JP5769006B2 - Vehicle steering system and cargo handling vehicle - Google Patents

Description

  The present invention relates to a vehicle steering apparatus for a cargo handling vehicle such as a forklift.

A hydraulic power steering device is usually used as a forklift steering device. The hydraulic power steering device drives the hydraulic pump to supply hydraulic oil to the hydraulic cylinder based on the driver's steering, moves the piston of the hydraulic cylinder, and steers the steered wheels.
Forklifts have a wide range of steering angles and a high frequency of steering for their applications. Therefore, the power consumption of the steering device is relatively large.

Japanese Patent Laid-Open No. 06-206572 JP 2004-123026 A

For turning when the vehicle is stopped (including when driving at very low speed, the same applies hereinafter), a larger turning force is required than when turning when the vehicle is running. Therefore, when a steering wheel operation performed when the vehicle is stopped, that is, a so-called “stationary operation” is performed, the power consumption becomes extremely large.
Forklifts may require a stationary operation for their use, but unnecessary stationary operations may be frequently performed because, for example, the driver is immature. As a result, the amount of power consumption increases and the battery is consumed quickly.

  Accordingly, an object of the present invention is to limit unnecessary stationary operations and reduce power consumption.

The vehicle steering apparatus of the present invention includes a steering member, a vehicle speed detection unit that detects a vehicle speed, a vehicle speed determination unit that determines whether the detected vehicle speed is smaller than a specified value, and a steering reaction force applied to the steering member. The reaction force actuator is controlled based on the reaction force actuator to be applied, the steering drive mechanism that steers the steered wheels, the steering actuator that drives the steering drive mechanism , the vehicle speed, and the steering angle. A reaction force actuator control unit, and a steering actuator control unit that controls the steering actuator based on the vehicle speed and the steering angle. The steering actuator control unit includes a vehicle speed that is lower than the specified value. When it is determined that the speed is small, energization of the steering actuator is limited, and the reaction force actuator control unit determines that the vehicle speed is smaller than the specified value. The reaction force actuator so that the steering reaction force increases as the steering angle of the steering member increases more than the steering reaction force when the vehicle speed is determined to be equal to or higher than the specified value. Is to control .

  The cargo handling vehicle of the present invention is equipped with the vehicle steering device described above.

1 is a schematic side view showing a schematic configuration of a forklift 1. FIG. 2 is a configuration diagram showing the entire vehicle steering device 7. FIG. 3 is a control block diagram on a steering side where reaction force control is performed by a steering side ECU. It is a flowchart for demonstrating the reaction force control procedure by the side of a steering. It is a graph which shows the control map which recorded the reaction force current for steering corresponding to a steering angle. It is a graph which shows the control map which recorded the reaction force electric current for walls corresponding to a steering angle. It is a control block diagram by the side of steering which controls turning angle by turning ECU22. It is a flowchart for demonstrating the steering angle control procedure by the side of a steering.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic side view showing a schematic configuration of a forklift 1 as a cargo handling vehicle of the present invention. The forklift 1 steers a vehicle body 2, a cargo handling device 3 provided at the front of the vehicle body 2, a front wheel 5 as a drive wheel that supports the vehicle body 2, a rear wheel 6 as a steered wheel, and a rear wheel 6. A vehicle steering device 7 is provided.

  The vehicle steering device 7 is a so-called steer-by-wire power steering device in which the mechanical connection between the steering member 10 provided in the cab 22 and the rear wheel 6 that is a steered wheel is broken. In this embodiment, the steering member 10 is a hand-wheeled steering wheel with a knob 10a, and a stationary switch SW is attached to the tip of the knob 10a. The driver holds a knob 10a that is rotatably provided on the steering wheel, and rotates the steering wheel.

