JP2005350154A - Forklift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forklift able to make small radius cornering using a low-cost constitution. <P>SOLUTION: The forklift is equipped with a left and a right front wheel 2 and a left and a right rear wheel 3. The front wheels 2 are driving wheels to be given individually a driving force for regular and reverse rotation by respective motors 20, while the rear wheels 3 are casters arranged revolving individually round a left and a right shaft 30 so that the axles 31 are positioned in the back about the advancing direction in reference to the shafts 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a forklift used for loading and unloading loads.

  As shown schematically in FIGS. 12 and 13, a conventional general forklift is provided with a pair of front wheels 102 and a rear wheel 103 on the left and right sides of a body 101, a mast 104 at the front of the body 101, and a front side of the mast 104. The fork 105 is provided with a protrusion. Each front wheel 102 is a driving wheel, and forward and reverse rotational driving forces are individually applied from mutually independent driving motors 120 by a driver's operation of the handle 106, the brake / accelerator pedal 107, and the forward / reverse switching lever. On the other hand, each rear wheel 103 is supported so as to be able to turn about a pair of support shafts 130 on the left and right sides, and is connected to each other by a link member. Turn together. That is, the vehicle body 101 moves forward or backward as the front wheels 102 rotate forward and backward, and also turns and turns as the rear wheels 103 turn together.

  By the way, a place where a forklift is utilized is not a wide place without any obstacles, but a narrow and complex place where many obstacles such as luggage and pillars exist in the surroundings, such as in a warehouse. . For this reason, a forklift is strongly required to have a small turning function.

  However, in the conventional forklift described above, each rear wheel 103 is configured to pivot integrally with respect to each support shaft 130. Therefore, particularly when trying to turn the vehicle body 101 at a minimum on the spot, FIG. As shown in the figure, even if each rear wheel 103 is turned to the maximum extent, the extension line of each wheel axle only crosses at one position of each front wheel 102, and then one of each front wheel 102. Even if the other is rotated by the driving force from the drive motor 120 while the motor is stopped, the turning radius of the vehicle body 101 must be increased to some extent. The turning radius of the vehicle body 101 depends on the position of the turning center, but the turning center at the time of the minimum turning by the conventional forklift is limited to the position of the stopped front wheel 102. In this case, the turning center and the vehicle body 101 This is because the turning radius determined by the distance from the rear contour is biased to the left and right at the rear of the vehicle body 101.

As a technique for improving such an inconvenience, as shown in FIG. 15, an independent turning motor for individually turning each rear wheel 103 with respect to each support shaft 130 is provided, and the vehicle body 101 is minimized on the spot. When trying to turn, each rear wheel 103 is turned individually by each turning drive motor so that the extension line of each wheel axle intersects at the center position between each front wheel 102, and each front wheel 102 Some of them are rotated in different forward and reverse directions by the driving force from the drive motor 120. As a result, the turning center at the time of the minimum turning is the center position between the front wheels 102, and the turning radius becomes even and smaller at the left and right at the rear portion of the vehicle body 101 (see, for example, Patent Document 1).
JP-A-10-244951

  However, with such a technique, the turning radius of the vehicle body 101 can be minimized to a minimum, and a forklift with a small turn can be realized. However, a high-output turning motor for sufficiently turning each rear wheel 103 is separately provided. Since it is necessary, there is a problem that not only the component cost but also the running cost (power consumption) at the use stage is deteriorated.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a forklift with a small turn and an inexpensive configuration.

  To achieve the above object, according to the present invention, in a forklift having a pair of front and rear wheels on the left and right, each front wheel is a driving wheel to which a driving force of forward and reverse rotation is individually given by a mutually independent driving motor. Each rear wheel is a caster that is individually turnable around each support shaft such that each wheel shaft is positioned rearward in the traveling direction with reference to a pair of support shafts on the left and right. To do.

