KR20070022600A - Power steering device - Google Patents

Abstract

A power steering apparatus employing a hydraulic power cylinder, a motor driven pump, and a driving power source for the motor, wherein the power steering control system is configured to be electrically connected to at least the motor and the power source to control the driving state of the motor and the power supply voltage of the power source. do. The power steering control system includes a motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to a steering wheel through a power cylinder, a booster circuit for boosting a power supply voltage, and a motor angle. A motor angular acceleration detection circuit for detecting or predicting an acceleration and a booster-circuit control circuit for controlling the switching between actuation and non-operational states of the booster circuit in response to the motor angular acceleration.

Power steering, motor, motor control circuit, booster circuit, motor angular acceleration detection circuit, booster circuit control circuit

Description

Power Steering Device {POWER STEERING DEVICE}

1 is a system diagram showing a first embodiment of a power steering apparatus.

Fig. 2 is a block diagram showing an input section (input circuit), control section (control circuit) and output section (output circuit) of a controller included in the power steering apparatus of the first embodiment.

3 is a flowchart showing a control routine executed in the controller of the power steering apparatus of the first embodiment;

Fig. 4 is a flowchart showing the control operation of the motor angular acceleration detector and the booster circuit control section included in the power steering control system for the power steering apparatus of the first embodiment.

5 is a characteristic diagram showing basic motor characteristics.

6 (a) to 6 (f) are time charts illustrating the state change of the power steering system component parts of the first embodiment such as a motor and a reversible pump obtained at different steering speeds, that is, at high and low speed steering speeds.

Fig. 7 is a block diagram showing an input section, a control section and an output section of a controller included in the power steering apparatus of the second embodiment.

Fig. 8 is a flowchart showing the control operation of the steering torque change ratio prediction circuit and the booster circuit control section included in the power steering control system for the power steering apparatus of the second embodiment.

Fig. 9 is a system diagram showing a third embodiment of the power steering apparatus.

Fig. 10 is a block diagram showing an input section, a control section and an output section of a controller included in the power steering apparatus of the third embodiment.

Fig. 11 is a flowchart showing the control operation of the steering wheel angular acceleration arithmetic circuit and the booster circuit control section included in the power steering control system for the power steering apparatus of the third embodiment.

Fig. 12 is a block diagram showing an input section, a control section and an output section of a controller included in the power steering device of the fourth embodiment.

Fig. 13 is a flowchart showing the control operation of the PWM duty cycle value change ratio arithmetic circuit and booster circuit control section included in the power steering control system for the power steering apparatus of the fourth embodiment;

Fig. 14 is a block diagram showing an input section, a control section and an output section of a controller included in the power steering apparatus of the fifth embodiment.

Fig. 15 is a flowchart showing the control operation of the current value deviation arithmetic circuit and the booster circuit control section included in the power steering control system for the power steering apparatus of the fifth embodiment.

Fig. 16 is a flowchart showing the control operation of the motor angular acceleration detector and the booster circuit control section included in the power steering control system for the power steering apparatus of the sixth embodiment;

Fig. 17 is a map of a predetermined power supply voltage Ve versus motor angular acceleration threshold value αmfn for the power steering control system of the sixth embodiment.

18 is a system diagram showing the seventh embodiment of the power steering apparatus.

Fig. 19 is a block diagram showing an input section, a control section and an output section of a controller included in the power steering apparatus of the seventh embodiment.

<Description of Symbols for Main Parts of Drawings>

a1: steering wheel

b1: steering shaft

b2: middle shaft

b3: pinion shaft

b4: torque sensor

b5: pinion

b6: steering wheel angle sensor

c1: rack-pinion mechanism

1: motor

2: reversible pump

2a, 2b: first and second ports

3, 4: first and second check valve

5: reservoir tank

6: motor rotation angle sensor

7: vehicle speed sensor

8: Motor-Current Detector (Motor-Current Detection Circuit)

10, 11: first and second fluid lines

10a, 11a: first and second branch lines

20: power cylinder

21, 22: first and second cylinder chamber

23: rack shaft

23a: rack

24: piston

30: controller

31: steering-assisted torque arithmetic section (steering-assisted torque calculating circuit or steering-assisted torque calculating means)

32: motor control circuit (motor control means)

34: booster circuit control section (booster-circuit control circuit or booster circuit control means)

50: booster circuit

51: motor drive circuit

52: car battery

331: motor angular acceleration detector

[Document 1] Japanese Laid-Open Patent Publication No. 2003-137117

[Document 2] Japanese Laid-Open Patent Publication No. 2003-33077

TECHNICAL FIELD The present invention relates to a power steering apparatus, and more particularly, to a power steering apparatus with a hydraulic power cylinder that enables the application of steering support force by operating the hydraulic power cylinder by means of a motor driven pump.

The power steering device disclosed in Japanese Patent Laid-Open No. 2003-137117 (hereinafter referred to as "JP2003-137117") is generally known as this type of power steering device. The power steering device disclosed in JP2003-137117 has an output shaft connected to the lower end of the steering shaft, a rack-pinion mechanism installed on the lower end of the output shaft for steering the steered wheels, and a rack of the rack-pinion mechanism. With a hydraulic power cylinder and a motor driven reversible pump provided for selectively supplying working fluid into a first cylinder chamber arranged as the left half of the power cylinder or into a second cylinder chamber arranged as the right half of the power cylinder. It is composed. When a normal steering operation is performed by the steering wheel for left turn or right turn while driving a vehicle for the purpose of applying steering assistance, the working fluid (hydraulic pressure or working pressure) is normally rotated or reversed of the motor-driven reversible pump. Rotation is optionally supplied to either one of the first and second hydraulic cylinder chambers. When compared to an electric power steering device in which the steering shaft is directly driven by an actuator (electric motor) for an electric motor of the same size and type, the hydraulic power cylinder mounted power steering device can produce relatively large steering support.

However, with the recent expansion of vehicles with power steering devices, greater steering assistance is required. Therefore, a further increase in the motor power output was required. For further motor power output increases, Japanese Laid-Open Patent Publication No. 2003-33077 (hereinafter referred to as "JP2003-33077") corresponding to US Patent Application No. 6,987,371 is a source of drive power for a motor connected to a steering system. Teach the use of a booster circuit to boost the voltage. JP2003-33077 also teaches a steering controller that controls source voltage boost timing based on the rotational speed of the motor. Motor speed dependent source voltage boost timing control contributes to a reduction in the frequency of execution of the boost operation, thus ensuring a reduced power consumption of the car battery.

However, the hydraulic power cylinder mounted power steering apparatus disclosed in JP2003-137117 is configured such that the working fluid is pressurized by the rotation of the motor driven reversible pump so that the power cylinder is operated by the working fluid pressure generated by the pump. Thus, the power steering device of JP2003-137117 has a motor speed versus working fluid pressure characteristic in which the motor speed is fast until the working fluid pressure reaches a predetermined pressure level and the motor speed decreases after reaching the predetermined pressure level. In the case of the motor speed versus working fluid pressure characteristics described above, the rate of change of the motor speed is very high until the working fluid pressure reaches a predetermined pressure level. While the predetermined pressure level has not yet been reached, it is assumed that the actual rate of change of the motor speed is less than the desired value. Then, the response delay of the working fluid pressure rise occurs while the motor speed threshold value is not yet reached. In such a case, even if the boost operation starts at the boost timing when the motor speed reaches its threshold value, it is impossible to guarantee the predetermined fluid pressure control responsiveness (ie, the predetermined steering assist control responsiveness), and thus It is difficult to quickly and precisely bring the actual working fluid pressure closer to a given value. In addition, the required motor speed change after the start of boost operation depends on the pressure level of the working fluid pressure generated when the motor speed threshold value is reached. Therefore, in the case of a rapid motor speed increase, there is a possibility of insufficient boost operation and / or unnecessary implementation of the boost operation on the source voltage. To avoid this, it is possible to set the motor speed threshold value to a low value at the time when the boost operation is started. However, boost operation can be over-executed due to setting the motor speed threshold value to a low value, thus increasing the frequency of operation of the booster circuit undesirably. This leads to an increase in car battery load.

Therefore, in view of the aforementioned disadvantages of the prior art, it is an object of the present invention to apply steering support to any one of a pair of hydraulic cylinder chambers of a hydraulic power cylinder by selectively supplying working fluid pressure during operation of the motor driven pump. It is to provide a power steering apparatus that can achieve a good steering feeling without increasing the battery load.

In order to achieve the above and other objects of the present invention, the power steering apparatus includes a hydraulic power cylinder configured to support a steering force of a steering mechanism connected to a steered wheel, and hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder. A pump for selectively supplying pressure, a motor for driving the pump, and a power steering control system configured to be electrically connected to at least the motor and the driving power source for controlling the driving state of the motor and the power supply voltage of the driving power source; The power steering control system includes a motor control circuit that generates a motor drive signal whose command signal value is determined based on a steering support force applied to a steering wheel through a power cylinder, and motor angular acceleration that detects or predicts motor angular acceleration. A detection circuit and a booster-circuit control circuit that controls switching between actuation and non-operational states of the booster circuit in response to motor angular acceleration.

According to another aspect of the present invention, the power steering device also includes a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to the steered wheels, and each hydraulic cylinder chamber formed in the power cylinder via first and second fluid lines. A pump having a pair of ports supplied with hydraulic pressure, a motor capable of driving the pump in a normal rotational direction and a reverse rotational direction, a driving power supply for supplying electric power to the motor, a driving state of the motor and a power supply of the driving power supply A power steering control system configured to be electrically connected to at least a motor and a drive power source for controlling the voltage; The power steering control system includes a motor control circuit for generating a motor driving signal whose command signal value is determined based on a steering support force applied to a steering wheel through a power cylinder, and a booster circuit for boosting a power supply voltage of the driving power supply; And a motor angular acceleration detection circuit for detecting or predicting the motor angular acceleration, and a booster-circuit control circuit for controlling the switching between actuating and non-operating states of the booster circuit in response to the motor angular acceleration.

According to another aspect of the invention, the power steering device selectively supplies hydraulic pressure to any one of a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to a steered wheel, and two hydraulic cylinder chambers formed in the power cylinder. A power steering control system configured to be electrically connected to at least a motor and a driving power source for controlling the pump, a motor driving the pump, a driving power supply for supplying power to the motor, and a driving state of the motor and a power supply voltage of the driving power source. It includes; The power steering control system includes a motor control circuit for generating a motor driving signal whose command signal value is determined based on a steering support force applied to a steering wheel through a power cylinder, and a booster circuit for boosting a power supply voltage of the driving power supply; And a motor angular acceleration detecting circuit for detecting or predicting the motor angular acceleration, and a booster-circuit control circuit for switching the booster circuit when the motor angular acceleration becomes equal to or greater than the motor angular acceleration threshold value.

