JPH11321266A - Reach forklift truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve traveling performance within a range of ensuring lateral stability at the time of turning by suitably regulating tilting of a vehicle body at the time of turning according to a center-of-gravity position in the longitudinal direction of the vehicle gravity center. SOLUTION: A drive wheel 13 and a caster wheel 14 are supported on a vehicle body by rear wheel support mechanism comprising link mechanism 29 actuated to allow tilting of the vehicle body. The rear wheel support mechanism is provided with a damper 53 that can regulate or allow the actuation of the link mechanism 29 and is provided with a solenoid selector valve 58 controlled by a control unit 69. The control unit 69 regulates the actuation of the link mechanism 29 on the basis of the respective judgment values set to a load lift height position H, load W and lateral acceleration G corresponding to centrifugal force that is about to tilt the vehicle body at the time of turning, so as to prevent tilting of the vehicle body at the time of turning. When a center-of-gravity position Sg obtained from the load W and the reach position of a mast device 15 is on the front wheel axle side, the control unit 69 regulates the actuation of the link mechanism 29 on the basis of the lateral acceleration judgment value set to a larger value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reach forklift, and more particularly, to a reach forklift in which rear wheels are supported to allow a vehicle body to tilt.

[0002]

2. Description of the Related Art A reach forklift is a vehicle for transporting a relatively light load in a small factory or the like. For this reason, the reach forklift has driven wheels as front wheels at the ends of a pair of left and right reach legs, respectively, and has one drive steering wheel as a rear wheel. As a result, the overall length of the vehicle body is made as short as possible and the minimum turning radius is made small, so that the transfer operation in a narrow space can be performed easily.

In a reach forklift, the longitudinal length of the machine base is shortened, and a mechanism for driving and steering the drive steered wheels occupies a large portion in the machine base. The driver's seat is provided at a position deviated to the side opposite to the drive steered wheels, while being provided at a position deviated to the side from the vehicle.

In a forklift, the position of the center of gravity of the vehicle center of gravity in the vehicle front-rear direction changes depending on the magnitude of the load. In particular, in the reach forklift, the reach state of the mast, that is, the mast moves farthest from the front side of the vehicle The position of the center of gravity of the vehicle center of gravity in the vehicle front-rear direction greatly changes depending on whether the vehicle is in the arranged reach state or the non-reach state in which the mast is moved and arranged most rearward of the vehicle. As a result, the contact pressure of the drive steered wheels greatly changes according to the position of the center of gravity. That is, when the mast is in the non-reach state without loading, the center of gravity of the vehicle moves to the rearmost side, and the ground pressure of the steered wheels becomes the largest.
Conversely, when the mast is brought into the reach state by loading a load of an allowable limit, the center of gravity of the vehicle moves to the front side, and the contact pressure of the drive steered wheels becomes minimum. At this time, if the ground contact load of the driven wheels is too large, the steering force may be too large, and the reliability of the drive system may be reduced. Conversely, if the ground pressure of the driven wheels is too small, slippage occurs and the driving force cannot be efficiently transmitted to the road surface. In addition, depending on the fork's elevation position or the tilt angle when the tilt mechanism is attached to the fork,
The position of the center of gravity does not change so much.

For this reason, as shown in FIG. 24, the reach forklift is provided with caster wheels (auxiliary wheels) 91 which constitute rear wheels in parallel with the drive steering wheels 90 on the driver's seat side. Some vehicles include a rear wheel support mechanism 94 that is supported on a vehicle body frame 93 in a state where the wheel 91 is connected to a wheel 91 by a link mechanism 92. The drive steering wheel 90 is connected to the body frame 93 and the upper link 95 of the link mechanism 92.
Are urged toward the road surface by a suspension spring 96 provided therebetween. On the other hand, the caster wheel 91
Is supported via a caster spring 99 on a support plate 98 fixed to a portion of the lower link 97 extending from the fixed shaft 97a side to the driver's seat side. Drive steering wheel 9
Numeral 0 is pressed against the road surface by the urging force of the suspension spring 96 and the urging force of the caster spring 99, and the caster wheel 91 is pressed against the road surface only by the urging force of the caster spring 99.

When the mast is in a non-reach state and the ground pressure of the drive steering wheel 90 increases, the drive steering of the caster wheel 91 is performed by the operation of the link mechanism 92 based on the compression operation of the caster spring 99 and the suspension spring 96. The ring 90 relatively moves upward by a small amount. As a result, the weight of the rear portion of the vehicle is not biased to the drive steering wheel 90, and the contact pressure of the drive steering wheel 90 does not become excessive.

On the other hand, when the mast is in a reach state and the contact pressure of the drive steering wheel 90 is reduced, the caster spring 99 and the suspension spring 96 are actuated by the link mechanism 92 based on the extension operation, so that the caster wheel 9 is moved.
The drive steering wheel 90 relatively moves slightly downward by a small amount. As a result, the weight on the rear side of the vehicle is not biased to the caster wheels 91, and the contact pressure of the drive steering wheels 90 does not become too small.

In such a rear wheel support mechanism 94,
Since the drive steering wheel 90 is supported by the vehicle body in a state in which vibration is absorbed by the suspension spring 96, road followability during traveling on uneven road surfaces is improved, and driving force can be transmitted efficiently and traveling performance is improved. I do. Further, since the drive steering wheel 90 and the caster wheel 91 are supported in a state of absorbing vibration, vibration of the vehicle body can be suppressed when traveling on an uneven road surface, so that riding comfort can be improved.

Further, even when the vehicle body is tilted during turning, the link mechanism 92 is operated during turning to the left so that the drive steering wheel 90 is pushed down to the road surface side by the suspension spring 96 so that the ground contact pressure is secured, and the driving force is increased. It is transmitted efficiently. At the time of turning right, the link mechanism 92 is operated and the drive steering wheel 90 is supported by the suspension spring 96 in a state of absorbing vibration, and the road following ability when traveling on uneven road surface is improved, and the driving force is transmitted efficiently. And ride comfort is improved.

[0010] By the way, the vehicle provided with such a rear wheel support mechanism 94 has an excessive centrifugal force for tilting the vehicle body based on the lateral acceleration at the time of turning, or a state in which the load is lifted. When a moment load acting to tilt the vehicle body is applied due to the position of the vehicle center of gravity in the vertical direction, the link mechanism 92 operates and the suspension spring 96 contracts, or the caster spring 99 contracts to tilt the vehicle body. Permissible.
In other words, when the vehicle body tilts, the drive steering wheel 9 on the rear wheel side is used.
Zero or a contact pressure that counteracts the force of the caster wheel 91 sinking due to sinking is not immediately generated. as a result,
There is a possibility that the vehicle body may be largely tilted and the center of gravity of the vehicle may be shifted from the left-right center of the vehicle to the left and right sides, and the vehicle may be in an unstable state.

In order to solve such a problem, the present applicant has made the following proposal. First, Japanese Unexamined Patent Publication
In the suspension device disclosed in Japanese Patent Publication No. 191251, a double-acting hydraulic cylinder is provided between the upper link 95 and the vehicle body frame 93, and the oil chambers communicate with each other through an oil passage. An electromagnetically operated on-off valve for allowing or shutting off the movement of the hydraulic oil in the above is provided. When the lateral acceleration applied to the vehicle at the time of turning is detected by the lateral acceleration sensor, and the detected lateral acceleration is less than a predetermined determination value, and the lateral stability of the vehicle is sufficiently secured,
The operation of the link mechanism 92 is allowed by allowing the hydraulic cylinder to expand and contract, and the traveling performance and riding comfort are ensured. On the other hand, when the lateral acceleration is equal to or greater than the determination value and the lateral stability of the vehicle is not sufficient, the expansion and contraction operation of the hydraulic cylinder is regulated to regulate the operation of the link mechanism 92 to secure the lateral stability of the vehicle. I have.

The suspension device disclosed in Japanese Patent Application Laid-Open No. 6-191250 is provided with a hydraulic cylinder and an electromagnetic on-off valve similar to those of the above-mentioned suspension device.
When the vehicle speed is detected by the vehicle speed sensor and the detected vehicle speed is equal to or less than the predetermined determination value and the ride comfort does not matter, the expansion and contraction operation of the hydraulic cylinder and the operation of the link mechanism 92 are restricted to control the operation of the cargo handling operation. Ensure the vehicle's left-right stability. On the other hand, when the vehicle speed exceeds the determination value and the traveling performance and the riding comfort of the vehicle become a problem, the operation of the hydraulic cylinder is allowed to allow the operation of the link mechanism 92, and the riding comfort when the cargo work is not performed is improved. We are trying to secure.

[0013]

By the way, in the reach forklift, the axle of the driven wheels of the front wheels is
3 and the drive steering wheel 90 and the caster wheel 91 are supported by the rear wheel support mechanism 94 so as to allow the vehicle body to swing. Therefore, in a state where the operation of the link mechanism 92 is permitted, when the vehicle center of gravity is located on the vehicle rear side of the predetermined position between the front wheel axle and the rear wheel axle, the center of gravity position is at the predetermined position. Left and right stability is lower than that, and the vehicle body is more likely to tilt due to centrifugal force during turning or moment load during cargo handling work. Conversely, when the center of gravity of the vehicle is on the front side of the vehicle with respect to the predetermined position, the left-right stability is higher than when the position of the center of gravity is at the predetermined position, and the vehicle body is less likely to tilt.

As in the above-described suspension device, the link mechanism 9 is used with the same determination value of the lateral acceleration regardless of the position of the center of gravity.
In order to prevent the tilting of the vehicle body at the time of turning by restricting the operation of Step 2, it is difficult to prevent the tilting of the vehicle body at the time of turning when the center of gravity is relatively rearward by setting the determination value of the lateral acceleration high. That is, if the determination value of the lateral acceleration is set to a low value, it is not possible to obtain good traveling performance and riding comfort at the time of turning when the position of the center of gravity is relatively on the front side.

Further, as in a suspension device described later,
Even in the case where the operation of the link mechanism 92 is restricted with the same determination value for the vehicle speed to prevent a decrease in left-right stability during cargo handling work regardless of the position of the center of gravity, if the determination value of the vehicle speed is set to a high value, the position of the center of gravity becomes It is difficult to suppress the tilting of the vehicle body when turning when the vehicle is relatively behind the vehicle, and when the vehicle speed determination value is set to a low value, good traveling performance and riding comfort are obtained when the center of gravity is relatively in front of the vehicle. You will not be able to get it.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a mast that moves in the front-rear direction of a vehicle and to support a rear wheel so as to allow the vehicle body to tilt. In a reach forklift equipped with a rear wheel support mechanism, the reach forklift is capable of appropriately controlling the tilt of the vehicle body in accordance with the position of the center of gravity of the vehicle center of gravity in the front-rear direction of the vehicle, and improving travelability in a range where left-right stability can be ensured. Is to provide.

Further, in a reach forklift that restricts the operation of the rear wheel support mechanism under a predetermined turning condition and suppresses the tilting of the vehicle body, the tilting of the vehicle body during turning according to the position of the center of gravity of the vehicle center of gravity in the vehicle longitudinal direction is preferable. It is an object of the present invention to provide a reach forklift capable of improving running performance in a range in which left-right stability during turning can be ensured.

Also, in a reach forklift for controlling the tilt of the vehicle body under predetermined loading conditions, the tilt of the vehicle body during the loading operation is preferably restricted according to the position of the center of gravity of the vehicle center of gravity in the longitudinal direction of the vehicle. It is an object of the present invention to provide a reach forklift capable of improving traveling performance in a range where stability can be ensured.

[0019]

SUMMARY OF THE INVENTION In order to solve the above problems, an invention according to claim 1 is provided with two front wheels having a mast moving in the front-rear direction of a vehicle and having a fixed axle, and a fixed axle. A rear wheel support mechanism that includes two rear wheels that are not provided, and that operates to support each of the rear wheels with respect to the vehicle body and to allow the vehicle body to tilt, or to allow the rear wheel support mechanism to operate or An operation restricting means for restricting and permitting or restricting the tilting of the vehicle body, and a turning state amount detecting means for detecting a turning state amount of the vehicle corresponding to a magnitude of a centrifugal force for tilting the vehicle body during turning. Based on a predetermined judgment value for the turning state amount, the operation to restrict the operation of the rear wheel support mechanism when the centrifugal force is equal to or greater than the magnitude corresponding to the judgment value. Tilt control to control regulating means In a reach forklift having a step, a reach position detecting means for detecting a reach position of a mast, a load detecting means for detecting a load of a load loaded on a fork, and the reach position and a load, A center-of-gravity position detecting unit that calculates a center-of-gravity position in the front-rear direction; wherein the tilt control unit is configured such that the center-of-gravity position is a position closer to the front wheel axle than a preset reference position between the front wheel axle and the rear wheel axle. In some cases, the operation restricting means is controlled based on the determination value set for the value of the turning state amount corresponding to a larger value of the centrifugal force than when the position of the center of gravity is at the reference position.