  FIG. 2 is a configuration diagram illustrating the entire vehicle steering device 7. The vehicle steering device 7 includes a shaft 11 to which a steering member 10 is coupled, a cylindrical column 12 that rotatably supports the shaft 11, a steering angle sensor 13 that detects a steering angle of the steering member 10, and a steering member. 10 includes a reaction force motor 15 that functions as a reaction force actuator that applies a steering reaction force to the steering wheel 10, and a steering side ECU (electronic control unit) 16 that drives and controls the reaction force motor 15. The steering angle sensor 13 detects the rotation angle of the shaft 11 by detecting a magnetic element attached to the outer periphery of the shaft 11 of the steering member 10 with a hall sensor. In this embodiment, the steering angle sensor 13 detects the rotation angle from the neutral position of the steering member 10 in both forward and reverse directions, and the rotation angle from the neutral position to the right as a positive value. It is assumed that the rotation angle from the neutral position to the left is output as a negative value. The reaction force motor 15 is a column coaxial DC motor that is installed coaxially with the shaft 11 in the column 12 and rotationally drives the shaft 11 at a predetermined gear ratio.

The stationary switch SW attached to the knob 10a of the steering member 10 is a switch that is operated when the driver wants to intentionally perform the stationary operation. A signal indicating the on / off state of the stationary switch SW is input to the steering ECU 16.
Further, the vehicle steering device 7 is moved by the rack shaft 17 that is held on the vehicle body and extends in the left-right direction of the vehicle, the rack support 18 that supports the rack shaft 17 so as to be movable, and the rack shaft 17. A steered motor 19 as a steered actuator, a steered side ECU 22 that drives and controls the steered motor 19, and a steered angle that detects the steered position of the rear wheels 6 (referred to as “steered angle” in this specification). And a sensor 20. The steered motor 19 is, for example, a rack coaxial type DC motor built in the rack support 18. The rotational motion of the steered motor 19 is converted into parallel motion of the rack shaft 17 via the steered gear built in the rack support 18, and tie rods 21 </ b> L connected to a pair of ends of the rack shaft 17, respectively. This is transmitted to the rear wheel 6 via 21R, whereby the rear wheel 6 is steered. Since the turning angle sensor 20 corresponds to the displacement position of the rack shaft 17 and the turning angle of the rear wheel 6, the turning angle of the rear wheel 6 is detected by detecting the displacement position of the rack shaft 17 with a stroke sensor. It is a sensor to detect.

Further, in order to steer the rear wheel 6 according to the operation of the steering member 10, the steering side ECU 16 and the steered side ECU 22 are connected by an in-vehicle LAN.
FIG. 3 is a control block diagram on the steering side controlled by the steering side ECU 16. The target reaction force current turning angle calculation unit B1 of the steering side ECU 16 receives a steering angle signal indicating the detected steering angle from the steering angle sensor 13 and a signal indicating the on / off state of the stationary switch SW. Further, a signal representing the vehicle speed of the forklift 1 is input via the in-vehicle LAN. The signal representing the vehicle speed is obtained by, for example, attaching a magnetic body at equal intervals on the circumference of the wheel of the front wheel 5 or the rear wheel 6, detecting this with a magnetic sensor, and outputting a pulse signal output from the magnetic sensor as a frequency. Obtained by voltage conversion.

The target reaction force current turning angle calculation unit B1 performs a process of calculating a target reaction force current according to the steering angle. Then, as shown in FIG. 3, the current flowing through the reaction force motor 15 is detected, and the difference between the target reaction force current and the current flowing through the reaction force motor 15 is taken, and the reaction force motor 15 is changed based on this difference. PWM drive control is performed.
Hereinafter, the control process performed by the target reaction force current turning angle calculation unit B1 will be described in detail with reference to a flowchart (FIG. 4).

