JPH0585380B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a switchback travel control device for a vehicle equipped with an automatic transmission, particularly for a cargo handling vehicle such as a forklift.

(Prior Art) In recent years, various vehicles equipped with automatic transmissions have been proposed, and cargo handling vehicles such as forklifts equipped with automatic transmissions have also been proposed. On the other hand, in cargo handling vehicles such as forklifts, it is necessary to frequently switch between forward and reverse travel during cargo handling operations, so when switching the direction of travel from forward to reverse or from reverse to forward, the driver must ,
A switchback mechanism in which the vehicle speed is reduced to a certain degree before the vehicle comes to a secure stop, and the forward/reverse control lever is operated to change the direction point from forward to reverse or from reverse to forward, and the clutch is engaged. I was running.

(Problem to be Solved by the Invention) Since the weight of the cargo loaded on a vehicle during cargo handling work is not constant, the amount of deceleration of the vehicle during the switchback operation and the timing of switching the forward/reverse operation lever depend on the weight of the cargo. Need to change.
However, conventionally, the amount of deceleration and the timing of switching the forward/reverse operation lever have been determined based on the long experience and intuition of the driver. Therefore, there are inconveniences such as damage to the transmission due to forcible switchback driving at a vehicle speed in which forward/reverse switching is not possible, and cargo movement due to sudden deceleration.

Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes a load detector that detects the weight of the cargo and a device that operates the forward/reverse operation lever while the vehicle is running. A memory in which the relationship between negative acceleration and load suitable for performing switchback driving in which the direction point coincides with the direction of travel at that time and the direction point in the opposite direction of travel is performed is stored as data. a vehicle speed detector for detecting the traveling speed of the vehicle; a brake driving means for adjusting the braking state of the brake; and a switchback driving device based on the load detected by the load detector and the data stored in the storage device. indexing means for determining a suitable negative acceleration; control means for controlling the brake drive means so that the negative acceleration determined by the indexing means is achieved; A clutch drive means and a transmission drive are configured to switch the automatic transmission from a gear engagement corresponding to the current running direction to a gear engagement in the opposite direction to the current running direction when deceleration occurs, and to connect the clutch when the switching is completed. A configuration is adopted in which a switching control means for operating the means is provided.

(Operation) In the present invention, when performing switchback travel, the brake drive means is driven to automatically apply the brakes so that a suitable negative acceleration corresponding to the load detected by the load detector is obtained. When the traveling speed of the vehicle is decelerated to a predetermined speed, the switching control means switches the automatic transmission from a gear engagement corresponding to the current traveling direction to a gear engagement in the opposite direction to the current traveling direction, and the switching is performed. When completed, the clutch drive means and transmission drive means are actuated to engage the clutch.

(Example) An example in which the present invention is embodied in a forklift will be described below with reference to the drawings.

Figure 1 shows the mechanism of the drive system of a forklift.The output of the engine 1 is transmitted to the automatic transmission 3 via a dry single plate clutch 2, and the automatic transmission 3 is used for driving via a differential gear mechanism 4. The driving wheels 5 are driven forward and backward at a predetermined gear ratio. The engine 1 also includes a lift cylinder 7 for raising and lowering the fork 6.
It is also used as a drive source for a hydraulic pump that supplies hydraulic oil to a tail cylinder 8 for tilting a mast (not shown).

The connection state of the dry single-plate clutch 2 for turning on and off the output of the engine 1 is adjusted in accordance with the stroke amount of a rod 9a that expands and contracts based on the drive of a clutch control actuator 9 as a clutch driving means. Ru. On the other hand, the automatic transmission 3 can be shifted between 1st speed (low speed) and 2nd speed (high speed) by driving the shift switching actuator 10, and the forward/forward switching actuator 11
It is possible to switch between forward travel, neutral (neutral), and reverse travel by driving the vehicle.

Next, an electric circuit for driving and controlling each of the actuators 9 to 11 will be explained with reference to FIG. 2.

The vehicle speed sensor 12 detects the rotational speed of the output shaft of the automatic transmission 3, as shown in FIG. 1, and outputs the detection signal to the input/output interface 13. The forward/reverse movement detection sensor 14 detects the switching state (forward, neutral,
In other words, the direction point is detected and the detected signal is output to the interface 13.

The load detection sensor 16 as a load detector that detects the weight of the cargo is composed of a pressure sensor, and is based on the hydraulic pressure of the hydraulic oil in the lift cylinder 7, that is, the fork 6.
The weight of the cargo 17 is detected, and the detected signal is converted into a digital signal by the A/D converter 18 and output to the interface 13.

The backward tilt angle of the fork 6 is detected from the stroke amount of the rod of the tail cylinder 8, and the stroke detection sensor 19 that detects the stroke is composed of a potentiometer, and the detection signal is converted into a digital signal by the A/D converter 20. It is converted and output to the interface 13.

The microcomputer 21 as an indexing means and a switching control means is a central processing unit (hereinafter referred to as
A program memory 23 consisting of a read-only memory (ROM) that stores control programs, and a working memory 24 consisting of a readable and rewritable memory (RAM) that temporarily stores arithmetic processing results, etc. , the CPU 22 operates based on program data stored in the program memory 23.

