JP7119966B2 - forklift - Google Patents

Description

The present invention relates to forklifts.

In a cargo handling operation using a forklift, cargo is moved to a target location while being placed on a fork or a pallet into which the fork is inserted.

At this time, if the load placed on the fork or the pallet into which the fork is inserted is subjected to vibration or shock, the load may collapse. Therefore, various methods for suppressing collapse of cargo have been disclosed.

For example, Patent Literature 1 discloses a cargo collapse prevention device. The cargo collapse prevention device of Patent Document 1 includes an acceleration sensor for detecting vibration and impact of a cargo handling machine (for example, a forklift), a processing device that compares the acceleration value detected by the acceleration sensor with a preset threshold value, The processing unit has an alarm generating means for generating an alarm when the acceleration value exceeds a threshold value, or a speed control means for controlling the speed of the cargo handling machine.

In the cargo collapse prevention device described in Patent Document 1, the acceleration sensor is provided at a location where the vibration or impact applied to the cargo is easily detected, such as the upper end of the mast of a forklift. It can be detected as a value.

In the cargo collapse prevention device described in Patent Document 1, when the acceleration value detected by the acceleration sensor exceeds a threshold value, a signal is sent from the processing device to the alarm generation means, and the buzzer sounds, the pilot lamp lights, and the monitor is notified. An alarm such as a display is issued to notify the driver of the possibility of collapse of cargo or the like. With such an alarm, the driver can reduce the speed of the vehicle and perform avoidance driving to avoid the collapse of cargo, thereby preventing the collapse of cargo.

JP 2007-290817 A

The cargo collapse prevention device described in Patent Document 1 detects an acceleration value due to vibration or impact of a loaded cargo or pallet, and if the acceleration value exceeds a threshold, cargo collapse or the like may occur. , is determined. In addition, the threshold for judgment is set based on experiments conducted in advance according to the type of cargo handling equipment, the type and form of the cargo, and the weight, etc., and is sufficiently large compared to the acceleration value at which collapse of cargo actually occurs. is set to a value of about 50 to 80% as a low value with . In other words, the cargo handling speed is suppressed to 50 to 80% or less of the cargo handling speed at which cargo collapse occurs, which reduces the cargo handling efficiency. In addition, since thresholds for determination are set according to each case, such as the type of cargo handling machine, the type and form of cargo, and the weight, it takes a lot of time and effort to determine each threshold. Every time the type or weight changes, the threshold for determination must be changed, which is very troublesome.

SUMMARY OF THE INVENTION The present invention has been devised in view of the above points, and aims to easily suppress the collapse of loads placed on forks without trouble and to further suppress the decrease in work efficiency of cargo handling work. The object is to provide a forklift that can

In order to solve the above problems, a first invention provides a vehicle body, a traveling device for traveling the vehicle body, a cargo handling device for lifting and lowering a fork, a control device for controlling the traveling device and the cargo handling device, and a fork. Load slip detection means for detecting slippage of the loaded load and load slip suppression means are provided, and the control device detects slippage of the load on the forks using the load slip detection means, and detects the load slippage on the fork. In the forklift truck, the cargo slip suppressing means for suppressing the cargo slipping is operated when the cargo slipping detecting means detects the cargo slipping.

A second aspect of the present invention is the forklift according to the first aspect, wherein the fork includes a loading portion on which a load is placed and a supported portion supported by the cargo handling device. wherein the load slip detection means is a force detection means capable of detecting a force applied from the supported portion to the cargo handling device during acceleration or deceleration during travel of the forklift, and the control device detects the force In the forklift truck, it is determined that the load is slipping on the loading section when the rate of change of the force exceeds a predetermined value based on the detection result of the detection means.

A third aspect of the present invention is the forklift according to the second aspect, wherein the cargo handling device includes a lift bracket having a finger bar that supports the supported portion, and the supported portion includes the finger is supported by a bar, and the force detection means is arranged on a portion of a support contact surface facing the rear side of the forklift of the supported portion, which faces the finger bar; It's a forklift.

A fourth invention of the present invention is a forklift according to the second or third invention, wherein the cargo handling device includes a lift bracket having a finger bar that supports the supported portion, and the supported portion is , the force detecting means is arranged at a portion of the locking contact surface facing the front side of the forklift of the supported portion facing the finger bar. It is a forklift.

A fifth invention of the present invention is the forklift according to the third or fourth invention, wherein a plurality of the finger bars are arranged in a vertical direction, and the force detection means detects the supported portion. The forklift is provided at a portion of the supported portion facing the lowermost finger bar among the finger bars supporting the lift bracket.

A sixth invention of the present invention is a forklift according to any one of the first invention to the fifth invention, wherein the cargo handling device guides the movement of the fork in the vertical direction, has a mast that can be tilted in the front-rear direction with respect to the vehicle, and the load slip suppression means controls the inertial traveling of the vehicle body during travel, or increases the inclination angle of the mast with respect to the vehicle body, or A forklift that is at least one of the reducing controls.

A seventh aspect of the present invention is the forklift truck according to any one of the first aspect to the sixth aspect, wherein the control device controls the load slip suppression means when traveling in a forward direction. It is a fork riff that activates.

For example, when a forklift is accelerating forward travel, if a cargo placed on the forks collapses, the following phenomena occur in the order described below, leading to collapse of the cargo. First, a load that has been stationary on the fork begins to slide relative to the fork when acceleration exceeds a certain threshold. By the time the load starts to slide against the forks, it has not yet collapsed. After that, if the load continues to slide on the forks, the load eventually collapses. According to the first invention, by detecting the slippage (beginning of slippage) of the load on the forks, the signs of load collapse can be appropriately detected, and by suppressing the load slide before the load collapses, the load collapse can be prevented. can be suppressed. In addition, since the slippage of cargo that actually occurs is detected, there is no need to determine the threshold according to the type of cargo handling machine, cargo type, form, weight, etc., or to change the threshold for each task. It is possible to suppress collapse of cargo. Moreover, since the slippage of the load that actually occurred is detected and the slippage of the load is suppressed, there is no need to reduce the work speed more than necessary. That is, it is possible to further suppress a decrease in work efficiency of cargo handling work.

