DE10133228A1 - Driving control device of industrial vehicle e.g. fork lift truck, reduces driving torque with respect to driving wheel, if torque reduction control approval condition is judged - Google Patents

Abstract

A CPU (32) judges the slip condition, if the sliding velocity of the driving wheel (15), exceeds a threshold value. The CPU sets up the torque reduction control approval and disapproval conditions, and controls the motor (22) to reduce the driving torque or retarding torque with respect to the wheel, if approval condition is judged.

Description

The present invention relates to a Drive control device for electric company vehicles such as for example a reach truck.

A conventional reach truck has a couple forward extending thrust legs. A pair of front wheels, the trailing wheels are supported by the thrust legs. On Rear wheel and a caster are on the rear Bottom portion of the vehicle body arranged. The rear wheel acts as a drive wheel and as a steered wheel, and the Swivel castor acts as a drag wheel. A mast assembly is between the thrust legs. The mast assembly has a fork that is raised and lowered. The mast assembly is moved back and forth along the thrust legs.

The load on the rear wheel that acts as a drive wheel serves, changes according to the position of the mast assembly and the weight of a load carried by the fork. If the mast assembly is in the foremost position and the weight of a load on the fork the maximum acceptable Has value, then the load acting on the drive wheel minimized. In this condition the drive wheel will spin, if the forklift is on a wet concrete floor or on a Floor is started in a cold room. This does not prevent just a quick acceleration of the vehicle, but causes also a swiveling of the rear of the vehicle to the left and towards right. In addition, the drive wheel is spinning worn out early.

To prevent the drive wheel from spinning is in the Japanese Unexamined Patent Publication No. 2-299402, No. 3-27701 and No. 11-178120 each have a device which reduces the torque from an engine.

In particular, each device reduces the moment from one  a drive wheel driving motor when the drive wheel is spinning.

In the devices according to laid-open publication no. 2-299402 and No. 3-27701 is based on the speed of a Motor and a current fed into the motor detects whether a drive wheel spins. In the device according to the Publication No. 11-178120 is based on the Speed and the acceleration of a drive wheel detects whether the drive wheel spins.

The above disclosures disclose no method of controlling the engine torque. Usually an engine is regulated so that the engine torque in the degree is reduced, which corresponds to the degree of rotation. To do that Engine torque to reliably prevent cranking To control a drive wheel, several factors such as Example of the range of load acting on the drive wheel, the Friction of the drive wheel and the properties of the engine to be viewed as. However, the factors change with that respective vehicle. So the control procedure must be like this be adjusted so that it corresponds to the respective vehicle, and customizing the procedure is complicated.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to Drive control device for an electric company vehicle to provide a wheel spin with a simple one Construction reliably prevented.

To accomplish the above task and other aspects under the To solve the problem of the present invention is one Drive control device for an electric company vehicle provided that a drive wheel driven by a motor Has. The device has an actuator that for  Setting the torque of the motor is operated, a Spin detection device for detecting a Spin value, which is the degree of spin of the drive wheel represents, and means for controlling the engine. The Engine control device calculates a target torque of the engine according to the actuating size of the actuating element and controls the motor so that the motor generates the target torque. When the absolute value of the spin value is a predetermined one Spin determination value exceeds, then reduces the Engine control device, the target torque to a predetermined Rate to perform a spin prevention procedure.

Other aspects and advantages of the invention will be apparent from the following description together with the accompanying drawings clearer to understand the principles based on examples represent the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, along with its object and its Advantages most likely with reference to the following description of the currently preferred embodiments together with the accompanying drawings, where:

Fig. 1 according to a first embodiment of the present invention shows a block illustration of a thrust fork lift truck;

Figure 2 shows a side view of the forklift shown in Figure 1;

Figure 3 shows a top view of the forklift shown in Figure 1;

Fig. 4 is a graphical representation of a map M1 for calculating a target torque shows an engine;

Fig. 5 is a graph showing the relationship between a spin value ΔVD and the coefficient of friction between a rear wheel and a road surface during a drive mode;

Fig. 6 is a graph showing the relationship between a determination value Va and a vehicle speed;

Fig. 7 (a) to 7 (c) are graphs showing the changes of a front wheel speed VF movement of a rear wheel speed VD, and a motion through rotation value ΔVD show when the forklift is started on a wet road surface;

Fig. 8 (a) to 8 (c) are graphs showing the changes in the front wheel speed VF, the rear wheel speed VD and the through rotation value ΔVD show when an accelerator lever for a direction change at the same conditions as in Fig. 7 (a) to 7 (c ) is operated;

Fig according to a flow chart of a routine for determining, Figure 9 shows a second embodiment of the present invention, whether a through rotation preventing procedure is permitted.

Fig. 10 shows the relationship between the value of an acceleration mark FA with respect to the acceleration or deceleration of the forklift 10 ;

Fig. 11 shows a flow chart of a routine for setting the acceleration flag FA;

Figure 12 shows a graphical representation of changes in the front wheel moving speed VF, the rear moving speed VD, a vehicle acceleration AC and Rotation value ΔVD when the truck is driving on a dry road surface.

Fig. According to a fourth embodiment shows a graph of brake pressure data M2 for determining an auxiliary brake pressure PK 13;

FIG. 14 is a flowchart showing a brake control procedure is executed during the regenerative mode;

Fig. 15 according to a fifth embodiment is a flowchart showing a brake control procedure that is performed during the regenerative mode; and

Fig. 16 according to a sixth embodiment is a flowchart showing a drive control routine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment of the present invention will now be described with reference to FIGS. 1 to 8 (c). As shown in FIGS . 2 and 3, an operating vehicle, which in this embodiment is a reach truck 10 , has a vehicle body 14 and left and right push legs 15 that extend forward. Trailing wheels, which are left and right front wheels 11 L and 11 R, are supported by a respective thrust leg 15 . A rear wheel 12 and a castor 13 are located on the rear of the vehicle body 14 . The rear wheel 12 is driven and steered.

Each front wheel 11 L and 11 R has a brake 16 . For example, each brake 16 is a hydraulic friction drum brake. A mast assembly 17 is located between the thrust legs 15 . The mast assembly 17 is moved along the thrust legs 15 . A push cylinder 171 for moving the mast assembly 17 is located on the lower portion of the vehicle body 14 . The mast assembly 17 has a fork 17 a. The fork 17 a is raised and lowered by a lifting cylinder (not shown). The fork 17 a is also inclined together with the mast assembly 17 by the lifting cylinder.

The body 14 has a stand 20 in which an operator stands. Stand 20 is located in the rear right area of body 14 . The swivel castor 13 is located at stand 20 . An instrument panel 21 is located in front of stand 20 . An actuating element, which in this exemplary embodiment is an acceleration lever 23 , a lifting lever 24 , a push lever 25 and an inclination lever 26 are located on the instrument panel 21 . A box 14 a is to the left of booth 20 . A steering wheel 22 is located on the box 14 a. The steering wheel 22 is operated to steer the rear wheel 12 .

A drive unit 18 is in the box 14 a. The drive unit 18 has a drive motor 19 which is , for example, an AC induction motor. The rear wheel 12 is supported by the drive unit 18 and driven by the drive motor 19 . The drive unit 18 and the caster 13 are supported by the body by means of a suspension mechanism (not shown). The suspension mechanism prevents a large change in the load on the rear wheel 12 due to a shift in the center of gravity of the forklift 10 .

A brake pedal 100 is located on the bottom of the stand 20 . The brake pedal 100 is depressed when the rear wheel 12 is braked. Although not shown in the drawings, the brake pedal 100 is connected to a rear brake via a connection. If the brake pedal 100 is not depressed, the rear brake brakes the rear wheel 12 . When the brake pedal 100 is depressed, the rear brake releases the rear wheel 12 .

The circuit structure for controlling the drive motor 19 and the brake 16 will now be described. As shown in FIG. 1, a feed motor 31 actuates an oil pump 32 to deliver oil from an oil tank 30 to a brake control valve unit 33 and an oil control valve 34 . The oil control valve 34 controls the oil supply to the lift cylinder, the push cylinder 171 and the tilt cylinder. The oil control valve 34 controls the oil supply to the cylinders in accordance with an operation of the levers 23 , 24 and 25 .

The brake control valve unit 33 has an electromagnetic valve 33 b and an accumulator 33 a. Oil pumped by the oil pump 32 is first stored in the accumulator 33 a. The solenoid valve 33 b is operated on the basis of commands from the control device 44 . The control device 44 controls the electromagnet 33 b to adjust the pressure of the oil that is supplied from the accumulator 33 a to the brakes 16 . Each brake 16 brakes a corresponding front wheel 11 L, 11 R by a force that corresponds to the pressure of the supplied oil.

The control device 44 has, for example, a microcomputer, which has a CPU and a memory and controls all the operations of the forklift 10 . The control device 44 also has an inverter circuit. An accelerator lever sensor 40 is located under the instrument panel 21 . The accelerator lever sensor 40 detects the actuation variable ACC of the accelerator lever 23 or the position of the accelerator lever 23 , and sends a signal to the control device 44 that corresponds to the detected actuation variable ACC. The control device 44 feeds a current into the drive motor 19 which corresponds to the lever actuation variable ACC.

The acceleration lever 23 also acts as a direction lever for changing the direction of movement of the vehicle. That is, the accelerating lever 23 is normally in a neutral position. The lever 23 is moved forward or to a forward position when the forklift 10 moves forward, and it is moved backward or to a rearward position when the forklift 10 moves back. When the accelerator lever 23 is in the neutral position, the lever actuation amount ACC of the accelerator lever sensor 40 is defined as zero. The lever operation amount ACC represents the amount of forward or backward movement of the accelerator lever 23 from the neutral position.

A forward motion detection switch 401 and a backward motion detection switch 402 are turned off when the accelerating lever 23 is at the neutral position. When the accelerator lever 23 is moved from the neutral position to the forward position, the forward motion detection switch 401 is turned on and sends out a forward motion signal SF to the controller 44 . When the accelerator lever 23 is moved from the neutral position to the reverse position, the reverse motion detection switch 402 is turned on and sends out a forward motion signal SR to the controller 44 . On the basis of signals from the detection switches 401 , 402 , the control device 44 determines the direction of rotation of the drive motor 19 commanded by the acceleration lever 23 . In other words, the control device 44 determines the direction of movement of the forklift truck 10 commanded by the acceleration lever 23 . The particular direction need not necessarily be the actual direction in which the forklift 10 is moving.

A pair of rear wheel speed sensors 41 a, 41 b faces a gear that is attached to the output shaft of the drive motor 19 . Each wheel speed sensor 41 a, 41 b detects the teeth of the gear and emits pulse signals to the control device 44 , which correspond to the speed NM of the drive motor 19 . On the basis of the received pulse signals, the control device 44 calculates the rotational speed NM of the drive motor 19 and the rotational speed ND of the rear wheel 12, which will be described later.

The rear wheel speed sensors 41 a, 41 b are spaced apart from one another by a predetermined angular interval such that the phases of the signals from the rear wheel sensors 41 a, 41 b are offset by 90 °. On the basis of the phase difference between pulse signals from the sensors 41 a, 41 b, the control device 44 detects the current direction of rotation of the drive motor 19 or the current direction of movement of the forklift truck 10 .

A wheel angle sensor 42 is located near the drive unit 18 . The wheel angle sensor 42 detects the angle θ of the rear wheel 12 and sends a signal to the control device 44 which represents the detected wheel angle θ.

A pressure switch 43 is located on the brake control valve unit 33 . If the oil pressure in the accumulator 33 a falls below a predetermined value, then the pressure switch 43 sends a signal to the control device 44 . When receiving a signal from the pressure switch 43 , the control device 44 actuates the charging motor 31 to increase the oil pressure in the accumulator 33 a.

A pair of front wheel speed sensors 45 L, 45 R are arranged on the thrust legs 15 so that they correspond to the front wheel 11 L and 11 R, respectively. The left front wheel sensor 45 L sends a pulse signal to the control device 44 , the frequency of which corresponds to the speed NLF of the left front wheel 11 L. The right front wheel speed sensor 45 R sends a pulse signal to the control device 44 , the frequency of which corresponds to the speed NRF of the right front wheel 11 R.

The control device 44 controls the direction of rotation, the drive torque and the braking torque of the drive motor 19 on the basis of the lever actuation quantity ACC, the rear wheel speed ND, the motor speed NM, the wheel angle θ and the front wheel speeds NLF, NRF. The drive torque refers to a torque that is generated by the drive motor 19 for moving the forklift 10 . The braking torque refers to a torque that is generated by the drive motor 19 for braking the forklift 10 .

In this exemplary embodiment, the drive motor 19 generates a braking torque as a result of a regenerative braking process during a change of direction. The direction change refers to a change of the accelerator lever 23 from the forward position to the reverse position or from the reverse position to the forward position when the forklift 10 is traveling to change the direction of movement of the vehicle. The change of direction allows the forklift 10 to start moving in a direction opposite to the current direction of movement after it is temporarily stopped. From the operation of the accelerator lever 23 for changing direction until the forklift 10 stops, or in other words, when the actual direction of movement of the forklift 10 is different from the direction indicated by the accelerator lever 23 , the drive motor 19 generates a braking torque for braking the rear wheel 12 .

When the accelerator lever 23 is moved from the neutral position to the forward position or the reverse position, the corresponding switch 401 , 402 outputs a signal (the forward movement signal SF or the backward movement signal SR). When the accelerator lever 23 is operated to change direction, the movement direction signal sent to the controller 44 changes from the forward movement signal SF to the backward movement signal SR or from the backward movement signal SR to the forward movement signal SF. Based on the forward movement signal SF or the backward movement signal SR, the controller 44 detects the direction of movement of the forklift 10 indicated by the accelerating lever 23 , which does not necessarily coincide with the actual direction of movement.

The control device 44 calculates the rotational speed NM of the drive motor 19 on the basis of pulse signals from the rear wheel speed sensors 41 a, 41 b and detects the direction of rotation of the drive motor 19 or the current direction of movement of the forklift truck 10 . Then, based on the engine speed NM and the lever operation amount ACC, the control device 44 calculates a target value of a torque that must be generated by the drive motor with reference to a map M1 shown in FIG. 4.

The map M1 in FIG. 4 was previously stored in a memory of the control device 44 . Figure M1 defines the values of the target torque in relation to the engine speed NM and the lever actuation variable ACC. If the current direction of travel of the forklift 10 is the same as the direction of travel indicated by the accelerator lever 23 , then the controller 44 defines the engine speed NM as a positive value and refers to the map M1 to drive the engine 19 in a drive mode Taxes. In this case, the calculated target torque is a target value of the driving torque for moving the forklift 10 in a direction indicated by the acceleration lever 23 . In addition, if the accelerator lever 23 is in the forward position or in the reverse position when the forklift 10 is not moving, then the controller 44 defines the engine speed NM as a positive value and refers to the map M1 to the drive motor 19 in FIG To control drive mode of operation.

If the current direction of movement of the forklift 10 is different from the direction of movement indicated by the accelerator lever 23 , then the controller defines the engine speed NM as a negative value and refers to the map M1 to drive the drive motor 19 in a regenerative mode (brake Mode of operation). In this case, the calculated target torque is a target value of the braking torque for braking the forklift truck 10 . During the direction changeover, the drive motor 19 is controlled in the regenerative operating mode in such a way that the motor 19 generates a braking torque.

If the lever actuation quantity ACC decreases during the drive operating mode, the value of the calculated target drive torque can be negative. In such a case, the target drive torque essentially represents the target braking torque, and the drive motor 19 generates a braking torque. The drive mode of operation according to this description can thus include the state of the regenerative mode of operation in which the drive motor 19 generates a braking torque.

The controller 44 gradually increases or decreases the torque of the drive motor 19 such that the torque of the motor 19 reaches the calculated target value. The moment is not changed suddenly and therefore no shock is generated.

As described above, the drive motor 19 is controlled to generate a drive torque corresponding to the engine speed NM and the lever operation amount ACC when the current direction of movement of the forklift 10 is the same as the direction of movement indicated by the accelerator lever 23 . As a result, the forklift 10 moves in a direction indicated by the accelerating lever 23 . If the current direction of motion of the forklift 10 is opposite to the direction indicated by the accelerator lever 23 in the direction, namely when the accelerator lever 23 is operated for a direction switch to the drive motor 19 is controlled corresponding braking torque for producing an engine speed NM, and the lever operation amount ACC. As a result, the rear wheel 12 is braked and the forklift 10 is decelerated.

When the forklift 10 is accelerating or decelerating, the controller 44 determines whether the rear wheel 12 , which is the drive wheel, is spinning relative to the road surface. If the rear wheel 12 is spinning, then the control device 44 adjusts the torque of the drive motor 19 to stop the spinning of the rear wheel 12 .

A spin prevention procedure will now be described. The controller 44 calculates the moving speed of the rear wheel 12 with respect to the road surface based on the rear wheel speed ND and the diameter of the rear wheel 12 . The rear wheel moving speed VD represents the vehicle speed at the rear wheel 12. Since the rear wheel moving speed VD is calculated based on the rear wheel speed ND, the calculated rear wheel speed VD is different from the actual moving speed of the rear wheel 12 when the rear wheel 12 spins relative to the road surface.

The controller 44 calculates the moving speed VLF of the left front wheel 11 L relative to the road surface based on the rotation speed NLF of the left front wheel and the diameter of the left front wheel 11 L. The controller 44 also calculates the moving speed VRF of the right front wheel 11 R relative to that Road surface based on the right front wheel speed NRF and the diameter of the right front wheel 11 R. The controller 44 detects which of the front wheels 11 L, 11 R is radially outward during cornering based on the wheel angle A of the rear wheel 12 . Then, the controller 44 selects the moving speed of the radially outer front wheel as the front wheel moving speed VF. If the wheel angle θ is zero, namely when the forklift 10 moves straight, then the movement speed of the front wheels 11 L, 11 R is selected as the front-wheel moving speed VF.

Then, the controller 44 calculates a moving speed VDP of the rear wheel 12 by multiplying the front wheel moving speed VF by a conversion factor, which will be described later. In order to distinguish the moving speed VDP from the rear wheel moving speed VD calculated based on the rear wheel speed ND, the moving speed VDP is hereinafter referred to as a converted moving speed VDP or an estimated moving speed VDP. The converted moving speed VDP corresponding to the vehicle speed at the rear wheel 12, 11 L, 11 R is estimated on the basis of the speed of one of the front wheels.

The conversion factor is either a factor KL, which is used when the forklift 10 makes a left turn, or it is a factor KR, which is used when the forklift 10 makes a right turn. The conversion factors KL, KR are calculated according to the following equations.
KL = LW / (LW.cosθ + (LT - LD) sinθ)
KR = LW / (LW.cosθ + (LT + LD) sinθ)

In the equations, LW represents the wheelbase is, LT is half the track width between the front wheels 11 L and 11 R, and LD is the lateral displacement of the rear wheel 12 relative to the center between the front wheels 11 L and 11 R. As this is described above , various conversion factors are used when the forklift 10 makes a left turn and when the forklift 10 makes a right turn. This is because the rear wheel 12 , which is the steered wheel, is laterally offset from the center between the front wheels 11 L, 11 R (see FIG. 3). If the wheel angle θ is zero, namely when the forklift 10 is moving straight, then both conversion factors KL and KR are 1. Therefore, if the wheel angle θ is zero, one of the conversion factors KL, KR is used.

The converted moving speed VDP is calculated based on the rotational speeds NLF, NRF of the front wheels 11 L, 11 R. The front wheels 11 L, 11 R are dragged while the forklift 10 is moving while being in contact with the road surface. Unlike the rear wheel 12 , which is the drive wheel, the front wheels 11 L, 11 R do not spin on the road surface when the forklift 10 is accelerated or decelerated. Thus, the converted movement speed VDP essentially represents the exact movement speed of the rear wheel 12 .

Then, the controller 44 calculates a spin value ΔVD of the rear wheel 12 based on the rear wheel moving speed VD and the converted moving speed VDP according to the following equation.

ΔVD = VD - VDP

In the equation, the spin value ΔVD represents the difference between the rear wheel moving speed VD and the converted moving speed VDP. If the rear wheel 12 spins during the drive mode or during acceleration, the spin value ΔVD is positive. If the rear wheel 12 is spinning during the regenerative mode or during a deceleration, the spin value ΔVD is negative. When the absolute value of the spin value ΔVD exceeds a determination value Va, the controller 44 determines that the rear wheel 12 is spinning on the road surface.

If it is determined that the rear wheel 12 is spinning, then the controller 44 limits the torque of the drive motor 19 to stop the spinning. In particular, the control device 44 reduces the normal target torque calculated on the basis of the map M1 according to FIG. 4 by, for example, 10% and defines the result as a target torque of the drive motor 19 . As a result, the drive torque of the drive motor 19 is limited during the drive mode, whereby the spinning of the rear wheel 12 due to the acceleration is stopped. During the regenerative mode of operation, the braking torque of the drive motor 19 is limited, which limits the spinning of the rear wheel 12 as a result of the deceleration.

If the absolute value of the spin value ΔVD exceeds the determination value Va during the regenerative mode of operation, then the control device 44 controls the valve unit 33 to actuate the brakes 16 as required. As a result, the reduction in the braking torque due to the limitation of the driving torque of the motor 19 is compensated for.

The Fig. 5 is a graph showing the relation between the rotation value ΔVD and the friction coefficient of the rear wheel 12 and the road surface. The coefficient of friction is maximum when the spin value ΔVD is 0.1 m / s. When the spin value ΔVD increases from zero to 0.1 m / s, the coefficient of friction increases relatively suddenly. When the spin value ΔVD increases from 0.1 m / s to 0.3 m / s, the coefficient of friction decreases relatively suddenly. As the spin value ΔVD increases from 0.3 m / s, the coefficient of friction gradually decreases.

For an operating vehicle that has a relatively low maximum speed, such as the reach truck 10 , the relationship between the spin value ΔVD and the coefficient of friction is substantially constant regardless of the vehicle speed. The determination value Va is set to correspond to a range of the spin value ΔVD or a hatched area in FIG. 5 in which the coefficient of friction is relatively large.

The determination value Va is preferably changed in accordance with the operating state of the forklift 10 . For example, if a relative drive torque has to be generated by the drive motor 19 when the forklift 10 is started, the determination value Va is set to be relatively small compared to other cases. In the example shown in the graph in FIG. 6, the determination value Va is set to 0.1 m / s in a low vehicle speed range that includes an acceleration for starting the forklift 10 . For other vehicle speed ranges, the determination value Va is set at 0.2 m / s. The vehicle speed is represented, for example, by the converted movement speed VDP. When the forklift 10 is accelerating, the determination value Va may be different than when the forklift 10 is decelerating.

FIGS. 7 (a) to 7 (c) are graphs showing the front-wheel moving speed VF, rear wheel of the moving speed VD and the through rotation value ΔVD when the forklift 10 is started on a wet road surface. The forklift 10 moves forward and the wheel angle θ is zero. The mast assembly 17 is in the foremost position and the weight of a load on the fork 17 a has the maximum acceptable value. The determination value Va is set to 0.1 m / s from the point in time zero at which the forklift 10 is started up to the lapse of 5.5 seconds. Thereafter, the determination value Va is set at 0.2 m / s.

If the absolute value of the spin value ΔVD exceeds the determination value Va, then the target drive torque of the drive motor 19 is reduced by 10% from the normal value calculated in accordance with the map M1 shown in FIG. 4. During the anti-skid control procedure in the driving mode, the skid value ΔVD fluctuates around 0.2 m / s in a range of 0.1 to 0.2 m / s. The rear wheel moving speed VD shown in FIG. 7 (b) increases together with the front wheel moving speed VF shown in FIG. 7 (a) while in a range of 0.1 to 0.2 m / s fluctuates. In this way, when the forklift 10 starts on a wet road and the load on the rear wheel 12 is minimal, the rear wheel 12 is prevented from spinning and the forklift 10 is started reliably.

The determination value Va is set to 0.1 m / s from the start of the forklift 10 to the elapse of 5.5 seconds. In other words, the determination value Va is relatively small in a low speed range, such as immediately after the forklift 10 starts, compared to other speed ranges. Therefore, when the forklift 10 is started, the driving force of the rear wheel 12 is reliably transmitted to the road surface, and the forklift 10 is gently accelerated.

When the anti-skid control procedure is carried out, the rate by which the normal target torque is reduced is determined so that the absolute value of the skid value ΔVD falls below the determination value Va at least four times per second. Therefore, during the anti-skid procedure, the forklift acceleration change cycle is four times per second or more. If the rate by which the normal target torque is reduced is small, the cycle of changing the acceleration is shortened, which improves the driving quality. On the other hand, the rate by which the normal target torque is reduced is preferably large in order to obtain the maximum driving force while preventing the rear wheel 12 from spinning. Thus, in this embodiment, the rate by which the normal target torque is reduced is set to 10%, which ensures a maximum driving force without the operator feeling disturbed.

The Fig. 8 (a) to 8 (c) show changes in the front wheel moving speed VF, the rear moving speed VD and the through rotation value ΔVD, when the accelerator lever 23 in the same conditions as in the cases shown in FIGS. 7 (a) to 7 (c ) is actuated for a change of direction. In the cases according to FIGS. 8 (a) to 8 (c), the determination value Va is always 0.2 m / s. After the accelerator lever 23 is operated to change direction, the regenerative operation is performed for six seconds, and then the drive operation is performed.

If the absolute value of the spin value ΔVD exceeds the determination value Va, then the target drive torque of the drive motor 19 is reduced by 10% from the normal target value, which is calculated in accordance with the map M1 shown in FIG. 4. During the anti-skid control procedure in the regenerative mode, the skid value ΔVD fluctuates around -0.2 m / s in a range of 0.1 to 0.2 m / s. The rear wheel moving speed VD shown in FIG. 8 (b) decreases along with the front wheel moving speed VF shown in FIG. 8 (a) while in a range of 0.1 to 0.2 m / s fluctuates. Thus, when the forklift 10 is traveling on a wet road surface and the load on the rear wheel 12 is minimal, the rear wheel 12 is prevented from spinning and the forklift 10 is reliably decelerated.

During the anti-skid control at the Regenerative mode of operation will reduce the normal target torque by 10% reduced. Therefore, the braking force can be maximized without that the operator feels disturbed.

As described above, the target torque of the drive motor 19 is reduced from the normal target value by a predetermined rate when the absolute value of the spin value ΔVD exceeds the determination value Va, so that the spin of the rear wheel 12 is stopped. Thus, with a simple structure, the rear wheel 12 , which is the drive wheel, is reliably prevented from spinning.

The spin value ΔVD represents the difference between the rear wheel moving speed VD and the converted moving speed VDP. Thus, even if the vehicle speed changes, the spin value ΔVD has substantially the same relationship to the coefficient of friction between the rear wheel 12 and the road surface. Therefore, the skid prevention procedure is reliably performed based on the skid value ΔVD regardless of the vehicle speed.

The determination value Va is set to correspond to a range of the spin value ΔVD in which the coefficient of friction is relatively large (in the hatched area of the graph in FIG. 5). When the skid prevention procedure is performed, the skid value ΔVD fluctuates around the determination value Va (see Figs. 7 (c) and 8 (c)). Thus, during the anti-skid procedure, the coefficient of friction between the rear wheel 12 and the road surface is maintained at a relatively large value, and the rear wheel 12 has sufficient grip.

During the anti-skid procedure, the rate, which reduces the normal target torque, not to 10% limited but it can range from 10% to 20%, from 5% vary up to 30% or from 0% to 50%.

During the anti-skid procedure, the Frequency with which the spin value ΔVD per second falls below the determination value Va.

A second embodiment according to the present invention will now be described with reference to FIGS. 1 to 8 (c). The differences from the first embodiment are mainly described below. In the second embodiment, the skid prevention procedure based on the skid value ΔVD and the determination value Va is permitted only when the operating condition of the forklift 10 satisfies a predetermined approval condition. If the operating condition of the forklift 10 does not meet the approval condition, then the spin prevention procedure will not be performed even if the absolute value of the spin value ΔVD exceeds the determination value Va.

FIG. 9 shows a flow chart for determining whether the anti-skid procedure should be allowed. The controller 44 executes the routine shown in FIG. 9 at predetermined intervals.

At step S1, the controller 44 determines whether an approval flag FX is one. The approval mark FX indicates whether the anti-skid procedure is to be approved. A value of one of the registration mark FX indicates that the anti-skid procedure is permitted, and a value of zero indicates that the anti-skid procedure is prohibited. If the approval mark FX is zero, then the controller 44 proceeds to step S2.

At step S2, the controller 44 determines whether the absolute value of the spin value ΔVD is larger than a predetermined allowance determination value Vb. The allowance determination value Vb is larger than the spin determination value Va used to determine whether the rear wheel 12 is spinning. The allowance determination value Vb is determined in consideration of the spin value ΔVD when the rear wheel 12 can not maintain a strong grip on a road surface on which the rear wheel 12 is unlikely to spin, for example, a road surface with a relatively large coefficient of friction such as a dry road surface. In this embodiment, the admission determination value Vb is set to 0.5 m / s.

At step S2, if the absolute value of the skid value ΔVD is larger than the allowance determination value Vb, then the controller 44 proceeds to step S3 to allow the skid prevention procedure. At step S3, controller 44 sets admission flag FX to one and temporarily suspends the current routine. If the absolute value of the spin value ΔVD is equal to or less than the allowance determination value Vb, the controller 44 continues to hold the allowance flag FX at zero and temporarily suspends the current routine.

If the approval flag FX is one at step S1, the controller 44 proceeds to step S4. At step S4, the controller 44 determines whether the vehicle speed V is less than a predetermined stop determination value Vc. The stop determination value Vc represents an extremely low value of the vehicle speed V at which the forklift 10 substantially stops, and is set to 1 km / h (1 km / h = 1000 m / 3600 s). The vehicle speed V represents, for example, the average of the converted moving speed VDP or the average of the front wheel moving speeds VLF, VRF in the embodiments according to FIGS. 1 to 8 (c).

At step S4, if the vehicle speed V is lower than the stop determination value VC, the controller 44 proceeds to step S5 to prohibit the skid prevention procedure. At step S5, controller 44 sets admission flag FX to zero and temporarily suspends the current routine. If the vehicle speed V is equal to or greater than the stop determination value Vc, the controller 44 continues to hold the flag FX at one and temporarily suspends the current routine.

As described above, the registration mark FX is kept at zero until the absolute value of the spin value ΔVD exceeds the registration determination value Vb once when the forklift 10 is accelerated or decelerated. While the approval mark FX is zero, the skid prevention procedure is not performed even if the absolute value of the skid value ΔVD exceeds the skid determination value Va.

For example, if the forklift 10 is moving on a road surface where the rear wheel 12 is unlikely to spin, for example, on a dry road surface, or if the load on the rear wheel 12 is relatively large, then the absolute value of the spin value ΔVD can be between Spin determination value Va and the approval determination value Vb. In such a case, it is determined that the rear wheel 12 maintains a relatively strong grip with the road surface, and the registration mark FX is set to zero so that the anti-skid procedure is not performed. In other words, the anti-skid control is not performed even if the absolute value of the skid value ΔVD exceeds the skid determination value Va when the grip of the rear wheel 12 with the road surface is determined to be strong.

If the absolute value of the spin value ΔVD the Admission determination value Vb exceeds, then the Approval mark FX kept at one until the Vehicle speed V below the stop determination value Vc falls. While the registration mark FX kept at one the anti-skid procedure will be on the Basis of the comparison between the spin value ΔVD and the spin determination value Va.

If the forklift 10 is traveling on a floor where the forklift 10 is likely to spin, for example on a wet road surface, or if the load on the rear wheel 12 is relatively small, then the absolute value of the spin value ΔVD can be both the spin determination value Va and exceed the admission determination value Vb. In such a case, it is determined that the rear wheel 12 cannot maintain a strong grip with the road surface, and the approval flag FX is set to one so that the anti-skid procedure is approved. In other words, the anti-skid procedure is permitted when it is determined that the rear wheel 12 cannot maintain a strong grip with the road surface.

As described above, the anti-skid procedure is inhibited when the forklift 10 is unlikely to spin. Therefore, the anti-skid procedure is not performed too often. As a result, the forklift 10 is reliably accelerated and decelerated while preventing the rear wheel 12 from spinning.

If the absolute value of the spin value ΔVD the Admission determination value Vb exceeds, then the Anti-skid procedure approved. After that the Anti-spinning procedure prevented when the Vehicle speed V below the stop determination value Vc falls. It is only by comparing the Spin value ΔVD and the vehicle speed V with the appropriate determination values adequately determines whether the Anti-skid procedure is allowed.

A third embodiment of the present invention will now be described with reference to FIGS. 10 to 12. The differences from the second exemplary embodiment according to FIG. 9 are mainly described below. In addition to the procedure of the second embodiment shown in FIG. 9, a determination value for determining whether the rear wheel 12 is spinning is changed in accordance with an acceleration or deceleration of the forklift 10 . In particular, when an acceleration or deceleration is small, a relatively small first spin determination value Va1 is used. If the acceleration or deceleration is large, a relatively large second spin determination value Va2 is used. For example, the first skid determination value Va1 is set to 0.2 m / s, and the second skid determination value Va2 is set to 0.3 m / s.

If the forklift 10 can be accelerated or decelerated at a relatively high rate, then the forklift 10 is in the state that the rear wheel 12 is unlikely to spin. Therefore, when the acceleration or deceleration is large, the second skid determination value Va2 is used to prevent the skid prevention procedure from being performed excessively.

The controller 44 calculates the vehicle acceleration AC based on the change in the vehicle speed V during a predetermined period ΔT. The vehicle acceleration AC has a positive value when the forklift 10 is accelerated and has a negative value when the forklift 10 is decelerated. The controller compares the absolute value of the vehicle acceleration AC with a predetermined acceleration determination value to determine whether the forklift is in a high acceleration state or a large deceleration state. If it is determined that the forklift 10 is in the high acceleration or deceleration state, then the controller 44 sets the acceleration flag FA to one. On the other hand, the control device 44 sets the acceleration mark FA to zero. The zero value of the acceleration mark FA indicates that the forklift 10 is in a low acceleration state or in a small deceleration state.

FIG. 11 is a flowchart showing a routine for setting the acceleration flag FA. The controller 44 repeatedly executes the routine shown in FIG. 11 in the period ΔT.

At step S11, the controller 44 determines whether the registration flag FX is one. The approval mark FX is the same as in the second embodiment, and is used to determine whether the anti-skid control is allowed. If the approval flag FX is not one but zero, then controller 44 determines that the spin prevention procedure is prohibited and temporarily suspends the current routine.

If the approval flag FX is one at step S11, then the controller 44 determines that the anti-skid procedure is approved and proceeds to step S12. At step S12, the controller 44 determines whether the acceleration flag FA is zero. If the acceleration flag FA is zero, then the controller 44 proceeds to step S13. At step S13, the controller 44 determines whether the absolute value of the vehicle acceleration AC is larger than a predetermined first acceleration determination value AC1.

If the absolute value of the vehicle acceleration AC is greater than the first acceleration determination value AC1, then the controller 44 determines that the forklift 10 has changed from the low acceleration state to the large acceleration state or from the small deceleration state to the large deceleration state. The control device 44 then proceeds to a step S15. At step S15, controller 44 sets acceleration flag FA to one and temporarily suspends the current routine. At step S13, if the absolute value of the vehicle acceleration AC is less than the first acceleration determination value AC1, then the controller 44 determines that the forklift 10 maintains the small acceleration or the small deceleration state while maintaining the zero value of the acceleration flag FA. Thereafter, controller 44 temporarily suspends the current routine.

If the acceleration flag FA is one at step S12, the controller 44 proceeds to step S14. At step S14, the controller 44 determines whether the absolute value of the vehicle acceleration AC is less than a predetermined second acceleration determination value AC2. The second acceleration determination value AC2 is smaller than the first acceleration determination value AC1.

If the absolute value of the vehicle acceleration AC is less than the second acceleration determination value AC2, then the controller 44 determines that the forklift 10 has changed from the large acceleration state to the small acceleration state or from the large deceleration state to the small deceleration state, and it proceeds to step S16. At step S16, controller 44 sets acceleration flag FA to zero and then temporarily suspends the current routine. If the absolute value of the vehicle acceleration AC is greater than the second acceleration determination value AC2, then the controller 44 determines that the forklift 10 maintains the high acceleration state or the large deceleration state. In this case, controller 44 maintains one of acceleration flag FA and suspends the current routine.

As described above, when the acceleration flag FA is currently zero, the absolute value of the vehicle acceleration AC is compared with the first acceleration determination value AC1. If the acceleration mark FA is currently one, the absolute value of the vehicle acceleration AC is compared with the second acceleration determination value AC2, which is smaller than the first acceleration determination value AC1. These comparisons are made to compensate for hysteresis errors of the vehicle acceleration AC. In this embodiment, the first acceleration determination value AC1 is set to 1.0 m / s ² , and the second acceleration determination value is set to 0.2 m / s ² .

When accelerating, the forklift 10 changes from the low acceleration state to the high acceleration state at 1.0 m / s ² and changes from the high acceleration state to the low acceleration state at 0.2 m / s ² . Upon deceleration, the forklift 10 changes from the small deceleration state to the large deceleration state at -1.0 m / s ² and changes from the large deceleration state to the small deceleration state at -0.2 m / s ² .

If the approval flag FX is one, then the controller 44 determines the skid determination value used in the anti-skid control corresponding to the acceleration flag FA. That is, when the acceleration flag FA is zero, the controller 44 executes the skid prevention procedure based on the comparison between the skid value ΔVD and the first skid determination value Va1. If the acceleration flag FA is one, then the controller 44 performs the skid prevention procedure based on the comparison between the skid value ΔVD and the second skid determination value Va2.

FIG. 12 shows a graphical representation of the front wheel speed VF, the rear wheel speed VD, the vehicle acceleration AC and Rotation value ΔVD when the forklift 10 is traveling on a dry road surface. The wheel angle θ is zero. The mast assembly 17 is in the rearmost position. The load weight on the fork 17 a is zero. It is extremely unlikely that the operating condition of the truck 10 from spinning the truck 10 causes.

According to the graphic representation in FIG. 12, the acceleration lever 23 is actuated for a change of direction between the times T ₂ and T ₃ . Thus, the forklift 10 , which is in the acceleration state, changes to the deceleration state by the change of direction, and is then stopped. Then the forklift is started in the opposite direction.

The vertical axis of the graph in FIG. 12 represents the speed or acceleration. To simplify the description, the determination values Va1, Va2, AC1 and Vb have negative values when the vehicle acceleration AC and the spin value ΔVD have negative values.

The period between the times T ₁ and T ₂ is a period for accelerating the forklift 10 before the direction change is carried out. The period between times T ₅ and T ₆ is a period for accelerating the forklift 10 in the reverse direction. During these periods T ₁ to T ₂ , T ₅ to T ₆ , it is determined that the forklift 10 is in the high acceleration state, and the acceleration flag FA is set to one. The period between the times T ₃ and T ₄ is a period for delaying a change of direction. During the period T ₃ to T ₄ , it is determined that the forklift 10 is in the large deceleration state, and the acceleration flag FA is set to one. Accordingly, during the period T ₁ to T ₂ , during the period T ₃ to T ₄ and during the period T ₅ to T _6, the second skid determination value Va2 is used as the skid determination value used in the anti-skid procedure. In particular, the spin determination value is set at 0.3 m / s. In periods other than those mentioned above, the first skid determination value Va1 is used as the skid determination value, which is 0.2 m / s.

If the forklift 10 is accelerated before changing direction, then the spin value ΔVD does not exceed the approval determination value Vd. Thus, the anti-skid procedure is not carried out. If the forklift 10 stops and starts during the direction change, then the spin value ΔVD temporarily exceeds the allowance determination value Vb at about the time T ₄ and then falls below the second spin determination value Va2. At the instant T ₅ immediately after the instant T ₄ , the second spin determination value Va2 is selected. Thus, the anti-skid procedure is not carried out.

It is assumed that the anti-skid procedure based on the allowance determination value Vb is not inhibited during a direction change delay. In this case, the skid prevention procedure is carried out immediately before the time T ₃ on the basis of the comparison between the skid value ΔVD and the first skid determination value Va1. At the time T ₃ , the second spin determination value Va2 is used. Since the skid value AVD does not exceed the second skid determination value Va2, the skid prevention procedure is not carried out.

It is assumed that the anti-skid procedure based on the permission determination value Vb is inhibited during a deceleration of the forklift 10 in the direction change. In this case, the skid value ΔVD does not exceed the allowance determination value Vb, as shown by a broken line D in FIG. 12. Therefore, the spinning prevention procedure is not carried out even though the spinning value ΔVD exceeds the first spinning determination value Va immediately before the time T ₃ . The rotation value ΔVD exceeds the second rotation determination value Va2 after the time T ₃ . However, since the skid value ΔVD does not exceed the permission determination value Vb, the skid prevention procedure is not carried out.

As described above, the second spin determination value Va2, which is relatively large, is used when an acceleration or deceleration of the forklift 10 is relatively large. If the forklift 10 can be accelerated or decelerated at a relatively large rate, the operating condition is unlikely to cause the forklift 10 to spin. Therefore, using the second skid determination value Va2, the excessive execution of the skid prevention procedure is prevented when the acceleration or deceleration is large. Accordingly, the forklift 10 is reliably accelerated or decelerated.

The exemplary embodiments according to FIGS. 9 to 12 can be modified as follows.

Instead of changing the skid determination value according to the acceleration or deceleration of the forklift 10 , the skid prevention procedure can be inhibited regardless of the skid value ΔVD when the forklift 10 is in the high acceleration or deceleration state. In other words, the anti-skid procedure can only be permitted if it is determined that the forklift 10 is in the low acceleration or low deceleration state. This simplifies the procedure.

Instead of prohibiting the skid prevention procedure based on the permission determination value Vb, only the skid determination value needs to be changed according to the acceleration or deceleration of the forklift 10 . Namely, the procedure of the embodiment shown in FIG. 9 can be omitted, and only the procedures of the embodiment shown in FIGS. 10 to 12 need be carried out. In this case, step S11 of the routine shown in FIG. 11 is omitted.

In the embodiment shown in FIGS. 10 to 12 can be changed by rotating 10, the second determination value Va2 in accordance with the operating state of the forklift. If the mast assembly 17 is in the foremost position, for example, if the load on the fork 17 a is zero, the second spin determination value Va2 may be different than if the load is not zero. This enables fine control to be carried out.

Instead of using both acceleration determination values AC1, AC2 to determine the acceleration state of the forklift 10 , a single acceleration determination value can be used.

When the forklift is accelerated, the spin determination value or the acceleration determination value may be different than when the forklift 10 is decelerated.

The vehicle acceleration AC can be increased by an additional Accelerometer are detected.

A fourth embodiment of the present invention will now be described with reference to FIGS. 13 and 14. The differences from the first exemplary embodiment according to FIGS. 1 to 8 (c) are mainly described below. The embodiment according to FIGS. 13 to 15 relates to a braking procedure for the front wheels 11 L, 11 R, which is carried out with the anti-skid procedure of the regenerative mode of operation. Namely, as in the first embodiment shown in FIGS. 1 to 8 (c), the brakes 16 are operated as needed to brake the front wheels 11 L, 11 R in this embodiment when the braking torque of the drive motor 19 is prevented from spinning of the rear wheel 12 is limited during the regenerative mode of operation. As a result, the reduction in the braking force due to the limitation of the braking torque of the drive motor 19 is compensated for.

This embodiment relates to details of a such a brake control procedure.

When the skid prevention procedure is performed during the regenerative mode, the deceleration of the forklift 10 is affected by the braking force (main braking force) applied to the drive wheel 12 by the drive motor 19 and by the braking force applied to the front wheels 11 L, 11 R by the brakes 16 ( Auxiliary braking force) determined. The auxiliary braking force is determined by the pressure of the oil supplied to the brakes 16 by the brake control valve unit 33 or by the auxiliary brake pressure. The control device 44 adjusts the auxiliary braking force in accordance with the brake pressure data M2 shown in FIG. 13 so that the deceleration of the forklift 10 remains in a reasonable range. The brake pressure data M2 shown in FIG. 13 was previously stored in the memory of the control device 44 .

The brake pressure data M2 are used to determine the auxiliary brake pressure PK used with the auxiliary braking force in one Interrelation stands. The brake pressure data M2 set four levels the auxiliary brake pressure PK fixed, namely a first to fourth Brake pressure P0 to P3. The third brake pressure P2 is on Reference value P. The first brake pressure P0 is zero. The second Brake pressure P1 is 30% lower than the reference value or 0.7 P. The fourth brake pressure P3 is 30% greater than that Reference value P or 1.3 P.

The controller 44 selects one of the first to fourth brake pressures P0 to P3 based on the vehicle deceleration β by referring to the brake pressure data M2. The selected brake pressure is set as the auxiliary pressure PK. The vehicle deceleration β is calculated based on the change in the vehicle speed V in a predetermined period. The vehicle speed V is represented, for example, by the average of the front wheel moving speeds VLF, VRR described in the first embodiment shown in FIGS. 1 to 8 (c).

As shown by the brake pressure data M2 shown in FIG. 13, the first brake pressure P0 corresponds to a range of the vehicle deceleration β that is equal to or larger than β5. The second brake pressure P1 corresponds to a range of the vehicle deceleration β between β3 and β6. The third brake pressure P2 corresponds to a range of the vehicle deceleration β between β1 and β4. The fourth brake pressure P3 corresponds to a range of the vehicle deceleration β that is equal to or less than β2. The vehicle deceleration values β1 to β6 satisfy the inequality 0 <β1 <β2 <β3 <β4 <β5 <β6. The first to fourth brake pressure P0 to P3 and the vehicle deceleration β satisfy the following equations:

P0: β ≧ β5

P1: β3 ≦ β ≦ β6

P2: β1 ≦ β ≦ β4

P3: β ≦ β2.

During the skid prevention procedure, the controller 44 starts operating the brakes 16 at the third brake pressure P2, which is the reference value P. If the vehicle deceleration β is in the range corresponding to the current auxiliary brake pressure PK, then the controller 44 determines that the current auxiliary brake pressure PK is appropriate and maintains the current auxiliary brake pressure PK. If the vehicle deceleration β is outside the range that corresponds to the current auxiliary pressure PK, then the controller 44 determines that the current auxiliary brake pressure PK is inappropriate and changes the auxiliary brake pressure PK such that the auxiliary brake pressure PK corresponds to the vehicle deceleration β. That is, as shown in FIG. 13, when the vehicle deceleration β exceeds the upper value of the range corresponding to the current auxiliary brake pressure PK, the auxiliary brake pressure PK is decreased by one step. If the vehicle deceleration β falls below the lowest value of the range corresponding to the current auxiliary brake pressure PK, the auxiliary brake pressure PK is increased by one step.

Any area of vehicle deceleration β that is one of the first to fourth brake pressure corresponds to P0 to P3, overlaps with the areas of vehicle deceleration β that the adjacent  Brake pressure ranges correspond. This is said to be the hysteresis error compensate for the vehicle deceleration β.

FIG. 14 is a flowchart showing a brake control routine that is performed during the regenerative operation. The routine of FIG. 14 is started when the regenerative mode starts, and it is repeated at predetermined intervals during the regenerative mode. The regenerative mode of operation begins, for example, when the acceleration lever 23 is actuated for a change of direction.

At step S21, the controller 24 determines whether the current routine has started for the first time after the regenerative operation has started. If the current routine is the first routine, then the controller 44 proceeds to step S22. If the current routine is being executed a second time or more, the controller 44 proceeds to step S24.

At step S22, the controller 44 determines whether the vehicle speed V is equal to or greater than a predetermined low speed determination value Vd. If the vehicle speed V is less than the low speed determination value Vd, then the controller 44 determines that the forklift 10 is in a low speed area and ends the current routine. In this case, controller 44 will not execute this routine until the regenerative operation is complete. If the vehicle speed V is equal to or higher than the low speed determination value Vd, then the controller 44 determines that the forklift 10 is not in the low speed range and proceeds to step S23.

At step S24, the controller 44 determines whether the brakes 16 are applied. If the brakes 16 are not applied, the controller 44 proceeds to step S23. If the brakes 16 are applied, the controller 44 proceeds to step S25.

At step S23, the controller 44 determines whether the absolute value of the spin value ΔVD is greater than the determination value Va. If the absolute value of the spin value ΔVD is equal to or less than the determination value Va, then the controller 44 determines that the rear wheel 12 does not spin , and temporarily suspends the current routine. If the absolute value of the spin value ΔVD is larger than the determination value Va, then the controller 44 determines that the rear wheel 12 is spinning and proceeds to step S25. If it is determined that the rear wheel 12 is spinning, the braking torque of the drive motor 19 is similar to that of the first embodiment shown in FIGS. 1 to 8 (c) to stop the spinning.

At step S25, the controller 44 determines whether a predetermined waiting period t has passed since the brakes 16 were activated. The waiting period t corresponds to the time from the application of the brakes 16 to the stabilization of the vehicle deceleration β. The waiting period t is, for example, 100 to 300 ms. If the waiting period t has not passed, then the control device 44 proceeds to a step S31 and applies the brakes 16 with the current auxiliary brake pressure PK. Specifically, the control device 44 feeds a current corresponding to the auxiliary brake pressure PK into the electromagnetic valve 33 b of the brake control valve unit 33 .

If it is determined that the rear wheel 12 is spinning, then the auxiliary brake pressure PK is first set to the third brake pressure P2, which is the reference value P (see FIG. 13). Therefore, if it is determined in step S23 that the rear wheel 12 is spinning, then the brakes 16 are activated in step S31 with the third brake pressure P2.

If the waiting period t has passed in step S25, the control device 44 proceeds to step S26 and calculates the vehicle deceleration β. At step S27, the controller 44 determines whether the auxiliary brake pressure PK is appropriate for the vehicle deceleration β by referring to the brake pressure data M2 shown in FIG. 13. That is, the controller 44 determines that the vehicle deceleration β is in a range that corresponds to the current auxiliary brake pressure PK.

If the vehicle deceleration β is in the range corresponding to the current auxiliary brake pressure PK, then the controller 44 determines that the current auxiliary brake pressure PK is appropriate and proceeds to step S31. At step S31, controller 44 activates brakes 16 at the current auxiliary brake pressure PK. That is, the current auxiliary brake pressure PK is maintained.

If the vehicle deceleration β is outside the range of the current auxiliary brake pressure PK, then the controller 44 determines that the current auxiliary brake pressure PK is not appropriate and proceeds to step S28. At step S28, the controller 44 determines whether the vehicle deceleration β is larger than the upper value of the range corresponding to the current auxiliary brake pressure PK.

If the result at step S28 is affirmative, then controller 44 proceeds to step S29 and decreases the auxiliary brake pressure PK by one step. However, if the current auxiliary brake pressure PK is the first brake pressure P0 or the lowest value, then the auxiliary brake pressure PK is maintained at the first brake pressure P0.

If the result at step S28 is negative, namely when the vehicle deceleration β falls below the lowest value of the range corresponding to the current auxiliary brake pressure PK, then the controller 44 proceeds to step S30. At step S30, the controller 44 increases the auxiliary brake pressure PK by one step. However, if the current auxiliary brake pressure PK is the fourth brake pressure P3 or the highest value, then the auxiliary brake pressure PK is maintained at the fourth brake pressure P3.

After step S31 is reached from either step S29 or step S30, the control device 44 activates the brakes 16 by means of the new auxiliary brake pressure PK. Namely, the brakes 16 carry out the braking process by means of the auxiliary brake pressure PK, which has been offset by one step.

At step S32, the controller 44 determines whether the drive motor 19 maintains the regenerative mode. For example, if the accelerator lever 23 is operated in a direction that matches the current direction of movement of the forklift 10 during a deceleration in the direction switching, then it is determined that the regenerative mode is suspended. In addition, if the accelerator lever 23 is shifted to the neutral position during a deceleration of the direction switch, then it is determined that the regenerative mode is suspended.

If the regenerative mode is suspended, the controller 44 proceeds to step S34 and controls the brake control valve unit 33 so that the brakes 16 stop braking. Thereafter, controller 44 ends the routine. If it is determined that the regenerative operation is being maintained, the controller 44 proceeds to step S33.

At step S33, the controller 44 determines whether the vehicle speed V is equal to or less than the stop determination value Vc. The stop determination value Vc is a value of a low vehicle speed, at which it can be assumed that the forklift 10 is stationary, as was described in step S4 of the flow chart shown in FIG. 9. The stop determination value Vc is 1 km / h, for example. If the vehicle speed V is greater than the stop determination value Vc, the controller 44 temporarily suspends the current routine and then starts repeating this routine.

If the vehicle speed Vc is equal to or less than the stop determination value Vc, the controller 44 proceeds to step S34. At step S34, the controller 44 controls the brake control valve unit 33 so that the brakes 16 stop braking, and ends the current routine. Therefore, the braking operation of the front wheels 11 L, 11 R is stopped by the brakes 16 immediately before the forklift 10 stops. This prevents a shock generated during the braking operation of the forklift 10 due to the braking operation, which is transmitted to the vehicle body.

As described above, when the rear wheel 12 spins during a deceleration in the regenerative mode, the brakes 16 are activated with the third brake pressure P2, which brakes the front wheels 11 L, 11 R with a force that corresponds to the third brake pressure P2 equivalent. The braking process with the third brake pressure P2 is continued in a waiting period t. After the waiting period t, namely after the vehicle deceleration β has stabilized, the steps S26 to S31 are repeated so that the auxiliary brake pressure PK is set to the value which corresponds to the vehicle deceleration β. If the vehicle deceleration β increases, the auxiliary brake pressure PK is reduced accordingly, so that the braking force is reduced. If the vehicle deceleration β is reduced, the auxiliary brake pressure PK is increased so that the braking force increases. In this way, the braking force is set in accordance with the vehicle deceleration β, and the vehicle deceleration β is maintained in a predetermined appropriate range.

As shown in step S24, the spin determination in step S23 is not carried out while the brakes 16 are being operated for the following reason. That is, the spinning of the rear wheel 12 indicates that the braking distance of the forklift 10 is relatively long. Thus, after it is determined in step S23 that the rear wheel 12 is spinning, the braking distance is minimized by continuously activating the brakes 16 without performing the spinning determination.

Since the brakes 16 are actuated hydraulically, an electric current only needs to be supplied to the electromagnetic valves 33 b in order to actuate the brakes 16 . Since the forklift 10 is driven by the electric current from the battery, the power consumption is advantageously minimized. This embodiment is therefore preferable for reducing the power consumption, in which the front wheels 11 L, 11 R are braked by the hydraulic brakes 16 .

The brake pressure data M2 previously stored in the memory of the control device 44 allow easy and reliable control of the auxiliary brake pressure PK in accordance with the vehicle deceleration β.

The auxiliary brake pressure PK is selected from several stages. Compared to the case where the auxiliary brake pressure PK is steady  control is at the current one Embodiment therefore simple.

The auxiliary brake pressure PK is in agreement with one changed only parameter, which is the vehicle deceleration β. Therefore the control is simple.

When the waiting period t has passed after the brakes 16 are activated with the reference brake pressure P2, the auxiliary brake pressure PK is controlled in accordance with the stable vehicle deceleration β. This prevents the auxiliary brake pressure PK from receiving an inappropriate value immediately after the brakes 16 are activated due to unstable values of the vehicle deceleration β.

When the vehicle speed V is smaller after the start of the regenerative operation, namely when a short braking distance is expected to be the low speed determination value Vd directly, without the front wheels 11L, 11R are braked, then the brakes 16 are not activated. This prevents unnecessary activation of the brakes 16 and protects the battery.

A fifth embodiment of the present invention will now be described with reference to FIG. 15. The fifth embodiment is a modification of the embodiment shown in FIGS. 13 and 14. As shown in FIG. 15, steps S26 to S30 in FIG. 14 are omitted and only steps S21 to S24, S31 up to S34. That is, in step S31, a braking operation is carried out by a predetermined single auxiliary brake pressure PK. The auxiliary brake pressure PK is not changed according to the vehicle deceleration β.

The exemplary embodiments according to FIGS. 13 to 15 can be modified as follows.

If the accelerator lever 23 is moved to the neutral position while the forklift 10 is traveling, then the anti-skid procedure and the brake control procedure can be performed. Namely, at step S32 shown in FIG. 14 or 15, it is not necessary to consider whether the accelerating lever 23 is moved to the neutral position to determine whether the braking operation needs to be ended.

The auxiliary brake pressure PK can be calculated in accordance with the difference between the vehicle deceleration β and a predetermined target value. In this case, the load weight on the fork 17 a can be detected, and the target value can be set in accordance with the load weight.

The condition to start the anti-skid procedure can be different than the condition to start the Brake control procedure. For example, the Spin determination value, which is the reference value for starting the brake control procedure is smaller than that Spin determination value Va, which is the reference value at Start the anti-skid procedure.

The braking force of the brakes 16 can be adjusted by a method other than changing the auxiliary brake pressure PK. For example, the activation and deactivation of the brakes 16 can be repeated at short intervals, and the activation ratio in each cycle can be changed to control the braking force.

The second exemplary embodiment according to FIG. 9 can be combined with the exemplary embodiments according to FIGS . 13 to 15 18531 00070 552 001000280000000200012000285911842000040 0002010133228 00004 18412. That is, when the skid prevention procedure based on the permission determination value Vb is prohibited, the brake control procedure shown in FIGS. 13 to 15 can be prohibited.

The exemplary embodiment according to FIGS. 10 to 12 can be combined with the exemplary embodiments according to FIGS. 13 to 15. Namely, the forklift can, in the embodiments according to FIGS. 13 to 15 of the through rotation determination value in accordance with the acceleration or deceleration to be changed 10th

A fourth embodiment of the present invention will now be described with reference to FIG. 16. The differences from the first embodiment according to FIGS. 1 to 8 (c) and from the fifth embodiment according to FIG. 15 are mainly described below. As in the first embodiment shown in FIGS. 1 to 8 (c), the spin prevention procedure for the rear wheel 12 and the brake control procedure for the front wheels 11 L, 11 R are performed when the spin of the rear wheel 12 is detected during the regenerative operation. Furthermore, in the embodiment shown in FIGS. 16 (a) to 16 (c), the brake control procedure for the front wheels 11 L, 11 R is carried out when the spinning of the rear wheel 12 is not detected during the regenerative operation, for example due to a malfunction can be.

As described in the first embodiment shown in FIGS. 1 to 8 (c), the spin value ΔVD, which is used to determine whether the rear wheel 12 is spinning, is represented by the difference between the rear wheel moving speed VD and the converted moving speed VDP. The converted moving speed VDP is calculated based on the front wheel speeds NLF, NRF, which are detected by the front wheel speed sensors 45 L, 45 R. Therefore, if at least one of the front wheel speed sensors 45 L or 45 R malfunctions, the spin value ΔVD cannot be obtained and it cannot be determined whether the rear wheel 12 is spinning.

Fig. 16 shows a drive control routine of the forklift 10th The routine of FIGS. 16 (a) to 16 (c) is executed at predetermined intervals while the forklift 10 is moving.

At a step S41, the controller 44 determines whether both front wheel speed sensors 45 L, 45 R are normal. That is, the controller 44 determines whether it receives pulse signals from the front wheel speed sensors 45 L, 45 R that represent the front wheel speeds NLF and NRF, respectively. If the result is positive, if the front wheel speed sensors 45 L, 45 R are normal, then the control device 44 proceeds to step S42.

Steps S42 to S50 relate to a target engine torque setting procedure and the spin prevention procedure described in the first embodiment shown in FIGS . 1 to 8 (c). Therefore, if necessary, reference should be made to the description of the first exemplary embodiment according to FIGS. 1 to 8 (c).

At step S42, the controller 44 calculates the front wheel moving speed VF based on the front wheel speeds NLF, NRF. The front wheel speed VF represents the moving speed of one of the front wheels 11 L, 11 R, which is located radially on the outside during cornering.

At step S43, the controller 44 calculates the rear wheel speed ND based on the engine speed NM, which is detected by the rear wheel speed sensors 41 a, 41 b. The controller 44 also calculates the rear wheel moving speed VD based on the rear wheel speed ND. At step S44, the controller 44 calculates a converted moving speed VDP based on the front wheel moving speed VF. At step S45, the controller 44 calculates the spin value ΔVD by subtracting the converted moving speed VDP from the rear wheel moving speed VD.

At step S46, the controller 44 calculates a target torque of the drive motor 19 based on the engine speed NM and the lever operation amount ACC by referring to the map M1 shown in FIG. 4. When the drive motor 19 is controlled in the drive mode, the target drive torque is calculated. If the drive motor 19 is controlled in the regenerative mode of operation, then the target braking torque is calculated.

At step S47, the controller 44 determines whether the absolute value of the spin value ΔVD exceeds the determination value Va. If the absolute value of the spin value ΔVD is equal to or less than the determination value, then the controller 44 determines that the rear wheel 12 is not spinning and proceeds to step S48. In step S48, the controller 44 controls the drive motor 19 according to the normal target torque calculated in step S46.

If the absolute value of the spin value ΔVD exceeds the determination value Va, then the controller 44 determines that the rear wheel 12 is spinning and proceeds to step S49. In step S49, the controller 44 reduces the normal target torque calculated in step S46 by a predetermined rate, and sets the result as a new target torque to prevent skidding. Thereafter, the control device 44 proceeds to step S50. In step S50, the control device 44 controls the drive motor 19 according to the reduced target torque.

At step S51 following step S48, controller 44 stops brakes 16 and temporarily suspends the current routine. That is, when it is determined that the rear wheel 12 is not spinning, the front wheels 11 L, 11 R are not braked.

At a step S52 following the step S50, the controller 44 determines whether the vehicle speed V is equal to or less than the predetermined stop determination value Vc. The vehicle speed V is represented, for example, by the average of the front wheel moving speeds VLF, VRF. As described in step S33 in the flow chart shown in FIG. 14, the stop determination value Vc is a value of the vehicle speed V at which the forklift 10 substantially stops. If the vehicle speed V is equal to or less than the stop determination value Vc, the controller 44 executes step S51 and temporarily suspends the current routine.

If the vehicle speed V is larger than the stop determination value Vc, the controller 44 proceeds to step S53 and determines whether the drive motor 19 is controlled in the regenerative mode. That is, the controller 44 determines whether the current direction of movement of the forklift 10 is opposite to the direction indicated by the accelerating lever 23 .

If the drive motor 19 is not operated in the regenerative mode, namely when the drive motor 19 is operated in the drive mode, then the controller 44 proceeds to step S51 and temporarily suspends the current routine. If the drive motor 19 is operated in the regenerative mode, the controller 44 proceeds to step S54. At step S54, controller 44 activates brakes 16 and temporarily suspends the current routine. That is, when it is determined that the rear wheel 12 is spinning during the regenerative operation, the spinning prevention procedure for the rear wheel 12 and the brake control procedure for the front wheels 11 L, 11 R are carried out.

If the result at step S41 is negative, namely if at least one of the front wheel speed sensors 45 F, 45 R malfunctions, then the control device 44 proceeds to step S55. At step S55, the controller 44 calculates the target torque of the drive motor 19 based on the engine speed NM and the lever operation amount ACC by referring to the map M1 shown in FIG. 4, as in the step S46. In step S56, the controller 44 controls the drive motor 19 according to the normal target torque calculated in step S55.

After step S56, the controller 44 proceeds to step S53. As described above, at step S53, the controller 44 determines whether the drive motor 19 is operated in the regenerative mode. If the drive motor 19 is operated in the regenerative mode, the controller 44 proceeds to step S54 and activates the brakes 16 .

As described above, if it is determined that at least one of the front wheel speed sensors 45 L, 45 R is malfunctioning, if the rear wheel 12 cannot be detected, the anti-skid procedure is not performed, and the drive motor 19 is performed accordingly controlled the normal target torque. If the drive motor 19 is controlled in the regenerative mode of operation, the front wheels 11 L, 11 R are braked by the brakes 16 . Namely, if the rear wheel 12 cannot be spun in the regenerative mode, the front wheels 11 L, 11 R are braked regardless of whether the rear wheel 12 spins.

The drive motor 19 , which is an AC induction motor, is operated by adjusting the size and frequency of a three-phase AC current supplied to the drive motor 19 according to signals from the rear wheel speed sensors 41 a, 41 b. Thus, the drive motor 19 can be controlled even if the front wheel speed sensors 45 L, 45 R malfunction. However, if the rear wheel speed sensors 41 A, 41 B malfunction, the drive motor 19 cannot be controlled.

As described above, if the spinning of the rear wheel 12 cannot be detected during the regenerative operation, the front wheels 11 L, 11 R are braked regardless of whether the rear wheel 12 spins. If the front wheel speed sensors 45 L, 45 R have a malfunction, or therefore, if lines of the sensors 45 L, 45 R are interrupted, then the front wheels 11L, 11R are braked, in order to minimize the stopping distance of the forklift 10 degrees.

If only one of the front wheel speed sensors 45 L, 45 R malfunctions, then the spin value ΔVD can be calculated based on the front wheel speed detected by the normal sensor 45 L, 45 R, and the spin prevention procedure can be performed using the calculated spin value ΔVD be carried out.

The front wheels 11 L, 11 R are braked not only when the front wheel speed sensors 45 L, 45 R malfunction, but also when the spin value ΔVD cannot be calculated due to a malfunction of the rear wheel sensors 41 a, 41 b. In this case, the drive motor 19 can be replaced by a DC motor, which can be controlled even if the rear wheel speed sensors 41 a, 41 b malfunction.

A brake pedal 100 (see FIG. 3) may be disposed on the bottom of the stand 20 , and when the brake pedal 100 is depressed to brake the rear wheel 12 , the spinning of the rear wheel 12 can be detected. If it is determined that the rear wheel 12 is spinning, then the front wheels 11 L, 11 R are braked by the brakes 16 . If the spinning of the rear wheel 12 cannot be detected, then the braking control procedure of the front wheels 11 L, 11 R can be carried out by the brakes 16 .

The braking process of the front wheels 11 L, 11 R can be carried out according to one of the methods described in the exemplary embodiments according to FIGS. 13 to 15.

The exemplary embodiments according to FIGS. 1 to 16 can be modified as follows.

In the illustrated embodiment, the spin value ΔVD represents the difference between the moving speed VD and the converted moving speed VDP. However, the spin value ΔVD can represent a spin ratio. In this case, the spin value ΔVD is calculated based on the following equations. The above equation is used during drive mode or when accelerating the forklift 10 . The lower equation is used during regenerative operation or when decelerating the forklift 10 . The determination value Va is determined according to the spin ratio.

ΔVD = (VD - VDP) / VD

ΔVD = (VDP - VD) / VDP

If the absolute value of the rotational speed of the rear wheel 12 or the absolute value of the speed of movement of the rear wheel 12 exceeds a predetermined determination value, then it can be determined that the rear wheel 12 is spinning.

The regenerative mode of operation can be started by actuating an actuating element other than the accelerating lever 23 . For example, a pedal can be used.

In the illustrated embodiments, the rear wheel 12 is electrically braked during the regenerative mode of operation. However, the rear wheel 12 can be braked electrically by countercurrent braking. Namely, any braking method can be applied as long as the motor 19 is electrically controlled so as to generate a braking torque.

The drive motor 19 does not have to be an AC motor, but it can be a DC motor.

The brakes 16 need not be hydraulic drum brakes, but can be hydraulic disc brakes. In addition, the brakes 16 need not be hydraulically controlled, but can be driven by electrical actuators.

The front wheels 11 L, 11 R do not always have to be trailing wheels. For example, the front wheels 11 L, 11 R can be driven or braked by motors as the rear wheel 12 spins as needed.

The present invention can be applied to operating vehicles other than the reach truck 10 . The present invention can be applied to commercial vehicles in which the front wheels are driving wheels and the rear wheels are trailing wheels.

Hence the current examples and Embodiments an illustrative and none have a restrictive character, and the invention is not based on the details given herein are limited, but can within the scope and equivalents of the attached Claims are modified.

A reach truck has a rear wheel that is a drive wheel and front wheels that are trailing wheels. The rear wheel will powered by a motor. A controller calculates a target torque of the motor according to the actuation variable an accelerator lever and controls the engine such that the motor generates the calculated target torque. The Controller calculates a spin value that is the Represents the degree of spin of the rear wheel based the speed of the rear wheel and the speed of the front wheels. When the absolute value of the spin value is a predetermined one Spin determination value exceeds, then the Control device the target torque by a predetermined rate, to perform a spin prevention procedure. As a result, with a simple structure, the spinning of the rear wheel stopped reliably.

Claims (25)

1. A drive control device for an electric company vehicle having a drive wheel driven by a motor, the device comprising:
an actuator that is operable to adjust the torque of the engine;
a skid detection device for detecting a skid value representing the skid degree of the drive wheel; and
means for controlling the engine, the engine control means calculating a target torque of the engine according to the operation amount of the actuator and controlling the engine so that the engine generates the target torque, and the apparatus is characterized in that the engine control means reduces the target torque by a predetermined rate to execute a skid prevention procedure when the absolute value of the skid value exceeds a predetermined skid determination value. 2. Device according to claim 1, characterized in that  the engine control device drives the engine in a Operating mode or in a braking mode in response to actuates an actuation of the actuating element, the Motor control device the motor to generate a Driving torque controls to a driving force on the Drive wheel when the motor is in the drive Operating mode is operated, and the Motor control device the motor for generating a braking torque controls to apply braking force to the drive wheel when the motor is operated in the braking mode. 3. Device according to claim 1 or 2, characterized in that the spin determination value is set to be corresponds to a range of the spin value in which the Friction between the drive wheel and the road surface is relatively large. 4. Device according to one of claims 1 to 3, characterized in that the engine control device assumes the skid determination value low vehicle speed smaller than at high Vehicle speed. 5. Device according to one of claims 1 to 4, characterized in that the engine controller the rate by which the target torque is reduced so that the absolute value of the Spin value around the spin determination value fluctuates four times or more per second. 6. Device according to one of claims 1 to 5 characterized in that the operating vehicle has a towing wheel, the Spin detection device the speed of movement of the drive wheel relative to the road surface on the  Based on the speed of the drive wheel, and where it is calculated the speed of movement of the towing wheel relative to that Road surface based on the speed of the Trailed wheel, and being the Spin detection device the spin value on the Basis of the drive wheel movement speed and the Tractor wheel movement speed calculated. 7. The device according to claim 6, wherein the rotation detection device the Speed of movement of the drive wheel relative to that Road surface based on the Tractor wheel movement speed estimates and the estimated Speed of movement as a converted Movement speed determines, and the Spin detection device calculates a value with the difference between the drive wheel moving speed and the converted movement speed in one Interrelation, and the calculated value as the Defines the spin value. 8. Device according to one of claims 1 to 7, marked by an approval body that carries out an execution of the Anti-skid procedure by the Motor control device only allows if the Operating state of the vehicle a predetermined Admission requirement met. 9. The device according to claim 8, characterized in that the approval body the execution of the Anti-skid procedure by the Engine control device only allows in a period that then starts when the absolute value of the spin value one predetermined admission determination value that  is greater than the spin determination value, and then ends when the vehicle speed drops to one Hold determination value decreased, which is approximately zero. 10. The device according to claim 8, characterized in that the approval body the execution of the Anti-skid procedure by the Engine control device prevents when the absolute value of the Vehicle acceleration a predetermined Acceleration determination value exceeds. 11. The device according to one of claims 1 to 9, characterized in that the engine control device determines the skid determination value changes according to the absolute value of vehicle acceleration. 12. The device according to claim 11, characterized in that the engine control device assumes the skid determination value a large absolute value of vehicle acceleration greater than with a small absolute value of the vehicle acceleration sets. 13. The apparatus according to claim 2, characterized by
a brake for braking a trailing wheel located on the vehicle; and
a brake control device, the brake control device actuating the brake when the anti-skid procedure is executed in the braking mode. 14. The device according to one of claims 1 to 12, wherein the vehicle has an additional wheel, and the device is characterized by
a brake for braking the additional wheel;
a brake control device, the brake control device actuating the brake when the anti-skid procedure is carried out due to a braking operation of the drive wheel. 15. The apparatus according to claim 14, characterized in that the brake is a friction brake. 16. The apparatus according to claim 14 or 15, characterized in that the brake control device on the additional wheel through the Brake applied braking force according to the Vehicle deceleration changes. 17. The apparatus according to claim 16, characterized in that the brake control device increases the braking force of the brake, when the vehicle deceleration decreases. 18. The apparatus according to claim 16 or 17, characterized in that the brake control device gradually increases the braking force of the brake changes. 19. The device according to claim 18, characterized in that the brake control device of each of the various stages of the Braking force a predetermined range of vehicle deceleration assigns, and wherein the brake control device, the braking force the brake adjusts so that the vehicle deceleration is within a range that corresponds to the braking force. 20. Device according to one of claims 16 to 19, characterized in that  the brake control device from an operation of the brake until a predetermined period elapses, the braking force the brake to a predetermined reference value regardless of Changes in vehicle deceleration are maintained. 21. Device according to one of claims 14 to 20, characterized in that the brake control device actuates the brake prevents if the vehicle speed when starting the Braking of the drive wheel is less than one predetermined low speed determination value. 22. The device according to one of claims 14 to 21, characterized in that after the brake has been applied once, the Brake control device continues to apply the brake until the vehicle speed to a predetermined Hold determination value decreased, which is approximately zero. 23. The device according to claim 13, characterized in that the brake control device actuates the brake when the brake Operating mode is then carried out when the Spin detection means not the spin value can capture. 24. The device according to claim 23, characterized in that the rotation detection device has a first sensor for Detect the speed of the drive wheel and a second sensor for detecting the speed of the towing wheel, and wherein the Spin detection device the spin value on the Basis of the speed of the drive wheel and the speed of the Tractor wheel calculated. 25. The device according to one of claims 14 to 22,  characterized in that the brake control device operates the brake when that Drive wheel is braked when the Spin detection means not the spin value can capture.