JPH06227410A - Electric power steering device - Google Patents

Abstract

PURPOSE:To provide a small-sized and low-priced electric power steering device by providing a torque sensor control circuit comprising a torque sensor driving circuit and a signal amplifying circuit and a motor control circuit comprising a motor driving circuit and a control device in the same case to integrate the motor control circuit with the torque sensor circuit. CONSTITUTION:A torque sensor control circuit 11 having a motor control circuit 13 disposed and stored in the same case 19 is so constructed that a signal amplifying part for amplifying a detection signal of a torque sensor 8 includes a torque sensor amplifying circuit 9a only, and an output signal of a torque sensor 8, an output signal of a torque sensor amplifying circuit 9a and an output signal of a torque sensor driving circuit 10 are input to a control circuit 12 to judge the abnormality of the torque sensor 8. The auxiliary steering force amount is decided by a control device 12, and the steering torque of a steering shaft is decided using an output signal of the torque sensor amplifying circuit 9a and a car velocity signal from a car speed sensor 15. It is not necessary to provide a large current wiring part for running a motor current on a printed wiring board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering device.

[0002]

2. Description of the Related Art FIG. 10 shows a block diagram of a conventional electric power steering apparatus. This device includes a motor 1 for assisting the steering force and an ON-O of the motor 1.
Field effect transistors (hereinafter referred to as FETs) as four switching elements that control the rotation directions of the FF and the motor 1.
2a, 2b, 2c, 2d, a current detection circuit 3 composed of a resistor and a relay 4 connected via a key switch 7 between the bridge circuit and the main power source (battery) 6. And torque sensor signal amplification circuits 9a and 9b for amplifying the output of the torque sensor 8 for detecting the steering torque of the steering shaft, and a torque sensor control circuit 10 for driving the torque sensor 8. A control device 12 for controlling the steering force assist amount by switching the motor drive circuit 5 on and off and switching the polarity based on the output signals of the circuit 11 and the torque sensor signal amplification circuits 9a and 9b.
It has and. The motor drive circuit 5 and the controller 12 constitute a motor control circuit 13. The motor control circuit 13 and the torque sensor control circuit 11 are connected by a connection line 14. Reference numeral 15 is a vehicle speed sensor.

FIG. 11 is a printed wiring board 1 which constitutes a motor control circuit 13 of a conventional electric power steering apparatus.
6 shows the appearance of No. 6. This printed wiring board 16 has a large current (20 A or more) of the motor 1 of the motor drive circuit 5.
It has a large current wiring portion 17 necessary for flowing the heat and a heat radiating plate 18 for radiating heat generated when the switching element of the motor drive circuit 5 is driven.

[0004]

As shown in FIG. 11, in the conventional configuration, the motor control circuit is large, so that the motor control circuit and the torque sensor control circuit must be separated from each other. Not only does it require a connecting line to connect the circuit of the above, but the connecting line also has a shield wire and a feedthrough capacitor to eliminate the influence of disturbance noise received when transmitting the torque sensor amplified signal to the motor control circuit. It is necessary to take measures against noise such as.

An object of the present invention is to solve the above problems and to obtain an electric power steering apparatus which is compact and can be constructed at low cost.

[0006]

In order to solve the above-mentioned problems, the present invention relates to a motor connected to a steering shaft via a connecting means for assisting the steering force, and a motor drive circuit for driving this motor. A torque sensor for detecting a steering torque of the steering shaft, a torque sensor drive circuit for driving the torque sensor, a torque sensor signal amplification circuit for amplifying a detection signal of the torque sensor, and an output of the torque sensor signal amplification circuit A motor drive circuit comprising a torque sensor drive circuit and a torque sensor signal amplification circuit, and a control device for controlling the steering force assisting amount by switching the motor drive circuit on and off based on a signal and switching the polarity. A motor control circuit including a control device is housed and arranged in the same case.