According to the second aspect of the invention, it is possible to appropriately detect the moment when the load, which has been stationary with respect to the fork due to static friction, begins to slide with respect to the fork as the static friction changes to dynamic friction.

According to the third invention, it is possible to appropriately detect the rate of change in the force when the forklift is accelerating in the forward direction or decelerating in the reverse direction.

According to the fourth invention, it is possible to appropriately detect the rate of change in the force when the forklift is accelerating in the reverse direction or decelerating in the forward direction.

More force applied from the fork to the lift bracket during acceleration or deceleration is applied to the lower finger bar than to the upper finger bar. According to the fifth invention, the detection signal from the force detection means can be obtained as a detection signal with a better S/N ratio, so that the slippage of the load on the forks can be detected with higher accuracy.

According to the sixth invention, load slippage can be suppressed with a simple configuration without adding a special device.

According to the seventh invention, load slippage can be suppressed with a simpler configuration.

1 is a side view of a forklift according to an embodiment of the present invention; FIG. 1 is a perspective view showing a fork according to an embodiment of the invention; FIG. 4 is an exploded perspective view showing the arrangement of a pair of left and right force detection means in the fork according to the first embodiment; FIG. 4 is a cross-sectional view along the XZ plane for explaining the arrangement of force detection means of the first embodiment; FIG. FIG. 2 is a block diagram for explaining inputs and outputs of a forklift control device; FIG. 10 is a cross-sectional view for explaining the operation of the force detection means with respect to the pallet on which the load is placed when the forklift travels in the forward direction; FIG. 5 is a cross-sectional view for explaining the operation of the force detection means when the pallet on which the load is placed is slipping while the forklift is traveling in the forward direction; It is a figure explaining the relationship of the magnitude|size of the force detected by the force detection means with respect to the magnitude|size of the acceleration of the forward direction of a forklift. FIG. 5 is a diagram illustrating the relationship between the rate of change in force during accelerated travel in the forward direction of the forklift. It is a figure explaining the example of the relationship between the travel speed of a forklift, and the magnitude|size of the force detected by a force detection means. It is a flow chart explaining control in load slip control means of a 1st embodiment. It is a sectional view in the XZ plane explaining the structure of the force detection means of 2nd Embodiment. FIG. 5 is a cross-sectional view for explaining the operation of the force detection means with respect to the pallet on which the load is placed when the forklift travels in the backward direction; FIG. 5 is a cross-sectional view for explaining the operation of the force detecting means when the pallet on which the load is placed is slipping while the forklift is accelerating in the backward direction; It is a flow chart explaining control in load slip control means of a 2nd embodiment. FIG. 5 is a cross-sectional view for explaining the operation of the force detecting means with respect to the load placed on the pallet when the forklift travels in the forward direction;

Embodiments for carrying out the present invention will be described below with reference to the drawings. In addition, when the X-axis, the Y-axis, and the Z-axis are described in the drawing, each axis is orthogonal to each other. In FIG. 1, the direction from the rear to the front of the vehicle body 11 is the X-axis direction, and the direction from the bottom to the top of the vehicle body 11 is the Z-axis direction. Also, the X-axis direction is defined as "front", the direction opposite to the X-axis direction is defined as "rear", the Z-axis direction is defined as "up", and the direction opposite to the Z-axis direction is defined as "down". Also, the Y-axis direction is defined as "left", and the opposite direction to the Y-axis direction is defined as "right".

● [Overall configuration of forklift 10 according to the embodiment of the present invention (Figs. 1 and 2)]
The overall configuration of a forklift 10 for carrying out the present invention will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a side view of a forklift 10 according to an embodiment of the invention. FIG. 2 is a perspective view showing a pair of left and right forks 30 (30R, 30L) according to the embodiment of the present invention.

As shown in FIG. 1 , the forklift 10 includes a vehicle body 11 and a cargo handling device 12 for raising and lowering a fork 30 on the front portion of the vehicle body 11 . The forklift 10 has driving wheels 14 as front wheels provided at the front portion of the vehicle body 11, steering wheels 15 as rear wheels provided at the rear portion of the vehicle body 11, and front and rear wheels for allowing the driver to switch between forward and backward traveling. A forward lever 60 is provided. In addition, in the description of the present embodiment, the forklift 10 is an engine forklift.

The cargo handling device 12 has a mast 20 having an outer mast 18 and an inner mast 19 , a lift bracket 24 , a backrest 28 and a fork 30 . A pair of left and right outer masts 18 are provided with inner masts 19 that can slide up and down inside the outer masts 18 .

The tilt cylinder 21 is hydraulically operated and installed between the vehicle body 11 and the outer mast 18 . The mast 20 is tilted in the front-rear direction with the lower end portion as a fulcrum by the operation of the tilt cylinder 21 . The mast 20 is provided with a lift cylinder 22 which is hydraulically operated, and the operation of the lift cylinder 22 causes the inner mast 19 to slide up and down within the outer mast 18 to be raised and lowered. Accordingly, the cargo handling device 12 can move the forks 30 (30R, 30L) in the vertical direction and tilt them in the front-rear direction with respect to the vehicle body 11 .

The lift bracket 24 can be fitted with a backrest 28 that prevents a load placed on the forks 30 from falling behind the mast 20 . 2, illustration of the backrest 28 is omitted.

A pair of left and right forks 30 are provided with respect to the mast 20 via the lift bracket 24 . The lift bracket 24 is provided with respect to the inner mast 19 and can be raised and lowered with respect to the mast 20 . Since the left and right forks 30 have the same configuration, for convenience of explanation, the right fork 30 is referred to as the fork 30R and the left fork 30 as the fork 30L.

