JPH01275268A - Motor-driven power steering device - Google Patents

Abstract

PURPOSE:To make steering control with high stability by furnishing a plurality of contactless sensing means for sensing the steering torque around the rotary shaft for steering. CONSTITUTION:In a motor-driven power steering device, the steering torque applied to an upper shaft 1, at whose top a steering wheel is mounted, is transmitted to a lower shaft 2 through a torsion bar 8, and thereby a pinion 3 is rotated to cause a rack shaft 4 to slide. Thus steering is conducted. As an aid steering force, the power of a motor 5 is transmitted to the lower shaft 2 via a pinion 6 and a bevel gear 7. Therein the two shafts 1, 2 in relative rotation with twisting of the torsion bar 8 are equipped, at their ends on mating side, with magnetic drums 9, 10, and magnetic sensors 11a, 11b are arranged in linear symmetry position to these magnetic drums 9, 10 so as to constitute a torque sensor of non-contact type.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides torque control in which an increase of 1 to 1 torque is obtained in a direction to assist the torque applied to a rotating shaft. The present invention relates to a torque control device, and particularly to a torque control device suitable for a groove power steering link system for an automobile.

[Conventional technology]

In order to reduce driver fatigue and increase safety, the application of so-called power steering has become quite common in steering systems for automobiles, etc., but this system has traditionally been hydraulically actuated. was the mainstream.

However, in recent years, so-called electric power steering systems, which use an electric actuator such as an electric motor as a source of auxiliary steering force, have been widely adopted from the standpoint of equipment in the engine room and enrichment of control contents. It is in.

By the way, in this type of electric power steering device, the torque detector is preferably a non-contact type in order to improve durability and reliability.
No. 2, etc. are known.

[Problem to be solved by the invention]

The above-mentioned conventional technology includes a method for detecting failure of a
There was a safety issue due to the lack of consideration given to what to do after a failure.

1] The object of the present invention is to use a double system for the silk output means□
The objective is to increase safety.

[Means to solve the problem]

The above purpose is to arrange a plurality of magnetic sensors arranged facing the first and second magnetic drums on the circumference -F of this magnetic tram, and to find the mutual difference in the torque detected by each sensor. , when this difference is outside the predetermined range, 1~
This is achieved by eliminating the auxiliary steering force due to the lux sensor failure.

[Effect]

Magnetic 1~Multiple magnetic sensors placed around the ram are
Each detects 1 to 1 lux. Thereby, it is possible to compare and judge whether the husband's torque is normal, and the auxiliary steering torque of the electric power steering device can be safely eliminated, thereby increasing safety.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The 1 to 1 torque control device according to the present invention will be described in detail below with reference to illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to a rack-and-pinion electric power steering system for automobiles, and numeral 1 indicates upper shirts 1 to . 2 is lower shirt 1
~． 3 is a pinion, 4 is a rack shaft, 5 is an electric motor, 6 is a pinion, 7 is a bevel gear, 8 is a torsion bar, 9 and 10 are magnetic drums for torque sensors, 1.1a and llb are magnetic sensors for torque sensors , 12 is a circuit board, 13 is various control circuit elements including a microcomputer, 14 is a power FET for switching, 15 is a heat sink, 16 is an internal connection lead, 17 is a connector, 20 is a sensor holding part, 21. 2 is a motor holding part, 22 is a rack holding part, 23 to 26 are bearings, 27 and 28 are oil seals, and 29 is a deseal.

A steering handle is attached to the upper shirt l-1,
As a result, the steering torque applied to the handle shaft 1 is 1 to
- It is transmitted to the lower shirts 1 and 2 via the rotation bar 8, and steering is performed by rotating the pinion 3 and sliding the rack shaft 4.

On the other hand, a pinion 6 is attached to the rotating shaft of the electric motor 5, and is connected to the lower shaft 2 via a bevel gear 7.
Torque is transmitted. Therefore, when the electric motor 5 generates a torque of 1 to 1, this is applied to the lower shirt 1 by 2
As a result, the auxiliary steering force (power assist I-
) will be obtained.

The magnetic rams 1 to 9 and 10 are drums whose peripheral portions are magnetized at a predetermined pitch, and are attached to the lower end of the upper shirt +-1 and one end of the lower shaft 2, respectively. Therefore, when the upper shaft 1 is rotated, it rotates together with the upper shaft 1, and the I-lux transmitted from the upper shirt 1 to the lower shaft 2 causes twisting in the hexion bar 8. Displacements appear in the rotational angular positions of the magnetic trams 9 and 10, which makes it possible to detect torque.

A magnetic sensor li is combined with these magnetic drums 9 and 10 to constitute a non-contact torque sensor as a whole.
a and 1.1 b are arranged in axially symmetrical positions with respect to the magnetic drum 9°10.

