JP2005247162A - Hydraulic drive type industrial vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic drive type industrial vehicle with a simple and inexpensive constitution capable of obtaining a drive force enough to escape from a slip condition due to projection, indentation, and soft ground of a road. <P>SOLUTION: Plural sets of pairs of right and left wheels are installed on front and rear sides, and at least one set of wheels are constituted as drive wheels 3A, 3B interconnected with hydraulic motors 21A, 21B, respectively. One hydraulic pump 30 is installed on a vehicle body 2 side, and proportional electromagnetic switch valves 37A, 37B reducing a flow rate and switching normal and reverse rotation of the hydraulic motors 21A, 21B by slip-detecting the corresponding drive wheels 3A 3B are interposed in a piping from the hydraulic pump 30 to each of the hydraulic motors 21A, 21B. Based on the slip-like detection, the proportional electromagnetic switch valve corresponding to one slipped drive wheel is operated to reduce, so as to reduce a working oil supply volume to the hydraulic motor and rotate one drive wheel at a low speed. Also, the working oil supply volume to the hydraulic motor corresponding to the other drive wheel increases to increase the pressure, and the other drive wheel can be rotated and traveled with a large drive force, so as to escape from a slip condition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydraulic drive type industrial vehicle such as a forklift.

  As a drive system for this type of vehicle, a hydraulic drive system that is simple in operation and structure and easy in remote operation is often adopted, and the configuration thereof includes one pump-multiple motor, multiple pump-multiple motor, and the like. It depends on the specifications. In general, a vehicle has a plurality of drive wheels, and all of these drive wheels must contact the dry ground (on the road surface). However, depending on the unevenness of the road surface and the degree of soft ground, the drive wheel slips and slips. However, the driving force is not generated on the other driving wheels, and traveling may become impossible.

  In order to solve such problems, the following configuration has been conventionally provided. That is, open / close valves are arranged in the middle of the direct passages for the hydraulic motors of the left and right rear wheels, and throttle oil passages are provided in parallel with the direct passages, with these open / close valves being sandwiched therebetween.

According to this, during normal driving, the pressure oil that exits the hydraulic motor passes through both the direct passage and the throttle oil passage, so the pressure oil passage resistance is smaller and smoother than in the case of only the direct passage. Pressure oil can move. When one of the rear wheels is idle due to unevenness on the road surface, the two open / close valves are excited simultaneously. Then, since the pressure oil flows only through the throttle oil passage, the amount of pressure oil supplied to the hydraulic motor of the rear wheel that has been idling is limited. As a result, the pressure oil pressure on the other hydraulic motors increases, and the road surface It is said that a driving force is generated on the other rear wheel that is not included in the unevenness of the road and can escape from the unevenness of the road surface (see, for example, Patent Document 1).
JP 2002-372149 A (1st, 4th page, FIG. 3)

  However, according to the above-described conventional configuration, it is necessary to provide a throttle oil passage (pipe) corresponding to each hydraulic motor, which makes the configuration complicated and expensive. In addition, since the pressure oil with a limited supply amount is supplied to the hydraulic motors of both rear wheels in an equal amount, the idling state is continued, and is sufficient for escape when a large load is applied. In some cases, a driving force is not generated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic drive type industrial vehicle having a simple and inexpensive configuration and capable of always obtaining a sufficient driving force for escape.

  In order to achieve the above-described object, in the hydraulic drive type industrial vehicle according to claim 1 of the present invention, the vehicle body is provided with a plurality of pairs of left and right wheels on the front and back, and at least one set of wheels is respectively It is composed of a drive wheel linked to a hydraulic motor, and one hydraulic pump is provided on the vehicle body side, and a slip state of the corresponding drive wheel is detected in the piping from this hydraulic pump to each hydraulic motor. And a proportional electromagnetic switching valve for switching between forward and reverse rotations of the hydraulic motor is interposed.