According to a second aspect of the present invention, in the first aspect of the invention, the turning state amount is a lateral acceleration applied to the vehicle at the time of turning, and the turning state amount detecting means is provided to the vehicle at the time of turning. The tilt control means controls the operation restricting means based on the larger determination value set for the lateral acceleration.

According to a third aspect of the present invention, in the first aspect of the present invention, the turning state quantity is a vertical position of the vehicle based on a lifting position of the load and a load,
The turning state amount detecting means includes a lift detecting means for detecting a lift position of a fork, and a load detecting means for detecting a load of a load. The operation restricting means is controlled based on the set larger judgment value.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the turning state amount includes a vertical center of gravity of the vehicle based on a lift position and a load of the load, and a lateral acceleration applied to the vehicle body. Wherein the turning state amount detecting means comprises:
A fork height detecting means for detecting a fork height position, a load detecting means for detecting a load of a load, and a lateral acceleration detecting means for detecting a lateral acceleration applied to a vehicle body; In contrast, the control unit controls the operation restricting unit based on a determination value set to a larger value with respect to a determination value set to a smaller value for a larger value of the load and the lift position.

According to a fifth aspect of the present invention, there is provided a vehicle having a mast that moves in the front-rear direction of a vehicle and has a fixed axle.
A rear wheel support mechanism comprising two front wheels, two rear wheels having an axle not fixed thereto, supporting the rear wheels with respect to a vehicle body, and operating to allow the vehicle body to tilt; An operation restricting means capable of permitting or restricting the operation of the support mechanism to permit or restrict the tilting of the vehicle body, and a magnitude of a moment load for tilting the vehicle body at the time of loading / unloading work based on the vertical position of the vehicle center of gravity. Based on a stable state amount detecting means for detecting a stable state amount of the vehicle and a determination value preset for the stable state amount, the magnitude of the moment load is equal to or greater than the magnitude corresponding to the determination value. And a tilt control means for controlling the operation restricting means so as to restrict the operation of the rear wheel axle support mechanism, the load for detecting the load of the load loaded on the fork. Output means, a reach position detecting means for detecting a reach position of the mast, and a center of gravity position detecting means for detecting a center of gravity of the vehicle center of gravity in the longitudinal direction of the vehicle from the reach position and the load, the tilt control means When the position of the center of gravity is a position closer to the front wheel axle than a reference position set in advance between the front wheel axle and the rear wheel axle, the moment load is smaller than when the position of the center of gravity is at the reference position. The operation restricting means is controlled based on the determination value set to the stable state amount corresponding to a large value.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the stable state quantity is a vertical position of the vehicle center of gravity of the vehicle based on the fork's elevation position and the load of the load. The stable state amount detecting means is a lift detecting means for detecting a lift position of a fork, and a load detecting means for detecting a load of a load, and the tilt control means is provided for the lift position and the load. The operation restricting means is controlled based on the larger judgment value set in the step (1).

According to a seventh aspect of the present invention, in accordance with the fifth or sixth aspect of the present invention, there is provided a loading state detecting means for detecting that the vehicle is in a state of performing a loading operation. The tilt control means prohibits a control for restricting the operation of the rear wheel support mechanism based on the determination value when the vehicle is in a state of performing a loading operation.

According to an eighth aspect of the present invention, in the invention according to the seventh aspect, the loading state detecting means is arranged so that the reach position detecting means and the reach position are within a predetermined range including at least the reach state. And a loading determination means for determining that the vehicle is in the loading state.

(Operation) According to the first aspect of the present invention,
The driving force is efficiently transmitted to the road surface at the time of turning by the two rear wheels supported by the rear wheel support mechanism in a state where the vehicle body is allowed to tilt. The state in which the vehicle body tilts due to the centrifugal force at the time of turning is determined based on the amount of turning state corresponding to the centrifugal force, and the operation of the rear wheel support mechanism is regulated to prevent the vehicle body from tilting. At this time, when the position of the center of gravity of the vehicle center of gravity in the front-rear direction of the vehicle is relatively on the front wheel axle side and the left-right stability of the vehicle is relatively high, until the turning state amount becomes a relatively larger value, the rear wheels The operation of the support mechanism is not restricted, and the traveling performance is improved while maintaining the left-right stability. Conversely, when the center of gravity is located closer to the rear wheel axle and the left-right stability of the vehicle body is relatively low, the operation of the rear wheel support mechanism is restricted when the amount of turning state is relatively smaller, and centrifugal force is applied. The tilting of the vehicle body is restricted, and the left-right stability is improved while running performance is secured.

According to the invention described in claim 2, according to claim 1,
In addition to the operation of the invention described above, the tilting of the vehicle body at the time of turning is determined based on the lateral acceleration proportional to the centrifugal force applied to the vehicle at the time of turning.

According to the invention described in claim 3, according to claim 1
In addition to the operation of the invention described in (1), the tilting of the vehicle body at the time of turning is regulated based on the lift position and the load of the load, which are major factors of the amount of tilting of the vehicle body due to centrifugal force at the time of turning.

According to the fourth aspect of the present invention, the first aspect is provided.
In addition to the operation of the invention described in the above, the vehicle is turned on the basis of the lateral acceleration set in accordance with the load of the load and the lifting position, which is substantially proportional to the magnitude of the centrifugal force for tilting the vehicle body during the turn. The tilting of the vehicle body at is restricted.

According to the fifth aspect of the present invention, the two rear wheels supported by the rear wheel support mechanism in such a manner that the vehicle body is allowed to tilt can ensure road followability when traveling straight on uneven terrain. You. The state in which the vehicle body tilts due to the moment load acting on the vehicle including the same load when the load is lifted in a state where the load is biased left and right during the loading operation is determined based on the stable state amount corresponding to the moment load, Tilt of the vehicle body is prevented by restricting the operation of the rear wheel support mechanism. At this time, when the position of the center of gravity of the vehicle in the front-rear direction of the vehicle is relatively closer to the front axle side and the left-right stability of the vehicle is relatively high, the rear wheels are kept until the stable state amount becomes a relatively large value. The operation of the support mechanism is not restricted, and the traveling performance is improved while maintaining the left-right stability. Conversely, when the position of the center of gravity is closer to the rear wheel axle and the left-right stability of the vehicle body is relatively low, the operation of the rear wheel support mechanism is restricted when the amount of stable state is a relatively small value, and the moment load is applied. The tilting of the vehicle body is restricted, and the left-right stability is improved while running performance is secured.

According to the invention of claim 6, according to claim 5,
In addition to the operation of the invention described in the above, the tilting of the vehicle body during the loading operation is regulated based on the lifting position and the load of the load that determines the magnitude of the moment load based on the vertical position of the center of gravity of the vehicle.

According to the invention of claim 7, according to claim 5,
Or, in addition to the effect of the invention described in claim 6, the position of the center of gravity of the vehicle in the front-rear direction of the vehicle moves to the front wheel axle side,
Even when the operation of the rear wheel support mechanism is not restricted, the operation of the rear wheel support mechanism is surely permitted during a loading operation in which the left-right stability of the vehicle is sufficiently large. Therefore, at the time of loading work,
The operation of the rear wheel support mechanism does not remain restricted while one of the rear wheels is floating above the road surface.

According to the invention of claim 8, according to claim 7,
In addition to the operation of the invention described in (1), the state of loading is determined from the reach position of the mast detected to obtain the position of the center of gravity.

[0035]

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIGS. 2 and 3, a reach forklift 10 according to the present embodiment has a vehicle body 11 in which two driven wheels 12 as front wheels and one drive steering wheel (hereinafter, drive wheel) as rear wheels. 13). Both driven wheels 12
They are fixed on the same axle. The drive wheels 13 are provided at positions deviated leftward from the left and right centers of the vehicle body. A caster wheel (auxiliary wheel) 14 is provided on the same axle as the drive wheel 13 on the right lateral side of the drive wheel 13. In the present embodiment, a rear wheel is constituted by the drive wheel 13 and the caster wheel 14.

The forklift 10 has a mast device 15 on the front side of the vehicle body 11. The mast device 15 includes an outer mast 16a, an inner mast 16b, a lift cylinder 17, a lift bracket 18, a fork 19, and the like. The mast device 15 is provided movably in the front-rear direction along the left and right reach legs 20 by a reach cylinder (not shown).

A driver's seat 21 is provided at the rear of the vehicle body 11. A steering wheel 23 is provided on an upper surface of a storage box 22 provided on the left side of the driver's seat 21. An operation lever 25 for cargo handling operation and accelerator operation is provided on an instrument panel 24 in front of the driver's seat 21.

FIG. 4 shows the rear wheel support mechanism 26.
The rear wheel support mechanism 26 includes a drive unit 27 that drives and steers the drive wheels 13, and a link mechanism 29 that supports a caster unit 28 having the caster wheels 14 on the vehicle body frame 11 a. The link mechanism 29 is connected to the vehicle body 1
1 is allowed to operate.

The link mechanism 29 includes an upper link 30, a lower link 31, a connector 32, and a caster link 33. Each link 30-33 is connected by four axes 34-37 located at the vertices of a quadrilateral.

The upper link 30 is disposed so as to extend slightly above the drive wheel 13, and the right end thereof is rotatably connected to the vehicle body frame 11a by a fixed shaft 34. The lower link 31 is disposed so as to extend substantially horizontally obliquely below the upper link 30, and is rotatably connected to the vehicle body frame 11 a by a fixed shaft 35 located at the center of the lower link 31. The left end of the upper link 30 and the left end of the lower link 31 are relatively rotatably connected to both ends of a substantially L-shaped connector 32 extending substantially vertically by shafts 36 and 37, respectively.

The caster unit 28 includes the lower link 3
The caster link 33 is disposed substantially horizontally on the right side of the lower surface side of the device 1. The caster link 33 is supported rotatably about a shaft 35 in a state where the right end is inserted through a guide shaft 38 attached to the right end of the lower link 31. The left end of the caster link 33 is rotatably connected to a fixed shaft 35. A pair of front and rear caster springs 39 are interposed between the lower link 31 and the caster links 33. The pair of caster wheels 14 is supported by a rotation mechanism (not shown) with respect to the caster link 33 so as to be rotatable in a horizontal plane. As shown in FIG. 5, each of the links 30, 31, and 33 is formed in a substantially U-shape having two arms facing each other at a predetermined distance in the front-rear direction. Are provided as a pair.

As shown in FIGS. 1, 4, and 5, between the support member 40 fixed to the body frame 11a and the upper surface of the connector 32, the connector 32 of the link mechanism 29 is connected to the body frame 11a. A suspension spring 41 biasing downward is interposed.

The drive unit 27 has a drive motor 42, and a shaft 36 connecting the upper link 30 and the connector 32 is connected to a support 43 to which the drive motor 42 is fixed. In the lower part of the support 43,
A gear box 44 is attached so as to be relatively rotatable in a horizontal plane, and the drive wheel 13 is supported on an output shaft (not shown) extending from the gear box 44.

As shown in FIG. 6, a gear wheel 45 is fixed to the upper part of the gear box 44,
5 is meshed with a gear 46a provided at the lower end of the steering shaft 46.

A power steering motor 47 is provided near the steering shaft 46, and power from an output shaft of the motor 47 is introduced into a gear box 48 in which a lower portion of the steering shaft 46 is accommodated.
When the motor 47 is driven in accordance with the operation of the steering wheel 23, the steering force is reduced. The steering wheel 23 and the steering shaft 46 are connected to each other by a shaft 49 connected via a universal joint 50.

The suspension spring 41 has a purpose of pressing the driving wheel 13 against the road surface to secure the ground pressure, and the spring constant is set relatively strong. On the other hand, the caster spring 39 is provided for the purpose of absorbing vibration from the road surface, and the suspension spring 4
It has a spring constant weaker than that of 1. For this reason, during straight running, the input from the caster wheel 14 is transmitted to the lower link 31 after the caster spring 39 has contracted to a predetermined length.