[0007]

With the above construction, the motor control circuit and the torque sensor control circuit can be integrated, so that not only the connecting line for connecting the two becomes unnecessary, but also the shield line applied to the connecting line, There is no need for noise countermeasures such as through-type capacitors.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings of FIGS.

FIG. 1 is a block circuit diagram of an electric power steering apparatus according to an embodiment of the present invention. In FIG. 1, the same parts as those of the conventional one shown in FIG. 10 are designated by the same reference numerals.

In the present invention, as shown in FIG. 1, the torque sensor control circuit 11 and the motor control circuit 13 are housed and arranged in the same case 19. In the torque sensor control circuit 11, the torque sensor signal amplifying portion for amplifying the detection signal of the torque sensor 8 is only the torque sensor amplifying circuit 9a, and the output signal of the torque sensor 8, the output signal of the torque sensor amplifying circuit 9a, and the torque sensor. The output signal of the drive circuit is input to the control device 12, and the control device 12 determines the abnormality of the torque sensor 8. Reference numeral 30 is a resistance of the current detection circuit 3.

Further, in the electric power steering system of the present invention, since the control device 12 determines the steering force assist amount,
The torque sensor 8 measures the steering torque of the steering shaft.
The output signal of the torque sensor signal amplification circuit 9a that amplifies the torque sensor detection signal to the signal level that can be processed by the control device 12 and the vehicle speed signal from the vehicle speed sensor 15 are used.

Next, a method of determining when the torque sensor is abnormal for preventing malfunction of the electric power steering device will be described. In the conventional configuration, the abnormality determination of the torque sensor 8 is performed by comparing the output signals of the torque sensor signal amplification circuit 9a and the torque sensor signal amplification circuit 9b with the control device 12 and detecting a difference of a torque sensor abnormality when a difference of a predetermined value or more is detected. I was determined. On the other hand, in the present invention, the torque sensor control circuit 11 and the motor control circuit 13 are integrated, no noise countermeasure is required, and the signal in the torque sensor control circuit 11 can be input to the control device 12 without limitation. For the abnormality determination of the torque sensor, the control device 1 outputs the output signal of the torque sensor 8 and the output signal of the torque sensor drive circuit 10.
2 and converts it into a value corresponding to the output signal of the conventional torque sensor signal amplifying circuit 9b.
When a difference of a predetermined value or more is detected by comparing with the output signal Tm of “a”, it is determined that the torque sensor is abnormal.

FIG. 2 and FIG. 3 explain in detail the method of determining the abnormality of the torque sensor. The torque sensor 8 is
Upon receiving the sine wave drive signal from the torque sensor drive circuit 10, the torque detection signals S1 and S2 are output. The torque detection signals S1 and S2 are full-wave rectified by the torque sensor signal amplification circuit 9a as shown in FIG. Perform S1 ', S
2'DC signal, and then S1 'and S2'
Is amplified to a level that can be processed by the control device 12. This signal is Tm. The torque signal Tm is
This is a signal that determines the control current of the motor 1 by the control device 12.

FIG. 3 shows a method of detecting the torque sensor sub-signal in the abnormality determination of the torque sensor 8 according to the present invention. The torque sensor sub-signal is not used to determine the motor current under normal conditions, but is used for determining a large output abnormality such as operation stop during abnormal conditions. Therefore, the resolution is the torque signal Tm.
The resolution is lower than that of. Therefore, as shown in FIG. 3, first, the output signal D of the torque sensor drive circuit 10 is used as a synchronization signal to input the peak values S1P and S2P of the torque detection signals S1 and S2 to the controller 12, and the difference S1P-S2P is input to the controller 12. Is calculated, and this value is used as the torque sub-detection value T
Let s. Then, the torque signal Tm and the sub torque detection value Ts are compared, and when the difference exceeds a predetermined value, it is determined that the torque sensor is abnormal. Further, by directly inputting the torque detection signals S1 and S2 to the control device 12 and detecting a point where the peak values of S1 and S2 are equal to each other, the conventional configuration relies on the variation characteristic of the torque sensor amplifier circuit. Point correction (a slight vibration of the steering wheel occurs if the error of the middle point is large) can be surely performed.