  Therefore, according to the first aspect of the invention, each proportional electromagnetic switching valve is switched and the direction of the flow of hydraulic oil from the hydraulic pump is switched, so that both drive wheels are forwardly rotated through both hydraulic motors. It is possible to switch between traveling and reverse traveling in which both drive wheels are reversely rotated via both hydraulic motors. Such turning control during forward / reverse running can be performed by controlling each proportional electromagnetic switching valve to control the rotation speed and rotation direction of each hydraulic motor.

  That is, by controlling the throttle of the proportional electromagnetic switching valve on the inside of the turn and rotating the hydraulic motor on the inside of the turn at a low speed, the drive wheel on the inside of the turn can be rotated at a low speed by rotating in the same direction in the left and right directions, so Turning can be done by giving a difference in number. Further, by setting the proportional electromagnetic switching valve on the inside of the turn to the communication stop state and stopping the rotation of the hydraulic motor on the inside of the turn, only the driving wheel on the outside of the turn can be rotated to perform the pivot travel. Then, the proportional electromagnetic switching valve on the inside of the turn is switched and the throttle control is performed, and the hydraulic motor on the inside of the turn is rotated in the reverse direction at a low speed, thereby rotating the driving wheel on the inside of the turn at a low speed and rotating in the pivot direction. Yes. Furthermore, by switching and controlling the proportional electromagnetic switching valve on the inside of the turn and reversely rotating the hydraulic motor on the inside of the turn, the left and right hydraulic motors, that is, the left and right drive wheels, rotate in the left and right directions and have the same rotational speed. Therefore, a spin turn with a minimized turning radius can be performed. As a result, it is possible to perform a right turn or a left turn during forward / backward travel.

  In such normal driving, when one of the left and right drive wheels is in a slip state (idle state) and no drive force is generated on the other drive wheel, slip detection is detected. Based on this, the proportional electromagnetic switching valve corresponding to one drive wheel is throttled. As a result, the amount of hydraulic oil supplied to the hydraulic motor corresponding to one slip-like drive wheel is reduced, the slip-like drive wheel is rotated at a low speed, and the hydraulic oil to the hydraulic motor corresponding to the other drive wheel is reduced. The supply will be increased. Therefore, in the hydraulic motor corresponding to the other drive wheel, the pressure of the hydraulic oil rises, so that the other drive wheel can be rotated with a large driving force to be able to travel.

  Further, in the hydraulic drive type industrial vehicle according to claim 2 of the present invention, the vehicle body is provided with a plurality of pairs of left and right wheels on the front and back, and at least one set of wheels is linked to a hydraulic motor and driven. Proportional solenoid valves that are configured on wheels and that are provided with one hydraulic pump on the vehicle body side, and that reduce the flow rate by detecting slipping of the corresponding drive wheels in the piping from the hydraulic pump to each hydraulic motor. Further, a proportional electromagnetic switching valve for switching between forward and reverse rotations of the hydraulic motor is interposed.

  Therefore, according to the second aspect of the present invention, each proportional electromagnetic switching valve is switched and the direction of the flow of hydraulic oil from the hydraulic pump is switched, so that both drive wheels are forwardly rotated through both hydraulic motors. It is possible to switch between traveling and reverse traveling in which both drive wheels are reversely rotated via both hydraulic motors. Each proportional solenoid valve is in a normal communication state during such forward / reverse travel. The turning control during forward / reverse running can be performed by controlling the proportional electromagnetic switching valves to control the rotation speed and rotation direction of each hydraulic motor.

  In such normal driving, when one of the left and right drive wheels is in a slip state (idle state) and no drive force is generated on the other drive wheel, slip detection is detected. Based on this, the proportional solenoid valve corresponding to one drive wheel is throttled. As a result, the amount of hydraulic oil supplied to the hydraulic motor corresponding to one slip-like drive wheel is reduced, the slip-like drive wheel is rotated at a low speed, and the hydraulic oil to the hydraulic motor corresponding to the other drive wheel is reduced. The supply will be increased. Therefore, in the hydraulic motor corresponding to the other drive wheel, the pressure of the hydraulic oil rises, and thus the other drive wheel can be rotated with a large driving force to be able to travel.

