JP2524450Y2 - Motor-driven power steering device - Google Patents

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a motor-driven power steering device that increases the steering force according to the steering torque, and in particular, to provide a fail-safe function when the steering torque detection sensor fails. The present invention relates to a power steering device having the same.

(Conventional technology and its problems) A steering torque detection sensor (hereinafter referred to as "torque sensor") for detecting a steering torque is provided on a steering shaft or the like, and according to the steering torque detected by the torque sensor,
Control the drive current of the motor that drives the steering system,
Therefore, a motor-driven power steering device that increases the steering force is known.

In such a power steering device, it is assumed that a signal for operating the motor is erroneously output due to a failure of the steering torque detection system such as disconnection or short circuit of the torque sensor or an amplifier that amplifies a detection output signal from the torque sensor. Is done. In such a case, since the driver operates the steering wheel (the steering wheel), there is no hindrance except that an extra steering force is applied. It is required that the steering device be provided with a fail-safe function in the event of a failure of the torque sensor.

The present invention has been made in view of such a demand, and has a motor-driven power steering device that has a fail-safe function in the event of a torque sensor failure and that can secure stable traveling without any trouble even when the torque sensor fails. The purpose is to provide.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, a sensor for detecting a steering torque of a steering system is provided, and the steering system is controlled according to the steering torque detected by the sensor. In a motor-driven power steering apparatus for increasing a steering force by controlling a drive current of a motor to be driven, the sensors have substantially the same characteristics as each other, and each of the sensors detects a steering torque at the same point in a steering system. In order to reduce the steering force by the motor, when a deviation of the steering torque value detected by these sensors is equal to or greater than a predetermined value, the motor is constituted by a plurality of sensors integrally attached to each other via a common support member. A prohibition means for prohibiting boosting is provided.

(Operation) The plurality of sensors of the present invention have substantially the same characteristics as each other, and are integrally attached to each other via a common support member. This makes it possible to avoid erroneous failure determination as much as possible. When the deviation of the steering torque detection values of the plurality of sensors for detecting the steering torque is equal to or greater than a predetermined value, it is determined that one of the sensors is out of order, and the motor does not increase the steering force. As a result, the power steering device does not increase the steering force excessively, and the steering is performed only by the manual operation of the steering wheel, and it is possible to ensure stable running during running, particularly during high-speed running.

(Embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

First, a schematic configuration of a motor-driven power steering apparatus according to the present invention will be described with reference to FIG. 4 and FIG.

In FIG. 4, reference numeral 1 denotes a steering wheel fixed to a steering shaft 2. The steering shaft 2 is connected to a rack and pinion portion 5 of a steering gear 4 via two universal joints 3. The steering gear 4 includes a key box 7 for accommodating a shaft 8 (see FIG. 5), a pinion (not shown), and a rack (not shown) engraved on the left end of the shaft 8 in the figure. Rack and pinion portion 5, a worm screw portion 8a formed at the right end of the shaft 8 in the drawing, and a number of balls 6a.
Ball screw 6b that fits into the worm thread 8a via
And a ball screw portion 6 comprising:

Tie rods 9, 9 are connected to both ends of the shaft 8 via ball joints (not shown).
Are connected to knuckle arms 11, 11 fixed to left and right steering wheels 10, 10, respectively. Then, the steering angle is given to the left and right steering wheels 10, 10 by the movement of the shaft 8 in the left-right direction.

The ball screw portion 6 constitutes a part of a power steering device. The power steering device further drives the shaft 8 to increase a steering force,
Reduction gear device 13 for reducing the rotation of the motor, an electromagnetic clutch device 15 interposed between the reduction gear device 13 and the motor 14,
And an electronic control unit for controlling the operation of the electromagnetic clutch device 15
The ball screw section 6, the reduction gear device
13 and the electromagnetic clutch device 15 are integrally accommodated in a casing 18.

