JP2002005949A - Yaw acceleration detector for industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yaw acceleration detector using no yaw rate sensor and applicable to an industrial vehicle frequently using an abrupt change of direction such as switchback. SOLUTION: This yaw acceleration detector is equipped with a yaw rate computing means 30 for finding a yaw rate by computation from a detected vehicle speed and a turning radius, and a yaw acceleration computing means 30 for finding a yaw acceleration by computation from the yaw rate found by the yaw rate computing means, and characterized in that, when a yaw acceleration is found, a yaw rate is given a code differing with the progressing direction detected by a progressing direction determining means. This configuration dispenses with any yaw rate sensor. Since the codes are sorted by progressing directions, an accurate yaw acceleration is acquired even for switchback during a turn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial vehicle such as a forklift, and more particularly to an apparatus for detecting a rate of change of a yaw rate with respect to time, that is, a yaw acceleration.

[0002]

2. Description of the Related Art In an industrial vehicle such as a forklift, a yaw acceleration is detected, and various controls such as cargo handling control and traveling control are performed based on the detected value.

[0003] For example, in a counter-type forklift (four-wheel type forklift), a rear axle supporting a rear wheel is swingably mounted on a machine base in order to achieve vehicle stability during traveling. If the rear axle is merely swingably supported, the machine base may be tilted by a lateral force due to centrifugal force during turning. Therefore, conventionally, the yaw acceleration is obtained, and when the absolute value exceeds a predetermined value, it is determined that the lateral force is considerably large,
The technology that regulates the swing of the rear axle is adopted.
Thereby, the inclination of the machine base at the time of turning is suppressed to be small, and it becomes possible to turn at a stable posture.

As means for detecting the yaw acceleration, means for obtaining the yaw acceleration using a yaw rate sensor is generally used. For example, as described in Japanese Patent Laid-Open No. Hei 10-287116, the yaw acceleration is determined from the steering angle and the vehicle speed of the steered wheels. There is also a method of calculating a yaw rate and obtaining a yaw acceleration from the yaw rate. Specifically, in the case of an engine-type counter-type forklift, the vehicle speed V at the center point between the front wheels is estimated from the rotation of the differential ring gear connected to the front wheels, and the steering angle of the rear wheels that are the steered wheels is calculated. The turning radius r of the vehicle is estimated, and the yaw rate Y is obtained from the equation Y = V / r. Then, the yaw acceleration is obtained by differentiating this equation with time. According to this method, there is an advantage that a yaw rate sensor becomes unnecessary.

[0005]

However, at present, the yaw acceleration detecting means described in Japanese Patent Application Laid-Open No. H10-287116 is not widely and generally employed.
In particular, in a vehicle type such as a battery-type reach forklift that frequently and continuously changes its direction from forward to backward or from reverse to forward (so-called switchback) during turning on the spot, the yaw acceleration detecting means is used as it is. Application was not preferred.

SUMMARY OF THE INVENTION An object of the present invention is to provide a yaw acceleration detecting device which can be applied to an industrial vehicle that frequently uses a change of direction such as switchback and does not use a yaw rate sensor.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted intensive studies and as a result, disclosed in Japanese Patent Laid-Open No. 10-287.
No. 116 discloses a yaw acceleration detecting means,
It was noted that no sudden change of direction, such as switchback, was taken into account. This is due to the fact that the yaw acceleration detecting means has been invented for an engine-type counter forklift. This is because, in such a vehicle type, switchback while turning is not performed, and there is no problem that it is necessary to distinguish between forward and reverse when detecting the yaw acceleration.

Here, considering the case where the above-described means is applied as it is to a battery-type reach forklift in which switchback is frequently used, the yaw rate is positive or negative even if the switchback is performed while turning left or right. Is left as it is. In such a case, as will be understood from FIG. 4A, the sign of the yaw acceleration changes through zero after the switchback.
For this reason, if the control for restricting the swing of the axle is performed in accordance with the magnitude of the absolute value of the yaw acceleration, the swing regulation and the release are repeated, and the running may be unstable.

A yaw acceleration detecting device according to the present invention has been made based on the above knowledge, and as described in claim 1, vehicle speed detecting means for detecting a vehicle speed at a predetermined point on a machine base, A turning radius detecting means for detecting a turning radius of the vehicle, a yaw rate calculating means for calculating a yaw rate from the vehicle speed detected by the vehicle speed detecting means and a turning radius detected by the turning radius detecting means, and a yaw rate calculating means. A yaw acceleration calculating means for calculating a yaw acceleration from the yaw rate and a traveling direction discriminating means for discriminating whether the traveling direction is forward or backward are provided. The yaw acceleration is obtained.