When the steering angle is detected by the steering angle sensor 13 (step S1) and the vehicle speed is detected (step S2), the detected vehicle speed is set to a specified value in order to determine whether the vehicle is stopped or traveling. Compare (step S3). Since this specified value is a value for determining whether the vehicle has stopped, a very small value is adopted. For example, the value is 2 km / h.
If the detected vehicle speed is larger than the specified value (step S3 → Yes), the target reaction force current turning angle calculation unit B1 applies a steering angle-reaction force current map during vehicle travel to apply a steering reaction force. A force current is calculated (step S4). An example of this map is shown in FIG. When the steering angle is 0, the reaction force current is “0”, and is set to increase as the steering angle (absolute value) increases thereafter. As can be seen from FIG. 5, as the steering angle increases, the increase rate of the reaction force current decreases, and the curve converges to a constant value. The reaction force current obtained in this manner is output as the target reaction force current from the target reaction force current turning angle calculation unit B1, and is used for the PWM drive control of the reaction force motor 15 described above (step S6).

  When the detected vehicle speed is greater than the specified value, the target reaction force current turning angle calculation unit B1 calculates the target reaction force current and at the same time, based on the steering angle signal input from the steering angle sensor 13. Thus, a process of calculating a target turning angle corresponding to the steering angle is also performed (step S5). For example, the target reaction force current turning angle calculation unit B1 calculates a target turning angle that is proportional to the steering angle when the detected vehicle speed is larger than a specified value. The target turning angle obtained in this way is output to the turning angle control unit B3 through the in-vehicle LAN. Processing in the turning angle control unit B3 will be described later.

On the other hand, if the detected vehicle speed is smaller than the specified value (step S3 → No), it is determined that the forklift 1 is stopped, and it is determined whether the signal of the stationary switch SW is on or off. (Step S7).
Here, the purpose of the stationary switch SW will be described. The cargo handling vehicle may require a stationary operation for its use. The stationary switch SW is a switch installed for the driver to operate when performing such intentional stationary operation. When this switch is turned on, the driver can operate the steering wheel even when the vehicle is stopped (including when driving at an extremely low speed below the specified value; the same applies hereinafter). However, if the switch is turned off, the driver cannot operate the steering wheel when the vehicle is stopped. For this reason, unnecessary stationary operation can be prevented.

  It is desirable that the stationary switch SW is automatically kept off at the initial time and can be turned on only when operated by the driver. Here, the “initial time point” refers to a time point when the forklift 1 starts before the engine starts, a time point when the forklift 1 that has been stopped stops (a time point when the state was determined to be Yes in step S3 and switched to No). And so on.

Also, if the forklift 1 starts to move with the stationary switch SW turned on (when it is switched to Yes for the first time from the state determined as No in step S3), the stationary switch SW is automatically switched off and switched. After that, it is desirable to maintain the off state.
If it is determined in step S7 that the signal of the stationary switch SW is in the on state, the driver can confirm that he wants to stationary the steering wheel even when the vehicle is stopped. Do the same process.

If it is determined in step S7 that the signal of the stationary switch SW is in the OFF state, the process proceeds to step S8 and proceeds to the wall reaction force current calculation process (step S8).
In the wall reaction force current calculation process, a wall reaction force current is calculated by applying a steering angle-wall reaction force current map when the vehicle is stopped. The wall reaction force current thus obtained is output as a target reaction force current from the target reaction force current turning angle calculation unit B1, and the reaction force motor 15 is PWM-driven based on the target reaction force current. The

  A specific example of the wall reaction force current map is shown in FIG. When the steering angle is 0, the wall reaction force current is “0”, but is set so as to increase rapidly as the steering angle (absolute value) increases thereafter. As can be seen from FIG. 6, the wall reaction force current increases rapidly, and then the wall reaction force current saturates and maintains its saturation value even when the steering angle is increased. . In this way, when the steering member 10 is started to rotate, a steep slope is provided in the reaction force torque, and a “wall feeling” is generated in the steering. Know that steering is very difficult.

  The target reaction force current turning angle calculation unit B1 outputs a command signal indicating that the target turning angle is not changed to the turning angle control unit B3 after the wall reaction force current calculation process (step S8). (Step S9). The processing in step S9 is different from the processing in step S5 described above (processing for calculating a target turning angle substantially proportional to the steering angle based on the steering angle signal input from the steering angle sensor 13). This is to fix the rudder angle at the current value.

