered wheels 6 with respect to the steering angle θs” is expressed as an overall gear ratio (steering angle θs / tire angle θt), an overall increase is made by adding the ACT angle θta in the same direction as the steering angle θts. The gear ratio becomes smaller (large tire angle θt, see FIG. 3). Then, the overall gear ratio is increased by adding the ACT angle θta in the reverse direction (small tire angle θt, see FIG. 4). In this embodiment, the steer turning angle θts constitutes the first rudder angle, and the ACT angle θta constitutes the second rudder angle.

Next, the electrical configuration of the power steering apparatus of this embodiment and its control mode will be described.
As shown in FIG. 1, in the present embodiment, a first ECU (VFC ECU) 16 that controls the flow rate control valve 15 and a second ECU (IFSECU) 31 that controls the gear ratio variable actuator 30 are connected to an in-vehicle network (CAN: Controller Area Network) 36 is connected. A steering angle sensor 37, a vehicle speed sensor 38, and a rotation angle sensor 39, which will be described later, are connected to the in-vehicle network 36. The first ECU (VFCECU) 16 and the second ECU (IFSECU) 31 are the steering angle θs, vehicle speed V (and ACT angle θta) detected by these sensors, and the first ECU (VFCECU) 16 and the second ECU (IFSECU). The variable flow rate control and the variable gear ratio control are executed based on a control signal input by mutual communication with the control unit 31.

(Gear ratio variable control)
First, the gear ratio variable control will be described.
FIG. 5 is a control block diagram of the power steering apparatus of the present embodiment. As shown in the figure, the second ECU (IFSECU) 31 includes a microcomputer 41 that outputs a motor control signal, and a drive circuit 42 that supplies drive power to the motor 35 of the gear ratio variable actuator 30 based on the motor control signal. I have.

  The motor 35 of the present embodiment is a brushless motor, and the drive circuit 42 supplies three-phase (U, V, W) drive power to the motor 35 based on the input motor control signal. Each control block shown below is realized by a computer program executed by the microcomputer 41 (and a microcomputer 51 described later).

  The second ECU (IFSECU) 31 controls the operation of the gear ratio variable actuator 30 by controlling the driving power supplied to the motor 35, that is, executes gear ratio variable control.

  The microcomputer 41 has a gear ratio variable control calculation unit 44 that calculates a gear ratio variable ACT command angle θgr *, which is a control target component for changing the gear ratio according to the vehicle speed, and the vehicle responsiveness according to the steering speed. A differential steer control calculation unit (LeadSteer control calculation unit) 45 that calculates a differential steer ACT command angle θls *, which is a control target component for improvement, is provided.

  In the present embodiment, the vehicle speed V and the steering angle θs are input to the gear ratio variable control calculation unit 44, and the vehicle speed V and the steering speed ωs are input to the differential steer control calculation unit 45. The steering speed ωs is calculated by differentiating the steering angle θs with time (the same applies hereinafter). The gear ratio variable control calculation unit 44 calculates a gear ratio variable ACT command angle θgr * based on the steering angle θs and the vehicle speed V (gear ratio variable control calculation), and the differential steer control calculation unit 45 calculates the vehicle speed. A differential steer ACT command angle θls * is calculated based on V and the steering speed ωs (differential steer control calculation).

  The gear ratio variable ACT command angle θgr * calculated by the gear ratio variable control calculation unit 44 and the differential steer ACT command angle θls * calculated by the differential steer control calculation unit 45 are input to the adder 46. The adder 46 superimposes the gear ratio variable ACT command angle θgr * and the differential steer ACT command angle θls * to calculate an ACT command angle θta *, which is a control target amount of the ACT angle θta (ACT). Command angle calculation).

  The ACT command angle θta * calculated by the adder 46 is input to the FB control (feedback control) calculation unit 47. In the present embodiment, the motor 35 of the variable gear ratio actuator 30 is provided with a rotation angle sensor 39 (see FIG. 1), and the ACT angle θta is detected based on the motor rotation angle detected by the rotation angle sensor 39. It has come to be. Then, the FB control calculation unit 47 calculates a current command value by feedback control based on the ACT angle θta and the ACT command angle θta * (FB control calculation).