As shown in FIG. 4, a damper 53 comprising a double-acting hydraulic cylinder is provided between a support plate 51 extending horizontally from the support base 43 and a support member 52 extending horizontally from the body frame 11a. It is interposed. The damper 53 has a cylinder 54 connected to the support member 52 at a base end thereof, and a piston rod 55 connected to the support plate 51.

The cylinder 54 has two oil chambers partitioned by a piston 56, and each of the oil chambers is connected to a pipe 57a, 57, respectively.
7b is connected to two ports of the electromagnetic switching valve 58. The electromagnetic switching valve 58 is a two-port two-position switching valve, and includes an electromagnetic solenoid 58a that shuts off communication between the two ports during demagnetization. An accumulator 59 for storing hydraulic oil is connected to a pipe 57c branched from the pipe 57b, and a check valve 6 is provided downstream of the accumulator 59.
0 is provided. A throttle valve 6 is provided on the pipe line 57b.
1 is provided.

When the spool (not shown) of the electromagnetic switching valve 58 is switched to the shut-off position shown in FIG. 4, the dampers 53 communicate with the flow paths 57a and 57 communicating the two oil chambers of the cylinder 54.
7b is shut off, and the piston rod 55 enters a locked state in which expansion and contraction is restricted. When the spool of the electromagnetic switching valve 58 is switched from the shut-off position to the communication position, the two chambers of the cylinder 54 are communicated via the flow paths 57a and 57b, and the damper 53 is allowed to expand and contract the piston rod 55. It becomes a free state.

As shown in FIGS. 1 and 4, a steering angle sensor 62 is provided near the gear wheel 45 as a steering angle detecting means for detecting the steering angle (tire angle) θ of the drive wheel 13. . A magnetic sensor 64 is provided above the drive motor 42 as vehicle speed detecting means for detecting the rotation of the disk brake 63 rotating integrally with the drive wheel 13 and indirectly detecting the vehicle speed V. Lift cylinder 1
In the vicinity of 7, a pressure sensor 65 is provided as load detecting means for detecting the oil pressure of the oil chamber of the lift cylinder 17 corresponding to the load W of the load loaded on the fork 19. Further, the lift cylinder 17 is provided with a reel-type rotational displacement sensor 66 as a lift detecting means for detecting the lift position of the fork 19. In addition, a displacement sensor 67 is provided near the reach cylinder as reach position detecting means for detecting the reach position of the mast device 15.

Further, a steering angle sensor 62, a magnetic sensor 64, a pressure sensor 65, a rotational displacement sensor 66, and a displacement sensor 67 are electrically connected to the inside of the vehicle body 11a and also electrically connected to an electromagnetic solenoid 58a. A control unit 69 is provided.

Next, the electrical configuration of the vehicle body swing control device provided in the reach forklift 10 will be described with reference to the electrical block diagram of FIG. The steering angle sensor 62 is connected to the driving wheel 1.
The digitally encoded binary steering angle data Dθ having a value corresponding to the steering angle θ of 3 is output to the control unit 69. The magnetic sensor 64 outputs a digital vehicle speed signal PV having a pulse width corresponding to the vehicle speed V to the control unit 69.
The pressure sensor 65 outputs an analog load signal SW corresponding to the load W of the load loaded on the fork 19 to the control unit 69. The rotational displacement sensor 66 outputs an analog lift signal SH corresponding to the lift position H of the fork 19.
Is output to the control unit 69. The displacement sensor 67 determines the reach position Sr of the mast device 15 between a reach state in which the mast device 15 is reached most toward the front of the vehicle and a non-reach state in which the mast device 15 is returned most toward the rear of the vehicle. It continuously detects and outputs a digital mast position signal PS corresponding to the detected position to the control unit 69.

The control unit 69 includes a microcomputer 70, A / D converters 71 and 72, and a solenoid drive circuit 74. The microcomputer 70 includes a central processing unit (hereinafter, CPU) 75, a read-only memory (ROM) 76, a writable and readable memory (RAM) 77, an input interface 78, and an output interface 79. In this embodiment, the operation restricting means is constituted by the damper 53, the electromagnetic switching valve 58, and the like. A lateral acceleration detecting means is constituted by the steering angle sensor 62, the magnetic sensor 64 and the microcomputer 70, and the steering angle sensor 62, the magnetic sensor 64,
The pressure sensor 65, the rotational displacement sensor 66 and the microcomputer 70 constitute a turning state quantity detecting means, and the pressure sensor 65, the displacement sensor 67 and the microcomputer 70 constitute a center of gravity position detecting means.

The CPU 75 determines the steering angle data Dθ output from the steering angle sensor 62, the vehicle speed signal PV output from the magnetic sensor 64, the detected value of the load W output from the pressure sensor 65 via the A / D converter 71, and the rotation. A detected value of the elevation position H output by the displacement sensor 66 via the A / D converter 72, and
Reach position S output by the displacement sensor 67 as a digital signal
The detected values of r are input via the input interface 78, respectively. The CPU 75 outputs an exciting current Ie for exciting the electromagnetic solenoid 58a to the output interface 79.
Is output to the solenoid drive circuit 74 via the.

The ROM 76 stores various program data including the program data of the swing control processing shown in the flowcharts of FIGS. The swing control process is to prevent the tilting of the vehicle body 11 due to the centrifugal force at the time of turning of the vehicle by restricting the operation of the link mechanism 29 and prevent the stability of the vehicle in the left-right direction (hereinafter referred to as left-right stability). This is the control to be performed. The CPU 75 repeatedly executes the swing control process at predetermined time intervals (for example, several tens of milliseconds).

The CPU 75 determines whether the steering direction of the steered wheels 13 is right steering or left steering based on the detected steering angle θ as the swing control processing. The ROM 76 stores a map M1 for detecting the turning direction of the vehicle from the steering direction of the steered wheels 13 and the detected steering angle θ. As shown in FIG. 8, the map M1 is set so as to obtain a turning radius r with respect to the steering angle θ for each of the left and right turning directions. This is reach forklift 1
At 0, the drive wheels 13 are offset in the vehicle width direction. In other words, the turning radius is larger when the drive wheel 13 turns right as the turning outer wheel than when the drive wheel 13 turns left as the turning inner wheel. The CPU 75
In the swing control process, a turning radius r is obtained for each turning direction using the map M1 based on the detected steering angle θ.

The CPU 75 determines the lateral acceleration G from the detected steering angle θ and the vehicle speed V as the swing control processing. C
The PU 75 calculates the lateral acceleration G using the turning radius r obtained from the steering angle θ and using the following equation (1).

G = V ² / r (1) The ROM 76 stores lateral acceleration determination values G 1, G 2, which serve as references for determining whether or not to restrict the operation of the link mechanism 29 based on the calculated lateral acceleration G. G3, G4 are set, and maps M2, M3, M4, M5 in which the conditions of the load W and the elevation position H when using the respective lateral acceleration determination values G1, G2, G3, G4 are stored. I have. The maps M2 and M3 are used at the time of a right turn in which a lateral acceleration G in the left direction occurs, and as shown in FIGS. 9A and 9B, the loading state based on the load W and the lifting position H. , The lateral acceleration determination values G1 and G2 are set. In this embodiment, the lift position H of the fork 19 is detected in a range of 0 to 3 m. The maps M4 and M5 are used at the time of a left turn in which a rightward lateral acceleration is generated. As shown in FIGS. 10 (a) and 10 (b), the loading state based on the load W and the lifting position H is shown. To the lateral acceleration determination values G3, G4
Is set.

The CPU 75 performs a swing control process based on a judgment value preset for a turning state amount of the vehicle corresponding to the magnitude of the centrifugal force for tilting the vehicle body 11 when the vehicle turns. When the centrifugal force is equal to or greater than the magnitude corresponding to the determination value, the operation of the link mechanism 29 is restricted. In the present embodiment, the turning state quantity is the load W of the load.
And the vertical center of gravity of the vehicle center of gravity based on the vertical position H and the lateral acceleration G applied to the vehicle body 11. Then, the CPU 75 executes the map M2
Using M5, the lateral acceleration determination values “0”, G1, G2 set according to the load W and the elevation position H are obtained, and the link mechanism is determined based on the lateral acceleration determination values “0”, G1, G2. 29 operation is regulated. When the load W is less than the load determination value W0, the map M2 indicates that the lift position H is equal to the lift determination value H0 based on the lift determination value H0 set for the lift position H.
If it is less than the lateral acceleration determination value G2, the lateral acceleration determination value G2 is set to a value smaller than the lateral acceleration determination value G2 when the lift position H is equal to or greater than the lift determination value H0.
1 is set. This is because, even if the load W is the same, the higher the lift position H is, the more the vehicle body 11 tilts with respect to the same lateral acceleration G. In the present embodiment, the lift determination value H0 is set to 1.5 m.

On the other hand, the map M3 indicates that the load W is equal to the load determination value W.
When 0 or more, the lateral acceleration determination value G2 is set when the height position H is less than the height determination value H0 based on the height determination value H0, and when the height position H is equal to or greater than the height determination value H0. In some cases, “0” is set as the lateral acceleration determination value. This is because even if the lifting position H is the same,
This is because the larger the load W, the more the vehicle body 11 tilts at the same lateral acceleration.

The lateral acceleration determination values G3, G4 when turning left
Are set such that different lateral acceleration determination values G3 and G4 are set according to the load determination value W0 set for the load W of the load. The map M4 sets the lateral acceleration judgment values G3, G4 when the load W is less than the load judgment value W0, and the map M5 sets the lateral acceleration judgment values G3, G4 when the load W is equal to or more than the load judgment value W0.

When the load W is less than the load determination value W0, the map M4 is based on the lift determination value H0. When the lift position H is less than the lift determination value H0, the lateral acceleration determination value G4 is obtained.
Is set, and when the lift position H is equal to or higher than the lift determination value H0, the lateral acceleration determination value G3 set to a value smaller than the lateral acceleration determination value G4 is set. on the other hand,
The map M5 indicates that when the load W is equal to or greater than the load determination value W0, the lift position H is based on the lift determination value H0.
When it is less than 0, the lateral acceleration determination value G4 is set, and when the lift position H is equal to or higher than the lift determination value H0, "0" is set as the lateral acceleration determination value.

This is because the reach forklift 10 restricts the operation of the link mechanism 29 when the body 11 tilts leftward due to the contraction of the suspension spring 41 due to the centrifugal force in the left direction during the right turn. This is because the timing of restricting the operation of the link mechanism 29 when the vehicle body 11 tilts rightward due to the contraction of the caster spring 39 due to the rightward centrifugal force at the time of rotation is delayed until the caster spring 39 is almost contracted. For example, when the vehicle turns right when the load W is less than the load determination value W0 and the lift position H is equal to or greater than the lift determination value H0, the link mechanism 29 is moved when the lateral acceleration G becomes equal to the lateral acceleration determination value G1.
Operation is regulated. Similarly, at the time of the left turn when the load W is less than the load determination value W0 and the lift position H is equal to or greater than the lift determination value H0, the caster spring 39 is not fully contracted at the time of the lateral acceleration determination value G1, and the caster spring 39 The operation of the link mechanism 29 is restricted at the time when the lateral acceleration determination value G3 is reduced.

The CPU 75 performs the swing control process by using the maps M2 to M5 in accordance with the loading conditions based on the lifting position H and the load W for each turning direction, and using the lateral acceleration determination values G1 to G5.
Set G4. Then, as the swing control processing, the CPU 75 determines the calculated lateral acceleration G based on the set lateral acceleration determination values G1 to G4. If the lateral acceleration G is equal to or greater than the respective lateral acceleration determination values G1 to G4, the link is performed. Mechanism 29
The lateral acceleration G is controlled by the lateral acceleration determination values G1 to G1.
When it is less than G4, the operation of the link mechanism 29 is permitted.