The ball screw 6b of the ball screw portion 6 is formed into a cylindrical shape, and a ball groove 6f having a substantially semicircular cross-section substantially encircling the inner peripheral wall is engraved at a substantially central position in the axial direction of the inner peripheral wall, Both ends of the ball groove 6f are provided with holes (not shown) formed in the side wall of the ball screw 6b at the both end positions and a ball tube 6g attached to the outer peripheral wall of the ball screw 6b.
, The space defined by the ball tube 6g and the worm screw portion 8a and the ball groove 6f is filled with the large number of balls 6a. A driven gear 13a is formed integrally with the ball screw 6b on the outer peripheral wall near the right end in the figure of the ball screw 6b. And ball screw
6b is housed in a bore 6d of a casing 18 having a cylindrical shape and having a shaft 8 penetrating along a central axis, and both ends thereof are rotatably supported by ball bearings 6e.

The motor 14 has its drive shaft 14a parallel to the shaft 8,
In addition, the drive shaft 14a is
And is attached to the side wall of the casing 18 on the rack pinion portion 5 side. The motor 14 is electrically connected to an electronic control unit 16 described later, and the electronic control unit 16
Supplies driving power.

The electromagnetic clutch device 15 housed in the clutch housing space 15a of the casing 18 includes a field coil 15b fixed to a side wall on the casing mounting surface side of the motor 14 concentrically with the drive shaft 14a of the motor 14, A friction plate (armature) 15d opposed to the shaft 15c and spline-coupled to the shaft 13c 'so as to be rotatable integrally with the shaft 13c' of the drive gear 13c described later and to be movable in the axial direction; And a rotor 15c having a disk surface that is fixed to a drive shaft 14a of the motor 14, rotates integrally with the drive shaft 14a, and is engageable with the friction plate 15d.
The field coil 15b is electrically connected to the electronic control unit 16, and when energizing power is supplied from the electronic control unit 16, the field coil 15b displaces the friction plate 15d toward the rotor 15c and frictionally engages the same. The rotation of the motor 14 can be transmitted to the shaft 7 via the reduction gear device 13 and the ball screw 6b.

A drive gear 13c of the reduction gear unit 13 meshes with a driven gear 13a formed on the ball screw 6b via an idle gear 13b, and these gear trains reduce the rotation of the motor 14 and transmit the rotation to the shaft 8. I do.

The motor 14 is capable of normal rotation and reverse rotation, and when the motor 14 rotates forward or backward, the rotational force of the motor 14 is transmitted to the ball screw 6b via the reduction gear, and the shaft is driven according to the forward or reverse rotation of the motor 14. 8 moves by being pressed left and right, thereby increasing the steering force.

Next, the configuration of the electronic control unit 16 will be described with reference to FIGS. 1 to 3 and FIG.

The electronic control unit 16 includes a control circuit 30, a motor drive circuit 40, a clutch drive circuit 50, a disconnection detection circuit 55 for detecting an abnormality such as a disconnection of a vehicle speed sensor, a comparison circuit 56 for detecting an abnormality of a torque sensor, and the like. A first torque sensor 20 and a vehicle speed sensor 22 are connected to an input side of the circuit 30, and an output side of the motor drive circuit 40, one input terminal of the AND circuit 59, and an abnormal state of the first torque sensor 20 and the like. Alarm lights 52 for issuing alarms are respectively connected, and the output side of the AND circuit 59 is connected to the clutch drive circuit 50. The motor 14 is connected to the output side of the motor drive circuit 40, and the electromagnetic clutch device 15 is connected to the output side of the clutch drive circuit 50, respectively. The vehicle speed sensor 22 is also connected to a disconnection detection circuit 55, and the output side of the disconnection detection circuit 55 is connected to one input terminal of an OR circuit 57. The input side of the comparison circuit 56 is connected to the first torque sensor 20 and the second torque sensor 21.
The output side of the comparison circuit 56 is the other input terminal of the OR circuit 57,
And the other input terminal of the AND circuit 59 via an inverter 58, and the OR circuit 57 is connected to the input side of the control circuit 20. Note that the comparison circuit 56 and the inverter
The 58 and the AND circuit 59 constitute a prohibition unit that prohibits the motor from increasing the steering force when the failure of the torque sensors 20 and 21 is detected.