  With such a configuration, when trying to make a minimum turn on the spot, each front wheel is rotated forward and backward different from each other by the driving force from each drive motor, so that the center position between each front wheel is the turning center. Following this, each rear wheel naturally turns around each support shaft individually so that each wheel axle is located behind the direction of travel relative to each support shaft. The extension line of the axle of each rear wheel intersects at the center position between each front wheel. Therefore, since the turning center at the time of the minimum turning is the center position between the front wheels, the turning radius becomes small. However, it seems to move forward or backward by rotating each front wheel in the same direction, and at the same time, it seems to bend by giving a difference in left and right rotation speed of each front wheel, and following this, each rear wheel follows Since it can turn naturally around each spindle, there is no problem at all with respect to running and turning functions.

  Here, since each rear wheel is a caster, when the traveling direction is reversed in exactly the opposite direction, the wheel shaft of each rear wheel is positioned forward with respect to the traveling direction with reference to each support shaft. This state is an unstable state in which each rear wheel tries to make a sudden turn with respect to each support shaft, and at this time, it is desirable to be able to quickly escape from this unstable state. Therefore, from the viewpoint of realizing early departure from the unstable state of each rear wheel, the driving force applied to each front wheel by each drive motor is temporarily adjusted when the traveling direction is reversed. It is good to be.

  Similarly, from the viewpoint of realizing early departure from the unstable state of each rear wheel, the wheel axle of each rear wheel is moved from the front in the traveling direction with respect to each support shaft as the traveling direction is reversed. A slide mechanism that slides backward may be provided. However, in this case, if each rear wheel is inadvertently slid during traveling, there is a risk that instability of the traveling itself will result. Therefore, in order to prevent this, each of the rear wheels during traveling is prevented. It is preferable to provide a slide suppressing mechanism that suppresses sliding movement with respect to the support shaft.

  Furthermore, if each rear wheel turns inadvertently during a run other than when it is intended to bend, stable running will be hindered. It is preferable to provide a turning suppression mechanism that suppresses turning with respect to the support shaft.

  In addition, from the viewpoint of realizing stable traveling without unpleasant vibration, an angle sensor for detecting the turning position of each rear wheel with respect to each of the support shafts is provided, and based on the detection result of this angle sensor during traveling. When the fluctuation frequency of the turning angular velocity calculated in this way exceeds a predetermined reference value, it is preferable that the driving force applied to each front wheel by each driving motor is reduced.

  According to the forklift of the present invention, the minimum turning can be performed with a small turning radius, so that the turning is quick and agile, and this can be achieved at low cost by using each rear wheel as a caster.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the forklift which is 1st Embodiment of this invention is demonstrated. FIG. 1 is a side view showing the appearance of the forklift according to the first embodiment, FIG. 2 is a schematic plan view showing the drive mechanism of the forklift, FIG. 3 is a schematic plan view showing the main part of the forklift, and FIG. FIG.

  As shown in FIGS. 1 to 4, the forklift according to the present embodiment is roughly provided with a pair of front wheels 2 and rear wheels 3 on the left and right in the lower part of the vehicle body 1, and a mast 4 at the front portion of the vehicle body 1. It comprises a fork 5 protruding forward. Each front wheel 2 is a driving wheel, and forward and reverse rotational driving forces are individually applied from mutually independent drive motors 20 by the operation of the handle 6, the brake / accelerator pedal 7, and the forward / reverse switching lever by the driver. The drive of each drive motor 20 is controlled by a controller connected to the handle 6, the brake / accelerator pedal 7, and the forward / reverse switching lever.

  On the other hand, each rear wheel 3 is a caster and is supported so as to be individually turnable around a pair of support shafts 30 on the left and right. Specifically, a caster portion 32 having a wheel shaft 31 eccentric with respect to a support shaft 30 fixed to the vehicle body 1, and a ball bearing portion 33 that rotatably supports the caster portion 32 around the support shaft 30 are provided. It consists of

  Note that the lower end of the mast 4 is pivotally supported by the vehicle body 1 and is slightly tilted forward and backward by the driver's operation. The fork 5 is a part that directly supports an object such as loading and unloading and is moved up and down along the mast 4 by a driver's operation.