As shown in FIG. 2, the fork 30 (30R, 30L) has a placing portion 31 on which a load is placed and a supported portion 33 supported by the cargo handling device 12. The support portion 33 is integrally formed to form a substantially L shape.

The lift bracket 24 includes a pair of upper and lower finger bars (a first finger bar 25 and a second finger bar 26) arranged vertically to support the supported portion 33, and both ends of the pair of upper and lower finger bars in the left and right direction. and a connecting member 27 that connects the parts respectively. The first finger bar 25 is the upper finger bar and the second finger bar 26 is the lower finger bar.

As shown in FIG. 2, in the cargo handling work, for example, the load LD is placed on the placing portion upper surface 34 of the placing portion 31 of the fork 30 (30R, 30L) via the pallet PT.

● [Arrangement and function of force detection means 58FR and 58FL in cargo handling equipment (Figs. 3 and 4)]
FIG. 3 is an exploded perspective view showing the arrangement of a pair of left and right force detection means 58FR and 58FL in the fork 30 (30R and 30L) according to the first embodiment. FIG. 4 is a cross-sectional view along the XZ plane for explaining the arrangement of the force detection means 58FR and 58FL of the first embodiment.

The forklift 10 (see FIG. 1) is provided with force detection means 58FR and 58FL. The force detection means 58FR, 58FL can detect the force applied from the supported portion 33 to the cargo handling device 12 (see FIG. 1) during travel of the forklift 10, and detect the load placed on the forks 30 (30R, 30L). It is load slip detection means for detecting slip.

As shown in FIG. 3, the supported portion 33 is provided with an upper hook 42 on the upper side and a lower hook 43 on the lower side. The upper hook 42 and the lower hook 43 may be formed integrally with the supported portion 33, or may be integrally formed by welding separate members. The supported portion 33 is locked to the first finger bar 25 by the upper hook 42 and to the second finger bar 26 by the lower hook 43, respectively.

As shown in FIG. 4, the force detection means 58FR and 58FL detect the back surface 33a of the supported portion 33 of the forks 30 (30R and 30L) facing the rear side of the forklift 10 (support contact). (corresponding to the contact surface), it is arranged at a portion facing the second finger bar 26 that supports the supported portion 33 . In addition, the force detection means 58FR and 58FL are supported by the second finger bar 26, which is the lowest among the finger bars supporting the supported portion 33 with respect to the lift bracket 24. It is provided in the part 33 .

Further, the force detection means 58FR and 58FL have a gap so that the force detection surface 58Fa, which is the surface for detecting force, and the second finger bar front surface 26a, which is the front surface of the second finger bar 26, face each other. , is provided. The force detection means 58FR and 58FL are, for example, pressure sensors that detect the applied force as pressure. The pressure sensor is, for example, a piezoelectric element or the like, and converts strain in the direction in which pressure is applied into voltage.

As shown in FIG. 4, when the cargo LD is placed on the placing portion 31 via the pallet PT in the cargo handling work of the forklift, the lower surface LDa, which is the lower surface of the cargo LD, and the upper surface of the deck board of the pallet PT. The deck board upper surface PTb comes into contact, and the deck board lower surface PTa, which is the lower surface of the deck board of the pallet PT, and the placing portion upper surface 34, which is the upper surface of the placing portion 31, come into contact.

● [Input/output of the control device 50 of the forklift 10 (Fig. 5)]
FIG. 5 is a block diagram illustrating inputs and outputs of the control device 50 of the forklift 10 (see FIG. 1).

The control device 50 controls the travel device 52A, the hydraulic pump 52B, and the valve 52C. The controller 50 receives detection signals from the force detection means 58FR and 58FL and the forward/reverse lever 60 . Further, the control device 50 drives the tilt cylinder 21 and the lift cylinder 22 by controlling the hydraulic pump 52B and the valve 52C, and controls the cargo handling device 12 . The force detection means 58BR and 58BL indicated by dotted lines are used in a forklift of a second embodiment, which will be described later.

The control device 50 includes storage means 50 a and load slip suppression means 56 . The storage means 50a stores the magnitudes of the forces detected by the force detection means 58FR, 58FL, 58BR, and 58BL, and stores a threshold value for determining that the load is slipping with respect to the change rate of the forces. Note that the load slip suppression means 56A is used in a forklift of a second embodiment, which will be described later.

The travel device 52A controls the driving wheels 14 (see FIG. 1), which are the front wheels, and outputs the operating state (rotational speed, etc.) to the control device 50. As shown in FIG. The load slip suppression means 56 suppresses the load slip when the load slip detection means detects the load slip.

● [Control of the load slip suppression means 56 in the forklift of the first embodiment (Figs. 6 to 11)]
FIG. 6 is a cross-sectional view for explaining the operation of the force detection means 58FR and 58FL (load slippage detection means) with respect to the pallet PT on which the load LD is placed when the forklift 10 (see FIG. 1) travels forward. (See Figure 1). FIG. 7 is a cross-sectional view for explaining the operation of the force detection means 58FR and 58FL when the pallet PT on which the load LD is placed is slipping while the forklift 10 is traveling in the forward direction.

In FIG. 6, when the forklift 10 (see FIG. 1) travels in the forward direction, when the magnitude of acceleration Af1 in the forward direction is applied to the vehicle body 11, the space between the lower surface LDa and the deck board upper surface PTb and the lower surface of the deck board A frictional force corresponding to the acceleration magnitude Af1 in the forward direction is generated between PTa and the mounting portion upper surface 34 . For convenience of explanation, the case where the frictional force between the lower surface LDa and the deck board upper surface PTb is sufficiently greater than the frictional force between the deck board lower surface PTa and the mounting portion upper surface 34 will be described. In other words, the case where the load LD does not slide on the pallet PT and the pallet PT on which the load LD is placed slides on the placing portion 31 with respect to the change in the acceleration magnitude Af1 in the forward direction will be described. .