The CPU 75 calculates the yaw rate change rate ΔY / ΔT from the detected steering angle θ and vehicle speed V and the turning radius r using the following equation (2). ΔY / ΔT = V · {Δ (1 / r) / ΔT} (2) Here, Δ (1 / r) is a predetermined time ΔT of reciprocal value 1 / r of turning radius r (for example, several tens of milliseconds) ) Per change (deviation). The deviation Δ (1 / r) is obtained by reading the steering angle θ1 before the predetermined time ΔT from the data of the steering angles θ for a plurality of past times (predetermined time ΔT is one time) stored in the RAM 77, and reading the steering angle θ1 Is calculated from Δ (1 / r) = | 1 / r−1 / r1 | using the turning radius r1 determined from

Here, the yaw rate change rate ΔY / ΔT is
An equation representing the yaw rate Y is expressed by the following equation (3) obtained by time-differentiating Y = V / r. ΔY / ΔT = V · ｛Δ (1 / r) / ΔT｝ + (1 / r) · ｛ΔV / ΔT｝ (3) While the reach forklift 10 is turning, the time Δ
Since the vehicle speed V at T can be regarded as substantially constant, in the present embodiment, the expression (2) approximated by ignoring the latter term in the expression (3) is adopted as an arithmetic expression for estimating the ΔY / ΔT value.

The ROM 76 stores a yaw rate change rate determination value y0 preset for the calculated yaw rate change rate ΔY / ΔT. The yaw rate change rate determination value y0 is set for a right turn when a leftward lateral acceleration occurs, and an infinite value is set for a leftward turn when a rightward lateral acceleration occurs. That is, when turning left, the yaw rate change rate ΔY / ΔT is not considered. This is because the caster spring 3
This is because the operation of the link mechanism 29 is not restricted until the length of the link mechanism 9 is reduced to a predetermined length.

As a swing control process, the CPU 75 determines the calculated yaw rate change rate ΔY / ΔT based on the yaw rate change rate determination value y0 when turning right, and determines the yaw rate change rate ΔY / ΔT as the yaw rate change rate. If the rate determination value y0 or more, the operation of the link mechanism 29 is regulated, and the yaw rate change rate ΔY / ΔT is changed to the yaw rate change rate determination value y.
When it is less than 0, the operation of the link mechanism 29 is permitted.

The ROM 76 stores maps M6 and M7 for determining the center of gravity Sg of the vehicle center of gravity in the front-rear direction of the vehicle from the detected load W and the reach position Sr. As shown in FIG. 11 and FIG.
6 and M7, the load W is different when the mast device 15 is in the reach state in which the mast device 15 is closest to the vehicle front and when the mast device 15 is in the non-reach state in which the mast device 15 is returned most rearward in the vehicle.
From the center of gravity Sg. As shown in FIG. 13, the center of gravity position Sg is represented by a position where the intersection with the front wheel axle is 0 and the rear wheel axle side is positive on coordinate axes provided in the front-rear direction at the left and right center of the vehicle. The map M6 is used to set the center of gravity position Sg according to the load W when the mast device 15 is in the reach state, and the map M7 is used to set the center of gravity position according to the load W when the mast device 15 is in the non-reach state. Used to set Sg. This is reach forklift 10
In this case, the center of gravity position Sg moves in the front-rear direction of the vehicle in accordance with the magnitude of the load W, and the center of gravity position Sg greatly moves depending on whether the mast device 15 is in the reach state or the non-reach state. is there. When the load W is the same, the center of gravity position Sg hardly changes even if the lift position H changes. Therefore, the position of the center of gravity Sg is determined only from the load W and the position of the mast device 15.

The CPU 75 executes maps M6, M7 based on the detected load W and reach position Sr as swing control processing.
Is used to determine the position of the center of gravity Sg. And the CPU 75
Indicates that, as the swing control processing, when the obtained center of gravity position Sg is located on the front wheel axle side (not including the point A) from the point A as a reference position set at an intermediate point between the front wheel axle and the rear wheel axle on the coordinate axes. A lateral acceleration determination value (in the present embodiment, a turning state quantity corresponding to a larger value of the centrifugal force than when the center of gravity position Sg is on the rear wheel axle side (including point A) from point A). (Infinity) to restrict the operation of the link mechanism 29. That is, when the position of the center of gravity Sg is on the front wheel axle side from the point A, the CPU 75 does not restrict the operation of the link mechanism 29 based on the lateral acceleration G.

That is, in this embodiment, the vertical center of gravity of the vehicle based on the lifting position H and the load W of the load, and the lateral acceleration G applied to the vehicle body 11 during turning are detected as turning state quantities. You. Then, the CPU 75 sets the load W
And a larger value (lateral acceleration determination value G) for a determination value (G1 for G2 and “0” for G1) set to a smaller value for a larger value of the lifting position H.
For 1, G2, and “0”, control is performed to restrict the operation of the link mechanism 29 based on a determination value that does not consider the lateral acceleration determination value, that is, the lateral acceleration determination value is infinite.

This is because the axles of the driven wheels 12 are fixed to the vehicle body 11 and the drive wheels 13 and the caster wheels 14 are supported by the rear wheel support mechanism 26 so as to allow the vehicle body 11 to tilt left and right. This is because the more the position Sg of the vehicle center of gravity in the front-rear direction of the vehicle is closer to the front wheel axle, the greater the lateral stability of the vehicle. When the left and right stability is sufficiently large without restricting the operation of the link mechanism 29 during the turning of the vehicle, the operation of the link mechanism 29 is allowed to secure the ground pressure of the drive wheels 13 during the left turn, thereby obtaining the driving force. Is transmitted efficiently, and the driving wheel 13 is supported in a state of absorbing vibration when turning right so that the driving force is efficiently transmitted during uneven running. In addition, the driving wheel 3 is supported in a state of absorbing vibration during a right turn, thereby improving riding comfort.

The microcomputer 71 sets the flag F
g, Fy, Fs, and FL. The CPU 75 sets the flag Fg to “1” when the calculated lateral acceleration G is equal to or more than each of the determination values G1, G2, G3, and G4 according to the turning direction, and sets the flag Fg to “1” otherwise. 0 ". When the yaw rate change rate ΔY / ΔT is equal to or greater than the determination value yo during the right turn, the CPU 75 sets the flag F
y is set to “1”, otherwise the flag Fy is set to “0”
And The CPU 75 sets the flag Fs to “1” when the position of the center of gravity Sg is greater than or equal to A, and sets the flag Fs to “0” when the position of the center of gravity Sg is less than A. And C
The PU 75 sets the flag FL to “1” when at least one of the flag Fg and the flag Fy is “1” and the flag Fs is “1”, and sets the flag FL to “0” otherwise. I do.

Next, the operation of the vehicle body swing control device will be described with reference to FIG.
This will be described with reference to the flowchart of the swing control process shown in FIG. In the swing control process, the CPU 75 first
In step (hereinafter, S) 100, each data of the steering angle θ, the vehicle speed V, the load W, the elevation position GH, and the reach position Sr is read. Next, in S110, the CPU 75 determines from the steering angle θ whether the vehicle is turning right, turning left, or traveling straight.

When the CPU 75 determines in S110 that the vehicle is turning right, in S120, the turning radius r is obtained from the steering angle θ using the map M1. Next, the CPU 75
Is the lateral acceleration G from the vehicle speed V and the turning radius r in S130.
The yaw rate change rate ΔY / ΔT is calculated from the vehicle speed V and the turning radius r in S140.

At S150, CPU 75 determines whether or not yaw rate change rate ΔY / ΔT is equal to or greater than yaw rate change rate determination value y0. When the yaw rate change rate ΔY / ΔT is equal to or greater than the yaw rate change rate determination value y0, the CPU 75 sets the flag Fy to “1” in S160, and when the yaw rate change rate ΔY / ΔT is less than the yaw rate change rate determination value y0. Sets the flag Fy to "0" in S170.

Next, the CPU 75 determines in step S180 that the load W
When the load W is less than the load determination value W0 from the lift position H, the lift position H is determined using the map M2.
Whether the lateral acceleration G is greater than or equal to the lateral acceleration determination value G2 when less than 0, or whether the lateral acceleration G is greater than or equal to the lateral acceleration determination value G1 when the lift position H is greater than or equal to the lift determination value H0. Determine whether or not. When the load W is equal to or greater than the load determination value W0 in S180, the CPU 75 uses the map M3 when the load W is equal to or greater than the load determination value W0. Is greater than or equal to the lateral acceleration determination value G2, or the lift position H is equal to the lift determination value H
When the value is 0 or more, it is determined whether the lateral acceleration G is not less than the lateral acceleration determination value G1.

When the lateral acceleration G is equal to or greater than the lateral acceleration determination value G1 or G2 in S180,
In S190, the flag Fg is set to “1”, and when the lateral acceleration G is less than the lateral acceleration determination value G1 or G2,
At 200, the flag Fg is set to “0”.

On the other hand, when the CPU 75 determines in S110 that the vehicle is turning left, in S210, the CPU 75 obtains a turning radius r during left turning from the steering angle θ using the map M1. Then, in S220, the CPU 75 calculates the lateral acceleration G from the obtained turning radius r and the vehicle speed V.

In step S230, when the load W is smaller than the load determination value W0 from the load W and the lift position H, the CPU 75 uses the map M4 to determine the lateral acceleration when the lift position H is smaller than the lift determination value H0. It is determined whether or not G is equal to or greater than the lateral acceleration determination value G4, or whether or not the lateral acceleration G is equal to or greater than the lateral acceleration determination value G3 when the lift position H is equal to or greater than the lift determination value H0. When the load W is equal to or greater than the load determination value W0 from the load W and the lift position H in S230, the CPU 75 uses the map M5 to determine the lift position H as the lift determination value H0.
Is less than or equal to the lateral acceleration determination value G4, or is the lateral acceleration G greater than or equal to the lateral acceleration determination value G3 when the elevation position H is greater than or equal to the elevation determination value H0. Judge.

When the lateral acceleration G is equal to or larger than the lateral acceleration determination value G3 or G4 in S230,
If the flag Fg is set to “1” in S190 and the lateral acceleration G is less than the lateral acceleration determination value G3 or G4, the process proceeds to S2
At 00, the flag Fg is set to “0”.

Next, in S240, the CPU 75 obtains the center of gravity position Sg from the reach position Sr and the load W using the map M6 or M7. In S250, the obtained center of gravity position Sg is determined from the point A on the coordinate axis by the vehicle rearward. It is determined whether it is the side. The CPU 75 sets the flag Fs to "1" in S260 when the center of gravity position Sg is on the vehicle rear side from the point A, and S270 when the center of gravity position Sg is on the vehicle front side from the point A.
To set the flag Fs to "0".

At S280, the CPU 75 determines that at least one of the flag Fg and the flag Fy is “1”, and
It is determined whether the flag Fs is “1”. CPU7
In step S280, if at least one of the flag Fg and the flag Fy is "1" and the flag Fs is "1", the process proceeds to step S290, where the swing restriction flag FL is set to "1". To end. On the other hand, the CPU 75
Indicates that both the flag Fg and the flag Fy are “0” and the flag Fs is “0” in S280, or that both the flag Fg and the flag Fy are “0”.
, The swing restriction flag FL is set to "0" in S300.
And the process ends.

When the vehicle is traveling straight in S110, the CPU 75 terminates the process. The solenoid drive circuit 74 supplies the exciting current Ie to the electromagnetic solenoid 58a when the swing regulation flag FL is "0", and stops the supply of the exciting current Ie when the swing regulation flag FL is "1".

Therefore, when the load W is equal to or greater than the load determination value W0, the height position H is equal to or greater than the lift determination value H0, and the center of gravity position Sg is on the rear side of the vehicle from the point A, the link mechanism 29 is activated. Is restricted even when the lateral acceleration G is “0”, and the tilting of the vehicle body 11 during turning is prevented as much as possible.

On the other hand, when the load W is equal to or greater than the load determination value W0 and the lift position H is less than the lift determination value H0, or when the load W is less than the load determination value W0, the detected lateral acceleration G However, when turning right, the lateral acceleration determination value G1
Alternatively, the operation is determined based on the lateral acceleration determination value G3 or G4 at the time of G2 or a left turn, and the operation of the link mechanism 29 is regulated so that the tilt of the vehicle body 11 does not exceed a predetermined magnitude.