  In the hydraulic drive type industrial vehicle according to claim 3 of the present invention, if a difference greater than the rotation difference between the left and right drive wheels controlled by the handle is generated in the configuration according to claim 1 or 2, a slip-like state occurs. It is considered that the flow rate is reduced by operating the proportional solenoid valve or the proportional solenoid valve on the side where the number of revolutions is larger than the predetermined number of revolutions determined by the handle turning angle. Is.

  Therefore, according to the invention of claim 3, when one of the left and right driving wheels is in a slip state (idling state) and no driving force is generated in the other driving wheel, the wheel is controlled by the handle. If a difference equal to or greater than the rotation difference between the left and right drive wheels occurs, it is detected as a slip, and based on this detection, a proportional electromagnetic switching valve on the side with a higher rotation speed than the predetermined rotation speed determined by the steering angle Alternatively, a proportional solenoid valve, that is, a proportional solenoid switching valve or a proportional solenoid valve corresponding to one drive wheel is throttled. As a result, the proportional electromagnetic switching valve or the proportional electromagnetic valve can be automatically controlled by slip detection.

  Furthermore, the hydraulic drive type industrial vehicle according to claim 4 of the present invention is characterized in that, in the configuration according to claim 2 or 3, the proportional solenoid valve is a proportional solenoid throttle valve.

  Therefore, according to the invention of claim 4, the squeezing action can be easily performed.

  According to the first aspect of the present invention described above, during normal traveling, one of the left and right drive wheels is in a slip state (idle state), and no drive force is generated on the other drive wheel. The amount of hydraulic oil supplied to the hydraulic motor corresponding to one slip-shaped drive wheel is reduced by restricting the proportional electromagnetic switching valve corresponding to one drive wheel based on the slip-shaped detection. Thus, the slip drive wheel can be rotated at a low speed, and the amount of hydraulic oil supplied to the hydraulic motor corresponding to the other drive wheel can be increased. Therefore, the hydraulic motor corresponding to the other drive wheel can increase the pressure of the hydraulic oil, so that the other drive wheel can be rotated with a large driving force and can travel to escape from the slip state.

  This makes it possible to replace the valve for switching the forward / reverse rotation of the hydraulic motor interposed in normal piping with a proportional electromagnetic switching valve, while slipping due to road surface unevenness or soft ground. A driving force sufficient to escape from the state can be obtained.

  According to the second aspect of the present invention described above, during normal traveling, one of the left and right drive wheels is in a slip state (idle state), and a drive force is generated in the other drive wheel. When there is no more slip, the proportional solenoid valve corresponding to one drive wheel is throttled based on the slip detection, thereby reducing the amount of hydraulic oil supplied to the hydraulic motor corresponding to one slip drive wheel. Thus, the slip drive wheel can be rotated at a low speed, and the amount of hydraulic oil supplied to the hydraulic motor corresponding to the other drive wheel can be increased. Therefore, it is possible to obtain a driving force sufficient for escape from a slip state due to road surface unevenness or soft ground, while having a simple and inexpensive configuration in which a proportional solenoid valve is interposed in normal piping.

  According to claim 3 of the present invention described above, when one of the left and right drive wheels is in a slip state (idling state) and no driving force is generated on the other drive wheel, If a difference equal to or greater than the rotation difference between the left and right drive wheels to be controlled occurs, it is detected as a slip, and based on this detection, the proportionality on the side with the higher rotation speed than the predetermined rotation speed determined by the steering angle Solenoid switching valve or proportional solenoid valve, i.e., proportional solenoid switching valve or proportional solenoid valve corresponding to one drive wheel can be throttled, so that the proportional solenoid switching valve or proportional solenoid valve is automatically detected by slip detection. By controlling, the flow rate can be accurately and reliably controlled.

  Further, according to the fourth aspect of the present invention, the squeezing action can be performed easily and accurately.

[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS.
1 and 2, a forklift (an example of an industrial vehicle) 1 is provided with a pair of left and right front wheels (drive wheels) 3A and 3B at the front of a vehicle body 2, and a pair of left and right rear wheels 4A and 4B is provided, and a driver's seat 5 is provided above the front portion of the vehicle body 2. A mast 6 that can be expanded and contracted in the vertical direction is attached to the front end portion of the vehicle body 2 via a connecting shaft 7 in the vehicle width direction so as to be rotatable in the front-rear direction, and a tilt cylinder 8 that rotates in the front-rear direction. It is provided between the vehicle body 2 and the mast 6.