According to another aspect of the invention, the power steering device selectively supplies hydraulic pressure to any one of a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to a steered wheel, and two hydraulic cylinder chambers formed in the power cylinder. A power steering control system configured to be electrically connected to at least a motor and a driving power source for controlling the pump, a motor driving the pump, a driving power supply for supplying power to the motor, and a driving state of the motor and a power supply voltage of the driving power source. The power steering control system includes a torque sensor for detecting steering torque acting on the steering mechanism, a motor control circuit for generating a motor driving signal whose command signal value is determined based on the steering torque, and a driving power supply. The booster circuit boosts the power supply voltage and adjusts as the rate of change of the steering torque over time. A steering torque change rate predicting circuit for calculating or predicting the rate of change of the torque torque, and a booster-circuit control circuit for controlling the switching between actuation and non-operational states of the booster circuit in response to the steering torque change rate.

According to another aspect of the present invention, a power steering apparatus includes a steering shaft fixedly connected to a steering wheel, a hydraulic power cylinder installed in a steering mechanism for connecting the steering shaft to a steering wheel, and two hydraulic cylinder chambers formed in the power cylinder. A pump for selectively supplying hydraulic pressure to any one of the pumps, a motor for driving the pump, a driving power supply for supplying power to the motor, a driving state of the motor and a power supply voltage of the driving power supply, at least the motor and the driving power supply. A power steering control system electrically connected to the power steering system; The power steering control system includes a motor control circuit in which a command signal value generates a motor drive signal determined based on a steering support force applied to a steered wheel through a power cylinder, and the angular displacement of the steering wheel measured from the immediately preceding position. A steering angle sensor for detecting a steering angle corresponding to the steering wheel; a booster circuit for boosting a power supply voltage of a driving power source; a steering wheel angle acceleration calculation circuit for calculating or predicting a steering wheel angle acceleration based on the steering angle; A booster-circuit control circuit which controls the switching between actuation and non-operational states of the booster circuit in response to each acceleration.

According to another aspect of the invention, the power steering device selectively supplies hydraulic pressure to any one of a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to a steered wheel, and two hydraulic cylinder chambers formed in the power cylinder. A power steering control system configured to be electrically connected to at least a motor and a driving power source for controlling the pump, a motor driving the pump, a driving power supply for supplying power to the motor, and a driving state of the motor and a power supply voltage of the driving power source. It includes; The power steering control system includes a motor control circuit for generating a pulse-width modulation (PWM) duty cycle signal of a duty cycle value for the motor, a booster circuit for boosting the power supply voltage of the driving power supply, and a PWM duty cycle signal with respect to time. A PWM duty cycle signal change rate calculating circuit that calculates or predicts a PWM duty cycle signal change rate as a change rate of the duty cycle value of the control circuit, and controls the switching between the operating and non-operating states of the booster circuit in response to the PWM duty cycle signal change rate. A booster-circuit control circuit; The PWM duty cycle signal is determined based on the steering support applied to the steered wheels through the power cylinder.

According to another aspect of the invention, the power steering device selectively supplies hydraulic pressure to any one of a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to a steered wheel, and two hydraulic cylinder chambers formed in the power cylinder. A power steering control system configured to be electrically connected to at least a motor and a driving power source for controlling the pump, a motor driving the pump, a driving power supply for supplying power to the motor, and a driving state of the motor and a power supply voltage of the driving power source. Wherein the power steering control system includes a motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder, and an actual current value flowing across the motor. The motor current detection circuit for detecting the voltage Includes a booster circuit, a current value deviation calculating circuit for calculating a deviation between the command signal value and the actual current value, and a booster-circuit control circuit for switching the booster circuit when the deviation is equal to or higher than the deviation threshold value.

According to another aspect of the invention, the power steering device selectively supplies hydraulic pressure to any one of a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to a steered wheel, and two hydraulic cylinder chambers formed in the power cylinder. A power steering control system configured to be electrically connected to at least a motor and a driving power source for controlling the pump, a motor driving the pump, a driving power supply for supplying power to the motor, and a driving state of the motor and a power supply voltage of the driving power source. It includes; The power steering control system includes a motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to a steering wheel through a power cylinder, a booster circuit for boosting a power supply voltage of a driving power supply; A booster-circuit control circuit for controlling the switching between actuation and non-operational states of the booster circuit; The booster-circuit control circuit switches the booster circuit when it is determined that there is a possibility of delay in response to the hydraulic pressure supplied from the pump to the power cylinder.

Other objects and features of the present invention will be understood from the following description with reference to the accompanying drawings.

First Example

Referring now to the drawings and in particular to FIG. 1, the power steering device of the first embodiment is illustrated in an automobile with left and right steered wheels (not shown). As clearly shown in Fig. 1, the steering wheel a1 is fixedly connected to the top of the steering shaft b1. The upper end of the intermediate shaft b2 is mechanically connected to the lower end of the steering shaft b1 via a universal joint (not shown). The upper end of the pinion shaft b3 is mechanically connected to the lower end of the intermediate shaft b2 via a universal joint (not shown). The torque sensor b4 is a steering wheel a1 and each blood, which substantially corresponds to the magnitude and direction of steering torque (steering wheel torque) applied to the steering wheel a1 about the rotation axis by a driver. It is attached to the pinion shaft b3 to detect the magnitude and direction of the torque acting between the steering wheels. The torque detected by the torque sensor 4b is hereinafter referred to as "steering torque Ts". Pinion b5 is fixedly connected to the lower end of pinion shaft b3. The rack-pinion mechanism c1 consists of the rack 23a and the pinion b5 of the rack shaft 23 (described later). The pinion b5 meshes with the rack 23a of the rack shaft 23, which is the major cross member of the steering linkage. The rack-pinion mechanism c1 serves as a rotational to linear motion converter for converting the rotational movement of the steering wheel a1 into the linear movement of the rack shaft 23. The rack-pinion mechanism c1 also constitutes a part of the steering mechanism connected to the steering wheel.

Both ends of the rack shaft 23 are mechanically connected to each steered wheel (not shown) via tie rods (not shown) and steering knuckles (not shown). The rack shaft 23 is installed in the hydraulic power cylinder 20 in a manner extending in the axial direction of the power cylinder 20. In other words, the power cylinder 20 is installed on the rack-pinion mechanism c1 (steering mechanism). The piston 24 is also located in the power cylinder 20 and is installed at virtually the midpoint of the rack shaft 23 so that the piston 24 is movable with the rack shaft 23. As can be seen from the system diagram of FIG. 1, the inner space of the power cylinder 20 is defined by the first cylinder chamber 21 and the right side of the piston 24 formed on the left side of the piston 24 (see FIG. 1). It is divided into a second cylinder chamber 22 formed on the face. The first cylinder chamber 21 serves to support the axial movement of the rack shaft 3 in the first direction, that is, the right shaft rack movement. On the other hand, the second cylinder chamber 22 serves to support the axial movement of the rack shaft 23 in the second direction, that is, the left shaft shaft movement. That is, the power cylinder 20 supports steering force transmitted through a steering mechanism including a rack-pinion mechanism c1 connected to the steering wheel.

The motor 1 included in the power steering apparatus is a brushless motor capable of rotating in the reverse rotation direction and the normal rotation direction. The motor rotation angle sensor 6 detects the rotation angle θm of the motor rotor of the motor 1, that is, the angular position of the brushless motor rotor, and generates a signal indicating the motor rotation angle θm. To the motor 1 (exactly the rotor of the brushless motor). The motor 1 is operated from a three phase circuit having U phase, V phase and W phase. Three-phase circuits are powered by a voltage that is one third of the cycle out of phase. That is, the motor 1 is connected to a three-phase circuit having U, V, and W phases according to the rotation angle of the motor 1 through a switching circuit (included in the motor driving circuit 51 described later with reference to FIG. 2). It is driven by supplying a voltage. As a rotation angle sensor (or rotation position sensor), that is, a motor rotation angle sensor 6, a resolver, an absolute angle resolver, a plurality of parts spaced apart from each other in a circumferential direction and arranged in a magnetic field of the motor to operate on the Hall effect principle Hall element, rotary encoder and the like can be used. The use of the angular position sensor (motor rotation angle sensor 6) eliminates the need for expensive angular velocity sensors or expensive angular acceleration sensors. The motor shaft, ie the output shaft of the motor 1, is connected to a reversible pump 2 in which the discharge direction of the pressurized working fluid can be reversed or switched according to the rotational direction of the motor shaft. The reversible pump 2 has a first port 2a which serves as an inlet-outlet port and a second port 2b which serves as an inlet-outlet port.

The first port 2a is connected to the first cylinder chamber 21 via the first fluid line 10, while the second port 2b is connected to the second cylinder chamber (through the second fluid line 11). 22). The first branch line 10a is connected to the first fluid line 10. The first branch line 10a is also connected to the reservoir tank 5 via the first check valve 3. In a similar manner, the second branch line 11a is connected to the second fluid line 11. The second branch line 11a is also connected to the reservoir tank 5 via the second check valve 4. The first check valve 3 is arranged in the first branch line 10a to allow only free flow of the working fluid from the reservoir tank 5 to the first fluid line 10. The second check valve 4 is arranged in the second branch line 11a to allow only free flow of the working fluid from the reservoir tank 5 to the second fluid line 11.

As shown in Figs. 1 and 2, the controller (electronic control unit) provided for controlling the motor 1 included in the power steering control system generally includes a microcomputer. The controller 30 includes an input / output interface (I / O), memory (RAM, ROM), and a microprocessor or central processing unit (CPU). The input / output interface (I / O) of the controller 30 includes various engine / vehicle sensors, namely torque sensor b4, motor rotation angle sensor 6, vehicle speed sensor 7 and motor-current detector (motor). -Receive input information from the current detection circuit (8). The vehicle speed sensor 7 refers to a controller that moves at a certain speed and generates a signal indicating the vehicle speed VSP. The motor-current detector 8 is provided to detect the current value Im of the current (motor drive current) applied to the reversible motor 1. Within the controller 30, the central processing unit (CPU) allows access by the I / O interface of the input information data signal from the engine / vehicle sensors b4, 6, 7, 8 discussed previously. The CPU of the controller 30 is responsible for executing the control program stored in the memory, and can perform the arithmetic logic operations necessary for boost control (described later) and motor drive control (described later). The arithmetic result (arithmetic arithmetic result), i.e., the calculated output signal, passes through the booster circuit 50 and / or the motor drive circuit 51 through the output interface circuit of the controller 30 to the output stage, i.e., the motor 1; Is relayed. Details of the booster circuit 50 and the motor drive circuit 51 are described below with reference to the block diagram of FIG.

Referring now to FIG. 2, a processor of the controller 30 is a steering-assisted torque arithmetic that calculates a predetermined steering assist torque (or a predetermined steering assistance amount) based on the vehicle speed sensor 7 and the torque sensor b4. A calculation section (steering-assisted torque calculating circuit or steering-assisting torque calculating means 31). The processor of the controller 30 also obtains the calculated predetermined steering support torque and thus brings the actual steering support torque closer to the predetermined steering support torque, so that the actual motor current detected by the motor-current detector 8 Outputting a control command signal to the motor drive circuit 51 by servo control based on both the value Im and the steering assist torque calculated by the steering-assisted torque arithmetic operation section 31. A motor drive control section, simply a motor control circuit (motor control means) 32. The processor of the controller 30 also detects, determines or predicts the angular acceleration αm of the motor rotor of the motor 1 based on the motor rotation angle indication signal from the motor rotation angle sensor 6. Detector (motor angular acceleration detection circuit 331). In addition, the processor of the controller 30 controls the driving (switching between operating and non-operating states) of the booster circuit 50 based on the motor angular acceleration αm detected by the motor angular acceleration detector 331. A booster circuit control section (booster-circuit control circuit or booster circuit control means) 34.

