Power steering system.

Abstract

Achieving both excellent maneuverability and straight-line stability in all vehicle conditions. [Solution] A speed detection device retrofitted to the vehicle's eddy current instrument generates a high-resolution pulse signal. This pulse signal is then input to the power steering's calculation control device through an additional circuit that reduces it by a constant ratio. This ensures easy steering at low speeds while allowing for variable steering force at high speeds, thus achieving both operability and straight-line stability to suit all vehicle conditions.

Description

Technical Field

[0001] The present invention relates to a signal processing device having a variable function, which is attached to a control device for power steering.

Background Art

[0002] Power steering devices that use an electric motor or a hydraulic cylinder to assist the force required to steer the steering device of a vehicle in response to the driver's operation of the steering wheel have been put into practical use. Such a power steering device is equipped with a torque sensor and a vehicle speed sensor that detect the steering torque applied by the driver's operation of the steering wheel, as well as an electric motor and a hydraulic cylinder that generate steering assist force. The burden on the driver is reduced by generating the steering assist force by controlling the current or voltage and the hydraulic pressure in accordance with the detected steering torque signal and the signal from the vehicle speed sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] The conventional power steering system described in Patent Document 1 is shown. In such a power steering system, the steering assist force is set at the vehicle manufacturing stage, so it can be used when driving on highways, mountain roads, city streets, and sometimes even on motorsports circuits. In particular, changing the tires or components of the suspension system greatly changes the steering reaction force characteristics, so it is difficult to achieve both operability and straight-line stability with a single set of steering assist forces.

[0006] On the other hand, as described in Non-Patent Document 1, there were also systems that used an oscillator to input a signal as a dummy vehicle speed signal to electronically controlled power steering, and the input frequency was manually switched. With such oscillators, the driver had to switch the frequency depending on the vehicle speed, and problems arose such as the steering being too light at high speeds and poor straight-line stability if the maximum steering assist force at zero vehicle speed was used, and the steering force being too heavy at low speeds if the steering force was adjusted to match that at high speeds.

[0007] It is also conceivable to generate a speed signal by measuring the vehicle speed signal, performing calculations with a microcomputer, and increasing or decreasing the output frequency. However, this method not only complicates the circuit, but also makes it difficult to guarantee things like startup timing delays, since the power steering control unit (ECU) is also a microcomputer. [Means for solving the problem]

[0008] In this invention, a vehicle speed detection device that generates a higher-than-normal vehicle speed signal from the arithmetic control unit (ECU) is attached to the vehicle speed signal wiring, which is a control parameter for power steering. A signal processing device is then added to reduce the vehicle speed signal, and the reduction rate is made variable. In this way, no signal is generated when the vehicle speed is zero, so the same signal-free state is observed in all switching modes. When the vehicle speed increases, the pulse count reduction rate according to the vehicle speed can be varied in stages. [Effects of the Invention]

[0009] According to the present invention, the amount of steering assist when turning the steering wheel straight at zero vehicle speed is the same and reaches the maximum value at all switch positions. As the vehicle speed increases, the number of pulses generated by the signal processing device decreases in a ratio set by the toggle switch relative to the vehicle speed pulse generated by the vehicle speed detection device, and the power steering assist amount command value of the calculation control device decreases.