  The mast 6 is composed of a pair of left and right outer frames 9 on the forklift 1 side and a pair of left and right inner frames 10 which are guided by the outer frame 9 and can freely move up and down, and the mast 6 is lifted between the outer frame 9 and the inner frame 10. A cylinder 11 is provided. A lift bracket 12 which is guided to the inner frame 10 side and can be moved up and down is provided, and a pair of left and right forks 13 is provided on the lift bracket 12 via a pair of upper and lower finger bars. The driver's seat 5 is provided with a seat 15, a handle 16 positioned in front of the seat 15, and the like, and above the head guard via a front pipe 17 and a rear pipe 18 erected from the vehicle body 2 side. 19 is disposed. A counterweight 20 is provided on the vehicle body 2 behind the seat 15.

  The rims 3a and 3b of the pair of left and right front wheels 3A and 3B are directly attached to the rotating flanges (drive shafts) 22A and 22B of the hydraulic motors 21A and 21B via the coupling tools 23A and 23B, respectively. Linked to the 21A and 21B sides. The mounts of the hydraulic motors 21A and 21B are fixed to the vehicle body 2, that is, the front frame.

  An engine (an example of a drive source) 25 is provided on the vehicle body 2 side, and one constant displacement hydraulic pump (an example of a hydraulic pump) 30 is directly attached to the engine 25. The constant displacement type so that one constant displacement type hydraulic pump 30 corresponds to the two hydraulic motors 21A and 21B, that is, a one-pump two-motor type hydraulic drive system (HST system). The main supply pipe 32 from the port 31 in the hydraulic pump 30 includes branch supply pipes (such as hydraulic hoses) 32A and 32B, proportional electromagnetic switching valves (control valves) 37A and 37B, and supply and discharge pipes (such as hydraulic hoses) 33A and 33B. , 34A, 34B are connected to both ports 35A, 35B, 36A, 36B in the hydraulic motors 21A, 21B. Reference numeral 39 denotes a discharge pipe.

  Here, the proportional electromagnetic switching valves 37A and 37B are interposed to switch between forward and reverse rotation and stop of the hydraulic motors 21A and 21B, respectively. In the branch supply pipes 32A and 32B from the hydraulic pump 30 to the proportional electromagnetic switching valves 37A and 37B, a proportional electromagnetic throttle valve (proportional electromagnetic valve) that restricts the flow rate by detecting the slip of the corresponding front wheels 3A and 3B. Example) 38A and 38B are interposed. Here, the switching signals 37a and 37b to the proportional electromagnetic switching valves 37A and 37B and the control signals 38a and 38b to the proportional electromagnetic throttle valves 38A and 38B are configured to be output from the controller 40.

  That is, the controller 40 includes a forward / reverse switching signal 41 a from a forward / reverse switching switch 41 operated by a forward / reverse switching lever (change lever) 50 provided in the driver's seat 5, and a steering wheel turning angle sensor provided on the handle 16. 42, the turning angle signal 42a from the front wheel 42, the rotation speed signals 43a and 43b from the rotation sensors 43A and 43B provided corresponding to the front wheels 3A and 3B, and the vehicle speed command signal 51a from the electric accelerator pedal 51, The brake signal 52a from the electric brake pedal 52 is input.

  Then, if a difference greater than the rotation difference between the left and right front wheels 3A, 3B controlled by the handle 16 occurs, it is regarded as a slip shape, and the control is output from the controller 40 to each proportional electromagnetic throttle valve 38A, 38B based on the detection. Based on the signals 38a and 38b, the proportional electromagnetic throttle valves 38A and 38B on the side having a higher rotational speed than the predetermined rotational speed determined by the steering angle are operated to reduce the flow rate. Further, the rotation difference, forward / reverse rotation, and stop of each front wheel 3A, 3B are controlled by switching signals 37a, 37b output from the controller 40 to the proportional electromagnetic switching valves 37A, 37B. The left and right rear wheels 4A and 4B are provided so as to be able to turn around the longitudinal axis 27A and 27B with respect to the vehicle body 2, respectively.