The booster circuit 50 boosts or raises a power supply voltage (power supply voltage) of a driving power source such as the car battery 52 for the reversible motor 1, and boosts the boost-up battery voltage to the motor driving circuit 51. up battery voltage). As shown in Fig. 2, the booster circuit 50 is configured as a peripheral circuit or an external circuit provided on the outside of the controller. Instead, the booster circuit 50 may be integrated into the controller as an internal circuit.

The motor drive circuit 51 is composed of a switching circuit for supplying electric power to the motor 1 to obtain both a predetermined motor speed and a predetermined motor torque. The switching control is performed to the motor drive circuit 51 by the motor drive control section 32 to control the drive state of the motor 1.

Referring to Fig. 3, there is shown a power steering system control routine performed within the controller 30 included in the power steering apparatus of the first embodiment. The control routine is performed as a time triggered interruption routine that is triggered every predetermined hourly interval, such as 10 milliseconds.

In step 101, steering assistance control processing (or steering assistance torque arithmetic processing) is performed. In parallel with the steering assist control processing of step 101, boost control processing is performed in step 102. Steering assistance control processing (or steering assistance torque arithmetic processing) performed in step 101 includes an arithmetic operation to calculate or determine a predetermined steering assistance torque by the steering-assistance torque arithmetic operation section 31. In the conventional manner, the predetermined steering support torque is suitably calculated or determined such that the driver applied steering torque is closer to the predetermined value. The method of properly calculating a given steering support torque is conventional and does not form any part of the present invention. Therefore, detailed description of the method for calculating the predetermined steering support torque is omitted.

In step 103, motor drive control processing is performed. Motor drive control processing means servo-control processing performed by the motor drive control section 32. Specifically, the predetermined motor drive current value (or the predetermined motor drive signal value) for the motor 1 is calculated by the steering-support torque calculation section 31 in a manner to obtain the predetermined steering support torque. It is set or determined based on the support torque. Then, a control command signal is generated from the motor drive control section 32 to the motor drive circuit 51, so that the actual current value Im of the current flowing through the motor 1 is at a predetermined motor drive current value. You get closer.

In step 104, a check is made to determine if a system shutdown demand for the power steering control system is present or absent. In the absence of a system shutdown request, steps 101, 102, 103 are performed repeatedly. Conversely, when there is a system shutdown request, one cycle of control routine is terminated. For example, when the power steering control system is operating normally, the system shutdown request corresponds to an ignition-switch turned-OFF state. Conversely, if there is a failure of the power steering control system, such as a signal line failure, the processor of the controller 30 determines whether the system shutdown request is satisfied based on the output of the system failure signal.

Referring now to FIG. 4, there is shown a subroutine performed within the motor angular acceleration detector 331 and booster circuit control section 34 included in the power steering apparatus of the first embodiment. The subroutine is performed as a time-induced blocking routine that is triggered every predetermined hourly interval, such as 10 milliseconds.

In step 201, the motor rotation angle [theta] m is read. Specifically, the motor rotation angle θm is determined based on the latest information data from the motor rotation angle sensor 6.

In step 202, the motor angular acceleration [alpha] m is arithmetically calculated based on the motor rotation angle [theta] m. Specifically, the motor angular acceleration αm is calculated arithmetic as the second derivative d ² θ m / dt ² of the motor rotation angle θ m (ie, the second derivative of the angular displacement of the motor rotor of the motor 1). do. More specifically, the motor angular speed ωm is first calculated as the rate of change of the angular displacement of the motor rotor (i.e., the motor rotational angle θm) with respect to the unit time t. In other words, the motor angular speed ωm is expressed as the derivative dθm / dt, which is the rate of change of the motor rotation angle θm with respect to time. Secondly, the motor angular acceleration [alpha] m is calculated as the rate of change (= d [theta] m / dt) of the motor angular velocity [omega] m over time. That is, the motor angular acceleration αm is expressed by the equation αm = dωm / dt = d ² θm / dt ² .

In step 203, whether the source voltage of the drive power source (battery 52) for the motor 1 is boosted and the boost control in which the boost-up battery voltage is supplied to the motor drive circuit 51 is enabled (started). Or to determine whether or not it is disabled (disabled), the absolute value | αm | of the motor angular acceleration αm calculated through steps 201-202 is greater than or equal to the motor angular acceleration threshold value (fixed threshold value, αmf). A check is made to determine the acknowledgment. When the response to step 203 is positive (YES), that is, | αm | <αmf, the routine proceeds from step 203 to step 205. Comparing the absolute value | αm | of the motor angular acceleration αm to its threshold value αmf corresponds to the normal rotation and reverse rotation of the motor 1. The motor angular acceleration threshold value αmf means a threshold value in which the driver applied steering torque tends to increase to exceed a predetermined value due to lack of steering support.

In step 204, boost control is enabled (ON). In other words, the booster circuit 50 is switched on to initiate the boost operation. The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage (fixed voltage value Vdt), that is, Vd = Vdt.

In step 205, the boost control is either disabled (OFF) or left in an impossible state. In other words, the booster circuit 50 is switched off or kept switched off to disable the boost operation. The power supply voltage Ve is output from the booster circuit 50 in the present state, that is, Vd = Ve.

[Basic Power Steering Control Behavior]

The basic control operation performed by the power steering control system will be described in detail below. After the ignition switch is turned on, the drive current (or motor drive signal) determined based on at least the sensor signal (steering torque Ts) from the torque sensor b4 is supplied to the motor 1. The motor 1 generates a torque (motor torque Tm described later) substantially corresponding to the drive current supplied to the motor, and then the pump 2 is driven by the motor 1. The pump 2 thus discharges the pressurized working fluid of the flow rate corresponding to the motor speed.

For example, assuming that pressurized working fluid is discharged from the pump 2 into the first fluid line 10, the pressurized working fluid is introduced into the first cylinder chamber 21 through the first fluid line 10, Thus, a hydraulic pressure increase of the working fluid is caused in the first cylinder. The hydraulic pressure in the first cylinder chamber 21 acts as a steering support torque (steering support force) of driver applied steering wheel torque (driver applied steering force or driver applied steering force). The combined force of the driver-applied steering force and the steering assistance force generated by the hydraulic power cylinder 20 is in a first direction (shown in FIG. 1) with respect to the load resistance generated primarily by friction between each steering wheel and the road surface. This allows the right side movement of the rack shaft 23. In this way, the steered wheels can be steered. During steering assist operation, the piston 24 moves with the rightward displacement of the rack shaft 23 and consequently increases the volume of the first cylinder chamber 21, while the volume of the second cylinder chamber 22 is increased. This decreases. The working fluid discharged by the volume reduction of the second cylinder chamber 22 returns to the second port 2b of the pump 2 via the second fluid line 11. The working fluid returned to the pump 2 is fed back to the first cylinder chamber 21 in which the volume increases. As described above, the power steering apparatus of the first embodiment is configured such that the steering wheel a1 and the motor 1 are connected or coupled to each other via a working fluid. In other words, the steering wheel a1 and the motor 1 are connected or coupled to each other via an integral element (hydraulic power cylinder 20). Since the volume change of each of the first and second cylinder chambers 21, 22 of the power cylinder 20 is obtained by the movement of the working fluid generated by the rotation of the motor 1, the hydraulic power cylinder 20 is It serves as an integral element. Therefore, the predetermined steering support characteristic may be provided while rotating the motor 1 faster than the rotation of the steering wheel a1.

[Basic Motor Characteristics]

5, the basic motor characteristics of the motor 1 are shown. In Fig. 5, the horizontal axis represents the motor torque Tm, the left vertical axis represents the motor speed Nm, and the right vertical axis represents the motor current (actual motor current Im). V _M1 , V _M2 and V _M3 represent three different voltages applied to the motor 1. In Fig. 5, the magnitude relationship of the three voltages V _M1 , V _M2 and V _M3 is inequality V _M1. > V _M2 > V _M3 . As can be seen from the motor characteristics of FIG. 5 associated with three different applied motor voltages V _M1 , V _M2 and V _M3 for any applied voltage value, the motor speed Nm and the motor torque Tm are the counter electromotive force. are in inverse states to each other due to the generation of counter electromotive force. Therefore, under a constant voltage applied to the motor, the motor speed Nm tends to decrease as the motor torque Tm increases. For the same applied voltage, when the motor speed Nm increases inversely, the motor torque Tm tends to fall.

When the motor speed Nm is the speed value N2 under the applied voltage V _M2 , the motor torque Tm becomes the torque value T2, while the motor current Im becomes the current value T2. Under these conditions, when the motor speed Nm increases from the speed value N2 to the speed value N1, the motor current Im tends to decrease from the current value I2 to the current value I1 by the increase in the counter electromotive force, whereas the motor Torque Tm also tends to decrease from torque value T2 to torque value T1. That is, assuming that the motor speed Nm is raised when the steering support force corresponding to the torque value T2 is required, the motor torque Tm cannot be maintained at the torque value T2. In this case, the motor torque Tm tends to fall to a level smaller than the torque value T2. For the reason mentioned above, in order to increase the motor speed while the motor torque Tm remains unchanged (Tm = T2), the motor speed Nm is the speed value N2 and the motor torque Tm is the torque value T2. Under certain conditions, the motor voltage applied to the motor 1 is raised or boosted up from the voltage value V _M2 to the voltage value V _M1 . Even when the counter electromotive force occurs, it is possible to increase the motor current Im from the current value I2 to the current value I1 by the boost-up motor voltage from V _M2 to V _M1 . Therefore, it is possible to raise the motor speed Nm to the speed value N1 while maintaining the motor torque Tm at the torque value T2. When the motor voltage drops from the voltage value V _M2 to the voltage value V _M3 , if the motor speed Nm is kept at the speed value N2, the motor torque Tm will drop to the torque value T1. Even in such a case, it is possible to maintain both the motor speed Nm and the motor torque Tm at the speed value N2 and the torque value T2 by increasing or boosting the motor voltage, in other words, the source voltage (battery voltage). .

[Operation of Power Steering System Components at Different Steering Speeds]

On the basis of the motor characteristics described above, the power steering apparatus of the first embodiment operates at different steering speeds described below with reference to the time charts shown in Figs. 6A to 6F.