When the forklift 10 travels in the forward direction and an acceleration magnitude Af1 in the forward direction is generated, the pallet PT is subjected to an inertial force Rf1 that tends to move the pallet PT rearward, and the lower surface of the deck board PTa resists this force. A static frictional force Fr1, which is a frictional force, is generated with the mounting portion upper surface 34 . When the inertia force Rf1 is smaller than the maximum (maximum static friction force) of the static friction force Fr1, the pallet PT does not slip on the placement section 31 and stops.

However, since the forks 30 (30R, 30L) are not fixed to the lift bracket 24, they are moved rearward by the inertia force due to the acceleration magnitude Af1 in the forward direction, and the force detection surface 58Fa is moved toward the second finger. It contacts the bar face 26a. In this case, forces FfR1 and FfL1 corresponding to the static friction force Fr1 are applied to the force detection surfaces 58Fa of the force detection means 58FL and 58FR, respectively.

In FIG. 7, when the forklift 10 is further accelerated in the forward direction and a forward acceleration magnitude Af2 greater than the forward acceleration magnitude Af1 (see FIG. 6) is applied to the vehicle body 11, the inertia force Rf2 becomes: The maximum (maximum static friction force) of the static friction force Fr1 (see FIG. 6) is exceeded. In this case, the resting pallet PT (the position indicated by the two-dot chain line) begins to slide on the placing section 31 and is moved backward (the position indicated by the solid line).

When the pallet PT starts to slide, the frictional force between the deck board lower surface PTa and the placing portion upper surface 34 changes from static frictional force Fr1 to dynamic frictional force Fr2. The magnitude of the dynamic friction force Fr2 is smaller than the magnitude of the static friction force Fr1. In this case, forces FfR2 and FfL2 corresponding to the dynamic friction force Fr2 are applied to the force detection surfaces 58Fa of the force detection means 58FL and 58FR, respectively.

FIG. 8 is a diagram for explaining the relationship between the magnitude of acceleration Af in the forward direction of the forklift 10 and the magnitude of force detected by the force detection means 58FL and 58FR. FIG. 9 is a diagram for explaining the relationship between the force change rate R during accelerated traveling of the forklift 10 in the forward direction. Note that the force change rate R is a very small amount of change in force per unit time.

In FIG. 8, the region S1 is such that the inertial force Rf1 in FIG. , FfL1) increases in proportion to the magnitude of acceleration Af in the forward direction.

In the region S1, the force Ff (FfR1, FfL1) represents the static friction force Fr1, and therefore increases in proportion to the forward acceleration magnitude Af that produces the inertia force Rf1. As shown in FIG. 9, in region S1, for example, when force Ff (FfR1, FfL1) changes constantly as shown in FIG. 8, force change rate R is constant at force change rate R1.

8, the inertial force Rf2 in FIG. 7 becomes larger than the maximum static frictional force, and the stationary pallet PT begins to slide on the platform 31 with the dynamic frictional force Fr2, and the force Ff (FfR1, FfL1 ) represents the state of change with respect to the magnitude of acceleration Af in the forward direction.

In the region S1, when the magnitude Af of acceleration in the forward direction increases and the frictional force due to the inertial force Rf1 exceeds the maximum static frictional force (frictional force corresponding to the force Ffx), the stationary pallet PT is placed. It begins to slide against the portion 31 . As a result, the frictional force changes from the maximum static frictional force (frictional force corresponding to force Ffx) to dynamic frictional force Fr2 (frictional force corresponding to force Ffm).

As shown in FIG. 9, the force Ff (FfR1, FfL1) changes from the force Ffx to the force Ffm in the region S2. change amount of Af). After that, the force Ff becomes the force Ffm and becomes constant, so the force change rate R becomes zero. The control device 50 (see FIG. 5) determines that the stationary load is slipping when the force change rate R exceeds a predetermined value Rth. The predetermined value Rth is the change rate of the force at the instant when the load starts to slide, which is obtained in advance by experiments or the like, and is stored in the storage means 50a.

In FIG. 10, areas A1 and A5 are periods during which the forklift 10 is accelerating while traveling in the forward direction. Areas A2 and A4 are periods during which the forklift 10 is traveling at a constant speed in the forward direction. A region A3 is a period during which the forklift 10 is decelerating while traveling in the forward direction. In the above diagram, the forklift 10 accelerates to a travel speed V1, decelerates to a travel speed V2, and further accelerates to a travel speed V3.

Further, the lower diagram of FIG. 10 shows changes in force Ff (FfR1, FfL1) in each area (areas A1 to A6). Force Ff (FfR1, FfL1) rises to force Ff1 in region A1, falls from region A2 to force Ff2 in region A4 corresponding to the pressure caused by the weight of forks 30 (30R, 30L), etc., and decreases in region A5. It rises to the force Ff3 (equivalent to the maximum static friction force). Since the force Ff does not exceed the force Ff3 in the regions A1 to A5, the cargo does not slip.

● [Control of load slip suppression means 56 (Fig. 11)]
A processing procedure of the control device 50 (see FIG. 5) will be described with reference to the flowchart of FIG. FIG. 11 is a flow chart for explaining the control in the load slip suppression means 56 (see FIG. 5) of the forklift of the first embodiment. In addition, when the control device 50 is activated, the control device 50 executes the process at predetermined time intervals (for example, at approximately 10 [ms] intervals). Each step will be described in detail below.

In step S10, the control device 50 acquires travel information of the vehicle body 11 (see FIG. 1), and proceeds to step S20. The traveling information of the vehicle body 11 includes the operation state of the traveling device 52A (see FIG. 5), selection information of "forward" or "reverse" in the forward/reverse lever 60, and the like.

In step S20, the control device 50 obtains the forces FfR and FfL by the force detection means 58FR and 58FL (load slip detection means) (see FIG. 5), and proceeds to step S25.