Hereinafter, the operation in the first embodiment will be described.
1, 2, and 5 (a) show a normal forward travel time. At this time, the left and right front wheels 3A, 3B and the left and right rear wheels 4A, 4B are oriented in the front-rear direction. Further, both proportional electromagnetic switching valves 37A, 37B are in the forward communication state when one is on (excitation), and the proportional electromagnetic throttle valves 38A, 38B are in a normal communication state.

  Such a forklift 1 can run by an operator sitting on the seat 15 of the driver's seat 5 operating the handle 16. At that time, the forward / reverse travel is performed by the forward / reverse switching lever 50, and the forward / reverse switching signal 41a from the forward / reverse switching switch 41 by the operation is input to the controller 40. By switching the switching valves 37A and 37B, the flow direction of the hydraulic oil from the constant displacement hydraulic pump 30 is switched, and the rotation direction of the hydraulic motors 21A and 21B is changed.

  That is, in FIG. 1 in which both proportional electromagnetic switching valves 37A and 37B are on, hydraulic fluid from port 31 is supplied to main supply pipe 32, branch supply pipes 32A and 32B, proportional electromagnetic throttle valves 38A and 38B, By supplying to the ports 35A and 35B via the proportional electromagnetic switching valves 37A and 37B and the supply / discharge pipes 33A and 33B, the front wheels 3A and 3B can be rotated forward via the hydraulic motors 21A and 21B to be in forward travel. . Further, in FIG. 3 in which both proportional electromagnetic switching valves 37A and 37B are on, hydraulic fluid from the port 31 is supplied to the main supply pipe 32, branch supply pipes 32A and 32B, proportional electromagnetic throttle valves 38A and 38B, By supplying to the ports 36A and 36B via the proportional electromagnetic switching valves 37A and 37B and the supply / discharge pipes 34A and 34B, the front wheels 3A and 3B can be reversely rotated via the hydraulic motors 21A and 21B to be in reverse travel. .

  Further, by inputting the vehicle speed command signal 51a into the controller 40 by the accelerator pedal 51, the number of revolutions of the engine 25, that is, the hydraulic pressure (flow rate of hydraulic oil) from the constant displacement hydraulic pump 30 is controlled. , 21B is changed to control the speed. Stopping and the like can be performed by inputting a brake signal 52 a into the controller 40 by the brake pedal 52.

  The turning control is performed by the operator sitting on the seat 15 of the driver's seat 5 operating the handle 16, and the traveling speed is changed at this time by changing the steering wheel turning angle sensor based on the turning angle (rotation angle) of the handle 16. 42, the cutting angle signal 42a from the controller 42 is input to the controller 40, and the proportional electromagnetic switching valves 37A and 37B are switched and controlled by the switching signals 37a and 37b from the controller 40 to control the rotational speed and direction of the hydraulic motors 21A and 21B. You can do that. That is, it can be performed by controlling the rotation speed and rotation direction of both hydraulic motors 21A and 21B according to the turning angle of the handle 16 as follows.

  That is, when the handle 16 is in a neutral position, as shown in FIG. 1 described above, both proportional electromagnetic switching valves 37A and 37B are on, so that the left and right hydraulic pressures are as shown in FIG. The rotational speeds of the motors 21A and 21B are the same and go straight.

  When the steering wheel turning angle is small, the proportional electromagnetic switching valve 37B is throttled by the switching signal 37b output from the controller 40 to the proportional electromagnetic switching valve 37B inside the turn based on the turning angle signal 42a entering the controller 40. Thus, the hydraulic motor 21B inside the turning is rotated at a low speed. As a result, as shown in FIG. 5 (b), turning can be performed by rotating the front wheel 3B inside the turning at a low speed by rotating in the same direction in the left and right directions, and thereby making a difference in the number of rotations on the left and right.