In this configuration, the yaw rate and the yaw acceleration can be detected without using a yaw rate sensor. Also, since the sign of the yaw rate is switched for each traveling direction, a graph of the yaw acceleration detected at the time of switchback during turning is as shown in FIG. 4B.
Therefore, in an industrial vehicle such as a battery-type reach forklift, when the swing of the axle or the wheel is regulated at the time of switchback during turning, the state is maintained and stable running is ensured.

According to a second aspect of the present invention, in the case where the industrial vehicle is a reach forklift having a front wheel which is a driven wheel and a rear wheel which is a steering wheel and a driving wheel, the vehicle speed detecting means may be used. A rotation speed sensor for detecting the rotation speed of the rear wheel, and a means for determining the vehicle speed based on a signal from the rotation speed sensor. The turning radius detection means includes a steering angle for detecting the steering angle of the rear wheel. It is characterized by comprising a sensor and a means for determining a turning radius based on a signal from a steering angle sensor.

In this configuration, the vehicle speed is detected from the rotation speed of the rear wheel, and the turning radius is detected from the steering angle of the rear wheel. In a rear forklift driven by one rear wheel, the vehicle speed can be reliably obtained from the rotation speed of the rear wheels. Also, since the turning center is on the rotation axis of the front wheel, the turning radius of the rear wheel is larger than the turning radius of the center point between the front wheels.
Therefore, the yaw rate, and thus the yaw acceleration, can be obtained with high accuracy. On the other hand, Japanese Patent Laid-Open No.
In the conventional yaw acceleration detecting means described in Japanese Patent Application Publication No. 287116, in an engine-type counter-type forklift, a vehicle speed at a center point between front wheels is obtained from rotation of a differential ring gear connected to front wheels, and steering of rear wheels is performed. The turning radius for the center point between the front wheels is obtained from the corner. However, as the turning radius decreases, the error in the detected value of the vehicle speed increases, and the error in the calculated yaw rate and yaw acceleration also increases. In the invention according to claim 2, such a problem is solved.

In the present specification, the number of rotations of the rear wheel includes the number of rotations of the output shaft of the drive source of the rear wheel and the number of rotations of the rotation shaft of the transmission mechanism.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals. In the following description, the terms “front”, “rear”, “left”, “right” and the like are used with the forward direction of the vehicle defined as “front”.

The yaw acceleration detecting device according to the present embodiment is shown in FIG.
Is applied to a battery type reach forklift 10 as an industrial vehicle schematically shown in FIG.

In the reach forklift 10 shown in FIG. 1, a front wheel 12 is disposed at a tip end of a pair of left and right reach legs 18 extending forward from a lower portion of a machine base 16. These front wheels 12 are driven wheels. In addition, a rear wheel 14 as a driving wheel also serving as a steering wheel is arranged at the rear of the machine base 16 so as to be offset slightly to the left in the vehicle width direction. Further, on the right side of the rear wheel 14, an auxiliary wheel (caster wheel) 20 that is paired with the rear wheel 14 on the left and right is provided.

The rear wheel 14 is attached to an output shaft of a gear box 24 for transmitting the torque of a drive motor 22 as a drive source. The gear box 24 is rotatably supported by a support 26 attached to the machine base 16. By rotating a steering wheel (not shown), the gear box 24 rotates with respect to the support 26. As a result, the rear wheels 14 are steered.

In the vicinity of a gear wheel (not shown) provided above the gear box 24, a detection signal corresponding to the steering angle of the rear wheel 14 (the angle formed by the rotation surface of the rear wheel 14 with respect to the straight traveling direction) is output. A steering angle sensor 28 is provided. Various types of steering angle sensors 28 can be used. For example, the steering angle sensor 28 detects the rotation speed of the gear wheel, outputs a detection signal having an amplitude number proportional to the rotation speed, and outputs a phase difference for each steering direction. Hall element / magnetic sensor capable of outputting different kinds of detection signals are preferable. An output signal from the steering angle sensor 28 is input to the controller 30 and used for various controls.

The rotational direction of the drive motor 22 is switched by tilting a forward / backward switching lever 32 provided in the driver's seat. That is, the forward / reverse switching lever 32 is provided with a tilt direction detecting means 34 such as a switch for detecting the tilt direction or a potentiometer, and the controller 30 controls the drive motor 22 based on a detection signal from the tilt direction detecting means 34. Of the forklift 10 is switched between forward and reverse.

A brake disk (not shown) that rotates integrally with the drive shaft is provided above the drive motor 22.
A vehicle speed sensor (rotation speed sensor) 36 for detecting the rotation speed of the vehicle and generating a signal corresponding to the vehicle speed is provided. As the vehicle speed sensor 36, a hall capable of detecting the number of rotations of the brake disc and outputting a detection signal of an amplitude number proportional to the number of rotations, and outputting a type of detection signal having a different phase difference for each rotation direction. An element / magnetic sensor is preferred, but not limited to this. Of course, the vehicle speed sensor 36
May detect the rotation speed of the rear wheel 14 or the rotation speed of the rotation shaft of the transmission mechanism in the gear box 24. The output signal of the vehicle speed sensor 36 is also input to the controller 30 and used for various controls.