  The current command value calculated by the FB control calculation unit 47 is input to the voltage command value calculation unit 48, and the voltage command value calculation unit 48 calculates a voltage command value based on the current command value. Then, the voltage command value calculation unit 48 outputs the voltage command value to the PWM control calculation unit 49 (voltage command value calculation).

  The voltage command value calculated by the voltage command value calculation unit 48 is input to the PWM control calculation unit 49, and the PWM control calculation unit 49 generates (calculates) a motor control signal based on the input voltage command value. To the drive circuit 42 (PWM control calculation). The motor 35 is controlled by the drive power supplied from the drive circuit 42 based on the motor control signal.

  Further, the microcomputer 41 of the present embodiment includes an ACT flag determination unit 50 that performs ON / OFF (set / reset) determination of an ACT flag Fact (IFS Action Flag) used for determination of switching between two flow rate control modes described later. ing. Then, the ACT flag determination unit 50 performs the ON / OFF determination of the ACT flag Fact based on the duty ratio (ONDuty) of the motor control signal output from the PWM control calculation unit 49 (ACT flag determination).

  Specifically, as shown in the flowchart of FIG. 6, the ACT flag determination unit 50 determines whether the duty ratio input from the PWM control calculation unit 49 is greater than a predetermined threshold γ (step 101). ). When the duty ratio is larger than the predetermined threshold γ (step 101: YES), the ACT flag Fact is set to “ON” (step 102), and when the duty ratio is equal to or smaller than the predetermined threshold γ (step 101: NO) sets the ACT flag Fact to “OFF” (step 103).

  The determination result of the ACT flag determination unit 50, that is, the ACT flag Fact is output to the first ECU (VFC ECU) 16 via the in-vehicle network 36.

Next, a calculation processing procedure in the microcomputer 41 on the second ECU side configured as described above will be described.
As shown in the flowchart of FIG. 7, when the microcomputer 41 fetches sensor values from the above sensors as state quantities (step 201), it first performs a gear ratio variable control calculation (step 202), and then performs differential steer control calculation. Perform (step 203). The microcomputer 41 calculates the gear ratio variable ACT command angle θgr * and the differential steer ACT command angle θls * calculated by executing the gear ratio variable control calculation in step 202 and the differential steer control calculation in step 203. By superimposing, the control target ACT command angle θta * is calculated (step 204).

  Next, the microcomputer 41 executes feedback control based on the ACT command angle θta * calculated in step 204 and the ACT angle θta detected by the rotation angle sensor 39 (step 205), and is calculated in step 205. A voltage command value is calculated based on the current command value (step 206). Then, a motor control signal is generated based on the voltage command value, and the motor control signal is output to the drive circuit 42 (step 207).

  Then, the microcomputer 41 performs on / off determination of the ACT flag Fact based on the duty ratio of the motor control signal, and outputs the ACT flag Fact to the first ECU (VFC ECU) 16 (step 208).

(Variable flow control)
Next, flow rate variable control in the power steering apparatus of this embodiment will be described.
As shown in FIG. 5, the first ECU (VFC ECU) 16 is based on a microcomputer 51 that determines a voltage to be applied to the solenoid 29 of the flow control valve 15 (variable orifice 24), and a voltage control signal output from the microcomputer 51. And a drive circuit 52 for applying a drive voltage to the solenoid 29. The first ECU (VFC ECU) 16 controls the operation of the flow control valve 15 by controlling the voltage applied to the solenoid 29, that is, executes flow variable control.

  As shown in FIG. 8, in the power steering device 1 of the present embodiment, sufficient supply corresponding to the vehicle speed is applied to the fluid flow rate (supply flow rate Q) supplied to the power cylinder 12 in order to give the required assist force. Two flow control modes are set: “Assist mode” that secures the flow rate Q, and “Standby mode” in which the supply flow rate Q (standby flow rate Qs) is smaller than the supply flow rate (assist flow rate Qa) in this assist mode. Has been.