FIGS. 16 and 17 are graphs showing changes in the lateral acceleration G and the yaw rate change rate ΔY / ΔT during a right turn and a left turn. When the operation of the link mechanism 29 is not regulated and the vehicle turns right from straight ahead while traveling, as shown in FIG. 16, the yaw rate change rate ΔY / Y before the lateral acceleration G reaches the determination value G1. ΔT is the determination value y
By exceeding o, the operation of the link mechanism 29 is regulated earlier. That is, the operation of the link mechanism 29 is regulated almost simultaneously with the start of turning. Therefore, at the time of turning right, as shown in FIG. 18, the operation of the link mechanism 29 is restricted when the vehicle body 11 starts to turn right and is still in a substantially horizontal posture, and the tilting of the vehicle body 11 is restricted. Thereafter, as shown in FIG. 16, the steering angle θ is set to a constant cutoff angle and the yaw rate change rate ΔY / ΔT becomes less than the determination value yo.
The lateral acceleration G is equal to the determination value G1 (when the load W is less than the load determination value W0 and the lift position H is equal to or greater than the lift determination value H0) or G
2 (When the load W is less than the load determination value W0 and the lift position H is less than the lift determination value H0, or when the load W is the load determination value W
When the lift position H is less than or equal to 0 and the lift position H is less than the lift determination value H0) or more, the operation of the link mechanism 29 remains restricted.
Therefore, during the right turn, the link mechanism 29 remains fixed to the vehicle body frame 11a in a substantially horizontal posture as shown in FIG. While the operation of the link mechanism 29 is restricted, the vehicle body 11 leans to the left due to the centrifugal force at the time of turning right, but the caster wheel 14 slightly rises from the road surface, but the ground pressure of the drive wheel 13 is increased. Is secured.

Thereafter, as shown in FIG. 16, when the vehicle shifts from a right turn to a left turn, the lateral acceleration G is momentarily less than the determination value G1 in a section where the direction is switched. However, since the turning direction is being shifted, the yaw rate change rate ΔY / ΔT becomes a value equal to or larger than the determination value yo, and the link mechanism 2 is maintained until the vehicle is temporarily turned straight from the right turning state.
9 remains regulated. Then, when the vehicle shifts from the straight running posture to the left turning state, the yaw rate change rate Δ
The operation of the link mechanism 29 is no longer restricted based on Y / ΔT, and the operation of the link mechanism 29 is allowed.

When the vehicle body 11 tilts to the right due to the rightward centrifugal force in the left turning state, the lateral acceleration G becomes equal to the judgment value G3 (load) when the caster spring 39 is almost contracted to a predetermined length as shown in FIG. W is the load judgment value W0
G4 (when the load W is less than the load determination value W0 and the lift position H is less than the lift determination value H0, or when the load W is the load determination value). (When the lift position H is less than W0 and the lift determination value H is less than H0)
, And the operation of the link mechanism 29 is regulated again. Therefore, when turning left, the vehicle body 11 tilts slightly to the right until the caster spring 39 almost contracts to a predetermined length.
In this process, the operation of the link mechanism 29 is not restricted, and the ground pressure (wheel weight) of the drive wheel 13 and the caster wheel 14 is distributed at a set ratio by the link mechanism 29, so that the ground pressure of the drive wheel 13 is secured. That is, the ground pressure applied to the caster wheels 14 activates the link mechanism 29 to lower the drive wheels 13 with respect to the vehicle body frame 11a, thereby securing the ground pressure.

When the caster spring 39 is almost contracted to a predetermined length, the lateral acceleration G becomes equal to the lateral acceleration determination value G.
3 or G4 or more, the operation of the link mechanism 29 is restricted, and the tilting of the vehicle body 11 is restricted. For this reason, even if the vehicle body 11 is further tilted to the right while the operation of the link mechanism 29 is restricted, the ground pressure of the drive wheels 13 is ensured to be higher than that of the conventional device in comparison with the right tilt angle of the vehicle body 11 at that time. You. Therefore, although the ground pressure of the drive wheel 13 is slightly lowered, the slip does not occur, and the acceleration is not slowed down, the braking effect is not adversely affected, and the steering performance is not reduced so much as to cause a problem.

In this embodiment, when turning left, the timing for locking the link mechanism 29 is later than when turning right as compared with the conventional device. However, in the conventional device, even if the operation of the link mechanism 92 is restricted early, the sinking of the vehicle body to the caster wheel 91 side still occurs until the caster spring 99 contracts to a predetermined length.
Restricting the operation of the link mechanism 92 itself was not so effective for restricting the tilt of the vehicle body 11. Therefore, as in the present embodiment, when the caster spring 39 contracts to the predetermined length during the left turn, the link mechanism 2
Even if the timing of restricting the operation of the vehicle body 9 is delayed,
Is not so large as in the conventional apparatus.

Further, since the caster spring 39 has a small spring constant with respect to the suspension spring 41, it is easily displaced, and the centrifugal force applied to the vehicle body 11 until the caster spring 39 contracts to a predetermined length is relatively small. Since the operation of the link mechanism 29 is restricted after the caster spring 39 has almost contracted to the predetermined length, the amount of tilt of the vehicle body 11 can be small relative to the lateral acceleration G. In other words, in a state where the operation of the link mechanism 29 is restricted, the caster spring 39 is almost completely contracted, and the vehicle body 11 is in a state where it is difficult to sink further into the caster wheel 14 side.
After the operation of the link mechanism 29 is restricted, the vehicle body 11 does not tilt further more, and the contact pressure of the drive wheels 13 is hardly reduced. Accordingly, left-right stability is ensured while suppressing a decrease in the ground pressure of the drive wheels 13.

On the other hand, as shown in FIG. 17, when the vehicle makes a left turn from a straight running state while traveling, the lateral acceleration G is determined when the caster spring 39 is almost contracted to a predetermined length as shown in FIG. Reaches the value G3 or G4,
The operation of the link mechanism 29 is regulated. In the process in which the vehicle body 11 leans slightly to the right until the caster spring 39 is almost contracted to the predetermined length, the link mechanism 29 moves so as to distribute the ground pressure (wheel load) between the drive wheel 13 and the caster wheel 14 at a set ratio. The ground pressure of the driving wheel 13 is secured. After the caster spring 39 is almost fully contracted, the link mechanism 29
Therefore, even if the vehicle body 11 further tilts rightward, the decrease in the contact pressure of the drive wheels 13 is relatively suppressed. Accordingly, left-right stability is ensured while suppressing a decrease in the ground pressure of the drive wheels 13.

Thereafter, when the vehicle shifts from the left turning state to the right turning state, the operation of the link mechanism 29 is permitted when the lateral acceleration G becomes smaller than the judgment value G3 or G4.
When the operation of the link mechanism 29 is permitted, the caster spring 39 moves while the link mechanism 29 moves so as to distribute the ground pressure between the drive wheel 13 and the caster wheel 14 at a set ratio.
Is gradually restored, and the vehicle body 11 returns to the horizontal posture.

During the left turn, the yaw rate change rate ΔY / ΔT
Is not taken into account, so that the value ΔY
Even if /.DELTA.T is equal to or greater than the determination value yo, the operation of the link mechanism 29 is allowed to be allowed until the vehicle enters the straight traveling posture. When the reach forklift 10 begins to shift to the right turning state after passing the straight-ahead posture, the yaw rate change rate ΔY / ΔT has already become a value equal to or greater than the yaw rate change rate determination value yo. At times, the operation of the link mechanism 29 is quickly regulated. The lateral acceleration G becomes equal to the determination value G1 before the return steering angle θ at the time of turning right settles at a constant turning angle and the yaw rate change rate ΔY / ΔT becomes less than the determination value yo.
Alternatively, it becomes G2 or more, and the operation of the link mechanism 29 remains restricted.

Therefore, when the center-of-gravity position Sg is on the rear side of the vehicle from the point A, and the lateral stability of the vehicle is relatively lower than when the center-of-gravity position Sg is on the front side of the vehicle with respect to the point A, the lateral acceleration G at the time of turning is determined. Is greater than or equal to each of the determination values G1 to G4 set according to each loading condition, the operation of the link mechanism 29 is restricted, and the tilting of the vehicle body 11 is prevented. The operation of the link mechanism 29 is permitted until the lateral acceleration G reaches the lateral acceleration determination values G1 to G4.
Is supported in a state of absorbing vibration, the ground pressure does not become excessive, the followability when traveling on uneven terrain is improved and the driving force can be transmitted efficiently, and the driving wheel 13 is pressed against the road surface when turning left. As a result, the ground pressure is secured, and the driving force can be transmitted efficiently.

On the other hand, when the center of gravity Sg is located on the front side of the vehicle with respect to the point A and the lateral stability of the vehicle is relatively high, the lateral acceleration G at the time of turning is determined by each of the determination values G1 to G1 set according to each loading condition. Even if G4 or more, the operation of the link mechanism 29 is not restricted, the left and right stability is maintained, and the driving wheel 13 is supported in a state of absorbing vibration when turning right, so that the ground pressure does not become excessive and The driving force can be transmitted efficiently by improving the followability during traveling on the road surface, and the driving wheel 13 is pressed against the road surface when turning left, the ground pressure is secured, and the driving force can be transmitted efficiently.

As described in detail above, according to the present embodiment, the following effects can be obtained. (1) Detecting the reach position Sr of the mast device 15 and the center of gravity Sg of the vehicle in the longitudinal direction of the vehicle center of gravity determined by the load W of the cargo, and setting the center of gravity Sg between the front wheel axle and the rear wheel axle. When the left-right stability is higher on the front wheel axle side than the reference position (point A), the determination value (lateral acceleration determination values G1 to G4) when the center of gravity position Sg is at the reference position and the left-right stability is lower. The determination value set in the turning state quantity (lateral acceleration G) corresponding to a larger value of the centrifugal force at the time of turning (no regulation based on the lateral acceleration determination value is performed, that is, the lateral acceleration determination value is infinite) Based on this, the operation of the link mechanism 29 is restricted.

Therefore, when the position of the center of gravity Sg is on the front side of the vehicle in which the left-right stability is relatively increased, the traveling performance by the operation of the link mechanism 29 in a wider range than in the prior art while securing a sufficient left-right stability. (The transmission of the driving force at the time of left and right turns with high efficiency, the maintenance of the ride comfort at the time of right turn) is improved, and the center of gravity position Sg is on the rear side of the vehicle, which makes the left-right stability relatively lower. In addition, the left-right stability due to the regulation of the operation of the link mechanism 29 is improved over a wider range than before while the traveling performance is secured. As a result, the traveling performance can be improved in a range where the left-right stability can be ensured during turning.

(2) The closer the center of gravity position Sg is to the front wheel axle side, the smaller the value of the load W of the load and the higher the height position H of the load (G1 for G2, “0” for G2).
(G3 for G4, "0"), a larger value ("0", G1, G2) for the lateral acceleration determination value
The operation of the link mechanism 29 is restricted based on the lateral acceleration determination value set to (infinite with respect to “0”, G3, G4).

That is, the load W of the load is substantially proportional to the magnitude of the centrifugal force for tilting the vehicle body 11 when turning.
And, based on the lateral acceleration G corresponding to the lifting position H, the tilting of the vehicle body 11 during turning is restricted. Therefore, when high left-right stability can be ensured without restricting the operation of the link mechanism 29, the operation of the link mechanism 29 can be reliably permitted, and the traveling performance when the center of gravity is at the front side of the vehicle is improved. , And the left-right stability at the rear side can be reliably ensured.

(3) Drive Steering Wheel 13 and Caster Wheel 1
In the vehicle in which the rear wheels are constituted by the step No. 4, the determination value (G) of the turning state amount (lateral acceleration G according to the lift position H and the load W) when restricting the operation of the link mechanism 29 during the left turn.
3, G4) is set to be larger than the judgment values (G1, G2) at the time of turning to the right, and at the time of turning to the left, the operation of the link mechanism 29 is restricted after the caster spring 39 is almost fully contracted. Therefore, it is possible to suppress a decrease in the ground pressure of the drive wheels 13 due to the tilting of the vehicle body 11 during the left turn, to efficiently transmit the drive force, secure the braking force, and avoid a decrease in the steering performance.

(4) Since the operation of the link mechanism 29 is regulated based on the yaw rate change rate ΔY / ΔT in addition to the lateral acceleration G, the lateral acceleration G at the initial transition from the straight running state to the right turning is determined. Further tilting can be restricted in a state in which the vehicle body 11 is not tilted so much that it has not risen. Therefore, the tilt of the vehicle body 11 can be suppressed as small as possible. When turning left, the yaw rate change rate ΔY / Δ
Since the restriction of the operation of the link mechanism 29 based on T is not performed, the operation of the link mechanism 29 is allowed until the caster spring 39 is fully contracted, so that the traveling performance can be improved.