A support 26 supporting the gear box 24 is swingably attached to the machine base 16, and a suspension spring (not shown) and a damper cylinder 38 provide an appropriate ground pressure and cushioning for the rear wheel 14. The action is ensured. When the flow path of the hydraulic oil flowing through the damper cylinder 38 is shut off by the shutoff valve 40 under the control of the controller 30, the damper cylinder 4
Since the expansion and contraction of the zero is restricted, the swing of the support 26 is locked.

The above configuration is well known.
The yaw acceleration detecting device according to the present invention in the reach forklift 10 having the above configuration mainly includes a steering angle sensor 28, a vehicle speed sensor 36, and a controller 30 to which these sensors 28 and 36 are connected.

The controller 30 basically has a CPU
(Central processing unit) 42, RAM (read / write memory) 4
4 and a ROM (read only memory) 46. The microcomputer is capable of obtaining yaw acceleration in accordance with a program stored in the ROM 46 based on signals from the steering angle sensor 28 and the vehicle speed sensor 36.

FIG. 2 is a flowchart showing the program written in the ROM 46 of the controller 30. Here, the operation of the yaw acceleration detecting device according to the present invention will be described with reference to FIG.

When the program starts, first, a signal from the vehicle speed sensor 36 is read (step 10).
0), a vehicle speed (speed at the center point of the ground contact surface of the rear wheel 14) V corresponding to this signal is obtained by calculation (step 102). Further, since the vehicle speed sensor 36 emits signals having different phases depending on the rotation direction of the brake disk, which is the subject, the traveling direction is also determined by the signal from the vehicle speed sensor 36 (step 104).

Next, at step 106, the signal from the steering angle sensor 28 is read, and the steering angle θ is obtained by calculation (step 108). Here, as shown in FIG. 3, when the rear wheel 14 is steered clockwise with reference to the rotation plane CL of the rear wheel 14 in the straight traveling state, the steering angle θ takes a positive value, and the rear wheel 14 When the steering is performed in the counterclockwise direction, the steering angle θ assumes a negative value. In this case, when the steering angle θ is zero, it is determined that the vehicle is traveling straight (step 11).
0), the yaw rate is set to zero. This value is stored in the RAM as the yaw rate Y _R (step 112), and the process returns to step 100.

On the other hand, if the steering angle θ is not zero, it is determined that the vehicle is turning, and the turning direction is determined (steps 114, 116, 118). And step 120
Determines the turning radius r. Reach forklift 1
When the vehicle turns zero, the center of rotation is the rotation axis of the front wheel 12 and the rear wheel 14.
When the steering angle θ is positive, the turning center is on the left side, and it is determined that the vehicle is turning left. The turning radius r of the rear wheel 14 is calculated from the equation r = L _W / sin θ, where L _W is the wheel base. On the other hand, when the steering angle θ is negative, it is determined that the vehicle is turning right, and the turning radius r is calculated by the equation r = L _W / sin as described above.
It is calculated from θ. In FIG. 3, a subscript 1 is added to a left turn, and a subscript 2 is added to a right turn.

If the vehicle speed V and the turning radius r with respect to the center point of the contact surface of the rear wheel 14 are obtained based on the signals from the vehicle speed sensor 36 and the steering angle sensor 28 in this manner, The current yaw rate Y _C with respect to the center point of the ground contact surface is calculated by the equation Y _C = V / r (step 122). In addition, Step 104 and Step 1
Depending on the determined moving direction and the turning direction at 16,118, reference numeral is attached to the yaw rate Y _C (step 12
4). This encoding process is performed according to the following table. For example, when the reach forklift 10 is turning right and moving forward, the sign of the yaw rate is negative. Then, when the traveling direction is switched to the reverse while maintaining the right turn, the sign becomes positive. Further, the sign of the yaw rate is positive when the forklift 10 is turning left and moving forward, and negative when the forklift 10 is moving backward. .

[0029]

[Table 1] If the current yaw rate Y _C is thus obtained with a sign, the data of the yaw rate Y _R before the predetermined time ΔT is read from the RAM 44 (step 126).
The yaw acceleration ΔY / ΔT is given by the formula ΔY / ΔT = (Y _C −Y _R )
/ ΔT (step 128). Based on the value of yaw acceleration ΔY / ΔT obtained by this calculation,
For example, the damper cylinder 3
Control such as closing the shutoff valve 40 of No. 8 is performed.

Thereafter, at step 130, Y _R is replaced with Y _C and stored in the _RAM 26, and the routine returns to step 100.