Referring now to FIGS. 6A and 6B, the state change of the power steering system component parts of the first embodiment, such as the motor 1 and the reversible pump 2, obtained at high and low speed steering speeds, Is shown. The steering speed is defined as the rate of change of the steering wheel angle, simply steering angle θ (angular displacement of steering wheel a1 measured from the previous position), with respect to time. In the state change of the power steering system component part indicated by the broken line in Figs. 6A to 6D, the power supply voltage Ve boosts the power supply voltage because the steering speed is high and the boost control is not additionally performed. The characteristic obtained under the state which is output from the booster circuit 50 in the state which is not up, ie, Vd = Ve is shown. The state change of the power steering system component parts indicated by solid lines in Figs. 6A to 6F shows that the booster voltage output from the booster circuit 50 due to the high steering speed and further booster control being performed. The characteristic obtained under the state where (Vd) is raised to the boost-up voltage Vdt of predetermined ω, that is, Vd = Vdt is shown. In the state change of the power steering system component parts indicated by dashed-dotted lines in Figs. 6A to 6E, the power supply voltage Ve is the power supply voltage because the steering speed is low and no booster control is additionally performed. Is a characteristic obtained under the state output from the booster circuit 50 without boosting up, that is, Vd = Ve.

When the steering speed of the steering wheel a1 is low or slow, the moving speed of the piston 24 is slow, so that the volume change rate of each of the first and second cylinder chambers 21 and 22 is also slow. The working fluid can be withdrawn from the pump 2 which suitably follows the rate of volume change of each of the first and second cylinder chambers 21, 22. Under these conditions, the development of working fluid pressure is less prone to delay. This suppresses the generation of the highest steering torque, making it possible to generate smooth steering support.

Conversely, when the steering speed of the steering wheel a1 is high or fast, the moving speed of the piston 24 is high, so that the volume change speed of each of the first and second cylinder chambers 21 and 22 is also fast. In this case, there is a possibility that the working fluid discharged from the pump 2 may not properly follow the volume change rate of each of the first and second cylinder chambers 21, 22. Under these conditions, the tendency to delay the generation of working fluid pressure increases. This results in a lack of steering support. Due to insufficient steering support, a large amount of driver applied steering wheel torque is required.

The rotational motion of the motor 1 is determined by the following equation of motion (1). In other words, the angular velocity ωm of the motor 1 can be determined by the following equation (1).

Tm = J × dωm / dt + D × ωm + Tp (1)

Where Tm represents the motor torque, J represents the moment of inertia of the motor 1, D represents the damping coefficient, ωm represents the motor angular velocity, dωm / dt represents the motor angular acceleration αm, and Tp represents the pump ( And pump load torque which tends to increase in proportion to the working fluid pressure generated by the pump 2.

As can be seen from equation (1) discussed above, when a drive current is applied to the motor 1 so that the motor torque Tm starts to increase by the applied drive current, any hydraulic pressure is generated by the motor drive current. Since it is not yet generated by the pump 2 at the same time of application, the motor angular acceleration [d [omega] m / dt (= [alpha] m)] becomes large and the angular velocity [omega m] also becomes large. Thereafter, the pump load torque Tp tends to increase as the hydraulic pressure increases. When the difference (deviation) between the motor torque Tm and the pump load torque Tp becomes small, the motor angular velocity ωm tends to decrease gradually. That is, the motor angular speed ωm (ie motor speed) is determined based on the deviation between the motor torque Tm and the pump load torque Tp.

As shown by the dashed-dotted lines in Figs. 6A to 6E, the increase in the motor drive current is alleviated while the steering speed is low and the boost control is not executed (Fig. 6C). ), Therefore the motor torque Tm rises appropriately. At the same time, the moving speed of the piston 24 is low, so that there is little risk that the hydraulic pressure is generated due to the change in the motor torque Tm. Therefore, the motor angular acceleration [d [omega] m / dt (= [alpha] m)] becomes small, whereby it is possible to appropriately support the driver applied steering torque.

As shown by broken lines in Figs. 6A to 6D, the motor drive current applied to the motor 1 and the motor torque (in the state where the steering speed is high and the boost control is not performed) Tm) rises faster. At the same time, the moving speed of the piston 24 is slow, resulting in a delay in the generation of hydraulic pressure. The deviation between the motor torque Tm and the pump load torque Tp becomes large, the motor angular acceleration [dωm / dt (= αm) becomes large, and further, the peak value (maximum value of the motor angular velocity ωm) is increased. ) Becomes large. Due to the increased motor speed (increased motor angular speed), the counter electromotive force (induction voltage) generated in the induction circuit of the motor 1 also becomes large. Since the polarity of the induced voltage is opposite to the polarity of the applied voltage of the motor 1 at every moment, this results in a shortage of the motor voltage necessary for flowing the drive current across the motor 1. During fast steering, the lack of motor drive current tends to arise from the increase in motor speed (rise of motor angular speed? M). This results in a lack of motor torque Tm, and thus a reduction in motor speed occurs. This leads to a lack of hydraulic pressure generated by the pump 2. As a result, steering support is insufficient.

For the reasons discussed above, when a lack of steering support is about to occur, the power supply voltage Ve is boosted up to a predetermined value Vdt by boost control (see step 204 in FIG. 4), and consequently the motor ( The voltage applied to 1) is proportionally increased in such a way as to compensate for the lack of motor speed (lack of motor angular velocity ωm). In the power steering control system for the power steering apparatus of the first embodiment, the motor angular acceleration [d? M / dt (=? M)] and its threshold value ?? When a comparison result (| αm | ≥αmf or | αm | <αmf) of the latest information data for is used, and the absolute value (| αm |) of the motor angular acceleration αm is equal to or greater than the motor angular acceleration threshold value αmf, The processor of the controller 30 determines whether a lack of steering support will occur. Therefore, as shown by solid lines in Figs. 6A to 6F, the time point t1 when the absolute value | αm | of the motor angular acceleration αm exceeds its threshold value αmf. ), By the power steering control system for the power steering apparatus of the first embodiment, boost control is started (enabled) and power is supplied to the booster circuit 50 (ON), and thus the motor speed (motor angular speed) It is possible to raise (ωm)] to a high value. As a result, the driver applied steering torque becomes small, and it is possible to avoid the response delay of the working fluid pressure control, that is, the deteriorated steering assist control response. As described above, in the power steering control system for the power steering apparatus of the first embodiment, as a measurement when steering assist force is to be generated, a comparison result between the more recent motor angular velocity ω m and its threshold value ω mf is used. Instead, a comparison result (| αm | ≥αmf or | αm | <αmf) of a more recent motor angular acceleration [dωm / dt (= αm) and its threshold value αmf is used. In other words, the boost control is not only performed by the high motor angular velocity? M. Thus, according to the system of the first embodiment, it is possible to effectively suppress the durability degradation of the booster circuit 50 caused by unnecessary boost operation, and also to ensure the reduced power consumption of the battery 52.

In addition, the power supply operation to the motor 1 is stopped during the non-steering operation, and the driving state of the motor 1, that is, the direction of rotation of the motor 1, the motor torque, and the motor speed are adapted to the demand for steering support during steering. In the power steering apparatus of the first embodiment which can be controlled accordingly, it is necessary to raise the motor speed (motor angular velocity ωm) at once from zero motor speed (ωm = 0) to the maximum motor speed value. . When the motor speed must be raised at once, it is very advantageous to be able to detect the demand for motor speed rise based on the motor angular acceleration [d [omega] m / dt (= [alpha] m) at an early time.

2nd Example

Referring now to FIG. 7, a detailed configuration of the control system of the power steering apparatus of the second embodiment is shown. As can be seen from the comparison of the block diagrams shown in Figs. 2 and 7, the configuration of the control system of the power steering apparatus of the second embodiment is basically similar to that of the first embodiment. Thus, the same reference numerals used to designate the elements of the control system of the power steering apparatus of the first embodiment shown in FIG. 2 represent two different embodiments in the corresponding reference numbers used in the second embodiment shown in FIG. Will be applied for comparison. The circuitry indicated by reference numeral 332 will be described in detail below with reference to the accompanying drawings, but the detailed description of reference numerals 1, 6, 7, 8, b4, 31, 32, 50, 51 and 52 will be described above. This seems obvious and is omitted. In the system of the first embodiment, the booster circuit 50 is controlled using the motor angular acceleration [d [omega] m / dt (= [alpha] m)] as a parameter (see motor angular acceleration detector 331 shown in FIG. 2). Conversely, in the second embodiment, the booster circuit 50 is controlled using the steering torque change rate DELTA Ts (exactly, the change rate of the steering torque Ts over time) as a parameter (shown in FIG. 7). See steering torque change rate prediction circuit or steering torque change rate prediction section 332].

As can be seen from the block diagram of Fig. 7, which mainly shows the configuration of the controller 30 included in the control system of the power steering apparatus of the second embodiment, the steering torque change rate predicting section 332 is obtained from the torque sensor b4. Is provided to predict the steering torque change rate DELTA Ts on the basis of the sensor signal (steering torque Ts). Further, a booster circuit control section for controlling the driving (switching between operating and non-operating states) of the booster circuit 50 based on the steering torque change rate ΔTs predicted by the steering torque change rate prediction section 332 ( 34) is provided.

Referring now to FIG. 8, there is shown a subroutine executed within the booster circuit control section 34 and steering torque change rate prediction section 332 of the controller 30 included in the power steering apparatus of the second embodiment.

In step 301, the steering torque Ts is read. Specifically, the steering torque Ts is determined based on the latest information data from the torque sensor b4.

In step 302, the steering torque change rate DELTA Ts is arithmetic calculated and predicted based on the steering torque Ts. Specifically, the steering torque change rate DELTA Ts is calculated as the change rate of the more recent steering torque value Ts _(new) from the previous steering torque value Ts _(old) with respect to the unit time t. That is, the steering torque change rate DELTA Ts is represented by the differential dTs / dt which is the time change rate of the steering torque Ts.

In step 303, the absolute value of the steering torque change rate ΔTs calculated or predicted through steps 301 and 302 to determine whether boost control is enabled (started) or not (released). A check is made to determine if the value | ΔTs | is greater than or equal to the steering torque change rate threshold value Tsf. When the answer to step 303 is YES, ie | ΔTs | ≥Tsf, the routine proceeds from step 303 to step 304. Conversely, when the answer to step 303 is negative (NO), that is | ΔTs | <Tsf, the routine proceeds from step 303 to step 305. Comparing the absolute value | ΔTs | of the steering torque change rate ΔTs to its threshold value Tsf corresponds to the normal rotation and reverse rotation of the motor 1. The steering torque change rate threshold value Tsf means a threshold value that tends to increase the driver applied steering torque to exceed a predetermined value due to lack of steering support.

In step 304, boost control is enabled (ON). The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage Vdt, that is, Vd = Vdt.

In step 305, boost control is either disabled (OFF) or disabled. The power supply voltage Ve is output from the booster circuit 50, that is, Vd = Ve.

The operation and effects obtained by the control flow shown in Fig. 8 executed by the controller 30 included in the power steering apparatus of the second embodiment are described below. Basically, within the steering-assisted torque arithmetic calculation section 31, the predetermined steering assist torque is obtained from the sensor signals (vehicle speed VSP and steering torque Ts) from the vehicle speed sensor 7 and the torque sensor b4. ] Is calculated based on]. At this time, when the input information data signal value for the steering torque change rate DELTA Ts is large, the calculated variation in the predetermined steering support torque becomes large. This means that the motor angular acceleration [dωm / dt (=? M)] also becomes large. As already explained with reference to the system of the first embodiment, when the angular acceleration [d [omega] m / dt (= [alpha] m)] is large, the tendency of the occurrence of the working fluid pressure (hydraulic pressure) is increased. That is, there is a tendency to increase the response delay of the working fluid pressure control, that is, the deteriorated steering assist control responsiveness.