[0010] When the number of input pulses to the signal processing device is greater than that of the reference rotation pulse, the assist amount decreases, the direct feel during traveling increases, and the straight-line stability improves. Conversely, when the number of input pulses is less than that of the reference rotation pulse, the assist amount increases, and the steering wheel operation during traveling becomes lighter. In this way, by varying the frequency ratio of the pulses according to the vehicle speed instead of using fixed pulses, the steering force at high speeds can be made variable while ensuring ease of steering at low speeds. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] [Figure 1] Longitudinal sectional view of the retrofitted speed detection device [Figure 2] Transverse sectional view of the retrofitted speed detection device [Figure 3] Development view of the sensor support member in the retrofitted speed detection device [Figure 4] Internal block diagram of a general Hall IC [Figure 5] Characteristic diagram of Hall IC with omnipolar (active, high) characteristics [Figure 6] Operation diagram in the case where the number of magnet pole pairs is 1 and the characteristics of two installed Hall ICs are omnipolar (active, high) characteristics. [Figure 7] Overview of vehicle speed signal processing device [Figure 8] Schematic diagram of electric power steering equipped with the vehicle speed signal processing device [Figure 9a] Electric power steering operation characteristics controlled with double pulses and equipped with the signal processing device [Figure 9b] Electric power steering operation characteristics controlled with standard pulses and equipped with the signal processing device [Figure 9c] Electric power steering operation characteristics controlled with 1 / 2x pulses and equipped with the signal processing device [Figure 9d] Electric power steering operation characteristics controlled with 1 / 4x pulses and equipped with the signal processing device DETAILED DESCRIPTION OF EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0012] Next, an embodiment of the mechanical structure of the speed detection device in the eddy current type instrument according to the present invention will be specifically described with reference to the attached Figure 1, Figure 2, and Figure 3.

[0013] The eddy current type instrument C2 of the present embodiment is composed of a main shaft 21, a magnet rotor 22, an induction rotor 23, a pointer 24, a pointer shaft 25, a frame 26 and an outer housing 26o. The speed detection device W2 is composed of a circuit board 28 on which the magnetic detection element 27 is mounted, and a metal support member 29. The circuit board 28 is formed by integrally joining the circuit board 28a on which the magnetic detection element 27 is surface-mounted to the circuit board 28b via wiring, adhesion and soldering. This adopts a two-stage structure in view of the fine pitch of the connection wiring of the surface-mounted Hall IC 27 and the ease of board assembly. Naturally, it is also possible to implement this with a single printed board. The circuit board 28b is fixed to the support member 29 by tightening with screws 29i and nuts 29j. The screws 29i are soldered 28d after tightening. The nuts 29j are soldered 29d to the support member 29 to be integrated therewith. The board 28 is soldered 28c to the metal support member 29. The speed detection device W2 has a structure in which the metal support member 29 is clamped and fixed between the frame 26 and the outer housing 26o by screws 210.

[0014] The metal support member 29 is made of a copper sheet having a developed shape as shown in Figure 3, and has a three-dimensional structure formed by bending its edge portions. The bent edges are soldered 26h at the tangent lines with adjacent edges to achieve rigidity as a ribbed structure. The center hole of the support member 29 is structured to fit exactly into the portion supporting the main shaft at the center of the frame 26, and is aligned with the main shaft. In addition, the angle of the support member 29 relative to the frame 26 is uniquely determined by the two hole positions for the mounting screws 210.

[0015] The main shaft 21 transmits the rotation of the vehicle wheels or drive shaft, which is transmitted via a flexible cable (not shown), to the magnet rotor 22. The main shaft 21 is rotatably supported by the frame 26.

[0016] The magnetic rotor 22 consists of a magnet 22a and a soft magnetic holder 22b for the magnet 22a. The magnetic rotor 22 is fixed to the end of the main shaft 21.

[0017] The induction rotor 23 is a cup-shaped conductor. It is positioned with a small gap between it and the magnet 22a of the magnet rotor 22. The induction rotor 23 rotates due to the eddy current action generated by the rotation of the magnet rotor 22, and generates rotational torque proportional to the rotational speed of the magnet rotor 22. A pointer shaft 25 for mounting the pointer 24 is provided at the center of the induction rotor 23.

[0018] The pointer 24 is press-fitted and fixed to the end of the pointer shaft 25, and rotates together with the pointer shaft 25 mounted on the induction rotor 23 to display the vehicle's speed.