In addition to the control program, the program memory 23 previously stores data on the relationship between negative acceleration suitable for switchback travel and the weight of the cargo, that is, the load.

The CPU 22 is the input/output interface 13
Detection signals from each of the sensors are input through the sensor. The CPU 22 sequentially calculates the running speed and acceleration of the forklift at that time based on the detection signal from the vehicle speed sensor 12, and stores the calculation results in the working memory 24. Also, CPU22
determines the direction point of the forward/reverse operating lever 15 at that time based on the detection signal from the forward/reverse detecting sensor 14.

Furthermore, the CPU 22 controls the load detection sensor 16.
The weight of the cargo at that time, that is, the load, is calculated based on the detection signal from the , and the calculation result is stored in the working memory 24. Further, the CPU 22 calculates the backward inclination angle of the fork based on the detection signal from the stroke detection sensor 19, and stores it in the working memory 24.

Note that each calculation and judgment of these detection signals by the CPU 22 is performed based on data stored in the program memory 23 in advance.

Further, the CPU 22 controls the input/output interface 13 and each actuator drive circuit 25, 26, 27, 2 based on predetermined program data.
8, a clutch control actuator 9, a forward/reverse switching actuator 11, a brake actuating actuator 29, and a control valve drive device 30 for the tail cylinder 8 are driven and controlled, respectively.

When the CPU 22 determines that the forward/reverse operation lever 15 has been switched to neutral while driving,
Driving determination processing operation, that is, processing operation for determining whether the neutral operation of the forward/reverse operation lever 15 performed by the driver is an operation for performing switchback driving, elliptical shift driving, or coasting driving is now executed. There is. Based on the determination result, the CPU 22 drives the clutch control actuator 9 and the forward/reverse switching actuator 11 according to a predetermined program to perform switchback driving, coasting shift driving, or coasting driving. It's starting to be controlled.

Further, when the CPU 22 determines to perform switchback travel, it brakes the forklift to achieve the negative acceleration according to the weight of the cargo 17, based on the relationship between the load and the optimal negative acceleration shown in FIG. 31 is operated. Further, if the fork 6 is not in the completely backward tilted state, the fork 6 is controlled to be in the completely backward tilted state before the forward/reverse gear change is completed.

Next, the operation of the electric block circuit constructed as described above will be explained with reference to the flowcharts shown in FIGS. 4 and 5.

Now, while the forklift is traveling forward at a predetermined speed, the driver presses the forward/reverse operation lever 15.
When switching from forward to neutral, CPU2
2 determines that the direction point has been switched to neutral based on the detection signal from the forward/reverse motion detection sensor 14 (step S1), and activates the clutch control actuator 9 via the interface 13 and actuator drive circuit 25. The drive is controlled to disengage the dry single plate clutch 2 at the maximum speed (step S2). At the same time, CPU22
A built-in timer is activated to set a predetermined time (hereinafter referred to as set time t, in this example, 1 second).
During the process, it is determined whether the forward/reverse operating lever 15 has been switched to a direction point other than neutral (steps S3 and S4).

When the forward/reverse operation lever 15 is not operated and the direction point remains unchanged even after the set time t has elapsed, the CPU 22 executes coasting control processing to cause the forklift to coast (step S5). In other words, CPU22
In response to the time-up, it is determined that the vehicle is coasting, and after driving and controlling the forward/reverse switching actuator 11 to change the gear of the automatic transmission 3 from forward to neutral, the disconnected dry single plate clutch 2 is connected. Therefore, the forklift travels in an elliptical manner in this state.

On the other hand, when the forward/reverse operation lever 15 is switched to forward again within the set time t, the CPU 2
Step 2 is determined to be an elliptical shift (step S6), and an elliptical shift control processing operation is executed to make the forklift move forward again (step S7). That is, the CPU 22 simply engages the dry veneer clutch 2 in response to the direction point being switched back to forward. Therefore, the forklift will continue moving forward again. Further, when the operating lever 15 is switched to reverse within the set time t, the CPU 22 determines that the forklift is traveling in switchback mode (step S6), and executes a switchback control processing operation to cause the forklift to travel in switchback mode (step S8). .

When switchback driving control starts
The CPU 22 determines whether there is any cargo based on the detection signal from the load detection sensor 16 (step S9). Then, if there is cargo, the weight of the cargo is calculated (step S10), and the program memory 2
A suitable negative acceleration corresponding to the load is calculated based on the data stored in advance in Step 3 (Step S11). Then, the brake actuator 29 is drive-controlled via the input/output interface 13 and the actuator drive circuit 27 so that the negative acceleration is obtained (step S12), and the forklift is decelerated. At this time, CPU22
calculates the vehicle speed based on the detection signal from the vehicle speed sensor 12, calculates the negative acceleration from the change in the vehicle speed, and successively determines whether the forklift is being decelerated by a predetermined negative acceleration.