In order to avoid this, by supplying power to the booster circuit 50 under a specific condition where the absolute value | ΔTs | of the steering torque change rate ΔTs is large (that is, | ΔTs | ≧ Tsf), The system can provide the same operation and effect as the first embodiment. In addition, the detection timing (prediction timing) of the steering torque change rate ΔTs predicted based on the steering torque Ts detected by the torque sensor b4 is determined by the motor angular acceleration [d? M / dt (=? M = d ^2). as compared with the detection timing (operation timing) of θm / dt ^2)] and some progress in the phase. That is, it is possible to detect or predict the steering torque change rate DELTA Ts at an earlier stage rather than the motor angular acceleration [dωm / dt (=? M = d ² ? M / dt ² ). In the case of the system of the second embodiment using the steering torque change rate ΔTs instead of using the motor angular acceleration [dωm / dt (= αm = d ² θm / dt ² )], a countermeasure against noise is required, but steering is required. The use of the torque change rate ΔTs is superior to the use of the motor angular acceleration [d? M / dt (=? M = d ² ? M / dt ² )] in steering assist control responsiveness.

The third Example

Referring now to Figures 9 and 10, the system configuration of the power steering apparatus of the third embodiment is shown. As can be seen from the comparison of the system diagrams shown in Figs. 1 and 9, and also from the comparison of the block diagrams of Figs. 2 and 10, the basic configuration of the third embodiment is similar to that of the Fig. 1 embodiment. similar. Accordingly, the same reference numerals used to designate the elements of the power steering apparatus of the first embodiment shown in FIGS. 1 and 2 are used in the third embodiment shown in FIGS. 9 and 10 to compare the two embodiments. Will be applied to corresponding reference numerals. The circuit and steering wheel angle sensor (simply steering angle sensor, b6) indicated by reference numeral 333 will be described in detail with reference to the accompanying drawings below, but the detailed description of other reference numerals appears to be self-explanatory. It is omitted. In the system of the first embodiment, the booster circuit 50 is controlled using the motor angular acceleration [d [omega] m / dt (= [alpha] m)] as a parameter (see motor angular acceleration detector 331 shown in FIG. 2). Conversely, in the third embodiment, the booster circuit 50 is controlled using the ^second derivative d ² θ / dt ² of the steering wheel angle, simply the steering angle θ (angular displacement of the steering wheel a1) as a parameter. (See steering wheel angle acceleration arithmetic circuit or steering wheel angle acceleration arithmetic operation section 333 shown in FIG. 10).

As can be seen from the system diagram of the power steering apparatus of the third embodiment of Fig. 9, the steering wheel angle sensor b6 determines the steering wheel angle θ (angular displacement of the steering wheel a1 measured from the previous position). It is attached to the steering shaft b1 for detection. The other component parts of the power steering apparatus of the third embodiment are the same as the component parts of the first embodiment.

As can be seen from the block diagram of Fig. 10 mainly showing the configuration of the controller 30 included in the control system of the power steering apparatus of the third embodiment, the steering wheel angle acceleration arithmetic operation section 333 is a steering wheel angle sensor. from (b6) is provided for arithmetically calculating or predicting steering wheel angular acceleration vθ (= d ² θ / dt ² ) based on the sensor signal (steering wheel angle θ). Further, the driving of the booster circuit 50 (between operating and non-operating) is based on the steering wheel angular acceleration [vθ (= d ² θ / dt ² )] calculated by the steering wheel angular acceleration arithmetic calculation section 333. A booster circuit control section 34 is provided for controlling the switching).

Referring now to FIG. 11, there is shown a subroutine performed within the booster circuit control section 34 and steering wheel angular acceleration arithmetic operation section 333 of the controller 30 included in the power steering apparatus of the third embodiment.

In step 401, the steering wheel angle θ is read. Specifically, the steering wheel angle θ is determined based on the latest information data signal from the steering wheel angle sensor b6.

In step 402, the steering wheel angular acceleration vθ is calculated arithmetically based on the steering wheel angle θ. Specifically, the steering wheel angular acceleration vθ is calculated as the second derivative d ² θ / dt ² of the steering wheel angle θ (angular displacement of the steering wheel a1 measured from the previous position). More specifically, the steering wheel angular velocity ω is first calculated as the angular displacement of the steering wheel a1 (ie, the rate of change of the steering angle θ) with respect to the unit time t. That is, the steering wheel angular velocity ω is represented by a derivative (dθ / dt) which is the rate of change of the steering wheel angle θ with respect to time. Secondly, the steering wheel angular acceleration vθ is calculated as the rate of change of the steering wheel angular velocity [omega] (= d [theta] / dt) with respect to time. That is, the steering wheel angular acceleration vθ is represented by the equation vθ = dω / dt = d ² θ / dt ² .

In step 403, the absolute value of the steering wheel angular acceleration vθ calculated through steps 401 and 402 to determine whether boost control is enabled (started) or not (disabled) A check is made to determine whether | v [theta] | is equal to or greater than the steering wheel angle acceleration threshold value v [theta] f. When the answer to step 403 is positive (YES), that is, | vθ | If ≧ vθf, the routine proceeds from step 403 to step 404. Conversely, when the answer to step 403 is negative (NO), that is, | vθ | If <vθf, the routine proceeds from step 403 to step 405. Comparing the absolute value | vθ | of the steering wheel angular acceleration vθ with its threshold value vθf corresponds to the normal and reverse rotation of the motor 1. The steering wheel angular acceleration threshold value vθf means a threshold value in which the tendency for the driver applied steering torque to exceed a predetermined value due to lack of steering support increases.

In step 404, boost control is enabled (ON). The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage Vdt, that is, Vd = Vdt.

In step 405, boost control is either disabled (OFF) or disabled. The power supply voltage Ve is output from the actual booster circuit 50, that is, Vd = Ve.

The operation and effects obtained by the control flow shown in Fig. 11 executed by the controller 30 included in the power steering apparatus of the third embodiment are described below. Basically, in the steering-assisted torque arithmetic calculation section 31, the predetermined steering assist torque is obtained from the sensor signals (vehicle speed VSP and steering torque Ts) from the vehicle speed sensor 7 and the torque sensor b4. ] Is calculated based on]. At this time, if the input information data signal value is large for the steering wheel angular acceleration vθ, the calculated variation in the predetermined steering support torque becomes large. This is because the steering torque Ts is substantially proportional to the second derivative d2θ / dt2 of the steering wheel angle θ, that is, the steering wheel angular acceleration vθ. A large predetermined steering support torque means that the motor angular acceleration [d [omega] m / dt (= [alpha] m)] also becomes large. As has already been described with reference to the system of the first embodiment, in the case of a large angular acceleration [d [omega] m / dt (= [alpha] m)], the tendency of the generation of the working fluid pressure (hydraulic pressure) is increased. That is, there is a tendency to increase the response delay of the working fluid pressure control, that is, the deteriorated steering assist control responsiveness.

In order to avoid this, by supplying power to the booster circuit 50 under a specific condition where the absolute value | vθ | of the steering wheel angular acceleration vθ is large (that is, | vθ | ≧ vθf), the system of the third embodiment provides It can provide the same operation and effect as the first system.

4th Example

Referring now to FIG. 12, a detailed configuration of the control system of the power steering apparatus of the fourth embodiment is shown. As can be seen from the comparison of the block diagrams shown in Figs. 2 and 12, the configuration of the control system of the power steering apparatus of the fourth embodiment is basically similar to that of the first embodiment. Accordingly, the same reference numerals used to designate the elements of the control system of the power steering apparatus of the first embodiment shown in FIG. 2 are corresponding reference numerals used in the fourth embodiment shown in FIG. 12 to compare the two embodiments. Will be applied to. The circuitry indicated by reference numeral 334 will be described in detail below with reference to the accompanying drawings, but a detailed description of other reference numerals will be omitted since the above description seems obvious. In the system of the first embodiment, the booster circuit 50 is controlled using the motor angular acceleration [d [omega] m / dt (= [alpha] m)] as a parameter (see motor angular acceleration detector 331 shown in FIG. 2). Conversely, in the fourth embodiment, the booster circuit 50 is a parameter of the duty cycle value Duty of the pulse-width modulation (PWM) signal (PWM duty-cycle signal) applied to the motor 1 with respect to time. Controlled using the change rate ΔDuty (hereinafter referred to as " PWM duty change rate ΔDuty ") (see PWM duty change rate calculating circuit or PWM duty change rate calculating section 334 shown in FIG. 12). . The duty cycle value Duty of the PWM signal corresponds to the motor command current value Imo (that is, a predetermined motor drive current value or motor control command signal value).

As can be seen from the block diagram of FIG. 12 mainly showing the configuration of the controller 30 included in the control system of the power steering apparatus of the fourth embodiment, in the motor drive control section 32, the motor command current value ( Imo) is first calculated or calculated based on the predetermined steering support torque calculated by the steering-assisted torque arithmetic operation section 31. Then, the motor drive control section 32 enters into the switching circuit of the motor drive circuit 51 an actual motor current value Im detected by the motor-current detector 8 and a calculated motor command current value Imo. A PWM signal having a duty cycle value Duty determined based on the deviation therebetween is output. The PWM duty change rate calculating section 334 receives input information regarding the duty cycle value Duty of the PWM signal from the motor drive control section 32 and based on the received PWM cycle value Duty of the PWM signal, Calculate or predict the duty change rate ΔDuty. Further, a booster circuit control section for controlling the driving (switching between operating and non-operating states) of the booster circuit 50 based on the PWM duty change rate ΔDuty calculated by the PWM duty change rate calculating section 334 ( 34) is provided.

Referring now to FIG. 13, there is shown a subroutine executed within the booster circuit control section 34 and the PWM change rate calculation section 334 of the controller 30 included in the power steering apparatus of the fourth embodiment.

In step 501, the duty cycle value Duty of the PWM signal is read. Specifically, the duty cycle value Duty of the PWM signal is determined based on the latest information data signal from the motor drive control section 32.

In step 502, the PWM duty change rate ΔDuty is arithmetic calculated based on the duty cycle value Duty. Specifically, the PWM duty change rate ΔDuty is calculated as the rate of change of the more recent duty cycle value Duty _{( new )} from the previous duty cycle value Duty _(old) for the unit time t. The more recent duty cycle value (Duty _(new) ) is calculated in the current execution cycle, while the previous duty cycle value (Duty _(old) ) is calculated one cycle before. That is, the PWM duty change rate ΔDuty is represented by a derivative dDuty / dt, which is a time change rate of the duty cycle value Duty.

In step 503, the PWM duty change rate ΔDuty calculated through steps 501 and 502 is used to determine whether boost control is enabled (started) or not (disabled). A check is made to determine if it is greater than or equal to the threshold value Pd. When the answer to step 503 is affirmative (YES), ie ΔDuty ≧ Pd, the routine proceeds from step 503 to step 504. Conversely, when the answer to step 503 is negative (NO), that is, ΔDuty <Pd, the routine proceeds from step 503 to step 505.