  In the forklift having such a configuration, the vehicle body 1 moves forward or backward by rotating the front wheels 2 in the same direction by the driving force from the driving motors 20. By giving a difference in the force distribution, the rotational speeds of the front wheels 2 are different from each other in the left and right directions, so that the rear wheels 3 (the caster portions 32) follow the respective support shafts 30 as a reference. Each wheel shaft 31 can be rotated naturally around each support shaft 30 individually so that each wheel shaft 31 is located behind the moving direction. Therefore, there is no problem at all with respect to the traveling and bending function of the vehicle body 1.

  Moreover, when trying to turn the vehicle body 1 with the minimum amount on the spot, as shown in FIG. 5, the front wheels 2 are rotated in different forward and reverse directions so that the center position between the front wheels 2 is the center of turning. Following this, each rear wheel 3 naturally turns about each support shaft 30 individually, and the extension line of the wheel shaft 31 of each rear wheel 3 is at the center position between each front wheel 2. Come to meet. Therefore, since the turning center at the time of the minimum turning is the center position between the front wheels, the turning radius becomes small. Then, since the minimum turning can be performed with a small turning radius, it is quick and agile. This can be achieved at low cost by making each rear wheel 3 a caster.

  Here, in the present embodiment, since each rear wheel 3 is a caster, as shown in FIG. 6, when the traveling direction of the vehicle body 1 is reversed in exactly opposite directions, for example, the driver advances / reverses from a stopped state. When the switch lever is operated, and then the brake / accelerator pedal 7 is operated with the handle 6 left unchanged, the wheel shaft 31 of each rear wheel 3 (caster portion 32) is a traveling direction (reverse direction) with respect to each support shaft 30. However, this state is an unstable state in which each rear wheel 3 tries to make a sudden turn with respect to each support shaft 30. Therefore, when each rear wheel 3 is in an unstable state, it is desirable to be able to quickly escape from this state.

  Therefore, in this embodiment, when the traveling direction is reversed, the driving force applied to each front wheel 2 from each drive motor 20 is temporarily adjusted. In other words, based on the operation of the steering wheel 6, the brake / accelerator pedal 7, and the forward / reverse switching lever by the driver, the controller recognizes whether the traveling direction is reversed or not, and if the controller recognizes that it is reversed, the controller Before sending a command for driving in a desired traveling direction (reverse direction) according to the driver's intention to each drive motor 20, each command for temporarily proceeding in a direction slightly deviated from the desired traveling direction It is sent to the drive motor 20. As a result, each rear wheel 3 naturally turns around the support shaft 30, and each wheel shaft 31 comes to be located rearward with respect to a desired traveling direction, so that it can escape from an unstable state.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a side view showing the appearance of the forklift according to the second embodiment, FIG. 8 is a schematic plan view showing the main part of the forklift, and FIG. 9 is a schematic sectional view thereof. The feature of the second embodiment is that the forklift according to the first embodiment described above is deformed, and the early departure from the unstable state of each rear wheel (see FIG. 6) is achieved on the structural surface. In these drawings, parts having the same names and performing the same functions as those relating to the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  In the present embodiment, the structure of each rear wheel 3 is different from that in the first embodiment. Specifically, as shown in FIGS. 7 to 9, each rear wheel 3 includes a caster portion 32 and a slide bearing portion that supports the caster portion 32 so as to be slidable in a direction substantially orthogonal to the support shaft 30. 34 and a ball bearing portion 33 that supports the slide bearing portion 34 so as to be pivotable around a support shaft 30 fixed to the vehicle body 1. With such a configuration, the caster portion 32 can turn freely around the support shaft 30 together with the slide bearing portion 34, and the slide bearing portion 34 is positioned at the slide end with respect to the ball bearing portion 33. 31 is in an eccentric state with respect to the support shaft 30.

  With such a configuration, during traveling, turning, and minimum turning, each rear wheel 3 follows the aspect of forward / backward movement, bending, or turning caused by the rotation of each front wheel 2 with the caster portion 32 positioned at the slide end. Then, each of the axles 31 can be turned naturally around each of the spindles 30 so that each of the axles 31 is located behind the traveling direction with reference to each of the spindles 30.