  When the assist request is high, the flow rate control mode is set to “assist mode” to ensure a sufficient supply flow rate Q for generating the required assist force. When the assist request is low, “standby mode” is set. By increasing the distribution ratio of the fluid returned to the pump body 21, the pressure loss is suppressed and the energy consumption is reduced.

  As shown in FIG. 5, in this embodiment, the microcomputer 51 calculates the target steering angle of the steered wheels 6, that is, the target tire angle θt *, based on the ACT command angle θta * calculated by the second ECU (IFSECU) 31. A target tire angle calculation unit 53 is provided as a calculation means for performing the calculation. Then, the first ECU (VFC ECU) 16 performs the flow rate variable control based on the target tire angle θt *.

  More specifically, in the present embodiment, the microcomputer 51 receives the ACT command angle θta * calculated in the second ECU (IFSECU) 31 together with the vehicle speed V, the steering angle θs, and the steering speed ωs. The target tire angle calculation unit 53 receives the ACT command angle θta * and the steering angle θs. Then, the target tire angle calculation unit 53 calculates the target tire angle θt * by adding the ACT command angle θta * to the steer turning angle θts (see FIGS. 3 and 4) based on the steering angle θs.

  Note that, as in the gear ratio variable actuator 30 of the present embodiment, the transmission ratio can be varied by increasing (or decelerating) the rotation of the steering shaft 3 input to the rack and pinion mechanism 4. “Tire angle” corresponds to the angle of the pinion shaft, that is, “pinion angle” (tire angle = pinion angle × base gear ratio of rack and pinion). Accordingly, in this case, it is needless to say that the “target tire angle” is the same as the “target pinion angle”.

  The microcomputer 51 also determines a standby / assist determination unit 54 for determining standby / assist mode switching, and a flow rate command value Q that is a control target amount of the supply flow rate Q based on the determination result (standby / assist determination value V_as). And a flow rate command value calculation unit 55 for calculating *.

  In the present embodiment, the target tire angle θt *, the steering speed ωs, the vehicle speed V, and the ACT flag Fact output from the second ECU (IFSECU) 31 are input to the standby / assist determination unit 54. Then, the standby / assist determination unit 54 performs standby / assist mode switching determination based on these input state quantities (standby / assist determination).

  Specifically, when the vehicle is stopped, the standby / assist determination unit 54 determines that the “assist ON ((ON)” is selected when the absolute value of the steering speed ωs is greater than the predetermined threshold value α or the ACT flag Fact is “ON”. Stand-by OFF) ”. Then, in the vehicle running state, the absolute value of the target tire angle θt * with a threshold β as a value corresponding to the angle range of the “dead zone” in the vicinity of the steering neutral, that is, the region where the vehicle traveling direction does not follow the steering operation Is larger than the threshold value β, it is determined that “assist ON (standby OFF)”.

  In addition, the microcomputer 51 of the present embodiment includes a threshold value calculation unit 56 that calculates a threshold value β used for determination of standby / assist mode switching when the vehicle is traveling, and the vehicle speed V is input to the threshold value calculation unit 56. It is like that. Then, the threshold calculator 56 calculates the threshold β based on the input vehicle speed V (threshold calculation).

  Specifically, as shown in FIG. 9, the threshold value calculation unit 56 has a threshold value calculation map 56a in which the threshold value β and the vehicle speed V are associated with each other, and the threshold value calculation map 56a has a low vehicle speed V. Accordingly, the threshold value β is set to be large. Based on the threshold calculation map 56 a, the threshold calculation unit 56 calculates a larger threshold β as the vehicle speed V decreases, and the standby / assist determination unit 54 determines the threshold β calculated by the threshold calculation unit 56. Based on the comparison with the target tire angle θt *, the standby / assist mode switching determination during the vehicle running is executed.

Next, the standby / assist determination procedure will be described.
As shown in the flowchart of FIG. 10, the standby / assist determination unit 54 first determines whether or not the vehicle speed V is 0 (Km / h), that is, whether or not the vehicle is stopped (step 301). ). If it is determined that the vehicle is in a stopped state (V = 0, step 301: YES), it is determined whether or not the absolute value of the steering speed ωs is greater than a predetermined threshold value α (step 302). If it is determined that there is no difference (| V |> 0, step 301: NO), it is determined whether or not the absolute value of the target tire angle θt * is larger than the threshold value β calculated by the above threshold calculation (step 303). ).

