JP2513328Y2 - Vehicle speed limiter for four-wheel steering vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a device for limiting the vehicle speed during four-wheel steering of a four-wheel steering vehicle.

(Prior Art) In a four-wheel steering vehicle, when the vehicle speed reaches a preset predetermined value, the vehicle speed limiting device is actuated to prevent the vehicle speed from further increasing in order to improve maneuverability during four-wheel steering. (See Japanese Utility Model Laid-Open No. 64-35181).

Since steerable turning is possible during four-wheel steering compared with normal two-wheel steering, the four-wheel steering during high-speed driving tends to cause unstable vehicle running characteristics, so the vehicle speed is limited to a fixed value during four-wheel steering. I am doing it.

(Problems to be solved by the invention) By the way, such a vehicle speed limiting device determines the vehicle speed based on the output of the vehicle speed sensor. However, if an abnormality or a failure occurs in the vehicle speed sensor, the vehicle speed limiting function is not activated. It causes trouble and causes a problem in terms of driving safety.

An object of the present invention is to provide a vehicle speed limiting device for a four-wheel steering vehicle, which determines abnormality of a vehicle speed sensor, and substitutes a function by a backup vehicle speed sensor in case of abnormality to enhance traveling safety.

Therefore, according to the present invention, as shown in FIG. 1, a front wheel steering mechanism and a rear wheel steering mechanism, and a rear wheel which selectively and reversibly adjusts the steering direction and the steering amount of the front wheel steering mechanism. In a vehicle speed limiting device for a four-wheel steering vehicle equipped with a mode switching mechanism that transmits to the steering mechanism and means for limiting the vehicle speed so that the vehicle speed does not exceed a set value during four-wheel steering, a main vehicle speed sensor 90 and a backup vehicle speed are provided. The output of the sensor 91 and the output of the backup vehicle speed sensor 91 are compared with the vehicle speed values of two high and low corresponding to the vehicle speed limit and the vehicle speed limit, and the output of the main vehicle speed sensor 90 and the output of the comparison means. A main vehicle speed sensor and a judging means 94 for judging an abnormality of the main vehicle speed sensor based on the comparison, and for judging an abnormality of the comparing means on the basis of comparison between outputs corresponding to two high and low vehicle speed values of the comparing means. And the comparing means are both normal, based on the output of the main vehicle speed sensor, and when the main vehicle speed sensor is abnormal and only the comparing means is normal, based on the output of the comparing means, the control means 96 for operating the vehicle speed limiting means 95. With.

(Operation) By comparing the output of the main vehicle speed sensor and the output of the comparison means of the backup vehicle speed sensor, the abnormality of the main vehicle speed sensor is determined. Further, the abnormality of the comparison means can be determined from the contradiction between the two comparison results. As the backup vehicle speed sensor and the comparison means, for example, a simple structure which is turned on / off with the comparison reference vehicle speed as a boundary and which is unlikely to cause a failure can be applied, so that the probability that the comparison means causes an abnormality can be sufficiently reduced. Therefore, the abnormality determination result of the main vehicle speed sensor is extremely reliable.

When it is determined that the main vehicle speed sensor is abnormal, it is determined whether the vehicle speed is zero or whether the vehicle speed reaches the limit vehicle speed by the two outputs of the comparison means of the backup vehicle speed sensor.

Therefore, even when there is an abnormality in the main vehicle speed sensor, the output of the comparison means of the backup vehicle speed sensor
It is possible to limit the vehicle speed during four-wheel steering and determine whether the vehicle speed is zero.

(Example) Hereinafter, an example of the present invention will be described.

In FIG. 2, reference numeral 25 is a steering handle, 26 is a gear box which operates in response to rotation of the steering handle 25, and steers the front wheels 21 via a link 29 and a steering linkage 23. The gear box 26 functions as a so-called power steering actuator, but may be a manual steering gear.

Reference numeral 18 denotes a mode switching gear box, which controls the steering direction of the steering handle 25 transmitted via a link 27 by selectively adjusting the steering amount via a rear wheel steering actuator 28.
To communicate.

The mode switching gearbox 18 transmits the steering amount of the front wheels in the same phase (same direction), transmits the same in the opposite phase (reverse direction), or interrupts the transmission to the rear wheels.
By operating the in-phase mode switching valve 15 and the anti-phase mode switching valve 16, switching between in-phase and anti-phase can be selected.
When both valves 15 and 16 are deactivated, it is possible to switch to two-wheel steering. Note that these switching can be performed when the vehicle is stopped, that is, when the vehicle speed is zero.

