JPH0476461A - Yaw rate sensor - Google Patents

Abstract

PURPOSE:To shorten an unstable time of sensor output directly after beginning to run to improve reliability of control of a vehicle by detecting the condition of a vehicle directly before beginning to run, and providing a current supply control part to previously begin current supply to a yaw rate sensor. CONSTITUTION:A measuring part 1 is connected to a keyless electric source line to supply current by inserting a key to the key cylinder of a vehicle, and the power of a control unit part 2 is taken from an ignition power source IG line. Because current is supplied to the measuring part 1 by inserting the key to the key cylinder, the measuring part 1 can be started at least a few seconds before beginning to run of the vehicle. Hereby, the unstable time of a sensor directly after beginning to run can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a yaw rate sensor for detecting a yaw rate as a parameter for vehicle control.

(Prior art) In a four-wheel steering type (i.e. 4WS) vehicle in which not only the front wheels but also the rear wheels are steered by the steering operation of the steering wheel, when driving at high speed, the steering wheel is steered in the same direction as the steering wheel operation direction. The rear wheels are steered in the same phase), and the amount of steering is suppressed to maintain vehicle stability, while when parking, etc., the rear wheels are steered in the opposite direction to the direction in which the steered wheels are operated (inverse phase). ), and it is common practice to increase the amount of steering so that the vehicle can turn in a sufficiently small radius. This control is generally performed using two parameters: vehicle speed and steering angle.

By the way, when a vehicle turns, the angular velocity caused by the turning is directly detected and the detected value is added to the parameters for calculating the control amount for rear wheel steering, thereby enabling more responsive control. Additionally, when the vehicle sways left or right due to external lateral forces such as crosswinds while driving, the system detects the sway and controls the steering of the rear wheels to counteract the sway to keep the vehicle running straight. It becomes possible to do so. Therefore, for example, as described in Japanese Patent Application Laid-Open No. 57-44568, the turning or swinging of the vehicle is directly calculated by a yaw rate sensor, and the turning angle of the 4WS is changed according to the yaw L/-t. is proposed.

(Problems to be Solved by the Invention) A gyro is a typical sensor for detecting vibration of a movable object, but it is not practical to use such an expensive sensor in a vehicle control system. Therefore, when using the yaw rate as a long sword signal for vehicle 4WS control, etc., the yaw rate sensor may be a tuning fork type or vibrator type angular velocity sensor, which is used in a system to prevent image shake of a video camera. It is possible to repurpose it.

The above-mentioned angular velocity sensor, for example, connects a vibration unit in which a drive element and a detection element made of piezoelectric bimorph are orthogonally joined together, and a vibration unit in which a monitor element and a detection element are orthogonally joined together by a connecting plate, and connects this connecting plate at a single point. By applying a constant drive signal to one drive element, the entire tuning fork resonates through the connecting plate, and when angular velocity is applied to this, the force generated perpendicular to the plane of the piezoelectric bimorph is converted into a voltage. The sensor output is then converted into a sensor output.

However, when attempting to use such an angular velocity sensor in a vehicle control system, the following problem occurs. That is, this type of angular velocity sensor does not immediately output a stable detection signal when energized, but there is a startup time, and detection accuracy is usually not guaranteed until a certain period of time has elapsed. The period during which this detection accuracy is not guaranteed may be a long time unit if high accuracy is required.

A yaw rate sensor used for vehicle control does not require such high accuracy as to require a start-up time in units of hours as described above.
The zero point cannot be recognized until about 2 seconds have passed. However, in the case of yaw rate sensors for vehicles, the conventional way of thinking is that the energization of the yaw rate sensor is started in conjunction with the ignition switch like other control circuits, so the output of the yaw rate sensor is unstable. This causes a problem in that the reliability of the control cannot be maintained because vehicle control is started without any change. For example, 4WS
In the case of control, when the ignition switch is turned on and the yaw rate sensor starts to be energized, the way the car turns will differ depending on whether you start the engine and put it in the garage immediately or if you put it in the garage after a while. In addition, when the engine is started and the vehicle starts moving immediately, the turning angle becomes uncertain.

The present invention has been made in view of the above problems, and an object of the present invention is to shorten the period of instability of the yaw rate sensor output immediately after the start of vehicle operation, and to improve the reliability of vehicle control.