Further, when the fork 6 has the cargo 17, the CPU 22 determines whether or not the fork 6 is completely tilted backward based on the detection signal of the stroke detection sensor 19 (step S13). If the fork 6 is not in a completely backward tilted state, an increment in rearward tilt to make it fully backward tilted is calculated (step S14), and the control valve drive device 30 and drives the tail cylinder 8 by an amount corresponding to the rearward tilt increase (step S15).

When the speed, which is sequentially calculated based on the detection signal from the vehicle speed sensor 12, becomes less than a predetermined speed at which the gear can be changed from forward to reverse, the CPU 22 drives and controls the actuator 11 for forward/reverse switching via the actuator drive circuit 26. and switches the gear of the automatic transmission 3 from forward to reverse (step S16).

When the gear of the automatic transmission 3 is switched from forward to reverse (step S16), control is performed to reverse the traveling direction of the forklift (step S17). That is, the clutch 2 is connected and the forklift is further decelerated, and the brake actuator 29 is driven in a direction to release the brake 31. Immediately after the forklift decelerates and stops, it reverses its traveling direction and begins traveling backwards (step S17). and,
After the reversal of the traveling direction is completed, the control valve driving device 30 is operated so that the fork backward inclination angle is in the initial state.
The tail cylinder 8 is actuated via (step S18).

On the other hand, if there is no cargo when the switchback travel is started, the brake actuator 29 is controlled to operate the brake 31 so that the maximum negative acceleration is obtained (step S19).
Then, after step S19 is executed, step
Each operation after S16 is executed in the same manner as described above.

In this case, although the explanation has been made regarding traveling from forward to reverse, switchback traveling from reverse to forward is also performed by the same processing operation.

As described above, in the present invention, the brakes are automatically applied in accordance with the weight of the cargo 17 to obtain negative acceleration during switchback travel, and the vehicle is decelerated to a predetermined speed that allows forward and forward switching. Since the gears are automatically switched and the clutch is connected, ideal deceleration is always possible regardless of the skill of the driver, the presence or absence of cargo, and changes in weight, which can cause loss of weight balance and collapse of the load during deceleration. There is no risk of damage to the automatic transmission.

Furthermore, in the device of this embodiment, the fork is tilted completely backward before the direction of travel is reversed from forward to reverse or from reverse to forward during switchback travel, so the forklift is tilted completely backwards, so the forklift reverses the direction of travel. This reliably prevents the inconvenience of the cargo moving due to inertia when the cargo is moved.

Note that the present invention is not limited to the embodiments described above, and for example, the drive amount of the brake 31 and the negative acceleration are calculated in accordance with the load, without constantly calculating the negative acceleration based on the detection signal from the vehicle speed sensor The relationship between the acceleration of
The drive control of the brake actuator 29 and the drive control of the tail cylinder 8 for completely tilting the fork 6 backward are performed in parallel,
Steps S13 to S15 and step S18 may be omitted. Further, although the above embodiment was applied to a forklift, it goes without saying that the invention may also be applied to other cargo handling vehicles such as a shovel loader.

Effects of the Invention As detailed above, according to the present invention, when a cargo handling vehicle equipped with an automatic transmission is traveling in a switchback mode, the gears can be automatically changed to a speed at which forward and forward gears can be changed in an optimal state according to the weight of the cargo. Therefore, the switchback control is performed while ensuring the safety of the cargo regardless of the skill of the driver, and there is no risk of damaging the transmission, etc., which is an excellent effect.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the mechanism of the drive system of a forklift embodying this invention, Fig. 2 is an electric block circuit diagram of the forklift, and Fig. 3 is a diagram showing the relationship between load and negative acceleration. , FIGS. 4 and 5 are flowcharts for explaining the operation. In the diagram, 1 is the engine, 2 is the dry single plate clutch,
3 is an automatic transmission, 6 is a fork, 7 is a lift cylinder, 8 is a tail cylinder, 9 is an actuator for clutch control, 11 is an actuator for forward/reverse switching, 12 is a vehicle speed sensor, 15 is a forward/reverse operation lever, 16 is a Load detection sensor, 19 is a stroke detection sensor, 21 is a microcomputer, 22
2 is a central processing unit (CPU), 23 is a program memory, 24 is a working memory, and 31 is a brake.

Claims (1)

[Scope of Claims] 1. A load detector that detects the weight of the cargo; and a device that operates a forward/reverse control lever while the car is running to change direction from a direction point that corresponds to the current direction of travel to a direction that is opposite to the direction of travel. A memory device that stores data on the relationship between negative acceleration and load suitable for switching to the lexion point for switchback driving, a vehicle speed detector that detects the vehicle's running speed, and a brake system. a brake driving means for adjusting the state; an indexing means for determining a negative acceleration suitable for switchback travel based on the load detected by the load detector and data stored in the storage device; a control means for controlling the brake driving means so as to achieve the determined negative acceleration; and when the traveling speed of the vehicle is reduced to a predetermined speed, the automatic transmission is changed from a gear connection corresponding to the current traveling direction. Cargo handling equipment equipped with an automatic transmission equipped with a switching control means that operates a clutch drive means and a transmission drive means to switch gear engagement in the direction opposite to the current traveling direction and connect the clutch when the switching is completed. Vehicle switchback travel control device.