In step 504, boost control is enabled (ON). The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage Vdt, that is, Vd = Vdt.

In step 505, boost control is either disabled (OFF) or disabled. The power supply voltage Ve is output from the actual booster circuit 50, that is, Vd = Ve.

The operation and effects obtained by the control flow shown in Fig. 13 executed by the controller 30 included in the power steering apparatus of the fourth embodiment are described below. Basically, in the steering-assisted torque arithmetic calculation section 31, the predetermined steering assist torque is obtained from the sensor signals (vehicle speed VSP and steering torque Ts) from the vehicle speed sensor 7 and the torque sensor b4. ] Is calculated based on. Then, in the motor drive control section 32, the motor command current value Imo is calculated based on the predetermined steering support torque calculated by the steering-support torque arithmetic operation section 31. Then, the motor drive control section 32 has a duty cycle value determined on the basis of the deviation between the motor command current value Imo and the actual motor current value Im calculated on the switching circuit of the motor drive circuit 51. Outputs the PWM signal of (Duty). At this time, if the input information data signal value is large with respect to the PWM duty change rate ΔDuty, the duty cycle value of the PWM signal fluctuates in response to the change in the steering torque Ts. / dt (= alpha m)] becomes large. Therefore, as has already been described with reference to the system of the first embodiment, in the case of a large angular acceleration [d [omega] m / dt (= [alpha] m)], the tendency of the occurrence of the working fluid pressure (hydraulic pressure) is increased. That is, there is a tendency to increase the response delay of the working fluid pressure control, that is, the deteriorated steering assist control responsiveness.

In order to avoid this, by supplying power to the booster circuit 50 under certain conditions where the PWM duty change ratio ΔDuty is large (that is, ΔDuty ≥ Pd), the system of the fourth embodiment has the same operation and effect as the first embodiment. Can be provided. In addition, the PWM signal of the calculated duty cycle value Duty is an electrical command signal, and thus it is possible to determine the source-voltage boost timing without any additional sensors.

5th Example

Referring now to FIG. 14, a detailed configuration of the control system of the power steering apparatus of the fifth embodiment is shown. As can be seen from the comparison of the block diagrams shown in Figs. 2 and 14, the configuration of the control system of the power steering apparatus of the fifth embodiment is basically similar to that of the first embodiment. Thus, the same reference numerals used to indicate the elements of the control system of the power steering apparatus of the first embodiment shown in FIG. 2 are corresponding reference numerals used in the fifth embodiment shown in FIG. 14 to compare the two embodiments. Will be applied to. The circuitry indicated by reference numeral 335 will be described in detail below with reference to the accompanying drawings, but a detailed description of other reference numerals will be omitted since the above description seems obvious. In the system of the first embodiment, the booster circuit 50 is controlled using the motor angular acceleration [d [omega] m / dt (= [alpha] m)] as a parameter (see motor angular acceleration detector 331 shown in FIG. 2). Conversely, in the fifth embodiment, the booster circuit 50 is a motor command current calculated by the motor drive control section 32 and the actual motor current value Im detected by the motor-current detector 8 as a parameter. The deviation [Delta] Im between the values Imo is controlled (see the electric-current value deviation calculating circuit or the electric-current value deviation calculating section 335 shown in FIG. 14).

As can be seen from the block diagram of FIG. 14 mainly showing the configuration of the controller 30 included in the control system of the power steering apparatus of the fifth embodiment, in the motor drive control section 32, the motor command current value ( Imo) is first calculated or calculated based on the predetermined steering support torque calculated by the steering-assisted torque arithmetic operation section 31. Then, the motor drive control section 32 determines on the switching circuit of the motor drive circuit 51 based on the deviation ΔIm between the actual motor current value Im and the calculated motor command current value Imo. A PWM signal having a duty cycle value Duty is outputted. The current value deviation calculation section 335 receives input information regarding the motor command current value Imo corresponding to the duty cycle value Duty of the PWM signal applied from the motor driving circuit 51, and calculates the calculated motor command current. The deviation [ΔIm (= Imo−Im)] between the value Imo and the actual motor current value Im is arithmetically calculated. In addition, the booster circuit control section 34 for controlling the driving (switching between operating and non-operating states) of the booster circuit 50 based on the deviation ΔIm calculated by the current value deviation calculating section 335. This is provided. In the control system of the fifth embodiment shown in Fig. 14, within the motor drive control section 32 and the current value deviation calculation section 335, the current value deviation Im is calculated separately. Instead, the deviation? Im calculated in the motor drive control section 32 can be branched.

Referring now to FIG. 15, there is shown a subroutine executed within the booster circuit control section 34 and the current value deviation calculation section 335 of the controller 30 included in the power steering apparatus of the fifth embodiment.

In step 601, the motor command current value Imo is read from the motor drive circuit section 32.

In step 602, the actual current value Im detected by the motor-current detector 8 is read.

In step 603, the deviation [Delta] Im between the motor command current value Imo and the actual current value Im is calculated from the equation [Delta] Im = Imo-Im.

In step 604, the deviation? Im calculated through steps 601 to 603 is the current value deviation threshold value to determine whether boost control is enabled (started) or not (turned off). A check is made to determine if (Imf) or more. When the answer to step 604 is affirmative (YES), that is, ΔIm ≧ Imf, the routine proceeds from step 604 to step 605. Conversely, when the answer to step 604 is negative (NO), that is, ΔIm <Imf, the routine proceeds from step 604 to step 606.

In step 605, boost control is enabled (ON). The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage Vdt, that is, Vd = Vdt.

In step 606, boost control is either disabled (OFF) or disabled. The power supply voltage Ve is output from the actual booster circuit 50, that is, Vd = Ve.

The operation and effects obtained by the control flow shown in Fig. 15 executed by the controller 30 included in the power steering apparatus of the fifth embodiment are described below. Basically, in the steering-assisted torque arithmetic calculation section 31, the predetermined steering assist torque is obtained from the sensor signals (vehicle speed VSP and steering torque Ts) from the vehicle speed sensor 7 and the torque sensor b4. ] Is calculated based on. Then, in the motor drive control section 32, the motor command current value Imo is calculated based on the predetermined steering support torque calculated by the steering-support torque arithmetic operation section 31. The motor drive control section 32 then outputs a motor command current value Imo determined based on the predetermined steering support torque. If the change in the steering torque Ts is large, a motor command current value Imo that is larger than the actual current value Im is output, and thus a deviation ΔIm between the motor command current value Imo and the actual current value Im ) Becomes large. At this time, the driving current of the high current value is supplied to the motor 1 through the motor driving circuit 51 in a manner followed by a large deviation? Im. As a result, the motor angular acceleration [dωm / dt (=? M)] is likely to increase. Therefore, as has already been described with reference to the system of the first embodiment, in the case of a large angular acceleration [d [omega] m / dt (= [alpha] m)], the tendency of the occurrence of the working fluid pressure (hydraulic pressure) is increased. That is, there is a tendency to increase the response delay of the working fluid pressure control, that is, the deteriorated steering assist control responsiveness.

To avoid this, by supplying power to the booster circuit 50 under certain conditions (ie,? Im? Imf) with a large current value deviation? Im, the system of the fifth embodiment has the same operation and effect as the first embodiment. Can be provided.

6th Example

Referring now to FIG. 16, modified somewhat from the subroutine of FIG. 4, executed within the booster circuit control section 34 and motor angular acceleration detector 331 of the controller 30 included in the power steering apparatus of the sixth embodiment. The subroutine is shown. As can be seen from the comparison of the subroutines shown in Figs. 4 and 16, the configuration of the control system of the power steering apparatus of the sixth embodiment is basically similar to that of the first embodiment. In the system of the first embodiment, boost control is made possible under certain conditions in which the absolute value |? M | of the motor angular acceleration [? M (= d? M / dt)] is equal to or greater than one predetermined motor angular acceleration threshold value? Mf. That is, the motor angular acceleration αm is compared with a fixed single motor angular acceleration threshold value αmf. Conversely, the system of the sixth embodiment uses the variable motor angular acceleration threshold value αmfn which varies with the power supply voltage Ve (the pre-programmed power supply voltage Ve versus the motor angular acceleration threshold value shown in Fig. 17). αmfn) property map]. In the variable motor angular acceleration threshold value αmfn, n is a positive integer. That is, a plurality of threshold values αmf1, αmf2, αmf3, ..., αmfn are set in accordance with the voltage level of the power supply voltage Ve. The configuration of the controller 30 included in the control system of the power steering apparatus of the sixth embodiment of Fig. 16 is basically similar to that of the first embodiment. In the system of the sixth embodiment, (i) a signal line to which information data on the voltage level of the power supply voltage Ve can be read is attached to the booster circuit control section 34, and (ii) shown in FIG. The system of the first embodiment differs in that a preprogrammed power supply voltage Ve versus motor angular acceleration threshold value αmfn characteristic map is embedded in the booster circuit control section 34.

In the modified subroutine of FIG. 16 (Sixth Embodiment) similar to that of FIG. 4 (First Embodiment), only two steps 202a and 202b are added. Thus, the same step numbers used to indicate the steps of the subroutine shown in FIG. 4 will apply to the corresponding step numbers used in the modified subroutine shown in FIG. 16 to compare two different blocking subroutines. Steps 202a and 202b will be described in detail below with reference to the accompanying drawings, but steps 201 to 205 will be briefly described.

In step 201, the motor rotation angle [theta] m is read.

In step 202, the motor angular acceleration [alpha] m is arithmetically computed as the second derivative d ^{2 [} theta] m / dt ² of the motor rotation angle [theta] m.

In step 202a, the power supply voltage Ve is read.

In step 202b, the motor angular acceleration threshold value αmf is the power supply voltage read through step 202a from the pre-programmed power supply voltage Ve vs. motor angular acceleration threshold value αmfn characteristic map shown in FIG. It is calculated or retrieved based on the voltage level of Ve.

In step 203, the absolute value of the motor angular acceleration [alpha] m computed through steps 201 and 202 to determine whether boost control is enabled (started) or not (disabled) | A check is made to determine whether alpha m |) is equal to or greater than the map-search motor angular acceleration threshold value alphamf. When the answer to step 203 is YES, that is, | αm | If ≧ αmf, the routine proceeds from step 203 to step 204. Conversely, when the answer to step 203 is negative (NO), that is, | αm | When <αmf, the routine proceeds from step 203 to step 205. Comparing the absolute value | αm | of the motor angular acceleration αm with its threshold value αmf corresponds to the normal rotation and reverse rotation of the motor 1. The motor angular acceleration threshold value αmf means a threshold value in which the driver applied steering torque tends to increase to exceed a predetermined value due to the lack of steering support.

In step 204, boost control is enabled (ON). The booster voltage Vd output from the booster circuit 50 is raised or boosted up to a predetermined boost-up voltage Vdt, that is, Vd = Vdt.

In step 205, the boost control is either disabled (OFF) or left in an impossible state. The power supply voltage Ve is output from the current booster circuit 50, i.e., Vd = Ve.