  When the steering wheel turning angle is intermediate, the switching signal 37b from the controller 40 to the proportional electromagnetic switching valve 37B inside the turning is stopped based on the turning angle signal 42a entering the controller 40, and the proportional electromagnetic switching valve 37B is turned off. (Non-excitation) results in a communication stop state, and thus the rotation of the hydraulic motor 21B inside the turning is stopped. As a result, as shown in FIG. 5C, only the front wheel 3A on the outside of the turn is rotated, and thus pivoting can be performed.

  When the steering angle is larger than the middle, the proportional electromagnetic switching valve 37B is controlled by the switching signal 37b output from the controller 40 to the proportional electromagnetic switching valve 37B inside the turn based on the cutting angle signal 42a entering the controller 40. The other side is switched on and the aperture is controlled, so that the hydraulic motor 21B on the inner side of the turning is rotated in the reverse direction at a low speed. As a result, as shown in FIG. 5 (d), the front wheel 3B on the inside of the turn is rotated at a low speed by rotation in the left and right direction, so that the pivoting can be performed.

  Further, when the steering angle is maximum (handle lock), the proportional electromagnetic switching valve is output from the controller 40 to the proportional electromagnetic switching valve 37B on the inside of the turn based on the cutting angle signal 42a entering the controller 40. 37B is controlled to be switched to the other ON state, so that the hydraulic motor 21B on the inner side of the turn is rotated in the reverse direction. As a result, as shown in FIG. 5 (e), the left and right hydraulic motors 21A and 21B, that is, the front wheels 3A and 3B are rotated in the opposite directions and the rotation speed is the same, thereby minimizing the turning radius. You can do a spin turn.

  5 (b) to FIG. 5 (e) show the case of a right turn, the left turn is similarly performed by reversing the cutting direction of the handle 16. . Further, although the case of forward movement is shown, the same operation is performed in the case of backward movement in the state of FIG. When turning left and right, the left and right rear wheels 4A and 4B in the form of a turning caster are turned.

  During normal running as described above, of the pair of left and right front wheels 3A and 3B, one front wheel, for example, the right front wheel 3B is on the soft ground, and the other left front wheel 3A is on the dry ground. In this case, the front wheel 3B on the soft ground is in an idle state, and no driving force is generated on the front wheel 3A on the dry ground. At this time, the rotation speed signals 43a and 43b from the both rotation sensors 43A and 43B are compared in the controller 40, and if a difference equal to or greater than the rotation difference between the left and right front wheels 3A and 3B controlled by the handle 16 occurs, it is regarded as a slip state. Detected.

  Then, based on this detection, the proportional electromagnetic throttle valve 38B corresponding to the front wheel 3B on the soft ground, that is, the proportional electromagnetic throttle valve on the side having a higher rotational speed than the predetermined rotational speed determined by the steering angle is controlled. A signal 38b is output, and the proportional electromagnetic throttle valve 38B is throttled.

  As a result, the amount of hydraulic oil supplied to the hydraulic motor 12B corresponding to the front wheel 3B on the soft ground is reduced, the right rear wheel 11B that has been idling is rotated at a low speed, and the front wheel 3A on the dry ground is also supported. The amount of hydraulic oil supplied to the hydraulic motor 12A is increased. Therefore, in the hydraulic motor 12A corresponding to the front wheel 3A on the dry ground, the pressure of the hydraulic oil rises, so that the front wheel 3A on the dry ground can be rotated with a large driving force so as to be able to travel and enter the soft ground. You can escape from the state.

  When the left front wheel 3A slips on a soft ground or the like, a control signal 38a is output to the proportional electromagnetic throttle valve 38A corresponding to the left front wheel 3A, and the proportional electromagnetic throttle valve 38A is throttled. It can act in the same manner as described above.

  As a result, it is possible to always obtain a sufficient driving force for escape while having a simple and inexpensive configuration in which proportional electromagnetic throttle valves 38A and 38B are interposed in ordinary piping. In addition, since the proportional electromagnetic throttle valves 38A and 38B can be automatically controlled via the controller 40 by slip detection, the flow rate can be accurately and reliably controlled.

