초록 ▼

A drive control apparatus for a forklift. Based on the load state, it is determined whether to limit a maximum vehicle speed and an acceleration/deceleration during traveling of the forklift. Limitation contents regarding the maximum vehicle speed and the acceleration/deceleration is determined base

A drive control apparatus for a forklift. Based on the load state, it is determined whether to limit a maximum vehicle speed and an acceleration/deceleration during traveling of the forklift. Limitation contents regarding the maximum vehicle speed and the acceleration/deceleration is determined based on a determination result of whether to put the limitations. A speed of the engine is adjusted based on the determined limitation contents, thereby controlling driving of the forklift. When the determined limitation contents are changed, an acceleration/deceleration limitation value is selected from a plurality of acceleration/deceleration limitation values according to the pattern of the change of the limitation contents, and drive control related to the acceleration/deceleration is executed to limit the acceleration/deceleration of the forklift by using the selected acceleration/deceleration limitation value.

대표청구항 ▼

The invention claimed is: 1. A drive control apparatus for a forklift, the forklift including an engine, a drive wheel, a power transmission mechanism for transmitting power of the engine to the drive wheel, and a loading device that is provided at a front portion of the forklift and mounts a load,

The invention claimed is: 1. A drive control apparatus for a forklift, the forklift including an engine, a drive wheel, a power transmission mechanism for transmitting power of the engine to the drive wheel, and a loading device that is provided at a front portion of the forklift and mounts a load, the drive control apparatus comprising: a load state determining section, wherein the load state determining section detects a load state of the loading device, and, based on the detected load state, determines whether to limit a maximum vehicle speed and an acceleration/deceleration during traveling of the forklift; a limitation contents determining section that determines limitation contents regarding the maximum vehicle speed and the acceleration/deceleration based on a determination result of the load state determining section, wherein, when the determination result of the load state determining section is negative, the limitation contents determining section determines not to limit the maximum vehicle speed and the acceleration/deceleration, and wherein, when the determination result of the load state determining section is positive, the limitation contents determining section selects, from a plurality of maximum vehicle speed limitation values and a plurality of acceleration/deceleration limitation values that are previously set according to load states, a maximum vehicle speed limitation value and an acceleration/deceleration limitation value that are appropriate for the detected load state; and a control section that adjusts a speed of the engine based on the limitation contents determined by the limitation contents determining section, thereby controlling driving of the forklift, wherein, when the limitation contents determined by the limitation contents determining section are changed, the control section executes drive control related to the maximum vehicle speed according to the limitation contents that are set after the change, and the control section selects an acceleration/deceleration limitation value from the acceleration/deceleration limitation values according to the pattern of the change of the limitation contents and executes drive control related to the acceleration/deceleration to limit the acceleration/deceleration of the forklift by using the selected acceleration/deceleration limitation value. 2. The drive control apparatus according to claim 1, further comprising an acceleration instructing device that is operated by a driver to instruct acceleration of the forklift, the acceleration instructing device being configured to instruct acceleration when in an operated state and not to instruct acceleration when in a non-operated state, wherein, in a case where the limitation contents are changed, the control section executes the drive control while the operated state of the acceleration instructing device continues, ends the drive control when the acceleration instructing device is shifted to the non-operated state, and returns the acceleration/deceleration limitation value to the acceleration/deceleration limitation value that corresponds to the limitation contents that are set after the change made by the limitation contents determining section. 3. The drive control apparatus according to claim 1, wherein, when the limitation contents are changed from an unlimited state in which the maximum vehicle speed and the acceleration/deceleration are not limited to a limited state where the maximum vehicle speed and the acceleration/deceleration are limited or when the limitation contents are changed from the limited state to the unlimited state, the control section selects the smallest value of the acceleration/deceleration limitation values, and executes the drive control by using the selected smallest acceleration/deceleration limitation value. 