The basic operation and effects of the system of the sixth embodiment are similar to those of the first embodiment. Therefore, only different operations and effects of the system of the sixth embodiment will be described below.

As can be seen from the Ve-αmfn characteristic map shown in Fig. 17, the voltage level of the power supply voltage Ve is substantially divided into five voltages V _E1 , V _E2 , V _E3 , V _E4 , V _E5 . The voltage level is defined by the inequality V _E1 <V _E2 <V _E3 <V _E4 <V _E5 . The first, second, third, fourth, and fifth motor acceleration threshold values αmf1, αmf2, αmf3, αmf4, and αmf5 are applied to the voltages V _E1 , V _E2 , V _E3 , V _E4 , and V _E5 . Corresponds. When the power supply voltage Ve is low, the boost control should be initiated as soon as possible to ensure the desired motor speed and the desired motor torque. Conversely, when the power supply voltage Ve is high, there is less need for boost control in that case. In other words, by specifying such a state in which boost control is truly substantially required, the frequency of execution of boost control is effectively reduced while fully considering the voltage level of the supply voltage Ve, thus improving the durability of the booster circuit 50. It is possible to let.

7th Example

Referring now to Figures 18 and 19, the system configuration of the power steering apparatus of the seventh embodiment is shown. As can be seen from the comparison of the system diagrams shown in Figs. 1 and 18, and also from the comparison of the block diagrams of Figs. 2 and 19, the basic configuration of the seventh embodiment is similar to that of the Fig. 1 embodiment. similar. Accordingly, the same reference numerals used to indicate the elements of the power steering apparatus of the first embodiment shown in FIGS. 1 and 2 are used in the seventh embodiment shown in FIGS. 18 and 19 to compare the two embodiments. Will be applied to corresponding reference numerals. The circuit denoted by reference numeral 31 'will be described in detail below with reference to the accompanying drawings, but the detailed description of other reference numerals is omitted because the above description seems obvious.

As can be seen from the system diagram of the power steering apparatus of the seventh embodiment of Fig. 18, the steering wheel angle sensor b6 determines the steering wheel angle θ (angular displacement of the steering wheel a1 measured from the previous position). It is attached to the steering shaft b1 for detection. Rotational direction control valves (simply, rotary valves b4 '), such as four-way three-position rotary valves, provide for supply of the working pressure zone generated by the one-way pump 2' to the first and the second and third positional valves. On the pinion shaft b3 for switching from one of the second cylinder chambers 21, 22 to the other. Specifically, the rotary valve b4 'consists of a valve body and a rotor hermetically fixed to the valve body such that the passages in the rotor connect or disconnect with ports in the valve body to provide four flow paths. do. Although not explicitly shown in Fig. 18, the rotary valve b4 'has four ports, that is, a pump port, two outlet ports, and a tank port (drainage port). The pump port of the rotary valve b4 'is connected via a fluid line 2α to the discharge port 2a' of the one-way pump 2 'which allows the working fluid to be discharged in only one direction. The first outlet port of the rotary valve b4 'is connected to the first cylinder chamber 21 via the fluid line 10', while the second outlet port of the rotary valve 21 is the fluid line 11 '. It is connected to the second cylinder chamber 22 through. The tank port (drainage port) of the rotary valve b4 'is connected to the reservoir tank 5. Sensor signals from the engine / vehicle sensors b6, 6, 7, 8 discussed previously control the driving of the booster circuit 50 (switching between operating and non-operating states) and driving the motor 1. It is input to the input interface circuit of the controller 30 to control.

As can be seen from the block diagram of Fig. 19, which mainly shows the configuration of the controller 30 included in the control system of the power steering apparatus of the seventh embodiment, the processor of the controller 30 includes the vehicle speed sensor 7 and the steering. Hydraulic pressure arithmetic operation section for calculating a predetermined hydraulic pressure to be generated or generated by the one-way pump 2 'based on the sensor signals (vehicle speed VSP and steering wheel angle θ) from the wheel angle sensor b6. (Hydraulic pressure calculating circuit or hydraulic pressure calculating means 31 '). The processor of the controller 30 also detects by the motor-current detector 8 in such a way that it obtains the calculated predetermined hydraulic pressure to bring the actual hydraulic pressure from the pump 2 'closer to the predetermined hydraulic pressure. The motor drive circuit 51 sends a control command signal by servo control on the basis of both the actual motor drive current value Im and the predetermined hydraulic pressure pressure calculated by the hydraulic pressure arithmetic operation section 31 '. And a motor drive control section 32 for outputting. The sensor processor of the controller 30 also detects, determines or predicts the motor angular acceleration αm based on the motor rotation angle θm detected by the motor rotation angle sensor 6. It includes. In addition, a booster circuit control section 34 for controlling the driving (switching between operating and non-operating cycles) of the booster circuit 50 based on the motor angular acceleration αm detected by the motor angular acceleration detector 331. This is provided. Within the hydraulic pressure arithmetic operation section 31 ′, the predetermined hydraulic pressure pressure corresponding to the maximum working pressure and substantially corresponding to the driver required steering support is calculated based on the vehicle speed VSP and the steering wheel angle θ. . Specifically, the predetermined hydraulic pressure is calculated based on the variation of the vehicle speed VSP and the steering wheel angle θ. More specifically, under the condition where the vehicle speed VSP is low and the variation of the steering wheel angle θ is large, the predetermined hydraulic pressure is set to a high pressure value. Under a condition where the vehicle speed VSP is low and the variation in the steering wheel angle θ is small, the predetermined hydraulic pressure is set to a low pressure value. Under the condition that the vehicle speed VSP is high speed, the predetermined hydraulic pressure is set at a relatively low pressure as compared with the vehicle moving state at low speed. As described above, in a manner similar to the first embodiment, the power steering apparatus of the seventh embodiment is also configured such that the steering wheel a1 and the motor 1 are connected to each other through a working fluid. In other words, the steering wheel a1 and the motor 1 are connected to each other via an integral element (hydraulic power cylinder 20). Since the volume change of each of the first and second cylinder chambers 21, 22 of the power cylinder 20 is obtained by the movement of the working fluid generated by the rotation of the motor 1, the hydraulic power cylinder 20 is It serves as an integral element. Therefore, the predetermined steering support characteristic may be provided while rotating the motor 1 faster than the rotation of the steering wheel a1.

Under the condition that the vehicle speed VSP is low and the steering wheel angle θ is large, for example during parking or cornering driving, the required hydraulic pressure is generally high and a rapid motor speed increase is required. In this case, edema of the motor drive current occurs due to rapid moto speed rise. This results in a shortage of the motor torque Tm, and thus a drop in motor speed occurs. This leads to a lack of hydraulic pressure generated by the pump. As a result, steering support is insufficient.

In order to avoid this, when a lack of steering support force is about to occur, the power supply voltage Ve is boosted up to a predetermined value Vdt by boost control, and as a result, the voltage applied to the motor 1 is insufficient in motor speed [ [The lack of motor angular velocity [omega] m] is increased proportionally. In the power steering control system for the power steering apparatus of the seventh embodiment, as a measurement when a lack of steering support force is to occur, a comparison result of the latest information data with respect to the motor angular acceleration αm and its threshold value αmf ( When | αm | ≥αmf or | αm | <αmf are used, and when the absolute value | αm | of the motor angular acceleration αm is equal to or greater than the motor angular acceleration threshold value αmf, the processor of the controller 30 is capable of steering assistance. Determine if lack of power is likely to occur. By the power steering control system for the power steering apparatus of the seventh embodiment, the booster control function is started (enabled), and the absolute value | αm | of the motor angular acceleration αm is the threshold value αmf. When is exceeded, power is immediately supplied to the booster circuit 50 (ON), and thus it is possible to raise the motor speed (motor angular speed? M) in a timely manner to a higher value. As a result, the driver applied steering torque becomes small, and it is possible to avoid the response delay of the working fluid pressure control, that is, the deteriorated steering assist control response. In the seventh embodiment shown in Figs. 18 and 19, as the parameter used to determine the source voltage boost timing, the motor angular acceleration [alpha] m detected by the motor angular acceleration 331 is used. Instead, the system of the seventh embodiment has a steering torque change rate DELTA Ts predicted by the steering torque change rate prediction section 332, a steering wheel angle acceleration vθ calculated by the steering wheel angle acceleration arithmetic operation section 333. ), The PWM duty change rate ΔDuty calculated by the PWM duty change rate calculation section 334, or the current value deviation [ΔIm (= Imo-Im)] calculated by the current value deviation calculation section 335 is used. It may be.

Each of the systems shown in embodiments implements boost control under certain conditions (VSP ≧ VSPf) where the vehicle speed VSP is above a predetermined speed valve VSPf that does not require a large amount of steering support torque (steering support force). And a vehicle speed dependent boost control suppression section (vehicle speed dependent boost control suppression circuit or vehicle speed dependent boost control suppression means) for suppressing. Basically, during high speed driving such as highway driving, there is a possibility that the vehicle dynamic behavior (vehicle stability) due to the quick steering support decreases. Conversely, during vehicle movement at low speeds such as cornering or parking, relatively large steering assistance is required to provide good driving. Thus, it is possible to improve vehicle stability by suppressing boost operation under certain conditions defined as VSP ≧ VSPf, such as during cornering or parking at low speed. By executing the boost operation only during the low speed movement, it is possible to suppress unnecessary operation.

In each of the illustrated embodiments, by the booster circuit control section 34, the booster voltage Vd output by the booster circuit 50 is a predetermined boost-up which is a fixed voltage value at the power supply voltage Ve. It rises to the voltage Vdt. Instead, the predetermined boost-up voltage Vdt is determined by a vehicle such as the steering state of the steering wheel a1, the vehicle speed VSP, the motor angular acceleration αm and / or the duty cycle value Duty of the PWM signal. It can be set variable stepwise (in two or more steps) or steplessly based on the movement state. That is, the predetermined boost-up voltage Vdt is determined by the steering state of the steering wheel a1 (for example, the steering wheel angle θ, the steering wheel angular velocity ω and / or the steering wheel angular acceleration vθ = dω / dt = d). ² θ / dt ² )], vehicle speed (VSP), motor angular acceleration (αm) and / or duty cycle value (Duty) of the PWM signal based on the state of movement of the vehicle Can be determined or set. Therefore, it is possible to set the predetermined boost-up voltage Vdt more precisely, and thereby it is possible to effectively suppress the power consumption of the battery 52.

In the illustrated embodiments, the parameter used to determine if boost control should be initiated, that is, the measurement (or reference) when a lack of steering support force is to occur, the motor angular acceleration αm, the steering torque change rate ( ΔTs, steering wheel angular acceleration (vθ), PWM duty change rate (ΔDuty), and current value deviation (ΔIm) between the calculated motor command current value (Imo) and actual motor current value (Im) One is used. Alternatively, a combination of these parameters αm, ΔTs, vθ, ΔDuty and ΔIm may be used. In addition, in order to suppress unnecessary boost operation more precisely, the vehicle speed VSP can be further considered as a combined parameter. In this case, when the combined parameter exceeds its threshold value, the system is configured to connect (enable) the boost control function.