(5) Since the lateral acceleration G and the yaw rate change rate ΔY / ΔT are calculated using the detected values of the steering angle θ and the vehicle speed V, a comparison is made between an acceleration sensor or the like that directly detects the lateral acceleration G. There is no need to provide an expensive detector. In particular, if the magnetic sensor 64 originally attached to the forklift 10 can be used, and if the steering angle sensor 62 provided for other control or the like is used, the sensor cost can be relatively reduced by sharing the sensors. Can be suppressed.

(6) Since the lateral acceleration G is calculated from the detected values of the steering angle θ and the vehicle speed V, the lateral acceleration G generated when the vehicle body 11 swings right and left due to the uneven road surface during straight running is calculated. The operation of the link mechanism 29 is not restricted based on this. Therefore, the operation of the link mechanism 29 is not unnecessarily restricted during straight running on an uneven road surface,
The drive wheel 13 is actuated by the operation of the suspension spring 41.
The driving force can be efficiently transmitted, and the riding comfort can be ensured.

(7) Considering that the driving wheel 13 is offset in the vehicle width direction and the turning radius r differs depending on the turning direction even when the steering angle θ is the same, the turning radius is separately calculated from the steering angle θ when turning right and left. Since the map M1 for obtaining r is used, the lateral acceleration G and the yaw rate change rate ΔY / ΔT can be obtained accurately, and a highly accurate swing control can be realized.

(8) When the lateral acceleration G is directly detected by the acceleration sensor, the detected value includes noise such as vibration of the vehicle body 11. Therefore, if it is attempted to obtain the yaw rate change rate ΔY / ΔT using a value obtained by performing a difference (differential) process on the detected value, noise may be amplified by the difference process, and the reliability of the estimated value may be poor. On the other hand, according to the present embodiment, the value 1 / r obtained from the steering angle data θ that is hardly affected by the vibration of the vehicle body 11 detected by the steering angle sensor 62 is subtracted (differentiated). The change rate ΔY / ΔT can be detected with high accuracy.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment is different from the first embodiment in that a steering angle sensor 62, a magnetic sensor 64, a rotational displacement sensor 66, and a torque sensor 68 are not provided and a limit switch 81 is provided. A control unit 82 in place of the microcomputer 69;
Of the swing control performed by the microcomputer 70
The only difference is that the control is different from the control performed by the user. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only different points will be described in detail.
Also, the configuration of the microcomputer 85 is the same as the configuration of the microcomputer 70, so that the same reference numerals are used and the description is omitted.

As shown in FIG. 20, the mast device 15 is provided with a fork 19, that is, a limit switch 81 as a height detecting means for detecting the height H of the load. Further, inside the vehicle body 11, each sensor 65, 67,
A control unit 82 for controlling the electromagnetic solenoid 58a of the electromagnetic switching valve 58 based on the detection signal from 81 is provided.

As shown in FIG. 21, the limit switch 8
1 is electrically connected to the input side of the control unit 82. The limit switch 81 is turned off at a lift position H lower than the lift determination value H0 set at a higher position in the entire lift range of the fork 19, and is turned on at a lift position equal to or higher than the lift determination value H0. SS is output to the control unit 82. The lift determination value H0 is the same as the lift determination value H0 of the first embodiment. The control unit 82
Are connected to a pressure sensor 65 as load detecting means and a displacement sensor 67 as reach position detecting means.

The control unit 82 includes an A / D converter 83,
The apparatus includes a solenoid drive circuit 84 and a microcomputer 85 as a load determining means. The CPU 75 of the microcomputer 85 includes an on / off signal SS output from the limit switch 81, a load signal SW output from the pressure sensor 65 via the A / D converter 83, and a reach position signal PS output from the displacement sensor 67. Through the input interface 78. The CPU 75 causes the solenoid drive circuit 84 to output an exciting current Ie for exciting the electromagnetic solenoid 58a via the output interface 79.

In this embodiment, the pressure sensor 65, the limit switch 81 and the microcomputer 85 constitute a stable state quantity detecting means, and the displacement sensor 67 and the microcomputer 85 constitute a loading state detecting means. .

The ROM 76 stores various data including the program data of the swing control processing shown in the flowchart of FIG. The CPU 75 repeatedly executes the swing control process at predetermined time intervals (for example, several tens of milliseconds).

As the swing control processing, the CPU 75 obtains the center of gravity position Sg from the reach position Sr of the mast device 15 and the load W of the load using the maps M6 and M7. ROM
A map M8 for obtaining the load determination value W0 corresponding to the center of gravity position Sg is stored in 76. As shown in FIG. 22, the map M8 sets a larger load determination value W0 as the position of the center of gravity Sg is closer to the front wheel axle side. The CPU 75 performs a swing control process as follows:
Based on a predetermined determination value for a stable state amount corresponding to the magnitude of the moment load that attempts to tilt the vehicle body 11 during a cargo handling operation based on the vertical position of the vehicle center of gravity,
When the magnitude of the moment load is equal to or greater than the magnitude corresponding to the determination value, the operation of the link mechanism 29 is restricted. In the present embodiment, the stable state quantity includes the load W and the lift position H.
Is the position of the center of gravity in the vertical direction of the center of gravity of the vehicle based on
Then, the CPU 75 executes the map M
8, when the calculated center-of-gravity position Sg is closer to the front wheel axle than one reference position between the front wheel axle and the rear wheel axle, the moment load is larger than when the center of gravity position Sg is at the same reference position. Is controlled based on the load determination value W0 set to the load W corresponding to the larger value of. That is, in the present embodiment, the load determination value W0 that increases linearly with respect to the center of gravity position Sg is set by the map M8.

The ROM 76 stores a lift determination value H0 set for the lift position H. CPU7
5 is a swing control process in which the detected lift position H and the load W of the load are determined based on the set load determination value W0 and the constant lift determination value H0. Determine the magnitude of left-right stability of the vehicle. And CPU7
5 determines that the left / right stability is reduced to a predetermined level, restricts the operation of the link mechanism 29 to restrict the tilt of the vehicle body 11, and determines that the left / right stability is not reduced. Then, the operation of the link mechanism 29 is allowed.

The ROM 76 stores a reach determination value S0 for determining that the vehicle has entered the loading state based on the reach position Sr of the mast device 15. When the detected reach position Sr is smaller than the reach determination value S0 as the swing control process, the CPU 75 determines that the vehicle has entered the loading operation. In the present embodiment, it is assumed that the reach position Sr of the mast device 15 is not set to be less than the reach determination value S0 when the vehicle does not perform the loading operation.

The microcomputer 85 has a tilt restriction flag FL. When the load W is equal to or greater than the load determination value W0 and the lift position H is equal to or greater than the lift determination value H0 as the swing control process, the tilt restriction flag FL is set if the reach position Sr is equal to or greater than the reach determination value S0. Is set to "1", otherwise the tilt control flag FL is set to "0". In other words, the CPU 75 starts the loading operation even when the left-right stability of the vehicle, which is determined based on the loading state of the load, restricts the operation of the link mechanism 29 and restricts the tilt of the vehicle body 11. When the operation is performed, the operation of the link mechanism 29 is prohibited from being restricted.

Next, the operation of the above-structured reach forklift will be described with reference to the flowchart of the swing control process shown in FIG. In the swing control processing, C
The PU 75 first detects the lifting position H detected in S400,
The detected values of the load W and the reach position Sr are read. CP
U75 obtains the center-of-gravity position Sg from the reach position Sr and the load W using the maps M6 and M7 in S410.
At 0, the load determination value W0 is set from the center of gravity position Sg using the map M8.

Next, in S430, the CPU 75 determines whether or not the detected lift position H is equal to or greater than the lift determination value H0 and whether the load W is equal to or greater than the load determination value W0. CPU7
5 is S44 when the lift position H is equal to or greater than the lift determination value H0 and the load W is equal to or greater than the load determination value W0 in S430.
At 0, it is determined whether the reach position Sr is equal to or greater than the reach determination value S0. If the reach position Sr is equal to or greater than the reach determination value S0 in S440, the CPU 75 proceeds to S450.
Then, the tilt control flag FL is set to "1" and the process is terminated.

On the other hand, when the lift position H is less than the lift determination value H0 or the load is less than the load determination value W0 in S430, the CPU 75 sets the tilt restriction flag FL to "0" in S460. The process ends.

The solenoid drive circuit 84 outputs the exciting current Ie when the swing regulation flag FL is "0", and stops the output of the exciting current Ie when the swing regulation flag FL is "1". .

Therefore, when the vehicle is not in the state of carrying out the loading operation, the operation of the link mechanism 29 is restricted and the vehicle body is prevented from tilting when the loaded state of the vehicle lowers the lateral stability of the vehicle due to the tilting of the vehicle body 11. You. At this time, as the center-of-gravity position Sg is closer to the front wheel axle side and the left-right stability of the vehicle increases, the operation of the link mechanism 29 is allowed until the load W reaches the load determination value W0, and the driving wheels 13 , The driving force is transmitted with high efficiency, and the driving wheel 13 is supported in a state of absorbing vibration when turning right, so that the riding comfort is improved.

Further, when the vehicle performs the loading operation, the operation regulation of the link mechanism 29 based on the load W and the lifting position H of the load is prohibited, and the left-right stability of the vehicle is ensured regardless of the loaded state of the load. In this state, the operation of the link mechanism 29 is allowed.

As described in detail above, according to the reach forklift of this embodiment, the following effects can be obtained. (9) The value of the load determination value W0 is changed according to the position of the center of gravity Sg, and the position of the center of gravity Sg is on the front wheel axle side and the link mechanism 2
When the left-right stability is relatively large without restricting the operation of the load 9, the load determination value W0 is relatively increased so that the operation of the link mechanism 29 is not easily restricted by the low load W, and the center of gravity position Sg is shifted rearward. Link mechanism 2 on the wheel axle side
If the left-right stability does not become sufficiently large unless the operation of the link 9 is restricted, the load determination value W0 is made relatively small so that the operation of the link mechanism 29 is easily regulated at a low load W. Therefore, when the center of gravity position Sg is on the front wheel axle side, the up-and-down movement of the drive wheel 13 is allowed in a wider range than before while the sufficient left-right stability is ensured, and the road following ability on the uneven road surface is improved. It secures and the running performance is improved. or,
When the position of the center of gravity Sg is on the rear wheel axle side, the left-right stability is improved over a wider range than before while the traveling performance is maintained. As a result, the traveling performance can be improved in a range where the left-right stability can be ensured during the cargo handling operation. (10) The load lifting position H and the load that determine the magnitude of the moment load based on the vertical position of the vehicle center of gravity W
Thus, the tilt of the vehicle body 11 during the cargo handling operation is restricted. Therefore, when high left-right stability can be ensured without restricting the operation of the link mechanism 29, the operation of the link mechanism 29 can be reliably permitted, and
Drivability when the center of gravity is on the front side of the vehicle can be further improved, and left-right stability when the center of gravity is on the rear side of the vehicle can be further improved.

(11) When the vehicle enters the state of carrying out the loading operation, the stable state amount (lift position H and load W)
The restriction on the operation of the link mechanism 29 based on the above is prohibited. Therefore, at the time of loading operation, the link mechanism 29 is allowed to operate in a state where a sufficient magnitude of left-right stability is ensured by the center of gravity position Sg being on the front wheel axle side. As a result, in a state where the line connecting the ground point of the drive wheel 13 and the caster wheel 14 is inclined with respect to the axles of both the driven wheels 12 in a place where the road surface is not flat, the link mechanism 29 is set based on the lift position H and the load W. When the operation is restricted, when the vehicle is moved to a flat place and the loading operation is performed in that state, the restriction condition is eliminated by the loading and the operation restriction of the link mechanism 29 is released, and the vehicle body 11 is generated. Can be prevented from swinging.

The embodiment is not limited to the above embodiment, but may be modified as follows. ○ In the first embodiment, each lateral acceleration determination value G1, G2,
The lateral acceleration determination values G1e, G2e, G3e, and G4e, which have large values for G3 and G4, respectively, are set in advance. When the center of gravity position Sg is located on the front side of the vehicle with respect to the point A, the lateral acceleration determination values G1e and G1e are set. The operation of the link mechanism 29 may be restricted based on G2e, G3e, and G4e. In this case, it is possible to ensure the traveling performance even during the cargo handling operation in which the center of gravity position Sg is on the front side of the vehicle.