  Moreover, when reversing the traveling direction, the wheel shaft 31 of each rear wheel 3 (the caster part 32) is in an unstable state where it is positioned forward with respect to the traveling direction (reversing direction) with respect to each support shaft 30. Based on the operation of the steering wheel 6, the brake / accelerator pedal 7, and the forward / reverse switching lever by the driver, the controller issues a drive command in a desired traveling direction (reverse direction) according to the driver's intention to each driving motor. The vehicle body 1 advances in the desired direction of travel. Then, each caster portion 32 is slid to the other slide end with respect to the ball bearing portion 33 by the slide bearing portion 34, and the respective wheel shafts 31 are positioned rearward in the desired traveling direction. It becomes possible to escape from the stable state.

  However, in this case, if each rear wheel 3 is inadvertently slid during traveling, it may result in instability of the traveling itself, so it is desirable to take measures to prevent this. For example, as shown in FIG. 10, a compression coil spring 35 that urges the caster portion 32 toward the slide end with respect to the slide bearing portion 34 is provided, and the ball bearing portion 33, that is, the support shaft 30 is provided by the elastic force of the compression coil spring 35. It is possible to suppress inadvertent slide movement of the caster part 32 with respect to the above. Further, for example, the shape of the guide rail that guides the sliding movement of the caster part 32 may be curved so as to be lowered at both slide ends.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 11 is a schematic cross-sectional view showing a main part of the forklift according to the third embodiment. The feature of the third embodiment resides in that the forklifts of the first and second embodiments described above are modified so as to suppress inadvertent turning of each rear wheel during traveling. Although FIG. 11 shows the configuration of each rear wheel in the second embodiment as a base, it can of course be applied to each rear wheel in the first embodiment.

  In the present embodiment, a shaft portion 34a is provided integrally from the slide bearing portion 34 so as to penetrate the ball bearing portion 33 coaxially with the support shaft 30, and the tip of the shaft portion 34a is coaxial with the shaft portion 34a. The disk 34b is fixed. Further, a block member 36 is disposed opposite to the disk 34a. The block member 36 is moved up and down by a forward / reverse rotation driving force from an adjustment motor 37 fixed to the vehicle body 1 and is in contact with the disk 34a. It is designed to be able to take a separated state and a separated state. The adjustment motor 37 is connected to the controller, and the drive is controlled by the controller.

  According to such a configuration, during traveling, the adjustment motor 37 is driven by the command from the controller and the block member 36 is lowered, so that the block member 36 and the disk 34a are in contact with each other. Then, the movement of the disk 34a is suppressed by the frictional resistance with the block member 36, and as a result, the rotation of the slide bearing part 34 (caster part 32) integral with the disk 34a around the support shaft 30 is suppressed. Become. Accordingly, inadvertent turning of each rear wheel 3 is suppressed during traveling, and thus stable traveling is possible. However, when it is intended to turn, each rear wheel 3 can turn although there is some resistance.

  On the other hand, during low-speed running including stopping, the adjustment motor 37 is driven by the command from the controller and the block member 36 is raised, so that the block member 36 and the disk 34a are separated. Then, the disk 34a is free to move without receiving frictional resistance with the block member 36. As a result, there is no turning around the support shaft 30 of the slide bearing part 34 (caster part 32) integral with the disk 34a. Can be done without resistance.

  Next, a fourth embodiment of the present invention will be described. The feature of the fourth embodiment is that the forklifts of the first to third embodiments described above are designed to suppress inadvertent turning vibration that may occur in each rear wheel during traveling. This is because, since each rear wheel 3 is a caster, there is a risk that each rear wheel 3 will inadvertently oscillate with respect to each support shaft 30 especially during high speed running. It causes unpleasant vibration.

  In the present embodiment, an angle sensor that detects a turning position of each rear wheel 3 with respect to each support shaft 30 is provided. The angle sensor is connected to the controller and sends detection data to the controller.