In such a forklift 1, an operator sitting on the seat 15 of the driver's seat 5 operates the lift cylinder 11 by operating the lift lever, for example, so that the fork 13 is moved to the mast 6 via the lift bracket 12 or the like. It can be moved up and down along the way, so that the expected fork work can be performed. Further, by operating the tilting lever 8 by operating the tilting lever 8, the mast 6 can be rotated (tilted) around the connecting shaft 7, so that the posture of the fork 13 can be changed via the lift bracket 12 or the like. .
[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG.

  The proportional electromagnetic throttle valves 38A and 38B are removed from the first embodiment described above. According to the second embodiment, during normal running, one of the pair of left and right front wheels 3A and 3B, one front wheel, for example, the right front wheel 3B is on the soft ground, and the other left front wheel 3A is When the vehicle is on the dry ground, the front wheel 3B on the soft ground is in an idle state, and no driving force is generated on the front wheel 3A on the dry ground. At this time, the rotation speed signals 43a and 43b from the both rotation sensors 43A and 43B are compared in the controller 40, and if a difference equal to or greater than the rotation difference between the left and right front wheels 3A and 3B controlled by the handle 16 occurs, it is regarded as a slip state. Detected.

  Then, based on this detection, control is performed to the proportional electromagnetic switching valve 37B corresponding to the front wheel 3B on the soft ground, that is, the proportional electromagnetic switching valve on the side having a higher rotational speed than the predetermined rotational speed determined by the steering angle. A signal 37b is output, and the proportional electromagnetic switching valve 37B is throttled.

  As a result, the amount of hydraulic oil supplied to the hydraulic motor 12B corresponding to the front wheel 3B on the soft ground is reduced, the right rear wheel 11B that has been idling is rotated at a low speed, and the front wheel 3A on the dry ground is also supported. The amount of hydraulic oil supplied to the hydraulic motor 12A is increased. Therefore, in the hydraulic motor 12A corresponding to the front wheel 3A on the dry ground, the pressure of the hydraulic oil rises, so that the front wheel 3A on the dry ground can be rotated with a large driving force so as to be able to travel and enter the soft ground. You can escape from the state.

  When the left front wheel 3A idles on a soft ground or the like, a control signal 37a is output to the proportional electromagnetic switching valve 37A corresponding to the left front wheel 3A, and the proportional electromagnetic switching valve 37A is throttled. It can act in the same manner as described above.

  As a result, the valve for switching the forward / reverse rotation of the hydraulic motors 21A and 21B interposed in the normal piping is replaced with the proportional electromagnetic switching valves 37A and 37B. Sufficient driving force can be obtained. In addition, the proportional electromagnetic switching valves 37A and 37B can be automatically controlled via the controller 40 by slip detection, so that the flow rate can be accurately and reliably controlled.

  In the first and second embodiments described above, two sets (four-wheel type) are shown before and after the pair of left and right front wheels 3A and 3B and the pair of left and right rear wheels 4A and 4B. It may be a large traveling carriage of a type in which a pair of left and right wheels and a plurality of front and rear wheels are provided. In this case, all the sets may be configured as drive wheels, or some of the sets may be configured as drive wheels in the manner of the first and second embodiments.

In the first embodiment described above, the proportional electromagnetic throttle valves 38A and 38B are used as the proportional electromagnetic valves, but this may be a proportional electromagnetic flow rate adjusting valve or the like.
In the first and second embodiments described above, the counter-type forklift 1 is shown as an industrial vehicle. However, this may be an industrial vehicle (forklift) having a traversing system. In this case, a variable displacement hydraulic pump or the like is used as the hydraulic pump.

  In the above-described first and second embodiments, the pair of left and right rear wheels 4A and 4B employs a swivel caster type that is turned around, but this is one of the pair of left and right rear wheels 4A and 4B. The rear wheel 4 may be steered forcibly by a cylinder or the like by a handle wheel, and the other rear wheel 4 may be of a turning caster type.