In the present embodiment, the threshold value α related to the steering speed ωs is “0 [deg / s]” corresponding to the steering neutral position.
When it is determined in step 302 that the absolute value of the steering speed ωs is larger than the threshold value α (| ωs |> α, step 302: YES), or in step 303, the absolute value of the target tire angle θt * is larger than the threshold value β. Is also larger (| θt * |> β, step 303: YES), it is determined that “assist ON (standby OFF)” (step 304).

  In this embodiment, when it is determined in step 302 that the absolute value of the steering speed ωs is equal to or less than the threshold value α (| ωs | ≦ α, step 302: NO), the ACT flag Fact is subsequently set to “ON. Is determined (step 305). If the ACT flag Fact is “ON” (Fact = ON, step 305: YES), it is determined in step 304 that “assist ON (standby OFF)”.

  That is, in the present embodiment, by determining whether or not the ACT flag Fact indicating that the load is applied to the gear ratio variable actuator 30 when the vehicle is stopped and the steering angle is constant, It is determined whether or not the application of assist force is desirable. When the ACT flag Fact is “ON”, it is determined as “assist ON”, and a sufficient supply flow rate is secured to give the required assist amount.

  On the other hand, when it is determined in step 303 that the absolute value of the target tire angle θt * is equal to or smaller than the threshold value β (| θt * | ≦ β, step 303: NO), or when the ACT flag Fact is not “ON” ( In Fact = OFF, step 305: NO, the standby / assist determination unit 54 sets a “provisional flag” (step 306).

  Next, the standby / assist determination unit 54 determines whether or not the provisional flag has been set for a predetermined time t or longer (step 307). If it is determined that the setting is continued for a predetermined time t or longer (step 307: YES), it is determined that “standby is ON (assist OFF)” (step 308). If it is determined in step 307 that the provisional flag has not been set for a predetermined time t or longer (step 307: NO), it is determined in step 304 that “assist ON (standby OFF)”.

  Then, the standby / assist determination unit 54 performs the standby / assist determination by repeating the processes of steps 301 to 308. In this embodiment, when the standby / assist determination unit 54 determines “assist ON”, the standby / assist determination value V_as is “0”, and when it is determined “standby ON”, the standby / assist determination unit 54 The assist determination value V_as is set to “1”.

  On the other hand, as shown in FIG. 5, the flow rate command value calculation unit 55 includes the standby / assist determination value V_as, the vehicle speed V, and the angular velocity of the target tire angle θt *, which are the determination results in the standby / assist determination unit 54. That is, the target tire angular velocity ωt * is input. The target tire angular velocity ωt * is calculated by differentiating the target tire angle θt * with respect to time (the same applies hereinafter). Then, the flow rate command value calculation unit 55 calculates a flow rate command value Q * corresponding to each mode of standby / assist based on the vehicle speed V and the target tire angular velocity ωt * (flow rate command value calculation).

More specifically, the flow rate command value calculation unit 55 includes a standby flow rate map 55a corresponding to the standby mode and an assist flow rate map 55b corresponding to the assist mode.
The flow rate command value Q * and the vehicle speed V are associated with the standby flow rate map 55a, and the flow rate command value calculation unit 55 determines that the standby / assist determination result is “standby ON (V_as = 1)”. The flow rate command value Q * corresponding to the input vehicle speed V is calculated using the standby flow rate map 55a.

  In this embodiment, in the standby flow rate map 55a, the flow rate command value Q * is set to be a predetermined standby flow rate Qs regardless of the value of the vehicle speed V. Therefore, as shown in FIG. 11, in the standby mode, regardless of the vehicle speed V, a constant flow rate command value Q * (standby flow rate Qs) is calculated.

  On the other hand, the assist flow map 55b is a three-dimensional map in which the flow command value Q * is associated with the vehicle speed V and the target tire angular speed ωt *. The flow command value calculator 55 indicates that the standby / assist determination result is “assist ON”. If (V_as = 0) ", the flow rate command value Q * corresponding to the input vehicle speed V and the target tire angular velocity ωt * is calculated using the assist flow rate map 55b.