Next, processing on the steered side controlled by the steered side ECU 22 will be described. FIG. 7 is a control block diagram on the steered side. A signal representing the vehicle speed of the forklift 1 is supplied to the steered side ECU 22, and an on / off signal of the stationary switch SW is supplied. Further, the target turning angle calculated by the target reaction force current turning angle calculation unit B1 is supplied.
The vehicle speed signal and the on / off signal of the stationary switch SW are input to the current limit value calculation unit B2 of the turning side ECU 22, and the target turning angle is input to the turning angle control unit B3. The turning angle control unit B3 performs a process of calculating a target current for turning the rear wheel 6. In this target current calculation process, the difference between the target turning angle input to the turning angle control unit B3 and the detected turning angle detected by the turning angle sensor 20 is taken, and the turning motor is based on this difference. A target current to be supplied to 19 is calculated. On the other hand, the current flowing through the steered motor 19 is detected, and the difference between the aforementioned target current and the current flowing through the steered motor 19 is taken, and the steered motor 19 is PWM driven based on this difference. As described above, the rotation of the steering motor 19 is converted into a parallel motion of the rack shaft 17 via the steering gear and is connected to the pair of end portions of the rack shaft 17 via tie rods 17L and 17R. This is transmitted to the rear wheel 6, thereby turning the rear wheel 6.

  FIG. 8 shows a flowchart for explaining the control of the current limit value calculation unit B2. First, the current limit value calculation unit B2 detects the vehicle speed (step T1), and compares the detected vehicle speed with a specified value to determine whether the vehicle is stopped or traveling (step T2). Since this specified value is a value for determining stop of the vehicle, a very small value is adopted (similar to the specified value in step S3 in FIG. 4).

When the detected vehicle speed is higher than the specified value (step T2 → Yes), the current limit value calculation unit B2 sets the current limit value to a value “steering current max during travel” in order to limit the target current. And it passes to turning angle control part B3.
As described above, the turning angle control unit B3 inputs the turning angle detected by the turning angle sensor 20, takes the difference between the target turning angle and the detected turning angle, and based on this difference, the target current In this target current calculation, the target current is limited so as not to exceed the current limit value input from the current limit value calculation unit B2. This is to protect the steered motor 19 by suppressing an excessive increase in the current flowing through the steered motor.

As a result of comparing the detected vehicle speed with the specified value in step T2, if the vehicle speed is lower than the specified value (step T2 → No), the on / off state of the stationary switch SW is checked (step T4).
If it is determined in step T4 that the signal of the stationary switch SW is in the ON state, the driver can confirm that he wants to stationary the steering wheel even when the vehicle is stopped. Do the same process.

If it is determined in step T4 that the signal of the stationary switch SW is in the OFF state, the process proceeds to step T5, and the current limit value calculation unit B2 sets the current limit value “ A value smaller than the “steering current max” is set and passed to the turning angle control unit B3. The “value smaller than the steering current max during travel” may be “0”, for example.
The turning angle control unit B3 calculates the target current based on the difference between the target turning angle and the detected turning angle, and the current limit is input from the current limit value calculation unit B2. Since the value is limited, the current flowing through the steering motor 19 is limited, and the steering is performed at a very low speed. If the current limit value is “0”, no current flows through the steered motor 19. That is, the vehicle cannot be steered.

  As described above, according to the embodiment of the present invention, the driver of the forklift 1 can turn the forklift 1 as usual by turning the steering member 10 during traveling of the vehicle. However, when the vehicle is stopped, the forklift 1 cannot be steered. Further, since a large wall reaction force is felt even when the steering member 10 is rotated, the driver can know that the forklift 1 cannot be steered.