For the first and second torque sensors 20 and 21, for example, Hall ICs are used. More specifically, as shown in FIGS. 6 (a) and 6 (b), a small diameter constricted portion 2a is provided on the steering shaft 2, and support members 2b and 2c are fixed to the shaft 2 with the constricted portion 2a interposed therebetween. The support member 2b has 2
Permanent magnets 20a and 21a have two holes I in the support member 2c.
C20b, 21b are mounted respectively, and each permanent magnet 20a, 21b
“a” is opposed to the corresponding Hall ICs 20b and 21b, and is arranged at a predetermined distance. The permanent magnet 20a and the Hall IC 20b constitute a first torque sensor 20, and the permanent magnet 21a and the Hall IC 21b constitute a first torque sensor.
Make up 21. The first and second torque sensors 20 and 21 have substantially the same characteristics, and the shaft 2 (the constricted portion 2a)
Is constant, the torsion torque, that is, the steering torque and the torsion angle, that is, the relative displacement between each magnet 20a (21a) and the Hall IC 20b (21b) is in a proportional relationship, and therefore, the Hall IC 20b and Each of 21b outputs a voltage signal proportional to the steering torque as shown in FIG. 7, and the output signal is supplied to the control circuit 30 and / or the comparison circuit 56 via the slip ring 19. On the other hand, the vehicle speed sensor 22 is, for example, a magnet 22 that rotates corresponding to the rotation of the output shaft of the engine.
a and a reed switch 22b that turns on and off in synchronization with the rotation of the magnet 22a (see FIG. 2).

FIG. 2 shows the internal configuration of the control circuit 30 and the motor drive circuit 40. First, the motor drive circuit 40 is a known changeover switch circuit composed of four transistors TR1 to TR4. When the energizing signal is input from the PWM circuit 32 to the bases of the transistors TR1 and TR4, the direction indicated by the broken line in FIG.
From the transistor TR4 via the motor 14, the motor 14 rotates clockwise (forward),
When the energizing signal is input to the bases of the transistors TR2 and TR3, a current flows in the direction indicated by the solid line in FIG. 2, that is, in the direction from the transistor TR3 to the transistor TR2 via the motor 14, and the motor 14 rotates counterclockwise. (Reverse rotation) direction. Then, the motor 14 generates a driving torque according to the supplied current value. The current value supplied to the motor 14 is detected and fed back to the PWM circuit 32 via the amplifier 36 of the control circuit 30. The diodes D1 to D4 of the switch circuit prevent the transistor from being damaged by the back electromotive force when the current is turned off.

Next, in the control circuit 30, the output signal of the first torque sensor 20 is amplified by the preamplifier 31, and then sent to the PWM circuit 32. On the other hand, the vehicle speed signal from the vehicle speed sensor 22 is a known signal.
The signal is converted into a voltage signal by an F / V conversion circuit 33, and a vehicle speed determination circuit 34
Supplied to The vehicle speed determination circuit 34 compares the supplied voltage signal with a predetermined reference voltage, and determines that the vehicle speed is a predetermined speed (for example,
15 km / h), and outputs a high-level (H) signal when the vehicle speed exceeds the predetermined speed. The output side of the vehicle speed determination circuit 34 is connected to one input terminal of the NOR circuit 35, and the other input terminal of the NOR circuit 35 is connected to the output side of the OR circuit 57 in FIG. The output side of the NOR circuit 35 is connected to the input side of the PWM circuit 32, the one input terminal of the AND circuit 59 in FIG.
52 are connected to each other. The NOR circuit 35 outputs a high-level (H) signal unless a high-level (H) signal is input to either of the two input terminals, and the high-level (H) signal is input to one of the input terminals. For example, the output is inverted to a low level (L) signal. Therefore, NO
The R circuit 35 determines that the vehicle speed is the predetermined speed (1
5 km / h), or when an abnormality such as a first torque sensor 20 described later is detected.
A low level (L) signal is supplied to the M circuit 32, the AND circuit 59, and the inverter 38. When a low level (L) signal is supplied to the inverter 38, the inverter 38 outputs a high level (H) signal to turn on the alarm lamp 52, and that the electromagnetic clutch device 15 described later is in a disengaged state, or An alarm is issued for a failure of the first torque sensor 20 or the like.

When a high level (H) signal is supplied from the NOR circuit 35, that is, when the vehicle speed is equal to the predetermined speed (15 km /
h) If the above is not the case and there is no abnormality in the first torque sensor 20 or the like, the supply current of the motor 14 is controlled as follows according to the output signal from the first torque sensor 20.