  Specifically, in the assist flow map 55b, the flow command value Q * is set so as to decrease as the vehicle speed V increases. The flow rate command value Q * is set so as to increase as the target tire angular velocity ωt * increases. Therefore, as shown in FIG. 11, in the assist mode, a smaller flow command value Q * is calculated as the vehicle speed V increases, and a larger flow command value Q * is calculated as the target tire angular velocity ωt * increases. It has become so.

  Further, the microcomputer 51 of the present embodiment includes a flow rate command value filter calculation unit 57 that moderates the change in the flow rate command value Q *, and the flow rate command value Q * calculated by the flow rate command value calculation unit 55 is: This is input to the flow rate command value filter calculation unit 57. The corrected flow rate command value Q ** corrected by the flow rate command value filter calculation unit 57 is input to the voltage command value calculation unit 58.

  More specifically, the flow rate command value filter calculation unit 57 includes a low-pass filter 57a. Then, the flow rate command value filter calculation unit 57 corrects the flow rate command value Q * using the low-pass filter 57a when the flow rate command value Q * increases (flow rate command value filter calculation).

  For example, as shown in FIG. 12, when the flow rate control mode shifts from the standby mode to the assist mode, the flow rate command value Q * changes in a rectangular waveform from the standby flow rate Qs to the assist flow rate Qa at the time of the mode shift. . Therefore, if the flow rate variable control is executed based on the flow rate command value Q * without performing correction by the flow rate command value filter calculation unit 57, the steering feeling may be deteriorated due to a sudden change in assist force.

  In view of this point, in the present embodiment, the flow rate command value Q * is corrected by the flow rate command value filter calculation unit 57 when shifting from the standby mode to the assist mode. After the mode transition, it rapidly increases from the standby flow rate Qs, and then increases smoothly to the assist flow rate Qa. As a result, it is possible to prevent the steering feeling from deteriorating due to a sudden change in the assist force while ensuring a quick rise of the assist force.

  In the present embodiment, the target tire angular velocity ωt * is input to the flow rate command value filter calculation unit 57 together with the flow rate command value Q *. The flow rate command value filter calculation unit 57 changes the time constant of the low-pass filter 57a in accordance with the target tire angular velocity ωt *.

  Specifically, the flow rate command value filter calculation unit 57 decreases the time constant of the low-pass filter 57a as the target tire angular velocity ωt * increases (see FIG. 13). This ensures a good steering feeling by lowering the increase rate of the supply flow rate at the time of slow steering where it is easy to feel the fluctuation of the assist amount accompanying the flow rate change, while increasing the increase rate of the supply flow rate at the time of sudden steering. It is possible to prevent the occurrence of a feeling of catching due to lack of assist. FIG. 13 is a schematic configuration diagram of a map used for changing the time constant.

  That is, as shown in the flowchart of FIG. 14, when the flow rate command value Q * is input from the flow rate command value calculation unit 55 (step 401), the flow rate command value filter calculation unit 57 first has the flow rate command value Q *. It is determined whether or not has increased (step 402).

  When the flow rate command value Q * increases (step 402: YES), the time constant of the low-pass filter 57a is determined based on the target tire angular speed ωt * (step 403), and the low-pass filter 57a is determined based on the determination. Correction of the used flow rate command value Q * is executed (step 404).

  Then, the flow rate command value filter calculation unit 57 outputs the corrected flow rate command value Q ** calculated by the correction calculation in step 404 to the voltage command value calculation unit 58 (step 405).

  As shown in FIG. 5, the voltage command value calculation unit 58 calculates a voltage command value to be applied to the solenoid 29 of the flow control valve 15 based on the input flow command value Q **, and calculates the voltage command value. This is input to the PWM control calculation unit 59. The PWM control calculation unit 59 generates (calculates) a voltage control signal based on the input voltage command value and outputs it to the drive circuit 52 (PWM control calculation).