[0019] A plate 26c is mounted on the frame 26 and secured with screws. The pointer shaft 25 is supported by a bearing 213 on this plate and a lower bearing 21c located at the center of the upper end of the main shaft 21. The inner end of the whisker spring 211 is fixed to the pointer shaft 25, and its outer end is fixed to the plate 26c.

[0020] The frame 26 is made of a metal material such as aluminum, and a plate 6c is attached to its upper end. The frame 26 holds the various components such as the main shaft 21, the magnet rotor 22, and the induction rotor 23.

[0021] In this embodiment, the magnetic detection element 27 is positioned opposite the side surface of the induction rotor 23 and is fixed to a circuit board 28 that is fixed to a support member 29 so as to detect the magnetic flux of the magnet 22 that has leaked out after penetrating the induction rotor 23. Two of these combinations are installed with a 90-degree phase difference. The magnetic detection element 27 detects the change in the magnetic field accompanying the rotation of the magnet rotor 22, converts this change in the magnetic field into an electrical signal, and outputs this electrical signal to various control devices mounted on the vehicle via a signal processing device.

[0022] Furthermore, electronic components such as resistors and capacitors (not shown) that protect the magnetic detection element 27 from external noise may be mounted. The control equipment is connected via electrical wiring (not shown). The circuit board 28 is fixed to the support member 29 by screws 29i. In this case, the ground wire is connected to the external housing 26o through the screw portion and the support member 29, and power is supplied to the vehicle body. This not only eliminates the need for a ground wire within the narrow meter space but also enables highly reliable power supply.

[0023] The following describes an embodiment of the circuit configuration in the velocity detection device for the eddy current type instrument related to the present invention, with reference to Figures 4, 5, and 6.

[0024] This section describes the operation of the velocity detection device in an eddy current type instrument that generates twice the normal pulse rate by using two magnetic detection devices with a magnet pole pair of 1. The magnetic detection device in Figure 6 consists of two omnipolar Hall ICs (active Hi) from Figure 5, installed 90 degrees apart. As shown in the internal circuit of the Hall IC in Figure 4, the output of the IC is connected to an open drain.

[0025] In Figure 6, the output of this IC is a pulled-up FET transistor circuit, which switches OFF (resistance increases) when it approaches the magnetic poles (S, N), causing the output voltage to rise. As the S pole approaches the upper Hall IC Q1, it switches OFF (resistance increases) and the voltage rises. At this time, Q2, which is 90 degrees behind in phase, is still switched ON (resistance zero) and the voltage is zero. After the S pole passes in front of Q1, Q1 switches ON (resistance zero) and the output voltage becomes zero. Then, when the S pole comes in front of Q2, Q2 switches OFF (resistance increases) and the output voltage rises. After the S pole passes in front of Q2, Q2 switches ON (resistance zero) and the output voltage becomes zero. A similar process repeats for the N pole, and the voltage characteristics shown in the chart appear in each output circuit. By suppressing reverse current with a diode, the summed voltage waveform is obtained at the output. Therefore, a single-pole pair of magnet rotors can produce a signal of 4 pulses per rotation.

[0026] Back when cable-driven eddy current type instruments were common, it was typical for engine control and power steering control to generate two pulses per revolution. This was because the magnetic detection element was a reed switch, requiring a large span of the reed switch for magnetic detection. To achieve this span, it was necessary to use a single pole pair (S and N) at the end of the magnet rotor to ensure reliable operation of the reed switch. This time, by using one pole pair of magnets and installing two magnetic detection devices, it is possible to create a speed detection device in an eddy current type instrument that generates twice the usual number of pulses.

[0027] Hereinafter, embodiments of the signal processing device 30 in the eddy current type instrument according to the present invention will be described with reference to Figures 7, 8, and 9.