  According to such a configuration, during traveling, detection data regarding the turning position of each rear wheel 3 is sequentially sent from the angle sensor, and the controller turns the respective rear wheels 3 with respect to each support shaft 30 based on the detected data. Angular velocity is calculated sequentially. Then, the controller calculates a fluctuating frequency from the successive turning angular velocities, and when this exceeds a predetermined reference value, the controller recognizes that the turning vibration of each rear wheel 3 is excessive and applies a driving force to each driving motor 20. Send a command to reduce. Thereby, since the rotation speed of each front wheel 2 falls and the traveling speed of the vehicle body 1 also falls, as a result, the turning vibration of each rear wheel 3 is eliminated. Accordingly, it is possible to realize stable running without unpleasant vibration.

  The command from the controller based on the detection result of the angle sensor in the present embodiment can be used for driving the adjustment motor 37 in the third embodiment, instead of being used for reducing the driving force of the drive motor 20. is there. That is, the adjustment motor 36 is driven by the command from the controller to further lower the block member 36, thereby increasing the pressure contact force, that is, the frictional resistance between the block member 36 and the disk 34 a, and as a result, the turning of each rear wheel 3. Is further suppressed to eliminate the turning vibration.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

  The present invention is useful for forklifts.

It is a side view which shows the external appearance of the forklift of 1st Embodiment of this invention. It is a schematic plan view which shows the drive mechanism of the forklift of 1st Embodiment. It is a schematic plan view which shows the principal part of the forklift of 1st Embodiment. It is a schematic cross section which shows the principal part of the forklift of 1st Embodiment. It is a schematic top view which shows the minimum turning condition of the forklift which is common to each embodiment of this invention. It is a schematic plan view which shows the unstable state which can arise in common with the rear wheel in each embodiment of this invention. It is a side view which shows the external appearance of the forklift of 2nd Embodiment of this invention. It is a schematic plan view which shows the principal part of the forklift of 2nd Embodiment. It is a schematic cross section which shows the principal part of the forklift of 2nd Embodiment. It is a schematic cross section which shows the principal part of the modification of the forklift of 2nd Embodiment. It is a schematic cross section which shows the principal part of the forklift of 3rd Embodiment of this invention. It is a side view which shows the external appearance of the conventional forklift. It is a schematic plan view which shows the drive mechanism of the conventional forklift. It is a model top view which shows the minimum turning condition of the conventional forklift. It is a schematic top view which shows the minimum turning condition of the conventional forklift.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Car body 2 Front wheel 3 Rear wheel 4 Mast 5 Fork 6 Handle 7 Brake / accelerator pedal 20 Drive motor 30 Support shaft 31 Wheel shaft 32 Caster part 33 Ball bearing part 34 Slide bearing part 34a Shaft part 34b Disk 35 Compression coil spring 36 Block member 37 Adjustment Motor

Claims (6)

In a forklift with a pair of front and rear wheels on the left and right,
Each front wheel is a drive wheel to which forward and reverse rotational driving forces are individually given by mutually independent drive motors, and each rear wheel is rearward with respect to the traveling direction with reference to a pair of left and right support shafts. A forklift, characterized in that it is a caster that can turn individually around each of the support shafts so that each wheel shaft is located.   2. The forklift according to claim 1, wherein when the traveling direction is reversed, a driving force applied to each front wheel by each driving motor is temporarily adjusted.   2. The slide mechanism according to claim 1, further comprising: a slide mechanism that slides from the front to the rear with respect to the traveling direction with respect to each supporting shaft as the wheel shaft of each of the rear wheels is reversed with the reversing of the traveling direction. forklift.   The forklift according to claim 3, further comprising a slide suppression mechanism that suppresses sliding movement of each of the rear wheels with respect to each of the support shafts during traveling.   The forklift according to any one of claims 1 to 4, further comprising a turning suppression mechanism that suppresses turning of each of the rear wheels with respect to each of the support shafts during traveling.   An angle sensor for detecting a turning position of each rear wheel with respect to each support shaft is provided, and during running, the fluctuation frequency of the turning angular velocity calculated based on the detection result by the angle sensor has a predetermined reference value. The forklift according to any one of claims 1 to 5, wherein when it exceeds, a driving force applied to each front wheel from each driving motor is reduced.

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