In addition, the control circuit element 3 of the circuit board 12 and the heat sink 1
57 power F E l"] 4, and as a control circuit unit U consisting of a connector 17 etc.
It has become ~.

The sensor holding part 20, the motor holding part 21, and the rack holding part 22 are made of aluminum die-casting or the like, and hold the pan 1 to 1 shafts and the pinion shaft 2 by means of bearings 23 to 26. It also serves as a mounting member for the electric motor 5, and also functions as a gear box for the pinion 3 and rack shaft 4, and also functions to unitize the whole unit. .

FIG. 2 shows the entire control circuit of the electric motor 5 including the control circuit units 1 to U, in which the torque signal τ from the magnetoresistive element 11 and the vehicle speed signal V representing the speed of the vehicle from the vehicle speed sensor 30 are transmitted. The signals are input to the microcomputer 13A and calculated, processed by the logic circuit 13B, and the bridge-connected FETs 14A to 14D are switched to perform chopper control of the electric motor 5, and the current is controlled by the detection signal of the current sensor 13D. so that a predetermined auxiliary steering force (torque) can be obtained.

At this time, the power from battery B is turned on and off by the car's key switch K, and the voltages of 5V and 7V stabilized by the power supply circuit -3C are supplied to the microcomputer 1.3A and logic circuit 1.3B. It is now possible to do so. Also,
Power is supplied to the electric motor 5 through the contacts of the relay R, and in the event of an abnormality, the motor 5 is turned off by releasing the relay R.

Figure 3 shows the characteristics of assist torque (auxiliary steering force) with respect to the value detected by the I-lux sensor, with vehicle speed as a parameter, and the assist torque decreases as the vehicle speed increases. .

Next, a more detailed explanation will be given with reference to FIGS. 4 to 6.

In this embodiment, as is clear from FIG.
]A4.1. B1 to lB4 and the other magnetic drum 1
It is composed of a total of four sets of MR elements, two sets of bridge-connected MR elements 2A and 1 to 2A/1.2B1 to 2B4, which are provided corresponding to MR elements 0 and 1.2B1 to 2B4.

Now, let us assume that the steering handle is operated and a torque of a value corresponding to upper shirt 1 to 1 is applied and rotated.

Then, the voltage eA1 in FIG. 5 is applied from the bridge formed by one of the MR elements IA1 to IA1 and A4 corresponding to the magnetic drum 9, and the voltage eA1 of the other MR element IB1 to IB4 is applied.
A voltage erll is generated from each of the bridges.

These voltages e^1 and eBl are generated with a 90° phase difference, so the upper shirt l-
When the position of a rotation angle of 1 is set as a reference point O, the rotation angle θ1 from this reference point O is 0l-tan" (e Bl
/ e Al).

Also, one MR element 2A1 corresponding to the magnetic drum 10
A voltage eA2 is generated from the bridge made up of the MR elements 2A4 to 2A4, and a voltage OB2 is generated from the bridge made up of the MR elements 2B-1 to 284. These voltages eΔ
2 and eB2 also have a 90° phase difference, and the sensing position is rotated by a rotation angle 02 from the reference point O. Therefore, the rotation angle 02 here is 02 = tan-' (e
B2/e A2).

On the other hand, since the upper shaft 1 and the lower shirt I-2 are connected by a torsion bar 8, when torque is transmitted between these shafts 71 and 71, the magnetic drums 9 and 10 The difference in rotation angle between them appears as O, and θ=θ knee 02.

Therefore, the torque τ can be detected based on this rotation angle difference of 0, and the torque can be determined as τ=KO=KC0z−02). Here, K is a constant determined by the rigidity of the torsion bar 8, etc.

In the same way, 1 to .tau.' can be determined from the magnetic sensor 1.1b.

Therefore, the microcomputer 13A performs the interrupt processing shown in FIG. Magnetic sensor l every 5 rn S
Voltage of la e/111 (!131+ eΔ2+ e1
Sample and import 32, calculate rotation angle OL, 02, calculate torque A1.

Left and right discrimination based on the sign of 1 to luk, and the torque Mc
It searches the map, calculates IHc using the vehicle speed correction coefficient kv, and further outputs the command I) 40 to the D/A converter 44 as digital data of 8 pins 1-.

At this time, the operational amplifiers 40 to 43 have voltages C^1 to QR2.
An amplifier is configured to take in the data, and the microcomputer 13A internally converts the data into A/D and takes in the data. On the other hand, the vehicle speed signal V is taken into the microcomputer 13A via the input filter F and counted.