(Means for Solving the Problems) The present invention starts the yaw rate sensor early in anticipation of the period during which the sensor output is unstable, thereby reducing the period of unstable output as much as possible after the start of vehicle operation. The configuration includes a yaw rate sensor that detects left and right deflection with respect to the direction of travel of the vehicle and outputs it as a parameter for vehicle control; The present invention is characterized in that it further includes an energization control section that receives the output of the state detection means and starts energization of the yaw rate sensor in advance immediately before the start of operation of the vehicle.

In the above-mentioned means for detecting a state immediately before the start of operation, a key insertion detecting means for detecting insertion of a key into a key cylinder of a vehicle can be used.

Furthermore, as the means for detecting the state immediately before the start of entrainment, door open detecting means for detecting the opening operation of the door of the vehicle can also be used.

(Operation) When the state immediately before the start of operation of the vehicle is detected by the state immediately before the start of operation of the vehicle, the energization control section is activated in response to the detection signal, and the energization to the yaw rate sensor is started. Then, the sensor output stabilizes to some extent by the time the vehicle actually starts operating.

Therefore, the period of unstable output after the start of operation is shortened.

When a key insertion detection means is used as a means for detecting immediately before the start of operation, it usually takes several seconds after the key is inserted into the key cylinder until the engine is started and the vehicle starts operating, and during this time the yaw rate sensor is activated. The output is stabilized to the extent that there is almost no problem.

Furthermore, when door open detection means is used as the means for detecting immediately before the start of operation, the time until the start of vehicle operation becomes even longer, and the stabilization of the sensor output becomes more reliable.

(Embodiment) FIG. 1 is an overall system diagram of an embodiment of the present invention. In the figure, reference numeral 1 denotes a measuring section constituted by a tuning fork type angular velocity sensor which is known per se, and 2 denotes a control unit section connected to the measuring section.These measuring section 1 and control unit section 2 constitute a yaw rate sensor. Ru.

The angular velocity sensor constituting the measurement section 1 is known per se as described above, and includes a vibration unit in which a driving element and a sensing element made of piezoelectric bimorph are orthogonally connected, and a monitor element and a sensing element are orthogonally connected. The vibration unit is connected with a connecting plate, and this connecting plate is supported at one point to form a tuning fork structure, and a constant drive signal is applied to one drive element to cause the entire tuning fork to resonate. By mounting it vertically on a vehicle, when angular velocity is applied around the vertical axis, a voltage corresponding to the direction and magnitude of the angular velocity is extracted as a yaw rate output (ψ output).

The power source of the measurement unit 1 is a 5V power source 3 subtracted from a battery power source (12V). On the other hand, the control unit section 2 includes a CPU 4, two A/D converters 5.6,
It is equipped with a power line 7. The yaw rate output taken out from the measuring section 1 is input to the CPU 4 via one A/D converter 5. In addition, the power supply voltage of the measurement unit l is a reference output (V
ref output), which is then output to another A/
The signal is input to the CPU 4 via the D converter 6.

The measurement part above! The voltage corresponding to the angular velocity ("/s) when the vehicle turns or swings left and right is extracted as the yaw rate output. Here, the sensor power supply voltage is 5
As (2), half of 2.5V is set as the reference voltage. When the yaw rate output is higher than this reference voltage, it is determined that the yaw movement is to the right in the direction of travel.
When the yaw rate output is lower than the reference voltage, it is determined that the yaw movement is to the left. Then, a yaw rate (φ) corresponding to the difference from the reference voltage is output as a signal indicating the direction and angular velocity of the deflection. Further, the reference voltage is adjusted so as to always have an accurate zero point in accordance with fluctuations in the power supply voltage.

The CPU also calculates the control amount of the rear wheel turning angle in the 4WS control using the yaw rate (ψ) detected as described above, the vehicle speed and the steering angle that are separately input as parameters. This control amount is set so that when the yaw rate (ψ) is large, the steering angle increases toward the in-phase side, and when the steering angle is large, the steering angle increases toward the opposite phase side, and vehicle speed is added to this as a parameter. When the vehicle speed is high, the control amount is calculated with priority given to the yaw rate (φ), and when the vehicle speed is low, the control amount is calculated with priority given to the steering angle. However, in reality, the direction and angle of rear wheel steering are determined by the map.

Then, a control signal is output to an actuator for steering the rear wheels, and the rear wheels are steered by a set amount.