  Then, a drive voltage is applied to the solenoid 29 based on the voltage control signal, whereby the operation of the flow control valve 15, that is, the fluid flow rate supplied to the power cylinder 12 is controlled.

  That is, as shown in the flowchart of FIG. 15, when the microcomputer 51 fetches sensor values from the respective sensors as state quantities (step 501), first, based on the ACT command angle θta *, the target tire angle θt * and the target tire An angular velocity ωt * is calculated (step 502).

  Next, the microcomputer 51 calculates a threshold value β used for determination of standby / assist mode switching during vehicle travel based on the vehicle speed V (step 503), and then executes standby / assist determination (step 504). Then, the flow rate command value Q * is calculated by executing the flow rate command value calculation (step 505).

  Next, the microcomputer 51 corrects the flow command value Q * by the flow command value filter calculation (step 506), and calculates the voltage command value based on the corrected flow command value Q ** (step 507). Then, a voltage control signal is generated based on the voltage command value, and the voltage control signal is output to the drive circuit 52 (step 508).

Next, operations and effects of the power steering device 1 of the present embodiment configured as described above will be described.
As described above, the dead zone in the vicinity of the steering neutral changes in the angular range according to the vehicle speed V, and is relatively wide in the low speed region and narrow in the high speed region. Therefore, in a configuration in which standby / assist mode switching determination is made by comparing a certain threshold value with a steering angle as seen in the past, it is difficult to shift from the assist mode to the standby mode in the low speed region, and conversely, the standby mode is in the high speed region. It tends to be difficult to shift from mode to assist mode.

  Based on this point, the microcomputer 51 of the present embodiment increases the threshold value β used for the standby / assist mode switching determination when the vehicle is traveling based on the vehicle speed V as the vehicle speed V decreases. That is, in the low speed region where the dead zone range is relatively wide, it is easy to shift from the assist mode to the standby mode by increasing the switching determination threshold β, and in the high speed region where the dead zone range is relatively narrow. Makes it easier to shift from the standby mode to the assist mode by reducing the threshold value β for switching determination.

  As a result, in the dead zone where the assist request is low, the flow control mode can be accurately switched to the standby mode, and as a result, an optimum assist force according to the vehicle state is applied to the steering system to improve the steering feeling. At the same time, it is possible to reduce energy consumption by suppressing pressure loss during non-assist.

  Furthermore, in the present embodiment, the microcomputer 51 controls the target steering angle of the steered wheels 6 calculated based on the ACT command angle θta * that is the control target amount of the steered angle of the steered wheels 6 based on the motor drive, that is, the target tire angle θt. By comparison between * and the threshold value β, the switching determination of the standby / assist mode when the vehicle is running is performed. Therefore, regardless of the change in the transmission ratio between the steering wheel 2 and the steered wheels 6, the flow rate control modes can be switched at an appropriate timing, and as a result, energy consumption can be more effectively reduced. become able to.

  In particular, since the variable flow control is performed using the target tire angle θt *, which is the target steering angle, instead of the tire angle θt, which is the actual steering angle of the steered wheels 6, the variable flow control can be performed at an earlier timing. As a result, the steering feeling can be further improved.

In addition, you may change each said embodiment as follows.
In the present embodiment, the gear ratio variable actuator 30 varies the transmission ratio by increasing (or decelerating) the rotation of the steering shaft 3 input to the rack and pinion mechanism 4. However, the present invention is not limited to this, and the gear ratio variable actuator may be provided in any of the steering transmission systems (between the steering wheel 2 and the steering wheel 6).

  In the present embodiment, the flow control valve 15 is incorporated in the hydraulic pump 11, and the fluid that is pumped from the pump port 22 by changing the distribution ratio of the fluid returning from the pump port 22 to the return port 23. The flow rate, that is, the fluid flow rate supplied to the power cylinder 12 was changed. However, the present invention is not limited to this, and the flow control valve 15 may be provided at a place other than the hydraulic pump 11. Needless to say, the configuration of the flow control valve 15 is not limited to that shown in FIG.