In this way, the signal processed by the microcomputer 13A as shown in FIG. 6, input to the D/A converter 44, and converted into an analog signal becomes a non-inverting input of the deviation amplifier 45, and on the other hand,
The current signal of the motor 5 detected by the current sensor i 3 D becomes the inverting input of the deviation amplifier 45 , and the deviation outputs thereof become the input of the pulse width modulation signal generator (PWM) 46 . The output of PWM4.6 is a right/left discrimination output signal 1.

In order to take an AND with Q, it is passed through an AND circuit /17.48 and then input to FET14B, 14+).

On the other hand, FET1, 4A, 14. C creates a 15V power supply in the power supply circuit 13C to avoid insufficient voltage.
This is supplied via drive FET4.9.50,
It's on, it's off. Note that the inverters 51 and 52 are for buffers.

By the way, the microcomputer i3A samples and takes in the signal from the magnetic sensor llb every 0.2 to 2 mS in the interrupt process shown in FIG. 7, and calculates the torque τ'.

In the next step, the difference between the calculated value and the value just obtained is determined by the process shown in FIG.
The warning lamp lights up and relay R is released.

Therefore, according to this embodiment,! - Since the lux sensor is a dual system and failure can be determined, there is an effect that 1 to lux detection is reliable and highly reliable.

Further, according to this embodiment, the torque sensor can be made into a dual system by using only two magnetic sensors, and there is an effect that the torque sensor can be made into a dual system with low cost 1 or more.

〔Effect of the invention〕

According to the present invention, there is an effect that it is possible to provide a low-cost and small-sized torque sensor equipped with two torque detectors and an electric power steering device with reliable torque control and high safety.

[Brief explanation of the drawing]

Fig. 3 is a partial sectional view showing an embodiment in which the torque control device according to the present invention is applied to an electric power steering device;
Fig. 2 is a block diagram of control circuit unit 1~, Fig. 3 is a control characteristic diagram, Fig. 4 is a circuit diagram to control circuit unit I, and Fig. 5 is a block diagram of control circuit unit 1~.
6 is a waveform chart for explaining the operation, FIG. 6 is a flowchart 1 to 1 for explaining the operation, and FIG. 7 is a flowchart 1 to 1 for determining a torque sensor failure. Handshake 1. Wheel shaft, 2. Pinion shaft, 3. Pinion, 4.
・Rack shaft, 5...Electric motor, 6-・Pinion, 7・
Bevel gear, 8... 1-1 shaft bar, 9, 10... Magnetic tram, 11. Magnetoresistive element, 12... Circuit board, 13.
...Control circuit element, 14...Power FET, U...Control circuit unit.

Claims (1)

[Scope of Claims] 1. An electric motor system that detects the steering torque transmitted along a predetermined rotation axis and controls the auxiliary steering torque to be applied to the torque output side of the rotation axis according to the detection result. An electric power steering device characterized in that a plurality of non-contact sensor means for detecting the torque are provided around the rotation shaft. 2. In the device described in claim 1, the non-contact torque detection means is installed at a predetermined interval between the input side and the output side of the rotating shaft, and has a signal track on the surface of which a magnetic signal is recorded. The structure is composed of first and second rotating drums, and a magnetoresistive element disposed on a fixed part facing each of these rotating drums, and the relative displacement due to twisting of the rotation axis between the rotating drums is controlled by the magnetoresistive effect described above. An electric power steering device characterized in that it is a torque detection device that detects torque as a resistance change of an element. 3. In the device described in claim 1, the plurality of non-contact type sensor means are arranged on fixed parts facing each of the first and second rotating drums according to claim 2, and a magnetoresistance effect is provided. An electric power steering device characterized in that it is a plurality of magnetic sensors composed of elements. 4. The electric power steering device according to claim 1, wherein the rotating shaft is a steering wheel shaft of an automobile, and the auxiliary steering torque acts as an auxiliary steering force. . 5. In the device described in claim 2, the signal due to the resistance change of the magnetoresistive element has a sine value of a signal that changes the rotational angular position of the first and second magnetic drums in a sine wave manner. An electric power steering device characterized by magnetically detecting a cosine value. 6. In the device according to claim 5, the rotation angles of the first and second magnetic drums are calculated based on the arctangent value of the ratio of the sine value and the cosine value of the signal, and the rotation angles of the first and second magnetic drums are An electric power steering device characterized in that the torque is detected as a difference between rotation angles of two magnetic drums. 7. In either claim 5 or 6, means for determining whether the difference in torque obtained from the respective magnetic sensors described in claim 3 is within a predetermined range. An electric power steering device characterized by having. 8. An electric power steering device according to claim 7, characterized in that the auxiliary steering torque is eliminated when the torque difference falls outside a predetermined range.