First, the PWM circuit 32 determines the supply current value I to the motor 14 according to the steering torque based on the output signal from the first torque sensor 20. More specifically, as shown in FIG. 8, the supply current value I is such that the steering torque value is within a predetermined minute value range (−tq
₀ to + tq ₀ ), the value is set to 0, so that even if a slight steering torque is generated, it is not sensitive to the steering torque, thereby stabilizing the control. When the steering torque value is in the range of + tq ₀ to + tq ₁ , the steering torque value is set to a value that increases in proportion to the increase of the steering torque value, and when the steering torque value exceeds the value + tq ₁ , the value is set to a constant value (+ I ₁ ) In the latter case, the steering force is prevented from increasing excessively. Similarly, the value decreases in proportion to the decrease in the steering torque when the steering torque value is within the range of -tq ₀ ~-tq _2, a constant value and the steering torque value is below the value -tq ₂ (-I ₂ ) are set respectively. And PW
The M circuit 32 determines which of the pair of transistors TR1 and TR4 and the pair of transistors TR2 and TR3 the energizing signal is to be supplied in accordance with the determined current value I, and also determines the pulse width of the energizing signal. When a predetermined transistor among the transistors TR1 to TR4 is repeatedly energized and supplied with power to the motor 14 by the determined pulse width, the time average current value of the motor 14 becomes the current value I determined as described above. It is to be. The value of the current supplied to the motor 14 is as described above.
The current value is fed back to the PWM circuit 32 and is controlled more accurately.

Thus, a current corresponding to the magnitude and direction of the steering torque is supplied to the motor 14, so that an increase in power according to the steering torque is obtained.

On the other hand, when a low level (L) signal is input from the NOR circuit 35 to the PWM circuit 32, that is, when the vehicle speed is equal to the predetermined speed (15 km / h)
If the above is the case, or if an abnormality occurs in the first torque sensor 20 or the like, the PWM circuit 32 outputs the energizing signal to the transistors TR1 to TR4 regardless of the steering torque value input from the first torque sensor 20. The motor 14 is stopped to supply power to the motor 14, and the motor 14 does not increase the steering force.

FIG. 3 shows the clutch drive circuit 50 and the electromagnetic clutch device 15
The internal configuration of the field coil 15b is shown, and a clutch driving circuit 50 is a known Darlington-connected transistor.
TR5, TR6 and a protection resistor R2 connected to the base terminal of the transistor TR5. When a high-level (H) signal is input to the base terminal of the transistor TR5, the transistors TR5 and TR6 become conductive and the field coil 15b is energized. . As described later, when the AND circuit 59 outputs a high level (H) signal, that is, when the vehicle speed is equal to or lower than a predetermined speed (15 km / h) and there is no abnormality in the first torque sensor 20 or the like. ,
The electromagnetic clutch device 15 is, as described above, a field coil.
When the 15b is energized, the driving force of the motor 14 is transmitted to the reduction gear device 13 by the contact operation, and the AND circuit 59 outputs a low level (L) signal, that is, the vehicle speed exceeds the predetermined speed. Or, when the first torque sensor 20 or the like is abnormal,
The high level (H) signal is no longer input to the transistor TR5, the field coil 15b is deenergized, and the electromagnetic clutch device 15 is disengaged to interrupt the transmission of the driving force of the motor 14.

Returning to FIG. 1, the disconnection detecting circuit 55 detects an abnormality such as disconnection or short circuit of the vehicle speed sensor 22.
If the output signal value from 22 does not change within a predetermined period, it is determined that the vehicle speed sensor 22 is abnormal and high level (H)
Output a signal. On the other hand, the comparison circuit 56 compares the steering torque signal values supplied from the first and second torque sensors 20 and 21 and when the deviation between the two steering torque signal values falls outside a predetermined allowable range, these signal values become When substantially different, the first torque sensor 20 is considered to have failed and is set to a high level (H).
Output a signal.