In the first embodiment, a map in which the lateral acceleration determination value is set as a linear function with respect to the center of gravity position Sg is prepared, and this map is used to detect the center of gravity position Sg detected at that time. The value of the lateral acceleration determination value to be used may be set in accordance with. In this case, the center of gravity position Sg
Since the optimum lateral acceleration determination value can be set according to the above, the operation of the link mechanism 29 is reliably permitted when high left-right stability can be ensured without restricting the operation of the link mechanism 29. In addition, it is possible to further improve the traveling performance when the position of the center of gravity is on the front side of the vehicle and to improve the left-right stability when the position of the center of gravity is on the rear side of the vehicle.

The load W of the cargo in the first embodiment
Alternatively, the operation of the link mechanism 29 may be restricted based on only the lifting position H to prevent the vehicle body 11 from tilting.
For example, when the position of the center of gravity Sg is on the rear side of the vehicle from the point A, the operation of the link mechanism 29 is restricted when the load W is equal to or more than the load determination value W0 and the height position H is equal to or more than the lift determination value H0. When the position Sg is on the front side of the vehicle with respect to the point A, the restriction based on the load W and the lifting position H is not performed. In this case, the tilt of the vehicle body 11 at the time of turning is determined without using the lateral acceleration G, the vehicle speed V, and the like.
, The traveling performance when the center of gravity position Sg is on the front side of the vehicle and the left-right stability when it is on the rear wheel of the vehicle can be improved.

○ In the first embodiment, the vehicle body 1
The operation of the link mechanism 29 may be restricted based on only the magnitude of the lateral acceleration G applied to 1 to prevent the body 11 from tilting. For example, when the position of the center of gravity Sg is on the rear side of the vehicle from the point A, the operation of the link mechanism 29 is restricted when the lateral acceleration G is equal to or greater than the lateral acceleration determination value G0, and the position of the center of gravity Sg is on the vehicle front side of the point A. Sometimes, the regulation based on the lateral acceleration G is not performed. In this case, since the tilt of the vehicle body 11 at the time of turning is determined based on the lateral acceleration G proportional to the centrifugal force applied to the vehicle at the time of turning, the tilt is determined based on the load W of the load and the lifting position H. As compared with the case, the traveling performance when the center of gravity is on the front side of the vehicle can be further improved, and the left-right stability when the center of gravity is on the rear side of the vehicle can be further improved.

In the first embodiment, if the reach forklift 10 handles only the same load with the load W, the operation of the link mechanism 29 is regulated based only on the lifting position H of the load, and the body 11 during turning is controlled. May be prevented. For example, when the center-of-gravity position Sg is on the rear side of the vehicle from the point A, the operation of the link mechanism 29 is restricted when the lift position H is equal to or higher than the lift determination value H0, and the center-of-gravity position Sg is on the vehicle front side of the point A. In some cases, the restriction based on the lifting position H is not performed. In this case, when handling only a load having the same load W, the tilting of the vehicle body 11 at the time of turning is preferably restricted based only on the elevation position H, and traveling when the center of gravity is located on the front side of the vehicle. And the left-right stability when the position of the center of gravity is on the rear side of the vehicle can be further improved.

In the second embodiment, if the reach forklift 10 handles only the same load W, the operation of the link mechanism 29 may be restricted based only on the lifting position H. For example, as the center of gravity position Sg is closer to the front of the vehicle, a larger value of the lift determination value H0 is set, and the link mechanism 29 is set based on the set lift determination value H0.
Regulate the operation of In this case, when only the same load W is handled, the tilting of the vehicle body 11 at the time of the cargo handling operation is preferably restricted based on only the lifting position H to improve the traveling performance when the center of gravity is at the front side of the vehicle. Further, the left-right stability when the position of the center of gravity is on the rear side of the vehicle can be further improved.

In the second embodiment, even when the vehicle enters the loading operation, the control for restricting the operation of the link mechanism 29 is performed based on the determination values of the lifting position H and the load W. Is also good. In this configuration, the reach forklift 10
Is used only in the premises of a flat road surface, and the operation of the link mechanism 29 is not restricted in a state where the line connecting the ground point of the drive wheel 13 and the ground point of the caster wheel 14 is inclined with respect to the front wheel axle. In this case, the left-right stability during the loading operation can be further increased.

The reach position Sr in the second embodiment
It may be determined that the vehicle has entered the loading operation based on the vehicle speed V. In this case, when the mast device 15 is reached while the vehicle speed V is high, the control unit 82 does not judge that the vehicle has started loading.

In the second embodiment, instead of the load determination value W0 set to increase linearly as the position of the center of gravity Sg is closer to the vehicle front side, the position of the center of gravity Sg is changed to the first embodiment. When the vehicle is behind the point A in
May be set, and when the position of the center of gravity Sg is on the front side of the vehicle with respect to the point A, the second load determination value W2 which is larger than the first load determination value W1 may be set. . Also in this case, it is possible to improve the traveling performance when the center of gravity position Sg is on the front side of the vehicle, and it is possible to improve the left-right stability while securing the traveling performance when it is on the rear side of the vehicle.

In the first embodiment, when the control for restricting the operation of the link mechanism 29 is performed based on the lateral acceleration determination values G1 to G4 set for the lateral acceleration G, the respective lateral acceleration determination values For each of G1 to G4, a regulation release determination value G1f to G4f smaller than each of the determination values G1 to G4 (for example, 0.5 <G <1) is set. And the link mechanism 2
For example, when the operation of the link mechanism 29 is restricted based on the lateral acceleration determination value G1 at the time of the operation restriction of 9, the operation restriction is released based on the restriction release determination value G1f. In this case, when the detected value of the lateral acceleration G changes in the vicinity of the lateral acceleration determination value G1, the link mechanism 2
9 to prevent the operating state from being frequently regulated and released,
The regulation of the tilting of the vehicle body 11 is stably performed, so that the running state can be stabilized.

Similarly, a regulation release determination value is provided for the yaw rate change rate determination value y0 set for the yaw rate change rate ΔY / ΔT. Then, the operation of the link mechanism 29 is restricted based on the yaw rate change rate determination value y0, and the operation is released based on the restriction release determination value. Also in this case, the regulation of the tilting of the vehicle body 11 based on the yaw rate change rate ΔY / ΔT is stably performed, so that the running state can be stabilized.

In the first embodiment, in addition to the lateral acceleration G, the operation of the link mechanism 29 is regulated based on the lateral acceleration change rate ΔG / ΔT instead of the yaw rate change rate ΔY / ΔT. Good. Also in this case, the operation of the link mechanism 29 can be restricted in a state where the lateral acceleration G at the time of starting the transition from the straight traveling state to the turning state is not increased, and the tilting of the vehicle body 11 can be suppressed as small as possible. .

In the first embodiment, the lateral acceleration may be directly detected by the lateral acceleration sensor. or,
The yaw rate change rate ΔY / ΔT may be obtained from the yaw rate directly detected by the yaw rate sensor.

In the first embodiment, instead of the steering angle sensor 62 for detecting the steering angle θ as an absolute value, a magnetic sensor for detecting presence / absence of each tooth facing the rotation of the gear wheel 45 is provided. A torque sensor for detecting a steering torque applied to the steering wheel 23. The CPU 75 detects the turning direction from the direction of the steering torque, and determines the steering angle θ from the relative steering amount of the steered wheels 13 from the straight traveling state. You may do so. The torque sensor used in the power steering device can be used in common. Also with this configuration, the turning direction and the steering angle θ can be detected.

In each embodiment, an electromagnetic proportional control valve capable of continuously adjusting the opening degree is used instead of the electromagnetic switching valve 58 that opens and closes. Control unit 69 (82)
Is to control the opening of the electromagnetic proportional control valve by duty control. If the electromagnetic proportional control valve is a normally-closed type, the CPU 75 gradually increases the magnitude of the exciting current Ie supplied to the electromagnetic proportional solenoid when the operation of the link mechanism 29 is permitted, thereby reducing the opening degree. When the operation is regulated, the supply of the exciting current Ie is stopped immediately to control the opening to be fully closed immediately. In this case, for example, when the operation of the link mechanism 29 is permitted during turning,
Can be prevented from becoming unstable.

In each of the embodiments, the reach forklift is supported by the vehicle body 11 so that the drive wheel 13 and the caster wheel 14 are allowed to tilt by a separate rear wheel support mechanism that is independent, ie, an independent A reach forklift having a suspension structure may be used. In this case, the tilting of the vehicle body 11 can be prevented by simultaneously restricting the operation of the dampers provided in the respective rear wheel support mechanisms.

In each embodiment, instead of restricting the operation of the link mechanism 29 by the damper 53 having the throttle valve 61, the operation may be restricted by a restricting hydraulic cylinder having no throttle valve. In this case, by providing a damper cylinder for tilting buffer separately from the restricting hydraulic cylinder, it is possible to prevent the vehicle body 11 from suddenly tilting and suddenly returning from the tilting state.

In each of the embodiments, the operation restricting means for restricting the operation of the rear wheel support mechanism is not limited to the damper 53 whose expansion / contraction operation is permitted or restricted by the electromagnetic switching valve. In addition, for example, a configuration in which a brake disc is fixed to a member such as an upper link 30 that swings with respect to the vehicle body 11 by the operation of the link mechanism 29, and the operation of the link mechanism 29 is regulated by sandwiching the brake disc with a piston brake. It may be.

In each embodiment, the reach forklift may have a structure in which the caster wheel 14 is directly fixed to the link mechanism 29 without the caster spring 39 therebetween.

In each of the embodiments, the rear wheel support mechanism has a structure in which the caster wheel 14 is not in contact with the ground when the vehicle body 11 is horizontal and is in contact with the ground only when the vehicle body 11 tilts slightly to the right. Good.

Each of the embodiments may be applied to a reach forklift in which the rear wheels include two drive steered wheels. Hereinafter, technical ideas other than the claims that can be grasped from the embodiment will be described together with their effects.

(1) In the reach forklift according to any one of claims 1 to 4, the rear wheels are drive steering wheels and caster wheels, and the rear wheel support mechanism is the same as that of the vehicle. A parallel link mechanism including a pair of upper and lower upper links and a lower link, which are disposed substantially horizontally in the roll surface and whose ends on the same side are rotatably supported by the vehicle body, and a connector that connects both levers, Biasing means for biasing the connector downward of the vehicle body, wherein the connector supports the drive steering wheel, and the lower link is substantially horizontal from a base shaft side to a side opposite to the connector. An extended caster link was provided, and the caster wheel was supported on the tip side of the caster link.
According to such a configuration, at the time of a turn in which the drive steered wheels become the outer wheels, it is possible to improve the road surface following ability of the drive steered wheels when traveling on uneven road surfaces, efficiently transmit the driving force, and improve the traveling performance, At the time of turning in which the drive steered wheels become inner wheels, the drive steered wheels are pressed against the road surface, the ground pressure is secured, and the driving force is transmitted efficiently.

(2) In the above (1), the tilt control means, when turning the drive steering wheel becomes an inner wheel, more than the determination value set at the time when the drive steering wheel becomes an outer wheel. The operation restricting means is controlled based on the determination value set for the value of the turning state amount corresponding to a larger value. According to such a configuration, at the time of turning in which the drive steered wheels become inner wheels, the drive steered wheels are reliably pressed against the road surface by the operation of the link mechanism,
The driving force can be reliably and efficiently transmitted.

(3) In the invention according to claim 2 or 4, the lateral acceleration detecting means includes a steering detecting means for detecting a steering angle of the rear wheel, a vehicle speed detecting means for detecting a vehicle speed, and a steering wheel. Lateral acceleration calculating means for calculating the lateral acceleration from the angle and the vehicle speed. According to such a configuration, the operation of the rear wheel support mechanism is not restricted by the lateral acceleration generated by the swing of the vehicle body when the vehicle is traveling straight on an uneven road surface, so that the road surface followability of the rear wheels, which are the drive wheels, is secured and the drive is performed. Power can be transmitted efficiently.

(4) The reach forklift according to any one of claims 1 to 4, further comprising a yaw rate change rate detecting means for detecting a yaw rate change rate, wherein the tilt control means determines the yaw rate change rate in advance. When it is equal to or greater than the set determination value, the operation restricting means is controlled. According to such a configuration, further tilting can be restricted while the tilting of the vehicle body is small, and it is not necessary to set the determination value of the lateral acceleration to a small value, so that the traveling performance can be further improved. .