In step S25, if the control device 50 determines that the predetermined time has passed since the timer was started (Yes), the process proceeds to step S30. The process proceeds to step S90. In addition, the timer is for operating the load slip suppression means 56 for a predetermined time in the control device 50, and operates for a preset time when activated.

In step S30, if the control device 50 determines that the forklift 10 (see FIG. 1) is traveling forward (Yes), the process proceeds to step S40, and if the forklift 10 is not traveling in the forward direction. If so (No), the process proceeds to step S85. Note that the control device 50 determines whether the forklift 10 is moving forward or backward based on the operating state of the traveling device 52A and information on the forward/reverse lever 60 .

In step S40, if the control device 50 determines that the forklift 10 is accelerating in the forward direction (Yes), the process proceeds to step S50, and if it determines that the forklift 10 is not accelerating in the forward direction ( No), the process proceeds to step S85. Note that the control device 50 determines whether the forklift 10 is accelerating based on the information in the travel device 52A.

In step S50, when the control device 50 determines that the forces FfbR and FfbL are stored in the storage means 50a (Yes), the process proceeds to step S60, and the forces FfbR and FfbL are stored in the storage means 50a (see FIG. 5). is not stored (No), the process proceeds to step S85. The forces FfbR and FfbL are the forces FfR and FfL acquired in step S20 in the previous process. Further, the forces FfbR and FfbL are initialized when the forklift 10 is started and when the forward/reverse lever 60 is switched in the forward/backward direction.

In step S60, based on the forces FfbR and FfbL stored in the storage means 50a and the forces FfR and FfL acquired this time, the control device 50 controls the force change rate RR ((force FfR−force FfbR)/predetermined time), RL ((force FfL−force FfbL)/predetermined time) is calculated, and the process proceeds to step S70.

In step S70, if the control device 50 determines that one of the force change rates RR and RL has exceeded the predetermined value Rth (Yes), the process proceeds to step S80, and the force change rate RR , RL do not exceed the predetermined value (No), the process proceeds to step S85. The predetermined value Rth is a value set in advance and stored in the storage means 50a.

In step S80, the control device 50 starts the operation of the load slip suppression means 56 (see FIG. 5) described later (starts a timer, stops the acceleration of the vehicle body 11, and shifts to inertial running), and proceeds to step S90. proceed.

In step S85, the control device 50 cancels the operation of the load slip suppression means 56, and advances the process to step S90.

In step S90, the control device 50 stores the forces FfR and FfL in the storage means 50a as forces FfbR and FfbL, respectively, and ends the process.

● [Operation of load slip suppression means 56]
When the controller 50 (see FIG. 5) determines that one of the force change rates RR and RL exceeds a predetermined value Rth (see region S2 in FIG. 9), the fork 30 (30R, 30L) ) is slipping on the forks 30 (30R, 30L) (see FIG. 7). As a result, by capturing the moment when the frictional force changes from the static frictional force to the dynamic frictional force, it is possible to appropriately detect the moment when the load LD begins to slide on the forks 30 (30R, 30L) (load slippage of the load). can be done.

When the control device 50 detects the slippage of the load, the control device 50 starts a timer and operates the load slip suppression means 56 for a predetermined period set in advance. The load slip suppression means 56 controls the travel device 52A to stop acceleration of the vehicle body 11 and shift to inertial travel (see FIG. 5). As a result, the inertial force accompanying the acceleration of the vehicle body 11 disappears, and the inertial force applied to the load is reduced to be smaller than the frictional force, so that the load can be stopped from slipping on the fork or the like.

The operation of the load slip suppression means 56 (see FIG. 5) will be described with reference to FIG. In the area A5, the force Ff detected by the force detection means 58FR and 58FL (see FIG. 5) increases as the vehicle body 11 (see FIG. 1) accelerates. When the force Ff exceeds the force Ff3 (equivalent to the maximum static friction force), that is, when the inertial force becomes greater than the maximum static friction force, the load starts to slide, so the frictional force changes from the maximum static friction force (equivalent to the force Ff3) to the dynamic friction It changes to force (equivalent to force Ff4).

In a region A6, the control device 50 (see FIG. 5) determines that the load has started to slide when the force change rate R from the force Ff3 to the force Ff4 exceeds a predetermined value Rth. When the control device 50 determines that the load has started to slide, the control device 50 activates the load slip suppression means 56 to stop the acceleration of the vehicle body 11 and shift to inertial running at the running speed V4C, thereby reducing the inertial force applied to the load. Reduce the friction force to stop the cargo from slipping. The force Ff4 is a force corresponding to the static friction force due to the load being stopped, and is the static friction force based on the weight of the fork or the like in the inertial running at the running speed V4C. The running speed V4 is the speed of the vehicle body 11 when the load slip suppression means 56 is not activated, and the load starts to slide, and if the slipping condition continues, the load eventually collapses.

● [Control of load slip suppression means in the form of the forklift of the second embodiment (Figs. 12 to 14)]
FIG. 12 is a cross-sectional view along the XZ plane for explaining the configuration of the force detection means 58BL and 58BR (load slippage detection means) of the forklift truck of the second embodiment. FIG. 13 is a cross-sectional view for explaining the operation of the load slip detection means 56A (see FIG. 5) with respect to the pallet PT on which the load LD is placed when the forklift 10 (see FIG. 1) travels backward.

While the forklift according to the first embodiment has only the force detection means 58FR and 58FL, the forklift according to the second embodiment further has force detection means 58BR and 58BL to detect the load. It is different in that it has load slip suppression means 56A instead of the slip suppression means 56 (see FIG. 5). The force detection means 58BR, 58BL and the load slip suppression means 56A will be described in detail below.

As shown in FIG. 12, the force detection means 58BR and 58BL detect the inner surface 43a of the lower hook 43 of the supported portion 33 facing the front side of the forklift 10 (corresponding to the locking contact surface). is arranged in a portion facing the second finger bar 26 in the . Further, the force detection means 58BR and 58BL detect the supported portion facing the second finger bar 26 which is the lowest among the finger bars supporting the supported portion 33 with respect to the lift bracket 24. It is provided at 33 locations.