In the first and second embodiments described above, the engine 25 is shown as the drive source of the constant displacement hydraulic pump 30, but this may be an electric motor or the like.
In the first and second embodiments described above, the travel speed at the time of turning is changed by controlling the rotational speeds of the hydraulic motors 21A and 21B according to the turning angle of the handle 16. The speed may be determined by controlling the rotation speed of the hydraulic motors 21A and 21B by the accelerator pedal 51 regardless of the turning angle of the handle 16.

  In the above-described first and second embodiments, the counter-type forklift 1 is shown as an industrial vehicle. However, the industrial vehicle works in the same way even if it is a large transport vehicle, a loader, a side forklift, or the like. To get.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway plan view of a hydraulic circuit portion during forward traveling in a hydraulic drive type industrial vehicle according to a first embodiment of the present invention. It is a side view at the time of normal driving | running | working in the industrial vehicle of the hydraulic drive type. FIG. 3 is a partially cutaway plan view of a hydraulic circuit portion during reverse travel in the industrial vehicle of the same hydraulic drive type. It is a system block diagram in the industrial vehicle of the hydraulic drive type. It is a schematic plan view explaining the steering state in the industrial vehicle of the same hydraulic drive type. FIG. 5 is a partially cutaway plan view of a hydraulic circuit portion during forward traveling in an industrial vehicle of hydraulic drive type, showing Embodiment 2 of the present invention.

Explanation of symbols

1 Forklift (industrial vehicle)
2 Body 3A Front wheel (drive wheel)
3B Front wheel (drive wheel)
4A Rear wheel 4B Rear wheel 13 Fork 16 Handle 21A Hydraulic motor 21B Hydraulic motor 25 Engine (drive source)
30 Constant displacement hydraulic pump (hydraulic pump)
32 Main supply piping 32A Branch supply piping 32B Branch supply piping 33A Supply / exhaust piping 33B Supply / exhaust piping 34A Supply / exhaust piping 34B Supply / exhaust piping 37A Proportional electromagnetic switching valve 37a Switching signal 37B Proportional electromagnetic switching valve 37b Switching signal 38A Proportional solenoid valve)
38a Control signal 38B Proportional solenoid throttle valve (proportional solenoid valve)
38b Control signal 40 Controller 41 Forward / reverse changeover switch 41a Forward / reverse changeover signal 42 Steering wheel turning angle sensor 42a Turning angle signal 43A Rotation sensor 43a Rotation speed signal 43B Rotation sensor 43b Rotation speed signal 50 Forward / backward switching lever 51 Accelerator pedal 51a Vehicle speed command Signal 52 Brake pedal 52a Brake signal

Claims (4)

  The vehicle body is provided with a plurality of pairs of left and right wheels on the front and rear, and at least one set of wheels is configured as a drive wheel linked to a hydraulic motor, and one hydraulic pump is provided on the vehicle body side. In the piping from the hydraulic pump to each hydraulic motor, a proportional electromagnetic switching valve is provided for reducing the flow rate by detecting the slip state of the corresponding drive wheel and switching the forward / reverse rotation of the hydraulic motor. Hydraulic drive type industrial vehicle characterized by   The vehicle body is provided with a plurality of pairs of left and right wheels on the front and rear, and at least one set of wheels is configured as a drive wheel linked to a hydraulic motor, and one hydraulic pump is provided on the vehicle body side. In the piping from the hydraulic pump to each hydraulic motor, a proportional solenoid valve for reducing the flow rate by detecting the slip state of the corresponding drive wheel and a proportional solenoid switching valve for switching forward / reverse rotation of the hydraulic motor are interposed. Hydraulic drive type industrial vehicle characterized by   If a difference greater than the rotation difference between the left and right drive wheels controlled by the steering wheel occurs, it is regarded as a slip, and by detecting this, a proportional electromagnetic switching valve on the side with a higher rotation speed than the predetermined rotation speed determined by the steering angle 3. The hydraulic drive type industrial vehicle according to claim 1, wherein the flow rate is reduced by operating a proportional solenoid valve. 4. The hydraulic drive type industrial vehicle according to claim 2, wherein the proportional solenoid valve is a proportional solenoid throttle valve.

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