Next, the structure of the present invention will be described with reference to FIGS. In FIG. 4, the housing 20 is made of a resin molded product and has FETs 2a, 2 as switching elements.
b, 2c and 2d are arranged, a switching element arrangement portion 21, a relay arrangement portion 22 for arranging the relay 4 which connects and disconnects the main power supply line, and a current detection resistor arrangement portion 23 for arranging a current detection resistor 30 for detecting a motor current. And an external connection section 24 for connecting the electric power steering control apparatus to the main power supply 6 and the motor 1, and a printed wiring board connection section 25 for connecting an electric signal of the housing 20 to the control apparatus 12 (see FIG. 9). And a FET that constitutes the motor drive circuit 5
2a, 2b, 2c, 2d, the relay 4, and the current detection resistor 30 are connected and arranged by soldering.

Here, the housing 20 is constructed by insert-molding the metal wiring board 26 in a resin-molded product so that the connection portion with each of the above-mentioned components is exposed. Further, the metal wiring board 26 has four FETs 2a, 2b, 2c,
2d is wired to form a bridge circuit, and the heat generated by this FET is radiated to the metal case 27.
A connecting portion 26a for connecting the FETs 2a, 2b, 2c, 2d is formed at a position parallel to the printed wiring board 28 and aligned with the height of the metal case 27. At a position close to the printed wiring board 28, a connection portion 26b with the current detection resistor 3a is provided.
And a connection portion 26c with the relay 4 and an external connection portion 24. Further, in order to supply signals and power from these parts to the control device 12, a printed wiring board connecting portion 25 is provided.
The terminals are arranged in a line for easy connection to the printed wiring board 28.

FIG. 8 shows the metal wiring board 26 which is insert-molded as the housing 20. The switching element arrangement portion 21, the current detection resistor arrangement portion 23, the relay arrangement portion 22 and the printed wiring board are shown. The connecting portion 25 and the external connecting portion 24 are all integrated as shown in FIG.
Further, by using polyphenylene sulfide resin as the resin for insert molding, heat of soldering when connecting the housing 20 and the printed wiring board 28, the FETs 2a, 2b, 2c, 2d, the current detection resistor 30 and the relay 4, It is possible to sufficiently withstand the heat generated from the FETs 2a, 2b, 2c, 2d when driving the motor.

FIG. 5 is an assembled sectional view of the electric power steering controller. The housing 20 includes FETs 2a, 2
Switching element placement portion 21 for fixing b, 2c and 2d
The heat generation of the FET can be radiated to the upper metal case 27 through the insulating material 29 and the heat radiation plate 30. Also, with this structure, the space of the printed wiring board 28 below the FET can be effectively utilized for mounting other components.
Further, since this heat dissipation structure has a high heat dissipation effect, the heat dissipation plate 30 can be downsized as compared with the conventional configuration.

FIG. 6 is a view showing a state in which the housing 20 having the components mounted thereon is attached to the printed wiring board 28. According to this embodiment, since it is not necessary to provide a large current wiring portion for passing the motor current on the printed wiring board 28, the printed wiring board 28 is downsized and the torque sensor control circuit 11 and the motor control circuit 13 are integrated. Can be converted.

FIG. 7 is a perspective view of an electric power steering controller in which the completed printed wiring board 28 of FIG. 6 is incorporated in a metal case 27.

[0021]

As described above, according to the present invention, since the motor control circuit and the torque sensor control circuit can be integrated, not only the connecting line for connecting the two becomes unnecessary, but also the connecting line is not provided. It also eliminates the need for noise countermeasures such as shielded wires and feedthrough capacitors.