The output of the mode switching gearbox 18 is transmitted to the rear-wheel steering actuator 28 via the link rod 30, and the rear-wheel steering actuator 28 selectively receives hydraulic pressure as the link rod 30 moves to operate, The rear wheel 22 turns from 31 via the steering linkage 24. The rear wheel steering actuator 28 has the same configuration as a known power steering actuator, and generates a steering output according to the steering direction and the steering amount.

Reference numeral 1 is an air cylinder that locks the rear wheels to prevent rolling of the rear wheels during two-wheel steering and releases the rear wheels during four-wheel steering. The rear-wheel lock state is detected by two lock sensors 6 and 7. It Air cylinder 1 is a lock release valve
Operation is controlled via 14. Therefore, the transition from two-wheel steering to four-wheel steering is performed after it is detected that the rear wheels are completely unlocked.

Reference numeral 8 is a pressure sensor that detects whether or not an appropriate air pressure is being supplied from the air supply source. A snake angle sensor 2 for detecting the snake angle on the rear wheel side is provided so that the direction and the snake angle of the rear wheel steering can be determined during four-wheel steering.

Further, position sensors 3, 4, and 5 are provided to detect whether the mode switching gear box 18 is in the in-phase position, the two-wheel steering position, or the out-of-phase position. These detection results are displayed on the display unit 41, and the driver can determine in which mode the vehicle is traveling.

Further, in order to enhance the traveling safety during four-wheel steering, a vehicle speed limiting air cylinder 17 is provided as a mechanism for limiting the vehicle speed, and this operation is controlled by the speed limiting valve 19. A main vehicle speed sensor 10 for detecting the vehicle speed and a backup vehicle speed sensor 11 are provided, and when a predetermined vehicle speed is reached during four-wheel steering based on these, a vehicle speed limiting air cylinder 17 is provided to prevent the vehicle speed from further increasing. Activate. In other words, during four-wheel steering, a sharper turn is possible compared to during two-wheel steering, so the vehicle speed must be set in order to prevent the steering handle 25 from being inadvertently turned too much when driving at high speeds, which could impair steering control. For example, the vehicle speed is automatically limited so that it does not exceed 25 km / h.

Each of these controls is carried out by the control unit 40 composed of a microcomputer, etc., and for this reason, the signals of the respective sensors are inputted to the control unit 40, and in-phase, anti-phase and two-wheel steering control instructions are given. Is performed through the display unit 41.

By the way, the gist of the present invention is that in the vehicle speed limiting mechanism, when an abnormality occurs in the main vehicle speed sensor 10 or the backup vehicle speed sensor 11, it is detected and a normal sensor is used as a vehicle speed detection function to perform four-wheel steering. It is to always operate the limited vehicle speed mechanism of (1) accurately to enable safe driving.

Therefore, as shown in FIG. 3, the output of the backup vehicle speed sensor 11 is converted into a voltage corresponding to the frequency by the F / V converter 50 and set by the two low speed side and high speed side comparators 51 and 52, respectively. Value (for example, vehicle speed 3
The set values corresponding to km / h and 25 km / h) are compared. Each of the comparators 51 and 52 outputs a high level signal "H" when the input value is larger than the set value.

The control unit 40 uses these main vehicle speed sensors 10
As shown in the flow chart of FIG. 4, it is determined whether or not an abnormality or failure has occurred in the vehicle speed sensor based on the output of the main vehicle speed sensor 10 and the output of the two comparators 51 and 52. The operation of the vehicle speed limiting mechanism that is controlled on the basis of the output of comparators 51 and 52 that determine the output of the backup vehicle speed sensor 11 when an abnormality occurs in the main vehicle speed sensor 10 is performed on behalf of the vehicle. .

These will be specifically described according to the flowchart.

First, in step 61, the main vehicle speed sensor (vehicle speed sensor #
The output V of 1) and the outputs VL and VH of the low speed side comparator and the high speed side comparator are read, and it is judged whether the vehicle speed V = 0 or not based on whether or not the V = 0 flag is set (step 6).
2) If the vehicle speed is zero, check in step 64 whether the backup vehicle speed sensor (vehicle speed sensor # 2) is abnormal.
Judge from the NG flag set.

If not abnormal, comparator output at that time VL =
If it is "H", and if so, it is determined that an abnormality has occurred in the vehicle speed sensor # 1, and the NG (abnormality) flag is set in step 66.

That is, although the vehicle speed sensor # 2 is normal and the low-speed side comparator output outputs a high level signal, the vehicle speed sensor # 1 detects zero speed. This is because it can be determined that the abnormality is occurring.