The basic concept of the power steering apparatus of the illustrated embodiments is summarized below in contrast to the prior art.

(1) Due to the basic motor characteristics, the motor torque Tm becomes insufficient due to the generation of counter electromotive force as the motor speed Nm increases.

(2) In the conventional apparatus, when the motor speed Nm becomes equal to or more than a predetermined threshold value, the motor torque Tm is obtained by boosting or raising the power supply voltage (battery voltage).

(3) However, in the case of a hydraulic power cylinder-mounted power steering device that generates steering assistance through the working fluid pressure generated by the motor driven pump, the boost operation is insufficient when the motor speed becomes above a predetermined threshold value. Although disclosed to compensate for motor torque, a response delay of working fluid pressure rise occurs.

(4) In other words, the power cylinder serves as an integral element in which the rotation of the steering wheel a1 and the rotation of the motor 1 are connected to each other.

(5) This means that the motor speed Nm is the response of the integral element (e.g., power cylinder) in order to produce a motor speed Nm and a motor torque Tm corresponding to the desired working fluid pressure required for the power cylinder. This means that it must be raised at a time up to a speed value higher than the variation of the steering wheel angle θ in a manner to compensate for the delay.

(6) The response delay of the integral element is remarkable in certain conditions where the steering wheel angular velocity ω is fast and the deviation between the actual working fluid pressure and the predetermined fluid pressure is large.

(7) For the reasons discussed above, the improved systems of the illustrated embodiments provide an integrated element (e.g., by initiating a boost control in a timely manner when it is expected that the deviation between the actual steering assistance and the predetermined steering assistance will become large. Compensation of the response delay of the power cylinder).

As can be seen from the first and seventh embodiments, when the booster circuit control section 34 included in the power steering control system determines that there is a possibility of a response delay of the hydraulic pressure supplied from the pump to the power cylinder, Operate to switch booster circuit 50.

The parameters used to predict the response delay of the integral element (eg, power cylinder) may be appropriately selected from the parameters used to calculate the predetermined steering support torque, such as vehicle speed VSP and steering torque Ts. And appropriately derived from the calculation result of the predetermined steering support torque. In other words, assuming that the steering wheel side is defined as the upstream side of the steering control system and the steering wheel side is defined as the downstream side, αm (corresponding to the second derivative (d ² θm / dt ² ) of the motor rotation angle θm) , ΔTs (corresponding to derivative (dTs / dt) of steering torque Ts), vθ (corresponding to second derivative (d ² θ / dt ² ) of steering wheel angle θ), ΔDuty [PWM duty cycle signal Detection upstream of the power cylinder included in the steering control system, such as the derivative of the value Duty (corresponding to dDuty / dt), and the parameter of ΔIm (substantially corresponding to the ratio of the actual motor current value Im). By differentiating the at least one parameter, it is possible to set or determine the source voltage boost timing appropriately and accurately.

The entire contents of Japanese Patent Application No. 2005-239335 (filed August 22, 2005) are incorporated herein by reference.

While the foregoing is a description of preferred embodiments for carrying out the invention, the invention is not limited to the specific embodiments shown and described herein, and various changes and modifications are defined in the scope or spirit of the invention as defined by the following claims. It will be appreciated that it can be done without departing from.

The present invention compensates for the response delay of an integral element (eg, a power cylinder) by initiating timely boost control when it is predicted that the deviation between the actual steering assistance and a given steering assistance will be large.

Claims (26)

A hydraulic power cylinder configured to support the steering force of the steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and A power steering device comprising a drive power supply for supplying power and a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the drive state of the motor and the power supply voltage of the drive power source, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; A booster circuit for boosting a power supply voltage of a driving power supply; A motor angle acceleration detection circuit for detecting or predicting motor angle acceleration, A power steering device comprising a booster-circuit control circuit that controls the switching between actuation and non-operational states of the booster circuit in response to motor angular acceleration. The vehicle speed sensor of claim 1, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. The power supply of claim 1, wherein the booster-circuit control circuit is configured to variably set a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on a moving state of the vehicle. Steering device. The motor of claim 1, wherein the motor comprises a brushless motor having an angular position sensor for detecting an angular position of the brushless motor rotor, And a motor angular acceleration detection circuit predicts motor angular acceleration based on sensor signals from each position sensor. A pump having a hydraulic power cylinder configured to support the steering force of a steering mechanism connected to the steered wheel and a pair of ports through which the hydraulic pressure is supplied through the first and second fluid lines to respective hydraulic cylinder chambers formed in the power cylinder. A motor capable of driving the pump in the normal and reverse rotation directions, a drive power supply for supplying power to the motor, and at least a motor and a power supply for controlling the drive state of the motor and the power supply voltage of the drive power supply. A power steering device comprising a power steering control system configured to be connected to The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; A booster circuit for boosting a power supply voltage of a driving power supply; A motor angle acceleration detection circuit for detecting or predicting motor angle acceleration, A power steering device comprising a booster-circuit control circuit that controls the switching between actuation and non-operational states of the booster circuit in response to motor angular acceleration. The vehicle speed sensor of claim 5, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. The power supply of claim 5, wherein the booster-circuit control circuit is configured to variably set a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on a moving state of the vehicle. Steering device. 6. The motor of claim 5, wherein the motor comprises a brushless motor having an angle sensor for detecting each position of the brushless motor rotor, And a motor angular acceleration detection circuit predicts motor angular acceleration based on sensor signals from each position sensor. A hydraulic power cylinder configured to support the steering force of the steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and A power steering device including a driving power supply for supplying power and a power steering control system configured to be electrically connected to at least the motor and the driving power source for controlling the driving state of the motor and the power supply voltage of the driving power supply, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; A booster circuit for boosting a power supply voltage of a driving power supply; A motor angle acceleration detection circuit for detecting or predicting motor angle acceleration, And a booster-circuit control circuit for switching the booster circuit when the motor angular acceleration is equal to or greater than the motor-angle-acceleration threshold. The vehicle speed sensor of claim 9, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. The power supply according to claim 9, wherein the booster-circuit control circuit variably sets a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage based on a moving state of the vehicle. Steering device. 10. The motor of claim 9, wherein the motor comprises a brushless motor having an angular position sensor for detecting an angular position of the brushless motor rotor, And a motor angular acceleration detection circuit predicts motor angular acceleration based on sensor signals from each position sensor. 10. The apparatus of claim 9, further comprising a power supply-voltage detection circuit for detecting a power supply voltage of the drive power supply, The booster-circuit control circuit compensates for the motor-angle-acceleration threshold in such a manner as to lower the motor-angle-acceleration threshold as the power supply voltage detected by the power-voltage detection circuit decreases. A hydraulic power cylinder configured to support the steering force of the steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and A power steering device comprising a drive power supply for supplying power and a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the drive state of the motor and the power supply voltage of the drive power source, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on the steering torque; A booster circuit for boosting a power supply voltage of a driving power supply; A steering torque change rate predicting circuit for calculating or predicting a steering torque change rate as a change rate of steering torque with respect to time; And a booster-circuit control circuit for controlling the switching between actuation and non-operational states of the booster circuit in response to the rate of steering torque change. The vehicle speed sensor of claim 14, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. The power supply according to claim 14, wherein the booster-circuit control circuit variably sets a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on the moving state of the vehicle. Steering device. A pump for selectively supplying hydraulic pressure to any one of a steering shaft fixedly connected to the steering wheel, a hydraulic power cylinder installed in a steering mechanism connecting the steering shaft to the steered wheel, and two hydraulic cylinder chambers formed in the power cylinder; And a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the motor driving the pump, the drive power source for supplying power to the motor, and the drive state of the motor and the power supply voltage of the drive source. Power steering, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; A steering angle sensor for detecting a steering angle corresponding to the angular displacement of the steering wheel measured from the immediately preceding position; A booster circuit for boosting a power supply voltage of a driving power supply; A steering wheel angular acceleration calculation circuit for calculating or predicting steering wheel angular acceleration based on the steering angle, A power steering device comprising a booster-circuit control circuit that controls switching between actuation and non-operation of the booster circuit in response to steering wheel angular acceleration. 18. The vehicle speed sensor of claim 17, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. 18. The power supply of claim 17, wherein the booster-circuit control circuit variably sets a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on a moving state of the vehicle. Steering device. A hydraulic power cylinder configured to support a steering force of a steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and a motor. A power steering device including a drive power supply for supplying power to the power supply and a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the driving state of the motor and the power supply voltage of the drive power source, The power steering control system, A motor control circuit for generating a pulse-width modulated (PWM) duty-cycle signal of duty cycle value for the motor, wherein the PWM duty-cycle signal is determined based on the steering support applied to the steered wheel through the power cylinder; , A booster circuit for boosting a power supply voltage of a driving power supply; A PWM duty-cycle signal change rate calculating circuit for calculating or predicting the PWM duty-cycle signal change rate as a rate of change of the duty cycle value of the PWM duty-cycle signal with respect to time; A power steering device comprising a booster-circuit control circuit that controls switching between actuation and non-operational states of the booster circuit in response to a PWM duty-cycle signal rate of change. 21. The vehicle speed sensor of claim 20, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. The power supply according to claim 20, wherein the booster-circuit control circuit variably sets a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on a moving state of the vehicle. Steering device. A hydraulic power cylinder configured to support the steering force of the steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and A power steering device comprising a drive power supply for supplying power and a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the drive state of the motor and the power supply voltage of the drive power source, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; Motor-current detection circuitry for detecting the actual current value flowing across the motor; A booster circuit for boosting a power supply voltage of a driving power supply; A current value deviation calculation circuit for calculating a deviation between the command signal value and the actual current value; And a booster circuit control circuit for switching a booster circuit when the deviation is equal to or greater than the deviation threshold value. 24. The vehicle speed sensor of claim 23, further comprising: a vehicle speed sensor for detecting a vehicle speed; And a vehicle-speed dependent boost control suppression circuit for suppressing a boost operation of the booster circuit when the vehicle speed is equal to or greater than a predetermined speed value. 24. The power supply of claim 23, wherein the booster-circuit control circuit is configured to variably set a predetermined boost-up voltage at which the booster voltage output from the booster circuit is boosted from the power supply voltage, based on a moving state of the vehicle. Steering device. A hydraulic power cylinder configured to support the steering force of the steering mechanism connected to the steered wheel, a pump for selectively supplying hydraulic pressure to any one of two hydraulic cylinder chambers formed in the power cylinder, a motor driving the pump, and A power steering device comprising a drive power supply for supplying power and a power steering control system configured to be electrically connected to at least the motor and the drive power source for controlling the drive state of the motor and the power supply voltage of the drive power source, The power steering control system, A motor control circuit for generating a motor drive signal whose command signal value is determined based on a steering support force applied to the steered wheel through the power cylinder; A booster circuit for boosting a power supply voltage of a driving power supply; Power steering including a booster-circuit control circuit that controls the switching between the operating and non-operating states of the booster circuit and switches the booster circuit when it is determined that there is a possibility of delay in response of the hydraulic pressure supplied from the pump to the power cylinder. Device.

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