Further, since the torque sensor control circuit and the motor control circuit are integrated, the signal in the torque sensor control circuit can be easily used. Therefore, one of the torque sensor signal amplification circuits is deleted and the torque sensor output signal is used. It becomes possible to make an abnormality determination. Further, by processing this torque sensor output signal, it becomes possible to surely correct even the midpoint fluctuation which has been a problem due to the secular change of the circuit characteristics.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an electric power steering apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a method of amplifying a torque sensor main signal in the present invention.

FIG. 3 is an explanatory diagram for explaining a method of detecting a torque sensor sub-signal in the present invention.

FIG. 4 is an exploded perspective view showing a configuration of an electric power steering device according to the present invention.

FIG. 5 is a sectional view of the electric power steering device.

FIG. 6 is a perspective view showing a main part of the electric power steering device.

FIG. 7 is a perspective view showing the same appearance.

FIG. 8 is a perspective view of the electric power steering device.

FIG. 9 is a perspective view showing a metal wiring board inside the same housing.

FIG. 10 is a block circuit diagram of a conventional electric power steering device.

FIG. 11 is a perspective view showing a printed wiring board of a conventional electric power steering device.

[Explanation of symbols]

 1 Motor 2a, 2b, 2c, 2d Field effect transistor 5 Motor drive circuit 8 Torque sensor 9a Torque sensor signal amplification circuit 10 Torque sensor drive circuit 11 Torque sensor control circuit 12 Controller 13 Motor control circuit 19 Case 20 Housing 21 Switching element Arrangement part 22 Relay arrangement part 23 Current detection resistor arrangement part 24 External connection part 25 Printed wiring board connection part 26 Metal wiring board 26a, 26b, 26c Connection part 27 Metal case 28 Printed wiring board 29 Insulation material 30 Heat dissipation plate

Claims (5)

[Claims] 1. A motor coupled to a steering shaft via coupling means for assisting a steering force, a motor drive circuit for driving the motor, and a torque sensor for detecting a steering torque of the steering shaft, A torque sensor drive circuit that drives a torque sensor, a torque sensor signal amplification circuit that amplifies a detection signal of the torque sensor, and an intermittent signal and a polarity switching of the motor drive circuit based on an output signal of the torque sensor signal amplification circuit. A torque sensor control circuit including the torque sensor drive circuit and the torque sensor signal amplification circuit, and a motor control circuit including the motor drive circuit and the control device in the same case. Electric power steering device stored in the 2. A printed wiring board on which components constituting a torque sensor control circuit and a control device are arranged, and a resin molded product on which components constituting a motor drive circuit are arranged and which are arranged on the printed wiring board. And a metal case in which the printed wiring board and the housing are housed and arranged, and the housing includes a connection portion with an external device, a connection portion with the printed wiring board, and the motor drive circuit. A metal wiring board is insert-molded in a resin-molded product so that a connection portion with a component constituting the is exposed.
The electric power steering device described. 3. A heat-generating component among components constituting a motor drive circuit is arranged in the vicinity of a metal case, and a heat radiating plate is interposed between the heat-generating component and the metal case via an insulating material to prevent heat from the heat-generating component. The electric power steering device according to claim 2, wherein the heat is dissipated to the metal case via the heat dissipation plate. 4. The electric power steering apparatus according to claim 3, wherein the casing is made of polyphenylene sulfide resin. 5. A motor coupled to a steering shaft via coupling means for assisting the steering force, a motor drive circuit for driving the motor, a torque sensor for detecting a steering torque of the steering shaft, A torque sensor drive circuit that drives a torque sensor, a torque sensor signal amplification circuit that amplifies a detection signal of the torque sensor, and an intermittent signal and a polarity switching of the motor drive circuit based on an output signal of the torque sensor signal amplification circuit. And a control device for controlling the steering force assisting amount, and determines a torque sensor abnormality based on the output signal of the torque sensor drive circuit, the output signal of the torque sensor, and the output signal of the torque sensor signal amplification circuit. An electric power steering device configured as described above.