JPH0624941B2 - Torque control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque control device capable of increasing a torque in a direction that assists the torque given to a rotary shaft, and more particularly to a torque control device. , A torque control device suitable for an electric power steering 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 such as automobiles. It was.

However, in recent years, from the viewpoint of fitting in the engine room and the abundance of control contents, the so-called electric power steering system that uses an electric actuator such as an electric motor as a source of auxiliary steering force has been widely adopted. It is in.

By the way, in this electric power steering apparatus, in order to take full advantage of its miniaturization and easy fitting, it is desirable to make it as unitary as possible.

Therefore, in the conventional device, as described in JP-A-57-47251, the electric motor for generating the auxiliary steering force and the control circuit unit thereof are integrated.

[Problems to be solved by the invention]

The above-mentioned conventional technology does not consider mounting of a sensor for torque detection or heat generation of the electric motor, and there is a decrease in reliability due to the presence of a connector or wiring lead between the sensor and the control circuit unit, and noise resistance is maintained. There was a problem with the additional element and use for, and the countermeasure against the temperature rise of the control circuit unit.

The object of the present invention is a torque that has no problems in reliability, noise resistance, heat resistance, etc. due to unitization, can be sufficiently miniaturized, and has good mountability when applied to an electric power steering device for automobiles. It is to provide a control device.

[Means for solving problems]

The above object is to provide first and second magnetic drums attached to the input side and the output side of the rotary shaft, and the sine value and cosine of a signal that changes the rotational angle positions of the first and second magnetic drums in a sine wave shape. As a value, first and second magnetic detection elements for non-contact magnetic detection, an electronic control circuit unit integrally holding these first and second magnetic detection elements, and mounting of this electronic control circuit unit A sensor holding portion for positioning the first and second magnetic detection elements with respect to the vicinity of the first and second magnetic drums is formed, and a holding member for the rotary shaft is formed together with the sensor holding portion. The electronic control circuit unit calculates the rotation angles of the first and second magnetic drums by the arctangent value of the ratio of the sine value to the cosine value of the signal, and calculates the rotation angles of the first and second magnetic drums. 1st and 2nd magnetic field Detecting the torque as a difference of the rotation angle of the arm, the auxiliary torque is achieved so as to be controlled.

[Work]

Since the sensor and control circuit unit are integrated, there is no need for external wiring leads or connectors between them, there is almost no risk of picking up noise, and therefore no special consideration is given to noise resistance. Further, since the control circuit unit is not in contact with the electric motor, there is no problem in heat resistance and sufficient reliability can be easily obtained.

〔Example〕

Hereinafter, a torque control device according to the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment in which the present invention is applied to an electric power steering for a rack and pinion type automobile, in which 1 is a handle shaft, 2 is a pinion shaft, 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, 11 is a magnetoresistive element for torque sensors, 12 is a circuit board, 13 is a chip microcomputer, etc. Various control circuit elements including, 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 is a motor holding part, 22 is a rack holding part, 23- 26
Is a bearing, 27 and 28 are oil seals, and 29 is a dust seal.

A steering handle is attached to the handle shaft 1, whereby the steering torque applied to the handle shaft 1 is transmitted to the pinion shaft 2 via the torsion bar 8, and the pinion 3 is rotated and the rack shaft 4 is slid. Steering is performed.

On the other hand, a pinion 6 is attached to the rotary shaft of the electric motor 5, and is connected to the pinion shaft 2 via a bevel gear 7 so that torque is transmitted. Therefore, when the electric motor 5 generates torque, this is given to the pinion shaft 2,
As a result, an auxiliary steering force (power assist) is obtained.

The magnetic drums 9 and 10 are drums whose peripheral portions are magnetized with predetermined pitches, and respectively include a lower end of the handle shaft 1 and a pinion shaft 2.
It is attached to the upper end of. Therefore, when the handle shaft 1 is rotated, the handle shaft 1 is rotated together with the handle shaft 1, and the torque transmitted from the handle shaft 1 to the pinion shaft 2 causes the torsion bar 8 to be twisted.
Displacement appears at the rotation angle positions of 10 and 10, and this enables torque detection.

A magnetoresistive element 11 which is combined with these magnetic drums 9 and 10 to form a non-contact type torque sensor as a whole.
Is integrated into a control circuit unit U including a control circuit element 13 on the circuit board 12, a power FET 14 on the heat sink 15, and a connector 17, and is unitized. The control circuit unit U is held by a sensor. The magnetic drum 9 can be installed by simply attaching it to the specified part of the sensor (sensor housing) 20.
A predetermined positional relationship with respect to 10 is obtained.

Sensor holder 20, electric motor holder 21, and rack holder
22 is made of aluminum die casting etc., bearings 23 to 26
Thereby constitutes a holding member for rotatably holding the handle shaft 1 and the pinion shaft 2, and also serves as a mounting member for the control circuit unit U and the electric motor 5, and also functions as a gear box for the pinion 3 and the rack shaft 4, and , Also works to unitize the whole.

FIG. 2 shows the entire control circuit of the electric motor 5 including the control circuit unit U. The torque signal .tau. From the magnetoresistive element 11 and the vehicle speed signal v from the vehicle speed sensor 30 representing the speed of the vehicle are stored in the microcomputer 13A. The logic circuit
FET 14A with signal processing at 13B and bridge connection
.About.14D are operated to perform a switching control of the electric motor 5 and current is controlled by a detection signal of the current sensor 13D so that a predetermined auxiliary steering force (torque) can be obtained.

At this time, the power from the battery B is turned on / off by the key switch K of the automobile, and the voltages of 5V and 15V stabilized by the power supply circuit 13C are the microcomputer 13A and the logic circuit 13B.
Is being supplied to. Further, the electric power for the electric motor 5 is supplied through the contact of the relay R, and is turned off by releasing the relay R when an abnormality occurs.

FIG. 3 shows the assist torque (auxiliary steering force) characteristic with respect to the value detected by the torque sensor. The vehicle speed is used as a parameter. The assist torque decreases as the vehicle speed increases. There is.

Next, a more detailed description will be given with reference to FIGS.

In this embodiment, as is clear from FIG. 4, the magnetoresistive element 11 functions to detect the magnetism of the first magnetic drum 9 and the magnetism of the second magnetic drum 10, respectively. 2 corresponding to the magnetic drum 9 of
A pair of bridge-connected magnetoresistive elements 1A1 to 1A4,
A first magnetic detection element 1B1 to 1B4 and two sets of bridge-connected magnetoresistive elements 2A1 to 2A4 and 2B1 to 2 provided corresponding to the second magnetic drum 10.
And a second magnetic detection element made of B4.

Therefore, the steering wheel is now operated and the steering wheel shaft 1
It is assumed that a certain value of torque is applied to and the motor is rotated.

Then, the voltage e _{A1 of} FIG. 5 is obtained from the bridge formed by one of the magnetic resistance elements 1A1 to 1A4 corresponding to the magnetic drum 9, and the other magnetic resistance element 1B1 to 1B4.
A voltage e _B1 is generated from each of the bridges.

These voltages e _A1 and e _B1 are generated with a 90 ° phase difference, so that when a certain position of the rotation angle of the handle shaft 1 is taken as the reference point 0, The rotation angle θ ₁ is calculated by θ ₁ = tan ⁻¹ (e _B1 / e _A1 ).

Further, one magnetic resistance element 2A corresponding to the magnetic drum 10
The voltage e _A2 is generated from the bridge composed of 1 to 2A4, while the voltage e _B2 is generated from the bridge composed of the magnetoresistive elements 2B1 to 2B4. These voltages e _A2 and e
_B2 also has a 90 ° phase difference, and the rotation angle θ from the reference point 0
_The sensing position is rotating only ₂ . Therefore, the rotation angle θ ₂ here is obtained by θ ₂ = tan ⁻¹ (e _B2 / e _A2 ).

On the other hand, since the handlebar 1 and the pinion shaft 2 are connected by the torsion bar 8, when torque is transmitted between these shafts, rotation occurs between the magnetic drums 9 and 10 depending on the magnitude of the torque. The angle difference appears as θ, and θ = θ ₁ −θ ₂
Becomes

Therefore, the torque τ can be detected from the difference θ in the rotation angle, and the torque can be obtained by τ = Kθ = K (θ ₁ −θ ₂ ). Here, K is a constant determined by the rigidity of the torsion bar 8.

Therefore, the microcomputer 13A uses the interrupt process shown in FIG.
The voltages e _A1 , e _B1 , e _A2 , and e _B2 are sampled and taken in every 0.2 to 0.5 mS, the rotation angles θ ₁ and θ ₂ are calculated, the torque is calculated, the right rotation and the left rotation are determined by the sign of the torque, Search I _MC Matsupu for torque, I _MC by the vehicle speed correction coefficient kv
Then, the I _MC command is output to the D / A converter 44 as 8-bit digital data. At this time, the operational amplifiers 40 to 43 form an amplifier for taking in the voltages e _{A1 to} e _B2 , and the microcomputer 13A internally A / D converts and takes in. On the other hand, the vehicle speed signal v is taken into the microcomputer 13A via the input filter F and counted.

Thus, the processing is performed by the microcomputer 13A as shown in FIG.
The signal input to the D / A converter 44 and converted into an analog signal is
Then, it becomes a non-inverting input of the deviation amplifier 45, while the current signal of the electric motor 5 detected by the current sensor 13P is
It becomes the inverting input of 45, and these deviation outputs become the input of the pulse width modulation signal generator (PWM) 46. And PWM
The output of 46 is ANDed with the right and left discrimination output signals r and l.
It becomes the input of 14D.

On the other hand, the FETs 14A and 14C are turned on and off by producing a 15V power source by the power source circuit 13C so that the gate voltage is not insufficient, and supplying this through the drive FETs 49 and 50. The inverters 51 and 52 are for buffers.

Therefore, according to this embodiment, since the control circuit unit U and the magnetoresistive element 11 are integrated and unitized, no external wiring lead is required, the assembly is easy, and the probability of picking up noise is high. It is small, compact, and highly reliable.

Further, according to this embodiment, since the control circuit unit U is not in contact with a portion such as the electric motor 5 which may have a high temperature, there is no problem in temperature control, and the heat generated by aluminum die casting or the like is relatively high. Since the control circuit unit U is directly attached to the sensor housing (sensor holding portion 20) with good radiation, cooling fins can be made small, and in some cases it can be omitted, so weight reduction is easy. is there.

Further, according to this embodiment, most of the mechanical portion of the power steering device including the electric motor 5 is the sensor holding portion.
Since 20 is integrated with the electric motor holding portion 21 and the rack holding portion 22, it is compact and easy to wear in the engine room of the automobile, and a sufficient cost reduction can be achieved.

In addition, according to the above embodiment, the torque sensor is 4
Since a pair of bridge-connected magnetoresistive elements 1A1 to 2B4 are used, there is an effect that signal detection is reliable and reliability is high.

〔The invention's effect〕

According to the present invention, since the entire unit can be fully implemented without lowering the reliability, it is possible to easily provide a small torque control device that ensures torque control and is small in size.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment in which a torque control device according to the present invention is applied to an electric power steering device, FIG. 2 is a block diagram of a control circuit unit, FIG. 3 is a control characteristic diagram, and FIG. Is a circuit diagram of the control circuit unit, FIG. 5 is a waveform diagram for explaining the operation, and FIG. 6 is a flow chart for explaining the operation. 1 ... Handle shaft, 2 ... pinion shaft, 3 ... pinion, 4 ... luck shaft, 5 ... motor, 6 ... pinion,
7 ... Bevel gear, 8 ... Torsion bar, 9,10 ... Magnetic drum, 11 ... Magnetoresistive element, 12 ... Circuit board, 13 ...
Control circuit element, 14 ... Power FET, U ... Control circuit unit.

Claims (3)

[Claims] 1. A torque control device of a system for detecting a torque transmitted along a predetermined rotating shaft and controlling an electric motor for applying an auxiliary torque to a torque output side of the rotating shaft according to the detection result. , The first and second magnetic drums respectively mounted on the torque input side and the torque output side of the rotary shaft, and the sine value of a signal that changes the rotational angle positions of the first and second magnetic drums in a sine wave shape. And a first and second magnetic detection element for magnetically detecting the cosine value in a non-contact manner, an electronic control circuit unit integrally holding these first and second magnetic detection elements, and this electronic control circuit unit. A sensor holding portion, which is attached so as to position the first and second magnetic detection elements in the vicinity of the first and second magnetic drums, and a holding portion for the rotary shaft together with the sensor holding portion. An electric motor holding portion so as to form a formed, the electronic control by the circuit unit, the arctangent value of the ratio of the sine value and cosine value of the signal the first and second
The torque control device is configured to calculate the rotation angle of the magnetic drum, detect the torque as a difference between the rotation angles of the first and second magnetic drums, and control the electric motor. 2. The torque control device according to claim 1, wherein the rotating shaft is a steering wheel shaft of an automobile, and the auxiliary torque acts as an auxiliary steering force. . 3. The automobile according to claim 2, wherein the automobile is provided with a rack and pinion type steering system, and the electric motor has a rotation shaft which is substantially parallel to a sliding direction of the rack. A torque control device which is directly attached to the electric motor holding portion.