The force detection means 58BR and 58BL are provided with a gap so that the force detection surface 58Ba, which is the surface for detecting force, and the second finger bar rear surface 26b, which is the rearward surface of the second finger bar 26, face each other. It is The force detection means 58BR and 58BL are pressure sensors that detect the applied force as pressure, like the force detection means 58FR and 58FL.

The control device 50A in the second embodiment differs from the control device 50 in the first embodiment shown in FIG. 5 in that the load slip suppression means 56 is a load slip suppression means 56A. The controller 50A also receives detection signals from the force detection means 58BR and 58BL indicated by dotted lines as well as the force detection means 58FR and 58FL indicated by solid lines.

In FIG. 13, when the forklift 10 (see FIG. 1) travels in the backward direction, when the magnitude of acceleration Ab1 in the backward direction is applied to the vehicle body 11, the space between the lower surface LDa and the deck board upper surface PTb and the deck board lower surface A frictional force is generated between PTa and the top surface 34 of the mounting portion according to the magnitude Ab1 of acceleration in the backward direction. A case where the frictional force between the lower surface LDa and the deck board upper surface PTb is sufficiently greater than the frictional force between the deck board lower surface PTa and the mounting portion upper surface 34 will be described. In other words, the case where the load LD does not slide on the pallet PT and the pallet PT on which the load LD is placed slides on the placing portion 31 with respect to the change in the acceleration magnitude Ab1 in the backward direction will be described.

When the forklift 10 travels in the backward direction and the magnitude of the acceleration in the backward direction Ab1 is generated, the pallet PT is subjected to an inertial force Rf3 that tries to move the pallet PT forward, and the deck board lower surface PTa resists this force. A static frictional force Fr3, which is a frictional force, is generated with the mounting portion upper surface 34 . When the inertia force Rf3 is smaller than the maximum (maximum static friction force) of the static friction force Fr3, the pallet PT is kept stationary with respect to the placement section 31 without slipping.

However, since the forks 30a (30aR, 30aL) are not fixed to the lift bracket 24, they are moved forward by the inertia force due to the acceleration magnitude Ab1 in the backward direction, and the force detection surface 58Ba is moved forward by the second finger. It contacts the bar back surface 26b. In this case, forces FbR1 and FbL1 corresponding to the static friction force Fr3 are applied to the force detection surfaces 58Ba of the force detection means 58BL and 58BR, respectively.

In FIG. 14, when the forklift 10 is further accelerated in the reverse direction and a reverse acceleration magnitude Ab2 larger than the reverse acceleration magnitude Ab1 (see FIG. 13) is applied to the vehicle body 11, the inertia force Rf4 is The maximum static friction force Fr3 (maximum static friction force) is exceeded. In this case, the resting pallet PT (the position indicated by the two-dot chain line) begins to slide on the placing section 31 and is moved forward (the position indicated by the solid line).

When the pallet PT starts to slide, the frictional force between the deck board lower surface PTa and the placing portion upper surface 34 changes from the static frictional force Fr3 to the dynamic frictional force Fr4, and the magnitude of the dynamical frictional force Fr4 is equal to the magnitude of the statical frictional force Fr3. smaller than

● [Control of load slip suppression means 56A (Fig. 15)]
The processing procedure of the control device 50A (see FIG. 5) will be described using the flowchart of FIG. FIG. 15 is a flow chart for explaining the control in the load slip suppression means 56A (see FIG. 5) of the forklift of the second embodiment. Each step that is different from the control in the load slip suppression means 56 in the first embodiment will be described in detail below. Each different step is represented by a thick solid line.

In step S20A, the control device 50A acquires the forces FfR, FfL, FbR, and FbL from the force detection means 58FR, 58FL, 58BR, and 58BL (load slip detection means), and advances the process to step S25.

In step S40A, when the control device 50A determines that the forklift 10 (see FIG. 1) is decelerating in the forward direction (Yes), the process proceeds to step S50A, and the forklift 10 is not decelerating in the forward direction. (No), the process proceeds to step S85A. Note that the control device 50A determines whether the forklift 10 is decelerating based on the information in the travel device 52A (see FIG. 5).

In step S50A, when the controller 50A determines that the forces FbbR and FbbL are stored in the storage means 50a (Yes), the process proceeds to step S60A, and the forces FbbR and FbbL are not stored in the storage means 50a. (No), the process proceeds to step S85A. The forces FbbR and FbbL are the forces FbR and FbL obtained in step S20 in the previous process. In addition, the forces FfbR, FfbL, FbbR, and FbbL are initialized when the forklift 10 is started and when the forward/reverse lever 60 is switched between the forward and backward directions.

In step S60A, the control device 50A calculates the force change rate RR ((force FbR-force FbbR) based on the forces FbbR and FbbL stored in the storage means 50a (see FIG. 5) and the forces FbR and FbL acquired this time. /predetermined time) and RL ((force FbL-force FbbL)/predetermined time) are calculated, and the process proceeds to step S70A.

In step S70A, if the control device 50A determines that one of the force change rates RR and RL has exceeded the predetermined value Rth (Yes), the process proceeds to step S80A, and the force change rate RR , RL do not exceed the predetermined value (No), the process proceeds to step S85A. The predetermined value Rth is a value set in advance and stored in the storage means 50a.

In step S80A, the control device 50A starts the operation of the load slip suppression means 56A (see FIG. 5) described later (starts the timer and increases the tilt angle of the mast 20 with respect to the vehicle body 11 (see FIG. 1)), The process proceeds to step S90A. In addition, the timer is for operating the load slip suppression means 56A for a predetermined period of time in the control device 50A, and operates for a preset period of time when activated. The angle of inclination in this embodiment is the angle formed by the vertical direction and the extending direction of the mast 20 . When the vertical direction and the extension direction of the mast 20 are 0 degrees, the tilt angle is increased (the clockwise direction around the Y axis in FIG. 1 is positive, and the fork is tilted in the positive direction). The tip of the mounting portion 31 of 30 rises, and when it is decreased (tilted in the negative direction), the tip descends. The inclination angle in this embodiment is an example, and may be changed as appropriate.