(5) The reach forklift according to any one of claims 1 to 4, further comprising a lateral acceleration change rate detecting means for detecting a lateral acceleration change rate, wherein the tilt control means comprises: When the rate is equal to or greater than a predetermined judgment value, the operation restricting means is controlled. According to such a configuration, further tilting can be restricted while the tilting of the vehicle body is small, and it is not necessary to set the determination value of the lateral acceleration to a small value, so that the traveling performance can be further improved. .

(6) In the reach forklift according to any one of claims 1 to 4, the tilt control means restricts the operation of the rear wheel support mechanism when the operation is released from the state where the operation is restricted. The operation restricting means is controlled based on a determination value set for the value of the turning state amount corresponding to a smaller value of the centrifugal force than the determination value when the operation is performed. According to such a configuration, the control for restricting the tilt of the vehicle body can be stably performed, and the running state at the time of turning can be stabilized.

(7) In the reach forklift according to any one of claims 1 to 4, the operation restricting means controls the operation of the rear wheel support mechanism between the rear wheel support mechanism and the vehicle body. A double-acting hydraulic cylinder provided so as to be allowed or regulated, and a flow passage communicating a pair of oil chambers of the double-acting hydraulic cylinder are provided to allow or block movement of hydraulic oil between the two oil chambers. An electromagnetically operated valve, wherein the tilt control means controls the electromagnetically operated valve. According to such a configuration, it is possible to provide an operation restricting unit that does not require external power supply.

(8) In the above (7), the solenoid operated valve is a proportional opening / closing control valve whose opening is continuously changed, and the tilt control means regulates the operation of the rear wheel support mechanism. Sometimes, the proportional control valve is controlled so that the opening of the proportional on-off control valve is fully closed promptly from full open, and when the operation of the rear wheel support mechanism is allowed, the opening is gradually fully opened from fully closed. The proportional control valve is controlled so that
According to such a configuration, when the operation of the rear wheel support mechanism is permitted during turning, a shock accompanying the permission is not generated in the vehicle body.

(9) In the reach forklift according to claim 1, the turning state quantity is a vertical center of gravity of the vehicle based on a lifting position of the load, and the turning state quantity detecting means is a forklift. Lifting position detecting means for detecting a lifting position, wherein the tilt control means controls the operation restricting means based on a larger judgment value set for the lifting position. According to such a configuration, when only a load having the same load is handled, the tilting of the vehicle body during turning is preferably restricted based on only the lift position, and traveling when the center of gravity position is on the front side of the vehicle. And the left-right stability when the position of the center of gravity is on the rear side of the vehicle can be improved.

(10) In the reach forklift according to claim 5, the stable state quantity is a position of the center of gravity of the vehicle in the vertical direction of the vehicle based on the lift position of the fork, and the stable state quantity detecting means is The tilt control means controls the operation restricting means based on a larger determination value set for the lift position. According to such a configuration, when handling only a load having the same load, the tilting of the vehicle body during the cargo handling operation is preferably restricted based on only the lifting position to improve the traveling performance when the center of gravity position is on the front side of the vehicle. It is possible to improve the left-right stability when the position of the center of gravity is on the rear side of the vehicle.

[0158]

According to the first to eighth aspects of the present invention, the tilting of the vehicle body is suitably regulated in accordance with the position of the center of gravity of the vehicle in the longitudinal direction of the vehicle, and the vehicle travels in a range in which left-right stability can be ensured. Improve the performance.

According to the first to fourth aspects of the present invention, the tilting of the vehicle body at the time of turning is suitably regulated according to the position of the center of gravity of the vehicle center of gravity in the front-rear direction of the vehicle, so that left-right stability during turning can be ensured. Drivability can be improved within the range.

According to the fourth aspect of the invention, it is possible to further improve the traveling performance when the position of the center of gravity is on the front side of the vehicle and to further improve the left-right stability when the position of the center of gravity is on the rear side of the vehicle. .

According to the fifth to eighth aspects of the present invention, the tilting of the vehicle body during the cargo handling operation is suitably restricted according to the position of the center of gravity of the vehicle center of gravity in the front-rear direction of the vehicle. Drivability can be improved within the range that can be ensured.

According to the seventh aspect of the invention, it is possible to prevent the vehicle body from shaking due to the fact that the operation of the rear wheel support mechanism is allowed immediately after loading. According to the invention described in claim 8, the loading state can be automatically detected with a simple configuration without providing new detecting means.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a swing control device according to a first embodiment.

FIG. 2 is a schematic side view of a reach forklift.

FIG. 3 is a schematic plan view similarly.

FIG. 4 is a schematic rear view of a rear wheel support mechanism.

FIG. 5 is a schematic plan view of the same.

FIG. 6 is a schematic rear view showing a configuration of a drive system and a steering system.

FIG. 7 is an electric block diagram of a swing control device.

FIG. 8 is a map showing a relationship between a steering angle and a turning radius.

9A and 9B are maps for setting a lateral acceleration determination value with respect to a lift position and a load.

FIGS. 10A and 10B are maps for setting a lateral acceleration determination value with respect to a lift position and a load.

FIG. 11 is a map for obtaining a position of a center of gravity from a load.

FIG. 12 is a map for obtaining a position of a center of gravity from a load.

FIG. 13 is a schematic plan view for explaining the position of the center of gravity.

FIG. 14 is a flowchart of a swing control process.

FIG. 15 is a flowchart of a swing control process.

FIG. 16 is a graph showing changes in the lateral acceleration and the yaw rate change rate during turning.

FIG. 17 is a graph showing changes in the lateral acceleration and the yaw rate change rate during turning.

FIG. 18 is a schematic rear view showing the link mechanism in an operation restriction state during a right turn.

FIG. 19 is a schematic rear view showing the link mechanism in an operation restricted state at the time of turning left.

FIG. 20 is a schematic configuration diagram of a swing control device according to a second embodiment.

FIG. 21 is an electric block diagram of a swing control device.

FIG. 22 is a map for setting a load determination value from the position of the center of gravity.

FIG. 23 is a flowchart of a swing control process.

FIG. 24 is a schematic rear view of a conventional rear wheel support mechanism.

[Explanation of symbols]

11: body, 12: driven wheel as front wheel, 13: drive steering wheel as rear wheel, 14: caster wheel, 15 ...
Mast, 26: rear wheel support mechanism, 53: damper constituting operation restricting means, 58: similarly electromagnetic switching valve, 62: steering angle sensor as steering angle detecting means constituting lateral acceleration detecting means and turning state amount detecting means , 64: a magnetic sensor as vehicle speed detecting means; 65, a pressure sensor as load detecting means constituting a turning state amount detecting means, a center of gravity position detecting means and a stable state amount detecting means; 66, a turning state amount detecting means; Rotational displacement sensor as a lifting height detecting means, 6
7: Displacement sensor as reach position detecting means constituting the center of gravity position detecting means and the loading state detecting means, 71: constituting the lateral acceleration detecting means, turning state amount detecting means, center of gravity position detecting means and stable state amount detecting means Microcomputer as tilt control means; 74, a solenoid drive circuit constituting operation restricting means; 81, a limit switch constituting stable state quantity detecting means; 85, stable state quantity detecting means;
Microcomputer as tilting control means and loading determination means constituting the center of gravity position detection means and loading state detection means, A: point as reference position, G: lateral acceleration as turning state quantity, G1 to G4: determination values A lateral acceleration determination value, H ... a lift position as a stable state amount, H0 ... a lift determination value as a determination value, Sg ... a center of gravity position, Sr ... a reach position, S0 ... a reach determination value constituting a predetermined range, W: load as a stable state quantity; W0: load determination value as a determination value.

Claims (8)

[Claims] 1. A vehicle comprising a mast which moves in the front-rear direction of a vehicle, two front wheels having an axle fixed thereto, and two rear wheels having an axle not fixed thereto, each of the rear wheels being supported by a vehicle body. A rear wheel support mechanism that operates to allow tilting of the vehicle body, and an operation restricting unit that allows or restricts the operation of the rear wheel support mechanism to allow or restrict the tilting of the vehicle body; Turning state amount detecting means for detecting a turning state amount of the vehicle corresponding to the magnitude of the centrifugal force for tilting the vehicle body at the time, and the centrifugal force is determined based on a judgment value preset for the turning state amount. And a tilt control means for controlling the operation restricting means so as to restrict the operation of the rear wheel support mechanism when the force is equal to or greater than the magnitude corresponding to the determination value. A reach position detecting means for detecting, a load detecting means for detecting a load of a load loaded on the fork, and a center of gravity position detecting means for obtaining a center of gravity of the vehicle center of gravity in the longitudinal direction of the vehicle from the reach position and the load, The tilt control means is configured such that, when the center of gravity position is a position closer to the front wheel axle side than a reference position set in advance between the front wheel axle and the rear wheel axle, the center of gravity position is greater than when the center of gravity position is at the reference position. A reach forklift for controlling the operation restricting means based on the determination value set for a value of the turning state amount corresponding to a larger value of the centrifugal force. 2. The turning state quantity is a lateral acceleration applied to the vehicle at the time of turning, the turning state quantity detecting means is a lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle at the time of turning, and the tilt control The reach forklift according to claim 1, wherein the means controls the operation restricting means based on the larger determination value set for the lateral acceleration. 3. The turning state amount is a vertical position of a vehicle based on a load position and a load, and the turning state amount detecting means detects a lift position of a fork. And a load detecting means for detecting a load of the load, wherein the tilt control means controls the operation restricting means based on a larger judgment value set for the lift position and the load. Reach forklift described in. 4. The turning state quantity is a vertical position of the vehicle based on the lift position and the load of the load, and a lateral acceleration applied to the vehicle body. A height detecting means for detecting a position, a load detecting means for detecting a load of a load, and a lateral acceleration detecting means for detecting a lateral acceleration applied to the vehicle body, wherein the tilt control means, with respect to the lateral acceleration, 2. The reach according to claim 1, wherein the operation restricting unit is controlled based on a judgment value set to a larger value with respect to a judgment value set to a smaller value with respect to a larger value of the load and the lifting position. forklift. 5. A vehicle having a mast that moves in the front-rear direction of a vehicle and two front wheels having an axle fixed thereto, and two rear wheels not having an axle fixed thereto, and supporting each of the rear wheels with respect to the vehicle body. A rear wheel support mechanism that operates to allow tilting of the vehicle body, and an operation restricting unit that allows or restricts the operation of the rear wheel support mechanism to allow or restrict the tilting of the vehicle body. A stable state amount detecting means for detecting a stable state amount of the vehicle corresponding to a magnitude of a moment load for tilting the vehicle body during a cargo handling operation based on the vertical position; and a determination preset for the stable state amount Tilt control means for controlling the operation restricting means so as to restrict the operation of the rear wheel axle support mechanism when the magnitude of the moment load is equal to or greater than the magnitude corresponding to the determination value based on the value. A load detecting means for detecting a load of a load loaded on a fork, a reach position detecting means for detecting a reach position of a mast, and a center of gravity of a vehicle center of gravity in a longitudinal direction of the vehicle from the reach position and the load. A center-of-gravity position detecting means for detecting a position, wherein the tilt control means, when the center-of-gravity position is a position closer to the front wheel axle than a reference position set in advance between the front wheel axle and the rear wheel axle, A reach forklift for controlling the operation restricting means based on the determination value set to the stable state amount corresponding to a larger value of the moment load than when the position of the center of gravity is at the reference position. 6. The stable state quantity is a height position of a fork and a position of a center of gravity of a vehicle center of gravity in a vertical direction of the vehicle based on a load of the load, and the stable state quantity detection means determines a lift position of the fork. The tilt control means controls the operation restricting means based on a larger determination value set for the lift position and the load. The reach forklift according to claim 5, wherein 7. A loading state detecting means for detecting that the vehicle is in a state of performing a loading operation, wherein the tilt control means is configured to determine the determination value when the vehicle is in a state of performing a loading operation. The reach forklift according to claim 5 or 6, wherein control for restricting operation of the rear wheel support mechanism based on the control is prohibited. 8. The loading state detecting means, the reach position detecting means, and a loading determining means for determining that the vehicle is in the loading state because the reach position is within a predetermined range including at least the reach state. The reach forklift according to claim 7, comprising: