JP5392550B2 - Vehicle steering system - Google Patents

Description

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

  The forklift that can select the driving mode by the mode selection switch has means for storing the limit turning angle of the steered wheels in the selected running mode, and the actual turning angle of the steered wheels exceeds the limit turning angle range. A traveling mode selection device has been proposed in which the actual steering angle is displayed on the steering instruction section so that the actual steering angle falls within the range of the limit steering angle (see, for example, Patent Document 1).

  Usually, in a cargo handling vehicle, the turning angle is set larger than the steering angle for the purpose of placing importance on the small turning performance.

Japanese Utility Model Publication No. 6-69065 (Claim 1, FIG. 3)

Therefore, when the vehicle is stopped in a state where a large turning angle is steered due to a stationary stop or the like, the running resistance when starting next increases. For this reason, a fuel consumption worsens and it is unpreferable on energy saving. In addition, the load on a support member such as a kingpin that supports the steered wheels is increased, and durability is reduced.
The present invention has been made in view of the above problems, and an object thereof is to provide a vehicle steering apparatus that can contribute to energy saving and has excellent durability.

In order to achieve the above object, the present invention provides a steering angle (θ _H ) of a steering member (10) in a vehicle steering device (9) for steering a cargo handling vehicle (1) provided with a cargo handling device (3). Steering angle detection means (14) for detecting the vehicle speed, vehicle speed detection means (49) for detecting the vehicle speed (V) of the cargo handling vehicle, a steering actuator (12) for turning the steered wheels (6), a target Control means (11) for controlling the turning actuator based on the turning angle (θ _W ^* ), wherein the control means has a vehicle speed detected by the vehicle speed detecting means less than a predetermined vehicle speed value (V ₀ ). When the absolute value (| θ _H |) of the steering angle detected by the steering angle detection means is equal to or greater than a predetermined steering angle value (θ _H0 ), the target turning angle is detected by the steering angle detection means. and a value between the normal value corresponding to the steering angle and (theta _WA ^* or - [theta] _WA ^*) to zero One predetermined limit value corresponding to the value of the corresponding target steering angle to the predetermined steering angle value is limited to (theta _W0 ^* or - [theta] _W0 ^*), the target turning angle is limited to the predetermined limit value When the detected vehicle speed exceeds the predetermined vehicle speed value, the target turning angle is gradually changed from the predetermined limit value to the normal value so that the driver can manually operate the operation switch. The control means has a function of changing at least one of the predetermined vehicle speed value and the predetermined steering angle value in response to the operation switch being operated. .

  In the present invention, for example, when a large steering is performed while the vehicle is stopped or traveling at a low speed, the target turning angle is limited to a predetermined limit value between the normal value and zero. The value will not be too large. Therefore, when starting from the next stop or when increasing the traveling speed from a very low speed, there is no case where the absolute value of the turning angle is excessively large, so that the traveling resistance can be reduced and saved. Can contribute to energy. That is, the fuel efficiency is improved, and the travelable distance with one refueling can be extended. Moreover, the load of the member which supports a steered wheel can be made small, and durability improves.

  In addition, if the vehicle speed condition for restriction is canceled during the limit setting of the target turning angle, if the target turning angle is immediately returned from the predetermined limit value to the normal value without restriction, Then, the actual change of the turning angle becomes sudden, and the driver's steering feeling may be deteriorated. On the other hand, in the present invention, since the target turning angle is gradually returned from the predetermined limit value to the normal value that is not restricted, the actual turning angle is also gradually changed. A good steering feeling can be given to the driver.

In addition, an operation switch (57) that can be manually operated by the driver is provided, and the control means is configured to control at least one of the predetermined vehicle speed value and the predetermined steering angle value in response to the operation switch being operated. Since it has a function of changing , there are the following advantages. That is , by changing at least one of the predetermined vehicle speed value and the predetermined steering angle value by the driver's operation, control according to the driving mode selected by the driver is possible. For example, when the predetermined vehicle speed value is changed to be increased or the predetermined steering angle value is changed to be decreased, it is preferable in that the energy saving effect can be improved.

Further, the control means may decrease the predetermined steering angle value when detecting or estimating acceleration of the cargo handling vehicle (claim 2 ). In the acceleration state, running resistance tends to increase even at the same turning angle. Therefore, when the acceleration of the cargo handling vehicle is detected or estimated, the predetermined steering angle value is decreased. Thereby, the steering angle range as a condition for limiting the target turning angle to a predetermined limit value can be further expanded, and as a result, it can further contribute to energy saving.

  In the above description, the alphanumeric characters in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

1 is a schematic side view showing a schematic configuration of a forklift as a cargo handling vehicle including a vehicle steering apparatus according to an embodiment of the present invention. It is the schematic for demonstrating the principle of operation which raises / lowers a fork. It is a block diagram which shows the electric constitution of a forklift. It is a flowchart which shows the flow of the main control by ECU. It is a graph which shows the steering angle-target turning angle map used as a control map. It is a block diagram which shows the electric constitution of a forklift in another embodiment of this invention. It is a flowchart which shows the flow of the main control of ECU in embodiment of FIG.

A preferred embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic side view showing a schematic configuration of a forklift as a cargo handling vehicle according to an embodiment of the present invention. Referring to FIG. 1, a forklift 1 includes a vehicle body 2, a cargo handling device 3 provided at a front portion of the vehicle body 2, a counterweight 4 provided at a rear portion of the vehicle body 2, and a driving wheel that supports the vehicle body 2. As a front wheel 5 and a rear wheel 6 as a steered wheel, a vehicle drive source 7 including, for example, an engine, a hydraulic pump 8 as a hydraulic source, and a vehicle steering device 9 for steering the rear wheel 6 I have.

The vehicle steering device 9 is configured as a so-called steer-by-wire vehicle steering device in which the mechanical connection between the steering member 10 that is a handwheel with a knob and the rear wheel 6 that is a steered wheel is broken. ing. As a steered wheel, a single rear wheel 6 may be provided at the center in the left-right direction of the vehicle body 2, or the rear wheels 6 may be provided on the left and right sides of the vehicle body 2, respectively.
The vehicle steering device 9 includes the steering member 10 and, for example, an electric motor for turning the rear wheel 6 as a steered wheel in accordance with an operation of the steering member 10, and an ECU 11 (electronic control unit) as control means. A steering actuator 12 that is driven and controlled by the ECU 11, and a reaction force actuator 13 that is driven by the ECU 11. Further, the vehicle steering device 9 includes a steering angle sensor 14 that detects the steering angle of the steering member 10 and a turning angle sensor 15 that detects the turning angle of the rear wheel 6.

The rear wheel 6 as a steered wheel is rotatably supported by a substantially vertical support member 16. The support member 16 is supported through a bearing 17 held by the vehicle body 2 so as to be rotatable about a substantially vertical rotation axis C1.
The rotation of the output shaft of the steering actuator 12 is decelerated via the transmission mechanism 18 and transmitted to the support member 16. The transmission mechanism 18 is provided such that a drive member 19 made of, for example, a drive gear that rotates along with the output shaft of the steering actuator 12, and a support member 16 around the rotation axis C1 so that the support member 16 can rotate along with the drive gear. It has a driven member 20 made of, for example, a driven gear. The transmission mechanism 18 and the turning actuator 12 constitute a turning mechanism A1.

Although not shown, the power of the drive source 7 such as an engine is transmitted to a transmission that performs forward / reverse switching and a shift operation via a torque converter, and further transmitted to left and right front wheels 5 (drive wheels) via a differential. It has become so. The transmission includes a forward clutch and a reverse clutch.
The forklift 1 includes a cab 22 including a driver seat 21. The cab 22 is formed on the vehicle body 2 so as to be surrounded by the frame 23.

  The cargo handling device 3 is lifted and lowered by a pair of left and right outer masts 24 supported by the vehicle body 2 so as to be tiltable about the lower end 24 a, an inner mast 25 supported by the outer mast 24 so as to be lifted and lowered, and the outer mast 24. The lift bracket 26 is supported so as to be supported, and a pair of left and right forks 27 that are attached to the lift bracket 26 and serve as a loading portion for loading a load.

  A tilt cylinder 28 is interposed between a predetermined portion of the outer mast 24 and a predetermined portion of the vehicle body 2. The tilt cylinder 28 includes a cylinder body 29 having one end that is swingably connected to a predetermined portion of the vehicle body 2, and a rod 30 that protrudes from the other end of the cylinder body 29. The tip of the rod 30 is slidably connected to a predetermined portion of the outer mast 24. As the rod 30 of the tilt cylinder 28 extends and contracts, the outer mast 24 is displaced into an upright posture and a tilted posture.

  A lift cylinder 31 is provided for moving the inner mast 25 up and down using the outer mast 24 as a guide. The lift cylinder 31 has a cylinder body 32 fixed to the outer mast 24 and a rod 33 protruding from the cylinder body 32. The tip of the rod 33 is fixed to a mounting portion 25 a provided at a predetermined portion of the inner mast 25.

A load sensor 34 as load detecting means for detecting the load of the cargo handling device 3 is attached to the lower part of the cylinder body 32 of the lift cylinder 31. A signal from the load sensor 34 is input to the ECU 11.
In the front part of the cab 22, an operation stand 35 is provided on the bottom surface 22 a of the cab 22, and the driver seat 21 is fixed to the rear part of the cab 22.

  The operation stand 35 includes the operation member 10, a lift operation lever 36 for lifting and lowering the fork 27, and a tilt for swinging the outer mast 24 as a plurality of operation elements for the driver to operate manually. An operation lever 37, a forward / reverse switching lever 38, and an eco driving mode selection switch 57 for selecting an eco driving mode in which the driver saves fuel consumption are provided. In addition, a confirmation mirror 39 for mainly confirming the rear side is fixed to the operation stand 35. The operation stand 35 is provided with various switches not shown.

  In the vicinity of the base of the operation stand 35, an accelerator pedal 40, a brake pedal 41, and a clutch pedal 42 are provided on the bottom surface 22a of the cab 22 as a plurality of operation elements for the driver to operate with his / her feet. Yes. Although the accelerator pedal 40, the brake pedal 41, and the clutch pedal 42 are actually arranged side by side in a direction perpendicular to the paper surface (corresponding to the left-right direction of the vehicle), they are schematically shown in FIG. In FIG. 1, the layout of the lifting / lowering operation lever 36, the tilt operation lever 37, and the forward / reverse switching lever 38 as operation elements is also schematically shown.

  Referring to FIG. 2 that conceptually shows the principle of the operation of raising and lowering the fork 27, a sprocket 43 is rotatably supported on the upper portion of the inner mast 25, and a chain 44 is wound around the sprocket 43. It has been. One end 44 a of the chain 44 is fixed to a fixing portion 24 b provided on the outer mast 24, and the other end 44 b of the chain 44 is fixed to the lift bracket 26. Thereby, the lift bracket 26 and the fork 27 are suspended using the chain 44.

  When the inner mast 25 rises with the extension of the rod 33 of the lift cylinder 31, the sprocket 43 rises with respect to the fixing portion 24 b of the outer mast 24, and the lift bracket 26 and the fork as the loading portion are connected via the chain 44. 27 is raised. The amount by which the fork 27 rises with respect to the ground surface 48 is twice the amount by which the rod 33 of the lift cylinder 31 extends.

A stroke sensor 45 as a loading portion height detecting means for detecting the height of the fork 27 as the loading portion is provided, and a signal from the stroke sensor 45 is input to the ECU 11. A rotary encoder may be used as the stroke sensor 45.
Specifically, a wire 46 having one end locked to the other end 44 b of the chain 44 is wound around a wire drum 47 rotatably supported by the outer mast 24, and the other end of the chain 44 together with the fork 27. When 44b moves up and down, the wire 46 is unwound from the wire drum 47 or unwound. At this time, the ECU 11 detects the number of rotations of the wire drum 47 with a rotary encoder as the stroke sensor 45, calculates the unwinding amount of the wire 46 from the wire drum 47 based on the detected value, and based on the calculated value. Thus, the loading portion height H, which is the height of the fork 27 from the ground surface 48, is detected.

FIG. 3 is a block diagram showing the main electrical configuration of the forklift 1. Referring to FIG. 3, the ECU 11 includes a steering angle sensor 14 for detecting the steering angle θ _H of the steering member 10, and a turning angle for detecting the turning angle θ _W of the rear wheel 6 as a turning wheel. Sensor 15, vehicle speed sensor 49 for detecting vehicle speed V, load sensor 34 as load detecting means for detecting load load W of fork 27 serving as a loading unit, and loading that is the height of fork 27 serving as a loading unit A stroke sensor 45 serving as a loading section height detecting means for detecting the section height H, a lifting operation lever position sensor 50 for detecting the position of the lifting operation lever 36, and a position for detecting the position of the tilt operation lever 37 Receiving from each of the tilt operation lever position sensor 51, the forward / reverse switching switch 52 that operates in accordance with the switching of the forward / reverse switching lever 38, and the eco-operation mode selection switch 57. There are input.

  Further, the ECU 11 controls the steering actuator 12, the reaction force actuator 13, the lift control valve 53 including an electromagnetic proportional control valve that controls the supply of hydraulic oil from the hydraulic pump 8 to the lift cylinder 31, and the tilt from the hydraulic pump 8. A tilt control valve 54 comprising an electromagnetic proportional control valve for controlling the supply of hydraulic oil to the cylinder 28, and an electromagnetic proportional control valve for controlling the supply of hydraulic oil to the hydraulic cylinder for engaging / disengaging the forward clutch. A signal is output to each of the forward clutch control valve 55 and the reverse clutch control valve 56 including an electromagnetic proportional control valve for controlling the supply of hydraulic oil to the hydraulic cylinder for engaging / disengaging the reverse clutch. It has become so.

The ECU 11 performs various controls. For example, the ECU 11 is input from the steering angle and vehicle speed sensor 49 input from the steering angle sensor 14 in order to cause the reaction force actuator 13 to generate torque for applying a steering reaction force according to the road surface reaction force to the steering member 10. The reaction force actuator 13 is driven and controlled based on the vehicle speed (that is, reaction force control is performed).
Further, the ECU 11 sends a control signal to the lift control valve 53 that controls the supply of hydraulic oil from the hydraulic pump 8 to the lift cylinder 31 according to the position of the lift operation lever 36 input from the lift control lever position sensor 50. Output.

Further, the ECU 11 sends a control signal to the tilt control valve 54 that controls the supply of hydraulic oil from the hydraulic pump 8 to the tilt cylinder 28 according to the position of the tilt operation lever 37 input from the tilt operation lever position sensor 51. Output.
Further, the ECU 11 outputs a control signal to the forward clutch control valve 55 in response to the forward / backward changeover switch 52 being switched to forward, and the hydraulic pump for operating the forward clutch is operated from the hydraulic pump 8. Allow oil to be supplied.

Further, the ECU 11 outputs a control signal to the reverse clutch control valve 56 in response to the forward / reverse changeover switch 52 being switched to the reverse direction, and the hydraulic cylinder for operating the reverse clutch is operated from the hydraulic pump 8. Allow oil to be supplied.
FIG. 4 is a flowchart showing the main operation of the ECU 11. Referring to FIG. 4, ECU 11 first determines in step S <b> 1 whether or not the eco-operation mode is selected based on a signal from eco-operation mode selection switch 57.

In the case (YES in step S1) eco operation mode is selected, at step S2, by adding a predetermined value A (> 0) to a predetermined vehicle speed value V _0, the predetermined vehicle speed value V ₀ The increase is corrected, and the predetermined steering angle value θ _H0 is subtracted from the predetermined steering angle value θ _H0 to decrease the predetermined steering angle value θ _H0 . In step S2, only one of the predetermined vehicle speed value V ₀ and the predetermined steering angle value θ _H0 may be corrected.

In step S 3, the vehicle speed V is read based on the signal from the vehicle speed sensor 49 and the steering angle θ _H is read based on the signal from the steering angle sensor 14.
Next, in step S4, it is determined whether or not the vehicle speed V is less than a predetermined vehicle speed value V ₀ (V ₀ is, for example, 5 km / h). That is, it is determined whether the vehicle is stopped (V = 0) or is traveling at a slow speed (0 <V <V ₀ ).

If the vehicle speed V is less than the predetermined vehicle speed value V ₀ (V <V ₀ ) (YES in step S4), the absolute value | θ _H | of the steering angle θ _H is set to a predetermined value in step S5. It is determined whether or not the steering angle value is θ _H0 (for example, 680 °) or more (| θ _H | ≧ θ _H0 ). That is, the steering angle θ _H is equal to or greater than a predetermined steering angle value θ _H0 (for example, 680 °) (θ _H ≧ θ _H0 ), and the steering angle θ _H is a predetermined steering angle value −θ _H0 (for example, −680 °). It is determined whether one of the following conditions is satisfied (θ _H ≦ −θ _H0 ).

In step S5, the absolute value of the steering angle theta _H | proceeds to step S6 when it is determined that _{(≧ θ H0 | | θ H} ) | θ H is a predetermined steering angle value theta _H0 more. In step S6, the target turning angle θ _W ^* is limited to a predetermined limit value θ _W0 ^* (or −θ _W0 ^* ) between the normal value θ _WA ^* (or −θ _WA ^* ) and zero. . The normal value θ _WA ^* (or −θ _WA ^* ) corresponds to the value of the target turning angle θ _W ^* corresponding to the steering angle θ _H at that time on the normal map (indicated by a broken line in FIG. 5). .

Specifically, as shown in FIG. 5, if the steering angle θ _H is equal to or _larger than a predetermined steering angle value θ _H0 (θ _H ≧ θ _H0 ), the target turning angle θ _W ^* is set to a predetermined limit value θ _W0. ^* limitation set to ^{_{(θ W * ← θ W0 *}} ). If the steering angle θ _H is equal to or less than a predetermined steering angle value −θ _H0 (θ _H ≦ −θ _H0 ), the target turning angle θ _W ^* is limited to a predetermined limit value −θ _W0 ^* [θ _W ^* ← (−θ _W0 ^* )]. Thereafter, the process proceeds to step S8.

In step S8, it is determined whether or not the vehicle speed V is equal to or higher than a predetermined vehicle speed value V ₀ when the target turning angle θ _W ^* is set to be limited. When the target turning angle θ _W ^* is set to be limited, the forklift 1 accelerates and the vehicle speed V becomes equal to or higher than the predetermined vehicle speed value V ₀ (in the case of YES in step S8, the target turning) When the condition for restricting the angle θ _W ^* is canceled), in step S9, as shown in FIG. 5, the target turning angle θ _W ^* is restricted, for example, from a predetermined limit value θ _W0 ^*. A gradual change (gradual increase) to a normal value θ _WA ^* not present, or a gradual change (gradual decrease) from a predetermined limit value −θ _W0 ^* to an unrestricted normal value −θ _WA ^* . Next, the process proceeds to step S10.

If the target turning angle θ _W ^* is set to be limited and the vehicle speed V is less than the predetermined vehicle speed value V ₀ (NO in step S8), the process proceeds to step S10 without passing through step S9. .
In step S5, the absolute value of the steering angle θ _H | θ _H | is less than the predetermined steering angle value theta _H0 when it is (| | θ _H <θ _{H0 i.e., -θ H0 <θ H <θ} H0) ( step S5 If NO in step S7), the process proceeds to step S7. In step S7, the target turning angle θ _W ^* is normally set based on the steering angle θ _H. Specifically, the target turning angle θ _W ^* is set using the formula θ _W ^* = k · θ _H as the coefficient k (corresponding to the slope of the map in FIG. 5). In Figure 5, the steering angle theta target turning angle _H theta _W ^* showed be proportional, the target steered angle theta _W ^* may be any one which is represented by a function equation of the steering angle theta _H. Then, it progresses to step S10.

In step S10, the turning angle θ _W actual turning angle) is read based on the signal from the turning angle sensor 15, and then in step S11, the turning angle θ _W (actual turning angle) is set to the target turning angle. The steering actuator 12 is driven and controlled so as to approach the steering angle θ _W ^* (that is, steering control is performed).
According to the present embodiment, for example, when steering is performed with a large steering angle θ _H when the vehicle is stopped (V = 0) or at a slow speed (V <V ₀ ), the target turning angle θ _W ^* is limited. Since it is limited to a predetermined limit value θ _W0 ^* (or −θ _W0 ^* ) between the normal value θ _WA ^* (or −θ _WA ^* ) that has not been received and zero, the actual turning angle θ _W The absolute value does not become excessively large. Therefore, when the vehicle is started from the next stop or when the traveling speed is increased from a very low speed, the vehicle does not travel with the absolute value of the turning angle θ _W being excessively large. As a result, the running resistance at the time of starting can be reduced, which can contribute to energy saving. That is, the fuel efficiency is improved, and the travelable distance with one refueling can be extended. Further, the load on the support member 16 that supports the rear wheel 6 as the steered wheel can be reduced, and the durability is improved.

Further, when the target turning angle θ _W ^* is set to be limited, the target turning is performed in step S9 on condition that the vehicle speed V becomes equal to or higher than the predetermined vehicle speed value V ₀ (in the case of YES in step S8). The angle θ _W ^* is gradually increased (or gradually decreased) from a predetermined limit value θ _W0 ^* (or −θ _W0 ^* ) to a normal value θ _WA ^* (or −θ _WA ^* ) that is not limited. This is a case where the vehicle speed condition (V <V ₀ ) for restriction is released when the actual turning angle θ _W is substantially restricted by the restriction setting of the target turning angle θ _W ^*. I am considering.

That is, in the target steering angle theta _W ^* limits set, when the vehicle speed condition for restriction is canceled, if the target turning angle theta _W ^* set limits theta _W0 ^* (or - [theta] _W0 ^* ) To immediately return to an unrestricted normal value θ _WA ^* (or −θ _WA ^* ), the actual turning angle θ _W changes suddenly and the driver's steering feeling becomes worse. There is a fear. On the other hand, in the present embodiment, the target turning angle θ _W ^* is changed from the predetermined limit value θ _W0 ^* (or −θ _W0 ^* ) to the normal value θ _WA ^* (or −θ _WA that is not limited). ^*) until, since the back gradually, as a result of actual steered angle theta _W is also changed gradually, it is possible to provide a good steering feeling to the driver.

Moreover, increased by the eco operation mode selection switch 57, when the eco operation mode is selected, as shown in step S2, by adding a predetermined value A to a predetermined vehicle speed value V _0, the predetermined vehicle speed value V ₀ The predetermined steering angle value θ _H0 is subtracted from the predetermined steering angle value θ _H0 to reduce the predetermined steering angle value θ _H0 . By this, the spread range and scope of the steering angle theta _H of the vehicle speed V for limiting sets the target steering angle theta _W ^*. As a result, the energy saving effect can be further improved.

Further, since the vehicle steering device 9 is configured as a so-called steer-by-wire vehicle steering device in which the mechanical connection between the steering member 10 and the rear wheel 6 as the steered wheel is cut off, the steering actuator The 12 turning control is preferable because the turning angle θ _W can be easily changed regardless of the steering angle θ _H.
6 and 7 show another embodiment of the present invention. Referring to FIG. 6, the present embodiment is different from the embodiment of FIG. 3 in that an accelerator sensor 58 for detecting the accelerator opening is provided as vehicle acceleration estimating means for estimating the acceleration of the vehicle. . A signal from the accelerator sensor 58 is input to the ECU 11, and the ECU 11 estimates the acceleration of the vehicle based on the signal from the accelerator sensor 58. In other words, the ECU 11 detects the intention of acceleration by the driver based on the signal from the accelerator sensor 58. As the accelerator sensor 58, a stroke sensor that detects the depression stroke amount of the accelerator pedal 40 can be used.

Further, in the present embodiment, the ECU 11 detects the vehicle acceleration V ′ by differentiating the vehicle speed value detected based on the signal from the vehicle speed sensor 49 with respect to time.
Referring to FIG. 7, the present embodiment is different from the embodiment of FIG. 5 in that steps S31 to S33 are added between steps S3 and S4. That is, in step S31, it is determined whether or not the vehicle acceleration V ′ obtained by time differentiation of the vehicle speed value obtained by the vehicle speed sensor 49 is positive. That is, when the vehicle acceleration is positive (V ′> 0), it is determined that the vehicle is in an acceleration state.

If it is determined in step S31 that the vehicle is not in an accelerated state (V ′ ≦ 0) (NO in step S31), the process proceeds to step S32, where the accelerator opening P detected by the accelerator sensor 58 is a predetermined value. It is determined whether or not the accelerator opening value P ₀ is equal to or greater than (P ≧ P ₀ ).
When it is determined that the vehicle acceleration is positive (V ′> 0) (YES in step S31), and accelerator opening P is equal to or greater than a predetermined accelerator opening value P ₀ (P ≧ P ₀ ). Is determined (YES in step S32), the process proceeds to step S33.

In the step S33, by subtracting a predetermined value C from a predetermined steering angle value theta _H0, after corrected by decreasing the predetermined steering angle value theta _H0, the process proceeds to step S4.
In step S32, if the accelerator opening P is less than the predetermined accelerator opening value P ₀ (P <P ₀ ) (NO in step S32), the process skips step S33 and proceeds to step S4. To do.

According to the present embodiment, the same operational effects as those of the embodiment of FIGS. Furthermore, there are the following advantages. That is, in the acceleration state, the running resistance tends to increase even at the same turning angle θ _W. Therefore, when acceleration of the forklift 1 is detected (V ′> 0) or the accelerator opening P is equal to or greater than a predetermined accelerator opening value P ₀ (P ≧ P ₀ ), the intention of acceleration is detected (acceleration when but estimated) subtracts the predetermined value C (> 0) from the predetermined steering angle value theta _H0, it decreased corrected so as to approach the predetermined steering angle value theta _H0 to zero. As a result, the steering angle range as a condition for limiting the target turning angle θ _W ^* to the predetermined limit value θ _W0 ^* (or −θ _W0 ^* ) can be further expanded, resulting in energy saving. It can contribute even more.

In each of the above embodiments, the eco-operation mode selection switch 57 can be abolished, and step S1 and step S2 can be abolished.
Further, in the embodiment of FIGS. 6 and 7, either one of step S31 and step S32 may be omitted. When step S32 is abolished, the accelerator sensor 58 is abolished. In addition, various modifications can be made within the scope of the claims of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Forklift (cargo handling vehicle), 2 ... Vehicle body, 3 ... Cargo handling device, 6 ... Rear wheel (steered wheel), 9 ... Vehicle steering device, 10 ... Steering member, 11 ... ECU (control means), 12 ... Steering Actuator, 14 ... Steering angle sensor (steering angle detection means), 49 ... Vehicle speed sensor (vehicle speed detection means), 57 ... Eco-operation mode selection switch (operation switch), 58 ... Accelerator sensor (vehicle acceleration estimation means), θ _H ... Steering angle, | θ _H | ... Absolute value of steering angle, θ _H0 ... Predetermined steering angle value, V ... Vehicle speed, V ₀ ... Predetermined vehicle speed value, θ _W ... Steering angle, θ _W ^* ... Target turning angle , Θ _W0 ^* , −θ _W0 ^* … predetermined limit value, θ _WA ^* , −θ _WA ^* … normal value

Claims (2)

In a vehicle steering device for steering a cargo handling vehicle equipped with a cargo handling device,
Steering angle detection means for detecting the steering angle of the steering member;
Vehicle speed detecting means for detecting the vehicle speed of the cargo handling vehicle;
A steering actuator for steering the steered wheels;
Control means for controlling the turning actuator based on the target turning angle,
The control means has the target turning angle when the vehicle speed detected by the vehicle speed detection means is less than a predetermined vehicle speed value and the absolute value of the steering angle detected by the steering angle detection means is equal to or greater than a predetermined steering angle value. Is a predetermined limit value that is a value between a normal value corresponding to the steering angle detected by the steering angle detection means and zero and corresponds to a target turning angle value corresponding to the predetermined steering angle value. When the vehicle speed detected when the target turning angle is limited to the predetermined limit value is equal to or higher than the predetermined vehicle speed value, the target turning angle is changed from the predetermined limit value to the above Gradually change to normal value ,
It is further equipped with an operation switch that can be operated manually by the driver,
The vehicle steering apparatus , wherein the control means has a function of changing at least one of the predetermined vehicle speed value and the predetermined steering angle value in response to an operation of the operation switch . 2. The vehicle steering apparatus according to claim 1, wherein the control means brings the predetermined steering angle value close to zero when the acceleration of the cargo handling vehicle is detected or estimated.

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