  In the present embodiment, the microcomputer 51 includes a target tire angle calculation unit 53 that calculates the target tire angle θt * based on the ACT command angle θta *, and the first ECU (VFC ECU) 16 sets the target tire angle θt * to the target tire angle θt *. Based on this, the variable flow control was executed. However, the present invention is not limited to this, and the tire angle θt (see FIGS. 3 and 4), which is the actual steering angle of the steered wheels, is calculated based on the ACT angle θta, and based on the tire angle θt instead of the target tire angle θt *. Thus, variable flow control may be performed. Further, the actual steering angle may be directly detected by a sensor or the like.

  In the present embodiment, the present invention is embodied in a power steering device including a variable transmission ratio device, and the standby / assist mode switching determination during vehicle traveling is performed by comparing the target tire angle θt * and the threshold value β. The threshold value β is increased as the vehicle speed V decreases.

  However, not limited to this, regardless of the presence / absence of a transmission ratio variable device, whether to determine standby / assist mode switching during vehicle travel by comparing the steering angle and the threshold or comparing the tire angle and the threshold The threshold value may be changed according to the vehicle speed (the threshold value increases as the vehicle speed decreases).

  In the present embodiment, the ACT flag determination unit 50 determines whether the ACT flag Fact is on or off based on a comparison between the duty ratio input from the PWM control calculation unit 49 and a predetermined threshold value γ. However, the present invention is not limited to this, and the on / off determination of the ACT flag Fact may be performed by comparing a command value (voltage command value) of the voltage applied to the motor 35 with a predetermined threshold value or a command value (current command) (Value) and a predetermined threshold value.

  Further, a detection means for detecting the actual voltage value of the motor 35 or a detection means for detecting the actual current value of the motor 35 is provided, and the comparison between the actual voltage value and the threshold value or the comparison between the actual current value and the threshold value is performed. The ACT flag Fact may be determined to be on / off based on the above.

  In the present embodiment, two ECUs, ie, a first ECU (VFC ECU) 16 and a second ECU (IFSECU) 31 are provided for each control target. However, the flow rate control valve 15 and the gear ratio variable actuator are integrated with one ECU. It is good also as a structure which performs 30 control.

Next, technical ideas other than the claims that can be understood from the above embodiments will be described.
(A) a hydraulic pump, a power cylinder for applying an assisting force to the steering system based on the hydraulic pressure, and a flow rate of the pressure oil supplied to the power cylinder by changing a distribution ratio of the pressure oil returning to the hydraulic pump A power steering device including a flow rate control device capable of changing the flow rate and a control means for controlling the flow rate control device, comprising a detection means for detecting an actual steering angle of the steered wheel, There is an assist mode for securing the flow rate for applying assist force, and a standby mode in which the flow rate is smaller than the flow rate in the assist mode, and when the vehicle is traveling, the actual steering angle is compared with a threshold value. The assist mode or the standby mode is switched based on the power, and the threshold is increased as the vehicle speed decreases. Tearing device.

The schematic block diagram of a power steering apparatus. The schematic block diagram of a hydraulic pump and a flow control valve. Explanatory drawing of gear ratio variable control. Explanatory drawing of gear ratio variable control. The control block diagram of a power steering device. The flowchart which shows the process sequence of ACT flag determination. The flowchart which shows the arithmetic processing procedure by the microcomputer by the side of 2nd ECU (IFSECU). Explanatory drawing of standby / assist mode. The schematic block diagram of a threshold value calculation map. The flowchart which shows the process sequence of standby / assist determination. Explanatory drawing of flow volume command value calculation. Explanatory drawing of flow volume command value filter calculation. The schematic block diagram of a time constant change map. The flowchart which shows the process sequence of flow volume command value filter calculation. The flowchart which shows the arithmetic processing procedure by the microcomputer by the side of 1st ECU (VFCECU).