On the other hand, when VL = H is not satisfied, the vehicle speed is zero, so in step 67, the NG flag of the vehicle speed sensor # 1 is cleared and the vehicle speed is determined to be normal.

In step 63, the output of the vehicle speed sensor # 1 is differentiated to detect the acceleration.

When the output of vehicle speed sensor # 1 is normal, check whether the outputs VL and VH of both comparators are "H",
If there is no output on the low speed side but there is output on the high speed side, it is determined that an abnormality has occurred in the vehicle speed sensor # 2, and the NG flag of the vehicle speed sensor # 2 is set (step
68-70).

Next, it is checked again whether the NG flag of the vehicle speed sensor # 1 is set, whether the flag of V = 0 is set further, and whether the vehicle speed is the predetermined value V ₃ or more, and the vehicle speed sensor # 1 is When VL and VH are both "H" when the vehicle speed is normal and the vehicle speed is higher than zero, it is judged that the vehicle speed sensor # 2 is normal and the NG flag is cleared (steps 71 to 76).

On the other hand, when neither VL nor VH is being output, it is determined that the vehicle speed sensor # 2 is still abnormal, and the NG flag of the vehicle speed sensor # 2 is set (step 77).

Next, when the NG flag of the vehicle speed sensor # 1 is set and the NG flag of the vehicle speed sensor # 2 is not set (steps 78, 79), the vehicle speed limiting mechanism is based on the normal output of the vehicle speed sensor # 2. Operate. Therefore, in step 80, look at the output VH of the high-speed side comparator and see that this is “H”.
Switch to, the vehicle speed is considered to have reached the set value (for example, 25km / h), the vehicle speed limiting mechanism is activated, and when there is no output, the vehicle speed limiting mechanism is left inactive (step 81, 82). However, when the vehicle speed sensor # 1 is normal, based on the sensor output, vehicle speed activates the vehicle speed limiting mechanism to perform the vehicle speed limit when it exceeds a predetermined limit speed V ₃ (step 78,83～85 ).

In this way, the abnormality of the sensor is judged while observing the outputs of the vehicle speed sensor # 1 and the sensor # 2, and when the abnormality occurs in the main vehicle speed sensor # 1, the comparator output VH of the vehicle speed sensor # 2 to be backed up, Since the operation is switched so as to control the operation of the vehicle speed limiting mechanism based on VL, appropriate control can always be performed and traveling safety during four-wheel steering can be ensured.

(Effect of the Invention) As described above, according to the present invention, even when an abnormality occurs in the main vehicle speed sensor, the vehicle speed limiting means can be correctly operated based on the output of the backup vehicle speed sensor, and traveling safety during four-wheel steering. It is possible to further improve the sex. Further, since the output of the backup vehicle speed sensor is configured to be taken out as two outputs by the comparison means, in addition to being able to determine the vehicle speed limit speed and the stopped state,
The configuration can be simplified, and therefore reliability can be further improved and cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a configuration diagram showing an embodiment of the present invention, FIG. 3 is a flock diagram, and FIG. 4 is a control operation. It is a flowchart. 10 …… Main vehicle speed sensor, 11 …… Backup vehicle speed sensor, 17 …… Vehicle speed limiting cylinder, 18 …… Mode switching gearbox, 21 …… Front wheel, 22 …… Rear wheel, 26 …… Gearbox, 28 …… Rear Wheel steering actuator, 40 ... Control unit.

Claims (1)

(57) [Scope of utility model registration request] 1. A front wheel steering mechanism and a rear wheel steering mechanism, a mode switching mechanism for selectively and reversibly transmitting a steering direction and a steering amount of the front wheel steering mechanism to a rear wheel steering mechanism, and a vehicle speed is set during four-wheel steering. In a vehicle speed limiting device for a four-wheel steering vehicle equipped with a means for limiting the vehicle speed so as not to exceed the value, the output of the main vehicle speed sensor, the backup vehicle speed sensor, and the backup vehicle speed sensor correspond to the vehicle speed limit and the vehicle stop state, respectively. And comparing the output of the main vehicle speed sensor with the output of the comparison means to determine whether the main vehicle speed sensor is abnormal, and to cope with the two vehicle speed values of high and low. Based on the output of the main vehicle speed sensor when both the main vehicle speed sensor and the comparison means are normal, Only the main speed sensor is abnormal and comparison means on the basis of the output of said comparator means when the normal, the vehicle speed limiting device of a four-wheel steering vehicle, characterized in that it comprises a control device for activating the vehicle speed limiting means.