In step S30A, if the control device 50A determines that the forklift 10 is traveling in the reverse direction (Yes), the process proceeds to step S40B, and if it is determined that the forklift 10 is not traveling in the reverse direction (No ), the process proceeds to step S85A. Note that the control device 50A determines whether the forklift 10 is moving forward or backward based on information from the forward/reverse lever 60 (see FIG. 5).

In step S40B, if the control device 50A determines that the forklift 10 is decelerating in the reverse direction (Yes), the process proceeds to step S50B, and if it determines that the forklift 10 is not decelerating in the reverse direction ( No), the process proceeds to step S40C.

In step S50B, when the control device 50A determines that the forces FfbR and FfbL are stored in the storage means 50a (Yes), the process proceeds to step S60B, and the forces FfbR and FfbL are not stored in the storage means 50a. (No), the process proceeds to step S85A.

In step S60B, based on the forces FfbR and FfbL stored in the storage means 50a and the forces FfR and FfL acquired this time, the control device 50A changes the force change rate RR ((force FfR−force FfbR)/predetermined time), RL ((force FfL−force FfbL)/predetermined time) is calculated, and the process proceeds to step S70B.

In step S70B, if the control device 50A determines that one of the force change rates RR and RL exceeds the predetermined value Rth (Yes), the process proceeds to step S80B, and the force change rate RR , RL do not exceed the predetermined value (No), the process proceeds to step S85A.

In step S80B, the control device 50A starts the operation of the load slip suppression means 56A described later (starts the timer and increases the tilt angle of the mast 20 with respect to the vehicle body 11), and advances the process to step S90A.

In step S40C, if the control device 50A determines that the forklift 10 is accelerating in the reverse direction (Yes), the process proceeds to step S50C, and if it determines that the forklift 10 is not accelerating in the reverse direction ( No), the process proceeds to step S85A.

In step S50C, when the controller 50A determines that the forces FbbR and FbbL are stored in the storage means 50a (Yes), the process proceeds to step S60C, and the forces FbbR and FbbL are not stored in the storage means 50a. (No), the process proceeds to step S85A.

In step S60C, based on the forces FbbR and FbbL stored in the storage means 50a and the forces FbR and FbL acquired this time, the control device 50A changes the force change rate RR ((force FbR−force FbbR)/predetermined time), RL ((force FbL−force FbbL)/predetermined time) is calculated, and the process proceeds to step S70C.

In step S70C, if the control device 50A determines that one of the force change rates RR and RL exceeds the predetermined value Rth (Yes), the process proceeds to step S80C, and the force change rate RR , RL do not exceed the predetermined value (No), the process proceeds to step S85A.

In step S80C, the control device 50A starts the operation of the load slip suppression means 56A described later (starts a timer, stops the acceleration of the vehicle body 11, and shifts to inertial running), and advances the processing to step S90A.

In step S90A, the control device 50A stores the forces FfR, FfL, FbR, and FbL in the storage means 50a as forces FfbR, FfbL, FbbR, and FbbL, respectively, and ends the process.

● [Operation of load slip suppression means 56A]
When the controller 50A determines that one of the force change rates RR and RL exceeds a predetermined value Rth (see FIG. 9), the load LD placed on the fork 30a (30aR, 30aL) is slipping on the fork 30a (30aR, 30aL) (see FIGS. 12 to 14). Accordingly, by capturing the moment when the frictional force changes from the static frictional force to the dynamic frictional force, it is possible to appropriately detect the moment when the load LD starts to slide on the forks 30a (30aR, 30aL) (sliding of the load). can be done.

When the control device 50A detects the slippage of the load, the control device 50A activates the timer and operates the load slip suppression means 56A for a preset predetermined period.

When the vehicle body 11 is accelerating forward or backward, the load slip suppression means 56A controls the traveling device 52A to stop the acceleration of the vehicle body 11 and shift to inertia traveling. As a result, the inertial force accompanying the acceleration of the vehicle body 11 disappears, and the inertial force applied to the cargo is reduced to be smaller than the frictional force, so that the cargo can be stopped from slipping on the fork or the like.

The load slip suppression means 56A controls the hydraulic pump 52B and drives the tilt cylinder 21 to increase the tilt angle of the mast 20 with respect to the vehicle body 11 when the vehicle body 11 is moving forward and decelerating (see FIG. 1). As a result, the tip of the mounting portion 31 of the fork 30 rises, and a force is generated to move the load backward. Due to this force, the inertial force is reduced to be smaller than the frictional force, so that the luggage can be stopped from slipping on the fork or the like.

The load slip suppression means 56A controls the hydraulic pump 52B and drives the tilt cylinder 21 to reduce the tilt angle of the mast 20 with respect to the vehicle body 11 when the vehicle body 11 is decelerating in reverse (see FIG. 1). As a result, the tip of the mounting portion 31 of the fork 30 descends, and a force is generated to move the load forward. Due to this force, the inertial force is reduced to be smaller than the frictional force, so that the luggage can be stopped from slipping on the fork or the like.

● [When the cargo LD slides on the pallet PT (Fig. 16)]
In the first and second embodiments, the case where the pallet PT on which the load LD is placed has been described as slipping with respect to the placing portions 31 of the forks (30R, 30L, 30aR, 30aL). FIG. 16 shows the case where the load LD slides on the pallet PT, instead of the pallet PT sliding on the placing section 31. FIG.

In FIG. 16, when the forklift 10 (see FIG. 1) further accelerates in the forward direction, a forward acceleration magnitude Af5 greater than the forward acceleration magnitude Af1 (see FIG. 6) is applied to the vehicle body 11. , the inertial force exceeds the maximum static friction force (not shown). In this case, the stationary load LD (the position indicated by the two-dot chain line) begins to slide on the pallet PT and is moved toward the supported portion 33 (the position indicated by the solid line).