FIG. 2 shows the configuration of the power supply circuit of the measuring section 1 and the control unit section 2 in this embodiment. As seen in this figure, the measuring section 1 is connected to a keyless power supply line. On the other hand, the power supply for the control unit section 2 which receives the output signal of the measurement section 1, calculates the yaw rate, and performs 4WS control is taken from an IG (ignition) power supply line. Here, the keyless power line is a power line that is energized by inserting a key into a key cylinder of a vehicle. By using this keyless power supply line as a power source for the measuring section 1, it is possible to start activating the measuring section at least a few seconds before the start of vehicle operation. As a result, as shown in the time chart of Fig. 3, the power of the measuring section l is turned on.
The period from when 4WS control starts (to
), the sensor output stabilizes to a certain extent, and the sensor output (zero point) when the angular velocity is zero can be recognized with an accuracy that does not pose any practical problem.

4(a), (b), and (c) are a plan view, a side view, and a longitudinal cross-sectional view (C-C section Figure).

This keyless switch 10 includes a box-shaped switch case 11 that opens upward, and a cover 12 that is fitted into the upper opening.
Inside the main body case constituted by 2, there are terminal plates 15.16 connected to two conductive wires 13.I4 extending outside, and two mounting plates 17.16 corresponding to the terminal plates 15.16. A slider 19 is provided which holds the slider 18 and is movable up and down.

2. The two terminal plates 15 and 16 are arranged parallel to each other with an interval between them, and are fixed to the center of the switch case If by screws 20 and 20, respectively. The slider +9 is disposed on one end of the slider 19, and the contact plates 17.18 are attached to two horizontal holes 21.2+ opening on the surface of the slider 19 on the terminal plate 1516 side through contact springs 22, respectively. ing.

In addition, the slider 9 can be freely projected by a predetermined amount by sliding through the lower end or the hole 11a at the bottom of the switch case 1, and a return spring 23 is installed between the upper end and the cover 2. It is constantly biased downward.

As shown in FIG. 5, the key cylinder 30 of the vehicle is provided with a slide shutter 32 that is lifted upward by the key 31 when the key 31 is inserted. The keyless switch IO is provided so that the keyless switch IO is in contact with the keyless switch IO. When the key 31 is removed as shown by the imaginary line on the right side of FIG.
The slider 19 is in the position shown in FIG. 4(c), and the contact plate 17.18 is held in a position where it does not come into contact with the terminal plate 15.16. Then, at the position where the key 31 is inserted to the solid line position in FIG. 5, the slide shutter 32 is lifted and the slider 19 is moved upward.
The two contact plates 17.18 are in contact with the corresponding terminal plates 15.16, and current is passed between the two terminal plates 15.16 via the contact plates 17.18 and the slider +9.

In the above embodiment, the insertion of the key into the key cylinder is detected and the energization to the measuring section of the yaw rate sensor is started. A well-known door switch may be used as the detection switch to start energizing the measuring section of the yaw rate sensor when the vehicle door is opened. Further, the ACCm source line that supplies power to a radio or the like can also be used as a power source for a yaw rate sensor.

(Effects of the Invention) Since the present invention is configured as described above, by activating the yaw rate sensor prior to the start of vehicle operation, it is possible to shorten the period of instability of the sensor output immediately after the start of operation. Control using the yaw rate can be made highly reliable immediately after the start of vehicle operation.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a power supply circuit diagram of the embodiment, FIG. 3 is a control characteristic diagram of the embodiment, and FIGS. 4(a) and (b). (c) is a plan view, a side view, and a vertical cross-sectional view (C-C cross-sectional view) of the keyless switch used in the same example;
The figure is an explanatory diagram of the arrangement structure and operation of the keyless switch. 1. Measurement section, 2. Control unit section, 3. Power supply, 5.
,6・A/D converter, lO keyless switch, 30. Kino Linda, 31 key, 32 Ni slide shutter

Claims (3)

[Claims] (1) In a yaw rate sensor that detects left and right deflection with respect to the vehicle traveling direction and outputs it as a parameter for vehicle control, there is a state immediately before the start of operation detection means for detecting a state immediately before the start of operation of the vehicle, and an output of the state immediately before the start of operation detection means. and an energization control unit that starts energizing the yaw rate sensor in advance immediately before the start of operation of the vehicle. (2) The yaw rate sensor according to claim 1, wherein the means for detecting the state immediately before the start of operation is a key insertion detecting means for detecting insertion of a key into the key cylinder of the vehicle. (3) The yaw rate sensor according to claim 1, wherein the means for detecting a state immediately before the start of operation is a door open detecting means for detecting an opening operation of a door of the vehicle.