[0028] Figure 7 shows the circuit of the signal processing device 30. A buffer 32 removes surges and noise from the input signal, and a 1 / 2 frequency divider 31 is constructed using a flip-flop circuit. There are three stages of 1 / 2 frequency dividers 31 in total, allowing for the extraction of four types of signals. When a signal with 4 pulses per revolution is input, four types of signals can be obtained per revolution: 4, 2, 1, and 1 / 2. As mentioned above, the vehicle speed sensor signal that serves as the reference for the arithmetic control unit (ECU) is 2 pulses per revolution, but the output of the signal processing device 30 is converted to 2x, 1x, 1 / 2x, and 1 / 4x.

[0029] As shown in Figure 4 of Patent Document 3, in electric power steering, the amount of power steering assist changes depending on the vehicle speed. Therefore, by generating more pulses from the vehicle speed sensor than the original setting value of the arithmetic control unit (ECU) and then varying the number of pulses generated by the signal processing unit 30, the amount of power steering assist can be varied.

[0030] Figure 8 shows a configuration in which the vehicle speed detection device and the signal processing device 30 are incorporated into a typical electric power steering system. In electric power steering, the ignition signal indicates whether the ignition is ON, the engine signal indicates whether the vehicle is in operation, the steering torque is detected by the torque detector, and the vehicle speed is detected by the speed detection device. The signal processing device 30 is interposed in this vehicle speed signal path.

[0031] The Calculation Control Unit (ECU) calculates the amount of assist from torque and vehicle speed using the map shown in Figure 9b (2 pulses / REV) and drives the motor. If the toggle switch is set to 4 pulses per revolution and the vehicle speed signal is provided to the ECM, twice the number of pulses are provided to the ECM as needed. As shown in Figure 9a, the steering is light when turning, but once the vehicle starts moving, it becomes a heavier characteristic with less assist and a more direct feel. Conversely, setting it to 1 pulse / REV in Figure 9c or 1 / 2 pulse / REV in Figure 9d provides light torque performance across the entire range. The weight of the power steering can be varied according to the driver's preference and the situation.

[0032] As described above, by installing an aftermarket signal processing device, the driver can select the optimal power steering assist force according to the driving situation in stages. Since the increase and decrease of the vehicle speed signal are geometrically constant, vehicle speed sensitivity is maintained, and unlike pulse generators such as those described in Non-Patent Document 1, it is possible to handle everything from improved drivability at zero speed to stability at high speeds in a single mode without frequently changing settings. [Explanation of Symbols]

[0033] 21 Spindle 22 Magnet Rotor 23 Induction rotor 24 Guidelines 25 Pointer axis 26 Frame 27 Magnetic detection element 28 Circuit boards 29 Support member 30 Signal Processing Device 31 1 / 2 minute period 32 buffers 33 Changeover switch 34 Output Stages C2 Eddy current type instrument W2 Speed ​​Detection Device

Claims

1. A power steering system comprising a steering torque detection means that outputs a steering torque signal corresponding to the steering force applied by the driver to the steering member, and an aftermarket speed detection device that detects the vehicle speed and generates a signal with a number of pulses proportional to the detected vehicle speed, and a calculation control device that determines the amount of steering assist from the steering torque signal and the pulse signal proportional to the vehicle speed, characterized in that a signal processing device that reduces the vehicle speed pulse signal is additionally installed between the aftermarket speed detection device that generates a signal with a number of pulses proportional to the vehicle speed and the calculation control device that calculates the amount of steering assist of the power steering.

2. The power steering device according to claim 1 is characterized in that the configuration of the vehicle speed signal reduction device is an aftermarket signal processing device that divides the vehicle speed pulse frequency, the frequency divider has means for switching the frequency division rate, and it is possible to manually switch between no frequency division and the frequency division rate.

3. The aftermarket vehicle speed detection device of claim 1 detects changes in the rotational magnetic force of the magnetic rotor in an eddy current type speedometer, and is characterized by generating a signal of 4n pulses per rotation of the vehicle speed cable for a number of magnetic pole pairs n of the magnetic rotor.

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