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power steering apparatus, 2 ... Steering wheel, 6 ... Steering wheel, 11 ... Hydraulic pump, 12 ... Power cylinder, 15 ... Flow control valve, 16 ... 1st ECU (VFC ECU), 21 ... Pump main body, 22 ... Pump port, DESCRIPTION OF SYMBOLS 23 ... Return port, 24 ... Variable orifice, 26 ... Spool, 28 ... Return flow path, 29 ... Solenoid, 30 ... Gear ratio variable actuator, 31 ... Second ECU (IFSECU), 35 ... Motor, 37 ... Steering angle sensor, 38 DESCRIPTION OF SYMBOLS ... Vehicle speed sensor, 39 ... Rotation angle sensor, 41 ... Microcomputer, 42 ... Drive circuit, 44 ... Gear ratio variable control calculation part, 45 ... Differential steer control calculation part, 46 ... Adder, 47 ... FB control calculation part, 48 ... Voltage command value calculation unit, 49 ... PWM control calculation unit, 50 ... ACT flag determination unit, 51 ... Microcomputer, 52 ... Drive circuit, 53 ... Tire angle calculation unit, 54 ... standby / assist determination unit, 55 ... flow rate command value calculation unit, 55a ... standby flow rate map, 55b ... assist flow rate map, 56 ... threshold value calculation unit, 56a ... threshold value calculation map, 57 ... flow rate command value Filter calculation unit, 57a ... Low pass filter, 58 ... Voltage command value calculation unit, 59 ... PWM control calculation unit, Q ... Supply flow rate, V ... Vehicle speed, θs ... Steering angle, ωs ... Steering speed, θt ... Tire angle, Q * , Q ** ... Flow rate command value, Qa ... Assist flow rate, Qs ... Standby flow rate, θt * ... Target tire angle, ωt * ... Target tire angular velocity, θta ... ACT angle, θta * ... ACT command angle, θts ... Steer steering Angle, θgr *: gear ratio variable ACT command angle, θls *: differential steer ACT command angle, V_as: standby / assist judgment value, Fact: ACT flag (IFS Action Flag), α, β, γ: threshold.

Claims (3)

The flow rate of the pressure oil supplied to the power cylinder can be changed by changing the distribution ratio of the hydraulic pump, the power cylinder for applying assist force to the steering system based on the hydraulic pressure, and the pressure oil returning to the hydraulic pump. A power steering apparatus comprising a flow rate control device and a control means for controlling the flow rate control device,
The transmission ratio between the steering wheel and the steering wheel is varied by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device;
Calculating means for calculating a target rudder angle of the steered wheel based on a control target amount of the second rudder angle;
The control means has an assist mode that secures the flow rate for applying the assist force, and a standby mode in which the flow rate is smaller than the flow rate in the assist mode, and when the vehicle is running, the target steering angle A power steering device characterized in that the assist mode or the standby mode is switched based on a comparison between the threshold value and a threshold value, and the threshold value is increased as the vehicle speed decreases. The flow rate of the pressure oil supplied to the power cylinder can be changed by changing the distribution ratio of the hydraulic pump, the power cylinder for applying assist force to the steering system based on the hydraulic pressure, and the pressure oil returning to the hydraulic pump. A power steering apparatus comprising a flow rate control device and a control means for controlling the flow rate control device,
The transmission ratio between the steering wheel and the steering wheel is varied by adding the second steering angle of the steering wheel based on the motor drive to the first steering angle of the steering wheel based on the steering angle of the steering wheel. A transmission ratio variable device;
A calculation means for calculating an actual steering angle of the steered wheel based on the second steering angle;
The control means has an assist mode that secures the flow rate for applying the assist force, and a standby mode in which the flow rate is smaller than the flow rate in the assist mode. A power steering device characterized in that the assist mode or the standby mode is switched based on a comparison between the threshold value and a threshold value, and the threshold value is increased as the vehicle speed decreases. The flow rate of the pressure oil supplied to the power cylinder can be changed by changing the distribution ratio of the hydraulic pump, the power cylinder for applying assist force to the steering system based on the hydraulic pressure, and the pressure oil returning to the hydraulic pump. A power steering apparatus comprising a flow rate control device and a control means for controlling the flow rate control device,
The control means has an assist mode for securing the flow rate for applying the assist force, and a standby mode in which the flow rate is smaller than the flow rate in the assist mode. A power steering device, wherein the assist mode or the standby mode is switched based on a comparison between an angle and a threshold value, and the threshold value is increased as the vehicle speed decreases.

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