The output signal of the comparison circuit 56 is inverted by an inverter 58 and
It is supplied to the D circuit 59. Therefore, if there is no abnormality in either of the first and second torque sensors 20 and 21, the inverter 5
8 outputs a high-level (H) signal, and the AND circuit 59 is in an open state.
A low level (L) signal is output from 58, and the AND circuit 59 is closed. In the latter case, the AND circuit 59 cannot output a high-level (H) signal, and the electromagnetic clutch device 15 is held in the disconnected state.

When a high level (H) signal from one of the disconnection detection circuits 55 and 56 is supplied to the NOR circuit 35 of the control circuit 30 via the OR circuit 57 as an abnormality detection signal, the NOR circuit 35 operates as described above. The low level (L) signal is output, and the AND circuit 59 is closed by the low level (L) signal, and the electromagnetic clutch device 15 is disconnected. still,
As can be understood from the above description, when one of the vehicle speed determination circuit 34, the disconnection detection circuit 55, and the comparison circuit 56 outputs a high level (H) signal, the electromagnetic clutch device 15 is disconnected, and at the same time, the motor 14 The power supply to the power supply will also be stopped.

In the above embodiment, the first and second torque sensors 20, 21
Detected the steering torque from the torsion angle of the steering shaft 2. However, the present invention is not limited to this, and the torque sensor may be mounted anywhere as long as the steering torque can be detected. 8
The steering torque may be detected from the twist angle of the steering wheel.

If necessary, two or more torque sensors having the same characteristics may be mounted, and an abnormality of the torque sensor may be detected by comparing these output values.

Further, although the motor 14 drives the shaft 8 to increase the steering force, the present invention may be applied to a power steering device that drives the steering shaft by a motor.

(Effects of the Invention) As described in detail above, according to the motor-driven power steering apparatus of the present invention, a plurality of sensors for detecting the steering torque are provided, and the steering torque values detected by these sensors are substantially different. At this time, the motor is not allowed to increase the steering force, so that the power steering device can have a fail-safe function in the event of a torque sensor failure, so that even when the torque sensor fails, there is no hindrance to travel and stable running can be achieved. It has an excellent effect of being secured.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a circuit diagram showing an internal configuration of an electronic control unit 16 for driving and controlling a motor and an electromagnetic clutch device of a power steering device according to the present invention, and FIG. FIG. 3 is a circuit diagram showing details of the internal configuration of the control circuit 30 and the motor drive circuit 40 shown in FIG. 1, FIG. 3 is a circuit diagram showing details of the internal configuration of the clutch drive circuit 50 shown in FIG. 1, and FIG. FIG. 5 is an overall configuration diagram of the power steering device according to the invention, and FIG. 5 is a more detailed configuration diagram of the ball screw portion 6, the reduction gear device 13, the motor 14, and the electromagnetic clutch device 15 in the power steering device shown in FIG. , Sixth
FIG. 7 is a partial side view of the steering shaft showing the state of attachment of the torque sensor. FIG. 7 is a graph showing the relationship between the steering torque and the output voltage of the torque sensor. FIG. 8 is a diagram showing the relationship between the steering torque and the current I supplied to the motor. 6 is a graph showing the relationship of. 1 ... steering wheel (handle), 6 ... ball screw part, 8 ... shaft, 13 ... reduction gear device,
14 ... motor, 15 ... electromagnetic clutch device, 16 ... electronic control device, 20 ... first torque sensor, 21 ... second torque sensor, 22 ... vehicle speed sensor, 50 ... clutch drive circuit, 56 ... Comparison circuit.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-254829 (JP, A) JP-A-57-203198 (JP, A) JP-A-61-275057 (JP, A) Japanese Patent Publication No. 45- 36967 (JP, B1)

Claims (1)

(57) [Scope of request for utility model registration] 1. A motor-driven power steering system comprising: a sensor for detecting a steering torque of a steering system; and a driving current of a motor for driving the steering system in accordance with the steering torque detected by the sensor to increase a steering force. The apparatus, wherein the sensors have substantially the same characteristics as one another, and
Each of the steering systems comprises a plurality of sensors which are integrally attached to each other via a common support member to detect a steering torque at the same point in the steering system, and a deviation of the steering torque value detected by these sensors is equal to or more than a predetermined value. A motor-driven power steering device, comprising: a prohibition unit that prohibits the motor from increasing the steering force when the motor is turned off.