If the driver wants to steer intentionally when the vehicle is stopped, turning on the stationary switch SW eliminates the wall reaction force and enables the steering.
Accordingly, it is possible to suppress wasteful power consumption in a cargo handling vehicle such as the forklift 1 and delay battery consumption.
Although the embodiment of the present invention has been described above, the implementation of the present invention is not limited to the above-described embodiment. For example, instead of the configuration in which the rear wheels 6 are provided on the left and right sides of the vehicle body 2 as steered wheels, a single rear wheel 6 may be provided at the center in the left-right direction of the vehicle body 2. In the above-described embodiment, the rack shaft 17 driven by the steering motor 19 is employed as the steering drive mechanism. However, a hydraulic cylinder driven by an electric hydraulic pump may be employed. In addition, various modifications can be made within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Forklift (cargo handling vehicle), 2 ... Vehicle body, 3 ... Cargo handling device, 5 ... Front wheel (drive wheel), 6 ... Rear wheel (steered wheel), 7 ... Steering device for vehicles, 10 ... Steering member, 13 ... Steering angle Sensor, 15 ... Reaction force motor, 16 ... Steering side ECU, 17 ... Rack shaft, 19 ... Steering motor, 20 ... Steering angle sensor, 22 ... Steering ECU, SW ... Stationary switch

Claims (8)

A steering member, a vehicle speed detection unit that detects a vehicle speed, a vehicle speed determination unit that determines whether the detected vehicle speed is smaller than a specified value,
A reaction force actuator for applying a steering reaction force to the steering member, a turning drive mechanism for turning steered wheels, a turning actuator for driving the turning drive mechanism ,
A reaction force actuator control unit for controlling the reaction force actuator based on the vehicle speed and the steering angle;
A steering actuator controller that controls the steering actuator based on the vehicle speed and the steering angle;
The steering actuator control unit is configured to limit energization to the steering actuator when it is determined that the vehicle speed is smaller than the specified value.
When the reaction force actuator control unit determines that the vehicle speed is smaller than the specified value, the steering reaction force is increased as the steering angle of the steering member increases, and the vehicle speed is equal to or higher than the specified value. A vehicle steering apparatus that controls the reaction force actuator so as to be larger than the steering reaction force when it is determined . The reaction force actuator control unit controls the reaction force actuator based on a relationship of a reaction force current of the reaction force actuator with respect to the steering angle, and the relationship when the vehicle speed is determined to be equal to or more than the specified value is: The reaction force current is 0 when the steering angle is 0, and the reaction force current increases and converges to a constant value as the steering angle increases while the rate of increase decreases. Vehicle steering system. The relationship of the reaction force current with respect to the steering angle when the vehicle speed is smaller than the specified value is that the reaction force current is 0 when the steering angle is 0, and the rate of increase is greater as the steering angle increases. The vehicle steering apparatus according to claim 2, which increases at a large increase rate. The relationship of the reaction force current with respect to the steering angle when the vehicle speed is smaller than the specified value is that the reaction force current is 0 when the steering angle is 0, and the rate of increase is greater as the steering angle increases. The vehicle steering apparatus according to claim 2, wherein the vehicle is increased to a saturation value at a large increase rate, and the saturation value is maintained regardless of the steering angle after the saturation value is reached. Further equipped with a stationary switch installed at a position where the driver can operate,
The reaction force actuator control unit, it is determined that the detected vehicle speed is less than the prescribed value, and when the stationary steering switch is turned ON, suddenly the steering reaction force to the reaction force actuator control unit to cancel the increase makes control,
The turning actuator control unit, it is determined that the detected vehicle speed is less than the prescribed value, and when the stationary steering switch is turned ON, releasing the limitation of the current supply to the steering actuator control unit claim 1 Symbol placement of a vehicle steering system. 6. The vehicle steering apparatus according to claim 1, wherein the steering member is a steer-by-wire type in which mechanical connection between the steering member and the steered drive mechanism is broken. The vehicle steering apparatus according to any one of claims 1 to 6 , which is applied to a cargo handling vehicle. A cargo handling vehicle equipped with the vehicle steering device according to claim 7 .

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