When the load LD starts to slide, the frictional force between the lower surface LDa and the deck board upper surface PTb changes from static frictional force to dynamic frictional force Fr5, and the dynamic frictional force Fr5 becomes smaller than the static frictional force. In this case, forces FfR5 and FfL5 corresponding to the dynamic friction force Fr5 are applied to the force detection surfaces 58Fa of the force detection means 58FL and 58FR, respectively. Accordingly, by capturing the moment when the frictional force changes from the static frictional force to the dynamic frictional force, it is possible to appropriately detect the moment when the load LD starts to slide on the pallet PT (load slippage).
● [Effects of the application]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to easily suppress collapse of loads placed on forks without trouble, and to further suppress a decrease in work efficiency of cargo handling work.

The forklift of the present invention is not limited to the configuration, structure, etc. described in the present embodiment, and various modifications, additions, and deletions are possible without changing the gist of the present invention. In particular, the force detection means (load slippage detection means) are provided on both the left and right forks, but may be provided on either one of the left and right forks.

The forklift described in the present embodiment is not limited to an engine forklift, and may be a forklift equipped with a cargo handling device. Further, the shape of the placement portion is not limited to a fork shape, and any shape that allows a load to be placed thereon may be used.

The force detection means (load slip detection means) is not limited to a pressure sensor, and may be a load sensor. Further, the force detection means (load slippage detection means) may be connected to the control device by wire or may be connected to the control device by radio. In the case of wireless connection to the control device, there is no need to consider the wiring layout for connecting the force detection means (load slip detection means) and the control device.

The force detection means (load slippage detection means) is arranged at a position facing the second finger bar 26 (see FIG. 4) in the description of the embodiment of the present application. Any position can be used as long as the frictional force generated when the slide slides can be detected appropriately.

The load slip suppression means is not limited to any one of stopping the acceleration of the vehicle body and shifting to inertial running, and increasing or decreasing the inclination angle of the mast with respect to the vehicle body. You may suppress a slip.

REFERENCE SIGNS LIST 10 forklift 11 vehicle body 12 cargo handling device 14 driving wheel 15 steering wheel 20 mast 21 tilt cylinder 22 lift cylinder 24 lift bracket 25 first finger bar 26 second finger bar 26a front face of second finger bar 26b rear face of second finger bar 27 connecting member 30 , 30R, 30L Fork 30a, 30aR, 30aL Fork 31 Mounting portion 33 Supported portion 33a Back surface of supported portion (corresponding to support contact surface)
34 Placement upper surface 42 Upper hook 43 Lower hook 43a Lower hook inner surface (corresponding to a locking contact surface)
50, 50A control device 50a storage means 52A travel device 52B hydraulic pump 52C valve 56, 56A load slip suppression means 58FL, 58FR force detection means (load slip detection means)
58BL, 58BR force detection means (load slippage detection means)
58Fa Force detection surface 58Ba Force detection surface 60 Forward/reverse lever LD Cargo LDa Lower surface PT Pallet PTa Deck board lower surface PTb Deck board upper surface Af, Af1, Af2 Magnitude of acceleration in forward direction Ab1, Ab2 Magnitude of acceleration in backward direction Fr1, Fr3 Static friction force Fr2, Fr4 Dynamic friction force Ff1, Ff2 Force Ff3, Ff4 Force Rf1, Rf2 Inertia force S1, S2 Area Ff, FfR, FfL Force FfR1, FfL1 Force R, RR, RL Force change rate A1, A2, A3 Regions A4, A5, A6 Regions V1, V2, V3 Travel speed V4, V4C Travel speed Rth Predetermined value

Claims (6)

a vehicle body;
a running device for running the vehicle body;
a cargo handling device that raises and lowers the fork;
a control device that controls the travel device and the cargo handling device;
load slip detection means for detecting slip of the load placed on the fork;
load slip suppression means;
has
The control device is
detecting slippage of the load on the fork using the load slip detection means;
A forklift that operates the load slip suppression means for suppressing the load slip when the load slip detection means detects the load slip,
The fork is
having a loading section on which a load is placed and a supported section supported by the cargo handling device;
The load slip detection means is
force detection means capable of detecting a force applied from the supported portion to the cargo handling device during acceleration or deceleration during travel of the forklift,
The control device is
Based on the detection result of the force detection means, it is determined that the load is slipping on the loading section when the magnitude of the rate of change in the force exceeds a predetermined value.
forklift. A forklift according to claim 1 ,
The cargo handling device
A lift bracket having a finger bar that supports the supported portion,
The supported portion is
supported by the finger bar,
The force detection means is
It is arranged at a portion of the supported portion facing the finger bar on the support contact surface that is the surface facing the rear side of the forklift,
forklift. A forklift according to claim 1 or 2 ,
The cargo handling device
A lift bracket having a finger bar that supports the supported portion,
The supported portion is
supported by the finger bar,
The force detection means is
It is arranged in a portion facing the finger bar on the locking contact surface, which is the surface of the supported portion facing the front side of the forklift,
forklift. A forklift according to claim 2 or 3 ,
A plurality of the finger bars are arranged in the vertical direction,
The force detection means is
provided at a portion of the supported portion facing the lowermost finger bar among the finger bars supporting the supported portion with respect to the lift bracket,
forklift. The forklift according to any one of claims 1 to 4 ,
The cargo handling device
It has a mast that guides the movement of the fork in the vertical direction and can be tilted in the front-rear direction with respect to the vehicle body,
The load slip suppression means is
control for inertia running of the running vehicle body;
or
control to increase or decrease the inclination angle of the mast with respect to the vehicle body;
is at least one of
forklift. The forklift according to any one of claims 1 to 5 ,
The control device is
activating the load slip suppression means when traveling in the forward direction;
forklift.

Images