As described above, the yaw acceleration ΔY / ΔT
Is constantly detected, but when switchback is performed during turning, the yaw acceleration ΔY / ΔT shows a change as shown in FIG. FIG. 4B shows the relationship between the time T and the yaw rate Y when a left turn is performed with the steering wheel turning angle kept constant and the switchback is made from forward to reverse while maintaining the turning state. T and yaw acceleration ΔY /
It is a graph which shows (DELTA) T. As can be seen from this figure, since the sign of the yaw rate Y changes when switching from forward to reverse, the sign of the yaw acceleration ΔY / ΔT does not change. In addition, in the case of switchback, since the traveling direction is switched in a short time, the yaw acceleration ΔY / ΔT shows a substantially constant value. Therefore, if the absolute value of the yaw acceleration ΔY / ΔT is, for example, equal to or more than the predetermined value α that regulates the swing of the rear wheel immediately before the switchback, even if the switchback is performed,
Since the yaw acceleration ΔY / ΔT detected by the yaw acceleration detection device of the present embodiment does not fall below the predetermined value α,
There is no problem that the swing regulation is released at the time of switchback during turning. This effect will be apparent from a comparison with FIG. 4A in which the sign is not assigned to the yaw rate Y for each traveling direction. Of course, the same applies to the case of the left turn and the case of the switchback from the reverse to the forward.

Although the preferred embodiments of the present invention have been described in detail, it goes without saying that the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the vehicle speed sensor 36 detects whether the vehicle is moving forward or backward. However, as the traveling direction detecting unit, a tilt direction detecting unit 34 interlocked with the forward / reverse switching lever 34 is used. Can be.

Further, the turning radius is calculated by an equation, but the relationship between the steering angle and the turning radius is represented by a map as R.
The information may be stored in the OM 46 and determined using the map.

Further, the yaw acceleration detecting device according to the present invention does not require a yaw rate sensor, and detects the vehicle speed and the steering angle in relation to the rear wheels 14 as described above. Therefore, the yaw acceleration detecting device is particularly effective for a battery type reach forklift. However, the present invention can be applied to other industrial vehicles.

[0035]

As described above, the yaw acceleration detecting device according to the present invention does not require a yaw rate sensor.
Effective for battery-powered industrial vehicles.

Further, since the yaw rate is calculated from the vehicle speed and the steering angle and the sign of the yaw rate is further divided according to the traveling direction, the yaw rate and the rate of change thereof can be accurately obtained. Therefore, it is possible to use the yaw acceleration detecting device of the present invention even in a vehicle that performs a sudden change of direction such as a switchback.

As described above, the present invention is particularly effective for a battery type reach forklift.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a battery type reach forklift to which a yaw acceleration detecting device according to the present invention is applied.

FIG. 2 is a flowchart for implementing a yaw acceleration detection device according to the present invention.

FIG. 3 is a schematic explanatory diagram showing a relationship between a steering angle of a rear wheel and a turning radius in a reach forklift.

FIG. 4 is a graph showing the relationship between the time T and the yaw rate Y when switching back from forward to reverse during a left turn, and the time T and the yaw acceleration ΔY / ΔT. (B) shows the case of the conventional yaw acceleration detecting means.

[Explanation of symbols]

10 ... reach forklift, 12 ... front wheel, 14 ... rear wheel, 28 ... steering angle sensor (turning radius detecting means), 30 ...
Controller (vehicle speed detecting means, turning radius detecting means, yaw rate calculating means, yaw acceleration calculating means), 36 ... vehicle speed (rotation speed) sensor (vehicle speed detecting means, traveling direction determining means).

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) B62D 137: 00 G01P 15/00 Z J

Claims (2)

[Claims] 1. A vehicle speed detecting means for detecting a vehicle speed at a predetermined point on a machine base; a turning radius detecting means for detecting a turning radius at the predetermined point; a vehicle speed detected by the vehicle speed detecting means and the turning radius A yaw rate calculating means for calculating a yaw rate from the turning radius detected by the detecting means, a yaw acceleration calculating means for calculating a rate of change of the yaw rate with respect to time from the yaw rate calculated by the yaw rate calculating means, A traveling direction discriminating means for discriminating whether the vehicle is traveling in the reverse direction, and assigning different signs to the yaw rates according to the traveling directions detected by the traveling direction discriminating means so as to obtain a yaw acceleration. Acceleration detector. 2. In a case where the industrial vehicle is a reach forklift having a front wheel that is a driven wheel and a rear wheel that is a steered wheel and a drive wheel, the vehicle speed detecting means detects the rotation speed of the rear wheel. A rotation speed sensor; and means for determining a vehicle speed based on a signal from the rotation speed sensor. The turning radius detection means detects a steering angle of the rear wheel, and the steering angle. The yaw acceleration detecting device for an industrial vehicle according to claim 1, further comprising means for determining a turning radius based on a signal from a sensor.