4. The drive control apparatus according to claim 1, wherein the load state determining section determines whether to limit the maximum vehicle speed and the acceleration/deceleration based on a determination condition that includes at least one of a height of the loading device and the weight of a load mounted on the loading device, wherein, in a case where the determination results of the load state determining section is positive, the limitation contents determining section selects a smaller maximum vehicle speed limitation value and a smaller acceleration/deceleration limitation value as the load state indicates a higher height or a greater weight, and wherein, in a case where the limitation contents are changed with the limitations being put, the control section executes the drive control by using the acceleration/deceleration limitation value that is set before the change if the acceleration/deceleration limitation value that is set after the change is greater than the acceleration/deceleration limitation value that is set before the change. 5. The drive control apparatus according to claim 4, wherein the load state determining section detects a vehicle speed and the weight of the load, and, until the detected vehicle speed surpasses a predetermined reference value, the load state determining section determines whether to limit the maximum vehicle speed and the acceleration/deceleration based on the detected weight of the load, and wherein, after the vehicle speed reaches the reference value, the load state determining section sets, as a fixed value, the weight of the load detected at the time when the vehicle speed reaches the reference value, and determines whether to limit the maximum vehicle speed and the acceleration/deceleration by using the fixed value. 6. The drive control apparatus according to claim 1, wherein the load state determining section determines whether to limit the maximum vehicle speed and the acceleration/deceleration based on the load state and a steered angle of a steered wheel of the forklift, and wherein, when the determination result of the load state determining section is positive, the limitation contents determining section selects, from a plurality of maximum vehicle speed limitation values and a plurality of acceleration/deceleration limitation values, which are previously set according to steered angles, a maximum vehicle speed limitation value and an acceleration/deceleration limitation value that are appropriate for the steered angle. 7. The drive control apparatus according to claim 1, wherein the control section computes a difference between an actual vehicle speed and a target vehicle speed, and adjusts the speed of the engine to realize an acceleration/deceleration that corresponds to the difference, and wherein, at start of the forklift from a stopped state, the control section sets, until the actual vehicle speed reaches a restoration speed that is a value of a predetermined ratio to a maximum vehicle speed limitation value determined to be appropriate for the load state, a starting limitation value that is greater than the maximum vehicle speed limitation value, and adjusts the engine speed by using the starting limitation value, and wherein, when the actual vehicle speed reaches or surpasses the restoration vehicle speed, the control section adjusts the engine speed by using the maximum vehicle speed limitation value. 8. The drive control apparatus according to claim 7, wherein the starting limitation value is a constant value, wherein, in a case where the actual vehicle speed falls below the restoration speed after reaching or surpassing the restoration speed, the control section adjusts the engine speed by using the starting limitation value when the actual vehicle speed falls to or below a hysteresis speed that is lower than the restoration speed. 9. The control apparatus according to claim 7, wherein the starting limitation value is set to a constant value until the actual vehicle speed reaches a limitation value reduction starting speed that is lower than the restoration speed, and wherein, when the actual vehicle speed is equal to or greater than the limitation value reduction starting speed, the starting limitation value is reduced to the maximum vehicle speed limitation value as the actual vehicle speed increases. 10. A drive control method for a forklift, the forklift including an engine, a drive wheel, a power transmission mechanism for transmitting power of the engine to the drive wheel, and a loading device that is provided at a front portion of the forklift and mounts a load, the drive control method comprising: detecting a load state of the loading device, and determining, based on the detected load state, whether to limit a maximum vehicle speed and an acceleration/deceleration during traveling of the forklift; determining limitation contents regarding the maximum vehicle speed and the acceleration/deceleration based on a determination result of whether to put the limitations, wherein, when the determination result is such that the limitations should not be put, it is determined not to limit the maximum vehicle speed and the acceleration/deceleration, and wherein, when the determination result is such that the limitations should be put, a maximum vehicle speed limitation value and an acceleration/deceleration limitation value that are appropriate for the detected load state are selected from a plurality of maximum vehicle speed limitation values and a plurality of acceleration/deceleration limitation values that are previously set according to load states; and adjusting a speed of the engine based on the determined limitation contents, thereby controlling driving of the forklift, wherein, when the determined limitation contents are changed, drive control related to the maximum vehicle speed is executed according to the limitation contents that are set after the change, an acceleration/deceleration limitation value is selected from the acceleration/deceleration limitation values according to the pattern of the change of the limitation contents, and drive control related to the acceleration/deceleration is executed to limit the acceleration/deceleration of the forklift by using the selected acceleration/deceleration limitation value.